Background Crop rotations with sugar beet (SB) vary in accompanying crops, affecting the organic matter input into the soil and thus the soil organic carbon (SOC) stocks. Furthermore, the impact of aboveground SB residues themselves on SOC stocks is unclear. Aims The aims of this study were to analyze the effects of three SB rotations and different amounts of SB residues on SOC stock development. Methods In a field experiment started in 2006, three different SB crop rotations [(1) SB-winter wheat (WW)-WW, (2) SB-WW-silage maize (SM), and (3) SB-WW-winter oilseed rape (WOR)-WW-WW-grain pea (GP)] were sampled for SOC stocks in 0-10, 10-20 and 20-30 cm soil depth in spring of 2018 and 2019. Further plots with an SB-WW-WW rotation received either no or the doubled amount of aboveground SB residues and were sampled as described above. Results After four rotations, doubled SB residues led to significantly higher SOC stocks in 0-10 cm depth compared to the removal of SB residues. However, the effect was relatively low with 12% of the added residue-C being recovered in the soil. Comparing different SB crop rotations, SOC stocks in 0-20 cm depth were significantly higher in the SB-WW-WW compared to the SB-WW-SM rotation, while the SB-WW-WOR-WW-WW-WW-GP rotation was intermediate. Differences in SOC stocks were likely due to the different amounts and possibly quality of crop residue C input. Conclusion In total, the accompanying crops rather than the share of SB seem to be decisive for SOC development in SB rotations.

In agroecosystems, temporal diversification creates a sequence of short-lived habitats through time. Crop species as well as the diversity of crops grown in sequence might affect soil biodiversity and nutrient cycling processes. In the present study, we focused on a long-term crop rotation established in 2006 in Lower Saxony, Germany on a Luvisol. Winter wheat (WW) and silage maize (SM) were grown in continuous cultivation as well as in rotations. WW rotations span up to six years (including silage maize, sugar beet, winter rape and/or grain pea). Over two years, microbial biomass carbon (MBC) as well as kinetics (Michaelis-Menten V-max and K-m) of extracellular hydrolytic enzymes (beta-glucosidase (BG), N-acetyl-beta-glucosaminidase (NAG) and acid phosphomonoesterase (AP)) were measured in topsoil (0-10 cm depth) three times during the growing season. Continuous wheat increased soil microbial parameters compared to continuous maize as indicated by the higher microbial biomass to soil organic carbon ratio and higher potential enzymes activities involved in the C- and N-cycles (V-max of BG and NAG). The efficiency of these enzymes was lowest in continuous maize (highest K-m of BG and NAG). Maize and sugar beet as preceding crop of WW significantly decreased MBC in the 1st year but not in the 2nd year WW. Sugar beet decreased BG activity as well as its substrate affinity (increased K-m). The effect of sugar beet on MBC and enzyme kinetics depended on the preceding crop and lessened with grain pea as the preceding crop. Soil microorganisms in the wheat phase benefited from winter rape as the preceding crop, shown by an increased biomass and efficiency to turn over chitin and peptidoglycan (decreased K-m of NAG). Differences between cultivated crops, cropping history and fluctuations within the year in soil microbial biomass and enzyme kinetics are shown. (C) 2021 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

In Germany, the guidelines for variety trials with sugar beet require plots with 80–100 beets for a representative estimation of root yield. If possible, one or two head rows shall be planted perpendicular to the plots to avoid border effects at open alleys. The optimum sample size was determined in the 1970s and the effect of head rows has not yet been systematically studied. The aim of the present study was to quantify the effects of sample size and head rows on the precision of yield and quality data of sugar beet. Two series of field trials were carried out in Germany in 2016–2017. In the series “sample size”, conducted at 9 environments, samples of 30, 60, 90 and 120 beets were compared. With increasing number of beets, coefficients of variation and least significant differences for yield and quality parameters decreased, especially when the sample size was increased from 30 to 60 beets. Compared to the current standard of 90 beets, the precision of samples with 60 beets was similar for sugar content but lower for root yield. It is concluded that the current sample size should not be reduced. In the series “head rows”, ten variety trials were conducted without and with head rows. The precision of trials with and without head rows did not differ in general. The effect of head rows on least significant differences for root yield and sugar content was not consistent among environments. With head rows, absolute root yield (tonnes per ha) was lower and sugar content was higher than without, but the rank of varieties in relative white sugar yield remained unchanged. Sugar beet varieties can thus be tested in trials with and without head rows without losing precision, even within the same trial series.

