Effects of Matric Potential Threhold Used for Control of Shallow Drip Irrigaion on Growth and Yield of Alfalfa

Abstract

【Objective】 Matric potential measured at a position below the emitter is often used as a threshold to control drip irrigation. In this paper we investigate the effect of the threshold on growth and yield of alfalfa irrigted by shallow drip irrigation. 【Method】 The field experiment was conducted in Hulunbeier area in Inner Mongolia, with the variety Longmu 806 used as the model plant. We compared five matrix potential thresholds measured at the depth of 10 cm below the emitter: -10, -20, -30, -40 kPa and -50 kPa, to study their effects on soil moisture distribution, growth and fresh grass yield, as well as water use efficiency of the alfalfa. 【Result】 The matrix potential threhold significantly affected spatial distribution of soil moisture; the higher the soil matrix potential threshold was, the higher the soil water content in the 0~30 cm soil layer was. With the decrease in the matrix potential, the plant height and fresh grass yield of the alfalfa increased first and then declined; the highest plant height and fresh grass yield were achieved when the soil matrix potential was -20 kPa. The average irrigation water use efficiency of the alfalfa increased with the decrease in soil matrix potential, and the highest irrigation water use efficiency was when the soil matrix potential was between -50 kPa and -40 kPa. 【Conclusion】 In order to maintain high and stable grass yield, for 1~3 year old alfalfa, the soil matrix potential threshold at the depth of 10 cm underneath the emitter of the shallow subsurface drip irrigation should be -20 kPa, when water holding capacity of the soil in the tillage layer is poor and the roots of the alfalfa are shallow.

Keywords

• artificial grassland
• shallow subsurface drip irrigation
• irrigation schedule
• soil matrix potential
• irrigation water use efficiency