21. Nutrient balance and share of green fields in organic farms with different production profile – Jarosław Stalenga, Jerzy Kopiński
The aim of the study was to assess the nitrogen, phosphorus and potassium balance and the percentage of green fields on arable lands in 30 organic farms of different production profile located in the Lubelskie, Podlaskie and Mazowieckie voivodeships. The studied farms were divided into three groups: as (a) specialized in crop/horticultural production, (b) specialized in animal production and (c) with no specific specialization. Each group consisted of 10 farms. In specialized farms, the dominant branch had at least 60% share in the total final gross production expressed in PLN. The surveys were carried out in the selected farms in 2010–2012 years. The studied farms were characterized by a positive nitrogen balance of 22.5 kg N ha-1 year-1. The phosphorus balance on an average was negative and amounted to -3.2 kg. It was the least negative in the animal group of farms, and the most negative in the crop/horticultural group of farms.The potassium balance was neutral and amounted to 0.4 kg K ha-1 year-1. Negative values were recorded only in the crop/horticultural farms. The share of green fields on arable lands on an average amounted to 32% what shows on the presence of desirable activities undertaken by organic farmers towards reducing nutrient losses. The nitrogen balance in the organic farms was over twice lower than in the conventional farms what indicates smaller risk of significant nitrogen losses from organic arable fields.
Keywords: organic farming, nutrient balance, green fields, specialization in agricultural production