YIELD POTENTIAL, AGRONOMIC PERFORMANCE NITROGEN FIXATION AND CLIMATIC ADAPTATION OF DETERMINATE AND INDETERMINATE SOYBEAN CULTIVARS

Abstract

Several experiments were conducted on clay loam soil at Agronomy Farm, NWFP Agricultural University, Peshawar during three consecutive years, to evaluate emergence potential under different planting dates, field conditions and storage containers and to measure the response of determinate and indeterminate soybean (Glycine max (L.) Merrill) cultivars to varying planting dates. Seed emergence consistently decreased from April to June. Emergence decreased when temperature and evaporation increased and relative humidity decreased. Seeding rate did not affect emergence. Emergence increased with seed depth and decreased soil moisture level. Seed moisture content and ambient relative humidity were directly proportional except in refrigerator, tin cans and plastic bags, retaining high moisture content. Germination and emergence consistently decreased with storage time. Maximum reduction occurred in high moisture seeds. Seeds in pods and refrigerator retained maximum germination. Healthy seedlings were proportional to germination and emergence. Field emergence was low but closely related to laboratory germination. Number of days to various vegetative and reproductive stages were reduced with late planting in determinates. In indeterminate number of days to reproductive stages were not affected by planting dates. In Williams reproductive stages initiated earlier than Lee and Essex. The number of days to maturity declined with each successive planting date for all cultivars. The maturity date of Williams was affected more by planting date than was the maturity date of Lee and Essex. In each planting date, leaf area increased, attained a peak and then decreased. Leaf area decreased with late planting and was not enough to produce sufficient seed yield. Leaf area was more in the center and low at the top and bottom of the plant. Williams had a uniform canopy profile compared with Lee and Essex. Nodule number, weight and activity decreased with late planting. In each planting date the number, weight and activity of nodules increased with time, attained a peak and then declined. Declined in activity was greater and sharp than number or weight of nodule. Lee produced greater number of flowers and pods compared to Essex and Williams. In each cultivar more than 80% of flowers, pods and filled pods occurred in two-third periods. Maximum flower and pod abortion occurred in the zone of maximum flower and pod production. Flower abortion was greater than pod abortion. Pods having more seeds were also greater in number. Main stem contributed more than 70% of pods and seeds. Number of pods or seeds were not affected by planting date. Seed weight consistently decreased with late planting and was the major component affecting seed yield. Late planting decreased seed yield and dry matter more than 80%. Cultivars produced equal amount of seed yield. Low 100 seed weight was responsible for low seed yield with late planting. Harvest indices were inconsistent and different for planting dates and cultivars.