Meta‐Study on Sulphur Supply and Fertilisation of Crop Species in Organic Farming of Central Europe— Part 2: Effects of S Concentration and N:S Ratio of Different Age Plant Material on DM Yield, N-Uptake, and Legume N2 Fixation

The sulphur content of the atmosphere has fallen sharply in recent decades. Due to a reduction in plant nutrition with sulphur, this has also led to a drop in the S concentrations in certain plant species over time. As a result, a lot of experimental work was carried out to remedy the emerging yield and quality deficiencies on the farms. In this summarized study, data from 98 sites in Central Europe were recorded from 1998 to 2023 received from sulphur fertiliser trials carried out on farms and experimental stations under organic farming conditions. This second part of meta-analysis focuses on establishing relationships between the status of plant nutrient supply with sulphur and DM yield responses, the nitrogen uptake of crop species and the extent of N2 fixation in legumes. Results of regression analyses based on the effect of the S concentrations and the N:S ratios of the crop species on the relative yield differences between 851 standard variants (=100%) and 1177 sulphur treatment variants. In principle, declining yield increases were determined as a result of increasing S concentrations and decreasing N:S ratios. Except in the case of grain legume young plants, both characteristics were suitable for determining corresponding limit values for yield formation. Different values were determined depending on the plant species and harvest material. In extensive comparative analyses and discussion with literature data, minimum sulphur concentrations and maximum values for N:S ratios for young plants, vegetative harvest material (straw) and grain materials are proposed to ensure optimum yields of permanent grassland, lucerne-clover-grass, grain legumes and cereals for use in practice of agricultural systems of different intensities.