Improved fallow management
1996
Anan Pintarak | Wijarn Juntorn (Maejo Univ., Chiang Mai (Thailand). Soil Fertility Conservation Project)
Traditional fallow cycle is shortening due to increasing land pressure. This is forcing farmers to abandon the long fallow periods which are essential for soil regeneration and weed control. Two on-station experiments which were set up to select suitable leguminous cover crops for improved fallow management in traditional cultivation systems with reduced fallow periods, were conducted at the Royal Mae Sa Mai Station at Amphur Mae Rim, Chiang Mai at an altitude of 800 m asl. In the first experiment, seven species of leguminous cover crops, i.e. Cajanus cajan (pigeon pea), Crotalaria juncea (sun hemp), Psophocarpus tetragonolobus (winged bean), Vigna unguiculata (local black bean), Lablab purpureus (lablab bean), Canavalia ensiformis (jack bean and Vigna umbellata (rice bean) were compared with the traditional fallow which was dominated by grasses. The legumes being tested clearly showed different growth characteristics. Only the black bean could give 100 percent cover at 56 DAS. The influence of the cover crops on the N soil content at 8 MAS to 18 MAS was positive. Yields of a following upland rice crop were higher than the control for all the improved fallow treatments with black bean showing the best results. In the second experiment, four legume species were selected. The treatments included intercropping of deep-rooting legumes, pigeon pea and tephrosia, with shallow rooting legumes, black bean (cowpea) and rice bean, as a potential for a two year-improved fallow. During the first year, seed yield of rice bean was not affected by inter-cropping with deep rooting legumes whereas black bean seed yield was reduced. Dry matter content of pigeon pea mono-crop was higher than that of a tephrosia monocrop.
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