| Low recovery rate of chemical nitrogen,and low reuse rates of nutrient resources in livestock and poultry waste have become serious problems in agriculture of our country.This study aimed to promote the cycle of nutrients in organic manure and increase nitrogen use efficiency,an optimized MAP method with a new solid precipitant was used to study the simultaneous recovery of nitrogen and phosphorus in piggery wastewater and organic matter.The dynamic changes of soil available nitrogen and the chemical fertilizer utilization efficiency as affected by integrated fertilization with organic manure and inorganic fertilizer were studied through field and 15N micro-plot experiments.The long-term experiments were conducted to investigate the effects of organic-inorganic fertilizers application and dual impacts of long-term organic manuring on the biochemical mechanism of soil organic matter transformation process and soil ecological environment quality.A method for screening copper tolerant rice(Oryza sativa L.)cultivars based on hydroponic experiments and cluster analysis was studied.The results were as follows:1.Based on the MAP method,the addition of a new type of solid precipitant combined with the appropriate molar ratio of reactive materials could effectively simultaneously recover nitrogen,phosphorus and organic matter from the pig farm wastewater.In the tested wastewater conditions,the appropriate molar ratio of reactive materials such as solid precipitant,magnesium chloride(MgCl2),disodium phosphate(Na2HPO4),ammonium(NH4+)was 0.6:0.6:0.6:1,and upon that the simultaneous recovery of nitrogen,phosphorus and organic compounds in wastewater was achieved for that the recoveries of total nitrogen,total phosphorus and organic matter were 91.8%,99.6%and 81.6%,respectively.The N,P2O5,and organic matter contents of the recovered material were 7.85%,25.05%and 23.10%,respectively,and met the total nutrient content requirements of the quality criterion of organic-inorganic compound fertilizer(GB 18877-2009).The total N release amount and ratio of recovered material in the soil column leaching test was significantly lower than that of commercial organic fertilizer under the same N dose condition,for the reason that the recovered material is a new type of organic-inorganic nitrogen-phosphorus compound fertilizer with sustained-release properties.The results of simulation experiment showed that the integrated application of recovered material fertilizer and urea significantly reduced the rate of ammonia volatilization and accumulated ammonia volatilization amount compared with single application of urea under the same nitrogen dose condition.The greenhouse pot experiment showed that and significantly increased the biomass of ryegrass,N,P and K uptake amounts and apparent utilization rates of nitrogen and phosphorus compared with complete chemical fertilizers under the same nutrient doses condition.2.Results of the field experiment under the double rice cropping system showd that there was no significant difference in the soil soluble ammonium,nitrate and total nitrogen concentrations between the integrated fertilization with organic-inorganic fertilizers treatments and farmer practice treatment(FP)during most growth stages of early and late rice.There was no significant difference in exchangeable ammonium nitrogen concentration between organic-inorganic fertilizations and FP,so was the alkali-hydrolyzable nitrogen(Ah-N)of CM(N)and FP during the early and late rice seasons,and the soil Ah-N concentration of FP was significantly higher than that of control(CK).In most growth stages of early and late rice,there was no significant difference in MBC,MBN,urease and sucrase activities between CM(N)and FP during most growth stages of early and late rice.The results showed that under the same nutrient doses applied,integrated fertilization with organic and inorganic fertilizers could ensure the supply of soil effective nitrogen and maintain the soil biological activities.Partial replacement of chemical fertilizers with organic manure is feasible.3.Results of the field experiment under the double rice cropping system showd that rice yields of FP,CM(N)and CM(-N)were significantly higher than those of the other treatments under the double rice cropping system.Using 20%organic nitrogen instead of urea nitrogen[CM(N)]increased the utilization rate of chemical nitrogen fertilizer and achieved similar rice yield as FP at the same time.The utilization rate of chemical nitrogen fertilizer of CM(-N)was significantly higher than those of FP and CM(N),but rice yield of CM(-N)was significantly lower than that of FP.From the view of annual rice yield,treatment FP achieved the highest rice yield,followed by CM(N)and CM(-N)with 6.1%and 10%higher chemical nitrogen utilization rate than of FP,respectively.The results showed that replacing 20%of chemical nitrogen with organic nitrogen could not only maintain rice yield,but also improve the nitrogen fertilizer utilization rate,and the