Manure Application Timing Research Articles

Land-use controls on nutrient loads in aquifers draining agricultural and mixed-use karstic watersheds.

Agricultural nonpoint source pollution from the upper areas of the Upper Mississippi, Missouri, and Ohio River basins accounts for the majority of the excess nitrogen that leads to the Gulf of Mexico's hypoxic zone. However, agriculture landscapes across the USA, Europe, and China are undergoing major changes related to the proliferation of confined animal feeding operations (CAFOs) that account for a greater proportion of point source contamination. Mitigating long-term nutrient inputs at a large scale (Mississippi River Basin) requires understanding these microscale changes at the small watershed level (less than 100km2). To assess the control of land-use and subsurface hydrological processes on nutrient fate and transport, temporal patterns in nutrient concentrations in a mixed land-use karstic watershed were analyzed. To assess the control of differential land-use sources on total inorganic nitrogen (TIN) loads within the watershed, 4months of weekly water sampling was performed at a spring location and at two underground conduit locations. The observed temporal variations in nutrient concentrations are primarily associated with seasonal changes in land-use associated with corn growth. Data show that land-use sources explain much of the temporal variability of TIN at the spring when weighted against the hydrological factor. End-member-mixing analysis of dissolved organic carbon (DOC) shows a progressive increase in the contribution of DOC-enriched sources and a more labile form of carbon toward the harvest time. Overall, during high flow, nonpoint source infiltration from manure-fertilized croplands in the northern branch (NB) dominate DOC loads. Because conduit-dominated karstic aquifers are more susceptible to contamination from direct and fast (< 7h) subsurface infiltration during late summer rainfall period (July to August), a slight advance in the timing of manure application could substantially reduce nutrient loads to local groundwater. A combined evaluation of subsurface hydrological processes and land-use factors controlling nutrients at the scale of small watersheds is crucial to developing site-specific nutrient management plans and managing the Gulf of Mexico's hypoxic zone.

Assessing the effects of manure application rate and timing on nitrous oxide emissions from managed grasslands under contrasting climate in Canada.

It is uncertain whether process-based models are currently capable of simulating the complex soil, plant, climate, manure management interactions that influence soil nitrous oxide (N2O) emissions from perennial cropping systems. The objectives of this study were (1) to calibrate and evaluate the DeNitrification DeComposition (DNDC) model using multi-year datasets of measured nitrous oxide (N2O) fluxes, soil moisture, soil inorganic nitrogen, biomass and soil temperature from managed grasslands applied with manure slurry in contrasting climates of Canada, and (2) to simulate the impact of different manure management practices on N2O emissions including slurry application i) rates (for both single vs. split); and ii) timing (e.g., early vs. late spring). DNDC showed "fair" to "excellent" performance in simulating biomass (4.7%≤normalized root mean square error (NRMSE)≤29.8%; -9.5%≤normalized average relative error (NARE)≤16.1%) and "good" performance in simulating soil temperature (13.2%≤NRMSE≤18.1%; -0.7%≤NARE≤10.8%) across all treatments and sites. However, the model only showed "acceptable" performances in estimating soil water and inorganic N contents which was partially attributed to the limitation of a cascade water sub-model and inaccuracies in simulating root development/uptake. Although, the DNDC model only demonstrated "fair" performance in simulating daily N2O fluxes, it generally captured the impact of the timing and rate of slurry application and soil texture (loam vs. sandy loam) on total N2O emissions. The DNDC model simulated N2O emissions from spring better than split manure application (fall and spring) at the Manitoba site partially due to the overestimation of available substrates for microbial denitrification from fall application during the wet spring periods. Although DNDC performed adequately for simulating most of the manure management impacts considered in this study we recommend improvements in the simulation of soil freeze-thaw cycles, manure decomposition dynamics, soil water storage, rainfall canopy interception, and microbial denitrification and nitrification activities in grasslands.

Modeling and Mitigating Phosphorus Losses from a Tile-Drained and Manured Field Using RZWQM2-P.

