Crop rotation in the summer rainfall area of South Africa

Abstract

Crop rotation is the successive growing of different crop species on fields with the aim to assist sustainability. Monoculture cropping, the opposite of crop rotation, of maize was and still is the main practice in the summer rainfall area of South Africa. Declining farm profits in the 1980's and increased risk due to the liberalisation of the grain markets in the early 1990's led to renewed interest in crop rotation as a practice for economically sustainable grain production although limited research has been done locally. Results of three field trials done in this area showed no yield advantage of rotated maize and wheat in comparison with monoculture. In seven trials, maize and wheat crop yields were affected, mainly improved by crop rotation. An important benefit of crop rotation in comparison with monoculture cropping is the relative low production risk with or without an increase in nett-return. Possible causes for the effect on yield involve the change in the availability of soil water and nitrogen, pressure from weeds and soil microbial composition, especially diseases affecting the maintenance of a healthy root system. Knowledge on the performance of different crop systems and relative importance of mechanisms involved under various soil, climate and management conditions is lacking and a multidisciplinary approach to future crop rotation research, is needed. © 2005, Taylor & Francis Group, LLC.