Soil nitrogen dynamics in alley cropping and no-till systems on ultisols of the Georgia Piedmont, USA |
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Authors: | C C Rhoades T M Nissen J S Kettler |
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Institution: | (1) Institute of Ecology, University of Georgia, Athens Georgia, 30602, USA;(2) Department of Crop and Soil Sciences, University of Georgia, Athens Georgia, 30602, USA |
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Abstract: | On highly-weathered Ultisols of the Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping presents
an option for rapidly increasing soil nitrogen availability while restoring long-term soil fertility. Three years after the
establishment of Albizia julibrissin hedgerows and no-till agriculture trials, we measured inorganic soil nitrogen (NO3
-–N and NH4
-–N) and net nitrogen mineralization during a 4-month field study and a 14-day laboratory study . We also measured the influence
of tree leaf amendments on grain sorghum production and N uptake. Soil nitrate increased four-fold within two weeks of adding
Albizia leaf mulch. Soil ammonium did not increase as rapidly nor to the same extent after tree mulch addition. Averaged over
the 4-month study, soil nitrate and ammonium were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till
plots. Net nitrification and mineralization were no higher in the alley cropping plots, during either field or laboratory
incubations. Tree mulch additions enhanced crop biomass production and N uptake 2 to 3.5 times under both high and low soil
moisture conditions. Our study demonstrates the dramatic short-term impacts of Albizia mulch addition on plant available nitrogen.
Combined with no-till practices, alley cropping with Albizia hedges offers Piedmont farmers an option for reducing reliance
upon chemical N fertilizer while improving soil organic matter levels.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | Albizia julibrissin conservation tillage hedgerow intercropping nitrogen mineralization |
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