Limited nutrient availability is one of the major challenges in organic farming. Little is known about nutrient budgets of organic farms, the underlying factors or effects on soil fertility. We therefore assessed farm gate nutrient budgets for nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and sulfur (S) of 20 organic farms in Germany and analyzed their soil nutri-ent status. In average, the budgets showed a surplus of N (19 kg ha−1), K (5 kg ha−1), S (12 kg ha−1), and Mg (7 kg ha−1), and a deficit of P (−3 kg ha−1). There was, however, high variability between farms (e.g. standard deviation up to ± 36 kg N ha−1), which was mainly explained by different degrees of reliance on biological N fixation (BNF) as N source. When farms obtained more than 60% of their N input through BNF, they had deficits of P (mean −8 kg P ha−1) and K (mean −18 kg K ha−1). Nutrient status of most soils was within the ad-vised corridor, but for P, K and Mg, 10–15% of fields were lower and 45–63% were higher than advised. Extractable soil nutrient contents did not correlate with the nutrient budgets, inputs or outputs. Only extractable soil P increased with increasing P inputs and outputs. Fur-thermore, a decrease in extractable soil P was detected with a prolonged history of organic farming, indicating a risk of soil P mining in organic farming systems. In conclusion, the study revealed nutrient imbalances in organic farming and pointed to P and K scarcity as a major challenge for organic farms with high reliance on BNF in the long term.

养分供应有限是有机农业的主要挑战之一。关于有机农场的营养预算，对土壤肥力的潜在因素或影响知之甚少。因此，我们评估了德国20个有机农场的氮，磷，钾，镁和硫的养分预算，并分析了它们的土壤营养状况。平均而言，预算显示盈余为N（19 kg ha-1），K（5 kg ha-1），S（12 kg ha-1）和Mg（7 kg ha-1），而赤字为P（-3千克ha-1）。但是，不同养殖场之间存在很大差异（例如，标准偏差最大为±36 kg N ha-1），这主要是由于对生物固氮（BNF）作为氮源的依赖程度不同所致。当农场通过BNF获得超过60％的氮投入时，他们有P（平均-8 kg P ha-1）和K（平均-18 kg K ha-1）的赤字。大多数土壤的养分状况都位于建议的走廊内，但对于磷，钾和镁，建议的土壤田地要低10-15％，土壤田地要高45-63％。可提取的土壤养分含量与养分预算，投入或产出不相关。随着P输入和输出的增加，仅可提取土壤P增加。此外，随着有机耕作历史的延长，可提取的土壤P减少，这表明有机耕作系统中存在土壤P开采的风险。总之，该研究揭示了有机农业中的养分失衡，并指出磷和钾的缺乏是长期依赖BNF的有机农场的主要挑战。低于建议值的地区占10-15％，高于建议值的地区45-63％。可提取的土壤养分含量与养分预算，投入或产出不相关。随着P输入和输出的增加，仅可提取土壤P增加。此外，随着有机耕作历史的延长，可提取的土壤P减少，这表明有机耕作系统中存在土壤P开采的风险。总之，该研究揭示了有机农业中的养分失衡，并指出磷和钾的缺乏是长期依赖BNF的有机农场的主要挑战。低于建议值的地区占10-15％，高于建议值的地区45-63％。可提取的土壤养分含量与养分预算，投入或产出不相关。随着P输入和输出的增加，仅可提取土壤P增加。此外，随着有机耕作历史的延长，可提取的土壤P减少，这表明有机耕作系统中存在土壤P开采的风险。总之，该研究揭示了有机农业中的养分失衡，并指出磷和钾的缺乏是长期依赖BNF的有机农场的主要挑战。随着有机耕作历史的延长，可提取的土壤P减少，这表明有机耕作系统中存在土壤P开采的风险。总之，该研究揭示了有机农业中的养分失衡，并指出磷和钾的缺乏是长期依赖BNF的有机农场的主要挑战。随着有机耕作历史的延长，可提取的土壤P减少，这表明有机耕作系统中存在土壤P开采的风险。总之，该研究揭示了有机农业中的养分失衡，并指出磷和钾的缺乏是长期依赖BNF的有机农场的主要挑战。