Prediction of P losses from manured agricultural fields through surface runoff and tile drainage is necessary to mitigate widespread eutrophication in water bodies. However, present water quality models are weak in predicting P losses, particularly in tile-drained and manure-applied cropland. We developed a field-scale P management model, the Root Zone Water Quality Model version 2-Phosphorus (RZWQM2-P), whose accuracy in simulating P losses from manure applied agricultural field is yet to be tested. The objectives of this study were (i) to assess the accuracy of this new model in simulating dissolved reactive phosphorus (DRP) and particulate phosphorus (PP) losses in surface runoff and tile drainage from a manure amended field, and (ii) to identify best management practices to mitigate manure P losses including water table control, manure application timing, and spreading methods by the use of model simulation. The model was evaluated against data collected from a liquid cattle manure applied field with maize ( L.)-soybean [ (L.) Merr.] rotation in Ontario, Canada. The results revealed that the RZWQM2-P model satisfactorily simulated DRP and PP losses through both surface runoff and tile drainage (Nash-Sutcliffe efficiency > 0.50, percentage bias within ±25%, and index of agreement > 0.75). Compared with conventional management practices, manure injection reduced the P losses by 18%, whereas controlled drainage and winter manure application increased P losses by 13 and 23%, respectively. The RZWQM2-P is a promising tool for P management in manured and subsurface drained agricultural field. The injection of manure rather than controlled drainage is an effective management practice to mitigate P losses from a subsurface-drained field.

Fall Tillage Reduced Nutrient Loads from Liquid Manure Application during the Freezing Season.

Reducing agricultural runoff is important year round, particularly on landscapes that receive wintertime applications of manure. No-tillage systems are typically associated with reduced runoff loads during the growing season, but surface roughness from fall tillage may aid infiltration on frozen soils by providing surface depressional storage. The timing of winter manure applications may also affect runoff, depending on snow and soil frost conditions. Therefore, the objective of this study was to evaluate runoff and nutrient loads during the freezing season from combinations of tillage and manure application timings. Six management treatments were tested in south-central Wisconsin during the winters of 2015-2016 and 2016-2017 with a complete factorial design: two tillage treatments (fall chisel plow vs. no-tillage) and three manure application timings (early December, late January, and unmanured). Nutrient loads from winter manure application were lower on chisel-plowed versus untilled soils during both monitoring years. Loads were also lower from manure applied to soils with less frost development. Wintertime manure applications pose a risk of surface nutrient losses, but fall tillage and timing applications to thawed soils can help reduce loads.

Influence of Dairy Slurry Manure Application Method, Fall Application‐Timing, and Winter Rye Management on Nitrogen Conservation

Core Ideas Manure application method and timing affected ryelage but not rye cover biomass. Manure injection compared to broadcast conserved manure‐N in ryelage. Manure injection compared to broadcast with rye cover resulted in more corn silage. Late injection compared to early injection conserved more manure‐N in ryelage. Late versus early injection resulted in more manure‐N in soil and more corn after cover crops. Fall manure applications can lead to nutrient losses prior to spring planting. This 2‐yr study evaluated effects of winter cereal rye (Secale cereal L.) crop management (cover crop versus ryelage), and fall, dairy slurry manure application method (broadcasted versus injected) and timing (September vs. November) on manure–N conservation. Nitrogen conservation was calculated from NH3 volatilization, percentage of manure–N in aboveground rye (%ManureN‐R) and soil (%ManureN‐S) in spring prior to corn (Zea mays L.) planting, and subsequent corn yield. Ryelage compared to cover crop conserved more %ManureN‐R (2.6‐fold) and despite reduced corn yield, ryelage‐corn treatments with 3.6‐fold greater rye biomass produced 20% greater total harvested forage than cover crops. Compared to broadcasted manure (BM), injected manure (IM) reduced NH3 losses and increased ryelage biomass (42%) after September (EARLY) applications, %ManureN‐R (50%), %ManureN‐S at multiple depths, and total harvested forage (20%). Corn silage yield with IM compared to BM was also greater after all cover crop treatments (23%), all ryelage treatments in 2015 (35%), and ryelage with a November application (LATE) in 2014 (30%). Compared to EARLY, LATE applications increased %ManureN‐R in ryelage after BM (44%) and IM (50%), %ManureN‐S at multiple depths in both rye treatments, and corn silage yields with IM following cover crops (21%). Following ryelage, corn yields were not larger following greater %ManureN‐S in LATE IM versus BM, suggesting potential for more soil NO3 leaching loss with LATE IM. However, multiple management options reduced fall manure–N losses and conserved manure–N for crop utilization, allowing for farm management flexibility.

