Yield and quality of four wheat crops subsequent to annual and perennial irrigated pastures

Abstract

Four consecutive wheat crops were grown after each of three annual and three perennial irrigated pastures, each group consisting of a legume, a grass, and the same grass supplied with fertilizer nitrogen. Tiller numbers and grain yields were greater after perennial pastures than after annual pastures. Nitrogen supplied to each wheat crop at the rate of 112 kg/ha prevented the differences in tiller number and in grain yield from developing. A greater rate of mineralization of nitrogen after perennial pastures than after annual pastures was sustained for 4 years, and this was associated with superior yields, tiller numbers, nitrogen content, and grain quality in each wheat crop. Although the concentration of total nitrogen in the 0–7.6 cm soil horizon after the two species of grass did not differ, there was approximately twice as much nitrogen taken up in the four wheat crops after the perennial grass pasture as after the annual grass pasture. At all levels of available nitrogen, the ratio between nitrogen in the grain and in the straw + chaff was c. 2 : 1.