Study On The Root And Shoot Growth And Interspecific Interaction Of Bothriochloa Ischaemum And Lespedeza Davurica Under Different Water And Nutrient Supply Conditions

The local dominant species of old world bluestem (Bothriochloa ischaemum) and dahurian bushclover (Lespedeza davurica) in the loess hill-gully areas of China were used to investigate under potted condition. There were three water treatments (HW: sufficient water supply; MW: moderate water stress; LW: severe water stress), three combinations of the two species (B0L12, B6L6 and B12L0) and four nutrient treatments (CK, N, P and NP). These treatments were applied after seedling establishment and remained until the end of the experiment. Biomass production and allocation, relative competitive ability and water use efficiency of the two species were investigated. The main conclusions were as follows:1. Whether in monoculture or mixtures, water stress decreased biomass production of both species and the old world bluestem was more sensitive to water deficiency. The growth of dahurian bushclover was restrained at the B6L6 combinations for each water treatment. .The N, P and NP treatments significantly improved the total biomass production of old world bluestem in monoculture or mixture conditions(P<0.05).The P and NP treatments significantly improved the total biomass production of dahurian bushclover in monoculture (P<0.05), however, no significant influence on the growth in mixture.2. The old world bluestem and bushclover had higher root: shoot ratios under each water treatment and combinations as soil water deficit increased. N, P and NP treatments significantly improved the water use efficiency of old world bluestem in monoculture or mixture conditions (P<0.05).3. In most cases, the relative yield total (RYT) values were greater than 1.0 in the mixture for each water and nutrient treatment, and the competitive ratio (CR) values also greater than 1.0. The competitive ratio values of old world bluestem tended to decrease as soil water deficit increased, while that of dahurian bushclover increased.4. Take full consideration of maximize biomass production, root:shoot ration,competitive ability, water use efficiency and its advantage for growing the two species, we suggested the order of best ratio was B6L6>B12L0>B0L12 for P,NP and CK treatments, and the order of N treatment was B12L0>B6L6>B0L12.