| The North China Plain is the main jujube-producing region,and it accounted for 60%of the total production in China.Nevertheless,intensive management including excessive fertilizers input and spray pesticides were widely performed in order to obtain higher yield and income benefits.The use of agro-chemicals has been shown to accelerate the deterioration of soil quality and negatively affect the quality and safe of jujube.Therefore,it is imperative to explore a sustainable and environmentally friendly agricultural strategy for improving soil quality and decreasing chemical fertilizer input to minimize environmental risks and maintain the sustainable development of jujube orchards.Biochar is known to as soil amendment for soil agriculture and environmental management,due to its specific physiochemical properties,such as high porosity,great adsorption capacity.However,how to evaluate effects of combined application of peanut shell-derived biochar and nitrogen amendments through identifying specific measures and filtering key indexes of soil fertility according to local conditions thus identifying the optimum amendment rate still needs further research on regional agriculture production.Therefore,a three-year field experiment?2013-2015?with different rates of biochar and nitrogen fertilizer addition was performed to investigate their effects on soil fertility?soil nutrients,soil aggregate structure,microbial biomass,enzyme activities,etc.?,jujube yield and quality in the North China Plain.There are thirteen treatments,including CK?no fertilizer?,four-level of biochar?C 0,2.5,5 and 10 t/hm2,namely,C0,C1,C2 and C3?and three-level of nitrogen fertilizer?N 300,450 and 600 kg/hm2,namely,N1,N2 and N3?.All biochar-amended treatments were evaluated,and selected the optimum amendment rates through our study,which can provide a theorectical basis for soil productivity improvement,high-efficient fertilization and eco-environment protection in jujube orchards.The main conclusions are summarized as follows:?1?The object of this study was to evaluate the effects of combined application of peanut shell biochar and nitrogen fertilizer on soil bulk density,the distribution and stability of soil mechanically and water-stable aggregates base on a three years' consecutive field experiment on fluvo-aquic soils in the North China Plain.This study could elucidate the responses of soil and jujube to soil fertility quality under biochar and N fertilizer application.The results showed that compared with the control,biochar amendments significantly decreased soil bulk density,and soil bulk desity decreased with the increasing biochar addition,with the lowest values were observed in C3N1 and C3N3 treatments in Xinzheng and Puyang city,decreased by 20.5%and 15.9%,respectively.Biochar-amended treatments had no significant influence on the proportions of>0.25 mm macro-aggregates under dry sieving,while the proportions of>0.25 mm water-stable macro-aggregates increased with biochar addition rate.In addition,the percentage of aggregate destruction was significantly decreased under biochar amendments compared with the control,the values of mean weight diameter and geometric mean diameter under wet sieving were significantly increased by 56.7%?52.4%and 29.2%?27.3%,respectively.The contents of oil organic carbon were significant higher in biochar-amended treatments than in the control.A significant positive correlation between soil organic carbon content and mean weight diameter?geometric mean diameter?P<0.05?was observed in this study according to the correlation analysis.?2?A three-year consecutive field experiment?2013?2015?was conducted to investigate the effect of biochar and nitrogen fertilizer amendments on soil microbial properties in jujube orchard according to microbiology.The results showed that biochar,nitrogen fertilizer amendments and their interactions significantly affected the contents of soil microbial biomass carbon.The greatest increment of 148.4%and 208.6%,respectively,were found in microbial biomass carbon contents in two study areas compared with the control.Biochar significantly improved microbial biomass nitrogen?MBN?contents,increased by 138.9%and 159.4%,respectively compared to the control.Soil microbial biomass in all C treatments were higher than the C0,but there were no significant differences among the three N treatments when biochar was applied at the rate of 2.5 t/hm2.Neither soil urease nor invertase were significantly affected in their activities by combination application of biochar and nitrogen fertilizer,the activities of alkaline phosphatase were significantly