Effects of Foliar Application of Humic Substance on Growth and Yield of Soybean in Arid Areas of Xinjiang, China
Yousuke MIYAUCHI1), Akihiro ISODA1), Zhiyuan LI2) and Peiwu WANG2)
(1)Graduate school of Horticulture, Chiba University, Matsudo 648, Matsudo city, Chiba 271-8510, Japan; 2)Urumqi Agricultural and Environmental Institute for Arid Areas in Central Asia, Urumqi, Xinjiang, China)

Abstract: Effects of a humic substance by foliar spraying on growth and yield of soybean were evaluated in Changji (2007, 2008) and Shihezi (2008), Xinjiang, China. The humic substance was applied at the period from the fully expansion of primary leaf to the start of flowering. No significant effect of the humic substance was observed for stem length, nod number and branch number. Seed yields, however, were improved by the application of humic substance by 13 to 32%. Pod number per plant increased by the application of humic substance due to increasing pod setting, although there was no significant effect on the cumulated flower number. There was a positive effect of the humic substance not on mean leaf area indices, crop growth rates and net assimilation rates, but on pod growth rates during the later pod filling period. CO2 assimilation rates, chlorophyll contents and quantum yields of photosystem II were not affected by the application of humic substance. It was therefore assumed that increasing pod setting by plant hormone like substances in the humic substance would stimulate assimilation of carbohydrates toward pods, leading to an increase in seed yield. It was concluded that the foliar application of humic substance on soybean was effective for seed yield increase in the arid areas of Xinjiang, China.
Key words: Arid area, Flower number, Humic substance, Pod setting, Seed yield, Soybean.