Study On Matrix-Based (Humic Acid) SRNFs And Their Sweet Potato Biological And Rhizosphere Soil Environmental Effects

1 Preparation of matrix-based slow release fertilizers and Screening substrates of fertilizersIn this experiment, ten types of matrix-based SRFs were prepared, and their nitrogen release characteristics were studied by alternate leaching method of sand media. The results showed that the dynamics of accumulated release rate of matrix-based fertilizer nitrogen could be quantitatively described by four equations: the first-order kinetics equation(Y=a(1-e-bx)), Elovich equation(Y=a+blnx), parabola equation(Y/k=a+bx0.5) and Logistic equation(Y=k/(1+ae-bx)). However, the imitation of Logistic equation was the best for describing the accumulated release rate(r=0.98561**~0.99926**). So the Logistic equation was the most practical for imitating nitrogen release mechanism of matrix-based fertilizers. The slow releasing effects of ten were studied through the parameters of Logistic equation and UPGMA cluster analysis of nitrogen releasing inflection point, the results showed that oxidized starch, lignin and airslake coal were the best slow releasing substrates in the organic substrates and bentonite was the best slow releasing substrates in the inorganic substrates.After taking the price, their biological and soil environmental effects into account, the airslake coal, which is rich of humic acid, was used to prepare matrixed-based SRFs.2 Preparation of humic acid slow release fertilizer study on nitrogen release mechanismThe best condition of preparing AHA through KOH was filtrated by complete experiment design. The results showed that, when KOH solution of 20% mixed with airslake-coal of 3 times, the production had the best chemical properties and the produce cost was cheaper. And then, three types of HA-SRNFs were prepared by AHA. Their nitrogen release characteristics were studied by leaching method of sand media. The results showed that dynamics of accumulated release rate of HA-SRNFs could be quantitatively described by Logistic equation(Y=k/(1+ae-bx)) (r=0.99581**~0.99989**). The maximum of accumulated release rate of HA-SRNFs nitrogen was studied by comparing the parameters of Logistic equation, and its sequence was HA-NO3>HA-CO(NH2)2>HA-NH4. The slow releasing effects of HA-SRNFs of same diameter were studied through the characteristic of nitrogen releasing inflection point, and its sequence was HA-NO3>HA-NH4>HA-CO(NH2)2. What's more, if the diameter of fertilizer granule was bigger, the slow release effects of HA-SRNFs of same form were better.3 Effects of HA-SRFs of different forms on formation of yield and quality of sweet potatoThe effects of HA-SRNFs on yield, quality, dry matter accumulation and distribution, photosynthetic characteristics of functional leaves, assimilation and utilization of mineral elements, root activity and key enzyme activity of functional leaves involved in nitrogen metabolism of edible-type sweet potato Beijing553 were studied by pool culture and micro plot of 15N trail. Compared with ANFs of same time, HA-SRNFs could increase the yield, the content of sucrose and soluble sugar of storage root, dry matter accumulation of storage root by heightening the inflection point rate, dry matter accumulation of plant by advancing the inflection point time and heightening the inflection point rate, GS activity, LAI, root activity, accumulation of N, P and K, distributive proportion of N in leaf, P in leaf and strorage root, K in strorage root. HA-SRNFs could reduce the starch content of storage root, distributive proportion of N in storage root, stem and leafstalk, P in stem and leafstalk, K in leaf, stem and leafstalk. What's more, HA-SRNFs could increase the utilized efficiency, soil remnant ratio, proportion of NDFF, distributive proportion of fertilizer N in strorage root and reduce the loss ratio, distributive proportion of fertilizer N in leaf, stem and leafstalk. Compared with HA- CO(NH2)2 and HA-NO3, HA-NH4 could increase the yield, soluble sugar of storage root, dry matter accumulation of storage root and plant, distributive proportion of dry matter into storage root, LAI, content of chlorophyll a and a+b, GS activity and photosynthetic rate of functional leaves, root activity, accumulation of P and K, distributive proportion of N in leafstalk, P in leaf and strorage root, K in strorage root and leafstalk and reduce content of starch and protein. What's more, HA-NH4 could reduce content of starch and protien utilized efficiency, soil remnant ratio, proportion of NDFF, distributive proportion of fertilizer N in strorage root and reduce the loss ratio.4 Effects of HA-SRFs of different forms on rhizosphere soil environment of sweet potatoThe effects of HA-SRNFs on physical properties of tillage soil, nutrient content and biological characteristics of rhizosphere soil were studied by a pool culture trail. Compared with ANFs of same form, HA-SRNFs could reduce the bulk density and qCO2 and could increase the non-capillary porosity, the total porosity, urease activity, microbial biomass C, qMB, respiration rate and the content of organic matter, alkali-hydrolysable nitrogen, available phosphorus. Compared with HA-CO(NH2)2 and HA-NO3, HA-NH4 could increase the microbial biomass C, qMB and the content of organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus and could reduce qCO2.