灌水和氮肥类型对土壤微生物量和酶活性的影响

灌水和施氮肥类型对土壤微生物和酶的影响尚不清楚。该研究旨在评估不同灌水和氮肥类型对土壤微生物生物量和酶活性的影响。结果表明,与清水灌溉相比,再生水灌溉显著增加了土壤细菌、放线菌、革兰氏阳性菌的生物量以及总磷脂脂肪酸,增加幅度分别为7.60%、10.48%、4.97%和4.88%。施氮肥显著提高了土壤细菌生物量和总磷脂脂肪酸,增加幅度范围分别为13.42%~17.34%和8.12%~11.19%。与清水灌溉相比,再生水灌溉并没有显著增加土壤脲酶、过氧化氢酶和蔗糖酶活性。施氮肥也没有显著提高土壤脲酶、过氧化氢酶和蔗糖酶活性。土壤微生物和酶在施缓释尿素肥的土壤中更为活跃。研究结果表明,与其他土壤微生物相比,放线菌和革兰氏阳性菌生长得更快,能更有效地利用再生水灌溉带入的可溶性有机氮;而细菌能更有效地利用氮肥带入的硝态氮。再生水灌溉和施缓释尿素肥在增加土壤微生物生物量和酶活性方面更有效。为了获得更好的土壤质量,更高的作物产量和可持续性利用水资源,建议夏玉米-冬小麦轮作种植利用再生水滴灌并施用缓释尿素肥。

Effects of irrigation water and N fertilizer types on soil microbial biomass and enzymatic activities

Effects of irrigation water and N fertilizer types on soil microbes and enzymes are poorly understood.This study aimed to evaluate the effect of different irrigation water and N fertilizer types on soil microbial biomass and enzymatic activities.A 2-year experiment(2015—2017)was conducted at the Tongzhou Experimental Station of Tongzhou District,Beijing,China(39°42′6.93″N,116°41′2.31″E).The experiments utilized a factorial randomized complete block design with 8 treatments(2×4)in 3 replicates.The first factor had 2 irrigation water types(fresh water(FW)and reclaimed water(RW)),and the 2nd factor had 4 N fertilizer types(no nitrogen,urea,ammonium sulfate,and slow-release urea).Physicochemical,microbe and enzyme analyses from soil and water samples were determined.The results showed the contents of SOC,SON,DOC,DON,TN,NO3--N,and NH4+-N in different treatment soils were significantly different across crop seasons(P<0.05).The average contents of DON in soils irrigated with RW are significantly higher than that in soils irrigated with FW(P<0.05).Fertilization increased the SOC,SON,DON,TN,and NO3--N contents in the soils significantly(P<0.05).No significant interaction between irrigation and fertilization on the soil SOC,SON,DOC,DON,TN,NO3--N,and NH4+-N contents.the DON content in the soils irrigated with RW was average 8.33%significantly higher than in the soils irrigated with FW(P<0.05).The SOC,SON,DON,TN and NO3--N contents in the soils fertilized with inorganic N was on average 8.35%,10.13%,11.75%,11.60%and 92.99%significantly higher,respectively,than that in the soils fertilized with no nitrogen(P<0.05).Soil bacterial biomass under different treatments ranged from 9.59 to 12.18 nmol/g.The soil actinobacterial biomass values under different treatments ranged from 1.01 to 1.24 nmol/g.The soil G+bacterial biomass values under different treatments were 6.10-6.73 nmol/g.Compared with FW and RW irrigation significantly increased the soil bacterial,actinobacterial,and gram-positive(G+)bacterial biomasses and total phospholipid fatty acids(PLFAs)by 7.60%,10.48%,4.97%and 4.88%,respectively.N fertilization significantly increased soil bacterial biomass by 13.42%-17.34%and increased the total PLFAs by 8.12%-11.19%.Compared with FW,RW irrigation did not significantly increase soil urease,catalase and invertase activities.N fertilization did not significantly increase soil urease,catalase and invertase activities.Soil microbes and enzymes were more active in the soils fertilized with slow-release urea.These results indicate that actinobacteria and G+bacteria grew more quickly and could more efficiently utilize the DON introduced by the RW and that the soil bacteria could more efficiently utilize NO3--N introduced by the fertilizers than the other microbes.RW irrigation and slow-release urea fertilization were more effective to increase the soil microbes and enzymes.For better soil quality,higher yields and save water resources,drip irrigation with RW under slow-release urea fertilization was recommended for summer maize-winter wheat crop rotation.