Features of high-yielding wheats grown at two seed rates and two nitrogen levels

Abstract

Four wheats of similar maturity were compared at two seed rates and two nitrogen levels. The cultivars were two high-yielding Mexican semi-dwarf wheats, Pitic 62 and accession WW 15, one local semidwarf crossbred, HMR, and one Australian variety, Robin. At each of two sites WW 15 yielded most grain and Robin the least. Yield components, growth, development and leaf characters were studied at one site. The semi-dwarf wheats had a higher proportion of ear weight at anthesis and set more grains per ear and per unit area. The high yield of WW 15 was associated with many grains per ear and a dense ear population. There were relatively small differences in total dry matter yield and leaf area index. WW 15 formed the most leaves on the main stem, had the shortest period from flag leaf emergence to anthesis and showed delay in the senescence of its flag leaves. Its leaves were also particularly narrow and small. The early effects of a higher seed rate on crop growth diminished with time in the main experiment but resulted in a small increase in grain yield. Nitrogen stimulated growth throughout the season, but the increased vegetative potential was not fully reflected in grain yield. Both nitrogen and the higher seed rate hastened flag leaf senescence.