caa a22 4500 463209206 CHVBK 20180405153135.0 cr unu---uuuuu 170326e20070901xx s 000 0 eng 10.1007/s10705-007-9094-6 doi (NATIONALLICENCE)springer-10.1007/s10705-007-9094-6 Soil aggregates control N cycling efficiency in long-term conventional and alternative cropping systems [Elektronische Daten] [Angela Kong, Steven Fonte, Chris van Kessel, Johan Six] This paper presents novel data illustrating how soil aggregates control nitrogen (N) dynamics within conventional and alternative Mediterranean cropping systems. An experiment with 15N-labeled cover crop residue and synthetic fertilizer was conducted in long-term (11years) maize-tomato rotations: conventional (synthetic N only), low-input (reduced synthetic and cover crop-N), and organic (composted manure- and cover crop-N). Soil and nitrous oxide (N2O) samples were collected throughout the maize growing season. Soil samples were separated into three aggregate size classes. We observed a trend of shorter mean residence times in the silt-and-clay fraction than macro- (>250μm) and microaggregate fractions (53-250μm). The majority of synthetic fertilizer-derived 15N in the conventional system was associated with the silt-and-clay fraction (<53μm), which showed shorter mean residence times (2.6months) than cover crop-derived 15N in the silt-and-clay fractions in the low-input (14.5months) and organic systems (18.3months). This, combined with greater N2O fluxes and low fertilizer-N recoveries in both the soil and the crop, suggest that rapid aggregate-N turnover induced greater N losses and reduced the retention of synthetic fertilizer-N in the conventional system. The organic system, which received 11years of organic amendments, sequestered soil organic carbon (SOC) and soil N, whereas the conventional and low-input systems merely maintained SOC and soil N levels. Nevertheless, the low-input system showed the highest yield per unit of N applied. Our data suggests that the alternating application of cover crop-N and synthetic fertilizer-N in the low-input system accelerates aggregate-N turnover in comparison to the organic system, thereby, leading to tradeoffs among N loss, benefits of organic amendments to SOC and soil N sequestration, and N availability for plant uptake. Springer Science+Business Media B.V., 2007 Aggregate dynamics nationallicence Long-term cropping system nationallicence Mean residence time nationallicence Plant nutrient uptake nationallicence Soil organic matter sequestration nationallicence Soil nitrogen cycling nationallicence Kong Angela Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut Fonte Steven Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut van Kessel Chris Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut Six Johan Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut Nutrient Cycling in Agroecosystems Kluwer Academic Publishers 79/1(2007-09-01), 45-58 1385-1314 79:1<45 2007 79 10705 https://doi.org/10.1007/s10705-007-9094-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10705-007-9094-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kong Angela Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut NATIONALLICENCE 700 1- Fonte Steven Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut NATIONALLICENCE 700 1- van Kessel Chris Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut NATIONALLICENCE 700 1- Six Johan Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA aut NATIONALLICENCE 773 0- Nutrient Cycling in Agroecosystems Kluwer Academic Publishers 79/1(2007-09-01), 45-58 1385-1314 79:1<45 2007 79 10705 Metadata rights reserved Springer special CC-BY-NC licence nationallicence SWISSBIB 453090222 BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer