| Due to coal mining in Shanxi Province,a large area of land subsidence had resulted in a decrease in cultivated land area,destruction of the original soil structure,and lack of nutrients,especially the availability of nitrogen is extremely low.In order to effectively fertilize the reclaimed soil in coal mining subsidence area,understand the nitrogen mineralization characteristics of organic fertilizer,therefore explore how to quickly increase the soil nitrogen content and nitrogen fertilizer utilization rate of reclaimed soil was one of the urgently solving problems in coal mining subsidence areas.This study took the coal mining subsidence soil from Shuiyu Coal Mine,Xiaoyi City,Shanxi Province as the research object,and used indoor aerobic culture method to explore the nitrogen mineralization characteristics and dynamic changes of related enzyme activity under applying three kinds of organic fertilizers(chicken manure,pig manure,and cow manure)and chemical fertilizers.Meanwhile through field experiment for three consecutive years,the study analyzed effects of combined application of different amounts of organic and inorganic fertilizers on nitrogen utilization and soil nitrogen forms in reclaimed soils,and confirmed the amount of organic fertilizer for quickly fertilizing the soil in the mining area,thereby providing scientific basis for efficiently fertilizing low-yielding farmland,especially new reclaimed soil in mining areas.The main findings were as follows:(1)The indoor aerobic culture method was used to study the nitrogen mineralization characteristics and dynamic changes of related enzyme activity under applying three kinds of organic fertilizers(chicken manure,pig manure,and cow manure)and chemical fertilizers.The results showed: The NH4+-N content in each treatment showed a trend of “decreasing-fluctuation-gradual stabilization” with the extension of incubated time.The NH4+-N content and culture time during 0-14 days of incubation showed a significantly negative correlation(P<0.01).The NO3--N content of each treatment showed a "rising-smooth fluctuation-stable" trend with the incubated time,and the changes conforms to the Sigmoid’s 3 Parameter index model(R2 = 0.6396 ~ 0.9174);in the whole cultivation process,the soil NH4+-N and NO3--N content varied with different fertilization treatments,with a sequence of chemical fertilizers>chicken manure>pig manure>cow manure>control.In terms of soil enzyme activity,the application of organic fertilizers significantly increased soil nitrogen conversion-related enzyme activities as a whole,but the growth rate depended on the type of organic fertilizer and the cultivation time.In the later period of incubation(98 days),urease activity of pig manure treatment(2.17 mg/g/24h)was highest and protease activity of chicken manure treatment(0.02mg/g/24h)was highest.Asparaginase of cattle manure treatment changed the least,but glutaminase of cattle manure treatment changed most.(2)A field experiment was conducted to study the effects of combined application of different amounts of chemical inorganic fertilizers(total nitrogen amount 0,100,150,200 kg / hm2 is expressed as IF0,IF100,IF150,IF200)and organic and inorganic fertilizers(chicken manure and chemical fertilizer combined application rates as 1:1 ratio at 100,150,200 kg/hm2 N,expressed as MF100,MF150,MF200)for three consecutive years on the maize yield,nitrogen absorption by plants and nitrogen utilization efficiency in reclaimed soil.The results showed: Compared with no nitrogen treatment,each nitrogen treatment for three consecutive years significantly increased corn grain yield(25.37% ~ 104.93%)and nitrogen absorption(68.19% ~ 239.03%)in coal mining subsidence areas.Compared with single fertilizer application,the combined application of chicken manure and chemical fertilizer could make maize yield and nitrogen uptake basically the same or increased.For the above-ground nitrogen uptake of maize,there was no significant difference between the 150 kg/hm2 nitrogen treatment and higher nitrogen content(200 kg/hm2)treatment(P>0.05),so 150 kg/hm2 nitrogen amount could be used as the recommended amount of fertilizer for reclaimed soil in the mining area.In terms of nitrogen fertilizer utilization rate,under the same nitrogen application level,the combined application of chicken manure and chemical fertilizer for three consecutive years could improve the nitrogen recovery rate compared with single application of chemical fertilizer treatment.Nitrogen partial productivity showed a decrease with the increase of nitrogen application rate.When the nitrogen application rate was 150 kg/hm2,the combined application of organic and inorganic fertilizers could improve the nitrogen agronomic efficiency.(3)A field experiment was conducted to study the effects of combined application of different amounts of organic and inorganic fertilizers on nitrogen forms of reclaimed soil for three years of continuous fertilization.The results showed: The mineral nitrogen content of different fertilization treatments(the total nitrogen content of single fertilizer application is 0,100,150,200 kg/hm2;the total nitrogen content of chicken manure and fertilizer 1: 1 is 100,150,200 kg/hm2)in soils for three consecutive years showed an increased trend with the depth of soil layers in 0-60 cm soil layers.Compared with the single fertilizer application,the mineral nitrogen content of combined application of organic and inorganic fertilizers treatments in the soil layer(0-20 cm)increased by 7.98%,and the mineral nitrogen residue of combined application of organic and inorganic fertilizers treatments in the deep layer(40-60 cm)decreased by 8.48% on average,especially the mineral nitrogen residue of combined application of chicken manure and chemical fertilizer treatment at 150 kg/hm2 nitrogen amount was the most obvious.As the fertilization years increased and the precipitation of growth period in each year reduced,the loss risk of soils mineral nitrogen of fertilizer treatments was reduced.After three consecutive years of fertilization,organic-inorganic combined application increased the content of soil amino acid nitrogen,ammonianitrogen,amino sugar nitrogen,and non-hydrolysable nitrogen in plough layer(0-20 cm)soil,which increased by 2.32% to 12.54%,8.67% to 17.60%,8.83% to 16.47%,and 13.95%,respectively.The content of hydrolysable unknown nitrogen in soil of each treatment was significantly lower than that of the blank treatment without fertilization.The components of organic nitrogen in the cultivated layer(0-20 cm)varied with different nitrogen forms,with a sequence of amino acid nitrogen>non-hydrolysable nitrogen> hydrolysable unknown nitrogen>ammonia nitrogen>amino sugar nitrogen.Compared with single application treatments,the ratio of non-hydrolysable nitrogen and hydrolysable unknown nitrogen to soil total nitrogen of combined single application treatments in plough layer(0-20 cm)soil,reduced,which is difficult to be transformed and utilized in soil,and the decrease ratio was 2.23% ~ 3.72%.In the 0-60 cm soil profile,the changes of soil amino acid nitrogen content and non-hydrolysable nitrogen content with different treatments showed a trend of decreasing first with soil depth and then increasing.The changes of hydrolysable unknown nitrogen,ammonia nitrogen and amino sugar nitrogen increased continually.The content of amino acid nitrogen and ammonia nitrogen in the soil varied different fertilizer treatments,which was easy to mineralize in each soil layer,with a sequence of the combination treatment under the same nitrogen application rate>single application of chemical fertilizer treatment.On the whole,combined application of chicken manure and chemical fertilizer for three consecutive years could increase corn grain yield and nitrogen uptake in reclaimed soil,and increase the content of mineral nitrogen in the cultivated layer and the content of easily mineralized organic nitrogen in each soil layer.Among them,the combined application of chicken manure and chemical fertilizer at a nitrogen amount of 150 kg/hm2 had the best effect. |
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