Development of PLEAD: A Database Containing Event-based Runoff Phosphorus Loadings from Agricultural Fields.

Computer models are commonly used for predicting risks of runoff P loss from agricultural fields by enabling simulation of various management practices and climatic scenarios. For P loss models to be useful tools, however, they must accurately predict P loss for a wide range of climatic, physiographic, and land management conditions. A complicating factor in developing and evaluating P loss models is the relative scarcity of available measured field data that adequately capture P losses before and after implementing management practices in a variety of physiographic settings. Here, we describe the development of the P Loss in runoff Events from Agricultural fields Database (PLEAD)-a compilation of event-based, field-scale dissolved and/or total P loss runoff loadings from agricultural fields collected at various research sites located in the US Heartland and southern United States. The database also includes runoff and erosion rates; soil-test P; tillage practices; planting and harvesting rates and practices; fertilizer application rate, method, and timing; manure application rate, method, and timing; and livestock grazing density and timing. In total, >1800 individual runoff events-ranging in duration from 0.4 to 97 h-have been included in the database. Event runoff P losses ranged from <0.05 to 1.3 and 3.0 kg P ha for dissolved and total P, respectively. The data contained in this database have been used in multiple research studies to address important modeling questions relevant to P management planning. We provide these data to encourage additional studies by other researchers. The PLEAD database is available at .

Manure application timing drives energy absorption for snowmelt on an agricultural soil

Reducing agricultural runoff year-round is important, in particular during snowmelt events on landscapes that receive wintertime applications of manure. To help inform manure guidelines, process-level data are needed that link management scenarios with the complexity of snowmelt, hence runoff. Albedo and radiative energy fluxes are strong drivers of thaw, but applying these mechanistic measurements across multiple, plot-scale management treatments over time presents a logistical challenge. The objective of this study was to first develop a practical field approach to estimate winter albedo in plot-scale field research with multiple management scenarios. The second objective was to quantify the radiative drivers of snowmelt by measuring fluxes after wintertime liquid manure application. Six management treatments were tested in south-central Wisconsin during the winters of 2015–2016 and 2016–2017 with a complete factorial design: three manure application timings (early December, late January, and unmanured) and two tillage treatments (conventional tillage versus no-tillage). A multiple linear regression model was developed to estimate albedo with digital imagery and readily-obtained site characteristics. Manure timing had a significant effect on radiative energy fluxes and tillage was secondary. January applications of liquid manure produced an immediate and lasting decrease in albedo, which resulted in greater net radiation absorbed by snowpack and subsequent energy available for snowmelt. Later applications of liquid manure accelerated snowmelt, which increased runoff losses and posed a challenge for nutrient retention from the liquid manure during thaw.

Long‐Term Manure Application Effects on Nutrients and Selected Enzymes Involved in Their Cycling

