Manure application technology in reduced tillage and forage systems: a review

Analyzing the Influence of Conservation Tillage and Manure on Soil Parameter Modulations in Croplands

Nowadays, when the human impact on the environment becomes prominent daily, specific steps are needed to mitigate or halt those changes. By far, agricultural land is most affected by the degradation process, leading to soil erosion and decreased soil quality. Sustainable measures are needed to find a solution to that problem. This study, located in an agricultural area in northwestern Croatia, gives an insight into how different tillage systems (conventional and conservation) with the addition of manure will affect soil physicochemical properties, hydrology response, and overall yield. To assess hydrological response, a rainfall simulator was used; meanwhile, soil samples were taken to determine bulk density, soil water content, water-stable aggregates, and soil organic matter. Soil water content did not show significant differences, whereas bulk density and penetration resistance yielded significantly higher values at 15-30 cm depth compared to 0-15 cm depth. Also, the conservation manure recorded lower bulk density and penetration resistance values than conventional tilled treatments. Water-stable aggregates and soil organic matter were severely affected by manure addition and yielded an increase after harvest. Hydrological response was delayed for the treatments with manure addition. Crop yield was also significantly higher for the conventional treatment with manure addition, whereas the control plots had lower yields. The results of this study show the positive aspects of conservation tillage, especially with manure addition, where soil quality is preserved or even increased.

Influence of manure application method on veterinary medicine losses to water

Veterinary medicines are routinely used within modern animal husbandry, which results in frequent detections within animal manures and slurries. The application of manures to land as a form of organic fertiliser presents a pathway by which these bioactive chemicals can enter the environment. However, to date, there is limited understanding regarding the influence of commonly used manure application methods on veterinary medicine fate in soil systems. To bridge this knowledge gap, a semi-field study was conducted to assess the influence of commonly used application methods such as, broadcast, chisel sweep, and incorporation on veterinary medicine losses to waters. A range of veterinary medicines were selected and applied as a mixture; these were enrofloxacin, florfenicol, lincomycin, meloxicam, oxytetracycline, sulfadiazine, trimethoprim and tylosin. All the assessed veterinary medicines were detected within surface runoff and leachates, and the concentrations generally decreased throughout the irrigation period. The surface runoff concentrations ranged from 0.49 to 183.47 μg/L and 2.26-236.83 μg/L for the bare soil and grass assessments respectively. The leachate concentrations ranged from 0.04 to 309.66 μg/L and 0.33-37.79 μg/L for the bare soil and grass assessments respectively. More advanced application methods (chisel sweep) were found to significantly reduce the mass loads of veterinary medicines transported to surface runoff and leachate by 13-56% and 49-88% over that of broadcast. Incorporating pig slurries reduced the losses further with surface runoff and leachate losses being 13-56% and 49-88% lower than broadcast. Our results show that manure application techniques have a significant effect on veterinary medicine fate in the environment and as such these effects should be considered in the decision-making processes for the management of manures as well as from a risk mitigation perspective for aquatic compartments.

Water quality benefits of weather-based manure application timing and manure placement strategies

The timing of manure application and placement of manure significantly affects manure nutrient use efficiency and the amount of nutrient lost from a field. Application of manure prior to a minimal precipitation period, and manure application through incorporation, reduces risks associated with nutrient loss through surface runoff. The current study aims to explore potential water quality impacts related to manure application strategies on the timing of application and approach (surface broadcasting or incorporation). The Soil and Water Assessment Tool (SWAT) was used to represent manure application scenarios and quantify potential water quality impacts in Susquehanna River Basin located in the Mid-Atlantic region of the United States. A baseline (business-as-usual) scenario was developed with manure application based on crop planting date and manure storage availability, and surface broadcasting as the application approach. The baseline was compared with a strategically timed manure application considering weather forecasting and manure incorporation. The strategic, weather-based manure application approach reduced TN and TP loading at the outlet by 4% and 6%, respectively. Manure incorporation simulations considering low-disturbance injection showed significant reduction of about 19% for TN and 44% for TP at the watershed outlet. Winter closure of manure application could reduce organic nutrient loss. Winter application of manure in 21% of row cropped areas (2% of whole watershed area) increased organic N and P loading by 10% and 4%, respectively, at watershed outlet.

