Nitrogen conservation in soil and crop residues as affected by crop rotation and soil disturbance under Mediterranean conditions |
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Authors: | A de Varennes M O Torres C Cunha-Queda M J Goss C Carranca |
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Institution: | (1) Department of Agricultural and Environmental Chemistry, Instituto Superior de Agronomia, TULISBON, Tapada da Ajuda, 1349-017 Lisbon, Portugal;(2) Kemptville Campus, University of Guelph, P.O. Box 2003, 830 Prescott St., Kemptville, ON, K0G 1J0, Canada;(3) National Agronomic Station, Avenida de República, 2784-505 Oeiras, Portugal |
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Abstract: | We investigated conservation and cycling of N under oat–oat and lupine–oat rotations in disturbed and undisturbed soil, when
roots or roots plus aboveground residues were retained. Crop residues were labelled with 15N in Year 1, and differential soil disturbance was imposed after harvest. In Year 2, plant growth, N transfer from residue
into the various sinks of the second crop (plant, soil, and residual residues), and changes in microbial activity and numbers
were determined. Oat biomass was greater after lupine than after oat due to differences in supply of N from these residues.
Buried residues of both crops appeared to decompose faster than when left on the soil surface. Lupine residues decomposed
faster than oat residues. Oat biomass was not affected by soil disturbance if grown after lupine but decreased when oat straw
was buried in the soil. More residue N was recovered from soil than from the crop. Most 15N was recovered from disturbed soil, which also had greater dehydrogenase activity and more culturable fungi. At the end of
the oat–oat rotation, 20 and 5 kg N ha−1 were derived from the roots of the first crop in undisturbed or disturbed soil, respectively. Equivalent values for the lupine–oat
rotation were 18 and 44 kg N ha−1. Returning aboveground residues provided an extra 52–80 kg N ha−1 for oat and 61–63 kg N ha−1 for lupine relative to treatments where they were removed. Over a year, lupine contributed 9 to 20 kg N ha−1 more to the agroecosystem than did oat. |
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Keywords: | Crop residues Legumes N conservation Lupine Oat Soil disturbance |
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