Impact of improved fallow periods on soil properties and productivity of maize ( Zea mays L.) in major and minor seasons of Asian humid tropics

Abstract

Improved fallows are considered an easy, low cost and suitable method of increasing the productivity and sustainability of smallholder tropical rainfed cropping systems, although most farmers allow weeds to grow when the environmental conditions are not conductive for crop production. Field studies were carried out over the minor and major seasons, to evaluate the impact of a preceding improved fallow using Crotalaria or Tithonia , two popular tropical green manures, on selected soil properties, and on the growth and yield of maize. Improved fallows enhanced chemical soil properties significantly and the impact was most prominent at the onset of the minor maize season. Thus, the growth and yield of maize was also increased to a greater extent in this season, when yields are generally lower due to the suboptimal climatic conditions of lower rainfall and higher temperatures. However, fallows in the minor season also improved soil characteristics and maize yields in the major season, the most significant impact being increased seed yields and harvest indices. Although farmers may not grow fallow crops in major seasons, the potential of these green manure fallows in increasing maize yields in minor seasons and possible strategies to include the fallows in the cropping sequences of tropical rainfed upland cropping systems are discussed on the basis of this field study.