Developing Improved Cropping Systems for Vegetables and Legumes in the Tropics

1. Assessment of cropping sequences in terms of yields

Abstract

The project which is aimed at developing adequate cropping systems for vegetables and legumes in the tropics was begun in 1983 and continues up to date. The results obtained were summarized as follows:
Mungbean yield in the spring and autumn plantings became nearly nil in the second cultivation on the same plot because of serious root damage caused by Fusarium oxysporum even if rotated with rice while mungbean yielded fairly high in the summer planting. Introduction of mungbean into cropping systems, therefore, is not recommended, except for summer planting especially in the subtropics. Soybean, on the other hand, is far more tolerant to continuous cropping than mungbean and can be cultivated on the same place without any serious growth retardation for a couple of successive years. Chinese cabbage and tomato should be uprooted when harvested. Their residues retard the growth of successive crops because of its allelopathic effect and introduction of various pathogens into the soils.
Rice straw mulch proved to increase summer tomato yields significantly, but compost application and increased fertilizer exerted no effect on its yield increase. A new heat-tolerant CL 5915-153 tripled the yield of previous heat-tolerant CL 1131-38-4 in the summer planting. It is, therefore, primarily important to avoid hazardous high temperature and heavy rain in the summer planting in terms of introducing highly heat-tolerant cultivars and adequate cultural practices. Cultivars with short duration are also indispensable as a summer component to a successful cropping sequence.
Deep-rooted crops with long duration are not suitable for a successive crops of the spring rice (in rainy season) . Combination of the spring rice and shallow-rooted summer crops with the short duration is acceptable. The deep-rooted crops following summer rice is highly recommendable (in dry season) . Combination of Graminaceous and Leguminaceous crops with long duration, and summer vegetables with short duration is also highly recommendable.
Based on the data collected, recommended cropping systems for vegetables and legumes in the tropics are presented. Acceptability of AVRDC advanced lines of tomato, Chinese cabbage, sweet potato, soybean and mungbean in the cropping system is also discussed.