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Vegetable Related Hort-Bytes

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corn thumbArticles are being published every day with information that can be used by Saskatchewan producers. The Hort-Bytes are a collection summaries of some of the most relevant articles recently published.

 

The article summaries are divided into sections based on content:

Within each section article summaries are organized alphabetically by title. Full citations are provided with each summary to allow for easy retrieval of orginal articles.

Click on the title to read the article summary:


Avoid Moisture Stress to Maximize Muskmelon Yields and Quality

Although it is widely believed that a little water stress helps give melons the best flavor, research out of Australia suggests the opposite - that late season water stress not only reduces melon yields but it may also impair fruit quality. The extend of the yield and quality loss appear to be proportional to the duration and severity of the moisture stress event. Stress at 7 days prior to harvest was more harmful than stress closer to harvest time. The researchers cautions that; while adequate moisture is clearly beneficial; excess moisture late in the season can lead to problems with fruit splitting and decay. Drip irrigation systems may be particularly useful in situations where it is important to keep the plants well supplied with moisture - but where contact between the fruit and moist soil needs to be avoided.

Source : Long, Walsh and Midmore (2006). HortScience 41:367-369.


Banding Cuts Herbicide Costs

Growers can control weeds in their potato crops by applying herbicides, via tillage or a combination of the two practices. As herbicides are costly, growers are looking at options to reduce herbicide use without compromising on weed control. Ivany (Can. J. Plant Sci. 2002) showed that reducing herbicide application (metribuzin preplant + clethodim post-emergence) to a 1ft wide band applied directly over the row provided excellent weed control (better than 90%) when combined with a single post-emergence tillage operation to take out the unsprayed weeds growing between the rows. The timing of the tillage step (crop at ground crack, 3" or 6" tall) had no impact on weed control. By comparison, a single tillage operation provided only 30-40% weed control. The weeds growing in the hills reduced yields in the tillage-only treatments by over 30%. By contrast, the combination of band applied herbicide+a single tillage produced yields equivalent to when the entire field was treated with herbicide, but at a cost savings of 66%. The relative efficacy of band application + tillage will vary with weed type and cropping conditions but the idea is worth thinking about for next spring.

Source: Ivany (2002) Can. J. Plant Sci.


Better Methods to Meet Crop Water Needs on Sandy Soils

The limited water holding capacity of sandy soils (4-8% by volume) represents a management challenge in vegetable production - especially when growers are attempting to produce shallowed rooted crops like onions or crops with high rates of moisture use like tomatoes. The standard approach to managing these crops on sandy soil is to irrigated heavily and frequently - resulting in poor water use efficiency and the leaching of valuable soil nutrients. As supplies of water become more limited and the environmental impact of nutrient leaching becomes a greater concern options for better managing the moisture requirements of vegetable crops on sandy soils are needed. Drip irrigation systems coupled with soil moisture monitoring systems may represent the answer as they allow for application of small amounts of water (no nutrient leaching) whenever required by the crop. In a trial with onions in Oregon, Shock et al (2005) showed that a drip system calibrated to deliver ½” of water in a single irrigation event each day produced higher yields and better onion quality than systems calibrated to deliver water either more or less frequently. Munoz-Carpena et al (2005) showed that a drip system coupled to tensiometers could be used to begin irrigating a tomato crop whenever soil moisture levels dropped below a threshold amount (-15kPa). This system applied small amounts of water up to 5 times each day. The frequency of irrigation had no impact on yields but total water use with this system was substantially reduced relative to crops irrigated using other control systems.

Sources: Shock, Feibert and Saunders (2005). HortTech 15: 652-659
Munoz- Caprpena, Dukes, Li and Klassen (2005). HortTech 15: 584-590.


Crowding Better Idea than Pruning Peppers in High Tunnels

There is growing interest in the potential to use high tunnels for the production of warm season vegetable crops such as peppers in Saskatchewan. Given the limited growing area available within the tunnels, growers must utilize production practices that maximize productivity and returns/unit area. The greenhouse industry faces the same challenge and some of the tricks used by greenhouse growers may be of use in high tunnels. For example - greenhouse peppers are typically pruned and trained to grow vertically to increase yields within a limited growing space. In the standard “V” training system, the pepper plant is pruned to form a 2-stemmed plant, with the two shoots that form the V being held apart and supported vertically by twine wrapped around the stems. While this approach has been proven to increase yields over the 6-9 month lifespan of a typical crop of greenhouse peppers, it may not be as effective or necessary when the harvest season is more limited - as in high tunnel production of peppers in SK. Jovicich, Cantliffe and Stoffella have recently compared the standard “V” training system versus a “Spanish” system in unheated low tech greenhouses in Florida. In the “Spanish” system, the plants are staked upright but are not pruned - resulting in bushy plants with 2-4 main stems. Over a 3 month harvest period, they found no yield difference between the two training systems. However, the “Spanish” system produced more “bonus” large-sized fruit and had significantly less grade out due to blossom end rot than the “V” system. Most importantly, the labor involved in training the plants using the “V” system was 75% greater than the labor required in the “Spanish” system. They conclude that the effort involved in the “V” training system could not be justified in situations where the lifespan of the pepper crop is relatively short. Instead, putting lots of plants into the production area was the key to maximizing yields when the growing/harvesting season was limited. When they compared spacings of 50, 25 or 20 cm between plants (with 1.3 m between rows) they found that the closest spacing resulted in the highest yields and also had the fewest problems with fruit quality. University of Saskatchewan trials have come to similar conclusions for peppers and melons growing in high tunnels. However, wider spacings were required for optimum yields of mature fruit in a high tunnel tomato crop.

Source : HortTechnology (2004) p. 507-513.


Earthway Seeders - A Review

The Earthway Seeder is a common sight in home gardens, small scale commercial farms and in research plots. These lightweight, inexpensive planters are sold with six different vertical metering plates that allow the unit to be used to seed a range of vegetable crops. A lack of precision is a major concern with all vegetable seeders. Inaccurate seed spacings can arise due to problems with both the seed singulation and metering system and the distribution and coverage system. When Parish and Bracy evaluated the performance of commercial vegetable planters (Stanhay and Gasparo) they found that even the best units were less precise than desired, particularly with irregularly shaped seed like carrot and spinach. In a similar series of tests using the Earthway planter, they found that its precision was far inferior to the commercial units. However, they felt that the Earthway still did an acceptable job and at 1/10 the price of the commercial planters. They noted that for many crops, the recommended seeding plates for the Earthway dropped more seed than was required. They recommended that for beets, broccoli, carrot and corn a portion of the holes in the seeding disks should be blocked with tape. We however found that taping the holes shut tended to allow small seeds like broccoli to slip between the plate and the body of the planter - at which point the seed was often crushed. An alternative solution to the problem of over-seeding is to dilute the seed of the vegetable crop with dead seed from a low cost, comparable-sized alternative crop. We use heat-killed canola seed to dilute seed of cabbage and broccoli, while spice crops like dill or caraway can be used to dilute carrot and beet seed.

