Productivity and nitrogen use of maize as affected by in situ and ex situ green manuring in major and minor seasons of tropical Asia

Abstract

Green manuring is considered an important agronomic practice for smallholder farming systems in the tropics. Different species of legumes and non-legumes are applied either asex situorin situgreen manures. Thus a field study conducted under rainfed conditions in Sri Lanka compared the effect ofin situandex situgreen manuring using two popular green manures (Crotolaria juncea— a legume andTithonia diversifolia— a non-legume) on the growth, seed yield and N use pattern of maize (Zea mays), the most popular upland cereal in the Asian tropics, grown with high and low N rates, in the two seasons that correspond to the monsoonal rains.In situgreen manuring, especially with crotolaria, increased the growth, seed yield and N use efficiency of maize when compared to theex situaddition of similar quantities of the green manure. The impact was also greater in the minor season, when the crop was subjected to moisture stress conditions. The benefits ofin situgreen manuring with tithonia were lower than those due to crotolaria.In situgreen manuring with tithonia also led to a greater increase in growth, seed yield and N use efficiency in maize compared toex situgreen manuring with this species. The green manures, especiallyin situapplication, also increased the benefits of enhanced rates of N fertilizer to the crops in both seasons, with greater use efficiency in the major season. The study showed the benefits of green manuring (bothinandex situ) for obtaining higher yields of maize in the growing seasons of the Asian tropics, especially thein situapplication of legume species.