Im integrierten Pflanzenschutz kommt der Fruchtfolge als vorbeugende Maßnahme zur Kontrolle von Krankheiten und Unkräutern eine hohe Bedeutung zu. Der Wechsel von Halm- und Blattfrüchten bzw. Sommerungen und Winterrungen soll dem Aufbau einseitiger Unkrautpopulationen entgegenwirken. Im Systemversuch Fruchtfolge in Harste sollte daher der Einfluss unterschiedlicher Fruchtfolgen auf die Verunkrautung in Zuckerrüben (ZR) und Winterweizen (WW) in nachfolgenden Fruchtfolgen geprüft werden (untersuchte Fruchtfolgefelder sind mit* gekennzeichnet): 1.) ZR*-WW*-WW, 2.) WW*-Monokultur, 3.) Silomais (SM)-WW*-WW, 4.) Winterraps (WRa)-WW*-WW, 5.) ZR*-WW*-SM und 6.) ZR*-WW*-WRa-WW-WW-Körnererbse (KE). Hierzu wurden im Frühjahr 2018 unbehandelte Boniturparzellen angelegt und nach Abschluss der Herbizid-Maßnahmen die artspezifische Abundanz und die oberirdische Trockenmasse bestimmt. In ZR wurde eine signifikant höhere Gesamtunkrautabundanz und -trockenmasse in der Fruchtfolge ZR-WW-WRa-WW-WWKE gegenüber der Fruchtfolge ZR-WW-WW vorgefunden. In der Fruchtfolge ZR-WW-WRa-WW-WW-KE wurde zudem eine signifikant höhere Abundanz an MATCH und eine signifikant höhere Trockenmasse an STEME nachgewiesen als in der Fruchtfolge ZR-WW-SM. Die Fruchtfolge ZR-WW-SM wies tendenziell den geringsten Shannon-Index der Unkrautabundanz auf, was auf eine Dominanz von ECHCG zurückzuführen ist. Die Fruchtfolge ZR-WW-WRa-WW-WW-KE wies tendenziell das diverseste Unkrautspektrum auf. In WW war die Gesamtunkrautabundanz nach der Vorfrucht WRa signifikant am höchsten. Unterschiede in der Unkrauttrockenmasse und im Shannon-Index waren geringer und nicht signifikant.

Agricultural landscapes are globally dominated by monocultures under intensive management. This is one of the main reasons for biodiversity loss and insect population decline in many regions all over the world. Agroecosystem biodiversity in these areas can be enhanced by cropping system diversification, such as crop rotations. Yet, long-term studies on effects of crop rotations on aboveground agrobiodiversity are lacking. We set up a 10-year long-term crop rotation experiment in Central Germany and monitored the temporal dynamics of aboveground arthropods over a full cultivation period to investigate influence of current and preceding crop identity and cropping system diversification on activity density, species richness, and community structure. We found that species composition was strongly influenced by currently grown crop although effect on arthropods varied between species groups. Especially, winter oilseed rape strongly affects arthropod community structure. Interestingly, we were also able to show an influence of the preceding crops, indicating an ecological memory effect in the aboveground arthropod community. Our results show that crop identity of both currently and previously grown crops in crop rotations may lead to an increase in arthropod activity density and changes in species composition. Diversified crop rotations including appropriate crops can be an easily implemented tool to increase arthropod biodiversity and biomass at large spatial and temporal scales, particularly in areas dominated by a single crop (e.g., wheat, maize). Our results may help to design optimized crop rotations for large-scale enhancement of insect biodiversity in agroecosystems.

The crop rotation (CR) trial at Harste was set up in 2006 to investigate the influence of varying CR (mustard (Mu)_ sugar beet (SB)-winter wheat (WW)-WW, SB-WW-Mu_silage maize (SM) and Mu_SB-WW-winter oilseed rape (WOR)WW-WW-phacelia (Ph)_grain pea (GP) on sugar beet (SB). SB yield increased in the order SB-WW-Mu_SM, Mu_SB-WW-WW and Mu_SB-WW-WOR-WW-WW-Ph_GP. However, the differences were not statistically significant in any investigation period. Main causes for high SB yield in CR Mu_SB-WW-WOR-WW-WW-Ph_GP were a high N-binding and N-supply potential as well as an improvement of soil fertility. Thus, the mineral N-fertilizer amount could be reduced and energy- and N-efficiency increased. In addition, CR SB-WW-Mu_SM was superior compared to Mu_SB-WW-WW in terms of energy- and land use efficiency as well as greenhouse gas emission. This was due to the high biomass production. However, it was not possible to ensure adequate soil organic matter supply via the crop and root residues remaining on the field in CR SB-WW-Mu_SM. For future research, there are pending issues regarding the economic viability of the entire CR and the CR impact on biodiversity.

