Yield and yield components of relay-intercropped wheat and soybean

Abstract

Relay intercropping, where soybean [ Glycine max (L.) Merr.] is sown into standing wheat ( Triticum aestivum L.), alleviates several problems associated with delayed soybean sowings following wheat in a double-cropping system. However, relay intercropping has resulted in wheat yield reductions at some locations. Little information is available on the relative performance of wheat cultivars in this system or on the effect of wheat cultivar on performance of the soybean crop. This 2-y study compared performance of relay-intercropped versus sequentially double-cropped wheat and soybean and determined the influence of wheat cultivar on performance of wheat and the succeeding soybean crop. Three wheat cultivars were sown in a relay intercropping pattern (33-cm-wide rows with two 61-cm-wide traffic lanes per 11-row planter pass) and in a conventional double-cropping pattern (18-cm-wide rows). Intercropped soybean was sown between wheat rows 19 (1991) or 27 (1992) days before wheat harvest. Double-cropped soybean was sown in 97-cm rows after wheat harvest. Averaged over cultivars and years, intercropped wheat yield was 18% less than double-cropped wheat due to fewer spikes per unit area. No consistent cultivar by cropping system interaction occurred for wheat yield or yield components. The exception was that, in 1991, ‘Williams’ wheat had similar yields in both cropping systems, but its yields in both systems were very low. In the intercropped system, yields (on an area basis) were less in rows bordering traffic lanes than in interior rows. Double-cropped soybean plants were taller at harvest, but intercropped soybean had longer lower internodes and higher lodging scores. However, relay-intercropped and double-cropped soybean yields were similar, and independent of the previous wheat cultivar.