紫花苜蓿与3种多年生禾本科牧草轮作的土壤养分生长季动态比较

Effects of growing three perennial grasses followingalfalfa on soil nutrient dynamics

摘要:

为研究紫花苜蓿与多年生禾本科牧草轮作对土壤养分的影响,以5龄紫花苜蓿(A)为前茬,设紫花苜蓿—草地早熟禾(AK)、紫花苜蓿—无芒雀麦(AS)、紫花苜蓿—苇状羊茅(AT)3种轮作模式,以连作紫花苜蓿(AA)为对照,研究了不同处理在生长季土壤有机质、全氮、碱解氮、全磷、有效磷含量的动态变化。结果表明:0~20 cm土层,在第1茬牧草刈割后,牧草生长季中和生长季末3个时间点:AS轮作较AA连作有机质含量分别降低9.99%、9.28%、7.81%,AT轮作较AA连作全氮含量分别降低13.30%、6.76%、11.41%,AT轮作较AA连作碱解氮含量分别降低11.72%、18.13%、12.30%,AT轮作较AA连作全磷含量分别降低4.95%、5.23%、6.42%,AK轮作较AA连作有效磷含量分别提高13.25%、13.16%、10.83%。在20~40 cm土层3个生长季时间点;AT轮作较AA有机质含量分别降低15.57%、12.38%、13.56%,AT轮作较AA连作全氮含量分别降低7.44%、3.76%、5.67%,AT轮作较AA连作分别碱解氮含量分别降低16.49%、17.87%、18.45%,AK轮作较AA连作有效磷含量分别增加19.87%、16.72%、12.55%。紫花苜蓿后茬种植禾本科牧草,会降低土壤有机质、全氮、碱解氮含量,并提高土壤速效磷含量,对全磷含量无显著影响。

Abstract:

This study investigated the rotational effects of three perennial grasses following five-year-old alfalfa on the dynamics of soil organic matter,soil total nitrogen,alkali-decomposed nitrogen,soil total phosphorus and available phosphorus in different growing seasons.The three rotational treatments included alfalfa-kentucky bluegrass (AK),alfalfa-smooth bromegrass(AS),and alfalfa-tall fescue(AT),with continuous alfalfa cropping (AA) as the control.In the 0~20 cm soil layer,relative to AA at three sampling stages (after the cut of first forage stubble,in the middle of growing season,and at the end of the growing season),the organic matter content of AS rotation decreased by 9.99%,9.28%,and 7.81%;the total nitrogen content of AT rotation crops reduced by 13.30%,6.76%,and 11.41% respectively;the available nitrogen content of AT rotation cropping reduced by 11.72%,18.13%,and 12.30% respectively;and the total phosphorus content of AT rotation cropping reduced by 4.95%,5.23%,6.42%;the effective phosphorus content of AK rotation increased by 13.25%,13.16%,10.83%.In the 20~40 cm soil layer,relative to AA at three sampling stages,the organic matter content of AT rotation reduced by 15.57%,12.38%,and 13.56%,respectively;the total nitrogen content of AT rotation decreased by 7.44%,3.76%,and 5.67%,respectively;the AT nitrogen content decreased by 16.49%,17.87%,and 18.45%,respectively;and the effective phosphorus content in AK increased by 19.87%,16.72%,and 12.5%,respectively.Planting gramineous forages following alfalfa reduced soil organic matter,total nitrogen and alkali-decomposed nitrogen,while increased soil available phosphorus,and had no significant effects on soil total phosphorus.