Source : Parish and Bracy (2004). HortTechnology 14: 257-261.


Economics of Potato Rotations

Determining the optimum crop rotation program involves consideration of economics as well as the sustainability and environmental impact of the rotation.  In an eight year study of potato rotations in Manitoba, Khakbuzan (et al. 2010) found that potatoes were far more profitable than any of the other crops used in the rotation (canola, cereals or forage crops) and therefore 2 year rotations (ex. potatoes/canola or potatoes/wheat) were more profitable than longer rotations.   A 2 year canola/potato rotation proved to be the most profitable despite the fact that in most years the canola crop actually returned net negative revenues due to low yields.  The reason this rotation was so highly profitable was that alternating potatoes with canola appeared to substantially increase potato yields.  The study did not explore why the potato/canola rotation was so much more favourable to the productivity of the potato crop relative to the canola crop.   While the shorter rotations did tend to maximize short-term economic gain the study noted that soil erosion and loss of soil organic matter was greater in the 2 year rotations than when potatoes were included less often in the rotation.  Eventually this degradation of the field conditions would lead to a decline in productivity for all crops in the rotation.       

Source : Khakbazan, Mohr, Volkmar, Tomasiewicz, Moulin, Derksen, Irvine, McLaren and Monreal (2010).  Amer. J. Potato Res. 87:446-457.


Factors Influencing Levels of Nutraceutical Agents in Vegetables

The health benefits of following a diet rich in vegetables have been well established. However, the factors that determine exactly how “healthy” any given vegetable will be have not been as well established. For example, the Vitamin A content of carrots can vary by 5X, depending on the cultivar, the production location and the year. G. Lester (HortScience 2006) has reviewed some of the factors that can influence the levels of several important nutritional agents (vitamins and antioxidants) in fruits and vegetables. Not surprisingly, which crop you chose to eat has the greatest impact on the levels and balance of nutrients consumed. The variety or cultivar of the crop is also important. Size matters - in general, as the size of the particular item increases, so do the levels of nutrients it contains. This likely reflects the tendency for nutrient levels to increase with maturity. Once the commodity reaches full size, nutrient levels plateau and may even begin to decline as the commodity matures past prime condition. Nutrient levels tend to be highest under growing conditions that match the needs of the plant for optimum growth. For cool season crops like lettuce, nutrient levels in the harvested crop are highest when the crop is grown under relatively cool conditions. Cool conditions close to harvest time are particularly beneficial. Warmer season crops like tomato show the same trend, except at higher temperatures. In general, the more light the crop receives, the higher the concentration of nutrients found in the crop. This relationship, however can be complicated as high light levels may also lead to high temperatures and rapid growth - factors that can actually reduce nutrient concentrations in the crop. Low light levels coupled with high temperatures may explain why greenhouse-grown vegetables tend to have lower nutrient levels than field-grown crops. Crops grown on clay soils tend to have a higher nutrient content than crops from sandy soils. This reflects the greater fertility and nutrient holding capacity of the finer textured soils. Crops grown under irrigation or in areas with very abundant rainfall tend to have lower nutrient levels than crops from drier conditions. This may reflect dilution of the nutrients by the more rapid growth triggered by abundant moisture. The relative nutritional value of crops grown utilizing “organic” methods versus standard methods is a matter of considerable debate - the results seem to vary with the crop, the cropping situation and the nutrient being evaluated.

Source : G. Lester (HortScience 41: 59-64)


Factors Influencing Quality Problems in Carrot

Consumers have limited tolerance for defects in the appearance of carrots - consequently growers must strive to employ crop management practices that maximize yields of marketable quality roots. Cultivar selection is a critical factor. Researchers in Nova Scotia showed that commercially available carrot cultivars vary widely in their ability to tolerate drought stress. Drought stress causes forked roots as well as other quality problems. The processing-type cultivars Bergen, Prodigy and Caropak were particularly tolerant of drought stress. Green shoulders (GS) and internal greening (IG) reduce both the visual quality and flavor of carrot. These disorders are caused by the accumulation of chlorophyl which occurs when the carrot crowns are exposed to light. Management practices that reduce exposure of the crowns to light will reduce both the incidence and severity of GS and IG. Select cultivars that produce a good stand with lush top growth. When growing carrots with small tops (ie Nantes-type) seed more densely than normal. Although light hilling once the carrot roots begin to bulk up may reduce the incidence of green shoulders it does not prevent internal greening. This suggests that internal greening occurs relatively early in development of the crop. Splitting is another common quality problem. Incidence of splitting increases as the clay content and nitrogen levels in the soil increase. Warm weather coming into harvest increased cracking whereas irrigation had little impact. Cultivar selection was again important in controlling cracking.

Sources :

  • Lada, Stiles and Pettipas (2004). HortScience 39: 855( Abstr).
  • Palanisamy, Lada, Kyei-Boahen, Stiles, Caldwell and Asiedu (2004). HortScience 39: 760 (Abstr).
  • Hartz, Johnston and Nunez (2004). HortScience 39: 852 (Abstr)

Freezing Cold is Best for Garlic

Although it is generally recommended that garlic be stored at 0oC , research by Volk et al suggests that -3oC is actually better for both soft and hard-neck types of garlic. Storage at -3oC resulted in superior flavor and color, slowed sprouting and reduced decay relative to storage at 0oC or warmer. Low temperature storage also improved the yield potential and quality when the garlic was planted out the next spring.

Source : Volk, Rotinoo and Lyons (2006). HortScience 39:571-573.


Heat Stress and Broccoli

Heat Stress and Broccoli Appearance of the head is a key quality indicator in broccoli. While excessive heat is not a common problem on the Canadian prairies, growers should nonetheless be aware of the potential impact of heat stress on their broccoli crops. Sensitivity to heat stress has a strong genetic component. Farnham and Bjorkman (2011) have recently shown that many of the most widely grown cultivars of broccoli (cv. Marathon, Greenbelt, Arcadia and Patron) were all more susceptible to heat stress than new lines bred specifically for enhanced heat tolerance. Under extremely hot conditions (avg. high > 30C, avg. low> 20C) these cultivars failed to form a marketable main head and instead produced a mass of lateral branches. Under less extreme conditions head quality was compromised by heat stress the heads became flattened, with a pale color and uneven bead size.

Source: Farnham and Bjorkman (2011). HortScience 46: 858-863.


