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Use of a systems synthesis approach to model nitrogen losses from dairy farms in south‐west England
Author(s) -
Cuttle S. P.,
Jarvis S. C.
Publication year - 2005
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.2005.00474.x
Subject(s) - leaching (pedology) , manure , ammonia volatilization from urea , volatilisation , environmental science , nitrogen , denitrification , fertilizer , ammonia , zoology , dairy farming , mathematics , agronomy , chemistry , soil water , soil science , biology , milk production , organic chemistry
Nitrogen (N) budgets were determined for six typical, moderately intensive dairy farms in south‐west England. Proportionately, only 0·12–0·17 of the N input to the farms was recovered in agricultural products, leaving annual N surpluses equivalent to 249–376 kg N ha −1 . A sequence of models (MANNER, NCYCLE and SUNDIAL) was used, together with the estimated N balance of the dairy cows and standard ammonia emission factors, to estimate N losses for each farm. Total estimated losses were equivalent to 137–220 kg N ha −1 year −1 . Leaching accounted for 0·26–0·45 of the total loss, ammonia volatilization for 0·27–0·39 and denitrification for 0·17–0·36. When residual N from manure applications was included, there appeared to be an annual accumulation of soil N, equivalent to 66–158 kg N ha −1 when averaged over the whole farm area. The amounts of N lost by leaching, volatilization and denitrification, and accumulated as soil‐N, were determined by a combination of farm properties, including N input, soil type, drainage, characteristics of the manure produced and type of fertilizer. The sum of estimated losses and change in N retained on the farm was between 0·85 and 1·11 of the N surplus (input minus output) determined from the farm budget. This suggests that losses and the change in soil‐N were underestimated on some farms and overestimated on others (by up to −50 and +23 kg N ha −1 respectively). Much of the discrepancy between estimates and the surplus was attributed to difficulties of fully integrating inputs and outputs between the different models and stages of the modelling procedure.