improved in Xinzheng orchard,with the highest increment of 23.0%?P<0.05?.The biochar,nitrogen fertilizer amendments and their interactions significantly improved the community of soil bacteria and actinomycetes in tested jujube orchards,the numbers of fungi then decreased at the medium and highest addition rate.Statistics analyses showed that three quantitative factors,soil microbial biomass,enzyme activities and microbial quantities,had reciprocally significant positive correlations.?3?To investigate the effect of combined application of peanut shell biochar and nitrogen fertilizer on soil organic matter,total N and soil available nutrient based on two-way ANOVA,which could elucidate the interactions between soil,biochar material and soil microbes on soil physical properties.The results showed that there was no significant difference was observed in soil pH under biochar and nitrogen fertilizer amendment compared with the control.Generally,biochar improved soil organic matter,total N,P,K and available N,P,K contents,soil nutrients increased with the increase biochar addition.There was no significant difference was found in tested soil nutrients,except soil total potassium under biochar and nitrogen fertilizer interaction.Compared with the control,soil organic matter,total N and available N in Xinzheng orchrd,increased by 3.6%?33.2%,81.5%and 33.6%,respectively.And in Puyang orchard,soil organic matter,total K and available N increased by 11.7%?32.4%,55.3%and 68.9%,respectively compared to the control.?4?A field experiment was performed consecutively to study the effect of application of different biochar?0,2.5,5,10 t/hm2?and nitrogen fertilizer?300,450,600 kg/hm2?on mean fruit weight,jujube yields and quality in jujube orchards areas of the North China Plain.The results showed that biochar addition increased mean fruit weight and jujube yields.One year after the application of biochar to the jujube orchard,soil fertility under biochar and N fertilizer amendments increasing with the increase of keeping years,and the yields of jujube were also gradually improved.The highest average jujube yields of 13502.1 kg/hm2 and 21182.6 kg/hm2 were observed in C3N2 and C3N2 treatments in Xinzhegn and Puyang orchards,increased by 31.7%and 17.8%,respectively,compared with the control.Biochar rates improved soil soluble solid,vitamin C,protein and amino acid contents of jujube?huizao?at different levels,whereras no significant differences were found in bianhesuan jujube quality except for the amino acid content.The optimal amounts for biochar and nitrogen fertilizer should be 10 t/hm2,450 kg/hm2 and 10 t/hm2,300 kg/hm2 in Xinzheng and Puyang jujube orchard,respectively according to these above-mentioned results and the real cost of production.?5?The objects of this study were to identify the optimum amendment rate under the combined application of peanut shell biochar and nitrogen fertilizer at different levels in jujube plantation.A total of fourteen important quantitative indices?i.e.,organic matter,total and available soil nutrient,soil microbial biomass,enzyme activities?related to soil chemical,physical and biological properties were selected,and factor analysis and minimum Euclidean distance method were employed to evaluate the overall soil fertility under biochar and nitrogen fertilizer amendments.Jujube yield was used to verify the evaluation results.The results indicated that three common factors that could reflect 82%of the original information quantity without losing any original variables were extracted from the initial 14 indices.There were significant positive correlations among soil nutrients,microbial biomass,enzyme activities and microbial population according to the correlation analysis,which indicated these soil fertility indices are interdependent and closely correlated,and then affected soil quality.The highest soil quality scores were observed in the C3N2 and C3N2 treatments,respectively,which were almost line with the results of jujube yields.Hierarchical cluster analysis classified 13 treatments into three and five main group in study areas on the basis of the measured parameters,which were generally consistent with the result of soil quality scores.The optimal amount for biochar and nitrogen fertilizer according to these results should be 10 t/hm2,450 kg/hm2 and 10 t/hm2,300 kg/hm2 in Xinzheng and Puyang jujube orchard,respectively.Further studies are needed to estimate its effective mechanisms and long-term effects under the combined application of peanut shell-derived biochar and nitrogen fertilizer. |
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