【作者】 沈浦；

【导师】 徐明岗； 何新华； Daniel Murphy；

【作者基本信息】 中国农业科学院 ， 土壤学， 2014， 博士

【摘要】 磷是植物生长发育必需的元素，也是引起水体污染的重要原因。土壤磷的化学、生物有效性变化和机制，是土壤学研究的核心问题之一。针对不同生态气候农田连续施肥下土壤有效磷的演变特征和机制研究相对薄弱，本文分析了十三个15–31年长期试验点（四个单季旱作、五个双季旱作和四个水旱轮作农田）不施磷（Control、N）、化学磷肥（NP、NPK）和有机肥配施化学磷肥（NPM、NPKM）等处理的观测数据，结合温室盆栽试验，主要研究（1）长期不同施肥土壤有效磷的变化特征；（2）不同作物土壤有效磷的农学阈值；（3）不同施肥下土壤有效磷对磷盈亏的响应特征；（4）不同C/N有机物料对磷素循环的影响，主要结果如下：（1）长期不同施肥下十三个点土壤有效磷的变化总体为：有机肥配施化学磷肥增加4.2mg/kg/yr，化学磷肥增加0.9mg/kg/yr，不施磷下降0.2mg/kg/yr。旱地农田中有机肥配施化学磷肥提升了土壤有机碳，提高了有效磷及其占全磷百分比（磷活化系数）；若土壤有机碳增加1.0g/kg，有效磷增加0.04–0.15mg/kg，磷活化系数增加0.3–1.2%。水旱轮作土壤有机碳与有效磷呈显著正相关，而与磷活化系数关系不显著。（2）不同作物土壤有效磷的农学阈值总体为：小麦、玉米和水稻土壤有效磷的农学阈值分别为7.5–23.5mg/kg、5.7–15.2mg/kg和4.3–14.9mg/kg。除哈尔滨外，其余点土壤有效磷需要在基础值提升2.8–18.9mg/kg，才能达到相应作物的农学阈值。（3）不同轮作下土壤有效磷的变化显著受到磷盈亏的影响。每盈亏100kg P/ha，双季旱作下土壤有效磷平均增量为：有机肥配施化学磷肥（11.1mg/kg）>化学磷肥（2.3mg/kg）>不施磷（0.7mg/kg）；而水旱轮作则不同，化学磷肥（11.6mg/kg）>有机肥配施化学磷肥（6.3mg/kg）>不施磷（~0mg/kg）。单季旱作下，上述两类施磷处理在各试验点的有效磷增量不同。单季和双季旱作下，土壤有机碳增加促进了盈余磷转化成有效磷，而水旱轮作下，有机碳对盈余磷的转化没有显著影响。（4）在磷盈余和亏缺下，不同C/N有机物料对磷在土壤-微生物-植物间组分变化有显著差异。在磷盈余下，低C/N有机物料显著增加了微生物对磷的固持、促进了植物对土壤有效磷的吸收，微生物磷占总磷比例在C/N12.5、25和50依次为5.4%、4.7%和1.7%；植物磷比例分别为14.8%、9.5%和2.1%。在磷亏缺下，低C/N有机物料仅增加了微生物对磷的固持，而未增加植物对磷的吸收。综上，我国典型旱作农田（特别双季旱作）配施有机肥对土壤有效磷的提升、加快达到有效磷农学阈值的效果显著优于水旱轮作。在农业生产实践中，在磷充足的农田选用低C/N有机肥更有利于促进植物和微生物对土壤磷的吸收利用。更多还原

【Abstract】 Phosphorus (P) is a major essential element for plant growth, metabolism and productivity, whilstexcess P has resulted in worldwide eutrophication in water bodies. The chemical and biologicalmechanisms of soil P availability are the key points for soil science. The study is mainly to address theevolution characteristics and mechanisms of soil available P under long-term (15–31) fertilizations atvarious eco-climate conditions. Six fertilization treatments were chosen:①Control,②chemical N,③chemical N and P (NP),④chemical NP and K (NPK),⑤chemical NP and manure (NPM);⑥chemical NPK and manure (NPKM) at13long-term experiment sites (four mono-upland sites, fivedouble-upland sites and four rice field-upland sites). Data analyses from these long-term fieldexperiments with a glasshouse pot experiment were used to examine (1) evolution characteristics of soilavailable P (SAP);(2) critical values of soil available P for wheat/barley, maize and rice;(3) response ofsoil available P to P apparent balance under different soils and fertilizations;(4) P cycling insoil-microorganism-plant systems under the addition of organic compounds into soil with differentcarbon/nitrogen ratios. The main findings are as followings:(1) Effects of long-term fertilizations on evolution characteristics of SAP of the13sites weregenerally showed that: SAP was increased by4.2and0.9mg/kg respectively under chemical P plusmanure treatment and chemical P treatments, but decreased by0.2mg/kg under no P treatments. At themono-/double-cropping upland sites, an increase of1.0g/kg soil organic carbon (SOC) would increaseSAP by0.04–0.15mg/kg and P activation coefficient (PAC, percentage of soil available P to total P) by0.3–1.2%, respectively. Though significant relationship showed between SOC and SAP, no significantrelationship showed between SOC and PAC at the upland rice sites.(2) The critical value of SAP for different crops under different soils showed that:7.5–23.5mg/kgfor the wheat/barley,5.7–15.2mg/kg for the maize and4.3–14.9mg/kg for the rice. An increase of2.8–18.9mg/kg SAP based on their initial values would achieve their relevant critical values of SAP forthese sites except Harbin (which was already achieved the critical SAP value based on its initial value).(3) The change in SAP was significantly affected by P apparent balance under different croppingsystems. The mean change in SAP with100kg P/ha surplus ranked as: chemical P plus manuretreatments (11.1mg/kg)> chemical P treatments (2.3mg/kg)> no P treatments (0.7mg/kg) at fivedouble-cropping upland sites, whilst chemical P treatments (mean11.6mg/kg)> chemical P plusmanure treatments (mean6.3mg/kg)> no P treatments (~0mg/kg) at four rice field-upland sites.Change in SAP with P surplus varied among the four mono-upland sites. At mono-/double-croppingupland sites, the promotion of SOC would significantly increase the change in SAP with P surplus.However, there was no significant effect of SOC on the transformation of surplus P into SAP at ricefield-upland sites.(4) Effects of organic compounds (OC) with various C/N ratios on the transformation of P amongsoil-microorganism-plant systems were different under P deficit and P surplus conditions. Under the P surplus conditions, OC with low C/N ratios increased P assimilation by microorganisms and P uptakeby plants from soil available P fractionations. The microbial biomass P fractionations were5.4%,4.7%and1.7%, whilst plant P fractionations were14.8%,9.5%and2.1%, respectively. However, OC withlow C/N ratios only increased P assimilation by microorganisms, but had less impact on the P uptake byplants.In summary, the use of organic manure to increase soil available P is more effective in Chinesetypical upland (especially double-cropping upland) soils than in rice-field upland soils. In agriculturalpractices, adapting organic manure with lower C/N is more reliable to promote P uptake by crops and Passimilation by microorganisms under P surplus conditions.更多还原