Switchgrass and milkvetch intercropping under 2:1 row-replacement in semiarid region, northwest China: Aboveground biomass and water use efficiency

An experiment was conducted to investigate the aboveground biomass and water use characteristics of switchgrass (Panicum virgatum) and milkvetch (Astragalus adsurgens Pall.) in solecropping and 2:1 row-replacement intercropping in semiarid region on the Loess Plateau of China. Field experiments were conducted during the growing seasons from 2001 to 2005. The aboveground biomass production, considering the sum of dry litter and standing parts, was measured every year at the end of growth season. The aboveground biomass, soil water content dynamics, water use efficiency (WUE), actual yield loss (AYL), land equivalent ratio (LER) and aggressivity (A) were compared under sole and intercropping. Intercropping reduced the biomass production of the two component plants, compared with their respective pure stands. Milkvetch was the dominant species in the intercropping in 2001–2004, however its aggressivity to swichgrass decreased gradually as the growth years progressed, and in 2005 it became the dominant in the mixture. The equivalent biomass production under intercropping and whole WUE of mixture were significantly lower than their respective solecropping, although LER of the mixture was equal or bigger than 0. It is concluded that there was no advantage of growing switchgrass and milkvetch under 2:1 row-replacement in semiaird hilly-gully region of Loess Plateau if total biomass production is the primary purpose.