Thesis Abstract of AGS Students

Management of leucaena hedgerows and tillage in maize-red kidney bean system

Sakda Sukviboon (1996)

Northern region of Thailand covers an area of about 170,000 km2, large part of which are the watersheds of the major rivers. An increasing land use pressure on the upland and highland have accelerated the conversion of the forest land into cultivated area particularly on the steep terrian. This practice usually leads to serious soil erosion and depletion of soil productivity.

Promotion of alley cropping and soil conservation among farmers in northern Thailand have been focused on leucaena hedgerows. Effective management of the alley cropping involves how to prune, when and how often to prune. These questions need to be assessed on-farm.

The study was conducted in Ban Huay Cha Kharn Village which locates in Chiang Dao district, Chiang Mai. Initially, informal and formal surveys were conducted to describe farmers' circumstances. Subsequently, the on-farm experiment was conducted with an emphasis on inves-tigating the effects of frequencies of pruning and types of tillage in the maize-red kidney bean and leucaena alley cropping. The treatments were arranged as a split-plot design with two levels of tillage as main plots and three pruning frequencies as subplots. The yield of maize was highly significant different among various frequencies of prunings whereas the red kidney bean yield was not significantly different. The total dry matter of maize-red kidney bean system was not significantly different among the treatments. Average dry matter of biomass of leucaena obtained from two pruning, three pruning, and four pruning methods were 11.78, 12.19, and 12.64 t/ha respectively whereas the monthly pruning provided a total dry matter of 19.20 t/ha. The average biomass gained as residue in the soil from two, three and four prunings were 15.66, 16.39, and 16.98 t/ha respectively.

The total soil loss computed by the Universal Soil Loss Equation (USLE) model was highly significant diffeent among different types of tillage and levels of pruning. The estimated soil loss from two prunings, three prunings, and four prunings methods were 56.9 t/ha/y (0.49 cm/y), 54.4 t/ha/y (0.47 cm/y), and 55.3 t/ha/y (0.48 cm/y) respectively. The average soil loss from minimum tillage and tillage methods were 55.0 t/ha/y (0.48 cm/y) and 56.0 t/ha/y (0.49 cm/y) respectively. The estimated soil loss from traditional cultivation in the farmer's field was 141.7 t/ha/y (1.23 cm/y). However, the total top soil movement measured by staking technique was not significantly different among the treatments for maize-red kidney bean system.

The results also suggested that the labour requirement under the studied conditions for the maize-red kidney bean system were high in every treatment. This ranged from 200 to 237 man-days/ha in the experimental plots whereas the traditional farming required only 202 mandays/ha. However, labour requirement may be provided mostly by the family labour.

The MT-2P treatment utilized the least manpowers of 200 mandays/ha and provided the highest net returns. Although soil erosion from the MT-2P treatment estimated by the USLE model was slightly higher than that from the MT-4P method but the annual rate of soil loss was about 50% of that estimated from the traditional farming plots. Therefore, the minimum tillage and alley cropping with the two prunings of leucaena hedgerows was more effective than the other treatments in this study to be used as a mean to maintain productivity of maize-red kidney bean system.

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