沼液过量还田对土壤环境容量及玉米生长的影响

Effects of Excessive Biogas Slurry Returning on Soil Environmental Capacity and Maize Growth

以沼液过量还田为前提,探讨沼液不同还田量对土壤环境质量和玉米生长发育的影响,提出沼液还田的安全容量。根据目标需氮量确定沼液施用量,共设5个处理:未施加任何肥料(N0 t/hm^(2),CK);1倍氮当量沼液(N 0.885 t/hm^(2),1N);2倍氮当量沼液(N 1.770 t/hm^(2),2N);3倍氮当量沼液(N 2.655 t/hm^(2),3N);4倍氮当量沼液(N 3.540 t/hm^(2),4N)。结果表明,沼液还田可显著增加玉米田土壤中Cu、Zn含量,1N处理为最佳安全容量,2N、3N、4N处理土壤存在Cu、Zn污染风险,其中,玉米完熟时4N处理Cu、Zn含量分别超出风险筛选值10.96%和10.36%,风险最大。与对照相比,沼液还田显著增加玉米苗期土壤中可溶性盐含量,提高土壤的pH值,但随着生育期的延长,可溶性盐含量和pH值呈下降趋势;至玉米的完熟期,1N、2N、3N、4N处理土壤可溶性盐含量比对照分别高出30.59%、52.16%、72.35%、108.63%,土壤pH值比对照分别高出3.95%、6.41%、9.05%、13.65%。所有处理的蛔虫卵死亡率均为100%,故沼液还田不存在蛔虫卵存活的安全风险,但3N与4N处理土壤存在大肠杆菌污染的风险,完熟期这2个处理土壤的大肠杆菌菌群含量分别为20、30个/g。沼液还田可增加玉米产量和改善玉米品质,以3N处理产量最高和品质最优,与对照相比,粗蛋白、粗脂肪、粗淀粉含量分别提高了19.82%、89.01%、11.31%,产量是对照的2.08倍。综合分析认为,以玉米产量最大和品质最优为优先目标时,3N处理为最优,以土壤环境安全容量为优先目标时,1N处理为最优。

The effects of different amounts of biogas slurry application on soil environmental quality and maize growth were studied,and the safe capacity of biogas slurry returning to the field was put forward.Five treatments were used,and application amount of biogas slurry was converted by maize nitrogen nutrient requirement.The five treatments included no fertilizer application(0 t/ha of N,CK),one time nitrogen equivalent biogas slurry(0.885 t/ha of N,1N),two times nitrogen equivalent biogas slurry(1.770 t/ha of N,2N),three times nitrogen equivalent biogas slurry(2.655 t/ha of N,3N),four times nitrogen equivalent biogas slurry(3.540 t/ha of N,4N).The results showed that,the content of Cu and Zn in soil could be significantly increased when biogas slurry was returned to the soil,and 1N treatment was the best safe capacity for soil environment.Cu and Zn pollution risk existed in 2N,3N,and 4N treatments,among them,the contents of Cu and Zn in 4N treatment at the mature stage exceeded their risk screening values by 10.96%and 10.36%,reaching the highest risk.Compared with CK,the soluble salt content and the pH values of soil increased at maize seedling stage,but they showed a decreasing trend with the extension of maize growth period.At the mature stage of maize,the soil soluble salt contents of 1N,2N,3N and 4N treatments were 30.59%,52.16%,72.35%and 108.63%higher than that of CK,and the soil pH values were 3.95%,6.41%,9.05%and 13.65%higher than that of CK.The mortality of ascaris eggs in all treatments was 100%,so there was no safety risk of the survival of ascaris eggs when biogas slurry was applicated into soil,but 3N and 4N treatments had risk of Escherichia coli contamination.The quantities of Escherichia coli in the two treatments were 20 and 30 per gram soil respectively at the mature stage.The biogas slurry application could increase the maize yield,and improve the maize quality significantly,and 3N treatment was the best,compared with CK,the contents of crude protein,crude fat and crude starch increased by 19.82%,89.01%and 11.31%respectively,and the yield was 2.08 times of CK.It was concluded that 3N treatment was the best when the yield and quality were taken as the priority objectives,and 1N treatment was the best when the soil environmental safety capacity was taken as the priority goal.