Nitrogen mineralization potentials (Nₒ) were determined on soil from a long-term crop rotation tillage experiment on a Palouse silt loam (fine-silty, mixed, mesic Pachic Ultic Haploxerolls). Crop rotations included continuous winter wheat (Triticum aestivum L.), alternate winter wheat and (pea Pisum sativum L.), alternate winter wheat and spring wheat, and pea-alfalfa (Medicago sativa L.)-green manure, followed by 5 y of alternate spring wheat and winter wheat. Tillage variables were moldboard plowing, chisel plowing, or no-till. Long-term N fertilizer rate plots were also studied on a Ritzville silt loam (coarse-silty, mixed, mesic Calciorthidic Haploxerolls). The tillage plots were cropped annually, whereas the fertilization rate plots were alternately fallowed and cropped to winter wheat with and without spring supplemental irrigation. Moldboard plowing resulted in uniform Nₒ values throughout the top 15 cm of soil, but N mineralization potential (Nₒ) was greater for chisel plowing and no-till than for moldboard plowing at the 0- to 5-cm depth and less at the 5- to 10- and 10- to 15-cm soil depths. The net result was that average Nₒ for 0 to 15 cm was unaffected by tillage or crop rotation in the fall sampling. In the spring sampling, average Nₒ for either chisel plowing or no-till was significantly higher than for moldboard plowing. Also, peas-alfalfa-green manure followed by alternate spring wheat-winter wheat had a significantly higher Nₒ averge than both continuous winter wheat and winter wheat-pea but was not different from winter wheat-spring wheat. The Nₒ of the tillage and the crop rotation management treatments were significantly greater with samples obtained in the fall than from those obtained in the spring. Nitrogen mineralization potentials increased linearly with increased N rate on both the dryland and supplemental irrigated treatments. However, supplemental irrigation uniformly increased Nₒ compared with the corresponding nonirrigated treatments.

The timeliness of P availability to a plant is important for maximum plant growth. There is little information pinpointing the critical time(s) in the life cycle of winter wheat (Triticum aestivum L.) at which P uptake is the most important for maximum growth response. The objectives of this research were: i) to determine the effects of removing P from the growing medium during progressive stages of growth on dry matter production and P uptake of winter wheat; and ii) to compare the P demand pattern of winter wheat with that known for spring wheat. ‘Centurk’ winter wheat was grown using a modified Hoagland's nutrient solution in a greenhouse environment. Treatments consisted of evaluating the plant response to the time grown with and without available P in the nutrient solution. This was accomplished by replacing the complete nutrient solution with a nutrient solution devoid of P and allowing plants to continue growth to physiological maturity. Winter wheat had taken up sufficient P by the first node stage to ensure maximum dry matter production of the mature roots and tops. Phosphorus availability in later growth stages did not significantly increase mature root and top dry matter production. Maximum grain yield at maturity, however, was only realized when P was available through the mealy-ripe stage (Feekes' Scale 11.2) of grain development. It appears that after noding stage only a small amount of P may be needed to allow carbohydrate translocation mechanisms to function. Spring wheat differs from winter wheat in that it only requires adequate P up to heading to produce maximum grain yields.

The most extensive spring freeze reported on winter wheat (Trificum aestivum L.) in the Great Plains occurred in Kansas and adjoining states in 1981. We related magnitude of injury to prevailing temperatures and compared consequences of freeze injury in 1981 and previous years. The injury threshold nearly paralleled the O°C isotherm during the freeze. Production losses ranged up to 85% in individual counties and averaged 62% in the affected area and 31% statewide in Kansas. Low grain production in 1981 contrasted with record production in states reporting freeze injury to winter wheat during previous years. Modeling showed record winter wheat production after spring freezes other years was associated with generally favorable conditions throughout the growing season, early development of wheat during the spring, and extraordinarily favorable conditions after the freeze. Spring freeze injury might affect winter wheat production locally, but production over large areas was frequently favored by conditions associated with localized freeze injury.

In soil environments (brown soils formed on loess and loess-like deposits) occupied by specialized crop rotations (no. 1 - maize, sugar beet, barley, clover; no. 2 - winter wheat, winter wheat, maize, winter wheat) the author found toxin-producing fungi of the genus Aspergillus, Penicillium, Helminthosporium, Monosporium, Acremonium, Arachniotus, Mortierella, Pullularia and Verticillium, possessing specific aptitudes to degrade the aflatoxins B1; B2; G1; g2. The author demonstrated in experiments made in vitro that the output of the degradation process ranging between 16.3% and 89% depended on the metabolic properties of the separate strains of microorganisms, the number of cells, and the duration of the culture growth