长期秸秆还田对潮土土壤各形态磷的影响

Effects of Long-term Straw Return on Various Fractions of Phosphorus in Fluvo-aquic Soil

基于黄淮海低平原区潮土上33年长期肥料定位试验,采用蒋柏藩―顾益初的石灰性土壤无机磷分级方法,研究冬小麦―夏玉米轮作中长期不同氮磷用量下秸秆还田对土壤全磷、有效磷(Olsen-P)及各形态无机磷的影响。结果表明:黄淮海低平原区潮土上冬小麦―夏玉米轮作中P2O5用量0~240 kg hm^(-2),随磷肥用量的增加,土壤全磷、Olsen-P、无机磷总量及无机磷中Ca2-P、Ca8-P、Al-P和Fe-P均显著增加,O-P和Ca10-P无显著变化;当土壤输入磷量低于作物输出磷量时,无论秸秆还田与否,土壤全磷、无机磷总量、Olsen-P和无机磷中除Ca8-P外的其他各形态磷均无显著变化;当土壤输入磷量高于作物输出磷量时,随秸秆用量的增加土壤全磷、Olsen-P和无机磷中的Ca2-P、Ca8-P、Al-P均显著增加,其中以Olsen-P增幅最大,无机磷中以Ca2-P增幅最大,其次为Ca8-P,再次为Al-P;土壤磷素盈余和亏缺量与土壤中各磷形态含量均呈显著正相关关系。

During the last decades,long-term fertilization has improved soil fertility in the Huang-Huai-Hai Plain. With increasing soil available P,crop response in yield to phosphorus fertilization has been found declining,while environmental risks of unreasonable fertilization are becoming an hot issue of concern. In recent years,returning straw to fields is a farming practice getting more and more popular in the Huang-Huai-Hai Plain,however,few studies,let alone long-term straw return field experiments,have been carried out to investigate impacts of such changes in field management on fractions of soil inorganic P,soil P availability,yield response as well as potential environmental risks. Therefore,based on the 33-year long-term fertilization field experiment effects of straw return in conjunction with chemical P fertilization on total-P,Olsen-P as well as fractions of inorganic phosphorus in fluvo-aquic soil in the Huang-Huai-Hai Plain were studied. Fractionation of inorganic P was done using the Gu Y-C,Jiang B-F method. In this experiment,the split-plot method was used,and 4 main plots,i.e. N0S0,N1S1,N2S2 and N3S3 were laid out. Each main plot was split into 3 sub-plots,applied with straw at a rate of 0,2 250 and 4 500 kg hm^-2,separately. This experiment under a winter wheat-summer maize rotation system was initiated in 1981,and designed to have maize straw returned to the field in 1981～1983,1987～1989,1993～1995,1999～2001 and 2005～2013 and winter wheat straw returned in 2000 and on. Results show that among the plots the same in P2O5 application rate,（0,60 or 20 kg hm^-2 in chemical phosphorus）,those having maize straw returned for 21 years and those having wheat straw returned for 15 years witnessed soil Ca8-P significantly increased with rising straw return rate;in plots applied with P2O5 at 240 kg hm^-2 in chemical phosphorus,soil total P,available P and inorganic P,such as Ca2-P,Ca8-P and Al-P,were all significantly increased with rising straw return rate,but Fe-P,O-P and Ca10-P did not change much in content. Compared to Plot N0P〈0S0,Plot N0P〈0S2（maize straw returned at 4 500 kg hm^-2）was 10.2% or 7.33 mg kg^-1 higher in content of soil Ca8-P;compared to Plot N1P1S0,Plot N1P1S2 was 32.5% or 24.39 mg kg^-1 higher in content of soil Ca8-P;compared to Plot N2P2S0,Plot N2P2S1 was 10.3% or 10.07 mg kg^-1 and Plot N2P2S2 was 27.3% or 26.71 mg kg^-1 higher in content of soil Ca8-P;and in comparison with Plot N3P3S0,Plot N3P3S1 and N3P3S2 was 64.5% or 2.47 mg kg^-1and 178.6% or 6.84 mg kg^-1 higher in content of soil Ca2-P,42.0% or 80.15 mg kg^-1and 67.8% or 129.3 mg kg^-1 higher in content of soil Ca8-P and 37.0% or 15.68 mg kg^-1 and 61.7% or 26.14 mg kg^-1,higher in content of Al-P,respectively. In terms of relative increment（p〈0.05）the fractions of inorganic P displayed an order of Ca2-PCa8-Pal-P. In addition,in the plots the same in straw return rate,impacts of chemical P fertilization rate on soil P were also examined：in comparison with Plot N0P〈0S0,Plots N1P1S0,N2P2S0 and N3P3S0 had soil total P,inorganic P and Olsen-P increased on average by 154,164 and 7.24 mg kg^-1（23.1%,35.9%,593.2%）,respectively,and Ca2-P,Ca8-P,Al-P and Fe-P increased on average by 1.53,49.43,14.18 and 13.09 mg kg^-1（242.9%,68.9%,59.5% and 40.7%）,respectively. Furthermore,in comparison with N0P〈0S0,Plots N1P1S1,N1P1S2,N2P2S1,N2P2S2,N3P3S1 and N3P3S2 had soil total P,inorganic P and Olsen-P increased on average by 2013,271 and 9.90 mg kg^-1（35.1%,59.1%,811.7%）,and Ca2-P,Ca8-P,Al-P and Fe-P increased by 3.67,97.65,22.99 and 17.04 mg kg^-1（581.7%,136.1%,96.6% and 53.0%）,respectively. In conclusion,in the farmlands under the winter wheat-summer maize rotation system in the Huang-Huai-Hai Plain,when P input falls lower than P output（120 kg hm^-2）,the soils would not have much changes in total P,inorganic P,Olsen-P and fractions of inorganic P,regardless of whether straw is returned in addition to fertilization. However,when P input goes beyond P output,soil total P,Olsen-P as well as Ca2-P,Ca8-P,Al-P and Fe-P will all increase,and among the P fractions,Olsen-P ranks first in relative increment,and is followed by Ca2-P,Ca8-P and Al-P. In addition,balance of soil phosphorus input and output is positively related to contents of the various fractions of soil phosphorus（p〈0.05）.