Abstract
Nutrient balances are used for analysing nutrient inputs and outputs on farm or field level and are vital for establishing balanced nutrient flows, especially when looking at grassland, arable and livestock farms. For special crops such as fruit, nutrient balances are less common, partly due to the fact that nutrient input and output amounts are relatively small. Here, the authors aim to analyse nutrient flows in integrated versus organically cultivated apple orchards (N, P, K, Ca, Mg). In organic agriculture, in contrast to integrated production (IP), predominantly organic fertilizers are applied. The amounts and ratio among the nutritional elements in organic fertilizers are dynamic and difficult to calculate. Thus, the principal objective of this work was a comparison between the nutrient balances of integrated and organic farms in order to detect possible differences. The main part of this meta study consisted in summarizing and developing simple soil surface balances of 28 apple farms in South Tyrol (IT) (19 farms working according to IP-criteria and 9 organic farms), focusing on fertilization (nutrient input flow) and nutrient output flows in the form of annually harvested fruits and wood residues from substituting old trees with young trees (approximately every twenty years). Furthermore, different soil and leaf analyses conducted by the Laimburg Research Centre (South Tyrol-IT) were included in order to compare the results of the nutrient balancing with the actual nutrient supply state of the soil and the plants. Results show that the nutrient balances of the analysed integrated farms are overall similar to the balances of organically managed farms. However, differences appear for N and P. Whereas N-balances of organic farms are more positive compared to the N-balances of integrated farms, P-balances of organically managed farms are more negative than P-balances of farms managed according to IP-criteria. Soil and leaf analyses for both production systems generally indicate a nutrient supply state of the soil and plants that lies within the optimum range and for some nutrients even beyond.