Der im Jahr 2006 angelegte Systemversuch Fruchtfolge (FF) in Harste prüft den Einfluss unterschiedlicher Fruchtfolgen (Senf (Sf)_Zuckerrüben (ZR)-Winterweizen (WW)-WW, ZR-WW-Sf_Silomais (SM), Sf_ZR-WW-Winterraps (WR)-WW-WW-Phacelia (Ph)_Körnererbse (KE)) auf den ZR-Ertrag. Der ZR-Ertrag stieg in der Reihenfolge ZR-WW-Sf_SM, Sf_ZR-WW-WW und Sf_ZR-WW-WR-WW-WW-Ph_KE, wobei die Differenzen nicht in allen Untersuchungszeiträumen statistisch gesichert sind. Maßgeblich für den hohen ZR-Ertrag in Fruchtfolge Sf_ZR-WW-WR-WW-WW-Ph_KE sind ein hohes N-Bindungs- und Nachlieferungspotenzial sowie eine Verbesserung der Bodenfruchtbarkeit. So konnte die mineralische N-Düngemenge reduziert und die Energie- und N-Effizienz gesteigert werden. Hinsichtlich der Energie- und Flächenbilanz sowie Treibhausgasemissionen ist aber auch die Fruchtfolge ZR-WW-Sf_SM aufgrund der hohen Biomasseproduktion der Fruchtfolge Sf_ZR-WW-WW überlegen. Eine ausreichende Versorgung des Bodens mit organischer Substanz über die auf dem Feld verbleibenden Ernte- und Wurzelrückstände ist in der Fruchtfolge ZR-WW-Sf_SM nicht gewährleistet. Insgesamt zeigen die Ergebnisse, dass bei günstiger Fruchtfolgenstellung von ZR Umweltbeeinträchtigungen ohne Ertragsverluste reduziert werden können. Offene Fragen bestehen hinsichtlich der Wirtschaftlichkeit bei Betrachtung der gesamten Fruchtfolge und bezüglich der Auswirkungen der Fruchtfolgen auf die Biodiversität.

Das Herbizid Conviso One mit den beiden Wirkstoffen Foramsulfuron 50 g l-1 und Thiencarbazone-Methyl30 g l-1 (HRAC-Gruppe B) benotigt im Zuckerrubenanbau komplementar eine resistente Sorte(sortenspezifische Selektivitat). Erfahrungen mit diesen Wirkstoffen in Mais zeigen, dass eine hohe Wirksamkeitauch bei Unkrautern in spateren Wachstumsstadien gegeben ist, wahrend die bisher im Zuckerrubenanbaueingesetzten Herbizide die hochste Effizienz im Keimblattstadium der Unkrauter haben. Um Erkenntnissebezuglich der Wirkdauer im Boden, der Sensitivitat von Unkrautern in verschiedenen Wachstumsstadien unddes optimalen Einsatztermins zu gewinnen, wurden in den Jahren 2013 und 2014 vom Institut furZuckerrubenforschung mehrere Feldversuche angelegt. Dabei wurden Unkrauter der Arten Chenopodiumalbum, Brassica napus, Galium aparine, Matricaria chamomilla und Polygonum convolvulus ausgesat, um dieBodenwirksamkeit (Applikation vor Aussaat der Unkrauter) sowie die Wirksamkeit nach Spritzapplikation inunterschiedlichen Stadien der Unkrauter zu testen. Weitere Versuche auf Praxisflachen unter standorttypischerVerunkrautung dienten zur Ermittlung der Wirksamkeit von Conviso One gegenuber einer sowie gegenuber Tankmischungen und Spritzfolgen unter Zugabe von Conviso One. DieErgebnisse zeigen eine abnehmende Wirksamkeit mit zunehmenden Entwicklungsstadien der Unkrauter, vorallem bei C. album. Im Vergleich zu praxisublichen Herbizidstrategien, die eine erste Behandlung imKeimblattstadium der Unkrauter vorsehen, kann bei Conviso One ein wirksamer Einsatz bis BBCH 14 von C.album erfolgen. Verglichen mit einer Standard-Herbizidstrategie kann durch den Einsatz von Conviso One einehohere Wirksamkeit gegenuber schwer bekampfbaren Unkrautarten wie Mercurialis annua und Durchwuchs-Kartoffel (Solanum tuberosum) erreicht werden und die Anzahl der notwendigen Spritzapplikationen sinkt. DieBodenwirksamkeit betrug im Mittel der Versuche und Jahre 15-20 Tage.

