河西荒漠灌区紫花苜蓿生产及其碳密度对建植年限和茬次的响应

Effects of planting year and stubble on alfalfa production and vegetation carbon density in Hexi Irrigation Area

以河西荒漠灌区2~7龄(2~7 a)紫花苜蓿(Medicago sativa L.)为研究对象,探究紫花苜蓿干草产量、营养品质和植被碳密度对种植年限及茬次的响应。结果表明,低龄(<5 a)苜蓿第2茬产量较高,而高龄(≥5 a)苜蓿第1茬产量较高;5 a苜蓿干草总产量显著高于其他种植年限,较6 a和7 a苜蓿分别提高27.81%和27.97%;5 a苜蓿产量动态指数亦较高。苜蓿粗蛋白含量在第4茬较高,介于17.67%~19.38%之间,7 a苜蓿第4茬相对饲喂价值较其他年限分别显著提高75.22%、50.91%、39.58%、42.68%和31.62%。植被碳密度变化规律与产量类似,即5 a苜蓿植被碳密度显著大于其他种植年限,较2、3、4、6 a和7 a苜蓿分别提高18.58%、27.37%、15.30%、25.14%和17.18%。随刈割次数增加,同龄苜蓿干草产量逐渐降低,营养品质和植被碳密度为第1茬较高。灰色关联度综合分析表明,河西荒漠灌区紫花苜蓿建植后2~5 a是生长旺盛时期,且第1茬生产和生态价值较高。因此,注重苜蓿草地建植前5年及第1茬生长期的合理管理对于维持苜蓿的优质高产和延长草地使用寿命具有重要意义。

In this study,alfalfa(Medicago sativa L.)planted 2~7 years in Hexi Desert Irrigation District was used as the research subject.By exploring the response of alfalfa hay yield,nutrient quality,and vegetative carbon density to planting year and stubble.The results showed that low-age(<5 a)alfalfa reached higher yields in the second stubble,while high-age(≥5 a)alfalfa had higher yields in the first stubble.Total hay yield of alfalfa in 5 a was significantly higher than in other planting years,increased by 27.81%and 27.97%compared to the lower yield years 6 a and 7 a,respectively.The index of alfalfa yield dynamic variation in 5 a was also higher.The crude protein content of alfalfa was higher in the fourth cutting,ranging from 17.67%to 19.38%.Alfalfa harvested in the fourth cutting demonstrated significantly higher relative feeding values compared to other cuttings,with increases of 75.22%,50.91%,39.58%,42.68%,and 31.62%,respectively.The trend in carbon density was similar to that of yield,carbon density in 5 a alfalfa was significantly higher than other planting years,with increases of 18.58%,27.37%,15.30%,25.14%,and 17.18%compared to 2 a,3 a,4 a,6 a,and 7 a,respectively.As the number of mowing increased,alfalfa production with the same age gradually decreased,and both nutrient quality of alfalfa and vegetative carbon density were higher in the first stubble.A comprehensive gray correlation analysis concluded that the 2 a to 5 a after the establishment of alfalfa was a period of vigorous growth,and all of them reached higher economic and ecological benefits in the first stubble in the Hexi Desert Irrigation District.Therefore,it is important to focus on the reasonable management in the first five years and first growing stubble of alfalfa grassland,which is important for maintaining high quality and yield of alfalfa and prolonging the service life of alfalfa grassland.