Cover crops affect the partial nitrogen balance in a maize-forage cropping system

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Rocha, Kassiano F. [UNESP]
Souza, Murilo de [UNESP]
Almeida, Danilo S. [UNESP]
Chadwick, David R.
Jones, Davey L.
Mooney, Sacha J.
Rosolem, Ciro A. [UNESP]

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Elsevier B.V.


Part of the nitrogen (N) fertilizer applied to crops is lost to the environment, contributing to global warming, eutrophication, and groundwater contamination. However, low N supply stimulates soil organic N turnover and carbon (C) loss, since the soil N/C ratio in soil is quasi-constant, ultimately resulting in land degradation. Grasses such as ruzigrass (Urochloa ruziziensis) grown as winter pasture or a cover crop in rotation with maize (Zea mays) can reduce N leaching, however, this may induce N deficiency and depress yields in the subsequent maize crop. Despite the potential to decrease N loss, this rotation may negatively affect the overall N balance of the cropping system. However, this remains poorly quantified. To test this hypothesis, maize, fertilized with zero to 210 kg N ha(-1), was grown after ruzigrass, palisade grass (Urochloa brizanta) and Guinea grass (Pannicum maximum), and the N inputs, outputs and partial N balance determined. Despite the intrinsically poor soil quality associated with the tropical Ultisol, maize grown after the grasses was efficient in acquiring N, resulting in a negative N balance even when 210 kg ha(-1) of N was applied after Guinea grass. Losses by leaching, N2O emission and NH3 volatilization did not exceed 13.8 kg ha(-1) irrespective of the grass type. Despite a similar N loss among grasses, Guinea grass resulted in a higher N export in the maize grain due to a higher yield, resulting in a more negative N balance. Soil N depletion can lead to C loss, which can result in land degradation.



Cropping system, Tropical forage, Nitrogen balance, Nitrogen loss, Nitrogen volatilization

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Geoderma. Amsterdam: Elsevier, v. 360, 7 p., 2020.