Thesis Abstract of AGS Students

Effects of input level on soybean yield in Chiang Mai valley

Morakot Augsornsward (1988)

There were two steps in this study of effects of input levels on soybean yield in the Chiang Mai Valley in the crop year 1985/1986.

Step 1: To identify target area for the study provincial secondary data were analyzed. From the study it was found that Amphoe Hang-Dong (District) in the Mae Taeng Irrigation Project of Changwat Chiang Mai (Province) has the highest density of farmers per agricultural area, growing soybean after rice and was selected for conducting on-farm research experiment. A crop cutting survey was carried out in dry season 1984/1985. Actual farm yield of soybean was generally much lower than the maximum yield obtained in experimental stations. From random sampling of soybean yields of 41 farmers plot in 5 Tambon (Subdistrict) average yield was only 228 kg/rai. Inputs used by farmers were farmyard manure, chemical fertilizer grade 16-20-0, foliar nutrients and insecti-cides. Most of the farmers were very well aware that weeds were the main problem in decreasing soybean yield. But only 7.3% of the farmers in the studied are practiced proper weed manage-ment because of labor shortages. They said they would try herbicides only if it is known to be very effective.

Step 2:This part of the study was aimed to test 6 input levels and the farmers' practices. The treatments include: (1) control (2) rhizobium (3) rhizobium + foliar nutrient (4) rhizobium + foliar nutrient + herbicide (5) rhizobium + foliar nutrient + herbicide + fertilizer rate 1.5-4.5-3 (N-P₂O₅-K₂O) kg/rai (6) rhizobium + foliar nutrient + herbicide + fertilizer rate 3-9-6 (N-P₂O₅-K₂O) kg/rai (7) farmers' practices. The results showed that soybean yield was increased, with increased input level except for control and only rhizobium inoculation, which were shown to be statistically nonsignificant. It was also found that the treatment of rhizobium + foliar nutrient + herbicide + fertilizer rate 3-9-6 (N-P₂O₅-K₂O) kg/rai (= full package), gave the highest yield of 387 kg/rai. The lowest yield on the control treatment was 265 kg/rai and farmers' practices yielded 325 kg/rai. Taken current price of soybean at 6.50 baht/kg, the maximum net return was 956.90 baht/rai when rhizobium + foliar nutrient + herbicide were applied. The minimum net return was 745.60 baht/rai in the control treatment, whereas farmers' practices gave only 765.55 baht/ rai. From the marginal rate of return analysis (MRR), treatment that gave the highest MRR was rhizobium + foliar nutrient + herbicide, followed by rhizobium only and rhizobium + foliar nutrient in that order. The lowest cost of production was obtained with the rhizobium + foliar nutrient + herbicide treatment at 3.63 baht/kg, compare with the farmers' practices at 4.25 baht/kg.

In conclusion, this treatment of rhizobium + foliar nutrient + herbicide is most suitable because the cost of production is considerably lower than that spent on farmers' own practice while giving much higher return.

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