The effect of meat and bone meal applied without or with mineral nitrogen on macronutrient content and uptake by winter oilseed rape

Meat and bone meal (MBM) can be a viable alternative to natural, organic and mineral fertilizers because it is rich in nitrogen (N), phosphorus (P), calcium (Ca), micronutrients and organic matter that can be recycled back into agricultural land. The aim of this study was to determine the optimal dose of MBM for winter oilseed rape (Brassica napus L.). Meat and bone meal was applied at three doses (1.0, 1.5 and 2.0 Mg ha-1) with the addition of mineral nitrogen at 79 and 40 kg N ha-1, and without the addition of mineral nitrogen (0 kg N ha-1), respectively. The effects exerted by MBM were compared with those exerted by mineral NPK fertilization (control treatment). Since MBM had low K content, K rate was 145 kg ha-1 in all treatments, and it was applied with mineral fertilizers. The macronutrient (N, P, K, Ca and Mg) content of winter oilseed rape seeds and straw, and macronutrient uptake by aboveground biomass were evaluated. A small-scale field experiment was conducted in northeastern Poland. The experiment had a randomized block design, and it was established on Dystric Cambisol developed from loamy sand. Changes in the uptake of the analyzed macronutrients and their concentrations in winter oilseed rape seeds and straw were affected by fertilization and weather conditions. Supplemental mineral N was applied before sowing to widen the narrow N/P ratio in MBM, which had a beneficial influence on the mineral composition and macronutrient uptake by the aboveground biomass of winter oilseed rape. Macronutrient (N, P, Ca and Mg) uptake by plants was highest in the treatment with the lowest MBM dose (1.0 Mg MBM ha-1) supplemented with 79 kg mineral N (50% N from mineral fertilizer and 50% N from MBM). The results of this study indicate that MBM applied at the dose of 1.0 t ha-1 meets the P and N requirements of winter oilseed rape in 100% and 50%, respectively. Therefore, the recommended mineral N fertilizer rate for winter oilseed rape can be reduced by 50%.