Ideas for Maximizing Pepper Yields in High Tunnels

There is growing interest in the potential to use high tunnels for the production of warm season vegetable crops such as peppers in Saskatchewan. Given the limited growing area available within the tunnels, growers must utilize production practices that maximize productivity and returns/unit area. The greenhouse industry faces the same challenge and some of the tricks used by greenhouse growers may be of use in high tunnels. For example - greenhouse peppers are typically pruned and trained to grow vertically in order to increase yields within a limited growing space. In the standard “V” training system, the pepper plant is pruned to form a 2-stemmed plant, with the two shoots that form the V being held apart and supported vertically by twine wrapped around the stems. While this approach has been proven to increase yields over the 6-9 month lifespan of a typical crop of greenhouse peppers, it may not be as effective or necessary when the harvest season is more limited - as in high tunnel production of peppers in SK. . ..........., Cantliffe and Stoffella have recently compared the standard “V” training system versus a “Spanish” system in unheated low tech greenhouses in Florida. In the “Spanish” system, the plants are staked upright but are not pruned - resulting in bushy plants with 2-4 main stems. Over a 3 month harvest period, they found no yield difference between the two training systems. However, the “Spanish” system produced more “bonus” large-sized fruit and had significantly less grade out due to blossom end rot than the “V” system. Most importantly, the labor involved in training the plants using the “V” system was 75% greater than the labor required in the “Spanish” system. They conclude that the effort involved in the V training system could not be justified in situations where the lifespan of the pepper crop is relatively short. Instead, putting an adequate number of plants into the production area was the key to maximizing yields when the growing/harvesting season was limited. When they compared spacings of 50, 25 or 20 cm between plants (with 1.3 m between rows) they found that the closest spacing resulted in the highest yields and also had the fewest problems with fruit quality. University of Saskatchewan trials have come to similar conclusions for peppers and melons growing in high tunnels. However, wider spacings were required for optimum yields of tomatoes.


Is Food Grown Today as Tasty and Nutritious as in the "Good Old Days"?

A growing body of evidence suggests that the concentration of certain minerals important in human nutrition (especially calcium and copper) as well as some vitamins and proteins is lower in fruit and vegetable today than they were in the past. Research suggests that this decline in quality can be largely attributed to a "dilution effect" related to a focus on yields rather than nutritional quality (or flavor), both in plant breeding programs and in agronomy research. To assess the impact of breeding/selection practices on nutrient quality researchers have grown older low yielding cultivars of various crops alongside modern high yielding cultivars in side by side trials using identical production practices under the same environmental conditions. Although there was significant year to year and site to site variability in nutrient levels, there was also a fairly consistent trend in the findings - beneficial mineral nutrients like magnesium and iron were found in higher concentrations in the older low yielding cultivars than in the modern cultivars. This "genetic dilution effect" could be attributed to selection for fast growing, fast maturing genotypes that had a larger average cell size that rendered the harvested portion of the plant large, juicy and tender. It appears that this combination of traits has been considered more important in recent breeding programs than issues like mineral content. Davis (2009) notes that the rate of decline in nutrient levels over the past 40 years has been greater in vegetable crops than in fruit. Over the same time period, the rate of improved of yields in new vegetable varieties was double the rate of improvement achieved in fruit crops - another line of evidence suggesting that selection practices have contributed to the observed decline in the nutritional quality of fruit and vegetables. In trials conduced with varying levels of production inputs like fertilizers, irrigation or pest control, a similar dilution effect was observed - high input production practices that led to rapid crop growth and high yields also resulted in production of commodities containing reduced concentrations of various minerals and other potential beneficial nutrients. Given these two types of dilution, its is perhaps not surprising that organically grown produce tends to have higher levels of various minerals and other nutrients - as organic production systems are typically based on growing older, open-pollinated cultivars using reduced inputs. The result is a slower growing and potential lower yielding crop, but the resulting fruit and vegetables may contain higher levels of beneficial nutrients or other complex phytochemicals, including the compounds that give the crop its flavor.

Source : Crop Yield and Quality: Can We Maximize Both? A Colloquium presented at the ASHS Conference (2007). HortScience 44: 5-22. (2009).


Low Temperature Performance of Sweet Corn Cultivars

Supersweet (sh2) and sugar enhanced (se) types of sweet corn have become increasingly popular as they are sweeter and have superior storage potential relative to the standard sweet (su) types. However, the high sugar content in the seed of the sh2 and se types may adversely affect their germination and emergence, particularly in cool, wet soils. Researchers at Clemson University have recently compared the germination characteristics of a range of su, se and sh2 varieties over soil temperatures ranging from 11-30 oC. In general, the standard su types germinated 1-2 days earlier than the se and sh2 types, particularly at the lower soil temperatures. Similarly, the lowest soil temperature to produce maximum germination was several degrees cooler for the su types than the higher sugar types. However, the most vigorous se and sh2 varieties performed as well at low temperatures as the best su types. Varieties which performed well at low soil temperatures, often did relatively poorly at higher temperatures and visa-versa. It appears that each corn variety has a characteristic optimum set of germination conditions. Ideally growers will time planting to coincide with these conditions. This study shows that generalizations about differences in germination potential between the various types of sweet corn are not really valid, at least at soil temperatures above 11 oC. It would be interesting to test the se and sh2 types at the lower soil temperatures commonly encountered by Saskatchewan growers of sweet corn.

Source : Hassel, Dufault and Phillips (2003). Low-temperature germination response of se, se and sh2 sweet corn cultivars. HortTechnology 13: 136-141.


Mother Stalk Method of Asparagus Culture

Asparagus is traditionally harvested using the "clear cut" method - for a few weeks each spring all spears are harvested as they emerge. The harvest continues until food reserves stored in the root system become exhausted - at that point spear diameter begins to decline. If harvest continues beyond this point, the long term vigor of the crop is compromised. The traditional clear cut harvest method results in a glut of asparagus early in the season which can exert downward pressure on prices. An alternative approach to harvesting asparagus is the "Mother Stalk Method". This method is widely employed in Asia to shift the asparagus harvest season. In the Mother Stalk Method, the first 3-5 spears to emerge in the spring are allow to grow into full size ferns. These ferns then begin to supply the root system with the food reserves required to safeguard the long term health of the crop. All subsequent spears are harvested - shifting the traditional spring harvest period into summer and beyond. Research (Dufault and Ward 2005; Orton et al 2008) suggests that the Mother Stalk Method produces yields that are comparable or even superior to the traditional clear cut method. However the Mother Stalk Method of culture also requires substantially more labor, as harvesting spears from within a developed canopy is difficult If the resulting off-season harvest commands a premium price the additional harvest effort may be worthwhile.

Source : Dufault and Ward (2005). HortScience 40: 1327-1332. Orton, Garrison and Garrison (2008). HortSciennce 43: 595.


