Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2008
Publication Date: 10/1/2008
Citation: Steenwerth, K.L., Belina, K.M. 2008. COVER CROPS AND CULTIVATION: IMPACTS ON SOIL N DYNAMICS, NITROUS OXIDE EFFLUX, AND MICROBIOLOGICAL FUNCTION IN A MEDITERRANEAN VINEYARD AGROECOSYSTEM. Applied Soil Ecology. Vol. 40, Issue 2, pp370-380.
Technical Abstract: Impacts of soil tillage and cover crops on soil nitrogen (N) dynamics and microbiological function were investigated in a vineyard grown in California’s Mediterranean climate. We compared soil N dynamics, N availability and N2O emissions in a vineyard agroecosystem of two cover crops [Trios 102 (Triticale x Triosecale), (‘Trios’), Merced Rye (Secale cereale), (‘Rye’)] with cultivation (‘Cultivation’), and 2) determine seasonal effects on soil N dynamics (0-15 cm) as well as nitrification and denitrification potentials. From treatments established in Nov. 2001, soils were sampled every two to three weeks from Nov. 2005 – Nov. 2006. Gravimetric water content (GWC) reflected winter and spring rainfall. Soil temperature did not differ among treatments, reflecting typical seasonal patterns. Microbial biomass N (MBN) in spring typically was 2-3 fold greater in ‘Rye’ and ‘Trios’ than ‘Cultivation’ in spring, suggesting cover crop presence contributed to greater N retention, but these differences among treatments disappeared with decreasing soil moisture in summer. Little temporal change in soil nitrate (NO3--N) was observed, but it was consistently greater in cultivated soils. Soil ammonium (NH4+-N) in cover crop treatments was 2-3 fold greater than ‘Cultivation’ in winter and spring, increasing in all treatments in summer after cover crops had been mowed and ‘Cultivation’ had been tilled. The increase in soil NH4+-N in summer corresponded to MBN turnover and increasing N availability as measured by anaerobic potential N mineralization. N2O efflux tended to be greater from cover crop treatments, and increased in response to precipitation and cultivation. Total N2O efflux during the study was relatively low as compared to both fertilized and unfertilized annual cropping systems. Both cover crop treatments demonstrated greater capacity for potential N mineralization, nitrification and denitrification than ‘Cultivation’, and seasonal conditions (e.g., GWC) tended to encourage a predominance of denitrification or nitrification in a given season, but this was not consistent. Our study demonstrates that discrete management events and precipitation influenced soil N dynamics. In addition, the similarity in N dynamics between the cover crop treatments suggests that both cover crops have like potentials for influencing N dynamics, and augmenting MBN, nitrification and denitrification, and N availability, whereas cultivation used for weed control depresses the soil’s capacity for these processes.