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(1) Background: Soil organic carbon (SOC) in agricultural soils plays a crucial role in mitigating global climate change but also, and maybe more importantly, in soil fertility and thus food security. Therefore, the influence of contrasting cropping systems on SOC not only in the topsoil, but also in the subsoil, needs to be understood. (2) Methods: In this study, we analyzed SOC content and δ13C values from a crop rotation experiment for biogas production, established in southern Germany in 2004. We compared two crop rotations, differing in their proportions of maize (0 vs. 50%) and perennial legume–grass leys as main crops (75 vs. 25%). Maize was cultivated with an undersown white clover. Both rotations had an unfertilized variant and a variant that was fertilized with biogas digestate according to the nutrient demand of crops. Sixteen years after the experiment was established, the effects of crop rotation, fertilization, and soil depth on SOC were analyzed. Furthermore, we defined a simple carbon balance model to estimate the dynamics of δ13C in soil. Simulations were compared to topsoil data (0–30 cm) from 2009, 2017, and 2020, and to subsoil data (30–60 cm) from 2020. (3) Results: Crop rotation and soil depth had significant effects, but fertilization had no effect on SOC content and δ13C. SOC significantly differed between the two crop rotations regarding δ13C in both depths but not regarding content. Annual enrichment in C4 (maize) carbon was 290, 34, 353, and 70 kg C ha−1 per maize year in the topsoil and subsoil of the unfertilized and fertilized treatments, respectively. These amounts corresponded to carbon turnover rates of 0.8, 0.3, 0.9, and 0.5% per maize year. Despite there being 50% maize in the rotation, maize carbon only accounted for 20% of the observed carbon sequestration in the topsoil. Even with pre-defined parameter values, the simple carbon model reproduced observed δ13C well. The optimization of model parameters decreased the carbon use efficiency of digestate carbon in the soil, as well as the response of belowground carbon allocation to increased aboveground productivity of maize. (4) Conclusions: Two main findings resulted from this combination of measurement and modelling: (i) the retention of digestate carbon in soil was low and its effect on δ13C was negligible, and (ii) soil carbon inputs from maize only responded slightly to increased above-ground productivity. We conclude that SOC stocks in silage maize rotations can be preserved or enhanced if leys with perennial crops are included that compensate for the comparably low maize carbon inputs. [ABSTRACT FROM AUTHOR]

Tree strips on agricultural production sites offer many economic, ecological and social advantages. However, the introduction of trees creates a transition zone between tree strips and crop land. Here, trees and crop plants compete for resources such as space, nutrients, water and light, which causes stress in the low‐competitive system. On the other hand, facilitation such as additional nutrient input through tree leaf litter and fine roots are possible. This study aims to provide indications for competition and benefits that can arise for plants growing in the transition zone of a temperate short rotation alley cropping agroforestry system (SRACS). Various climatic and plant‐growth parameters were investigated between 2013 and 2019 at different positions of an SRACS with fast‐growing poplars in northern Germany. Reduced yield of wheat, oilseed rape and silage maize close to the tree strip was associated with greater soil water tension in 30 and 60 cm soil depth due to the presence of poplar roots, reduced solar radiation due to tree shading and leaf litter coverage. In contrast, poplars growing in the outer rows produced more biomass than those in the inner rows due to the additional availability of space, light and nutrients taken from the crop field. Trees in the transition zone seem to be competitive with arable crops, but without effect on the average long‐term yield of arable crops. [ABSTRACT FROM AUTHOR]

Empirical data on energy performance (net-energy yield, energy efficiency, land demand) of biomass crop cultivation are needed for policy and agronomic decision making. Energy input and energy performance of the cultivation of silage maize (SM), sugar beet (SB), and winter wheat (WW) in crop rotations and continuous cultivation were evaluated on the basis of three field experiments on highly productive sites in Germany. Silage maize and SB root were considered as crops for biogas production and WW as a food crop. Even if SM cultivation needed the largest energy input across sites and years (19–22 GJ ha −1 a −1 ), the energy output compensated for it and largest net-energy yield (212–317 GJ ha −1 a −1 ), energy efficiency (11.4–17.1 GJ GJ −1 ), and smallest land demand (33–48 m 2 GJ −1 ) were observed. For SB cultivation, energy input (15–19 GJ ha −1 a −1 ) and energy performance were lower (119–266 GJ ha −1 a −1 , 9.1–14.7 GJ GJ −1 , 38–279 m 2 GJ −1 , respectively). Differences between both crops were significant (p ≤ 0.05), but not in all cases. Winter wheat cultivation required an energy input of 13–18 GJ ha −1 a −1 and showed the lowest energy performance (103–119 GJ ha −1 a −1 , 6.6–8.6 GJ GJ −1 , 84–102 m 2 GJ −1 , respectively). The net-energy yield and land demand values presented are among the largest and the lowest, respectively, for rainfed Central European conditions. As the preceding crops, SB induced a higher energy performance of the subsequent WW than SM. When taking such crop rotation effects into account for the overall evaluation, we concluded that SB root as a biomass crop is a suitable alternative to SM. [ABSTRACT FROM AUTHOR]

Rhizoctonia solani (AG 2-2IIIB), causing root and crown rot in sugar beet, poses an increasing problem in Europe. Agronomic measures have to be optimized to control disease and minimize yield and quality loss, because no fungicides can be applied. Resistant sugar beet cultivars have been introduced to reduce disease occurrence. Furthermore, crop rotation can influence R. solani occurrence. In contrast to other cereals, maize serves as a host of the fungus. In order to study the combined effect of these factors, a series of four field trials was established with crop rotations varying in the proportion of maize and comparing a resistant with a susceptible sugar beet cultivar in 2001-02 in southern Germany. Within crop rotations, cultivation methods were varied in the form of soil tillage, intercrops, or both. Sugar beet cultivar and crop rotation had the main impact on disease severity and sugar yield. With increasing proportion of maize, sugar yield decreased, whereas cultivation method had only a minor impact. Plowing directly before sugar beet increased sugar yield only within the unfavorable maize-maize-sugar beet rotation compared with mulching. These results give strong evidence that crop rotation of sugar beet with nonhost plants and cultivation of resistant sugar beet cultivars are adequate means for integrated R. solani control. [ABSTRACT FROM AUTHOR]

