Nitrous Oxide Emission from Grazing Is Low across a Gradient of Plant Functional Diversity and Soil Conditions

Nitrous oxide (N2O) emissions from pastures can vary significantly depending on soil and environmental conditions, nitrogen (N) input, as well as the plant’s ability to take up the N. We tested the hypothesis that legume-based N sources are characterized by significantly lower emission factors than mineral N based dairy systems. Therefore, this study monitored N2O emissions for a minimum of 100 days and up to two growing seasons across a gradient of plant species diversity. Emissions were measured from both grazed pastures and a controlled application of urine and dung using the static chamber method. About 90% of the simulated experiments’ accumulated N2O emissions occurred during the first 60–75 days. The average accumulated N2O emissions were 0.11, 0.87, 0.99, and 0.21 kg ha−1 for control, dung, urine patches, and grazed pastures, respectively. The N uptake efficiency at the excreta patch scale was about 70% for both dung and urine. The highest N2O-N emission factor was less than half compared with the IPCC default (0.3 vs. 0.77), suggesting an overestimation of N2O-N emissions from organically managed pastures in temperate climates. Plant diversity showed no significant effect on N2O emission. However, functional groups were significant (p < 0.05). We concluded that legume-containing pasture systems without a fertilizer addition generally appear capable of utilizing nitrogen inputs from excreta patches efficiently, resulting in low N2O emissions

Nitrous Oxide Emission from Forage Plantain and Perennial Ryegrass Swards Is Affected by Belowground Resource Allocation Dynamics

Soil–plant interactions affecting nitrous oxide (N2O) are not well-understood, and experimental data are scarce. Therefore, a greenhouse experiment was conducted in a 3 × 3 full factorial design, comprising three mineral N fertilizer rates (0, 150 and 300 kg N ha−1) applied to monoculture swards and a binary mixture of Plantago lanceolata and Lolium perenne. The parameters measured included daily N2O emissions, aboveground (AG) and belowground biomass (BG), N and C yields, as well as leucine aminopeptidase (LAP) activity in the soil as an indicator for soil microbial activity. Nitrous oxide emission and LAP were measured using the static chamber method and fluorimetric microplate assays, respectively. Cumulative N2O emissions were about two times higher for P. lanceolata than L. perenne monoculture swards or the mixture (p < 0.05). The binary mixtures also showed the highest N use efficiency and LAP activity, which significantly (p < 0.05) correlated with the C concentration in the belowground biomass. Plantago lanceolata was generally ineffective at reducing N2O emissions, probably due to the young age of the swards. Among the biological factors, N2O emission was significantly associated with biomass productivity, belowground C yield, belowground N use efficiency and soil microbial activity. Thus, the results suggested belowground resource allocation dynamics as a possible means by which swards impacted N2O emission from the soils. However, a high N deposition might reduce the N2O mitigation potential of grasslands

Nitrogen availability determines the long-term impact of land use change on soil carbon stocks in grasslands of southern Ghana

Enhancing the capacity of agricultural soils to resist soil degradation and to mitigate climate change requires long-term assessments of land use systems. Such long-term evaluations, particularly regarding low-input livestock systems, are limited. In the absence of suitable long-term experiments, this study assessed the outcome of C inputs and outputs across an array of plant functional groups in arable and permanent systems of a tropical savannah after more than 50 years of consistent land use. Soil samples were taken (0–30 cm depth) from arable crop fields, grazed–seeded grassland, cut–use permanent crops and native grassland. Soil organic carbon (SOC) stocks ranged from 17 to 64 Mg SOC ha−1 (mean ± sd = 32.9 ± 10.2 Mg ha−1). SOC stocks were lower for grazed–seeded grassland relative to cut–use grass, legume trees and shrubs. Accordingly, while the conversion of the native grassland to grazed pastures caused an estimated loss of 44 % of SOC over the period, the conversion to woody legumes resulted in slight (5 %), incremental gains. Within sown systems, nitrogen (N) availability seemed to be the most critical factor in determining the fate of the SOC stocks, with the soil N concentration and SOC being highly correlated (r – 0.86; p < 0.001). In total N, P and K were significant predictors of SOC density in the soils. Moreover, secondary plant metabolites in legumes, namely tannins, were identified as having an impact on SOC. The results from this study provide the theoretical basis for testing the hypothesis that improved soil fertility management and the use of tannin-rich plants have the potential to promote long-term SOC storage in the savannah ecological region

