Thesis Abstract of AGS Students

Assessing Nitrogen Fertilizer Management For Red Kidney Bean (Phaseolus vulgaris L.) in Highland

Budsara Limnirankul (1997)

This study commenced with a field survey undertaken in 9 villages (Pa Bong Mai, Pa Bong Kao, Mae Kan, Huay Luk, Chiya 1, Chiya 2, Chiya 3, Chiya 5 and Chiya 6) with the aim to understand red kidney bean production system, fertilizer management and cost-benefit of red kidney bean. In additional, average farm yield in early and late rainy seasons was estimated by crop cut method taken from 1 m² sample.

A field experiment was designed to investigate fertilizer management and rhizobium inoculation affecting seed yield and to evaluate the effect of time and rate of fertilizer application on red kidney bean yield. These were carried out on sandy loam soil, with total nitrogen of 0.076 percent and pH 4.9 at the Royal Project site, Ban Kae Noi in Muang Na sub-district, Chiang Dao district of Chiang Mai province. The factorial experiment consisting of rhizobium inoculation and nitrogen application was designed with eight treatment combinations and four replications. Two levels of rhizobium (Rhizobium legumeminosarum bv. phaseoli), with and without inoculation, and four levels of nitrogen applications were applied on red kidney bean Kae Noi variety. Urea was used as nitrogen source.

The results from the field experiment showed that rhizobium inoculation had no significant effect on the dry matter accumulation and total N uptake. But the total dry matter production at flowering (R₁ = first flowering, R₂ = blooming) and at physiological maturity (R₇) was significantly affected by chemical fertilizer application in both seasons. The bean receiving twice fertilizer applications produced highest total dry matter production in September planting.

Furthermore the fertilizer treatments did show significant effect on total N uptake at R₇ in both planting dates. The total N uptake increased with increased fertilizer input, giving the highest amounts of N uptake at R₇ stage of 113 kg ha^-1 in May planting and 100 kg ha^-1 in September planting when two applications of fertilizer (F₃) were used.

The nitrogen fixation as determined by the relative abundance of ureide in xylem sap showed that at 49 days after planting (DAP), the application of fertilizer at 7 DAP (F₁) or at 7 and 30 DAP (F₃) had significantly suppressed the fixation ability of rhizobium. But when the fertilizer was applied once at 30 DAP (F₂), the RUI-N% was significantly higher, averaging 61.4 percent which was comparable to non-fertilizer treatment of 59.7 percent.

The nitrogen fertilizer had significantly affected seed yield, with the highest yield of 1546 kg ha^-1 was obtained from the two applications of fertilizer in the September planting, while the other three treatments of no application and once application averaged 1244 kg ha^-1. The cost benefit analysis from the experiment found that R₀F₀ and R₀F₃ gave the highest returns in the May and September plantings respectively.

The results from the field survey indicated that red kidney bean production was capital and labour intensive. But farmers were able to cope with high input cost through the use of their own seed suppy and family or/ and exchange labor which contributing 80 percent of the total variable cost as non-cash. The red kidney bean could provide an annual income of 5864 to 6543 baht per household.

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