Effects of crop management practices on Echinochloa crus‐galli and Chenopodium album seed production in a maize/soyabean rotation

Abstract

Seed production of residual weed populations needs to be taken into account when estimating the long‐term impact of low‐input agronomic practices. The objective of this study was to measure the effects and interactions of crop, weed control, tillage practice and nutrient source on the seed production of the dominant residual weed species in a maize/soyabean rotation at two sites: Echinochloa crus‐galli (L.) Beauv. on a Sainte‐Rosalie clay and Chenopodium album L. on a Duravin clay loam. Seed production per unit area was estimated in each experimental unit. Weed seed production was greater under mechanical weed control compared with chemical weed control. In 1997, E. crus‐galli seed production reached over 326 000 seeds m–2 in mechanical weed control treatments, but averaged less than 500 seeds m–2 in the chemical weed control treatments. Chenopodium album produced in the range of 766 000 and 73 000 seeds m–2 in mechanical and chemical weed control treatments respectively. Very few or no weed seeds were produced in soyabean under chemical control. Tillage intensity and nutrient source did not affect seed production of either weed species, with the exception that E. crus‐galli produced more seeds in chisel than in mouldboard plough tillage in soyabean. Weed control method had more impact on seed production than tillage intensity and nutrient source in a maize/soyabean rotation.