Effects of replacing fishmeal with black soldier fly larval meal in the diets of grower-finishing guinea fowls reared under tropical conditions

The study was conducted with the view to determine the impact of replacing fishmeal with black soldier fly larval meal (BSFLM) on growing guinea fowls. BSFLM replaced fishmeal (3% in the control diet) in the ratios of 0, 20, 40, 60, 80, and 100% to produce six dietary treatments, which were iso-caloric and iso-nitrogenous. Two hundred and forty-eight-week old guinea fowls with mean live weight of 273.2 ± 10.9 g were tagged, weighted, and randomly assigned to 24 (6 × 4) floor pens; each pen was treated as a replicate. Feed and water were provided ad libitum during the entire period, which lasted 10 weeks. Feed consumption differed among the treatment groups (P = 0.0072) with the 100% fishmeal diets recording the lowest. Daily gain was significantly (P = 0.009) higher for birds fed high BSFLM diets compared to the control (100% fishmeal diet). The inclusion of BSFLM in the diets elicited positive linear effect on weight gains of the guinea fowls (R2 = 0.91) with increasing concentration resulting in higher live weight gains. The feed conversion ratio (FCR) also differed between treatments (P < 0.05) but similar for the 100% fishmeal (control) and 100% BSFLM diets. Organ and haematopoitic integrity were equally assured regardless of levels of the protein sources fed to the birds. Generally, meats from birds fed 60 to 100% BSFLM and from hens were more acceptable. A study to evaluate the economics of utilising BSFLM in guinea fowl production is recommended

Verschiedene Futtermittelproduktionssysteme und Ihr Potenzial zur Treibhausgas Massnahmen

