不同灌水施肥策略对土壤微生物量碳氮和酶活性的影响

Effect of different irrigation and fertilization strategies on soil microbial biomass carbon and nitrogen and enzyme activity

根区局部灌溉形成一个土壤水分分布不均匀的环境,影响了土壤微生物量和酶活性。为探明这种影响,在2种灌水水平(正常灌水和轻度缺水)和2种有机无机N肥配施(单施无机N肥和有机无机N肥配施)下,以常规灌溉(CI)为对照,研究分根区交替灌溉(AI)和固定部分根区灌溉(FI)对土壤微生物量C(MBC)、微生物量N(MBN)和酶活性的影响。与CI相比,AI提高拔节期土壤MBC和抽雄期土壤脲酶活性,但是降低大喇叭口期土壤MBC以及拔节期和抽雄期土壤MBN和拔节期土壤脲酶活性;FI增加抽雄期土壤转化酶活性,但是降低大喇叭口期土壤MBC和可溶性碳(DOC)以及3个时期土壤MBN。与正常灌水相比,AI下轻度亏水增加拔节期和抽雄期土壤DOC,但是降低大喇叭口期土壤MBC和拔节期土壤MBN。与单施无机N肥相比,AI下有机无机N肥配施增加拔节期土壤DOC、MBN和过氧化氢酶活性,而FI下则降低大喇叭口期土壤MBC和转化酶活性。因此,在轻度缺水和有机无机氮配施条件下,分根区交替灌溉可以提高玉米拔节期土壤微生物量碳和可溶性碳。

Partial root-zone irrigation creates a heterogeneous soil moisture distribution that may affect soil microbial biomass and enzyme activity. In order to understand such effect, a pot experiment was conducted to investigate the effects of alternate partial root-zone irrigation （AI） and fixed partial root-zone irrigation （FI） on soil microbial biomass C （MBC）, microbial biomass N （MBN） and enzyme activity when conventional irrigation （CI） as the control, under two irrigation levels （normal irrigation and mild water deficit） and two ratios of inorganic to organic N （only inorganic N and combined application of inorganic and organic N fertilizers）. Compared to CI, AI increased soil MBC at the jointing stages and urease activity at the tasselling stage, but reduced soil MBC at the bell-mouthed stage, MBN at the jointing and tasselling stages and urease activity at the jointing stage. FI enhanced soil invertase activity at the tasselling stage, but reduced soil MBC and dissolved oxidized C （DOC） at the bell-mouthed stage and MBN at the three stages. Compared to normal irrigation, mild water deficit increased soil DOC at the jointing and tasselling stages, but reduced soil MBC at the bell-mouthed stage and MBN at the jointing stages under AI. Compared to only inorganic N, combined application of inorganic and organic N fertilizers increased soil DOC, MBN and catalase activity at the jointing stage under AI, but it reduced soil MBC and invertase activity at the bell-mouthed stage under FI. Therefore, alternate partial root-zone irrigation increased soil microbialbiomass C and dissolved C at the jointing stage under mild water deficit and combined application of inorganic and organic N fertilizers.