Abstract
Effects of a foliar spraying of humic substance on growth and yield of soybean were evaluated in Changji (2007, 2008) and Shihezi (2008), Xinjiang, China. The humic substance was applied during the time from the fully expansion of primary leaf to the start of flowering. The humic substance had no significant effect on stem length, node number and branch number, but improved seed yields by 6 to 32%. It increased pod number per plant by increasing pod setting, although there was no significant effect on cumulated flower number. The humic substance did not affect the mean leaf area indices, crop growth rates and net assimilation rates, but increased pod growth rates during the later pod filling period. It also did not affect the CO2 assimilation rate, quantum yield of photosystem II or chlorophyll content. Thus, increasing pod number by plant hormone-like substances in the humic substance was considered to stimulate the translocation of assimilate toward pods, leading to an increase in seed yield. It was concluded that the foliar application of humic substance to soybean was effective in increasing seed yield in the arid areas of Xinjiang, China.
