Association between soil organic matter and wheat yield in Humid Pampa of Argentina

The Rolling and Flat Pampas are vast plains located in Argentina. Wheat is one of the most economically important crops of these regions. Two extensive studies have been preformed to evaluate the effects of nitrogen fertilization on wheat yield at field scale. We pooled these published data to establish relationships between wheat yield and soil and climate variables under a wide range of soils and management conditions. Total soil carbon was the variable more associated with yield (r2 = 0.25). The increase in grain production expected between soils with low and high carbon levels rounded 2,200 kg ha-1. A multivariate model which included carbon in the light fraction, potential mineralizaable nitrogen, available mineral nitrogen, and rainfall was obtained, explaining 50% of wheat yield variability. These results highlight the importance of organic matter on grain production in the Humid Pampas. This effect can be due to the role of organic soil components as source of nutrients for crops.