Effects of soil water and plant density interaction on plant and leaf characteristics of alfalfa

Suitable soil water content and plant density are key factors in the management of cultivated grassland. In this study, pot experiments were used to analyze the effects of different soil moisture (85%～90%, 75%～80%, 60%～65%, 35%～40% saturated soil moisture) and plant density (10, 15, 20 plants per pot) on plant and leaf characteristics of alfalfa (Medicago sativa). The results showed that the plant height, branch number, root neck diameter, main root length, and chlorophyll content of alfalfa increased first and then decreased with the increase of soil water content, while the leaf area and leaf dry weight showed an increasing trend. The root neck diameter, main root diameter, leaf area and leaf dry weight of alfalfa decreased with the increase of plant density, while chlorophyll a and chlorophyll b increased first and then decreased. Soil moisture and plant density interactions significantly affected only the root collar diameter (P < 0.05), and optimization results found that plant density was 15.1 plants per pot, and soil water content for soil saturated water capacity was 75.6% when root collar diameter was at its maximum, about 2.21 mm. This provides a scientific basis for regulating soil moisture and plant density in the field management of alfalfa.