INFLUENCE OF SOIL TEMPERATURE AND MOISTURE CONDITIONS ON GROWTH PROTEIN PRODUCTION OF MANITOU AND TWO SEMIDWARF MEXICAN SPRING WHEATS

Abstract

Three spring wheat cultivars (Triticum aestivum L.), Manitou, Pitic 62, and QK1-13, were grown in field plots containing a thermally controlled watercirculation system. The system provided two controlled root-zone temperatures (10 and 28 C) and one uncontrolled seasonal temperature (18 C), which represented mean summer soil temperatures of the Cryoboreal (8–15 C), the Mesic/Thermic (15–22/> 22 C), and the Boreal (15–18 C) climatic classes of the Canadian Soil Climatic Classification System. Three soil moisture conditions were characterized in terms of a soil moisture sufficiency index (SMI) levels were selected to correspond to the subclasses, Arid/Semiarid, Humid/Subhumid, and Perhumid. When temperature treatments were applied between emergence and the third-leaf stage of development, average yields from all treatments usually ranked with temperatures associated with the Cryoboreal > Boreal > Mesic/Thermic Classes. High soil temperature depressed the yields of the Mexican cultivars Pitic 62 and QK1-13 more than Manitou. Manitou appeared to tolerate a wider range in temperature than the Mexican cultivars, especially when seeded early (May). Yields of all cultivars were highest frequently under temperature and moisture conditions associated with the Cryoboreal and Boreal Subhumid classes. At these temperatures, yields were reduced markedly under Arid/Semiarid moisture conditions and depressed slightly under Perhumid moisture conditions. Grain yields were relatively low under the warm soils at all moisture conditions. In general, protein content was high under Arid conditions for all three temperatures. The protein content diminished with decreasing moisture stress under warm and cool temperatures. Thus, lowest protein concentration occurred under temperature and moisture conditions associated with the Cryoboreal Perhumid Class. Fertilizer (N + P + K) had greater effect at temperatures associated with cooler soils. Under all moisture and temperature conditions, Pitic 62 gave a much heavier root weight and a more fibrous root system than either Manitou or QK1-13.