Regions in the Po Valley, Northern Italy, are characterized by intensive crop-livestock farming systems. A simulation model has been chosen, in the framework of an inter-regional project, which should help in defining groundwater vulnerability and pollution risk on a regional scale in relation to agricultural land use by allowing the prediction of nitrate leaching under different climate, soil, crop and management scenarios. The model derives from the coupling of a hydrological model, MACRO, simulating water flow and solute transport in structured soils, with a model simulating soil N dynamics, SOILN. The aim of this work was to test the model's ability to simulate nitrate leaching through soil after land spreading of pig slurries. A dataset obtained in lysimeter experiments which had been carried out in the period 1976-1981 was used for this purpose. Four soil types were compared (silty-clay, sandy-loam, loam, sand) in factorial combination with 4 rates of pig slurry (0, 142, 284, 426 g of N m-2, accumulated values from 1976 to 1979) for a 7-crop sequence. The efficiency of the MACRO model ranged from 0.96, in the sandy-loam soil, to 0.81, in the sand. Percolation was usually underestimated, the relative error ranging from +0.7 to +14.6, depending on the soil. The low efficiency of the SOILN model in simulating nitrate leaching is attributed to the lack of knowledge of the mechanisms regulating N transformation processes and especially the mineralization of pig-slurry N. This lack of knowledge hampers the correct setting of the N transformation parameter values. A remarkable improvement of the model's performances was obtained by critically manipulating a few coefficients which control the mineralization-immobilization turnover of the faeces-organic N. The model efficiency, following this re-calibration, ranged from –0.62 to +0.84, and the relative error ranged from –56 to +35, depending on soil and treatment. N leaching was underestimated at the low pig slurry-N rates and overestimated at the high ones.
|Autori:||Marchetti, R.;Ponzoni, G.;Spallacci, P.|
|Data di pubblicazione:||2001|
|Titolo:||Simulating nitrate leaching under crops fertilized with pig-slurry in lysimeters|
|Rivista:||SOIL USE AND MANAGEMENT|
|Appare nelle tipologie:||1.1 Articolo in rivista|