Optimising nitrogen (N) management improves soil fertility and reduces negative environmental impacts. Mineral N fertilizers are of key importance in intensive conventional farming (CF). In contrast, organic farming (OF) is highly dependent on closed nutrient cycles, biological N fixation and crop rotations. However, both systems need to minimise N balances and maximise nitrogen-use efficiency (NUE). NUE of organic and conventional crop production systems was evaluated in three regions in Germany by analysing N input, N output and N balance of 30 pairs of one OF and one CF farm each from the network of pilot farms for the period 2009–2011; indicators were calculated using the farm management system REPRO. CF had higher N input in all farm pairs. In 90% of the comparisons, N output of CF was higher than OF, in 7% it was the same and in 3% lower. NUE was higher in 60% of the OF, the same in 37% and lower in only 3%. The NUE of crop production in OF was 91% (arable farms: 83%; mixed/dairy farms: 95%) and the NUE in CF was 79% (arable farms: 77%; dairy farms: 80%). N balance was lower in 90% of the OF. The yearly average N balance was four times higher in CF (59 kg N ha⁻¹ a⁻¹) than in OF (15 kg N ha⁻¹ a⁻¹). The results show a huge individual variability within OF and CF. Organic mixed/dairy farms had the lowest N balances and the highest NUE. A further expansion of OF area can help to reduce high N balances and increase the NUE of crop production.

Although scientists have been researching the impacts of organic agriculture on the environment and animal welfare for decades, the conclusions drawn by the scientific community remain controversial. Against this background, this paper provides a comprehensive assessment of the benefits of organic farming in both areas by analysing results of all relevant scientific comparative studies between organic and conventional farming that have dealt with this topic over the last thirty years. So far, this study is the largest one of its kind and the first one that adds the aspect of animal welfare to a comprehensive array of impact categories. The systematic review of the scientific literature from pairwise comparisons found that organic management showed clear advantages over conventional management in the fields of environmental protection and resource conservation, which can be mainly explained by the system approach pursued in organic farming. No clear conclusion was drawn regarding animal welfare indicating that farm-specific management factors are of greater importance than the production system (organic vs conventional). Consequently, organic farming may contribute to solving current environmental and resource challenges and is rightly considered a key approach for sustainable land use. The positive effects should be further strengthened by decreasing the yield gaps between organic and conventional farming, i.e. by improving yields based on organic principles as well as by altering their relevance through changes in consumption as feed for livestock and food for humans.

Sustainable and efficient energy use in agriculture helps tackle climate change by reducing fossil energy use. We evaluated German farming systems by analysing energy input and output. Data from 30 organic and 30 conventional farms (12 arable, 18 dairy farms each) between 2009 and 2011 was used. Energy input, output, and the influence of farm type, farm structure, and management intensity on energy-use efficiency (EUE) were analysed for crop production using the farm management system REPRO. Conventional farms (CF) always had higher energy input. The energy input for organic farms (OF) was 7.2 GJ ha⁻¹ and for CF 14.0 GJ ha⁻¹. The energy output of CF was also higher. Reductions were higher in energy input than in energy output. In 73.3% of the farm pairs, OF were more energy efficient than CF. The EUE was comparable with CF on 10% of OF and for 16.7% of CF the EUE was higher suggesting better fossil energy utilization. EUE can be increased when reducing fossil energy inputs through more efficient machinery, reduction of agrochemicals, precision farming, the use of renewable energy or energy retention, and by increasing yields. A reduction of inputs is urgently required to lower the (political) dependence on fossil energy.

Grass–legume mixtures are suitable for crop rotations under organic farming. Little attention has been paid to seasonal development of mixtures with alfalfa under field conditions. We investigated the effects of site and cut on herbage and belowground biomass yields of grass–legume mixture and on above- and belowground traits of Medicago sativa. Six sites in southern Germany were monitored during 2011. Dry matter herbage yield ranged from 9 to 16 t ha⁻¹. The total herbage yield of three cuts per year decreased from 45% to 36% and 19%. The belowground biomass in the upper 30 cm soil layer ranged from 1.7 to 3.8 t ha⁻¹.There was no seasonal trend. Diameter of the root neck and maximum order of branching of alfalfa increased during the season. The number of nodules per plant decreased from 9.5–17.0 in May to 7.5–13.0 in August. By the last cut, roots with larger diameter created smaller nodules. More branched roots created more nodules independent of their shape. Thinner roots have more active nodules. Plant height, number of stems and inflorescences per plant were higher in July and August than in May. In conclusion, a holistic analysis including above- and belowground traits should be used for the evaluation of fodder crops.

To protect the environment and reduce the impact of fertilizing on climate change, a tailored fertilization according to the needs of the plants becomes more and more important. In organic farming, the main sources of nitrogen (N) are organic fertilizers, such as compost and farmyard manure. In conventional agricultural systems, various plant sensors have already proven that they can guide efficient fertilization. Since these sensors can record the growth of the biomass growth, they can also be used in organic farming to detect the influence of various organic fertilizers on the growth of corn plants. In a field trial established in 2017, eight different organic fertilizers (biogas fermentation residue, matured farmyard manure, fresh and matured organic waste compost, fresh and matured green compost, and microbial carbonized compost) were used and applied in two different amounts (120 and 240 kg N ha⁻¹) along with an unfertilized control variant. The fertilization was applied according to the current version of the German fertilizer ordinance. In 2021, sensor measurements of the corn plants were taken at six different stages of development (from BBCH 13 to BBCH 35) with a hand-held field spectrometer using the REIP vegetation index. The measurements showed that the unfertilized control variant could be reliably recorded. Furthermore, even at early growth stages the measurements showed the differences between different composts. The results presented in this study show that sensor measurements using vegetation indices reacted sensitively to organic fertilization and can be a tool for farmers to support their decision for an adequate fertilization strategy.