The ALS-inhibitor herbicide Conviso One (foramsulfuron 50 g L-1 + thiencarbazone-methyl 30 g L-1, HRAC B) requires a corresponding resistant variety when used in sugar beet cultivation. Experiences with these active ingredients in maize show a high efficacy even at later development stages of weeds, whereas active ingredients applied in current sugar beet cultivation cause highest efficacy at the cotyledonous stage. To acquire insights concerning soil activity, sensitivity of weeds at various development stages and the optimum application timing of Conviso One, numerous field trials were conducted in 2013 and 2014 by the Institute of Sugar Beet Research, Gottingen. Weed plants of the species Chenopodium album, Brassica napus, Galium aparine, Matricaria chamomilla and Polygonum convolvulus were sown to test soil activity (application prior to sowing of weeds) and efficacy after spraying at various development stages of weeds. Additional field trials on naturally infested sites built the basis to investigate efficacy of Conviso One compared to standard herbicides and compared to combinations of Conviso One and standard herbicides in spraying sequence or tank mixture. The results indicate decreasing efficacy when development of weeds increases, especially for C. album. Compared to current herbicide strategies, which require application at the cotyledonous stage of weeds, effective application of Conviso One can take place until BBCH 14 of C. album. Conviso One caused higher efficacy against difficult to control weeds as Mercurialis annua and volunteer-potato (Solanum tuberosum) than the standard herbicide treatment and the number of applications decreased. Soil activity lasted 15-20 days on average of the field trials.

The study delivers values on greenhouse gas (GHG)-emission via cultivation of silage maize and sugar beet and of GHG-saving potential of electricity produced from biogas out of both biomass crops. Data are based on three rainfed crop rotation field trials in Germany (2011-2014) representative for Central Europe and can serve as default values. It was found that GHG-emission via crop cultivation was driven mainly by nitrous oxide emission from soil and mineral N-fertilizer use and was 2575-3390 kg carbon dioxide equivalents (CO(2)eq) per hectare for silage maize and 2551-2852 kg CO(2)eq ha(-1) for sugar beet (without biogas digestate application). Integrating a GHG-credit for surplus N in the biogas digestate reduced total GHG-emission via crop cultivation to 65-69% for silage maize but only to 84-97% for sugar beet. The GHG-saving potential of electricity production from biogas was calculated for three biogas plants differing in technical characteristics. The GHG-saving potentials were generally > 70% (silage maize: 78-80%, sugar beet: 72-76%) and the authors concluded that the technical setting of the biogas plant had a slight impact only. Overall, the authors assumed that the major potential for GHG-emission's reduction along the bioenergy production chain were N-management during crop cultivation and methane losses at the biogas plant. Finally, sugar beet, if cultivated in crop rotation, was shown to be an efficient alternative to silage maize as a biomass crop in order to achieve a higher diversity in biomass crop cultivation. (C) 2017 Elsevier Ltd. All rights reserved.

Der Beitrag fasst den bisherigen Kenntnisstand aus Publikationen zur Wirksamkeit des Herbizides Conviso One (Wirkstoffe: Foramsulfuron und Thiencarbazone-methyl, beide ALS-Inhibitoren) im Zuckerrübenanbau zusammen. Die Ergebnisse zeigen im Vergleich zu den bisher genutzten Herbiziden eine hohe Wirksamkeit auch bei höheren Entwicklungsstadien der Unkräuter. Begrenzend ist dabei das Entwicklungsstadium von Chenopodium album, welcher bis BBCH 14 wirksam bekämpft werden kann. Weiterhin kann die Bodenwirksamkeit mit durchschnittlich ca. 15 Tagen das Intervall zwischen den Applikationen verlängern. Conviso One hat eine hohe Wirksamkeit gegenüber einigen schwer bekämpfbaren Unkrautarten wie Mercurialis annua oder Durchwuchskartoffel (Solanum tuberosum) sowie eine Wirkung gegen Gräser. Spritzfolgen und/oder Tankmischungen aus klassischen Herbiziden und Conviso One erreichen unter verschiedenen Umweltbedingungen den höchsten Wirkungsgrad und sind insbesondere wegen des hohen Resistenzrisikos der beiden Wirkstoffe zur Vermeidung von Resistenzen zu bevorzugen.