Core Ideas We assessed long‐term manure rates and application times on soil nutrients and enzymes at two sites. Increasing manure rate enhanced soil fertility but hydrolase enzymes showed a quadratic trend. Manure application prior to period of heavy rainfall (spring and fall) was associated with phosphorus losses. Peroxidase and phenol oxidase activities declined with increasing manure application rates. Oxidative enzyme activities were good indices of long‐term soil organic carbon storage. We investigated how soil nutrients (soil organic carbon [SOC], nitrogen [N], and Mehlich‐3‐extractable phosphorus [P‐M3]) and enzymes involved in their cycling were impacted by 10 yr of beef cattle manure application at two sites in Nova Scotia, Canada: a dikeland site (silty clay loam) and an upland site (sandy loam site), under timothy (Phleum pratense L.) cover. Manure was applied at four rates (from 0 to 300 kg total N ha−1) at different times (spring, summer, early fall, and late fall). Activities of hydrolytic enzymes: β‐glucosidase (BG), cellobiohydrolase (CB), leucine aminopeptidase (LAP), and phosphomonoesterase (PME) and oxidative enzymes: phenol oxidase (PO), peroxidase (PP), were quantified. We hypothesize that manure application will increase soil nutrients and BG, CB, LAP, and PME activities and will decrease PO and PP activities. After 10 yr of manure application, compared to a control, soil pH, SOC, N, and P‐M3 increased linearly by 41, 45, and 125%, respectively, with increasing manure rate, while BG, CB, PME, and LAP activities showed a quadratic response. Conversely, enzymes degrading less labile components (PP and PO) declined with increasing manure rate. Higher SOC and P‐M3 contents and higher LAP activity were found at the upland site, whereas higher PME, PP, and PO activities were found at the dikeland site. Inverse relationships between PME activity and P‐M3 content and between PP activity and SOC or N content were found, whereas a positive correlation between N content and LAP activity was observed. Regular manure application is a good way to sustain soil fertility, with the extent of soil C storage controlled by soil type. The optimal rate and timing of manure application is essential, since application prior to periods of heavy rainfall is associated with phosphorus losses. Our results demonstrated that oxidative enzymes (PP and PO) are good indices of long‐term SOC storage. The lower their activity, the higher is the SOC sequestration.

Top-down constraints on global N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O emissions at optimal resolution: application of a new dimension reduction technique

Abstract. We present top-down constraints on global monthly N2O emissions for 2011 from a multi-inversion approach and an ensemble of surface observations. The inversions employ the GEOS-Chem adjoint and an array of aggregation strategies to test how well current observations can constrain the spatial distribution of global N2O emissions. The strategies include (1) a standard 4D-Var inversion at native model resolution (4° × 5°), (2) an inversion for six continental and three ocean regions, and (3) a fast 4D-Var inversion based on a novel dimension reduction technique employing randomized singular value decomposition (SVD). The optimized global flux ranges from 15.9 Tg N yr−1 (SVD-based inversion) to 17.5–17.7 Tg N yr−1 (continental-scale, standard 4D-Var inversions), with the former better capturing the extratropical N2O background measured during the HIAPER Pole-to-Pole Observations (HIPPO) airborne campaigns. We find that the tropics provide a greater contribution to the global N2O flux than is predicted by the prior bottom-up inventories, likely due to underestimated agricultural and oceanic emissions. We infer an overestimate of natural soil emissions in the extratropics and find that predicted emissions are seasonally biased in northern midlatitudes. Here, optimized fluxes exhibit a springtime peak consistent with the timing of spring fertilizer and manure application, soil thawing, and elevated soil moisture. Finally, the inversions reveal a major emission underestimate in the US Corn Belt in the bottom-up inventory used here. We extensively test the impact of initial conditions on the analysis and recommend formally optimizing the initial N2O distribution to avoid biasing the inferred fluxes. We find that the SVD-based approach provides a powerful framework for deriving emission information from N2O observations: by defining the optimal resolution of the solution based on the information content of the inversion, it provides spatial information that is lost when aggregating to political or geographic regions, while also providing more temporal information than a standard 4D-Var inversion.

Seasonal Manure Application Timing and Storage Effects on Field- and Watershed-Level Phosphorus Losses.

Timing of manure application to agricultural soils remains a contentious topic in nutrient management planning, particularly with regard to impacts on nutrient loss in runoff and downstream water quality. We evaluated the effects of seasonal manure application and associated manure storage capacity on phosphorus (P) losses at both field and watershed scales over an 11-yr period, using long-term observed data and an upgraded, variable-source water quality model called Topo-SWAT. At the field level, despite variation in location and crop management, manure applications throughout fall and winter increased annual total P losses by 12 to 16% and dissolved P by 19 to 40% as compared with spring. Among all field-level scenarios, total P loss was substantially reduced through better site targeting (by 48-64%), improving winter soil cover (by 25-46%), and reducing manure application rates (by 1-23%). At the watershed level, a scenario simulating 12 mo of manure storage (all watershed manure applied in spring) reduced dissolved P loss by 5% and total P loss by 2% but resulted in greater P concentrations peaks compared with scenarios simulating 6 mo (fall-spring application) or 3 mo storage (four-season application). Watershed-level impacts are complicated by aggregate effects, both spatial and temporal, of manure storage capacity on variables such as manure application rate and timing, and complexities of field and management. This comparison of the consequences of different manure storage capacities demonstrated a tradeoff between reducing annual P loss through a few high-concentration runoff events and increasing the frequency of low peaks but also increasing the annual loss.

