Aboveground biomass production and soil water dynamics of four leguminous forages in semiarid region, northwest China

The study evaluated the forage productivity and water use of four leguminous grasses namely alfalfa (Medicago sativa L.), vetch (Astragalus adsurgens Pall.), sainfoin (Onobrychis viciaefolia Scop.) and Lespedeza davurica grown in semiarid region on the Loess Plateau of China. The experiments were conducted in the years 2001-2004 where each grass was grown on four 7 tu x 6 m experimental plots. The aboveground biomass production considered the sum of dry litter and standing parts was measured every year at the end of growth season. Soil water measurements were made from soil drill (phi 4 cm cores) every month for soil extending to a depth of 300 cm in the first and second year and up to 500 cm in the rest of the period. The yearly biomass production, soil water storage volume as well as its change, monthly rainfall and water consumption of each grass were statistically analyzed. A linear correlation was used to analyze the biomass production and total water used in evapo-transpiration. Stepwise regression was performed to evaluate the relationship between biomass production and monthly rainfall and soil water storage to explain the differences among grasses. The analysis showed that biomass production of both the vetch and L. davurica were significantly (P < 0.05) correlated with total precipitation of April to June while that of sainfoin and alfalfa was significantly (P < 0.05) correlated with total precipitation of the growth season (April to October). All four grasses exhibited positive (P < 0.05) aboveground biomass production response to soil water usage, but there is difference among. Alfalfa, vetch and sainfoin had a drying effect at a depth less than 2.0 m and consistently showed profiles with the lowest soil water content. Profiles with the lowest soil water content also had greater herbage growth and greater depths of water extraction. (c) 2006 SAAB. Published by Elsevier B.V. All rights reserved.