Comparison of different tree nutrition strategies for organic apple growing: long-term and additive effects of compost N-fertilizer foliar fertilizer and bio-dynamic preparations on tree growth, yield

摘要

Organic apple growers often have yields that are 15-30 % below the average of conventional growers, and that are not explainable by losses due to insufficient plant protection measures. Thus, worldwide, a tendency can be observed that organic fruit growers are intensifying fertilization. The question is, whether this really can improve the yields and which side effects occur on fruit quality and soil. On the other hand it is stated that improving soil fertility with compost and/or bio-dynamic preparations can also stimulate nutrient mineralisation. However, quantitative data showing these single and combined effects on tree performance are scare.In an orchard with two-years old 'Topaz' apple trees on rootstock 'M27' we carried out from 2001 to 2007 a full factorial trial testing the factors i) biowaste compost (8000 kg ha~(-1),y~(-1)), ii) commercial organic N-fertilizer (10 % N; 40 kg N h~(-1),y~(-1)), Hi) foliar N-fertilizer (as molasses, 5 % N-content; 14 kg N ha~(-1),y~(-1)). In all possible combinations 9 treatments resulted. Additionally, 2 sub-treatments with bio-dynamic methods were tested: iv) application of the same compost but prepared by the bio-dynamic method with and without foliar application of the bio-dynamic preparation 500 and 501.With respect to yield, fruit weight, inner fruit quality, and mineral content of the fruits only rarely significant treatment effects occurred. Only by tendency, organic matter content, aggregate stability and microbial activity were improved in the plots receiving compost. Conclusions to optimize tree nutrition measures depending on spatial soil conditions could be drawn.