Management Factors Influencing Nutritional Quality of Vegetable Crops

With the constant stream of media reports regarding the role of vitamins and other nutrients in a healthy diet, consumers are looking for vegetables that pack the maximum nutritional value. Different cultivars of crops like broccoli and spinach show a huge range in their nutrient content. Improved nutrient content has emerged as one of the prime objectives of many vegetable crop breeding programs. Breeders in Texas have developed purple and yellow fleshed potatoes with 30 times the antioxidant value of normal white fleshed varieties. The new seedless types of watermelon tend to have redder flesh and a higher lycopene content that traditional types. Lycopene is another important anti-oxidant. Some of the management practices employed by growers can also have a significant impact on the nutritional value of their product. Fall planted spinach has higher levels of beneficial anti-oxidants and vitamins than a spring planted crop ... but the fall seeded crops also tends to have higher leaf nitrate levels which can be detrimental to the consumer. Low light levels due to cloudy weather or shading by weeds increases the water content of leafy greens while reducing their Vitamin C content.


Sources :

  • Marus and Lester (2004). HortScience 39:771 (Abstr).
  • Morelock, Howard and Murphy (2004). HortScience 39: 766 (Abstr).
  • Perkins-Veazie, Collins and Roberts (2004). HortScience 39:830 (Abstr).
  • Reddivari, Hale, Scheuring and Creighton Miller (2004) 39: 812 (Abstr).

Potato Flavour

While almost everybody enjoys the flavour of potatoes there is still room for improvement, especially if potatoes are to maintain their popularity in an increasingly diverse marketplace.   However, efforts to improve the flavour of potatoes are complicated by the fact that the flavour of potatoes is complex and there is little agreement as to exactly what makes for a “good” tasting potato.  The flavour of potatoes is influenced by genetics, production and storage practices as well as cooking methods.    While an “acceptable” flavour is required of any newly developed potato cultivar, the focus of most modern breeding programs has been on superior yields and processing characteristics.   Breeding to enhance flavour should be possible as there is considerable variability in the flavour within the popular commercialized varieties as well as in less developed Andean land races of potato.   Growing conditions and production practices can have subtle effects on potato flavour.   Stressful growing conditions (heat, drought etc) can lead to the accumulation of bitter glycoalkaloids.  Sulfur containing compounds typically have strong flavours, therefore soil sulphur levels may influence the flavour profile.  Similarly high soil potassium levels are thought to enhance potato flavour.  Certain microbes present in the soil may also contribute to the “earthy” flavour tones characteristics of potatoes.  Cooking causes very significant changes in potato flavour, with each cooking method yielding a different flavour profile.   In general, microwaving is considered to produce a less favourable flavour profile than baking or boiling.   In processed potatoes (chips and fries) the oil type used has relatively little impact on development of potato flavours but can contribute undesirable flavour notes such as rancidity.   While the flavour of processed potatoes deteriorates quite quickly during storage, there are few consistent changes in the flavour of boiled or baked potatoes as a function of time in storage.   

Source: Jansky (2010).  Amer. J. Potato Res. 87: 209-217.


Pre-Harvest Water Stress Improves Processing Quality and Flavor of Tomato

Reducing irrigation in the last 2-3 weeks prior to harvest resulted in higher soluble solid and Brix content of tomatoes when compared to a crop that was kept well-irrigated throughout the season. Both of these changes make the fruit easier to process and are associated with superior flavor. Although this late season water stress treatment did result in a small reduction in fruit yields, this loss was more than offset by the observed improvements in fruit quality. Earlier or more prolonged periods of stress resulted in unacceptable large reductions in fruit yield.

Source : Hatz, Johnstone, LeStrange, Nunez and Miyao (2004). HortScience 39:763. (Abstr)


One More Thing to Worry About

Researchers evaluating 30 years of yield and quality data for vegetable crops in Ontario confirm what many Saskatchewan growers have learned by hard experience in 2003 - hot dry weather is tough on many of our favorite vegetables. The researchers found that both the yields and quality of crops like potato, cabbage and rutabagas declined as the average growing season temperature increased - and were particularly hard hit by increasing numbers of “hot” (> 30C) days. Although these cool season crops have traditionally done well on the Prairies, global climate change models all indicate that the Prairies are seeing a general increase in summer temperatures coupled with a decline in precipitation. Although yields of cool season vegetables were not directly linked to overall growing season precipitation in the Ontario study, they did increase with the number of rainy days. This may support the old adage - that although irrigation is fine ... there is nothing like a rain to get the crops growing. The global climate models also predict warmer shorter winters on the Prairies - which would be great except that the overwintering stages of insect pests like Colorado potato beetle, grasshoppers and root maggots also enjoy warmer weather. The news however, is not all bad - more warm, dry days can be expected to increase local yields of heat-adapted crops such as tomatoes, particularly if growers adopt moisture-conserving production practices like mulches and drip irrigation. The researchers also found that year to year variations in the yields of crops like onion, carrot and radish could not be blamed on any specific climate factor. These crops may still represent reliable cropping options in the face of increasingly variable climate conditions.

Source: McKeown, Warland and McDonald (2003). Cool season vegetable crop yield prediction trends in Ontario: A possible signal for global warming?. The Grower. pp 17.


Prevention and Management of Diseases on Vegetable Transplants

The warm temperatures, high humidities and crowded conditions typically employed in greenhouse production of vegetable transplants are ideal for the development and spread of a range of diseases. Fungal diseases such as damping off (Rhizoctonia and Pythium) and bacterial diseases such as black rot (Xanthamonas campestris) have the potential to kill seedlings in the greenhouse and continue to cause damage once the seedlings are transplanted in the field. The best way to prevent problems with disease during transplant production is to plant disease-free seed into a clean greenhouse. Keep seedlings with common disease problems isolated from one another in the greenhouse. Plants weakened by a lack of light or nutrient, moisture or temperature stress are more susceptible to disease. Growers should avoid irrigation practices which lead to extended periods of leaf wettness or saturation of the growth media. Early detection of any problems is critical, as greenhouse diseases spread rapidly. Infected plants should be immediately removed from the greenhouse and adjacent flats should be quarantined. Unfortunately, there are relative few disease control products registered for greenhouse use and most are only effective if applied prior to arrival of the disease. Greenhouse pests such as fungus gnats attracted by the odor produced by decaying, diseased seedlings can spread the disease to adjacent healthy plants. Growers planning to purchase transplants from a custom grower should clearly specify their management and quality expectations ahead of time and then take the time to inspect the greenhouse prior to and during the seedling production period.

Source : Greathead (2003). Prevention and management of diseases in transplanted vegetables. HortTechnology 13: 55-58.


Progress on Extending the Shelf Life of Melons and Beans

As melon fruit begin to ripen they produce large amounts of ethylene gas - and this gas in turn triggers a number of additional ripening reactions including fruit softening and weakening of the connection between the fruit and the rest of the plant. Although some of these ethylene responses are beneficial, they also ultimately lead the fruit to lose quality and become over mature. Unfortunately, the orange fleshed cantaloupes that do well in the short growing season available in Saskatchewan also produce more ethylene than do the green fleshed honeydews - which may explain why locally grown cantaloupes also seem to have a limited shelf life.