Does Liquid Swine Manure Application Timing and Nitrapyrin Affect Corn Yield and Inorganic Soil Nitrogen?

Core Ideas Nitrapyrin (Instinct) effectively slowed nitrification of swine manure. Delaying fall application of swine manure increased corn yields and N availability. Instinct enhanced corn production in years with greater than normal precipitation. Fall application of liquid swine (Sus scrofa) manure (LSM) is preferred but it can increase N loss potential. Delaying application of LSM or adding a nitrification inhibitor could reduce N losses. This study measured the effects of LSM application timing and nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine] as Instinct on soil inorganic N and corn (Zea mays L.) production. Field experiments were conducted from 2010 through 2014 on clay loam soils (Aquic Hapludolls). Treatments consisted of two fall application timings (early and late) and three rates (0, 2.56, and 5.11 L ha−1) of Instinct. Manure was injected 10‐cm deep at 134 kg of available N ha−1. Additional treatments included a control and 134 kg ha−1 of N as anhydrous ammonia (AA) with and without nitrapyrin as N‐Serve. Treatments were arranged in a randomized‐complete block design with four replicates. Late fall application of LSM and Instinct use resulted in greater fall and early spring NH4–N concentrations in manure bands. When averaged across years, LSM applied late increased corn grain yields 0.5 Mg ha−1 compared with early application and yields were 0.5 to 0.7 Mg ha−1 greater with Instinct than without. An interaction between main effects showed the yield response to Instinct was greatest when LSM was applied early. Total N uptake and removal were greater with Instinct than without Instinct. In this study, delaying LSM application until late fall (November) and using nitrapyrin (Instinct) increased corn yields and N uptake in years with greater than normal spring precipitation.

Greenhouse Gas Emissions from an Irrigated Dairy Forage Rotation as Influenced by Fertilizer and Manure Applications

Core Ideas Urea formulated with urease and nitrification inhibitors can reduce N2O emissions. Nitrous oxide‐N emission losses as a percentage of total N applied were ≤0.21%. Timing of manure application did not affect N2O, CO2, and CH4 fluxes. Soil was a CH4 sink and emissions were not influenced by N source. Information is needed regarding the effect of N source on greenhouse gas (GHG) emissions from irrigated semiarid agricultural soils. We report N2O, CO2, and CH4 emissions from a silage corn (Zea mays L.) (2013)–barley (Hordeum vulgare L.) (2014)–alfalfa (Medicago sativa L.) (2015) rotation under conventional tillage and sprinkler irrigation. We evaluated the effectiveness of an enhanced‐efficiency fertilizer (SuperU, a stabilized granular urea with urease and nitrification inhibitors) to reduce N2O emissions compared with granular urea and to determine GHG emissions from fall‐applied dairy manure or composted dairy manure and spring‐applied dairy manure. Nitrogen was applied during the first 2 yr of the study. SuperU plots emitted 53% less N2O than urea with corn, whereas no emission reductions occurred in 2014 with barley. The N2O‐N emission losses as a percentage of total N applied were 0.21 and 0.04% for urea and SuperU in 2013, respectively, with losses of 0.05% from both urea fertilizers in 2014. On average, N2O fluxes from fall and spring manure were statistically similar and greater than the other N treatments in 2014 and a lasting manure treatment effect on emissions occurred under alfalfa. Carbon dioxide fluxes were greatest from fall‐ and spring‐applied manure during the first 2 yr. Methane fluxes were negative, indicating microbial oxidation, and no differences occurred among the treatments. Corn, barley, and alfalfa yields were similar among all N treatments. This work demonstrates that SuperU can reduce N2O emissions from irrigated cropping systems in the semiarid western United States without affecting yields.

