Comparison of dry matter production and photosynthetic rate against different planting dates between late and early maturing soybean [Glycine max] cultivars in paddy field

This experiment carried out in a southwestern Korea on a commerce silt loam soil at paddy field. Pungsannamulmong (PSNK), a yellow seed color type, was a relatively high-yielding late maturing cultivar and Nogchaekong (NCK), green seed color type, was a relatively low-yielding early maturing cultivar. Two seeds per hill were sowed with the planting density of 70x10 cm on May 20 and June 20, 2007. Fertilizer was applied prior to planting at a rate of 3.0-3.0-3.4g (N-P-K) per square m by all basal fertilizations. Experimental design was a randomized complete block with three replications. The days from planting to flowering date (R1) and maturing date were longer in PSNK than in NCK on two planting dates. Each seed yield of PSNK planted on May 20 or June 20, which was 282 or 248 g/square m, was higher than that of NCK, which was 244 and 213 g/square m, respectively. Also, the number of pod, number of seed and seed per pod were higher in PSNK than in NCK. The leaf area and top dry matter were higher in PSNK than in NCK, especially, at 60 and 70 days after emergence, respectively. Photosynthetic rate (Psub(N)) at flowering stage (R1), there was no significant difference between cultivars in the uppermost leaf but there was a significant difference in Psub(N) of the 7th leaf on seed development stage (R5).