Subsurface Manure Injection Reduces Surface Transport of Antibiotic Resistance Genes but May Create Antibiotic Resistance Hotspots in Soils

Compared to surface application, manure subsurface injection reduces surface runoff of nutrients, antibiotic resistant microorganisms, and emerging contaminants. Less is known regarding the impact of both manure application methods on surface transport of antibiotic resistance genes (ARGs) in manure-amended fields. We applied liquid dairy manure to field plots by surface application and subsurface injection and simulated rainfall on the first or seventh day following application. The ARG richness, relative abundance (normalized to 16s rRNA), and ARG profiles in soil and surface runoff were monitored using shotgun metagenomic sequencing. Within 1 day of manure application, compared to unamended soils, soils treated with manure had 32.5-70.5% greater ARG richness and higher relative abundances of sulfonamide (6.5-129%) and tetracycline (752-3766%) resistance genes (p ≤ 0.05). On day 7, soil ARG profiles in the surface-applied plots were similar to, whereas subsurface injection profiles were different from, that of the unamended soils. Forty-six days after manure application, the soil ARG profiles in manure injection slits were 37% more diverse than that of the unamended plots. The abundance of manure-associated ARGs were lower in surface runoff from manure subsurface injected plots and carried a lower resistome risk score in comparison to surface-applied plots. This study demonstrated, for the first time, that although manure subsurface injection reduces ARGs in the runoff, it can create potential long-term hotspots for elevated ARGs within injection slits.

Role of Organic and Conservation Agriculture in Ammonia Emissions and Crop Productivity in China

There is an increasing food demand with growing population and limited land for agriculture. Conventional agriculture with nitrogen (N) fertilizer applications, however, is a key source of ammonia (NH₃) emissions that cause severe haze pollution and impair human health. Organic and conservation agricultural (OCA) practices are thereby recommended to address these dual challenges; however, whether OCA provides cobenefits for both air quality and crop productivity is controversial. Here, we perform a meta-analysis and machine learning algorithm with data from China, a global hotspot for agricultural NH₃ emissions, to quantify the effects of OCA on NH₃ emissions, crop yields and nitrogen use efficiency (NUE). We find that the effects of OCA depend on soil and climate conditions, and the 40-60% substitution of synthetic fertilizers with livestock manure achieves the maximum cobenefits of enhanced crop production and reduced NH₃ emissions. Model forecasts further suggest that the appropriate application of livestock manure, straw return, and no-till could increase grain production up to 59.7 million metric tons (100% of straw return) and reduce maximum US$2.7 billion (60% substitution with livestock manure) in damage costs to human health from NH₃ emissions by 2030. Our findings provide data-driven pathways and options for achieving multiple sustainable development goals and improving food systems and air quality in China.

Culturable antibiotic-resistant fecal coliform bacteria in soil and surface runoff after liquid dairy manure surface application and subsurface injection

Land application of manure, while beneficial to soil health and plant growth, can lead to an overabundance of nutrients and introduction of emerging contaminants into agricultural fields. Compared with surface application of manure, subsurface injection has been shown to reduce nutrients and antibiotics in surface runoff. However, less is known about the influence of subsurface injection on the transport and persistence of antibiotic-resistant microorganisms. We simulated rainfall to field plots at two sites (one in Virginia and one in Pennsylvania) 1 or 7 d after liquid dairy manure surface and subsurface application (56 Mg ha^-1 ) and monitored the abundance of culturable antibiotic-resistant fecal coliform bacteria (ARFCB) in surface runoff and soils for 45 d. We performed these tests at both sites in spring 2018 and repeated the test at the Virginia site in fall 2019. Manure subsurface injection, compared with surface application, resulted in less ARFCB in surface runoff, and this reduction was greater at Day 1 after application compared with Day 7. The reductions of ARFCB in surface runoff because of manure subsurface injection were 2.5-593 times at the Virginia site in spring 2018 and fall 2019 and 4-5 times at the Pennsylvania site in spring 2018. The ARFCB were only detectable in the 0-to-5-cm soil depth within 14 d of manure surface application but remained detectable in the injection slits of manure subsurface-injected plots even at Day 45. This study demonstrated that subsurface injection can significantly reduce surface runoff of ARFCB from manure-applied fields.

Review: Closing nutrient cycles for animal production - Current and future agroecological and socio-economic issues

