Nicol Stockfisch

Effects of agricultural machinery with high axle load on soil properties of normally managed fields

Abstract In a field study, conducted on 10 conventionally managed field sites in Germany, the effects of high axle loads (15–25xa0Mg) on soil physical properties were investigated. Soil texture classes ranged from loamy sand to silty clay loam. All sites were annually ploughed, and one site was additionally subsoiled to 40xa0cm depth. In the context of common field operations wheeling was performed either by a sugar beet harvester (45xa0Mg total mass, 113xa0kPa average ground contact pressure) or a slurry spreader (30xa0Mg total mass, 77xa0kPa average ground contact pressure). Soil moisture conditions varied from 3.2 to 32xa0kPa water tension during this pass. Penetration resistance was measured before the pass. Soil cores were collected in a grid scheme at each site before and after the machine passed. Bulk density, aggregate density, air-filled porosity and air permeability at seven distinct soil water tensions ranging from 0.1 to 32xa0kPa were determined in these cores taken from three layers (topsoil, plough pan and subsoil). At most sites, a pass by the sugar beet harvester or slurry spreader strongly affected topsoil properties. Bulk density and aggregate density increased while air-filled porosity and air permeability decreased. The plough pan was already severely compacted before wheeling: therefore changes were small. The subsoil showed no changes or only minor signs of compaction. Only at one site, which was subsoiled the year before, significant signs of compaction (i.e. changes in bulk density, air-filled porosity and air permeability) were detected in subsoil layers. The results show that using present-day heavy agricultural equipment does not necessarily lead to severe subsoil compaction in soils where a compacted plough pan already exists. However, fields which were subsoiled leading to an unstable soil structure are in serious danger of becoming severely compacted.

Influence of sulphur supply on yield and quality of sugar beet (Beta vulgaris L.): determination of a threshold value

Abstract In the last 20 years, several crops such as oil seed rape and cereals have developed sulphur deficiency symptoms with subsequent yield reductions due to decreasing S deposition. The study aimed at: (1) defining indicators of the S status of sugar beet; and (2) determining threshold values of internal S concentrations which affect yield and quality. For this purpose, the effect of S supply on S concentration and N/S ratio in leaves and on yield and technical quality of sugar beet was analysed. A field survey with 200 sites was conducted and S treatments were performed in 33 field trials and four pot experiments. In the field survey, the mineral S content of the soil in spring had no impact on the S concentration in sugar beet leaves in July. In accordance, there was no effect of S application on yield and quality of sugar beet in the field trials, indicating that S was available in sufficient amounts. In pot experiments, beet yield and sucrose concentration decreased, while potassium, sodium and amino N concentration in the beet considerably increased with extremely low S supply. With S concentrations above 0.3% (range of: 0.28–0.32%) in young leaf blades, which equalled N/S ratios below 20, no changes in yield or quality occurred as a result of S application, indicating that the plants were adequately supplied with sulphur. Plants from field trials and pot experiments reached maximum yields with the same S concentrations in the leaf blades. This good agreement leads to the conclusion that these threshold values do not depend on growing conditions and are, therefore, a general characteristic for sugar beet. S concentration and N/S ratio in the blades of young sugar beet leaves sampled in July are thus suggested as suitable indicators of the plant’s S status.

Crop Rotational Effects on Yield Formation in Current Sugar Beet Production – Results From a Farm Survey and Field Trials

In Europe, the framework for sugar beet (Beta vulgaris L.) production was subject to considerable changes and for the future it is expected that sugar beet cultivation might concentrate around the sugar factories for economic reasons. Based on data from a national sugar beet farmers’ survey and multi-year crop rotation trials, the effects of cropping interval (number of years in between two subsequent sugar beet crops) and of preceding crops on sugar yield were elucidated under current Central European management conditions. The dominating sugar beet cropping interval was ≥4 years in the farm survey with pronounced differences between regions. However, the cropping intervals 2, 3, and ≥4 years did not affect the sugar yield. Therefore, significant differences in sugar yield between regions were assumed to be caused by multiple interactions between year, site, and farmers’ skills. Throughout Germany, the dominating preceding crops in sugar beet cultivation were winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.). In the field trials, the sugar yield was 5% higher after pea (Pisum sativum L.) compared to maize (Zea mays L.) as preceding crop, while differences between the preceding crops pea and winter wheat, and wheat and maize were not significant. Repeated measurements of canopy development and leaf color during the growing season revealed a higher N-availability after pea as preceding crop. However, decreased growth after maize was not completely compensated for by high N-fertilizer doses. Overall, the causes for the differences in sugar yield between the preceding crops remained open. The results do not support concerns about substantial yield losses in sugar beet production due to a reduction in the cropping interval from 3 to 2 years. Nevertheless, short rotations with maize and sugar beet might increase the risk of Rhizoctonia solani crown and root rot infestation. Leguminous crops such as pea offer the potential for higher sugar beet yield with lower N-fertilizer doses.

Reaction of Sugar Beet to Boron Fertiliser Application in Pot Experiments

During the last few years, reports on boron (B) deficiency in German sugar beet crops became more frequent. Deficiency symptoms often develop after prolonged dry periods in summer.