RESULTS AND DISCUSSION (continued)

8. True Seeding Depth

True seeding depth (plant emergence distance) was estimated in the late fall by measuring the distance from the seed to the area on the winter wheat plant where the green chlorophyll was first noticeable.

Seeding depth for all the fields surveyed ranged from less than 0.5 cm (0.2 inches) to 6.4 cm (2.5 inches) with an average of 2.0 cm (0.8 inches). Seeding depth proved to be a critical management factor in this program and all winter wheat fields (a total of three fields in 1992-93) that were seeded 5 cm (2 inches) or deeper were not successfully overwintered and were reseeded to spring crops.

The average winter wheat seeding depth in fields that did not have establishment problems was 1.8 cm (0.7 inches) with a range from 0.9 cm (0.35 inches) to 3.1 cm (1.2 inches).
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9. Seeding Date

The average seeding date of the winter wheat fields in this survey fell within the optimum time period for planting in the project area. However, there was an extremely wide range of seeding dates and many fields were seeded later than the recommended seeding dates in all three years. Poor harvest weather meant that the previous crop was often not harvested early enough for farmers to seed their winter wheat during the optimum period. This also meant that many farmers who had intended to seed winter wheat put their seed back into the bin once the optimum seeding date had passed.

Harvest date of the previous crop determines the earliest date that a field is available for the seeding of winter wheat. Chemical fallow and sweet clover fields were available for seeding early and the seeding date for these fields nearly always fell within the recommended time period for winter wheat.

The falls of 1992 and 1993 were extremely wet and there were many harvest problems. One would expect that Polish canola stubble would be available for seeding winter wheat earlier than cereal stubble. However, wet harvest conditions and the fact that canola does not deteriorate as quickly in the swath may have disrupted the normal harvest patterns thereby delaying the seeding of winter wheat into canola stubble during the years of this study.

10. Fall Plant Growth and Development

Ideally, winter wheat seedlings should enter the winter with well developed crowns. However, only 51 percent of the winter wheat fields in this study had plants with well defined crowns by freeze-up. The absence of crowns was associated with late seeding dates and deep seed placement.

Crown development usually starts once the plant has three fully developed leaves. The average winter wheat plant in this program entered the winter at Haun stage 3.1 (three fully developed leaves and a fourth leaf just emerged). This is consistent with the observation that 51 percent of the winter wheat fields had plants with well defined crowns.

The minimum and maximum Haun stages recorded were 1.2 (second leaf just starting) and 5.8 (sixth leaf just about fully developed), respectively, indicating that there were large differences among fields in the stage of development at which plants entered the winter. As a general rule, the Haun stage at freeze-up was lower for plants in fields where seeding date had been delayed by the removal of the previous crop.

11. Winter Damage

There was evidence of minor winter damage in 30 percent of the fields in this program. Most of the winter damage was restricted to small patches associated with exposed hills and headlands adjacent to roads where the stubble was thin or badly knocked down.

Winter wheat fields with poor snow trapping capability due to excessive stubble breakdown suffered the most extensive winter damage. Included in this group were a few chemical fallow fields and a field that had been seeded by an air seeder equipped with 12 inch (30 cm) sweeps. However, even in these fields the winter damage was minor and none of the fields were reseeded to a spring crop or summerfallowed. Certainly, problems that occurred at the time of seeding (poor seed delivery by drills, seed placement that was too deep, and seed that was left uncovered on the soil surface) placed far greater restrictions on crop productivity than did damage caused by winterkill.
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12. Problem Soils

Large areas of moderately to severely saline soils were recorded in 31 percent of the fields in this program. The winter wheat in severely saline areas was often badly damaged during the winter and most severely saline areas had little or no crop remaining by the end of June. Winter wheat growing on moderately saline soils had reduced vigor and was more susceptible to drought stress. The increased crop stress in saline areas usually resulted in greater tiller senescence (die-back) and floret abortion (head blasting) during periods of drought stress.

Winter wheat production is not recommended on fields that have large areas that are severely or moderately saline. Spring barley and oats have performed better than winter wheat on moderately saline soils and fields where salinity is a major problem should be sown to salt tolerant perennial grasses.
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13. Spring Flood Damage

Most of the fields in this program had good surface drainage. Spring flood damage was confined to sloughs where the water stood for an extended period of time. These slough areas are often inaccessible for early spring seeding.
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14. Chaff Rows

There was poor winter wheat establishment, suppression of winter wheat growth, increased problems with volunteer crops and/or delayed winter wheat maturity due to unspread chaff windrows in 14 percent of the fields surveyed in this program. In one field, winter wheat failed to establish in unspread canola residue windrows left by a combine that was not equipped with a chaff spreader. However, delayed winter wheat maturity, and therefore harvest, was the most common problem caused by unspread chaff rows. In one chemical fallow field, a delay in winter wheat maturity due to unspread chaff windrows from a crop harvested two years previously demonstrated the long term influence that heavy crop residues have on crop growth and development.
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