Effects of irrigation during different growing periods on three soybean cultivars in silty clay loam (Ratchaburi Series) soil
1996
Wanchai Thanomsub | Somchai Boonpradub | Santi Promkum | Anat Watanasit | Somyot Pichiporn | Thewa Maolanont (Department of Agriculture, Bangkok (Thailand). Field Crops Research Inst. Chainat Field Crops Research Center)
Irrigation frequency directly influences variable costs of soybean production. Reduction in the number of irrigation can be done by delaying irrigation during growing stages. Responses of 3 soybean cultivars differing in maturity to initiation of irrigation were investigated in a silty clay loam soil between Dec. 1995 and Mar. 1996 at Chai Nat Field Crops Research Center. The number of irrigation throughout the season was between 3 and 6, and total amounts of water applications were between 124 and 237 mm, depending up on initiation of irrigation and cultivars used. Three soybean cultivars responded similarly to initiation of irrigation. LAI, LAD an4 CGR reduced with delaying irrigation. Full irrigation produced the highest yield (342 kg/rai), whereas initiation of irrigation at V4, R1 and R3 stages gave 12, 33 and 44 percent smaller yields. Reduction in the number of pods/plant and seed size were the main factors causing smaller yields of beginning irrigation at V4, R1 and R3. Three soybean cultivars gave no significant difference in yield, although their maturity was different. No significant differences in yields among cultivars resulted from compensation in yield components between cultivars. NS1 produced the greatest seed size, whereas SJ5 and ST2 compensated by having higher number of pods/plant and seeds/pod, respectively.
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