紫花苜蓿与草地早熟禾轮作序列土壤氮素时空动态变化差异

摘要

通过研究甘农9 号紫花苜蓿(Medicago sativa cv. Gannong No.9) 与海波草地早熟禾(Poa pratensis Haibo) 轮作序列土壤氮素时空动态变化,探讨不同轮作序列土壤氮素时空分配机制.设置草地早熟禾→紫花苜蓿(PA) 和紫花苜蓿→草地早熟禾(AP) 轮作处理,以草地早熟禾→草地早熟禾(PP) 和紫花苜蓿→紫花苜蓿(AA) 为对照;于种植第二年4-10 月分别采集0-20 和20-40 cm 土层土壤,测定全氮与碱解氮含量.结果表明,PA 模式0-20 和20-40 cm 土层4-10 月全氮含量动态均呈先下降后上升趋势;0-20 cm 土层碱解氮含量动态呈上升-下降-上升趋势,而20-40 cm土层呈下降-上升-下降-上升趋势;0-20 cm 土层,除8 月外,4-10 月PA 模式全氮含量显著高于PP,20-40 cm 土层,除8、9 月外,4-10 月PA 模式全氮含量显著高于PP(P ＜ 0.05);除4 月外,4-10 月PA 模式0-20 cm 和20-40 cm土层碱解氮含量均显著高于PP(P ＜ 0.05).AP 模式0-20 cm 和20-40 cm 土层4-10 月全氮和碱解氮含量动态均略呈下降趋势;0-20 cm 土层,除4、5、6 月外,其他月份AP 模式全氮含量显著低于AA(P ＜ 0.05),20-40 cm 土层,除10 月外,其他月份AP 模式与AA 模式无显著性差异(P ＞ 0.05);0-20 cm 土层,除4、5、6 月外,其他月份AP 模式碱解氮含量显著低于AA; 20 -40 cm 土层, 10 月AP 显著低于AA(P ＜ 0.05), 其他月份下两处理间均不显著(P ＞0.05).综上所述,草地早熟禾→紫花苜蓿序列可显著提高土壤全氮和碱解氮含量,紫花苜蓿→草地早熟禾序列可使土壤全氮与碱解氮得到有效利用.与苜蓿→草地早熟禾轮作相比,草地早熟禾→苜蓿能有效增加土壤氮素含量.%The spatiotemporal variability of soil nitrogen content under alfalfa and Poa pratensis rotation systems was examined to explore the spatiotemporal distribution of soil nitrogen under different rotation systems. The experiment included four treatments, Poa pratensis→alfalfa (PA), alfalfa→Poa pratensis (AP), Poa pratensis→Poa pratensis (PP), and alfalfa→alfalfa (AA). Soil was sampled from depths of 0-20 and 20-40 cm each month, from April to October in the second year after planting. The total N and available N contents were measured. The results showed that, under the PA mode, dynamic changes in total N content at soil depths of 0-20 and 20-40 cm were observed, first decreasing and then increasing from April to October. Available N content at a soil depth of 0-20 centimeter soil first increased and then decreased, before increasing a second time; this up and down trend was observed for a soil depth of 20-40 cm. In the 0-20 cm layer, the soil total N content of PA was significantly higher than that of PP from April to October (except for August), while in the 20-40 cm soil layers, the PA mode was significantly higher than that of PP in all months except August and September. The soil available N content of PA was significantly higher than that of PP in different soil layers except for April(P ＜ 0.05). Under the AP treatment, dynamic changes in total and available N content followed downward trends in different layers. In the 0-20 cm soil layers, the soil total N content under AP was significantly lower than that under AA in all months except April, May, and June (P ＜ 0.05). In the 20-40 cm soil layers, there was no significant difference between AP and AA, except in October(P ＞ 0.05). In the 0-20 cm soil layer, except in April, May, and June, the soil available N content of AP was significantly lower than that of AA in other months, and in the 20-40 cm soil layers,the AP mode was significantly lower than AA in October (P ＜ 0.05). In summary, the Poa pratensis→alfalfa rotation system can significantly increase soil total and available N content, and the alfalfa→Poa pratensis rotation system can improve the utilization rate of soil total and available N content. Compared with alfalfa→Poa pratensis treatment, the Poa pratensis→alfalfa rotation system can effectively increase soil nitrogen content.