Quantifying Yield Gaps and Abiotic Stresses in Rain-fed Production Systems of Thailand: Global Theme on Agroecosystems Report no. 45

Quantifying potential yield and yield gap of crops for various growing conditions could provide valuable information for designing strategic crop management plans to increase crop yields. The farmers in the Phu Pha Man district of Khon Kaen province of Thailand commonly grow soybean and peanut under both rainfed and irrigated conditions and cultivate maize under rain-fed conditions. The farmers’ long-term average yields in the district are 1360 kg ha-1 for soybean, 1480 kg ha-1 for peanut and 2810 kg ha-1 for maize. The simulation results, using CSM-CROPGRO models for soybean, peanut and maize, showed that for the Phu Pha Man district, the yield potential of soybean ranged from 1130 to 3700 kg ha-1, maize ranged from 1370 to 7460 kg ha-1 and peanut ranged from 630 to 3880 kg ha-1 under rain-fed conditions. For the fully irrigated conditions in the dry season, the yield potential of soybean ranged from 1870 to 3150 kg ha-1 and peanut ranged from 1840 to 3010 kg ha-1. The yields were generally higher for early planting dates than for later plantings. These results indicated that farmers’ yields under rain-fed conditions in the Phu Pha Man district can be more than doubled with improved management practices. Yield gap analysis for Tad Fa watershed in Phu Pha Man district of Khon Kaen showed that under soil water and nitrogen nonlimiting conditions, the yield potential of soybean ranged from 2810 to 3630 kg ha-1 and for maize, it ranged from 4360 to 6130 kg ha-1. The yield reductions from the yield potential caused by water and nitrogen limitations ranged from 12% to 48% for soybean and 29% to 83% for maize. Low rates of nitrogen application and pests and diseases were the main factors causing yield gaps of soybean and maize in the Phu Pha Man district. Regional analysis of peanut yields showed that northeastern region of Thailand is more productive area for rain-fed conditions, whereas northern region is more suitable to produce peanut under well-irrigated conditions during the dry season