Fertilizing Dryland Spring and Winter Wheat in the Brown Soil Zone1

Abstract

AbstractNitrogen and P fertilizers were applied to spring or to winter wheat to measure yield response during an 11‐year period at Huntley, Montana. The soil was a typical Brown soil of the Northern Plains, moderately low in plant available P. Annual precipitation averages 10 to 13 inches in this soil zone. In a wheat‐fallow cropping system, spring wheat grain yields were increased in only 1 year by NP fertilization and decreased in 1 year by P and by NP fertilization. During a 3‐year period, winter wheat yields were not increased by fertilization and were decreased by N and by NP fertilization in 1 year and by N fertilization in another year. Phosphorus and NP fertilizers caused accelerated growth and ,soil moisture use during early spring. Accelerated growth persisted until heading, then gradually disappeared. Soil moisture use was at a lower rate during the heading to maturity period because of decreased moisture supply. Both crops were under drouth stress during the critical heading to maturity stage.With natural precipitation, spring and winter wheat grain yields averaged about 30% of the potential grain yield with soil moisture removed as a limiting factor. Because of the drouth stress, increased vegetative production usually did not carry through to increase grain yields.