Long and short term effects of tillage systems on grain yield, the incidence of diseases and production costs for maize

The effect of four tillage systems on grain yield of maize, incidence of diseases and production costs was investigated for a Hutton soil in the Natal Midlands from 1982 to 1995. The four tillage systems were no-till (NT), reduced tillage (R, T and R2 T) and conventional tillage (CT). Mean grain yields were not significantly affected by tillage system. Compared with the other systems, NT negatively affected final plant densities, by about 2000 plants ha1. The incidence of ear rot caused by Stenocarpella spp. was not significantly affected by tillage systems, although NT resulted in reduced ear rot incidence in seven out of 13 years. Spraying fungicide for control of grey leaf spot (Cercospora zeae-maydis) improved yields over 100% for NT and in reduced tillage systems during a wet season, compared to 80% increase with CT. During a drier season spraying had no significant effect on grey leaf spot. In the long term, NT was economically more profitable and less risky than the CT system.