grain was fuller,which was conducive to improving quality.4.The results of 15N double micro-plots experiment indicated that under the same nutrient does applied,shoot biomass of integrated fertilization was higher than FP,and the grain yields had no significant difference,The chemical fertilizer nitrogen recovery rates of integrated fertilizations were 37.1%and 37.9%for early rice,36.8%and 36.2%for late rice respectively.Both of them were significantly higher than those of FP.The recoveries for the whole year were 37.6%and 37.7%respectively,which were significantly higher than those of FP(31.5%).The integrated fertilization significantly increased the cumulative nitrogen recovery rates and significantly reduced the nitrogen loss rates.The recovery rates of early rice season residual chemical fertilizer nitrogen in follow-up late rice season under integrated fertilizations were 10.5%and 11.3%respectively and were significantly higher than that of FP(8.9%).The recovery rates of fomer year residual chemical fertilizer nitrogen in follow-up early rice season under integrated fertilizations were 7.9%and 11.2%respectively and were significantly higher than that of FP(6.1%).The integrated fertilization with organic manure and chemical fertilizers significantly increased the recovery rates of both seasonally applied and residual chemical fertilizer nitrogens in early and late rice seasons.5.Eightteen paddy soil samples were collected from a 30-year field experiment with six different fertilization treatments.The analytical results showd that under the same nutrient doses applied,integreated fertilization was better than chemical fertilizers,and available phosphorus and organic carbon were significantly increased.The addition of organic manure significantly increased the concentrations of soil total nitrogen,total phosphorus and organic carbon as well as available nitrogen,available phosphorus and available potassium.Integrated fertilization increased microbial biomass carbon(MBC),enhanced soil basal respiration and cumulative carbon mineralization compared to chemical fertilization alone at the same nutrient doses.The activities of soil protease(Pro),?-glucosidase(?G),N-acetyl-glucosaminidase(NAG)and acid phosphatase(AP)from the integrated fertilization treatments were significantly higher than those of the treatments without organic manure,so did the activities of soil leucyl aminopeptidase(LAP)and urease(Ure)from the treatment with organic manure in addition to farmer practise fertilization(NPKM2).The stoichiometric ratios,expressed as ln?G:ln(NAG+LAP):lnPro:lnUre:lnAP,ranged from 1:0.94:1.04:0.67:1.01 to 1:0.98:1.10:0.78:1.25,indicating that the acquisition of C,N and P changed consistently and synchronously under different nutrient management strategies.We concluded that protease and urease should be considered in eco-enzymatic stoichiometric assessments for the hydrolysis of proteins,amino acids,carbohydrates and phosphomonoesters in soil,and integrated fertilization with chemical fertilizers and organic manure should be recommended as a preferable nutrient management system for intensive rice cultivation.6.Twelve soil samples were collected from a 9-years field experiment with four pig manure rates.The analytical results showd that long-term application of organic fertilizer(4800 kg/ha)significantly increased soil nutrient concentrations and pH value,promoted phosphatase activity and accelerated mineralization of organic phosphorus.Soil enzyme activities and microbial biomass were significantly correlated with soil physical and chemical properties.Soil urease,protease,?G,NAG,LAP activities,microbial biomass carbon(MBC)and mineralization of carbon(Cmin)were significantly positively correlated with soil organic carbon(SOC).The application of organic manure significantly increased the concentrations of Cu and Zn in soils and the ratios of the easily-transportable fractions.The concentrations of Cu and Zn in the soil were positively correlated with the SOC.The long-term heavy application of pig manure has the risk of contaminating the soil with Cu and Zn.7.Based on hydroponic experiments,the toxic threshold of Cu concentration in solution ranged from 900 to 1200 ?g/L for rice seedlings.The recommended copper concentration in nutrient solution was 1000 pg/L for screening tolerant rice cultivars in hydroponics based on relative SPAD value,shoot and root dry weight,root length and root dehydrogenase activity,and oxidizing capacity and shoot Cu concentration of rice.Sixteen local rice cultivars collected were classified into tolerant,normal,and sensitive groups by cluster analysis,and four,one,and 11 cultivars belonged to each group in order.Xiushui123,Xiushui134,Jiahe991,and Xianghu301 belonged to the tolerant group;Xiushui137 belonged to the sensitive group.The cluster analysis based on hydroponic experiments is an effective method for identifying rice cultivars that are tolerant to Cu stretss. |
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