| In organic farming systems, the purchase of nutrients is firmly restricted as compared to conventional farming systems. This will often cause a negative nutrient budget on the field level, especially in cases with low animal density, where more nutrients are removed in yields than are applied in fertilisers. Studies on five organic dairy farms in Southern Norway, that were aiming at self-sufficiency,revealed that the concentrations of ammonium-acetate lactate (AL) soluble phosphorus (P) had decreased with time. The farms had been organically managed since 1986 or earlier. It was found that the higher the initial P-AL concentration,the greater was the decrease that occurred, calculated per year. Out of 156 topsoil samples,only 6 had low P-AL values (< 25... |
