Cattle Slurry Application Research Articles

Effects of Dairy Cattle Slurry Application on Alfalfa Biomass: Photosynthetic Characteristics and Nitrogen and Phosphorus Use Efficiency

Effects of Dairy Cattle Slurry Application on Alfalfa Biomass: Photosynthetic Characteristics and Nitrogen and Phosphorus Use Efficiency

Nitrogen and carbon stocks in sandy soil cultivated with corn subjected to 17 years of animal manure and mineral fertilizer application

Animal manure can be used as a source of nutrients in cropping systems throughout the world. However, in subtropical climates, the impacts of animal manure application over multiple years on crop productivity and on the total organic carbon (TOC) and total nitrogen (TN) stocks in the soil profile are not well understood. In this study, we aimed to evaluate how animal manure application carried out over more than 17 years can impact corn productivity and TOC and TN stocks in different soil layers. This long-term study was conducted from 2004 to 2021 under no-till conditions in southern Brazil. The treatments included pig slurry (PS), cattle slurry (CS), pig deep litter (PDL), mineral fertilizer (NPK) and a control (no fertilizer application). To determine soil TOC and TN stocks, soil samples were collected from the 0.00–0.10, 0.10–0.20, 0.20–0.30, 0.30–0.40 and 0.40–0.50 m layers in December 2008, 2012, 2016 and 2020. Corn productivity was evaluated for the 2008/09, 2012/13, 2016/17, and 2020/21 crops. The highest yields and TOC and TN stocks were observed in soils with pig deep litter and cattle slurry application. In the sandy soil under a no-till system after 26 animal manure applications over 17 years, the highest TOC and TN stocks were observed in the 0.00–0.10 m layer. On average, the TOC stocks obtained for the 0.00–0.10 m layer were 11.21, 14.88, 15.82, 22.59 and 15.16 Mg ha−1 for the control, PS, CS, PDL and NPK treatments, respectively. The soil TN stocks in the 0.00–0.10 m layer were 1.06, 1.40, 1.65, 2.03 and 1.43 Mg ha−1 for the control, PS, CS, PDL and NPK treatments, respectively. The application of pig deep litter to the soil over 17 years resulted in a notable increase in TOC and TN levels, playing a crucial role in increasing the productivity of maize crops.

Methane uptake rates across different soil types and agricultural management practices in Denmark

Upland terrestrial soils play a crucial role in the global methane (CH4) cycle, although their potential as sinks for CH4 remains inadequately quantified. This study investigated CH4 uptake rates spanning two full years at four locations representing typical soil types and crop rotations in Denmark. The sampling campaigns included a total of more than 5000 manual static chamber flux measurements. All locations were, on average, small net sinks for CH4 while displaying significant differences between locations ranging from −1.5±0.3 g CH4-C ha−1 day−1 on the loamy soils to −3.8±0.3 g CH4-C ha−1 day−1 on the sandy soil with the lowest bulk density. A significant negative effect of soil moisture on CH4 uptake was also identified across the locations. Therefore, this study highlights the importance of soil texture and moisture as key controlling variables for CH4 uptake and emphasizes the need for local estimates of sink capacity. Overall, there were no detectable effects of agricultural management practices and fertilisation events did not affect the CH4 flux except for some high emissions following cattle slurry application on coarse sandy soil, which needs some consideration.