Modelling trends in ammonia in the Netherlands over the period 1990–2014

This study investigates to what extent emissions of ammonia, physicochemical processes and meteorology affect the trend in the atmospheric ammonia in the Netherlands between 1993 and 2014. Two distinct periods were distinguished: a period of declining ammonia concentrations between 1993 and 2004 and a period of slightly increasing ammonia concentrations between 2005 and 2014. In the first period, large emission reductions were reported, while the second period is characterized by smaller emission reductions. The Operational Priority Substances (OPS) model was used to quantify the effects of meteorology and physicochemical processes on atmospheric ammonia concentrations. The general performance of the OPS model for ammonia concentration, ammonium concentration and wet deposition of ammonia/ammonium is quite good when evaluated with observations over the whole period. For the period 1993–2004, model sensitivity runs show that the change in atmospheric chemical conditions and specific meteorological conditions can largely explain the smaller decline in ammonia concentrations compared with the decline in ammonia emissions. Uncertainties in emissions such as changes in the timing of manure applications and uncertainties in the estimated excretion and grazing emissions might partly explain remaining differences at the beginning of the period. Low-emission manure spreading techniques have an important reducing effect on the atmospheric ammonia concentration. Without these techniques, the ammonia concentrations at the measurement stations would have been about 3.5–4 μg m−3 higher in recent years. In the period between 2005 and 2014 emissions declined at a much lower rate, but the observed concentrations increased slightly. One third of the observed difference in trends can again be explained by the changed chemical conditions while no explanation has yet been found for the rest.

Year‐Round Nitrous Oxide Emissions as Affected by Timing and Method of Dairy Manure Application to Corn

Core Ideas The year × timing interaction affects cumulative N2O emissions. Injection of manure produces the highest cumulative N2O emissions. Injection of manure produces the highest corn yields. Manure application to agricultural soils enhances N2O emissions, but these emissions could be reduced by using improved application methods at the right time. We conducted a 3‐yr study on corn (Zea mays L.) grown in Elora, ON, Canada, to test the effects of timing and method of liquid dairy manure application on year‐round N2O emissions. A randomized complete block design was set up every year evaluating two application times (fall vs. spring) and three methods of manure application (surface broadcasting, incorporation, and injection). Lower cumulative N2O emissions for fall than spring application (mean ± standard error = 1.2 ± 0.3 vs. 2.9 ± 0.3 kg N2O‐N ha−1) were found during the driest year (2012), whereas no differences in emissions occurred between application timing in near‐normal precipitation years (2013 and 2014). Nitrous oxide emissions were not affected by the timing × method of application interaction. Injected manure resulted in cumulative N2O emissions not different than surface broadcast manure (3.6 ± 0.5 vs. 3.0 ± 0.5 kg N2O‐N ha−1) but significantly higher than incorporated manure (2.2 ± 0.3 kg N2O‐N ha−1). Injection resulted in greater corn yields than the other two methods. Our results suggest that (i) method of application affects N2O emissions independently of timing; (ii) including N2O emissions for the non‐growing season avoided biased estimates for the fall application timing since 20 to 60% of total emissions occurred during this period; and (iii) incorporating manure is the best practice to mitigate N2O emissions, although if N rates are optimized, injection could potentially produce yields with low N2O intensity.

Coupling Dairy Manure Storage with Injection to Improve Nitrogen Management: Whole‐Farm Simulation Using the Integrated Farm System Model

