有机无机肥配施提高旱地麦田土壤养分有效性及酶活性

【目的】有机无机肥配施可显著提高土壤微生物活性，改善土壤养分供应状况。深入理解不同氮肥用量配施有机肥下土壤的生物化学性状，为充分发挥肥料效益，实现冬小麦高产稳产提供科学施肥依据。【方法】以冬小麦为供试作物，在黄土高原南部半湿润易旱区连续三年进行了田间定位试验。采用裂区试验，设置5个氮肥用量 (N 0、75、150、225、300 kg/hm2)，配施或不施有机肥 (30 t/hm2)。在冬小麦拔节期、抽穗期、灌浆期、成熟期，取0—20 cm土层样品，采用常规方法测定土壤养分和酶活性。在收获期，调查了冬小麦籽粒产量。【结果】1) 冬小麦产量以施氮量N 150 kg/hm2配施有机肥处理最高，且有机无机肥配施与单施化肥处理相比能够在减少19.1%的氮肥用量条件下，保证冬小麦产量稳产高产，此外在天气不理想的状况下，冬小麦的净收益也能保持在较高水平。2)在冬小麦的整个生育期，有机无机肥配施处理可显著提高0—20 cm土层土壤有机质、全氮、有效磷、速效钾、硝态氮含量以及土壤蔗糖酶、碱性磷酸酶和脲酶活性，与单施化肥处理相比分别增加18.2%、27.4%、149.3%、31.4%、27.6%、4.0%、4.7%、1.5%，但对过氧化氢酶活性无明显促进作用，且除了脲酶以施氮量N 300 kg/hm2配施有机肥的活性最高，其余指标均以施氮量N 150 kg/hm2配施有机肥处理效果最佳。3) 施氮量、有机肥、冬小麦生育期显著影响土壤蔗糖酶、碱性磷酸酶、过氧化氢酶和脲酶活性，施氮量和有机肥的交互效应显著影响碱性磷酸酶活性，施氮量和冬小麦生育期的交互效应显著影响土壤蔗糖酶、碱性磷酸酶和过氧化氢酶活性，有机肥和冬小麦生育期的交互效应显著影响土壤碱性磷酸酶和过氧化氢酶活性，施氮量、有机肥和冬小麦生育期三者的交互效应显著影响土壤蔗糖酶活性。4) 相关分析表明，土壤碱性磷酸酶与有机质间、脲酶与速效钾之间均未达显著相关水平，土壤蔗糖酶、碱性磷酸酶、过氧化氢酶和脲酶与有机质、全氮、有效磷、速效钾均呈显著或极显著正相关。【结论】土壤养分、酶活性和冬小麦产量之间密切相关，在施用有机肥30 t/hm2的基础上配施氮肥N 150 kg/hm2，有利于增强黄土高原南部半湿润易旱区冬小麦土壤生态系统的可持续性。

Improvement of soil nutrient availability and enzyme activities in rainfed wheat field by combined application of organic and inorganic fertilizers

【Objectives】Combined application of organic and inorganic fertilizers can significantly improve soil microbial activity and improve soil nutrient supply. In order to give full play to the fertilizer benefits and achieve high and stable yields of winter wheat, it is necessary to understand the biochemical characteristics of soil under different nitrogen (N) application rates combined with application of organic fertilizer.【Methods】Field positioning experiments were conducted for three consecutive years on winter wheat in a semi-humid and drought-prone areas of the southern Loess Plateau. Different N application rates (N 0, 75, 150, 225, 300 kg/hm2) combined with organic manure (0 and 30 t/hm2) were set up by split plot experiment. In jointing stage, heading stage, filling stage and maturity stage of winter wheat, 0?20 cm soil samples were taken to determine soil nutrients and enzyme activities by using conventional methods. During the harvest period, the grain yield of winter wheat was investigated.【Results】1) The highest yield of winter wheat was obtained when 150 kg/hm2 of N rate was combined with organic fertilizer (N150 + M), and compared to the chemical N fertilizer application, organic and inorganic fertilizer application could ensure the stable yield and high yield of winter wheat when the N fertilizer rate was reduced by 19.1%, in addition, under the unsatisfactory weather conditions, the net income of winter wheat could also be maintained at a relatively stable and high level. 2) During the whole growth period of winter wheat, the combined application of organic and inorganic fertilizers significantly increased soil organic matter, total N, available P, readily available K, NO₃?-N content, and the activities of sucrase, alkaline phosphatase and urease in 0?20 cm soil layer by a mean of 18.2%, 27.4%, 149%, 31.4%, 27.6%, 4.0%, 4.7%, 1.5%, respectively, compared with that without manure, while it had no significant effect on catalase activity. Except the highest value of urease activity occurring in the N300 + M (the combination of manure with N 300 kg/hm2) treatment, the other indicators were the best treated with the N150 + M (the combination of manure with N 150 kg/hm2) treatment. 3) N application, organic fertilizer and growth period of winter wheat significantly affected soil invertase, alkaline phosphatase, catalase and urease activities, the interaction between N application rate and organic fertilizer significantly affected alkaline phosphatase activity, the interaction between N application rate and growth period of winter wheat significantly affected soil invertase, alkaline phosphatase and catalase activities, the interaction effect of organic fertilizer and winter wheat growth period significantly affected soil alkaline phosphatase and catalase activities, and the interaction effect of N application rate, organic fertilizer and winter wheat growth period significantly affected soil invertase activity. 4) There was no significant correlation between soil alkaline phosphatase and organic matter, urease and readily available potassium. The activities of soil invertase, alkaline phosphatase, catalase, and urease were all positively correlated with soil organic matter, total N, available P and readily available K.【Conclusions】Soil nutrients, enzyme activities and winter wheat yields were closely related. The combined application of manure with chemical N 150 kg/hm2 is recommended for enhancing sustainability of ecosystem of winter wheat field in the semi-humid and drought-prone areas of the southern Loess Plateau.