Increasing cattle slurry application to grass-clover leys of different ages did not affect nitrate leaching but increased legacy effect in mixed organic crop rotations

ContextOrganic dairy farms with grass-clover often have a large N surplus, due to biological N fixation and in addition, manure application, which challenges the efforts to reduce N losses. Potential loss pathways include leaching from grass-clover ley and subsequent crops, but if managed appropriately this N legacy effect may result in higher yields in the subsequent crops. ObjectiveTo investigate the fate of the ley phase N surplus including losses of nitrate in grass-clover leys, contribution to the N supply of the subsequent crop, and the contribution from the long-term slurry N application to grass-clover leys to nitrate leaching and yields in subsequent crops. MethodsWe quantified nitrate leaching across three years in two six-year crop rotations with two or four years of grass-clover ley and examined legacy effect of the grass-clover ley in relation to short- or long-term N fertilization levels. This was done by measuring water nitrate contents below the root zone combined with water balance modelling. ResultsNitrate leaching in 1- to 4-yr-old grass-clover leys were not influenced by cattle slurry application of up to 300 kg total-N ha-1 (equivalent to approximately 170 kg available N). Leaching losses were 2 - 19 kg N ha-1 yr-1 across grassland ages and application rates. Arable crops showed correspondingly low nitrate leaching (4–24 kg N ha-1 yr-1) except for barley/peas (74 kg N ha-1 yr-1), where a catch crop was established after autumn mechanical weed control. The legacy effect of fertilization on N yield was found in the first year following cultivation of 2-yr-old grass-clover swards and in both year one and two following cultivation of 4-yr-old grass-clover swards. The legacy effect was generally better predicted by the long-term cumulated fertilizer N application during the last rotation (six years) as compared to the most recent grass-clover N application rate. Nitrate leaching in the arable phase of the mixed crop rotations was not affected by fertilizer application in the ley phase. However, this might depend on catch crop strategy in the arable crops. ConclusionsNitrate leaching in dairy crop rotations was not influenced by cattle slurry application. It was found that both the short- and long-term slurry application history were able to explain the legacy effect and of those, the long-term was the best predictor. ImplicationsThe study shows that N leaching reduction targets can be met in an organic dairy crop rotation when attention is paid to the full crop rotation and utilization of short- and long-term legacy effects of slurry application.

Marginal increase in nitrate leaching under grass–clover leys by slurry and mineral fertilizer

AbstractOn dairy farms, fertilization of grass-clover swards ensures stable grass yields but may increase the potential for nitrate leaching on light-textured soils. The aim of this study was to quantify the N use efficiency and nitrate leaching under fertilized grass-clover leys. The study was conducted over 2 years at two sites, with increasing applications of mineral fertilizer (0–480 kg available N ha−1) alone or in combination with a basic application of cattle slurry. For plots fertilized with mineral N, the N soil surface balance was independent of the application rate and in the same range as for unfertilized plots (− 11 to 51 kg N ha−1). However, when plots were fertilized with slurry N (+ mineral N), the surplus was substantially increased owing to the fraction of organic N applied in slurry (95–100 kg N ha−1) and higher biological N2 fixation inputs (55–228 kg N ha−1). The type of fertilizer had no effect on nitrate leaching across the full range of application rates. Nitrate leaching increased quadratically as a function of application rate, with a range of 3–117 kg N ha−1 (0.33–17 mg l−1 in soil solution sampled with suction cups) in the first year and less in the second year, when clover proportion was lower due to the self-regulatory nature of grass-clover mixtures. Importantly, the rate of marginal leaching increased with fertilization level: below 150 kg N ha−1 there was no additional leaching from fertilization and at 200 kg N ha−1 around 5% of additional fertilizer-N was leached. This is less than generally found for arable crops and thus even in intensive dairy systems, grass-clover leys are an environmentally favorable crop.

Effect of Grasslands Fertilisation on Soil Organic Matter Quality and Nutrients Status