Core Ideas Manure storage and injection strategies were simulated using the Integrated Farming Systems Model. Strategies were verified using field data. We compared manure storage in environmental and economic model outputs. Introducing 6 mo of storage on a PA dairy farm decreased whole‐farm NUE without manure injection. Manure injection and 6 mo of storage gave the best combination of profit and environmental outcome. Application of livestock manure to farm soils represents a priority nutrient management concern in the Chesapeake Bay watershed. Historically, strong emphasis has been placed on adding manure storage to dairy operations, with the recognition that manure application methods can be improved. The Integrated Farm System Model was used to simulate manure management on a typical Pennsylvania dairy farm (100 milking cows, 80 ha). Converting the operation from daily haul to 6 mo of storage with broadcast application did not substantially change nitrogen (N) losses to the environment. However, switching to manure injection conserved ammonium N and improved manure N use efficiency by crops, even though it increased N leaching by 27% with 6‐mo storage and 13% with 12‐mo storage. Increasing manure storage from 6 to 12 mo with manure injection reduced nitrate N leaching by 38%, due to better timing of manure application to crop growth, but lowered annual net returns. Overall, manure injection and 6 mo of storage resulted in the best combination of profit and environmental outcome.

Poultry Manure Nitrogen Availability Influences Winter Wheat Yield and Yield Components

Standard poultry manure use recommendations in North Carolina consider waste analysis but not differences among manure types, cropping seasons, or application timing. This study evaluated poultry manure source, N rate strategy, and application time effects on soft red winter wheat (Triticum aestivum L.) tiller density, yield components, grain yield, and N availability coefficients. Coefficients included fertilizer N equivalence based on grain yield and plant‐available N based on aboveground plant N content. Four field experiments used broiler litter (BL) and composted layer manure (CLM), two rates (67 and 134 kg total‐N ha−1), and three different application times (incorporated in October preplant, Feekes’ 3 in December/January, or Feekes’ 4 in February). Dual‐source treatments received 67 kg N ha−1 of manure plus 67 kg N ha−1 as urea ammonium nitrate (UAN) solution at Feekes’ 5. Fertilizer‐N (UAN) rate treatments (0, 39, 78, 117, and 156 kg N ha−1) were also included. Yields responded to N inputs but were lowest when BL and CLM were applied at 67 kg N ha−1 either preplant or at Feekes’ 3. Grain yield and N availability were greater with CLM than with BL (3.0 vs. 2.8 t ha−1 grain and 58 vs. 52 kg ha−1 N uptake, respectively). Availability coefficients ranged from 12 to 32%, lower than the standard assumed values of 50 to 60%. The feasible poultry manure application window includes preplant until Feekes’ 4, but fertilizing winter wheat crops solely with poultry manure may supply less N than intended.

Effect of methods and time of poultry manure application on soil and leaf nutrient concentrations, growth and fruit yield of tomato (Lycopersicon esculentum Mill)

In order to obtain maximum economic value of plant nutrients in poultry manure and increase in tomato yield, field experiments were conducted at Owo, southwest Nigeria, during 2012 and 2013 early cropping seasons to study the effect of two methods (broadcasting on the soil surface and the incorporated) and four times (3weeks before transplanting (3 WBTP), 0week at transplanting (0 WATP), 3weeks after transplanting (3 WATP), and 6weeks after transplanting (6 WATP) of poultry manure (PM)) applications on soil chemical properties, leaf nutrient concentrations, growth and yield of tomato. The eight treatments were factorially arranged in a randomized block design with 3 replications. Results showed that PM incorporated into the soil produced higher soil organic matter and soil and leaf N, P, K, Ca, Mg, growth and yield (0.9tha−1) of tomato compared with broadcast method. Also PM applied at 3 WBTP had higher leaf nutrient concentrations and better growth and yield of tomato compared with 0 WATP, 3 WATP and 6 WATP. The higher yield of 3 WBTP was adduced to better synchrony between crop demand and nutrient supply. Using the mean of the two years, 3 WBTP increased tomato fruit yield by 4.0, 2.8 and 1.5tha−1 compared with 6 WATP, 3 WATP and 0 WATP, respectively. This yield difference can be economical on large scale tomato production. Therefore application of PM at 3 WBTP with incorporated method is recommended for tomato cultivation in the forest-savanna transition zone of southwest Nigeria.

