Effect of Phosphite Fertilizer on Yield and Growth in Soybean

Abstract

To evaluate whether phosphite fertilization contributes to enhancement of soybean yield, we investigated the effects of phosphite fertilizer on yield, yield components, growth, and dry matter production of soybean (cv. ‘Oosuzu’). In 2021, to assess the effects of application concentration, we established 100× and 500× plots, in which phosphite fertilizer was sprayed at 100- and 500-fold dilutions, respectively. In 2022 and 2023, to assess the effects of the timing of application, we established early and late plots, in which phosphite fertilizer was applied at the R1 (beginning of flowering) and R5 (beginning of seeding) stages. In 2021, we detected an increase in total grain weight in response to the application of a 100-fold dilution of phosphite fertilizer, and in 2023, we found that the winnowed grain weight increased in both the early (R1) and late (R5) fertilized plots and total grain weight in the late (R5) fertilized plot. These findings revealed that the foliar application of phosphite fertilizer promotes the yield of soybean. This increase in yield can be attributed to an increase in the number of pods, whereas we observed no significant effects of phosphite fertilization on aboveground dry matter weight or SPAD during the growth period. It is accordingly suggested that the application of phosphite fertilizer during the reproductive growth period from R1 to R5 contributes to enhancement in the sink capacity, rather than source capacity, of soybeans, thereby leading to an increase in the number of pods, and hence an increase in yield.