The impact of agriculture on the environment has become a sharp focus, especially as future demand for food is projected to double over the next 2-3 decades. The negative impact of agriculture on the environment is primarily blamed on intensifying and simplifying production evident on the field, farm, landscape or regional scale. Grassland use contributes to climate change and environmental degradation, but it can also be used as a tool for greenhouse gas emissions mitigation. Moreover, low-input systems are often considered ecologically beneficial, but their sustainability under intensification is uncertain. Plant-soil feedbacks regulate soil carbon and nitrogen cycling via litterfall, root decay and root exudates, controlling microbial population dynamics in most soils, yet their impact may vary depending on the vegetation type. Enhancing the capacity of low-input systems to resist soil degradation and mitigate climate change requires long-term assessments. In Chapter 2, this thesis assessed the outcome of C inputs and outputs across an array of plant functional groups in arable and permanent systems of a tropical Savannah after more than 50 years of consistent land use. Soil samples were taken (0–30 cm depth) from arable crop fields, grazed-seeded grassland, cut-use permanent crops and native grassland. Soil organic carbon (SOC) stocks ranged from 17 to 64 Mg SOC ha-1 (mean±sd = 32.9±10.2 Mg ha-1). SOC stocks were lower for grazed-seeded grassland relative to cut-use grass, legume trees and shrubs. Accordingly, while converting the native grassland to grazed pastures was estimated to have lost 44 % of SOC over the period, the conversion to woody legumes resulted in slight (5 %) incremental gains. Within sown systems, nitrogen (N) availability seemed to be the most critical factor that determines the fate of the SOC stocks, with soil N concentration and SOC being highly correlated (r = 0.86; p<0.001). In total, N, P and K were significant predictors of SOC density in the soils.Experiments to test the hypothesis that legume-based N sources are characterized by significantly lower emission factors than mineral N based dairy systems were described in Chapter 3. This study monitored N2O emissions for a minimum of 100 days and up to two growing seasons across a gradient of plant species diversity. Emissions were measured from grazed pastures and a controlled urine and dung application using the static chamber method. About 90% of the simulated experiments’ accumulated N2O emissions occurred during the first 60–75 days. The average accumulated N2O emissions were 0.11, 0.87, 0.99, and 0.21 kg ha−1 for control, dung, urine patches, and grazed pastures, respectively. The N uptake efficiency at the excreta patch scale was about 70% for both dung and urine. The highest N2O-N emission factor was less than half compared with the IPCC default (0.3 vs 0.77), suggesting an overestimation of N2O-N emissions from organically managed pastures in temperate climates. Plant diversity showed no significant effect on N2O emission. However, functional groups were significant (p < 0.05). Moreover, soil-plant interactions affecting N2O production in soils are not well understood, and experimental data are scarce. A better understanding of the mechanisms by which plants affect N2O emission would facilitate the selection of forage species for sustainable intensification. In Chapter 4, this thesis described a greenhouse experiment that tested the hypothesis that high forage plantain Plantago lancelota (PL) than Lolium perenne (LP) in mixtures reduces N2O emission. The greenhouse experiment was arranged in a 3x3 factorial, fully randomized design, comprising three mineral N fertilizer rates (0, 150 and 300 kg N ha-1) applied to two monocultures (LP and PL) and one binary (LP-PL) sward mixture. Parameters measured included daily N2O emissions, aboveground (AGB) and belowground biomass (BGB), N- and C- yields above- and belowground, as well as leucine aminopeptidase (LAP) activity in the soil as an indicator for soil microbial activity. Results showed that accumulated N2O emissions (83 days) were about two times higher for PL than LP or LP-PL swards (p<0.05). N application increased AGB in all treatments (p<0.001), however, the N300 rate reduced biomass allocation belowground. The PL yielded lower dry matter (AGB+BGB) and N than LP or LP-PL (p<0.001). As a result, the binary sward (LP-PL) showed the highest N use efficiency and increased LAP activity. Spearman correlation analyses and structural equation modelling suggested C allocation dynamics belowground as a potential means by which plants might impact N2O emission. Thus, the work generally demonstrates the potential of mixtures to reduce the environmental impacts of agriculture. Despite identifying some variables influencing nutrient cycling and recognizing that emission factors are overestimated in grassland systems in temperate climates, uncertainties remain, making the accurate estimation of emissions across different soil types difficult

Impact of cattle slurry application methods on ammonia losses and grassland nitrogen use efficiency

Optimal manure management is required to ensure efficient nutrient supply to farmland and to avoid adverse environmental impacts. Accordingly, ammonia (NH3) emissions associated with different slurry application techniques were investigated in grassland trials under different soil and weather conditions across Germany. Cattle slurry was applied in two dressings, early in spring and after the first silage cut, with a target amount of 170 kg N ha 1. The application treatments comprised: trailing shoe (TS), acidified slurry applied with trailing shoe (TS + A), open slot injection (SI), and slurry treated with a nitrification inhibitor (NI) applied by slot injection (SI + NI). In addition, slurry application techniques were compared with a non-N-fertilized control and a mineral fertilizer treatment (calcium ammonium nitrate, CAN). NH3 measurements followed each N application event. NH3 losses were equivalent to 1–39% of total ammoniacal nitrogen (TAN) applied. The average NH3 mitigation potential of the different slurry application techniques compared to TS was 45.7 ± 7, 21.2 ± 6.2 and 13.7 ± 8.2% for TS + A, SI and SI + NI, respectively. The use of nitrification inhibitor with slot injected slurry did not increase NH3 losses relative to TS (p > 0.05). Mean apparent N use efficiency was two times higher for CAN (49%) than the slurry treatments (24%) but was comparable between SI + NI and CAN in five out of the eight cases. Our results indicate that mean TAN related NH3 emissions of tested treatments (3.3, 22.6, 12.2, 17.8 and 19.3% for CAN, TS, TS + A, SI and SI + NI, respectively) were generally lower than described in previous studies. Moreover, the results suggested possible increases in NH3 mitigation and N use efficiency when cattle slurry is applied with acidification or injection techniques. We found no evidence that NI addition to slot injected slurry, a treatment discussed as a measure to reduce N2O emission and nitrate leaching, changed NH3 emission

