I am building a LP model to minimise nitrate leaching in arable farming and needs to estimate nitrate leaching with respect to each crop. I will like to find out if anyone knows of any formulae or functions for estimating nitrate leaching.
Analysis of the emission of nitrate to the groundwater starts with a
balance approach for the different crops taking into account: N-input from fertiliser and manure (kg/ha), atmospheric deposition in kg N per ha/yr, crop uptake in kg/ha and evapotranspiration. Crop uptake depends on crop and on yield level. Evapotranspiration differs between fertiliser and manure and whether a cover crop is used.
Of the N-surplus assessed in this way part will denitrify. Call this share alpha; alpha depends on local conditions. The remainder is emitted to the groundwater.
The formulas are then as follows:
N leaching to groundwater below 1 metre depth = (1-alpha) * (atmospheric deposition + N-input by fertilizer and manure - crop uptake - evotranspiration)
N03- in g/l = 62/14* (kg N leaching /10*precipitation surplus)
The estimated nitrate concentration in groundwater by crop can then be added to the different production activities in the linear programming model as another environmental parameter.
See page 98 in the following publication: http://edepot.wur.nl/134639
Article Environmental-economic policy assessment: A farm economic approach
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