Nitrogen and phosphorus effects on blue grama and buffalograss interactions

Abstract

Soil water availability and soil texture appear to influence the relative distribution of blue grama [Bouteloua gracilis (H.B.K.) Lag.] and buffalograss [Buchloe dactyloides (Nutt.) Engelman]. However, nutrient gradients may affect competitive interactions where the species occur together and may influence revegetation efforts in abandoned croplands. A greenhouse experiment was conducted to test whether competition between species was prevalent under relatively nutrient-rich vs. nutrient-poor conditions. Blue grama and buffalograss plants were grown in intra- and interspecific pairs under 4 nutrient regimes representing combinations of low and high availabilities of nitrogen (N) and phosphorus (P). Interspecific competition was evident only with high N and P availability. Blue grama exhibited greater aboveground biomass, increased tiller production and higher N and P contents when grown in mixture, compared to monocultures. This was accompanied with a reduction in tiller production and belowground P content in buffalograss grown in mixture. Stolon production in buffalograss was prevalent only with high P. Blue grama had greater biomass than buffalograss regardless of nutrient treatment. Blue grama appears to be more competitive than buffalograss with high nutrient availability and more stress tolerant with low fertility.