Soil-Moisture Tension Effects on Root Development and Shoot Growth of Alfalfa

Abstract

An experiment was conducted to determine the effect of soil-moisture stress maintained in the effective root depth on root and shoot development of alfalfa. These levels were maintained before depleted moisture was replaced to bring soil moisture in root depth to field capacity. Highest shoot growth resulted when 600 m.b. suction was maintained. Root development, however, was more for a drier level of more than 700 m.b.
The results indicate that under soil-moisture stress the shoot (aerial portion) of alfalfa is affected more than the root system. Consequently, in consideration of the plant system as a whole, growth was retarded at a faster rate in the aerial portion of alfalfa than in roots.
An explanation based upon the relation of both plant water potential, and rate of soil moisture conductivity to the roots, to soil-water potential was suggested. The soil aeration and oxygen rate of supply to roots was also suggested to explain the difference between the effect on the shoot and on the root. The results suggest an average amount of 3.18 inches of soil moisture to be replaced each 15 days to give the optimum results for irrigating alfalfa under conditions similar to those experimented.