The effects of pig manure type and application timing and frequency on nitrate leaching from a seven‐course arable rotation on a retentive alluvial soil

AbstractManagement rules for integrating manure applications into arable crop rotations have generally been developed from short‐term studies. The aim of this experiment was to test whether they would apply to frequent applications across an entire crop rotation. The hypothesis was that by avoiding autumn manure applications and adjusting fertilizer inputs to account for manure nitrogen (N) inputs, frequent manure applications could be made to a rotation without increasing N leaching compared with a control that received inorganic fertilizer according to the recommended rates. Four separate manure management strategies with varying manure types (pig slurry vs. pig farmyard manure), timing (autumn/winter vs. spring) and frequency (4–7 applications in 7 yrs) were superimposed on the rotation and compared with a treatment that received no manure. The rotation comprised cereals, potatoes, sugar beet and fallow and was undertaken on a retentive marine silt soil in Eastern England. The results demonstrated that by reducing fertilizer N inputs (by 14–54%, depending on manure type and application frequency) to account for manure N and by avoiding autumn applications of slurry, applications could be made as regularly as 6 yrs in seven without increasing N leaching, compared with an inorganic fertilizer control. Yields were at least the same as the inorganic fertilizer control from all manure treatments. This result contrasts with previous work which demonstrated that less frequent manure applications were necessary on a sandy soil. Soil type is therefore an important consideration when developing guidelines. The message is generally positive: fertilizer savings, similar or better yields and no extra leaching can be achieved over a rotation by careful manure management.

Evaluation of greenhouse gas emissions from hog manure application in a Canadian cow–calf production system using whole-farm models

The development of beneficial management practices is a key strategy to reduce greenhouse gas (GHG) emissions from animal agriculture. The objective of the present study was to evaluate the impact of time and amount of hog manure application on farm productivity and GHG emissions from a cow–calf production system using two whole-farm models. Detailed model inputs (climate, soil and manure properties, farm operation data) were collected from a 3-year field study that evaluated the following three treatments: no application of hog manure on grassland (baseline); a single application of hog manure on grassland in spring (single); and two applications of hog manure as fall and spring (split). All three treatments were simulated in a representative cow–calf production system at the farm-gate using the following whole-farm models: a Coupled Components Model (CCM) that used existing farm component models and the Integrated Farm System Model (IFSM). Annual GHG intensities for the baseline scenario were 17.7 kg CO2-eq/kg liveweight for CCM and 18.1 kg CO2-eq/kg liveweight for IFSM. Of the total farm GHG emissions, 73–77% were from enteric methane production. The application of hog manure on grassland showed a mean emission increase of 7.8 and 8.4 kg CO2-eq/kg liveweight above the baseline for the single and split scenarios, respectively. For the manured scenarios, farm GHG emissions were mainly from enteric methane (47–54%) and soil nitrous oxide (33–41%). Emission estimates from the different GHG sources in the farm varied between models for the single and split application scenarios. Although farm productivity was 3–4% higher in the split than in single application (0.14 t liveweight/ha), the environmental advantage of applying manure in a single or split application was not consistent between models for farm emission intensity. Further component and whole-farm assessments are required to fully understand the impact of timing and the amount of livestock manure application on GHG emissions from beef production systems.

Organic amendment effects on potato productivity and quality are related to soil microbial activity

Applying manure to row-crop systems can reduce inorganic fertilizer dependence and enhance soil biology and crop yields. However, it remains unclear whether low manure application rates or semi-annual application rates can provide these benefits. Our objective was to evaluate the effects of variable rates and timing of manure application on soil microbial processes and crop performance in a potato-corn cropping system. We tested the effects of five manure application rates of 0.0 (Ctrl), 1.54 (T1), 3.08 (T2), 6.16 (T3), and 12.32 (T4) Mg C ha−1 on potato productivity, severity of common scab, and soil biological processes. The highest rates of manure application consistently increased crop yields but even the lowest rate (1.54 Mg C ha−1) increased potato and corn yields. The severity of common scab incidence on daughter tubers was reduced by treatments T2, T3, and T4 in year one but was unaffected by any treatment in year two. Yield increases and reduced common scab severity were related to increased activities of C- and N-acquiring enzymes and microbial biomass C and N. Manure application rates of <2 Mg C ha−1 can provide crop and soil benefits that appear to increase with multiple applications, while higher application rates provide stronger and more consistent effects on yields, and especially soil biological properties related to nutrient cycling and organic matter dynamics.