水氮供应对地下滴灌紫花苜蓿生长特征及草地小气候的影响

为探讨不同水氮处理条件下紫花苜蓿生长状况与草地小气候特征的关系,以2年生紫花苜蓿“巨能7号”为研究对象,采用田间试验和室内分析相结合的方法,研究了宁夏引黄灌区地下滴灌条件下不同滴灌量和施氮量处理下紫花苜蓿生长特征和草地小气候的变化。结果表明:1)滴灌量和施氮量对紫花苜蓿的株高、叶面积和鲜草产量都有显著的影响,表现为紫花苜蓿的株高、叶面积和鲜草产量均随滴灌量和施氮量的增加而增加,当施氮量增加到一定值时,继续增施氮肥,其鲜草产量增产效果在不同滴灌量处理下表现出不同的趋势。2)与不施氮处理相比,增施氮肥降低了紫花苜蓿株间空气温度、浅层土层温度和株间光照强度,而增加了群体内部空气相对湿度。3)不同滴灌量对紫花苜蓿的生长微环境的调节作用不同,随着滴灌量的增加,紫花苜蓿群体相对湿度逐渐提高,而紫花苜蓿株间气温和浅层土层温度降温效应越明显。4)紫花苜蓿生育期间株高与叶面积、草产量和群体内部相对湿度呈极显著正相关(P<0.01),与群体内光照强度、株间气温、浅层土壤温度呈极显著负相关(P<0.01)。合理减少滴灌量和施氮量不仅能维持紫花苜蓿良好的生长特征,而且能提高鲜草产量和改善草地生态环境条件。本研究旨在为紫花苜蓿群体微环境生态因子的改善及高产优质栽培措施提供科学依据。

Effects of water and nitrogen supply on growth and microclimate characteristics of alfalfa under drip irrigation

The overall aim of our research is to improve the microenvironment ecological factors of alfalfa and to recommend appropriate regulation of water and fertilizer use based on scientific evidence. In this study, the relationship between the amounts of inputs (irrigation and nitrogen fertilizer) and the growth and microclimate characteristics of alfalfa were investigated in a 2-year drip-irrigation field experiment in the Yellow River irrigation region of Ningxia. The results showed that the amounts of drip irrigation and nitrogen fertilizer significantly affected the plant height, leaf area, and yield of alfalfa. Compared with the no-fertilizer treatment, fertilization decreased the air temperature, soil temperature, and illumination within the alfalfa stand, but increased the relative humidity. The microenvironment of alfalfa varied among the different irrigation treatments. As the amount of irrigation increased, the relative humidity in the alfalfa stand gradually increased, and the cooling effects on air temperature and soil temperature became stronger. There were strong positive correlations between plant height and leaf area, grass biomass, and relative humidity. There were significant negative correlations between plant height and illumination, temperature, and soil temperature. Therefore, a reasonable decrease in the amount of irrigation and nitrogen fertilizer can not only maintain good growth of alfalfa, but also increase grass yield and improve grassland ecological conditions.