Nitrate leaching potential from arable land in Germany: Identifying most relevant factors.

Diffuse nitrogen losses from agriculture in Germany continue to cause regionally increased nitrate concentrations in groundwater. Groundwater quality monitoring cannot be a timely indicator of the effects of mitigation measures being applied in agriculture, due to frequently long transport routes and high residence times of the leachate. Instead, nitrate leaching potential is often determined at field and farm scale by monitoring soil mineral nitrogen contents at 0-90 cm depth in autumn (SMNa), i.e. before the start of the annual leachate period. In this study, we developed an understanding of the controls on the soil mineral nitrogen content at the start of winter. In an on-farm approach, extensive data was collected from 48 farms in five nitrate-sensitive regions in Germany from 2017 to 2020. From this data set, 25 management and site factors were evaluated with regard to their significance for SMNa by means of a random forest model. With the random forest regression, we identified the role of the factors on SMNa with an acceptable model accuracy with R2 = 0.56. The results show that the cultivated crop is the most important factor influencing SMNa. Potatoes, oilseed rape and maize produced the highest SMNas, whereas SMNas were lowest after spring barley, sugar beet and winter barley. Among site factors, soil type and texture as well as precipitation in October were most decisive. The effects of N fertilisation parameters such as rate and timing were masked by these site factors. The results show that the reduction of nitrogen-intensive crops in crop sequences can be a promising measure for the reduction of nitrate loads. On the other hand, our analysis makes clear that soil-related factors controlling nitrogen release and risk of leaching, as well as weather, can significantly mask the effect of cultivation.

Feed Clusters According to In Situ and In Vitro Ruminal Crude Protein Degradation.

Effective degradation (ED) of crude protein (CP) was estimated in vitro at 0.02, 0.05 and 0.08 h−1 assumed ruminal passage rates for a total of 40 feedstuffs, for which in situ ED was available and used as reference degradation values. For this, the Streptomyces griseus protease test was used. The differences between in vitro CP degradation and the in situ CP degradation values were lowest in legume grains and highest in cereal by-products and barley. The differences between in situ and in vitro ED were expressed using a degradation quotient (degQ), where degQ = (EDin vitro − EDin situ)/EDin situ. Among the tested feedstuffs, eight specific clusters were identified according to degQ for the assumed passage rates. The feedstuffs clustered in an unspecific way, i.e., feedstuffs of different nutrient composition, origin or treatment did not necessarily group together. Formaldehyde−treated rapeseed meal, soybean meal, wheat, a treated lupin, sunflower meal and barley could not be assigned to any of the clusters. Groupwise degradation (range of degQ for assumed passage rates are given in brackets) was detected in grass silages (−0.17, −0.11), cereal by-products together with sugar beet pulp (−0.47, −0.35) and partly in legume grains (−0.14, 0.14). The clustering probably based on different specific nutrient composition and matrix effects that influence the solubility of feed protein and limit the performance of the protease. The matrix can be affected by treatment (chemically, thermally or mechanically), changing the chemical and physical structure of the protein within the plant. The S. griseus protease test had reliable sensitivity to reflect differences between native feedstuffs and treatments (thermally or chemically) that were found in situ. The in situ results, however, are mostly underestimated. The clustering results do not allow a clear conclusion on the groupwise or feed-specific use of carbohydrate-degrading enzymes as pre- or co-inoculants as part of the S. griseus protease test and need to be tested for its potential to make this test more conform with in situ data.

Effect of Hay Steaming on the Estimated Precaecal Digestibility of Crude Protein and Selected Amino Acids in Horses.

Steaming hay is increasingly used to treat low-quality forage because it was proven to reduce inhalable allergens such as mould spores, bacteria, and airborne dust particles. Preliminary results have shown a substantial loss of precaecal (pc) digestibility (D) of crude protein (CP) and amino acids (AA). For this purpose, six different batches of hay from central Germany were divided into four subsamples, and each one was individually steamed. Native hay and four replicates of each steamed subsample were analysed for CP, AA, neutral detergent insoluble crude protein (NDICP), neutral detergent soluble crude protein (NDSCP) as well as pepsin insoluble CP (piCP). Based on the analytical parameters, pcD of CP, protein solubility (PS), piCP (% CP) and precaecal digestible (pcd) CP and pcdAA contents were calculated. Selected Maillard reaction products (MRP), namely furosine and carboxymethyllysine (CML), were also analysed. Steaming did not affect CP content (native = 69, steamed = 67 g/kg dry matter, DM; p > 0.05), but it had an impact on the insoluble part of CP. Thus, NDICP increased by 57% (native = 27, steamed = 42 g/kg DM; p < 0.05) and piCP by 15% overall (native = 40, steamed = 46% of CP; p < 0.05). This could be a consequence of the heat damage and the associated increase in MRP. The content of furosine rose by 67% (native = 17.6, steamed = 29.4 mg/100 g DM; p < 0.05). The content of CML increased by 120% (native = 5.1, steamed = 11.3 mg/100 g DM; p < 0.05). We chose to analyse these two MRPs because they represent the reaction products with the limiting AA lysine. In contrast, the soluble fractions of CP declined, while PS as a percentage of CP decreased by 38% as a result of the treatment, and NDSCP was reduced by as much as 41% (p < 0.05). In line with this, the steaming process decreased the pcD of CP (native = 56%, steamed = 35%; p < 0.05) and pcdCP (native = 37.9, steamed = 22.5 g/kg DM; p < 0.05), respectively. The same effects were shown for selected AA; e.g., sulphuric AA pcd methionine plus pcd cysteine decreased by 45%, pcd threonine decreased by 41%, and the limited AA pcd lysine decreased by more than 50% (p < 0.05). In conclusion, the high temperatures generated during steaming lead to protein damage and consequently to a reduction in the pcD of CP and essential AA. Nevertheless, steaming successfully reduces viable microorganisms and binds dust particles. Therefore, steamed hay is still a proper and sometimes the only possible roughage for horses suffering from respiratory diseases such as equine asthma. Essentially, horse diets based on steamed hay should be balanced accordingly.

