Digestates from cover crop, straw and cattle slurry mixtures as nutrient source in organic cropping system

Yields in organic arable farming are way below the potential. The reasons are due to the lack of nutrients and poor synchrony between nutrient availability and crop demand (Möller and Müller, 2012). Nitrogen (N) is often the most limiting nutrient for biomass production. Nitrogen available in soil is taken up by plant almost exclusively in mineral form. Yet, limitation of mineralized N in soil is often the problem especially in organic farming. In crop management systems using only organic substrates, the challenge is to increase the N mineral fertilizer value of organic substrates in order for organic farming to rely on organic fertilizer sources. Anaerobic digestion has the potential to increase the nutrients availability (Webb et al., 2013). Cover crops (CC) are useful to reduce nutrient leaching losses and they have the potential to produce extra biomass for biogas production. If a CC with symbiotic N fixation is used the CC can also contribute with extra N to the system. The biomass production in cover crops is influenced by the main crop harvest time and probably by the straw management. The aim of the current study is to quantify the influence of main crop harvest time and straw management and the inclusion of anaerobic digestion of cover crops and straw on N utilization and on potential biogas production. A comparison between mono- and co-digestion of cover crops, straw and cattle slurry is also included

Biogas production by co-ensiling catch crops and straw, effect of substrate blend and microbial communities

The combination of catch crop (CC) and barley straw(S) for biogas production was investigated in order to evaluate the ensiling process in batch assay and in continuous process. Based on two new agriculture strategies designed to produce energy and improve nutrient cycling in organic farming are being evaluated, one of them consisting on the harvest of straw and catch crop in different periods whereas the other strategy consists on harvesting them at the same time. Catch crops is promoted to reduce nutrient leaching during rainy season and straw that is not used for animal feeding or bedding is generally left in the field. Mixtures of CC and S provides several advantages: 1) Provides adequate TS for silage, 2) Absorbs the silage effluent, 3) Produces high LAB activity, and 4) Provides an optimal C/N for anaerobic digestion (AD). The effect of feeding compositions (straw or manurea ddition) on the microbial community structures were also investigated

Effect of anaerobic digestion of cover crops and straw on N and S availability in the digestate

Lack of nutrients and poor synchrony between nutrient availability and crop demand are often reasons for low yields in organic farming. A field experiment conducted in Denmark aims to use cover crops (CC) to produce extra biomass for biogas production and afterwards utilize the digestate as nitrogen (N) and sulfur (S) fertilizer. The influence of the main crop harvest time and the straw management on biomass production of cover crops is investigated. A spring barley crop and an under-sown CC (clover and chicory mixture) were established to compare early and late barley harvest time and different straw management, including a treatment with high stubble. The dry matter (DM) yield of CC in October was 2.5 t/ha for early barley harvest and 2.3 t/ha for late harvest. At early barley harvest with high stubble treatment, an extra DM yield of 1.3 t/ha was obtained. The harvested CC was ensiled and used as substrates for mono- and co-digestion with cattle manure in 15L digesters. The silages contained mixtures of CC and straw at ratios 1:0, 3:1 and 10:1 (fresh weight basis). Anaerobic digestion (AD) increased the fraction of NH4+ in total N from 0.07 to 0.41 in a reactor fed with CC silage only, for example. This increase was lower for reactors fed with higher ratio of straw in the silage mixture. In 2018, the N fertilizer value of cattle manure and different digestates and raw silages are tested in a new spring barley crop in confined microplots. Yields and N uptake of spring barley will be measured and the fertilizer value of digested materials will be compared with corresponding undigested cover crops. In addition, the fate of N and S in the soil with different cover crop-straw mixtures and digestion management will be investigated

Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko

We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low activity state. Quasi-coherent, large-amplitude ($\delta B/B \sim 1$), compressional magnetic field oscillations at $\sim$ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied comet-interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pick-up ion driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.Comment: 6 pages, 3 Figure

Inclusive V0V^0 Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table

The QCD transition temperature: results with physical masses in the continuum limit II.

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the \Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table

Co-ensiling of cover crops and barley straw for biogas production

The study investigated the effect of co-ensiling of cover crops (CC) and barley straw (BS) on biogas production. Blends containing chopped CC and BS (mix ratios of 1:0, 2:1, 3:1, 6:1; 10:1 and 19:1 (w:w)) were prepared and stored for 4 months prior to the biogas batch assay. Results show that CC is feasible for producing biogas with reasonable CH4 yield (330 mL CH4 gVS-1) and has good storability. Using of coensiling blends showed advantages over CC as it elevated the hydrolysis rate (k) from 0.024 to 0.061 d-1 and decreased the lag phase (from 5 to 0.8 days) during the thermophilic (51 C) batch test. Synergistic effects were observed from both CH4 yield and hemi-cellulose removal. The finding provided an alternative strategy for integrated straw management and CC utilization for improved biogas production

Anaerobic digestion of co-ensiled cover crop and barley straw: Effect of coensiling ratios, manure addition and impact on microbial community structure

Cover cropping is important for nutrient management of agricultural systems and has largely unexploited potential for biogas production. Co-harvest of cover crops and straw and storage as silage blends prior to biogas is promising as it could enhance the long-term storability and lead to synergies for anaerobic digestion. However, it is necessary to evaluate the feasibility of using co-ensiled blends and process optimization based on continuous test. In this study, semi-continuous thermophilic anaerobic digestion experiments were carried out with feeding of cover crop silage, co-ensiled cover crop and straw (with mixing ratios in relation to various harvest strategies) with or without addition of cattle manure. The main objective is to determine the feasibility of aforementioned mixtures for biogas production and the influence on microbial community structures in response to various feeding compositions. Results demonstrated that cover crop (silage) is feasible for digestion alone or with addition of barley straw, cattle manure or both, while manure addition led to higher CH4 yield/buffer capacity, and enhanced the volatile solids reduction. Microbial community compositions were found to have been affected by the feeding, while high straw addition led to a distinct community structure