Winter Survival Of Wheat Research Articles

Abstracts of papers presented at the annual meeting of the Canadian Phytopathological Society University of British Columbia, Vancouver 14-17 August 1988

Abstracts of papers presented at the annual meeting of the Canadian Phytopathological Society University of British Columbia, Vancouver 14-17 August 1988

Predicting Soil Temperatures to Indicate Winter Wheat Mortality

AbstractTillage effects on soil temperature that affect winter wheat survival (Triticum aestivum L.) were investigated from 1981 to 1985 at Fargo, ND. Tillage systems used all 4 yr were reduced (disked) and no‐till tall stubble (seeding directly into 20‐cm standing stubble). Conventional tillage (plow, disk, and harrow) in 1981–82 and 1982–83, and no‐till short stubble (seeding directly into 5‐cm stubble) in 1983–84 and 1984–85 comprised the third tillage system used for comparisons. Survival of winter wheat in the no‐till tall stubble system was near 100% in each of the 4 yr, while in 2 of the 4 yr, survival was 50% or less in the other tillage systems. Differences in survival were attributed to warmer soil temperatures in the tall stubble system. Hourly soil and air temperature measurements and snow depth were used to develop a statistical model that predicts daily minimum crown depth (3 cm) soil temperatures (R2 = 0.92). An independent set of data was used to test the model; soil temperatures within the range considered critical for winter wheat were predicted to an accuracy of 1 °C. Predicted crown depth soil temperature may be used to indicate winter wheat mortality.

THE EFFECT OF N AND P FERTILIZATION ON WINTER SURVIVAL OF WINTER WHEAT UNDER ZERO-TILLED AND CONVENTIONALLY TILLED MANAGEMENT

A preliminary field study was conducted to investigate the influence of fall applications of nitrogen and phosphorus on winter survival of winter wheat on zero-tilled and conventionally tilled land. Nitrogen fertilization tended to decrease winter survival while phosphorus fertilization tended to increase survival. A N-P interaction was observed, with the decrease in survival in response to added N being more evident in the absense of applied P. Balanced N-P fertilization may therefore result in highest winter survival in both conventionally tilled and zero-tilled winter wheat. Key words: Zero-tillage, winter survival, nitrogen, phosphorus, winter wheat

Date of Seeding, Fall Growth, and Winter Survival of Winter Wheat and Rye

AbstractIn the northern part of the North American Great Plains the level of cultivar winterhardiness required for winter cereal production is extremely high. Therefore, for successful production in this area close attention must be paid to all factors that influence a plant's ability to attain maximum winterhardiness. In this study, the influence of date of seeding on fall growth and winter survival of winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) was assessed in seven trials grown on udic and typic boroll soils in the northcentral part of the agricultural area of Saskatchewan. In these trials, four wheat and two rye cultivars were seeded at 2 week intervals between 1 August and 15 October in each of 3 years. During this period, rye accumulated shoot dry matter at twice the rate of wheat. However, as expected, a decrease in shoot dry weight of both wheat and rye occurred with each succeeding delay in seeding date. The only meaningful winter damage that was observed in the rye was for the last two seeding dates with ‘Cougar’. The effect of date of seeding on survival of wheat was not consistent among trials. However, average survival was highest for the 15 August and 1 September seeding dates. This was 4 to 6 weeks prior to the onset of fall conditions favorable for cold acclimation. Differences in survival among wheat cultivars were not influenced by seeding date. This allowed for utilization of the Field Survival Index to evaluate the relative effects of suboptimal seeding dates on winter survival potential of cultivars. These results demonstrate that the Field Survival Index can be used to evaluate the effects of certain management practices in addition to inherent cultivar potential on winter survival.

Determining Winter Wheat Stand Densities Using Spectral Reflectance Measurements1

AbstractRemote sensing would be a valuable tool to decision making and crop forecasting groups to gain knowledge of winter wheat acreage, extent of winterkill, and the potential acreage that may be reseeded to spring crop. To simulate winterkill, seven winter wheat (Triticum aestivum L.) stand variables of 0, 10, 20, 40, 60, 80, and 100% of full stand (full stand = seeding rate of 67 kg/ha) were established by seeding to stand. The plots, 20 ✕ 20 m, were located on Williams loam (fine‐loamy mixed, Typic Argiborolls) near Sidney, Mont. An Exotech Model 100‐A ground truth radiometer, corresponding to LANDSAT multispectral scanner (MSS) bands 4, 5, 6, 7, (0.5 to 0.6, 0.6 to 0.7, 0.7 to 0.8, and 0.8 to 1.1µm), was used to measure reflected radiation at 0930 hours MST on clear or nearly clear days. We chose the comparatively simple, but physically meaningful normalized difference vegetation index, VI7 = (MSS7 − MSS5)/(MSS7 + MSS5), with the variant of substituting MSS6 for MSS7 to illustrate crop cover differences. In an attempt to better distinguish soil background from crops and to improve on the crop‐vegetation index relationship, we included the more complex, but also physically meaningful, perpendicular vegetation index, PVI = [(Rgg5 − Rp5)2 + (Rpp7 − Rp7)2]1/2 with the variant of substituting MSS6 for MSS7.Early in the season, VI7 delineated stands ≥40% from those <40%, allowing a judgment as to whether or not a field would need to be reseeded to spring crops. A winter wheat survival of about 40% is generally considered adequate to provide a reasonably good stand if plants are properly spaced. The 10 and 20% plots became distinguishable from the soil background at a biomass accumulation of about 30 kg/ha (LA1 ≃ 0.06).There was no advantage of using either variant of the PVI over the VI7 when plotted against leaf area index (LAI) or leaf dry matter (LDM). Both yielded a family of straight lines, with indices of determination ranging from 0.796 to 0.942, and slopes decreasing from the 10% plot to similar slopes for the 80 and 100% plots.