Feed Intake Parameters of Horses Fed Soaked or Steamed Hay and Hygienic Quality of Hay Stored following Treatment.

Horses suffering from equine asthma must consume low-dust forage, with soaking and steaming being suitable methods of hay treatment. The impacts of this treated hay's subsequent storage and effects on the horses' chewing activity are largely unknown. Meadow hay was soaked (10-15 °C, 15 min) or steamed (100 °C, 60 min). Microbial counts (colony forming units (CFU)) were determined by culture before and after soaking or steaming, and subsequent storage at 10 and 25 °C for 6, 12 and 24 h (three replicates each). Six horses were fed native, soaked and steamed hay, according to a cross-over design, and chewing parameters were measured. Steaming reduced (p < 0.05) typical mold vs. soaking (0 vs. 50 CFU/g) and yeasts vs. native and steamed hay (0 vs. 102 and 90 CFU/g). Storing soaked hay elevated bacteria, mold, and yeasts (p < 0.05). Within the first 60 min of hay intake, the steamed hay and soaked hay were eaten slower (19.5 and 21.5 g dry matter/min, respectively; p < 0.05) and the steamed hay was chewed more intensely (steamed hay: 3537; native: 2622; and soaked: 2521 chewing cycles/kg dry matter, p < 0.05). Steaming particularly improves the hygienic quality of hay. Soaked hay is not stable when stored and is less accepted by horses.

Fermentation Characteristics and In Vitro Digestibility of Fibers and Fiber-Rich Byproducts Used for the Feeding of Pigs.

Dietary fibers may have positive impact on health and wellbeing of pigs. The study examined physicochemical properties of two lignocelluloses (including and excluding bark), powdered cellulose, Aspergillus niger mycelium, lucerne chaff, soybean shells, wheat bran, and sugar beet pulp in relation to fermentability and digestibility using in vitro batch-culture incubation. Maize starch and a purified cellulose were used as standardized substrates for classification of the test substrates. The substrates covered a wide range regarding their physicochemical properties. Swelling capacity (SC) was 9-411%, water binding capacity (WBC) was 4.4-14.3 g/g dry matter (DM), and water holding capacity (WHC) was 4.1-10.6 g/g DM. Gas production and other fermentation parameters-namely post-incubation pH, CH4, NH3, and short chain fatty acids (SCFA) concentrations-revealed a significant fermentation of sugar beet pulp, soybean shells, lucerne chaff, wheat bran, A. niger mycelium, and powdered cellulose, whereas the lignocelluloses were not fermented. Significant correlations were found between the physicochemical properties and the fermentation parameters (p < 0.05). Enzymatic pre-digestion mostly reduced gas, NH3, and SCFA production. In vitro digestibility of DM (IVDMD) and organic matter (IVOMD) was mostly negligible after enzymatic pre-digestion. Fermentation alone led to only 0.10-0.15 IVDMD and 0.14-0.15 IVOMD in lignocelluloses and powdered cellulose, respectively, but 0.44-0.37 IVDMD and 0.46-0.38 IVOMD in the remainder of substrates (p < 0.05). In vitro digestibility was again correlated with the physicochemical properties of the substrates and the fermentation parameters (p < 0.05). The fiber preparations and fiber-rich byproducts were fermented to a relevant extent. In contrast, lignocelluloses were not fermented and can be used rather as bulk material.

Hydrothermal carbonization of biomass residues: mass spectrometric characterization for ecological effects in the soil-plant system.

Hydrochars, technically manufactured by hydrothermal carbonization (HTC) of biomass residues, are recently tested in high numbers for their suitability as feedstock for bioenergy production, the bioproduct industry, and as long-term carbon storage in soil, but ecological effects in the soil-plant system are not sufficiently known. Therefore, we investigated the influence of different biomass residues and process duration on the molecular composition of hydrochars, and how hydrochar addition to soils affected the germination of spring barley ( L.) seeds. Samples from biomass residues and the corresponding hydrochars were analyzed by pyrolysis-field ionization mass spectrometry (Py-FIMS) and gaseous emissions from the germination experiments with different soil-hydrochar mixtures by gas chromatography/mass spectrometry (GC/MS). The molecular-level characterization of various hydrochars by Py-FIMS clearly showed that the kind of biomass residue influenced the chemical composition of the corresponding hydrochars more strongly than the process duration. In addition to various detected possible toxic substances, two independent mass spectrometric methods (Py-FIMS and GC/MS) indicated long C-chain aliphatic compounds which are typically degraded to the C-unit ethylene that can evoke phytotoxic effects in high concentrations. This showed for the first time possible chemical compounds to explain toxic effects of hydrochars on plant growth. It is concluded that the HTC process did not result in a consistent product with defined chemical composition. Furthermore, possible toxic effects urgently need to be investigated for each individual hydrochar to assess effects on the soil organic matter composition and the soil biota before hydrochar applications as an amendment on agricultural soils.