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Nitrate leaching in crop rotations with grass-clover as influenced by sward age, grazing, cutting and fertilizer regimes

Eriksen, J.; Askegaard, M. and Søegaard, K. (2012) Nitrate leaching in crop rotations with grass-clover as influenced by sward age, grazing, cutting and fertilizer regimes. Agriculture, Ecosystems and Environment, , pp. 1-12. [Completed]

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Summary

Grazing animals have profound effects on pastoral systems including nutrient removal by grazing and redistribution through excreta. Generally, in grazed pastures the conversion of consumed N into product is low and a substantial quantity of N (>70%) is recycled through the direct deposition of animal excreta. This low N utilization by grazing animals reflects the relatively high concentrations of N required for metabolic functions and optimum growth of plants compared to that needed by the grazing ruminant for amino acid and protein synthesis (Haynes and Williams, 1993). Increasing the N concentration in grass, such as by increasing the rate of N fertiliser application, can result in a substantial N surplus (i.e. N inputs – N outputs in products). For example, N surpluses of 150 to 250 kg N ha-1 yr-1 occur in highly productive dairy farm systems in the Netherlands and northern Germany (Rotz et al., 2005). Grazing cattle return N in urine patches at rates of up to about 1000 kg N ha-1, which is far in excess of plant requirements (Haynes and Williams, 1993). Urine N is in highly mineralisable forms compared to dung N, and within 3-5 days is rapidly converted to plant-available N in soil. This can result in inorganic soil N under urine patches up to 10 times greater than under dung patches, and more than 30 times greater than areas unaffected by excreta (Afzal and Adams, 1992).


EPrint Type:Journal paper
Subjects: Environmental aspects > Air and water emissions
Farming Systems > Farm nutrient management
Research affiliation: Denmark > DARCOF III (2005-2010) > ORGGRASS - Grass-clover in organic dairy farming
Deposited By: Eriksen, Senior scientist Jørgen
ID Code:20637
Deposited On:26 Mar 2012 13:40
Last Modified:01 Jun 2012 12:32
Document Language:English
Status:Unpublished
Refereed:Not peer-reviewed

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