This paper summarises the current state of knowledge on efficacy of the herbicide Conviso One (active ingredients: foramsulfuron and thiencarbazone-methyl, both ALS-inhibitors) in sugar beet cultivation. The results published to date show high efficacy even at higher developmental stages of the weeds in comparison to the use of current herbicides. The limiting factor is the developmental stage of Chenopodium album, which can be effectively controlled up to BBCH 14. Furthermore, soil activity lasts ca. 15 days enabling a prolonged interval between applications. Conviso One has high efficacy against some troublesome weeds such as Mercurialis annua or volunteer potatoes (Solanum tuberosum) and is also able to control grass weeds. Spraying sequences and/or tank mixes of current herbicides and Conviso One achieved highest efficacy under various environmental conditions. They should be preferred to solo applications due to the high risk of resistance development in both active ingredients.

In a holistic methodological approach, we linked field trial data with different modeling approaches to answer the question if sugar beet roots offer an ecological and economical efficient alternative to silage maize as a substrate for biogas production. Field trials were conducted at highly productive sites in Germany, representative for Central Europe, and tested both biomass crops in continuous cultivation and in crop rotations with winter wheat. In these trials, estimated methane yield of silage maize was generally higher (6837 to 8782Nm3ha−1 a−1) than of sugar beet roots (3206 to 7861Nm3ha−1 a−1) and both biomass crops reached highest yield in crop rotations. Under the nonobservance of technical effects, substrate production costs (€ per Nm3 methane) were higher for sugar beet roots and a nationwide modeling showed that, in most of the German districts, it would need to be reduced by 10 to 25% in order to reach economical competitiveness with silage maize. However, at a farm level, sugar beet for biogas production was economically advantageous when introduced with a share of 10 to 16% into the individual farm's cultivation program mainly due to high yield stability reducing the economical risk. However, a decrease in gross margin (€ ha−1) was likely to occur. In the field trials, different ecological impacts of crop cultivation were assessed but did not highlight one of the two biomass crops in comparison. However, it was evident that cultivating them in three years long crop rotations with two years of winter wheat provoked lower risks of loss of soil organic matter (−122 to −20kg humus-C ha−1 a−1) or N-leaching (40 to 62kgNha−1 in three years) than in continuous cultivation. In contrast, the continuous cultivation of silage maize and sugar beet showed lower greenhouse gas emission (7652 to 11,074kg C-dioxide-equivalents ha−1 in three years) than the crop rotations with winter wheat. Overall, we conclude that sugar beet roots can offer an efficient alternative to silage maize as a substrate for biogas production. However, to raise sugar beet's competitiveness, dry matter yields should be increased without increasing production costs and ecological impacts.

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. (C) 2016 Elsevier B.V. All rights reserved.

Since silage maize is the main crop grown for biogas production (biomass crop) in Germany; its increasing cultivation is critically discussed in terms of social and agronomical aspects. To investigate if sugar beet is suitable as an alternative biomass crop to silage maize; three-year field trials with both biomass crops in rotations with winter wheat (food crop) and continuous cultivation were conducted at three highly productive sites. Dry matter (DM) yield per hectare was measured via field trials whereas methane yield per hectare was estimated via a calculation. Higher annual DM yield was achieved by silage maize (19.5–27.4 t∙ha−1∙a−1) compared to sugar beet root (10.7–23.0 t∙ha−1∙a−1). Dry matter yield was found to be the main driver for the estimated methane yield. Thus; higher estimated methane yield was produced by silage maize (6458–9388 Nm3∙ha−1) with overlaps to sugar beet root (3729–7964 Nm3∙ha−1). We; therefore; classify sugar beet as a suitable alternative biomass crop to silage maize; especially when cultivated in crop rotations with winter wheat. Additionally; we found that the evaluation of entire crop rotations compared to single crops is a more precise approach since it includes rotational effects.

