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Aims
An essential task of agricultural systems is to improve internal phosphorus (P) recycling. Cover crops and tillage reduction can increase sustainability, but it is not known whether stimulation of the soil microbial community can increase the availability of soil organic P pools.
Methods
In a field experiment in southwest Germany, the effects of a winter cover crop mixture (vs. bare fallow) and no-till (vs. non-inversion tillage) on microbial P-cycling were assessed with soybean as the main crop. Microbial biomass, phospholipid fatty acids (PLFAs), P cycling enzymes, and carbon-substrate use capacity were linked for the first time with the lability of organic P pools measured by enzyme addition assays (using phosphodiesterase, non-phytase-phosphomonoesterase and fungal phytase).
Results
Microbial phosphorus, phosphatase, and fatty acids increased under cover crops, indicating an enhanced potential for organic P cycling. Enzyme-stable organic P shifted towards enzyme-labile organic P pools. Effects of no-till were weaker, and a synergy with cover crops was not evident.
Conclusions
In this experiment, cover crops were able to increase the microbially mediated internal P cycling in a non-P-limited, temperate agroecosystems.
Manures can be treated by solid–liquid separation and more sophisticated, subsequent approaches. These processes generate fertilizers, which may differ in composition and N2O release potential. The aim of the study was to investigate the influence of processing-related changes in digestate composition on soil-derived N2O emissions after application to soil. For that purpose, N2O emissions within the first 7 weeks after fertilization with two raw and eight processed digestates (derived from solid–liquid separation, drying and pelletizing of separated solid, and vacuum evaporation of separated liquid) were measured in the field in 2015 and 2016. Additionally, an incubation experiment was run for 51 days to further investigate the effect of subsequent solid and liquid processing on soil-derived N2O release. The results showed that, only in 2016, the separation of digestate into solid and liquid fractions led to a decrease in N2O emissions in the following order: raw digestate separated liquid separated solid. N removal during subsequent processing of separated solid and liquid did not significantly influence the N2O emissions after fertilization. In contrast, the concentrated application of the final products led to contradictory results. Within the solid processing chain, utilization of pellets considerably increased the N2O emissions by factors of 2.7 (field, 2015), 3.5 (field, 2016), and 7.3 (incubation) compared to separated solid. Fertilization with N-rich ammonium sulfate solution led to the lowest emissions within the liquid processing chain. It can be concluded that the input of less recalcitrant organic C into the soil plays a greater role in N2O release after fertilization than the input of ammoniacal N. Digestate processing did not generally reduce emissions but apparently has the potential to mitigate N2O emissions substantially if managed properly.
Winter wheat in northwestern Europe is often fertilized with several doses of calcium-ammonium-nitrate (CAN). For economy, farmers fertilize using a combination of N-doses. Here, we examined the necessity of N splitting (1–3) and application timing in experiments conducted in 2010 using a one-factorial fully randomized block design, and in 2011–2012 using a two-factorial split-plot design (four replicates). The study site, in southwestern Germany, had silty loam soil, and modern cultivars (2010: one cultivar, 2011–2012: three cultivars) with different genetic abilities to develop the yield components of interest were tested. A late first or single N application at stage BBCH 29/31 did not lead to differences in grain yields or protein contents compared to three N applications. However, a single N application at stage BBCH 25/27 resulted in a reduced protein content. Yield component development did not significantly differ among the cultivars. Early N application increased plant density but not yield. In two years, low plant densities were compensated by higher numbers of kernels per spike. Hence, under the tested conditions, the number of N applications could be reduced, as the high compensation ability of modern cultivars allows N fertilization consisting of two or even one application.
Conservation Agriculture (CA) is a farming system that aims to protect soil resources by promoting minimum soil disturbance in combination with the maintenance of a permanent soil cover, and diversification of crop rotation.
The aim of this study was to investigate the effects of no-till and shallow conservation tillage using a chisel plough and rotor tiller on loamy soils with high clay contents in combination with cover crop mixtures in rotations with at least three different crops. Crop yield, soil Nitrogen content and weed coverage were the main parameters measured. Experiments were performed in an on-farm approach in southwest Germany on 18 farms and two research stations over a period of 6 years. Yields of cereals, oilseed rape, maize, soybean and peas were slightly lower under no-tillage with 5.8–7.3 Mg grain yield equivalents ha− 1 than under conservation tillage with 6.3–7.8 Mg grain yield equivalents ha− 1. Cover cropping did not affect crop yields. Tillage and cover cropping had no influence on weed control in the subsequent main crop. Soil nitrate contents before winter in November were on average 11 kg N ha − 1 lower in the cover crop treatments compared to the plots without cover crops.This study shows that CA with minimum tillage had slight advantages compared to the no-till system under Southwest Germany farming conditions
Der bodenschonende Anbau von Mais wird bei Wegfall von Glyphosat deutlich schwieriger werden. Es wird sich zeigen, ob entweder Glyphosat für Standorte mit hoher Erosionsgefahr weiterhin zur Verfügung steht oder ob andere Lösungen gefunden werden, die weniger Bodenschutz bringen und/oder Ertragseinbußen nach sich ziehen.