Abstract Soil organic matter (SOM) represents one of the largest and most important reservoirs of organic carbon in terrestrial eco-systems. The quality of SOM (e.g., content of soil organic carbon, humic substances, humic acids, fulvic acids, and HA/FA ratio) is a key factor in determining soil fertility and productivity. The loss of SOM is currently considered a detrimental form of soil degradation. The study aims to evaluate the effect of mineral fertilising (NPK), farmyard manure, cattle slurry, and digestate applications in intensively used permanent grassland. The long-term field experiments were carried out at the locality Jevíčko, region of Boskovice Furrow Malá Haná (the Czech Republic). The effect of amending soil with different organic and mineral fertilisers was studied. Qualitative parameters of SOM, soil reaction, and the content of available nutrients (N, P, K, Ca, Mg) were followed. Results showed that the control (no organic input) and the NPK variants had the lowest SOM quality. Higher SOM quality was after the farmyard manure, Slurry, and Digetsate applications. The highest acidity (indicated by the lowest values of pH/KCl) was determined in the control, NPK, Slurry, and D variants. The most favourable soil reaction and available nutrient content were after the farmyard manure application. Humic substances spectral absorption in the UV-VIS and infrared spectral ranges showed that the highest absorbance and amount of aliphatic hydrophobic components were observed after the application of farmyard manure. The multi-criteria statistical evaluation, including principal component analysis and factor analysis, confirmed that amending soil with farmyard manure and slurry resulted in an increase in humic substances content and improved SOM quality.

Effect of Dairy Cattle Slurry Application on Alfalfa Yield, Nitrogen Utilization, and Nitrogen Surplus

Effect of Dairy Cattle Slurry Application on Alfalfa Yield, Nitrogen Utilization, and Nitrogen Surplus

Emissions of nitrous oxide and methane after field application of liquid organic fertilizers and biochar

The use of anaerobic digestates as fertilizer is proposed as a means to close agricultural nutrient cycles. However, digestates have higher inorganic nitrogen contents than raw manures, which could translate into increased emissions of potent greenhouse gases such as nitrous oxide (N2O) and methane (CH4). To mitigate these emissions, the addition of biochar with high nutrient absorption capacity is suggested. To quantify the effects of anaerobic digestion and biochar amendment on N2O and CH4 emissions, we conducted a study over 33 months with four different crops (silage maize, winter wheat, winter barley, and forage grass). We measured soil parameters such as mineral nitrogen, moisture, and temperature. The N2O emissions after application of digestates were generally similar to those observed after cattle slurry or mineral fertilizer application. The highest N2O emissions were observed in the first year of the experiment during maize cultivation and were strongly influenced by high soil nitrate concentrations, which were likely linked to enhanced soil organic N mineralization after ley termination. The CH4 emissions were mostly negative. The addition of biochar to co-digested manure before application at an annual rate of 2 t ha− 1 had no effect on N2O emissions but led to short-lived CH4 peaks from organic fertilizers directly after spreading. We conclude that digestates do not promote larger N2O emissions than mineral fertilizers or cattle slurry, and that biochar addition to digestates in small application quantities does not reduce N2O emissions but bears the risk of CH4 release.

Forms of Toxic and Trace Metals in Grassland Soils of Galicia, Spain

The application of cattle slurry to agricultural soils contributes to the circular economy, while enriching the soil in macro and micronutrients and organic matter. However, this practice can have deleterious environmental effects, by adding toxic metals and other contaminants. The pseudo-total concentrations of nine potentially toxic and trace metals (Fe, Mn, Zn, Cu, Ni, Co, Cr, Cd and Pb) as well as metals extracted by DTPA, Mehlich 3 and 0.01 M CaCl2 were determined in Galician (NW Spain) grassland soils regularly receiving cattle slurry. Four soil depths (0–5, 5–10, 10–20 and 20–40 cm) were sampled and analysed. The pollution condition was assessed by comparing the pseudo-total concentrations with generic reference levels for Galician soils and by using pollution indices. The results indicated the absence of soil pollution by Fe, Ni, Co, Cr and Pb and a situation of no pollution to moderate pollution by Mn, Zn and Cu. Cd was the element most frequently enriched in the studied soils according to the pseudo-total, DTPA and Mehlich-3 concentrations, while the extraction by CaCl2 pointed to no environmental risk. The study supports the lithogenic character of Fe, Ni, Co and Cr, the mixed lithogenic and anthropogenic nature of Mn, Zn and Cu and the anthropogenic origin of Cd in these soils. The latter element can be added by both the application of cattle slurry and inorganic phosphate fertilisers.

