Effects Of Rational Fertilizers On Rice Growth,Nutrient Absorption And Loss Risk

In order to improve the nitrogen utilization efficiency(NUE)in double cropping rice,and reduce the nitrogen applications rate and nitrogen and phosphorus loss in rice surface water,a field experiment was conducted in Yiyang,Hunan province.There were six treatments in this experiment:no nitrogen fertilizer(T1),conventional fertilization(T2),20%nitrogen reduction plus boron-silicon fertilizer(T3),organic fertilizer instead of 20%chemical nitrogen(T4),20%nitrogen reduction plus nitrogen fertilizer synergist(T5),and organic fertilizer instead of 20%chemical nitrogen with boron-silicon fertilizer plus fertilizer nitrogen fertilizer synergist(T6).Here,we discussed the effects of chemical N fertilizer,nitrogen fertilizer synergist,organic fertilizer,and silicon fertilizer and boron fertilizer on NUE and N/P loss in double cropping rice.The main results are as follows:1)Compared with conventional fertilization treatment(T2),T3 treatment reduced the yield in early rice,but increased in late rice.Also,T4,T5,T6 treatments had the similar results in double cropping rice yield,and in late rice,the yield increased by 2.02%-4.07%compared with T2 treatment,though the effect was not remarkably.2)Compared with conventional fertilization treatment,nitrogen reduction treatments increased NUE in double-season rice,especially for T3 treatment,which had significantly improved NUE in double-season rice,and increased by 38.01%and 51.01%,in early and late rice respectively.Compared to T2,the N accumulation of overground in T5 treatment had been reduced by 4.69%in early rice and 5.08%in late rice.It is worth mentioning that,there was no significant difference between nitrogen reduction treatments(T3,T4,T5,T6)and conventional fertilization treatment in agronomic efficiency.Compared with conventional fertilization treatment,T3 and T5 treatments can increase the PFP_N in double cropping rice.3)The concentration of total nitrogen,water-soluble total nitrogen,ammonium nitrogen and nitrate nitrogen in the field water increased with the application of common urea,and the nitrogen loss in field water increased at the same time.Compared with conventional fertilization,nitrogen reduction treatments can reduce the nitrogen content in field water and reduce the risk of nitrogen loss.The peak of nitrogen loss take place at one week after nitrogen application,followed by the nitrogen concentration difference shrunken and loss risk reduced.4)In terms of the total phosphorus concentration in surface water of early and late rice,with no nitrogen fertilizer application,P concentration of surface water was lower than other treatments.However,the P concentration of T3 and T5 treatments were higher than that of other treatments,which indicated that with no P reduction application,organic fertilizer replacement and nitrogen fertilizer synergist had little effect on reducing P loss risk in surface water.About 9 days after the application of phosphate fertilizer is the key period of phosphorus loss stage.After that,the phosphorus concentration of each treatment tends to be the consistent,and the changes tends to be stable.The risk of phosphorus loss increases with the increase of phosphorus fertilizer application rate.5)There was no significant difference between 20%nitrogen reduction treatments and conventional fertilization treatment in the photosynthetic rate of the early rice.However,in the late rice,the photosynthetic rate of the 20%nitrogen reduction treatments were increased compared with the conventional treatment,with an average increase of 30.99%.In terms of comprehensive rice yield and photosynthetic rate,the correlation between yield and photosynthetic rate was not obvious.6)With organic fertilizer added,T4 treatment had increased soil organic content compared to the conventional treatment.Meanwhile,while there was no nitrogen fertilizer application,rice plant will increase the consumption of alkali nitrogen in the soil,and T5treatment increased alkaline N by 12.62%and 5.35%in the early and late rice,respectively.However,T3 treatment decreased soil alkaline N and Olsen-P,compared with conventional fertilization treatment.