Vernachlässigte Phosphor‐ und Kaliumdüngung im ökologischen Landbau senkt die biologische Stickstofffixierung bei Rotklee und den Kornertrag bei nachfolgendem Hafer |
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| Authors: | Wilhelm Rmer Philipp Lehne |
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| Institution: | Wilhelm Römer,Philipp Lehne |
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| Abstract: | Neglected P and K fertilization in organic farming reduces N2 fixation and grain yield in a red clover‐oat rotation N2 fixation is the most important N source in organic farming. An insufficient P, K, and S supply to legumes may reduce their N2 fixation capacity. Consequently, the total yield of plant production may also be reduced. This problem was studied in a pot experiment with red clover followed by oat. Soil was taken from a field where organic farming had been practiced for more than 30 years without applying any mineral fertilizers or buying additional fodder. The soil (luvisol from loess) was characterized by: pH (CaCl2) 5.4; lactate‐soluble (CAL) P 5 mg kg–1 and K 110 mg kg–1. 6 kg dry soil were mixed with 400 mg P applied as (i) triplesuperphosphate (TSP), (ii) rock phosphate (RP) or (iii) compost from organic household residues (BAK). An additional treatment (iv) with TSP received 1000 mg K as K2SO4 (TSP+K) and an additional treatment with RP (v) received only 200 mg P (RP/2). A control treatment received no fertilizer. P application significantly improved the P nutritional status of the plants (P content) and increased the N amount in the shoots of red clover (with 400 mg P per pot by 64 % to 139 % as compared to the control) and the dry matter (DM) yield by 60 % to 130 %. No significant differences between TSP and RP were found. The application of BAK resulted in a significantly higher N yield than the application of RP and TSP. The treatment TSP+K resulted in the highest DM yield (230 %), removal of P was 343 %, of K 228 %, and of N 239 % as compared to the control plants. This indicates a synergistic effect of P, K, and S on N2 fixation, which was also found with BAK. Oat grown after red clover increased its grain yield by 132 % (200 mg P as RP) to 165 % (400 mg P treatments). This was mainly due to a higher P uptake (up to 172 %) and a higher N uptake (up to 172 %) as compared to the control. |
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| Keywords: | organic farming red clover N2 fixation oat P deficiency P fertilization K fertilization S fertilization biowaste compost |
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