A pluriannual experiment was conducted at Verano (PC) to measure the yield response to N and P of irrigated grassland. A split-plot experimental design with five N treatments (100, 150, 200, 400, and 800 kg/ha N per year) and three P sub-treatments (0, 100, and 200 kg/ha P2O5 per year) was executed between 1975 and 1981, with levels of hay (dry matter) production far above those achieved with traditional applications. A Liebig response function, embodying the famous law of minimum, was chosen to represent the response relation between hay production and fertilizers. The N response is satisfactorily represented by a linear and plateau (LRP) function. The P response was estimated by means of a Mitscherlich exponential function and a fertility carryover equation which relates the quantity of available P in the soil at time t to the same quantity at t0 the accumulated additions of P and the total amounts removed by the crop. Such a Liebig response function seems to fit the data very well. The optimal P fertilizer application is computed by taking into account the price ratio, as usual, but also the amount of available P in the soil. The optimal amount of N, on the contrary, is independent of the price ratios and corresponds to the knot in the linear spline.
Funzione di risposta e fertilità residua dei prati stabili nel piacentino / P., Paris; Q., Paris; Lalla, Michele; C., Gavazzi. - In: RIVISTA DI AGRONOMIA. - ISSN 0035-6034. - STAMPA. - 17 (4):(1983), pp. 429-438.
Funzione di risposta e fertilità residua dei prati stabili nel piacentino
LALLA, Michele;
1983
Abstract
A pluriannual experiment was conducted at Verano (PC) to measure the yield response to N and P of irrigated grassland. A split-plot experimental design with five N treatments (100, 150, 200, 400, and 800 kg/ha N per year) and three P sub-treatments (0, 100, and 200 kg/ha P2O5 per year) was executed between 1975 and 1981, with levels of hay (dry matter) production far above those achieved with traditional applications. A Liebig response function, embodying the famous law of minimum, was chosen to represent the response relation between hay production and fertilizers. The N response is satisfactorily represented by a linear and plateau (LRP) function. The P response was estimated by means of a Mitscherlich exponential function and a fertility carryover equation which relates the quantity of available P in the soil at time t to the same quantity at t0 the accumulated additions of P and the total amounts removed by the crop. Such a Liebig response function seems to fit the data very well. The optimal P fertilizer application is computed by taking into account the price ratio, as usual, but also the amount of available P in the soil. The optimal amount of N, on the contrary, is independent of the price ratios and corresponds to the knot in the linear spline.Pubblicazioni consigliate
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