Physiological and Ecological Studies on the Summer Depressive Growth of Forage Crops : I. Effect of air temperature and soil moisture on the growth and the characteristics related to drought resistance of ladino clover and alfalfa.

Abstract

This paper gives the results of study made to find the influence of air temperature and soil moisture on the growth behaviour of the two legumes and to compare the characteristics related to drought resistance of them. The legumes used in this experiment were ladino clover which is sensible to summer depressive growth and alfalfa which is non-sensible to that damage. Four treatments as shown in Table 1. were applied to them for three weeks in a phytotron. The effect of low soil moisture on the growth of the two legumes was more harmful than that of high air temperature, though the growth of ladino clover was greatly affected by high air temperature. When low soil moisture and high air temperature were combined, the most severe injury was brought to the growth of the two legumes, especially to the growth of ladino clover. From these results, the cause of summer damage is considered to be brought by the influence of low soil moisture content and high air temperature in summer season. In comaparison with the morphological and physiological characteristics related to drought resistance of the two legumes, such as top and rot ratio, reflective index and osmotic value, ladino clover was inferior to alfalfa. By the each treatment, morphological and physiological characteristics of two legumes were adapted themselves to air temperature and soil moisture environment.