稻麦轮作区连续秸秆还田和施肥条件下砂姜黑土无机磷分布特征

Characteristics of inorganic phosphorus in lime concretion black soil under continuous straw-return and fertilization in a rice-wheat rotation area

为了揭示秸秆还田与化肥施用对砂姜黑土无机磷的影响,基于实施多年的秸秆还田与施肥定位试验,设置了常规施肥+秸秆全量还田(HN_1)、常规施肥量50%+秸秆全量还田(HN_4)、不施肥+秸秆全量还田(HN_0)、常规施肥+秸秆移除(N_1)、常规施肥量50%+秸秆移除(N_4)、不施肥+秸秆移除(N_0)处理,采用田间取样与室内化验分析相结合的方法研究了土壤不同形态无机磷的剖面分布及累积特点。结果表明,同等化肥施用水平下,秸秆还田较秸秆移除显著提高了土壤Ca_2-P和Fe-P的含量,提高幅度最高达219.05%和51.35%,两种形态无机磷占无机磷总量的百分比也显著提高;Ca_8-P和Al-P含量整体上有所降低,Ca_(10)-P含量显著降低,无机磷总量有所提高。秸秆还田配施化肥对土壤无机磷的活化效果随化肥施用量的减少和土层深度的增加而降低。秸秆还田不施化肥使土壤Ca_2-P、Ca_8-P、Al-P和Fe-P含量显著降低。与秸秆移除相比,秸秆还田配施化肥促进了Ca_(10)-P等潜在磷源的转化和分解。Ca-P(Ca_2-P、Ca_8-P、Ca_(10)-P)和Fe-P所占比例最高,为供试土壤无机磷的主要构成形态。常规施肥条件下秸秆还田促进了土壤速效磷(Olsen-P)含量的快速提升,常规施肥量50%条件下秸秆还田促进了表层土壤Olsen-P的提升,而无肥条件下秸秆还田对土壤Olsen-P含量的提升无明显效果。土壤Ca_2-P、Ca_8-P、Al-P和Fe-P与土壤Olsen-P的相关性均达到显著或极显著水平,表明4种无机磷与土壤Olsen-P关系密切,可能为土壤有效磷的重要来源。因而,秸秆还田不施化肥会加速土壤无机磷的耗竭,秸秆还田与化肥合理配施,可通过将缓效态无机磷转化为Ca_2-P和Fe-P等高活性无机磷,提高土壤供磷能力。

The aim of this study was to determine the effects of straw return and chemical fertilizer application on the inorganic phosphorus content in lime concretion black soil.Therefore,we conducted a multi-year field experiment with various straw return and fertilization treatments,and analyzed the profiles and accumulation characteristics of different forms of inorganic phosphorus in soil.The field experiment had six treatments:conventional fertilizer application+straw total return(HN 1);50%of conventional fertilization+straw total return(HN 4);no fertilizer+straw total return(HN 0);conventional fertilization+straw removal(N 1);50%of conventional fertilization+straw removal(N 4);and no fertilizer+straw removal(N 0).The results showed that under the same level of chemical fertilizer application,straw return significantly increased the contents of soil Ca 2-P and Fe-P by up to 219.05%and 51.35%,respectively,compared with those in the straw removal treatments.The proportions of Ca 2-P and Fe-P out of total inorganic phosphorus also increased significantly with straw return.In general,the Ca 8-P and Al-P contents decreased to some extent while Ca 10-P decreased significantly,and the total amount of inorganic phosphorus increased when straw was returned.The activation of inorganic phosphorus in soil with straw return and chemical fertilizer application decreased with decreasing amounts of fertilizer and increasing soil depth.The application of chemical fertilizers without straw return significantly reduced the contents of Ca 2-P,Ca 8-P,Al-P,and Fe-P in the soil.Compared with straw removal alone,straw removal+chemical fertilizer promoted the conversion and decomposition of potential phosphorus sources such as Ca 10-P.The main forms of inorganic P in soil were Ca-P(Ca 2-P,Ca 8-P,and Ca 10-P)and Fe-P.Under conventional fertilization conditions,straw return resulted in a rapid increase in Olsen-P content in soil.Under 50%conventional fertilization,straw return increased the Olsen-P content in surface soil.Returning straw to soil without fertilizer application did not significantly increase the Olsen-P content in soil.The correlations between soil Olsen-P and soil Ca 2-P,Ca 8-P,Al-P,and Fe-P reached significant or extremely significant levels,indicating that these four forms of inorganic P were closely related to soil Olsen-P,and may be important sources of available P in the soil.Therefore,the no-fertilizer and straw returning treatment could accelerate the depletion of inorganic P in soil.Together,the results showed that the rational application of straw and chemical fertilizers can improve the soil P supply by converting low-activity inorganic P into high-activity forms of inorganic P such as Ca 2-P and Fe-P.