Effects of Subterranean Clover Interseeding on Grain Yield, Yield Components, and Nitrogen Content of Soft Red Winter Wheat

Abstract

Much literature has documented the effects of interseeded legumes on forage production and quality. Little information is available, however, concerning the effects of interseeded legumes on small grains produced for grain. The objective of this study was to determine the effects of four interseeded subterranean clover (Trifolium subterraneum L.) cultivars on soft red winter wheat (Triticum aestivum L. cv. Coker 762) grain yield, yield components, and N accumulation. A field study was conducted for 3 yr in eastern Texas on a Sawtown fine sandy loam soil (fine loamy, siliceous, thermic Glossic Paleudalf), which contrasted the effect of four subterranean clover cultivars, ‘Mt. Barker’, ‘Nangeela’, ‘Nungarin’, and ‘Woogenellup’, on interseeded wheat yields. Interseeding decreased grain yields the first year due to apparent competition between wheat and clover, with all of the clover treatments producing lower yields than the control. All clover cultivars significantly increased wheat grain yields the second year, however, presumably because of N that was symbiotically fixed by clover during the first growing season. Interseeded Nungarin, Woogenellup, Mt. Barker, and Nangeela clovers increased yields by 84, 112, 233, and 283%, respectively, as compared with first-year yields. Regression analyses showed that Nangeela provided the highest N fertilizer equivalent of 59 lb/acre to the interseeded wheat. The N supplied by the clovers in the second study year was directly correlated with maturity, with later-senescing cultivars providing the most N. Kernels per spike and kernels per square foot were positively affected by clover interseeding the second year. Grain N contents and N accumulation by the wheat crop were influenced in the same fashion as grain yields. Wheat grain yields decreased the third year in relation to the prior growing season; probably a result of disease pressure and a later planting date. Third year grain yields were similar to those obtained the first year, but significant differences between the clover treatments and the control observed the first year were absent.