Interactive Effects Of Slow And Controlled Release Fertilizers And Water Management On Yield,Nitrogen Absorption And Utilization Of Rice

Traditional fractional fertilization was mostly used in rice production in China.The high application amout,time-consuming and labor-intensive and low utilization rate caused problems such as environmental pollution.As a new type of fertilizers,slow and controlled release fertilizers reasonably allocated nitrogen and one-time basic application could meet the need of rice for nutrients during the entire growth period,providing a new way for efficient fertilization of rice.In order to clarify the release characteristics of different types of slow and controlled release fertilizers and their practical application effect,the experiment was carried out in the rice experimental base of Nanjing Agricultural University,Yanling Town,Danyang City,Jiangsu Province,from 2018 to 2019.A variety of slow and controlled release fertilizers(humic acid fertilizers,HA;microbial fertilizers,MF;high tower fertilizers,HTF;blending fertilizers,BF;sulfur-coated fertilizers,SCU;and resin-coated fertilizers,PCU)and two water management(intermittent flooding and continuous flooding)were set up,conventional fractional fertilization(CK)and no nitrogen treatment(N0)were used as controls to study the effects of different water managements of slow and controlled release fertilizers on the growth and nitrogen absorption and utilization in rice,to provide the basis for further rational application.The main results were as follows:1.There are differences in nitrogen release characteristics of slow and controlled release fertilizersAccording to the actual nitrogen release rate of slow and controlled release fertilizers,these fertilizers were mainly divided into the following three types.(1)Active fertilizers:Their N release ability was characterized by "explosive release at the early stage and no release at the medium term".Such fertilizers were more susceptible to environmental factors such as moisture and temperature;(2)Slow-release fertilizers:Their N release was categorized by "large amount release in early stage,insufficient nutrient release in middle and later stages";(3)Controlled-release fertilizers:Their N release performance was characterized by "a relatively slower release at the early stage and steady release at the middle and late stages".The duration of the N release period of the three types of fertilizers was controlled-release>slow-release>active.2.Interactions of slow and controlled release fertilizers and water management had significant effects on rice yieldCompared with CK,the rice yield treated with active fertilizers had lower grain number per spike,and the effect on yield was inconsistent for two years;although the slow-release fertilizers were released in the early stage,due to insufficient nitrogen supply in the middle and late growth period,the total spikelets were low,causing yield reduction,but the difference was not significant;the controlled-release fertilizers delayed the peak seedling stage,the dry matter accumulations and the SPAD value were not significantly different compared with CK,and at the same time,due to the continuous release throughout the growth period,grain number per spike,seed setting rate and 1000-kernel weight increased,thus rice yield was improved.Therefore,under the same amount of N in pot,the fertilizer type with stronger supply capacity and longer continuous releasing time was more conducive to material accumulation in the later growth period,increasing the yield.The active fertilizers released nitrogen fast but had a long lasting period.Continuous flooding management in the tillering stage was beneficial to the long-term absorption of nitrogen by roots.In the filling stage,it would affect roots physiological function,active fertilizers were more conducive to the accumulation of dry matter in the early and middle stages under continuous flooding management;There was no significant difference in the rice yield of slow-release fertilizers under two water management;Controlled-release fertilizers promoted soil nitrogen mineralization under intennittent flooding management,which was beneficial to absorb nitrogen in time and improved yield.Therefore,yield under intermittent flooding management was higher than continuous flooding management.3.Interactions of slow and controlled release fertilizers and water management had significant effects on rice nitrogen absorption and utilizationCompared with CK,the nitrogen absorption and nitrogen content of rice treated with active fertilizers were higher,which satisfied the N supply of the peak nitrogen demand of rice,thereby improving the NRF;although the slow-release fertilizers had sufficient release in the early stage,due to the insufficient N supply in the middle and late stages,the N absorbed by the rice at the tillering stage was less than that released by the fertilizers.And N was easily lost through ammonia volatilization,and it was difficult to obtain sufficient N during the panicle initiation stage,thereby reducing the NRF;controlled release fertilizers had fewer in the early stage and more in the late stage releasing characteristics.Although it limited the N absorption of rice at the tillering stage,it relatively improved the N absorption efficiency.At the panicle initiation stage,the N absorption of the rice gradually increased to be significantly higher than other types of fertilizers,and the NRF was higher than other types.Therefore,under the same amount of N in pot,the type of fertilizers with stronger supply capacity and longer continuous releasing time reduced the loss of N when supplied exceeded demand,and improved the NRF.Active fertilizers released nitrogen fast but had a long lasting period.In the tillering stage,the content of NH4+-N was high under continuous flooding increasing the loss of ammonia volatilization,so the NRF of the active fertilizers under intermittent flooding management was higher than that of continuous flooding management;The N release of slow-release fertilizers was concentrated in the early stage and the duration was short,there was no significant difference in the NRF under the two water managements;The NRF of controlled-release fertilizers under intermittent flooding management was higher than that of continuous flooding.Mainly because of the N release performance was characterized by"fewer in the early stage and more in the late stage",rice absorbed nitrogen in a timely manner,reducing the loss of nitrogen through ammonia volatilization when N supply was excessive,thereby improving the recycling rate.Therefore,the NRF under the intermittent flooding management was higher.In conclusion,under the same amount of N in pot,the fertilizer with longer continuous releasing time was conducive to improving yield and N apparent recovery fraction,and the effect of intermittent flooding management was more obvious.