紫花苜蓿根系生长特征研究

Study on root system growth characteristics of alfalfa

根据2003—2004年天水农业气象试验站、清水县气象站紫花苜蓿Medicage sativa2年栽培试验资料，分析了紫花苜蓿的根系生长特征及其与环境因素的关系。结果表明：紫花苜蓿生育期所需用的气象资源与建植时间长短有关，建植1年的植株在播种一结荚期需用的光照、热量资源都高于建植2年的植株；结荚期以后，建植1年的植株生长速度加快，生育期时间缩短，需用的气象资源接近或少于建植2年的植株。根系的伸长速度与地上枝叶的生长速度关系密切，生长最快的时段是在地上枝叶停止生长或生长缓慢的冬、秋季节．最缓慢的时期是分枝到刈割的枝叶旺盛生长期。根系生物量与10cm地温≥0℃积温呈非线性关系，在积温≥3500℃后生物量开始迅速增长；根系的含水量在10cm土层地温≥0℃积温达到1580～1815℃及5344～5941℃时达到最大。在相同的时段内，紫花苜蓿的土壤水分利用能力远强于粮食作物，其100cm土层内的水分累积消耗量比麦田偏高30％，地下土壤干层迹线比麦田深40cm，持续的时间比麦田长约120d。

Based on the 2 years （2003 2004） investigation data at Tianshui Agro-meteorological Experimental Station and Qingshui Weather Stations, the growth characteristics of alfalfa root system and the relationship between the growth and environment factors have been analyzed. The results showed that the meteorological resources which alfalfa required at each growth period depend on the time of planting. The sunlight and heat which one year old alfalfa required was higher than that of two years from seeding to pod setting period, after that, but the growth speed increased and the growth period shortened for one year old plant, compared to two years old plant. The results also indicated that the growth speed of root system had a close relationship with the growth of stem and leaves, the fastest growth period for root was in winter and autumn when leaves and stem stopped growing or grew slowly;and the slowest root growth period was in branching to reaping period when the stem and leaves grew luxuriantly. The accumulated biomass of root system nonlinearity correlated to ground （10 cm） temperature （≥0 ℃） , the accumulation speed increased obviously when the accumulated temperature was over 3 500 ℃. The water content was the highest at 1 580-1 815℃ and 5 344-5 941 ℃ accumulated ground （10 cm） temperature（≥0 ℃）. Alfalfa made much more use of soil water than other crops, and its 100 cm soil water consumption was 30% higher than in the wheat field. The dry layer trace was deeper by 40 cm and lasted 120 days longer than wheat field.