Aminoethoxyvinylyglycine (AVG) is a recently developed product that safely and effectively blocks ethylene production. AVG is used commercially in apples - where it is being used to supplement or substitute for very expensive controlled atmosphere storage. However, a study by Leskovar and associates (2006) suggests that AVG may be of only limited use for extending the post-harvest life span of melons. They found that application of AVG to the foliage of the melon crop 1-3 weeks prior to fruit harvest slowed ripening of the fruit and occasionally reduced fruit size without providing any beneficial effect on keeping quality. Applying the AVG through the drip system prior to harvest did improve fruit firmness after harvest, but had no effect on other key quality indicators.

1-MCP (SmartFresh) is another new ethylene inhibitor which is being tested as a tool for extending the post-harvest lifespan of horticultural crops. Jeong (et al 2008) found that mature cantaloupes treated with 1-MCP gas just after harvest retained their firmness, both during storage and after processing into a fresh cut product. However, as was observed with AVG treatment, 1-MCP treatments failed to protect the fruit from other aspects of post-harvest decline like color change and watersoaking.

Many vegetable crops like lettuce and green bean are harvested at an immature growth stage. Exposing these crops to ethylene after harvest triggers a rapid increase in respiration and accelerates the loss of quality. Cho (et al 2008) showed that treating freshly harvest green beans with 1-MCP slowed the yellowing that typically occurs following exposure to ethylene. The 1-MCP treatments also appeared to protect the beans from the adverse changes (brown spot and watersoaking) that occur during storage at low temperatures (<7°C) for extended periods of time.

Sources :

  • Leskovar et al. (2006) HortScience 41: 1249-1252
  • Jeong et al (2008). HortScience 43: 435-438.
  • Cho et al (2008). HortScience 43:427-430.

Renting Honeybees Worth the $ in Pumpkin Fields

Although honeybees are not overly efficient as pollinators of cucurbits like melons and pumpkins, they may still help improve yields and fruit quality. Research out of Illinois indicates that while populations of wild pollinators like bumblebees and carpenter bees were often sufficient to get good numbers of fruit set in small fields of pumpkins - adding honeybees substantially increased the average size of the fruit. This increase in fruit size is critical for crops like pumpkin that are sold by weight. The greatest improvement in fruit size was seen in the larger Jack-O-Lantern types of pumpkin. The increase in fruit size was attributed to more thorough pollination of each fruit in fields with lots of honeybees. The average flower was visited 25-35 times/day in fields with honeybees, compared to 10-15 times/day in fields with only native bees. If honeybees are used at the recommended rate of 2-3 colonies/ha, the cost of custom pollination runs to about $200/ha. As this service resulted in a 10,000 kg/ha (40%) increase in pumpkin yields, adding honeybees resulted in a $1800/ha increased in net crop value based on a wholesale price of $0.20/kg (typical price for Saskatchewan). Honeybee colonies should only be introduced into the field within a couple of days of peak flowering of the crop - otherwise the bees will find other, more favored pollen sources.

Source : Walters and Taylor (2006). HortScience 41: 370-373.


Review of Mechanical Weed Control Options in Vegetable Crops

Weed control between and especially within the rows is critical in vegetable crop production. Although herbicides represent an efficient means of controlling weeds both within and between the rows, herbicide options are limited for many vegetable crops. Plastic mulches are useful for controlling weeds within the row but do little to slow weed growth between the rows. Hand weeding represents a last resort due to the cost.

At one time, mechanical tillage was the primary means of weed control in almost all crops. As costs of alternate methods of weed control increase, many growers are re-evaluating mechanical weed control options in their vegetable crops. Kelly, Pritts and Bellinder of Cornell University New York have recently published an interesting review of the performance of mechanical weed control options (HortTechnology 2007, vol 17 p 87-94). They consider use of the single or multi-unit rotary cultivators to be the present standard approach to mechanical weed control. Although these units can be very effective for weed control between rows, they are of limited value for control of weeds within the row. Additional downsides are the fact that rotary cultivators are; a) slow, b) tend to move weed seeds within the soil profile resulting in multiple weed flushes, c) cause compaction and general degradation of soil structure and d) do not work well in heavy textured wet soils.

Kelly and associates point out that the alternatives to rotary cultivators all have weaknesses as well as strengths. Flex tine harrows are fast, low cost and when properly adjusted and operated can do a decent job of controlling weeds both within and between rows. However, the efficacy of weed control achieved with flex-tine harrows can be highly variable, depending on the number of passes made, the size, type and number of weeds present in the field and the soil and weather conditions at the time of cultivation. Spider-type and finger hoes are also fast and relatively affordable ground driven units. Spider hoes do a decent job of controlling weeds between rows but are of limited value within the row, while finger weeders are gentle enough to provide weed control within the rows but are not aggressive enough to provide thorough weed control between the rows.

Brush weeders are a relatively recent development - these units work and look like street sweepers, with the rotating brushes shredding bigger weeds and smothering smaller weeds. If properly adjusted, brush weeders can be used both between and within rows without causing excess crop damage, at least in more robust crops like broccoli, corn and beans. As the brush weeder provides only minimal soil disturbance they do not promote multiple flushes of weeds. However, on the downside, brush weeders are slow, heavy and costly PTO driven units that can be difficult to adjust to differing row spacings.

Source: Kelly, Pritts and Bellinder (2007) HortTechnology 17: 87-94


Rotary Hoe Cultivation of Sweet Corn

While using some form of cultivator to control weeds between the rows is a fairly common practice in sweet corn production, controlling weeds within the row by cultivating is a more risky maneuver. Ideally, the method and timing of in-row cultivation are such that weeds are controlled before they can compete with the crop. In-row tillage in the early stages of crop development also tends to cause less crop damage. Multiple passes of the cultivator may be required to deal with weed flushes, but each pass adds to costs and also increases cumulative damage to the crop.

rotary hoeLeBlanc and associates (HortTechnology 2006 16: p. 583-589) looked at crop damage and yields of sweet corn after a rotary hoe was used for in-row weed control at various intervals after seeding. A rotary hoe (Fig.1). (Yetter Inc.) set to cultivate to a depth of 2" was used to cultivate within the crop rows from 1 to 4 times, beginning prior to crop emergence and running through until the crop reached the 6th leaf stage. They found that a single pass of the rotary hoe was safe in terms of crop damage and yields, irrespective of what stage the crop was at when the tillage event occurred. However, multiple passes with the rotary hoe resulted in increasing levels of crop damage that were reflected in reduced crop stand, delayed maturity and reduced yields. Unfortunately, the study did not address how the relative efficacy of weed control was influenced by the timing of cultivation and the number of passes used.

 

Source: LeBlanc et al. 2006. HortTechnology 16: 583-589


Shelterbelts Best for Protecting Transplants ?

