Effect of adding humic acid to phosphorous fertilizer on maize yield and phosphorus uptake and soil available phosphorus content

Objectives Humic acid has been proved to be able to improve the use efficiency of phosphorous fertilizers. Research on the appropriate addition dosage will provide scientific way in reducing application rates of P2O5 through the synergistic effect of humic acid.Methods Four kinds of humic acid P fertilizer (HP1, HP2, HP3 and HP4) were made by adding different proportions of HA (the added proportions were 1%, 5%, 10% and 20%, respectively) to mono-ammonium phosphate(P). A soil column experiment was conducted to investigate the effects of HP on maize yield, phosphorus uptake, P fertilizer use efficiency and the content of soil available phosphorus under the same P2O5 application rate and the reduction of P2O5 application rates (P2O5 application rates were decreased by 1%, 5%, 10% and 20%, respectively).Results 1) Compared with the normal P treatment, the grain yields of the HPs were significantly increased by 4.5% to 13.6% with the increase of added proportion of HA under the same P2O5 application rate. The reduction of the P2O5 application rate can lead to the decrease of the grain yields, but there was no significant decrease while the P2O5 application rate was reduced by 20%. 2) The grain phosphorus uptakes and aboveground phosphorus uptakes of the HPs were significantly increased by 6.0% to 15.4% and 6.3% to 14.0% compared to the normal P treatment under the same P2O5 application rate, but there were significant differences when the P2O5 application rate was reduced by 20%. 3) The phosphate apparent efficiencies of the HPs were increased by percentage points of 5.9 to 13.1, and the agronomic efficiencies and partial factor productivities were increased by 26.5%-79.1% and 4.5%-13.5% under the same P2O5 application rate. 4) Compared with the normal P treatment, humic acid mainly affected the soil available phosphorus contents in 0-50 cm soil layer. In particular, the soil available phosphorus contents of the HPs in 15-30 cm soil layer were increased by 18.1% to 36.6%.Conclusions Addition of humic acid shows satisfactory role in improving maize yield, phosphorus uptake and utilization, and increasing the soil available phosphorus contents under the same phosphorus input rate (P2O5 0.1 g/kg soil). P2O5 application rate can be reduced by about 20% through the synergistic effect of humic acid without affecting the yield.