Chemical and biological responses in a Mediterranean sandy clay loam soil under grain legume-barley intercropping

Grain legume-cereal intercropping can be of a great interest in Mediterranean croplands where severe climatic conditions and intensive agricultural practices exacerbate the process of soil degradation and decline of soil fertility. This study aimed to investigate the impact of leguminous intercrops in soil dynamics of various C and N pools and bacterial community structure. A field experiment including grain legume (pea, faba bean)-barley intercropping as compared to the respective sole crops (P100, F100 and B100) was carried out on a sandy clay loam soil in a Mediterranean environment. Row intercrops were established in an additive (P100/B50 or F100/B50) or replacement (P50/B50 or F50/B50) design. Soil chemical, biochemical and ecophysiological variables together with shifts in the bacterial community structure by DGGE community fingerprinting were determined at three sampling times over the cropping season. The impact of intercropped legumes upon the soil fertility status was assessed by calculating the synthetic index of biological fertility (IBF). Crop biomass production and weed suppression at the harvest stage were also determined. Results showed that the soil fertility status was not significantly increased and a few soil C and N-related biochemical variables were affected by the legume-based intercropping during the cropping season, suggesting that legume root-derived substrates stimulate microbial mineralization thus leading to an increase of the soil available-N pool. The bacterial community structure was resilient to crop treatments. Pea-barley intercropping in replacement design provided a more stable yield (in terms of aboveground biomass production) and a lower weed infestation