黄土高原不同粮草种植模式土壤碳氮及土壤酶活性

摘要

通过在陇中黄土高原半干旱区对苜蓿(Medicago sativa)-作物轮作地进行长期定位试验,探讨不同种植模式对土壤碳氮形态及其相关酶活性的影响.6种种植模式分别为苜蓿-苜蓿、苜蓿-休闲、苜蓿-小麦(Triticum aesti-vum)、苜蓿-玉米(Zea mays)、苜蓿-马铃薯(Solanum tuberosum)和苜蓿-谷子(Setaria italica).结果表明,苜蓿-作物种植模式不利于土壤总有机碳的积累,而苜蓿翻耕后保持休闲则可维持较高的有机碳含量;与苜蓿连作相比,苜蓿-作物种植模式的土壤有机碳降低了1.60%~23.11%,全氮含量增加了3.81%~21.83%.不同作物对土壤养分吸收利用状况不同,进而引起土壤酶发生变化.与苜蓿连作相比,苜蓿粮食作物种植模式在降低土壤过氧化氢酶和蛋白酶活性的同时,提高了土壤硝酸还原酶活性;其中土壤过氧化氢酶活性和蛋白酶活性分别降低了5.20%~12.30%和15.03%~43.43%,硝酸还原酶活性提高了1.26%~28.79%.苜蓿连作和苜蓿-粮食作物种植模式间的土壤脲酶活性无显著差异(P>0.05),但均高于苜蓿-休闲处理.相关性分析结果表明,土壤脲酶活性与土壤有机碳、全氮含量呈显著正相关(P<0.05),可作为衡量土壤肥力的指标.%A long-term field experiment comparing the effects of different alfalfa-crop rotations on soil carbon and nitrogen forms and related enzyme activities was conducted at Dingxi,western Loess Plateau.Six rotation patterns[alfalfa - alfalfa,alfalfa - fallow,alfalfa - wheat (Triticum aestivum ),alfalfa - corn (Zeamays ), alfalfa-potato(Solanum tuberosum )and alfalfa- millet(Setaria italica )]were compared.The results showed that the alfalfa crop rotation is not conducive to accumulation of soil total organic carbon and total nitrogen,and alfalfa ploughing maintains higher soil organic carbon levels.Compared to alfalfa-alfalfa,soil organic carbon and total nitrogen of alfalfa crop rotation system were decreased by 1.60%~23.11% and 3.81%~21.83%.Owing to differences insoil nutrient uptake among crops,soil enzyme content will be changed.Compared with con-tinuous alfalfa cropping,soil catalase and protease activity of alfalfa crop rotation were reduced,and the soil ni-trate reductase activity was increased;the soil catalase activity and the protease activity decreased by 5.20%~12.30% and 15.03%~43.43%,and the nitrate reductase activity increased by 1.26%~28.79%.There was no significant difference between continuous alfalfa cropping and alfalfa crop rotation on soil urease activity (P >0.05),but it was higher than that in the alfalfa fallow treatment.Moreover,correlation analysis showed that-soil urease activity and soil organic carbon and total nitrogen content were significantly positively correlated. These can be used as indices of soil fertility.