Crown‐Depth Soil Temperatures and Winter Protection for Winter Wheat Survival

AbstractWinterkill of winter wheat (Triticum aestivum L.) can be a serious problem in marginal winter wheat growing areas of the world. Plants that are well hardened or conditioned when entering the winter season may withstand crown‐depth temperatures of about −20°C; less hardened cultivars, about −16°C.Experiments were initiated on a Williams loam (fine‐loamy, mixed Typic Argiborolls) near Sidney, Montana, to establish snow depth and protection requirements, based on a −16°C limit criterion at crown depth (3 to 5 cm), for reasonable assurance of winter wheat survival.Soil temperatures were measured at 0‐, 3‐, 10‐, and 50‐cm depths on fallow soil under various snow depths. In addition, a deep furrow drill was used to seed winter wheat on summer fallow with soil temperatures measured at 0, 3, and 10 cm and in standing stubble with soil temperatures measured at 0‐, 5‐, 15‐, 30‐, 60‐, and 90‐cm depths. Providing no other confounding factors such as snowmelt and subsequent ice‐crust formation are present, about 7 cm of snow is probably sufficient to prevent winterkill even when air temperatures occasionally approach −40°C. The deep furrow drill formed furrows deep enough to trap about 6 to 7 cm of snow. Standing stubble provided additional protection and caught and held snow.

Influences of Method of Seeding and Moisture on Winter Wheat Survival and Yield1

AbstractField experiments were conducted during 1963–1967 at Mandan, N. Dak., to compare effects of furrow and surface drilling methods and fall and spring moisture differentials on winter wheat (Triticum aestivum L.) survival and yield. A system was developed to permit collecting winter wheat plants from frozen soil for survival counts.Average survival in February and March and final grain yields were significantly greater for furrow than for surface drilling. Survival often decreased substantially between early January and mid‐February, particularly in 1965 when survival decreased from over 90% to almost zero. Increased fall moisture also increased survival. Winter wheat survival was significantly correlated (r > 0.92) with cumulative degree days after December 1, calculated from a base of either _17.8 or −2.2°C. Furrow planting aided in trapping snow around the plant crowns, which may have reduced tissue desiccation and provided additional water during mid‐winter thaws. These results suggest, therefore, that the amount of protection afforded the crown, soil moisture conditions during the winter months, and intensity and duration of freezing prior to February 15 all affect winter wheat survival in frozen soils.

CHANGES IN COLD HARDINESS ACCOMPANYING DEVELOPMENT IN WINTER WHEAT

The cold resistance of 18 varieties of winter wheat hardened in a growth chamber was studied at various stages of development and the results were compared with the field survival of these varieties.In the growth chamber two maxima of cold resistance were found, the first for the dry or freshly moistened seed and the second when plants had approximately 4 to 6 leaves. Varietal differences were found in the exact timing of this second maximum and in its duration. As a result, some varieties changed their rank for cold resistance as they developed.Partial agreement was observed between the field survival of varieties sown at different dates and the changes in cold resistance of these varieties as they developed in the growth chamber.From these tests, a procedure has been developed that should enable fairly reliable predictions to be made of field survival of winter wheat in any area where low-temperature resistance is the major factor in winter survival.

CONTROL OF VARIATION WITHIN PLOTS IN WINTER SURVIVAL TRIALS OF WHEAT AND RYE

Variations in survival of winter wheat and winter rye were controlled among rows within plots by applying the principle of uniform packing through use of the Smith–Bergen Plotmaster seeder. Thus a source of serious bias in varietal comparisons for winterhardiness was largely eliminated.

VARIATION AMONG ROWS IN POWER-SEEDED CEREAL VARIETY TRIALS

Variations in survival of winter wheat and in yields of winter wheat, spring wheat, and barley were obtained among rows of power-seeded variety trials where there was differential packing by tractor wheels. This variation makes variety comparisons difficult and introduces bias in single-row-plot and two-row-plot trials. A power seeder with four drive-wheels giving uniform packing of all rows greatly reduced the variation in yield among rows.