In order to quantify the influence of land use systems on the level of soil organic matter (SOM) to develop recommendations, long-term field studies are essential. Based on a crop rotation experiment which commenced in 1970, this paper investigated the impact of crop rotations involving increased proportions of sugar beet on SOM content. To this end, soil samples were taken in 2010 and 2012 from the following crop rotation sequences: sugar beet-sugar beet-winter wheat-winter wheat (SB-SB-WW-WW = 50%), sugar beet-sugar beet-sugar beet-winter wheat (SB-SB-SB-WW = 75%), sugar beet-grain maize (SB-GM = 50%) and sugar beet-monoculture (SB = 100%); these were analysed in terms of total organic carbon (TOC) and microbial biomass carbon (MBC) content, MBC/TOC ratio and the TOC stocks per hectare. In addition, humus balances were created (using the software REPRO, reference period 12 years) in order to calculate how well the soil was supplied with organic matter. In the field experiment, harvest by-products (WW and GM straw as well as SB leaves) were removed. After 41 years, no statistically significant differences were measured between the crop rotations for the parameters TOC, MBC, MBC/TOC ratio and the TOC stock per hectare. However, the calculated humus balance was significantly affected by the crop rotation. The calculated humus balance became increasingly negative in the order SB-SB-WW-WW, SB-SB-SB-WW, SB monoculture and SB-GM, and correlated with the soil parameters. The calculated humus balances for the reference period did not reflect the actual demand for organic matter by the crop rotations, but instead overestimated it. (C) 2015 Elsevier B.V. All rights reserved.

In Central Europe, various plant species including large-grain legumes and their mixtures are grown as catch crops, particularly between grains harvested early and subsequent summer crops. This article investigates the question of how soil structure in the topsoil is influenced when catch cropping with large-grain legumes (experimental factor A: without catch crop, with catch crop) under different ploughless tillage conditions during catch crop seeding (experimental factor B: deep tillage/25-30 cm, shallow tillage/8-10 cm). Five one-year trials were performed using standard machinery at various sites in Germany. Soil core samples extracted from the topsoil in the spring after catch crop cultivation served to identify air capacity, saturated hydraulic conductivity and precompression stress. The above-ground and below-ground biomass yields of the catch crops were also determined at most of the sites. In addition, the soil compaction risk for the working steps in the experiments was calculated using the REPRO model.The dry matter yield of the catch crops varied considerably between the individual trial sites and years. In particular, high levels of dry matter were able to form in the case of early seeding and a sufficient supply of precipitation. The soil structure was only rarely affected positively by catch crop cultivation, and catch crops did not contribute in the short term to loosening already compacted topsoils. In contrast, mechanical soil stresses caused by driving over the ground and additional working steps used in cultivating catch crops often led to lower air capacity in these treatments. This is consistent with the soil compaction risks calculated using the REPRO model, which were higher in the treatments with catch cropping. Catch crop cultivation also only resulted in improved mechanical stability at one location. The positive effect of deep ploughless tillage on air capacity and saturated hydraulic conductivity, however, became more clearly evident regardless of catch crop cultivation. In order for catch crop cultivation with large-grain legumes to be able to have a favourable impact on soil structure, it is therefore important that cultivating them does not result in any new soil compaction. In the conditions evaluated, deep tillage was more effective at loosening compacted topsoil than growing catch crops. (C) 2016 Elsevier B.V. All rights reserved.

Considering conventional tillage with a mouldboard plough and conservation tillage with a cultivator or disc harrow, this study analysed whether structural differences in the soil of the lower topsoil led to any difference in this layer's susceptibility to compaction, and also how density changed – in the whole soil and also in the individual aggregates – during the compaction process in both tillage variants. To this end, soil samples were taken from the lower topsoil of seven medium-term and long-term soil tillage trials conducted in Central Europe. Compression tests were performed on these samples and they were also used to determine dry bulk density, aggregate density, air capacity and saturated hydraulic conductivity. The stress/bulk density functions as well as the stress/strain functions from the compression tests were analysed and the precompression stress determined. At two test sites, compaction behaviour was analysed for whole soil and for aggregates separately. In the case of conservation tillage, the soil structure demonstrated higher dry bulk density as well as lower air capacity and saturated hydraulic conductivity. Aggregate density was mostly similar. It increased relatively slowly during compaction, and often not before high loading steps. This is why higher precompression stress values in the variants under conservation tillage were mostly the result of a dense compaction of aggregates, and indicated higher stability against mechanical loads. However, for both variants the virgin compression section of the stress/bulk density functions displayed similar compression behaviour; and generally higher settlement for conventional tillage in the compression test did not result in higher dry bulk densities than with conservation tillage. Stability against mechanical loads in the conservation tillage variants should therefore not be overestimated.