Accumulation of dry matter and nitrogen by minimum-tillage silage maize planted into winter cover crop residues

Abstract

The use of winter cover crops in conjunction with minimum tillage may eliminate or at least mitigate the environmental problems associated with traditional maize tillage. The main goal of the present research was to study the accumulation of nitrogen and dry matter in the tops of silage maize under three cropping systems: (1) PLOUGH (=maize sown into an autumn-ploughed soil), (2) NW/MT (maize sown into frost-killed residues of the non-winterhardy phacelia and white mustard cover crops, and (3) RYE/MT (=maize sown into a stubble of forage rye whose above-ground phytomass was removed from the field shortly before maize planting). The experiments were conducted in the Swiss midlands and in the Jura range. Averaged across the five environments (=site × year combinations) tested, dry matter and nitrogen yields of maize were highest under PLOUGH and lowest under RYE/MT. These differences occurred as early as the 3rd leaf stage and remained until the end of the growing season of maize, but there were significant ( P <0.05) interactions between environment and cropping system. Total yields of dry matter and nitrogen (maize plus rye) of the RYE/MT system tended to be higher than the dry matter and nitrogen yields of maize in the other systems. The effect of method of seedbed preparation (rototilling vs. band rotary hoeing) on the yields of dry matter and nitrogen was not significant; there were no interactions between maize cropping system and manner of seedbed preparation. Under RYE/MT, both the mineral nitrogen content of the soil (0–90 cm depth) prior to maize sowing and the nitrogen concentration in the maize tops throughout the growing season of maize were relatively low, indicating that the rye cover crop reduced the nitrogen supply to the succeeding maize crop through pre-emptive competition.