Reduction of Chemical Application in Soybean at Farm Level : II Comparison between Wet and Dry Seasons Planting

Abstract

                A comparison study was conducted for soybean production in the rainy season at Thongphaphoom district and in the dry season at Nongprue district of Kanchanaburi province in the year of 2001 to 2002. The objective of the study was to seek for the possibility of reducing chemical applications in soybean. Treatments were composed of the chemical and non-chemical control for weed, insect and soil fertility designed as non, less chemical and moderate chemical applications. The given treatments were compared with farmer practices in which various kinds of chemical at different amounts were used in soybean production.

                This study was an on-farm research conducted in the farmer field where the treatments were subjected to the actual conditions of pest, weed and soil heterogeneity. Soybean cultivar “Chakkrabhandhu no.1” was grown in the upland soil on 20 July 2001 in the rainy season trial while the same variety was planted in the paddy field after rice in the dry season on 20 December 2001. Results of the experiments revealed that the yield of soybean crop grown in the wet season was lower than those of the dry season. The main factor reducing yield in both trials were weed infestation. Weed growth in the rainy season was mainly broadleaves while in the dry season the main weed infestation was volunteer rice. In both trials, insect infestation were mild, therefore, the use of neem extract seemed enough for controlling insect pests in soybean fields.

                In both experiments, it was found that the application of triple super phosphate (TSP) at 62.5 kg/ha increased the yield of soybean to the highest level among other treatments. While the biophoska organic fertilizer raised the yield to the second highest level in both trials. It can be concluded in this study that for growing soybean successfully in the rainy season, post emergence herbicides such as Formezafen plus Fluazifop-p-butyl and the application of triple super phosphate were needed. However, to grow soybean successfully in the dry season, the triple super phosphate or biophoska alone was sufficient for increasing yield of soybean grown after rice.