Effect of slurry application techniques on nitrous oxide emission from temperate grassland under varying soil and climatic conditions

The effect of slurry application techniques and slurry N stabilizing strategies on nitrous oxide emission from grasslands is poorly understood and, therefore, can result in large uncertainties in national/regional inventories. Field experiments were, thus, conducted to estimate the effect of different fertilization techniques on nitrous oxide (N2O) emissions. Fertilizer was applied (135–270 kg N ha−1 year−1) as calcium ammonium nitrate (CAN), untreated or treated cattle slurry. The slurry was either treated with sulfuric acid (target pH = 6.0), applied using trailing shoes or treated with 3,4-dimethyl pyrazole phosphate and applied via slot injection. N2O fluxes were sampled using the closed chamber technique. Cumulative N2O emissions ranged 0.1–2.9 kg N ha−1 year−1 across the treatment, sites and years. The N application techniques showed inconsistent effects on soil mineral N content, cumulative N2O emission and N yield. The fertilizer replacement value of slurry was low due to low N use efficiencies at the sites. However, a close positive relationship (r = 0.5; p = .013) between slurry value and biomass yield was observed, highlighting the benefit of high slurry value on crop productivity. N2O-N emission factors were low for all treatments, including CAN, but were 2–6 times higher in 2019 than in 2020 due to lower precipitation in 2020. Variations in N2O emission were largely explained by soil and climatic factors. Even with the low N2O emissions, this study highlights the benefit (significant mitigation of N2O emissions) of replacing the increasingly expensive chemical fertilizer N with input from slurry under favourable conditions for denitrification

Impact of black soldier fly larval meal on growth performance, apparent digestibility, haematological and blood chemistry indices of guinea fowl starter keets under tropical conditions

In order to assess the impact of larval meal on guinea fowl, six iso-caloric and iso-nitrogenous diets were fed to day-old-keets ad libitum till 8weeks of age. Water was also freely provided. The fishmeal (FM) component of the experimental diets was replaced with black soldier fly larval meal (BSFLM) in the following percentage ratios of 0&ndash;100%. Results showed that body weight gain significantly (P&lt;0.05) increased in all the BSFLM treatment groups compared to the control group. The final body weight of the birds at age 8weeks differed significantly (P&lt;0.001). Dry matter intake varied (P&lt;0.001) slightly among the birds but never affected (P&gt;0.05) ME intake and faecal output as well as weight changes of the keets. Digestibility of dry matter and energy were not affected (P&gt;0.05) by the differences in diet. Organ and haematopoietic integrity were assured regardless of the protein types used as well as levels of inclusion. The results suggest that the replacement of fishmeal with BSFLM in so far as the economics of production is concerned could result in reduced feed cost for starter guinea keet judging from diets that contained 60&ndash;100% BSFLM

GülleBest : What low-emissions technology exists for the application of slurry and digestate?

Rund 95 % der Ammoniakemissionen in Deutschland stammen aus der Landwirtschaft, 40 % davon aus der Ausbringung von Wirtschaftsdüngern. Flüssige Wirtschaftsdünger enthalten hohe Anteile an Ammoniumstickstoff, der insbesondere im Kontakt mit der Atmosphäre schnell in gasförmiges Ammoniak (NH3) umgewandelt werden kann. Damit geht der Stickstoff den Pflanzen als wichtiger Nährstoff verloren. Der Luftschadstoff NH3 gefährdet nicht nur sensible Ökosysteme, sondern auch die menschliche Gesundheit.Around 95 % of ammonia emissions in Germany come from agriculture, 40 % of which from the application manure. Manure generally contains high amounts of ammonium nitrogen, which can be rapidly transformed into gaseous ammonia (NH3), especially upon exposure to the atmosphere. The nitrogen is thus lost to the plants as an important nutrient. The air pollutant NH3 not only endangers sensitive ecosystems, but also human health