In a study of treatments designed to reduce transplanting stress of muskmelons, researchers in Nebraska found that planting close to shelterbelts worked best. The warm and wind-free conditions provided by the shelterbelt increased the proportion of the seedlings that survived transplanting and also promoted their subsequent growth. Coating the root system of the seedlings with a super-absorbant polymer prior to transplanting also enhanced transplant survival. These polymers have the ability to hold large amounts of moisture; this moisture becomes available to the root system during periods of moisture stress. Anti-transpirant sprays designed to slow moisture loss from the leaves did not enhance either survival or subsequent growth. It should be noted that both heat and moisture stress after transplanting were limited in these trials. Research conducted at the University of Saskatchewan indicated that treating seedlings with long lasting abscisic acid analogs was very beneficial in enhancing seedling survival and re-growth after transplanting. The anti-transpirant effects of the ABA analogs were particularly beneficial if hot and dry conditions were experienced after transplanting.

Source : Hodges, Daningsih and Brandle (2006). HortScience 41:361-366.


Shelterbelts Pay Off

Although the benefits of shelterbelts are generally well appreciated by vegetable crops growers, too many vegetable fields in Saskatchewan are still out on the bald prairie. Cost is the most common reason growers cite for not establishing a shelterbelt system - particularly the cost of devoting substantial amounts of valuable land to unproductive trees. However, in a recent paper, Hodges and associates out of Nebraska clearly showed that shelterbelts could more than paid their way on a typical vegetable operation. Using beans as a “typical” crop, they looked at the rate of growth, yields and quality of a crop protected by a shelterbelt systems versus one grown out in the open. The shelterbelt was a 30' tall mix of mature ash and conifers planted perpendicular to the prevailing wind direction. The test plots were planted 30 to 60' from the shelterbelt ... but the shelterbelt effects were observed 200' or more from the trees. As expected, proximity to the shelterbelt reduced the average wind speed to less than 40% of in the open. This completely protected the bean crop from damage by storm winds (winds stronger than 4 m/s-1). Air temperatures adjacent to the shelterbelt were warmer during the day but cooler at night than in the open. By contrast, soil temperatures in the sheltered area averaged 4C warmer than in the open - this resulted in better emergence and early growth. The relative humidity was also higher in the sheltered area than in the open - this would be advantageous in drought-prone areas, but could exacerbate problems with disease in more humid regions. Plants in the sheltered area were earlier, heavier and taller than in the open - culminating in a 50% increase in marketable yields. Factoring in price premiums paid for early product, the gross value of the crop grown with the shelter was approximately 60% more than the crop in the open. The shelterbelt system used in this study occupied about 8% of the area of the field - leaving an overall increase in gross crop value of 52% for the shelterbelt protected crop. Even greater benefits would be expected with more sensitive or higher value crops in more extreme locations.

Source : Hodges, Suratman, Brandle and Hubbard (2004). HortScience 39:996-1004.


Slow Progress on Extending the Shelf Life of Melons

As melon fruit begin to ripen they produce large amounts of ethylene gas - and this gas in turn triggers a number of additional ripening reactions including fruit softening and weakening of the connection between the fruit and the rest of the plant. Although some of these ethylene responses are beneficial, they also ultimately lead the fruit to lose quality and become over mature. Unfortunately, the orange fleshed cantaloups that do well in the short growing season available in Saskatchewan also produce more ethylene than do the green fleshed honeydews - which may explain why locally grown cantaloups also seem to have a limited shelf life.

Aminoethoxyvinylyglycine (AVG) is a recently developed product that safely and effectively blocks ethylene production. AVG is used commercially in apples - where it is being used to supplement or substitute for very expensive controlled atmosphere storage. A recent study by Leskovar and associates (HortScience 2006 vol 41 p 1249-1252) suggests that AVG may be of only limited use for extending the post-harvest life span of melons. They found that application of AVG to the foliage of the melon crop 1-3 weeks prior to fruit harvest slowed ripening of the fruit and occasionally reduced fruit size without providing any beneficial effect on keeping quality. Applying the AVG through the drip system prior to harvest did improve fruit firmness after harvest, but had no effect on other key quality indicators.

Source: Leskovar et al. (2006) HortScience 41: 1249-1252


Some Tips on Lycopene

Lycopene which is the pigment that gives tomatoes and watermelon their red color appears to offer a wide range of health benefits. Cultures that consume a diet rich in lycopenes have reduced rates of a range of cancers (especially prostate) as well as improved cardiovascular health. Although there are no specific recommendations as to optimum daily intake of lycopene, Collins and associates (HortScience 2006 vol 41 p 1135-1144) review some the factors that can contribute to a diet rich in this nutrient. Red coloration is a clear indicator of a high lycopene content - think tomato, watermelon, guava, red grapefruit. Yellow or orange varieties of tomato and watermelon largely lack this nutrient. There is considerable variability in the lycopene content of differing varieties of watermelon and tomato - and breeders are beginning to release new lines that have been specifically selected for an elevated lycopene content. A greater appreciation of the importance of lycopene is also driving increased interest in red varieties of carrots. The lycopene content of tomato and watermelon peaks at full maturity and then stays fairly stable during cold storage and the preparation steps typically used for fresh products. While cooking result in substantial loss of the lycopene found in tomato, the lycopene that is left in the cooked product is actually more readily absorbed during digestion that if the tomato was consumed raw. Fortunately, the lycopene in raw watermelon is quite easily absorbed. The rate of degradation of lycopene in frozen products can be minimized by minimizing exposure to air and by keeping the temperature as low as possible.

Source: Collins et al. (2006). HortScience 41:1135-1144


Standard Fertilizers the Best Bet ???

Growers looking to improve their onion yields get the best return on investment costs by sticking to conventional fertilizer inputs. That is the conclusion of a two year study which examined the effects of 11 different “nonconventional” fertilizers or crop stimulants under standard production conditions in Oregon. The nonconventional products tested included various humic acid formulations, seaweed extracts, plant growth regulators and several foliar feed formulations. All nonconventional products were applied according to their label recommendations to onions otherwise supplied with standard inputs of fertilizer and pesticides. None of the nonconventional products improve crop yields or quality - and several were clearly detrimental to the crop. None of the organic fertilizer formulations tested met crop nutrient requirements - yields from the organic regimes were consequently substantially lower than with a standard fertility program. At a cost of $ 10 - 200/acre for basic materials plus the added cost of application - none of the non-conventional products improved the net profitability of onion production in this study. Growers interested in trying these products should carefully examine their effectiveness in small replicated trials before investing in large scale applications.

Source : Feibert, Shock and Saunders (2003). Nonconventional additives leave onion yield and quality unchanged. HortScience 38: 381-386.