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.

The Influence of Organic and Mineral Fertilizers on the Quality of Soil Organic Matter and Glomalin Content

The influence of different fertilizers (mineral/organic) on the quantity and quality of soil organic matter was monitored in long-term stationary experiments (27 years) with silage maize monoculture production on Luvisol. The main aim of this study was to investigate the relationship between easily extractable glomalin (EEG), total glomalin (TG), and parameters commonly used for the determination of soil organic matter quality, i.e., the content of humic acids (CHA), fulvic acids (CFA), and potential wettability index (PWI). A significant correlation was found between EEG content and CSOM content, humic acid content (CHA), humic acid/fulvic acid ratio (CHA/CFA), PWI, and index of aromaticity (IAR). Furthermore, the contents of EEG and TG correlated with soil organic carbon (CSOM). Periodical application of sewage sludge and cattle slurry increased the content of glomalin in soils. From the results, it is obvious that data about glomalin content can be used to study soil organic matter quality. A more sensitive method (a method that reacts more to changes in components of soil fertility) seems to be the determination of EEG rather than TG. The factors supporting use of EEG extraction in agronomic practice are mainly the substantially shorter time of analysis than TG, CHA, and CFA determination and lower chemical consumption. Furthermore, the PWI method is even suitable for studying soil organic matter quality. On the other hand, the humus quality ratio (E4/E6) does not provide relevant information about soil organic matter quality.

Long-Term Effects of Animal Manures on Nutrient Recovery and Soil Quality in Acid Typic Hapludalf under No-Till Conditions

No-till farming and manure application are means of storing carbon in soil and increasing soil quality. However, the organic fertilization of no-till soils may sustain subtropical agroecosystems for only a limited period until the soil quality declines. The C, N, P, and other nutrient cycles are perturbed due to the nutrient imbalance in manures and their application on the soil surface, which poses a risk for nutrient dispersion into the environment. Long-term N-based manure application also impacts the apparent nutrient recovery (ANR) by crops and, hence, the crop quality. Our objective was to monitor changes in soil quality and to measure nutrient recovery from N-based organic fertilization in a Brazilian agroecosystem. A long-term experiment was established in May 2004 on Typic Hapludalf soil in Southern Brazil. The experiment comprised two periods: 2004–2009 and 2009–2020. The treatments were unfertilized (control), pig slurry, pig deep litter (swine manure and rice husk), cattle slurry, and mineral fertilizer (urea, triple superphosphate, and K chloride). Grain and cover crops were grown. The maize grain yield and oat biomass were used as indicators of productivity. The application of cattle slurry, pig deep litter, and pig slurry increased the grain production by 20% on average compared to mineral fertilization. Organic manuring increased the soil pH by up to one unit, while urea acidified the soil. The highest crop yields were obtained with pig deep litter, which increased the levels of P, K, Ca, Mg, and C in the soil test. Pig deep litter showed the highest N-ANR for the aboveground part of the plants. The ANRs for P, K, Ca, and Mg were also highest when pig slurry had been applied. The ANR values for the micronutrients varied widely among the organic sources but indicated large marginal offtake gains compared to mineral fertilization. The N-based fertilization with animal manures increased the rate of nutrient uptake by plants but led to an accumulation of nutrients in the soil, threatening the sustainability of the system. Manure applications must be monitored regularly to avoid the accumulation of nutrients that could impair the soil quality and become an environmental problem in the future.