Fusarium species are common pathogens on maize and reduce the product quality through contamination with mycotoxins thus jeopardizing safety of both animal feed and human food products. Monitoring of Fusarium infected maize ears and stalks was conducted in Germany to determine the range of Fusarium species present in the field and to assess the impact of tillage, crop rotation, and weather conditions on the frequency of Fusarium species. From 2016 till 2018, a total of 387 infected ears and 190 stalk segments from 58 locations in Germany were collected. For each sample location, site-specific agronomic data on tillage and previous crops as well as meteorological data on precipitation, air temperature, and relative humidity during the vegetation period were recorded. The most frequent Fusarium species detected in maize ears were Fusariumgraminearum, F.verticillioides and F.temperatum, whereas, F.graminearum, F.equiseti, F.culmorum, and F.temperatum were the species prevailing on maize stalks. Differences in the local species composition were found to be primarily associated with weather variations between the years and the microclimate at the different locations. The results indicate that mean temperature and precipitation in July, during flowering, has the strongest impact on the local range of Fusarium spp. on ears, whereas the incidence of Fusarium species on stalks is mostly affected by weather conditions during September. Ploughing significantly reduced the infection with F.graminearum and F.temperatum, while crop rotation exerted only minor effects. [ABSTRACT FROM AUTHOR]

• A further legume can be integrated in the crop rotation by maize-bean intercropping. • The appropriate bean cultivar is crucial for the success of this system. • The intercropping yields are comparable to those of pure maize. • Maize-bean intercropping fits into organic farming systems. • Maize-bean intercropping can be adopted to moderate maritime climate. Maize-bean intercropping is currently gaining popularity among farmers in Germany, although there is hardly any data available on the yield potential under moderate maritime climate conditions in comparison to pure maize cultivation as well as on the choice of the bean cultivar. To assess the agronomic potential of maize-bean intercropping for organic farming, field-experiments over two growing seasons were conducted in Northern Germany (53°46′N, 10°30′E). A split-plot design with two sowing times of the beans as main-plot-factor and different bean species and cultivars (Phaseolus vulgaris , cv.: Cobra, Eva, Tarbais, P. coccineus , cv.: Preisgewinner, Weiße Riesen, Vicia faba cv.: Isabell) as subplot-factor was applied. In both years, the average intercropping yield (11 t ha−1 in 2011 and 14 t ha−1 in 2012) of the two sowing dates was comparable to that of maize-control, except for Maize-Eva in 2011. The highest intercropping yields in 2011 were shown by cv. Tarbais and Preisgewinner with bean shares ranging from 34% to 39%. By contrast, the late-sown beans in 2012 had a share of 6–12% only, reflecting the overall higher maize yield level. Compared to maize control, the intercropping with Tarbais and Preisgewinner, which achieved the highest leaf mass scores, led to a significant improvement in crude protein yield by 36% and 18% in 2011, respectively. Earlier ripening bean cultivars (e.g. cv. Eva and Cobra) tend to lose their leaves before harvest. So cultivars with a longer growth period (e.g. cv. Tarbais), similar to maize, should be used to achieve high bean and crude protein yields. Our results demonstrate the importance of cultivar choice for achieving high bean yields that have the potential to improve feed quality. Tarbais and Preisgewinner were the most suitable cultivars for maize-bean intercropping, as they achieved the highest bean yields and improved the crude protein yield in 2011. Even though further optimization is indispensable, we have shown that maize-bean intercropping can fit into organic farming systems under moderate maritime climate. [ABSTRACT FROM AUTHOR]

• No-tillage gains lower yield than plow tillage with sandy soil and low precipitation. • No-tillage signigicantly nagatively influences silage maize yield after 3 years. • Achieving approximate double yield by irrigation in extreme drought years. • Irrigation is the most important factor as compared to tillage and crop rotation. • Giving highest and stable yield under plowed, irrigated and crop rotation combination. To analyze the effects of tillage (no-tillage , plow tillage), irrigation (rainfed , irrigated), and crop rotation (continuous maize , 4-year crop rotation) and their development, we conducted a field experiment over 9 years under sandy soil conditions in northeastern Germany. The generalized linear model showed that tillage, irrigation and crop rotation jointly explained approximately 35% of the total variance. Irrigation and crop rotation significantly positively influenced maize biomass yield started immediately in the first years in 2008 and 2011 respectively, while tillage started to significantly positively affect yield starting from the fourth year. In general, irrigation had the most relative importance as a management factor compared to the importance of tillage and crop rotation. Crop rotation with legumes increased soil nitrogen and carbon content and led to a higher yield than continuous maize 11.1 dt ha−1 y−1 in average. Furthermore, the significant effect of crop rotation on the yield of the following crop (maize) continued after 2 cycles of a 4-year crop rotation. A significant influence of the 2-way interactions between rotation, tillage and irrigation was only found in extremely dry years. It can be concluded that (i) the negative influence of no-tillage becomes noticeable after 3 years, leading to significantly lower yield compared to plow tillage; (ii) under the sandy soil and dry conditions, irrigation significantly increases yields and is the most important factor compared to tillage and crop rotation; and (iii) crop rotation significantly increases and maintains maize yield under both plowed and irrigated conditions. [ABSTRACT FROM AUTHOR]