Stem and Bulb Nematodes in Garlic

In mid-summer of 2008 garlic growers across Saskatchewan noted that their garlic did not look right.  The plants lacked vigor and the leaves were turning yellow beginning at the bottom of the plant.   Within a few weeks the tops were dead and the bulbs were distorted and decayed.    Assays of the diseased plants showed the presence of several known pathogens – one of which (Fusarium oxysporum f.sp. cepae) causes an array of symptoms very similar to those observed in the 2007 crop.  However the assays also showed that the affected bulbs and stems were loaded with microscopic nematodes which could also been causing or contributing to the problem.   Of particular concern is the Garlic Stem and Bulb nematode (Ditylenchus dipsaci).   This nematode is already widespread in temperate regions but infections of specific fields can usually be traced to the planting of garlic cloves or onion sets that came from nematode-infested fields.   Once introduced into a field the nematode can persist in a dormant state for many years until a suitable host crop is planted.  While these nemas prefer garlic and onions they can survive on a range of vegetable and grain crops.  When conditions are right (saturated soil) the nemas swim from the soil into the leaf sheaths of the young garlic plants.  They then move towards the base of the leaves where they begin to feed.   As they feed they inject a toxin into the leaf base which causes the affected tissues to die – leaving a characteristic yellow spotting of the leaf base (Fig. 1).    The nemas reproduce quickly during warm summer weather, with populations increasing by a factor of 1000 fold over the course of a single growing season.  As the bulbs begin to form the nema feeding results in loose, distorted growth with the outside of the bulbs showing a roughened corky texture.  Affected bulbs are prone to splitting and tend to separate from the roots at the basal plate (Fig. 2) – this opens the bulb to infection by the previously mentioned Fusarium pathogen. 

Problems with Stem and Bulb Nematodes are common in many of the major garlic production areas of the world (Ontario, California and China).   As the problem is introduced on planting materials growers should be cautious about the health of any garlic they plan on using as seed.   Where possible the garlic should be tested for the presence of nemas prior to purchase.   Heat treatment will reduce nema populations on the seed garlic (cloves immersed for 2 hours in 44-50oC  water), but may also damage the garlic resulting in reduced vigor.   Once the nemas have been introduced into the field they are very difficult to eradicate.   A four year rotation out of host crops is recommended.  Rotating with crops such as mustard, millet or marigold may further reduce nema numbers as residues of these crops appear to be toxic to the nemas.   While nemas can be effectively eliminated using chemical fumigants this practice is expensive, environmentally unsound and useless if the field is then replanted with nematode infected seed garlic.   Having the soil tested for nemas prior to planting is strongly recommended if there the area has a previous history of garlic/onion production.   While cool moist production conditions and fine textured (clay) soils are most favourable for the development and spread of the nemas, damage to the crop seems to be worse in warm, dry years.   While there are no lines of garlic that are truly “nematode resistant”, some vigorous growing lines appear to be better able to tolerate the nemas than others.  
See - Http://www.usask.ca/agriculture/plantsci/vegetable/resources/publication/2008resources/garlic_08.pdf


Strawberries in High Tunnels

Research at the University of Saskatchewan has shown that there is potential to produce excellent yields of high quality strawberries in high tunnels. The U of S trials used the day neutral type of strawberry that is planted fresh each spring. These plants take a while to develop, which delays fruiting. Earliness is always desirable in high tunnel production. Researchers at the University of Kansas looked at the potential to grow the higher yielding June bearing types of strawberry as an annual crop in high tunnels. Crowns of cv. Chandler and Sweet Charlie were planted in late fall - after all summer crops would have been harvested out of the high tunnel. They found that in cold years, the crowns that were overwintered in the high tunnels experienced less cold damage than crown planted under traditional field conditions. However, by late winter, the warmer temperatures in the high tunnels tended to cause the strawberry plants to break dormancy, leaving them susceptible to cold damage. Plants in the high tunnels had more fruiting branches and fewer runners than plants in the open. This converted to greater yields in the high tunnel. Fruit in the high tunnels were also ready for harvest several weeks ahead of open field conditions - representing an opportunity to capture a market premium. Fruit quality was good in the high tunnels, although grade-out increased if temperatures in the high tunnels became excessive.

Yields for day neutral strawberry in high tunnels in Saskatchewan (2005).

  Date of 50% Harvest Marketable Fruit (g/m2) Marketable %
High Tunnel Sept. 5 719 80
Low Tunnel Sept. 8 441 82

Source : Kadir, Carey and Ennahli (2006). HortScience 41: 329-335.
University of Saskatchewan - Vegetable Crops Research Update (2005).


Squash Fields Prove Pretty Tough

Partial defoliation or even complete loss of plants due to insects, hail, mechanical damage or drought are unavoidable in vegetable crop production. The impact of this type of damage on yields and quality varies with the crop, the severity of damage, the timing of the loss and the number of plants left in the field after the damage event. In a study of the response of squash to varying degrees of defoliation, researchers in the North-Eastern U.S. showed that squash tolerated the loss of up to 33% of the total crop leaf area with no loss in yield ... if the damage event occurred prior to fruit set. It did not appear to matter if the damage involved the complete loss of some plants as would occur in the event of mechanical damage or if each plant lost a portion of its total leaf area as would be typical in a hail event or with insect feeding. After fruit set, the crop was less able to tolerate this type of damage. In general, fields with high initial plant populations were better able to tolerate the loss of a few plants or the partial defoliation of the entire field. Partial defoliation had no impact on fruit quality ... but did tend to decrease the average fruit size as crop maturity was delayed. In areas with a more limited growing season, crops may not have time to fully overcome the check in growth caused by a defoliation event. However, a crop’s ability to recover from any damage event can be improved if the grower implements appropriate management steps as soon as possible. A light application of N fertilizer, some water and treatment with a protectant fungicide may be all the TLC the crop needs.

Source : Rangarajan, Ingall, Orzolek and Otjen (2003). HortTechnology 13:463-467.


Tips on Slowing Nutrient Loss from Vegetable Fields

Nutrient loss from vegetable fields represents an economic loss to growers and a preventable source of environmental damage. Vegetable crops are prone to nutrient loss because of; a) high rates of application of highly soluble, leaching prone fertilizers, b) limited crop recovery of applied nutrients due to the limited rooting system and short cropping duration typical of vegetable crops, c) the concentration of vegetable crop production on coarse textured soils that are prone to nutrient loss through both erosion and leaching.