NH3 Emissions After Trailing Hose Application of Cattle Slurry and Digestates

NH3 Emissions After Trailing Hose Application of Cattle Slurry and Digestates

Contrasting effects of slurry and mineral fertilizer on N2-fixation in grass-clover mixtures

In dairy systems, grass–clover swards are fertilized with on–farm cattle slurry as a basic dressing and often supplemented with mineral fertilizer throughout the season. Uncertainty remains on consequences for N input from atmospheric N2-fixation by grassland legumes. The aim of this study was to examine the N response of slurry versus mineral N fertilization on clover dynamics, the proportion of N derived from the atmosphere (%Ndfa) and the quantitative N2-fixation (qBNF) using the 15N isotope dilution method. This was done in an on farm setting at two sites in two years with increasing rates of N fertilizer (0–480 kg available N ha-1) either of mineral N only or combined with application of cattle slurry. The leys were at one site composed a 2–species mixture of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) and at the other site of a 4–species mixture of white clover, red clover (Trifolium pretense L.), festulolium (Festulolium braunii) and ryegrass. Species dynamics were significantly affected by fertilizer rate in the 2–species sward and by fertilizer rate and type in the 4–species sward. Reduction of the clover proportion in response to fertilization was due to a clover yield decrease (2–species sward) or a grass yield increase (4–species sward). In the 4–species sward, in treatments with mineral N only %Ndfa decreased markedly with N rate, whereas the corresponding slurry + mineral N treatments did not. Thus, apart from fertilization with mineral N only at one site the general picture was a relatively high (>80%) %Ndfa over the season when the N level was below 200–300 kg available N ha-1. The qBNF of the harvested biomass in sward without fertilization reached 193–216 kg N ha-1 in the 2–species sward and 203–286 kg N ha-1 in the 4–species sward. Clover persisted at high fertilization rates, but qBNF was reduced to 16–79 kg N ha-1 and 58–163 kg N ha-1 in 2– and 4–species swards, respectively. Interestingly, in the 4–species sward amended with slurry + mineral N, qBNF was high and independent of fertilization rate. We conclude that response of clover dynamics to N fertilization differed with fertilizer type and level – slurry have lower effect whereas the effect of mineral N only on N2-fixation is less predictable.

Quantitative microbial human exposure model for faecal indicator bacteria and risk assessment of pathogenic Escherichia coli in surface runoff following application of dairy cattle slurry and co-digestate to grassland

Animal waste contains high numbers of microorganisms and therefore can present a potential biological threat to human health. During episodic rainfall events resulting in runoff, microorganisms in the waste and soil may migrate into surface runoff, contaminating surface water resources. A probabilistic human exposure (HE) model was created to determine exposure to faecal indicator bacteria (FIB): total coliforms (TC), E. coli and enterococci following application of bio-based fertiliser (dairy cattle slurry, digestate) to grassland; using a combination of experimental field results and literature-based data. This step was followed by a quantitative microbial risk assessment (QMRA) model for pathogenic E. coli based on a literature-based dose-response model. The results showed that the maximum daily HE (HEdaily) is associated with E. coli for unprocessed slurry (treatment T1) on day 1, the worst-case scenario where the simulated mean HEdaily was calculated as 2.84 CFU day −1. The results indicate that the overall annual probability of risk (Pannual) of illness from E. coli is very low or low based on the WHO safe-limit of Pannual as 10 −6. In the worst-case scenario, a moderate risk was estimated with simulated mean Pannual as 1.0 × 10 −5. Unpasteurised digestate application showed low risk on day 1 and 2 (1.651 × 10 −6, 1.167 × 10 −6, respectively). Pasteurised digestate showed very low risk in all scenarios. These results support the restriction imposed on applying bio-based fertiliser if there is any rain forecast within 48 h from the application time. This study proposes a future extension of the probabilistic model to include time, intensity, discharge, and distance-dependant dilution factor. The information generated from this model can help policymakers ensure the safety of surface water sources through the quality monitoring of FIB levels in bio-based fertiliser.

