长期施用有机肥对减缓菜田耕层土壤酸化的影响

Effects of Long-Term Application of Organic Fertilizers on Reducing SoilAcidification of Plough Layer in Vegetable Fields

高投入、高产出、集约化的现代农业生产中土壤酸化问题频频发生,连年大量施用氮肥及不合理的氮肥配施导致土壤pH下降明显,是造成土壤酸化的主要原因之一。采取有效的施肥措施来控制土壤酸化对提升农田质量具有重要意义。为此,通过10年定位试验对不施肥(CK)、有机肥(M)、推荐施肥(R)、增施氮肥(R+N)、增施磷肥(R+P)等5种处理的不同施肥措施进行土壤耕层酸化的研究。结果表明:10年后,土壤耕层酸化顺序为增施氮肥>增施磷肥>推荐施肥>不施肥=有机肥处理。长期过量施用氮肥导致菜田耕层土壤中H+含量增加、pH显著降低、电导率(EC)显著升高(P<0.05)。尤其在施肥3—5 a间土壤pH值出现明显降低。R、R+N、R+P处理与CK和M处理相比pH值、pH变化量、pH年均变化率均显著降低(P<0.05),说明CK和M处理对土壤的pH值降低有一定的缓冲作用。ω(C)/ω(N)升高的处理(CK、M、R)比ω(C)/ω(N)下降的处理(R+N、R+P)pH下降程度慢,即ω(C)/ω(N)升高,有利于减缓耕层土壤酸化。长期施用有机肥(牛粪)可显著减少(P<0.05)菜田耕层土壤NO3−-N与NH4+-N的累积量,增加有机质含量,从而减缓耕层土壤酸化作用。R、R+N、R+P处理NO3−-N与NH4+-N的累积量是M处理的1.27—2.87倍,而M处理的耕层土壤有机质含量是R、R+N、R+P处理的1.25—1.45倍。施氮量是影响菜田耕层土壤酸化的主要环境因子(P<0.05),施氮量与EC呈正相关,而与pH呈负相关;有机质与pH呈正相关,而与EC呈负相关。

The problem of soil acidification occurs frequently in modern intensive agricultural production with high input and output.The continuous application of large amounts of nitrogen fertilizer and unbalanced ratio of nitrogen fertilizer cause the soil pH value to drop significantly,which is one of the main causes of soil acidification.Taking into effective measures of fertilizer application to control soil acidification is of great significance for improving farmland quality.A 10–year in situ trial was carried on to monitor soil acidification of plough layer.Five treatments of different fertilizer applications,which include non-fertilizer application(CK),organic fertilizer application(M),recommended fertilizer application(R),increased nitrogen fertilizer application(R+N)and increased phosphorus fertilizer application(R+P).The results showed that after continuous 10 years monitoring,the soil acidification order in different treatments is as following:increased nitrogen fertilizer application>increased phosphate fertilizer application>recommended fertilizer application>no fertilizer application=organic fertilizer application.Long-term excessive nitrogen fertilizer application led to an increase in H+content,with a significant decrease in pH and increase in electrical conductivity(EC)in the plough layer of vegetable fields(P<0.05).Especially during the 3rd to 5th years of fertilizer application,the soil pH value decreased obviously.Compared with CK and M treatments,the pH value,pH change,and annual average change rate of pH of R,R+N,R+P treatments were significantly reduced(P<0.05).It indicated that CK and M treatment had buffering effect on soil pH dropping.The treatments(CK,M,R)withω(C)/ω(N)increase had a slower pH decrease than the treatments(R+N,R+P)withω(C)/ω(N)decrease,which indicating the increase ofω(C)/ω(N)was beneficial for slowing down the soil acidification of plough layer.Long-term application of organic fertilizer(cattle dung)can significantly reduce the accumulation of NO3−-N and NH4+-N in plough layer soil of vegetable fields(P<0.05),increase the organic matter content,and thus slow down the soil acidification in plough layer.The cumulative amount of NO3−-N and NH4+-N in R,R+N,R+P treatments was 1.27 to 2.87 times than that of M treatment,while the soil organic matter content in M treatment was 1.25 to 1.45 times than that of R,R+N,R+P treatments.Nitrogen application was the main environmental factor affecting soil acidification in vegetable fields(P<0.05).Furthermore,nitrogen application was positively correlated with EC while negatively correlated with pH value.However,soil organic matter content was positively correlated with pH value and negatively correlated with EC.