Hartz (Hort-Technology 2006 p 390-402) and others suggest the following methods that will help vegetable growers to increase fertilizer use efficiency and/or to reduce nutrient losses;

a) base fertilizer applications on recommendations that are appropriate to your region, method of production, cropping duration, anticipated yield potentials etc. Recommendations developed for growers in California are usually not appropriate for growers in Saskatchewan.

b) base fertilizer applications on the results of soil tests rather than on past practices, and then use in-season tissue tests to confirm that the resulting soil nutrient levels are suitable for optimal crop development

c) use appropriate methods of fertilizer application - surface applied nutrients are more prone to loss by surface run off and volatilization than fertilizers incorporate at the time of application. In row crops the total amount of fertilizer applied can be significantly reduced by concentrating the nutrients in bands adjacent to the crop rows.

d) time nutrient application to match crop needs. Heavy applications of nitrogen fertilizers prior to planting are generally undesirable as the N needs of developing seedlings are limited, leaving the fertilizer N open to loss by denitrification and leaching. As the crop develops, N requirements tend to increase - these needs can be most efficiently and accurately met by split applications of N, delivered by side-banding or through the irrigation system. As fall approaches, it may be desirable to cut back on the N applications to encourage the crop to mature.

e) timely, accurate and uniform irrigation will increase crop growth without causing nutrient loss through run off or leaching

f) once the crop has been harvested plant cover crops to reduce nutrient loss by wind erosion and surface run

e) use deep-root rotational crops to return any nutrients that have been leached deep into the soil back to the soil surface where they will be available to subsequent vegetable crops. In Saskatchewan, fall planted rye does an excellent job of e) and f).

Source : Hartz (2006) Hort-Technology, pp. 390-402


Towards the Perfect Onion Ring

Although it is well known that onion yields are reduced by moisture stress, the impact of water shortages on quality is less clear. Onions exposed to at least mild moisture stress, especially late in the growing season, tend to be more pungent with a higher dry matter content than onions grown with consistently abundant supplies of moisture. Stronger flavored onions with a high dry matter content tend to maintain their quality during long term storage. When onions are being grown for the onion ring market, a strong flavor is not overly desirable, but a high proportion of bulbs with a single center is very important. Production contracts often stipulate the minimum % of single centers (typically > 75%). The tendency to produce single versus multiple centers is influenced by both genetics and production conditions. In a 2007 trial evaluating Spanish type onions, the U of S found that most available cultivars had > 90% multiple centers when grown under typical production conditions in Saskatchewan. The sole exception was Teton Hybrid from Norseco - 100% of its bulbs had single centers. The excessively high proportion of bulbs producing multiple centers in this trial suggests that the production conditions may not have been ideal. Any factor that interrupts bulb development will lead to an increased proportion of bulbs with multiple centers. Shock et al (2007) found that a single short period of moderate drought stress caused a significant increase in double centers - often without having any impact on bulb yields. The onion plants appeared most susceptible to this stress when they were in the 4-6 leaf stage. Although yields from the U of S trial were excellent, the high proportion of bulbs with multiple centers suggests that even more careful moisture management of the crop is required.

Source : University of Saskatchewan Vegetable Cultivar Trials for 2007 (http :
Shock, Feibert and Saunders (2007). HortScience 42: 1450-1455.


What to do with that straw mulch in your garlic patch ?

Fall planting garlic has the potential to increase yields, providing the crop survives the winter. Previous studies conducted by the University of Saskatchewan suggest that mulching fall-planted garlic with straw will improve overwinter survival and subsequent yields - especially in years or situations where the winter snow cover is limited. The straw mulch is typically removed early in the spring ... otherwise the soil is too slow to warm and crop development is delayed. The question then arises ...what to do with all that used straw ? One answer may be ... put it back on again a bit later! Garlic is a cool season, moisture-loving crop. Using the left over straw as a mulch between the rows should keep the soil cool and moist, while also suppressing weeds. In mid-June we took the straw that had previously been used as an overwinter mulch and spread it over one half of our garlic research trial. At that time, the garlic plants were already 30 cm tall. We attempted to direct the straw between the rows. Although some plants were lightly covered, wind action soon uncovered these plants. Any weed escapes in the straw mulched plot were controlled by hand weeding. The non-mulched plots were also hand weeded. The crop was harvested at maturity and yields and bulb quality assessed.

The 2005 growing season was relatively cool, with above normal rainfall. This resulted in excellent vigor and growth in the garlic trial. The mulching treatment appeared to delay maturity of the garlic crop. In the stiffneck types of garlic, this delay resulted in a 17% increase in total bulb yields. No corresponding yield benefit was observed when softneck types of garlic were mulched. Bulb color was often improved by the mulching treatment - but mulching also seemed to increase problems with bulb decay. Bulbs from the mulched areas seemed prone to falling apart, releasing the individual cloves.

In conclusion, using leftover straw appears to have both advantages and drawbacks. Greater benefits might be anticipated in a warmer year. Removal of the straw as the crop begins to mature may also be advisable.

Source: Vegetable Program's 2005 Garlic cultivar and cultural trials


Which Variety of Asparagus Should I Plant ?

Asparagus represents an interesting diversification opportunity for Saskatchewan vegetable growers. Demand for asparagus is always strong at local farmer’s markets. There is also interest in the crop at the retail level as local asparagus is ready just as the major production regions in California and Washington are finishing up for the season.

Selection of the best variety is critical for successful asparagus production, as a good patch will produce for two decades. In 1996, the University of Saskatchewan commenced a variety evaluation program for asparagus. Over 20 varieties were planted including old standards like Martha Washington and Viking, as well as many of the new all male lines including several from the Jersey series and some then un-named lines from the asparagus breeding program at Guelph. Unfortunately, the trial was attacked by Fusarium crown rot in 1998 and by 2000 much of the patch had died out due to this disease. Jersey Giant and Jersey Knight appeared to be the most resistant to the Fusarium, but after 3 years less than 20% of these plants were still standing.

Horticulture Nova Scotia has recently published yield and quality results for 6 years in a similar asparagus variety trial. They found that two of the Guelph lines (Guelph Millennium and Guelph Tiessen) performed best. These lines also performed well in Ontario trials. However, all of the Guelph lines are more sensitive to Fusarium than Jersey Giant. Therefore, growers considering planting asparagus must balance disease resistance issues against yield potential when making their variety selection.

Source : Horticulture Nova Scotia Vegetable Research and Variety Trials for 2002.



Success Factors for a Farmers' Market

Managers of farmers’ markets across Indiana ranked the factors contributing to the overall success of the market as; 1) location, 2) the number of vendors attending the market (more is better) and 3) management of the market. The key factors influencing whether vendors opted to continue using the farmers market as a sales outlet were; 1) number of customers seen and b) the fees paid to the market.

Contrary to initial expectation, the higher the fee associated with using the market, the more likely the vendors were to return. This likely reflects use of the fees to promote the market or enhance the market facility. The number of customers attending the market increased with the range of products being offered. The presence of concession stands and cooking demonstrations also increased customer traffic but the presence of musical entertainment and picnic areas were perceived as being detrimental to overall use of the market.

The picnic areas were considered unsightly and the trash attracted flies and wasps to the market area. The music was perceived as either distracting from the customers’ ability to interact with the grower/vendors or that the people attracted to the market by the music were not necessarily interested in purchasing produce.

Source : Hoffman, Dennis and Marshall (HortScience 44:712-716 2009)


University of Saskatchewan