Carbon Accumulation in Arable Soils: Mechanisms and the Effect of Cultivation Practices and Organic Fertilizers

The organic carbon content of soils is a key parameter of soil fertility. Moreover, carbon accumulation in soils may mitigate the increase in atmospheric CO2 concentration. The principles of carbon accumulation in arable soils are well known. The inclusion of clover/alfalfa/grass within the rotation is a central instrument to increase soil organic carbon. In addition, the regular application of rotted or composted farmyard manure within the rotation can increase soil organic carbon contents much more than the separate application of straw and cattle slurry. Humic substances, as a main stable part of soil organic carbon, play a central role in the accumulation of soil carbon. A major effect of compost application on soil carbon may be the introduction of stable humic substances which may bind and stabilize labile organic carbon compounds such as amino acids, peptides, or sugars. From this point of view, a definite soil carbon saturation index may be misleading. Besides stable composts, commercially available humic substances such as Leonardite may increase soil organic carbon contents by stabilization of labile C sources in soil.

Slow pyrolysis liquid in reducing NH3 emissions from cattle slurry — Impacts on plant growth and soil organisms

A substantial percentage of manure nitrogen (N) can be lost as gaseous ammonia (NH3) during storage and field spreading. Lowering slurry pH is a simple and accepted method for preserving its N. Efficiency of slow pyrolysis liquid (PL) produced from birch (Betula sp.) as an acidifying agent, and its ability to reduce NH3 emissions following surface application of cattle slurry, was studied in a field experiment. Untreated slurry (US) and slurries acidified with PL and sulfuric acid (SA) were applied to the second harvest of a grass ley. Immediate NH3 emissions, grass biomass, N-yield and possible toxic impacts on soil nematodes and enchytraeids were examined. Furthermore, the effects on soil respiration, nitrogen dynamics and seed germination were studied in subsequent laboratory experiments.In the field, over one third of the water-extractable ammonium-N (NH4-N) applied was lost through NH3 volatilization from US. SA and PL acidified slurries reduced NH3-N emission rate equally from 3.4 to <0.04 kg ha−1 h−1. Acidification with SA resulted in the highest and that with PL in the lowest grass dry matter (DM) and N yield. Neither SA nor PL acidification had negative effects on soil enchytraeids or nematodes. Reduced yield production, seed germination and delayed microbial activity after PL slurry application were most probably caused by the PL containing organic compounds. However, later increase in carbon dioxide (CO2) production and improved seed germination suggest that these compounds were rapidly volatilized and/or degraded by soil microbes. Though PL efficiently cut NH3 emission from surface-spread slurry, further studies on appropriate application methods and possible phytotoxicity are needed.

Natural estrogen emissions to subsurface tile drains from experimental grassland fields in Switzerland after application of livestock slurries and free compounds.

Natural estrogens are present in high concentrations in livestock slurries, which are often applied to agricultural fields in large quantities. As such, the export of slurry-derived natural estrogens from tile-drained fields is a potential source for estrogenic pollution in surface waters. Yet despite the abundance of tile-drained fields in Central Europe, export of natural estrogens from agricultural fields receiving livestock slurries is rarely studied in this region. In an effort to fill this knowledge gap, here we applied natural estrogens to Swiss experimental fields in the form of cattle slurry, pig slurry or dissolved in water, and quantified them in flow-proportionally collected drainage water over 18months. After pig and cattle slurry applications, concentration maxima in drainage water of 73, 8, 37, and 60ngL-1 for 17α-estradiol (E2α), 17β-estradiol (E2β), estrone (E1), and estriol (E3), respectively, were observed shortly after rain events. The exported fractions of individual natural estrogens to tile drains were on average 0.26% (ranging from 0.08 to 0.41%) after cattle, and 0.18% (0.03-0.40%) after pig slurry applications. Such numbers were higher than expected from the leaching potential based on substance properties, and comparable to those of more mobile micropollutants previously studied on the same fields. Natural estrogens were mainly exported to tile drains through preferential flow. Exported fractions were lower when applied in aqueous solution than when applied in slurry, pointing to particle-facilitated transport to tile drains when applied in slurry. In Switzerland, the estimated 6.3, 0.6, 7.4, and 7.7g of E2α, E2β, E1, and E3, respectively, exported through the tile-drained agricultural area per year contribute little to the total natural estrogen load received by surface waters. However, after slurry applications in highly drained catchments, natural estrogen emissions to tile drains can cause short term (i.e. less than 1week) estrogenic exposure in nearby streams.

