陇东黄土高原春播紫花苜蓿不同茬次生物量动态研究

Biomass dynamics of every stubble of spring-sowed alfalfa in the loess plateau of Longdong

2003~2005年,在陇东黄土高原区进行的春播紫花苜蓿生物量观测试验表明,春播紫花苜蓿当年的株高,由缓慢增长转为快速增长的转变时段在分枝到现蕾期,由快速增长再次转为缓慢增长的时段在开花期后;生长二、三年紫花苜蓿,一年中适宜刈割三次,前二茬鲜草的平均日增长量明显高于第三茬,并且生长三年的各茬鲜草平均日增长量普遍高于生长二年的;最大地上生物量均出现在第一、二茬,其鲜草和干草重量分别占三茬总重量的76.9%~84.3%和79.1%~86.3%;各茬次紫花苜蓿鲜干比在现蕾期后明显降低,到开花期刈割前降至最低。年际和地域的气候条件差异直接反映在紫花苜蓿各茬次生物量和鲜干比的变化上,在水份满足的情况下,以气温日较差大的地域更有利于紫花苜蓿物质积累。

The observations and the experiments of the biomass of spring-sowed alfalfa were carried out in the loess plateau of Longdong from 2003 to 2005. The results showed that the transition period of the plant height growth of spring - sowed annual alfalfa from slow to rapid is between the divaricating stage and the budding stage. The transition period of the plant height growth from rapid to slow comes after the budding stage. As for biennial and triennial alfalfa,clipping three times within a year is suitable. The average day-to-day increase of fresh grass weight of the first and second stubble alfalfa is obviously greater than that of third stubble alfalfa. Most instances showed that the average day-to-day increase of fresh grass weight of triennial alfalfa is grearer than biennial alfalfa. The maximum fresh grass and hay weight of alfalfa present in first and second stubble. For the first and second stubble alfalfa, fresh grass weight accounts for 76.9 % -- 84.3 % and hay weight accounts for 79.1% -- 86.3 % of all three stubbles. The ratio of fresh grass weight to hay weight of every stubble alfalfa decreases obviously after budding stage and falls off to minimum in blooming stage（clipping ago）. The interannual variation and the regional difference of climatic conditions affect the growth of alfalfa. If the need of water being enough for alfalfa growth, the areas where daily range of temperature is comparatively wide will be favorable to the substance accumulation of alfalfa.