Effects Of Simulated Acid Rain On Soil Environment Of Maize And Soybean Croplands In Black Soil Region

The northeast black land is the most important commodity grain base in China.At present,the black soil in China is seriously degraded,among which acid deposition aggravates soil acidification.In order to explore the effects of acid deposition on soil environment and influencing factors in black soil region of Northeast China,the effects of acid rain on soil chemical propertie s,soil microorganisms and greenhouse gas emissions of black soil were analyzed by spraying corn and soybean farmland soil with simulated acid rain.The main results are as follows:1.Under the experimental conditions,because of the strong buffer of black soil to acid,acid rain had no significant effect on the chemical properties of corn and soybean farmland soil,such as pH,organic matter,total nitrogen,available nitrogen and so on.However,compared with the control（CK）,with the increase of ac id rain intensity,the pH of maize soil treated once（T1）and twice（T2）decreased by 0.75%and 9.7%respectively,while the pH of soybean soil under T1 and T2 treatments decreased by 3.7%and 4.8%,respectively.The increase of acid rain intensity promote d the increase of available nitrogen in maize and soybean soil in the short term,however,had no obvious effect on total nitrogen and organic matter.2.Compared with the control,with the increase of acid rain intensity,soil bacteria in maize farmland decreased.T2 treatment had a significant inhibitory effect on soil bacteria,while T1 treatment had no significant effect.There was no significant change in fungi and actinomycetes,however,maize soil fungi increased with the increase of acid rain inten sity,and actinomycetes decreased gradually.The effect of acid rain treatment on the number of bacteria and fungi in soybean soil increased at first and then decreased,and the number of bacteria and fungi in T1 treatment increased significantly,while th at in T2treatment decreased compared with CK,while actinomycetes decreased with the increase of acid rain intensity.3.There was no significant difference in N ₂O and CH₄ cumulative emissions between maize and soybean soil under acid rain treatment,but the N₂O emission flux of maize soil under T2 treatment was higher than that of CK,T1 and CK from acid rain treatment to filling stage,and the N ₂O emission flux of soybean soil under T1 and T2 treatments was significantly higher than that of CK from seed filling stage to mature stage.Acid rain treatment has no special rule for CH ₄ emission capacity of maize and soybean.Acid rain treatment had a significant effect on CO ₂ cumulative emissions from maize and soybean soils.Compared with the control,with the increase of acid rain intensity,the cumulative CO ₂ emissions from maize soil increased,while CO ₂emissions from soybean soil decreased at first and then increased.4.With the increase of acid rain intensity,there was no significant difference in GHGI and GWP of soil greenhouse gas emissions between corn and soybean fields.Compared with the control,the GHGI of maize soil under T1 treatment decreased by 8.7%,while the GHGI of T2 treatment increased by 7.9%.With the increase of acid rain intensity,the GHGI of soybean soil increased gradually,and the CHGI of T1 and T2 increased by4.1%and 10.6%compared with CK,respectively.The greenhouse gas GWP of the two crops under T1 treatment decreased compared with CK,while the GWP under T2 treatment increased compared with CK.