Long-Term Effects of Organic Amendments on Soil Organic Matter Quantity and Quality in Conventional Cropping Systems in Switzerland

Increasing soil organic carbon (SOC) in agroecosystems is a promising solution to simultaneously address climate change mitigation, adaptation, and food security. Yet, the best management practices that could achieve these goals remain to be identified. Here, we analyze the long-term effects of application of green manure, cereal straw, farmyard manure, and cattle slurry on SOC in a 37 year long field experiment in Switzerland. The treatment effects were compared against control conditions that received only optimal mineral fertilization. More specifically, this study aimed at evaluating the effect of organic amendments on SOC accumulation and distribution in different soil particle-size fractions by means of a set of indicators about organic matter quality (biological reactivity, humification index) and microbial activity (extracellular enzyme activities). In the absence of organic matter input, application of mineral fertilizers alone resulted in the lowest SOC content and the highest humification index of the bulk soil organic matter. Among the organic amendments, cereal straw, farmyard manure, and cattle slurry promoted a higher SOC content and a lower humification index due to an increase of SOC in the clay-size fraction. The annual C accrual reached 4.4‰ per year over 37 years with farmyard manure. The higher biological reactivity measured for the green manure and cereal straw amendments was associated with higher soil enzymatic activities, while C retention coefficients decreased by at least 2.5 times compared to animal-derived amendments. The low availability of nutrients in green manure and straw amendments as suggested by the high phosphatase and N-acetylglucosaminidase activities may indicate a reduction in C retention of organic matter inputs due to nutrient microbial mining with plant-derived amendments.

Effect of Nitrification Inhibitors on N2O Emissions after Cattle Slurry Application

Cattle slurry injection (INJ) has shown to be an efficient measure to reduce ammonia (NH3) losses from soils but it might also significantly increase nitrous oxide (N2O) emissions, which can dominate the total greenhouse gas (GHG) release in silage maize production (Zea mays L.). Nitrification inhibitors (NIs) are known for their potential to mitigate N2O. Therefore, we tested the effect of NIs added to cattle slurry before INJ on N2O fluxes from a Haplic Luvisol under silage maize in southwest Germany. We determined N2O fluxes at least weekly, with the closed chamber method over two full years. NIs differ in their chemical and physical behavior and we therefore tested a range of commercially available NIs: 3,4-dimethylpyrazole phosphate, 3,4-dimethylpyrazol succinic acid, a mixture of both, nitrapyrin, dicyandiamide, and 1,2,4 triazol and 3-methylpyrazol. Although not significant, INJ treatments with NI showed lower mean annual N2O emissions than the INJ treatment without NI in the 1st year. The emission reduction by NI of 46% in the 2nd year was statistically significant. In both years, we did not find any difference in N2O release, crop yield, or nitrogen removal between the different NI treatments. In the 1st year, which was extraordinary dry and warm, emission factors (EFs) for all INJ treatments were 4 to 8-fold higher than default EF from the IPCC. Even in the 2nd year, only three NI treatments reached EFs within the range provided by the IPCC. Direct N2O accounted for between 81 and 91% of the total GHG emission. Area- and yield-related GHG emission of the broadcast application with subsequent incorporation was in both years in the statistical class with lowest emission. In contrast, INJ with NIs showed similar GHG emissions in only one year, and consequently, incorporation was found to be the optimum management practice for livestock farmers in our study region.