Study On Fertilizer Reduction Technique Based On Straw Composts And Fertigation System

Over-fertilization has been a problem for agricultural production in China for a long time,which may cause agricultural non-point source pollution.The application of straw composts can not only reduce chemical fertilizer but also improve physico-chemical properties of soil.Composite inoculants have strong adaptability and complete enzyme system.So they usually perform better than single strain inoculants under high-temperature and complex circumstance.Fulvic acid potassium（FA-K）is a kind of water-soluble organic fertilizer,and it is combined with nutrient elements.The slow-release effect of FA-K makes it provide nutrition support for a long time.Fertigation system is recognized as an effective water and fertilizer saving technology,and has been utilized in many countries.Therefore,this research screens an composite inoculant.It confirms that dropping FA-K by fertigation system can improve the soil nitrogen-conserving ability,which benefits for cucumber growth.Then,the straw compost is used as base fertilizer,chemical fertilizer and FA-K are dropped by fertigation system during the growth period.The pathway of chemical fertilizer reduction and its effects on cucumber yield and quality are discussed.The main results are summarized as follows.（1）Based on the isolated 15 effective cellulose degrading bacteria in the laboratory,the composite inoculant（JFB-1）which can effectively degrade crop straw was screened.Result shows that JFB-1 can shorten for 1-2 d for one period,2-4 d in total.The organic matter content is 403.5-515.1 g·kg^-1 and the ratio of C/N is reduced to 10.53-15.30.As a whole,the effect of rice straw composts are better than asparagus stalks composts for the same application.For example,when the application is set at 150 g·kg^-1,the soil organic matter content and total N are increased by 33.5% and 7.3%,the urease and cellulase activities are increased by 16.7% and 30.8% respectively.It can improve the soil microbial diversity.Shannon index,Simpson index and McIntosh index are increased by 56.0%,77.7% and 72.9% respectively.The biomass of cabbage is raised by 46.4% when it has been cultivated for 30 d by JFB-1 rise straw compost.（2）Planting cucumbers with FA-K dropped by fertigation system.Monitoring the change of soil NO₃^--N and NH₄⁺-N,the results shows that it needs to raise the soil NH₄⁺-N before florescence and raise the soil NO₃^--N after fruiting period for precision fertilization.Detecting the soil total N content,it shows that FA-K can improve the soil nitrogen capacity.FA-K dropped by fertigation system can reduce the soil nitrification and prevent the secondary salinization,and it can inhibit the activity of nitrate reductase which is facultative anaerobic enzyme.It verifies that FA-K dropped by fertigation system can improve the properties of soil and reduce the loss of N.Furthermore,it can reduce the greenhouse gas emission and agricultural non-point source pollutant.For nitrification,FA-K act the opposite role for AOA and AOB,it can improve the abundance of AOB but reduce the abundance of AOA.For denitrification,nirS gene is more sensitive to fertilizer application level,FA-K has no significant effect on nirS and nirK.（3）When the application of fertilizer is one half of farmer habit（CK）,exactly the N is 209.1 kg·hm^-2,P2O5 is 166.2 kg·hm^-2,K2 O is 256.2 kg·hm^-2 and the FA-K is 225kg·hm^-2,the yield is increased by 37.0% to the same application level but FA-K（H0）and10.8% to CK.The height,stem diameter and chlorophyll content in leaf are more than CK,which verifies that F（4）The Alternative experiment shows that the optimal yield and quality of cucumber fruits when the application of nitrogen fertilizer is 0.263 g·kg^-1,straw compost is 75 g·kg^-1 and FA-K is 0.28 g·kg^-1.Fertilizer reduction is 50% at that time.When the application of FA-K is set to some fixed value,the Vc content of fruits would be promoted by low-concentration of chemical fertilization and compost,but it would be inhibited by high-concentration of them.The content of soluble sugar in cucumber fruits and the application of FA-K are positively correlated.The application of chemical fertilizer and straw compost positively related to the NO₃^--N content of fruits.And the contribution of chemical fertilizer is far beyond to straw compost.