We face an urgent and complex challenge to produce large amounts of healthful animal and plant foods for an estimated 10 billion people by 2050 while maintaining essential ecosystem services. To compound this challenge, we must do so while not further degrading our environment and conserving essential nutrients such as copper, magnesium, phosphorus, selenium, and zinc that are in short supply for fertilization. Much good research has been done, but to meet this challenge, we need to greatly increase on-farm and watershed-scale research including on-farm evaluations and demonstrations of the putative best combinations of stewardship techniques over multiple years in real-world settings, which are backed by data on nutrient inputs, soil, air, and water chemistry (fluxes) and water discharge. We also need to work with farmers, specialists, and generalists in highly creative interdisciplinary teams that resist forming silos and that use combinations of techniques linked to agroecology and industrial ecology in combination with state-of-the-art engineering. Some of these research and demonstration farms need to be in catchments prone to pollution of aquatic and terrestrial ecosystems with nitrogen, phosphorus, and other nutrients. Some promising approaches include mixed crop-livestock systems, although these alone may not be productive enough without updating to meet the dietary needs of an estimated 10 billion people by 2050. Other approaches could be state-of-the-art multi-trophic production systems, which include several species of plants integrated into production with vertebrates (e.g., ruminants, pigs, poultry), invertebrates (e.g., insects, earthworms) and fish, shrimp, or crayfish to utilize wasted feed and excreta, and recycle nutrients back to the animals (via plants or invertebrates) in the systems. To cut costs and increase desirable outputs, we must recycle nutrients much better within our food production systems and produce both animal and plant foods more efficiently as nutrients cycle through systems.

Impacts of low-disturbance dairy manure incorporation on ammonia and greenhouse gas fluxes in a corn silage-winter rye cover crop system

Manure and fertilizer applications contribute to greenhouse gas (GHG) and ammonia (NH₃ ) emissions. Losses of NH₃ and nitrous oxide (N₂ O) are an economic loss of nitrogen (N) to farms, and methane (CH₄ ), N₂ O, and carbon dioxide (CO₂ ) are important GHGs. Few studies have examined the effects of low-disturbance manure incorporation (LDMI) on both NH₃ and GHG fluxes. Here, NH₃ , N₂ O, CH₄ , and CO₂ fluxes in corn (Zea mays L.)-winter rye (Secale cereale L.) field plots were measured under fall LDMI (aerator/band, coulter injection, strip-till, sweep inject, surface/broadcast application, broadcast-disk) and spring-applied urea (134 kg N ha^-1 ) treatments from 2013 to 2015 in central Wisconsin. Whereas broadcast lost 35.5% of applied ammonium-N (NH₄ -N) as NH₃ -N, strip-till inject and coulter inject lost 0.11 and 4.5% of applied NH₄ -N as NH₃ , respectively. Mean N₂ O loss ranged from 2.7 to 3.6% of applied total N for LDMI, compared with 4.2% for urea and 2.6% for broadcast. Overall, greater CO₂ fluxes for manure treatments contributed to larger cumulative GHG fluxes compared with fertilizer N. There were few significant treatment effects for CH₄ (P > .10); however, fluxes were significantly correlated with changes in soil moisture and temperature. Results indicate that LDMI treatments significantly decreased NH₃ loss but led to modest increases in N₂ O and CO₂ fluxes compared with broadcast and broadcast-disk manure incorporation. Tradeoffs between N conservation versus increased GHG fluxes for LDMI and other methods should be incorporated into nutrient management tools as part of assessing agri-environmental farm impacts.

Influence of Soil and Manure Management Practices on Surface Runoff Phosphorus and Nitrogen Loss in a Corn Silage Production System: A Paired Watershed Approach

Best management practices (BMPs) can mitigate erosion and nutrient runoff. We evaluated runoff losses for silage corn management systems using paired watershed fields in central Wisconsin. A two-year calibration period of fall-applied liquid dairy manure incorporated with chisel plow tillage (FMT) was followed by a three and a half-year treatment period. During the treatment period FMT was continued on one field, and three different systems on the others: (a) fall-applied manure and chisel tillage plus a vegetative buffer strip (BFMT); (b) a fall rye cover crop with spring manure application and chisel tillage (RSMT), both BMPs; a common system (c) fall manure application with spring chisel tillage (FMST). Year-round runoff monitoring included flow, suspended sediment (SS), total phosphorus (TP), dissolved reactive phosphorus (DRP), ammonium (NH4+-N), nitrate, and total nitrogen (TN). Results showed BFMT reduced runoff SS, TP, and TN concentration and load compared to FMT. The RSMT system reduced concentrations of SS, TP, and TN, but not load because of increased runoff. The FMST practice increased TP, DRP, and NH4+-N loads by 39, 376, and 197%, respectively. While BMPs showed mitigation potential for SS, TN, and TP, none controlled DRP, suggesting additional practices may be needed in manured corn silage fields with high runoff potential.

Benefits and tradeoffs of reduced tillage and manure application methods in a Zea mays silage system

A critical question is whether there are agricultural management practices that can attain the multiple management goals of increasing yields, preventing nutrient losses, and suppressing greenhouse gas (GHG) emissions. No-till and manure application methods, such as manure injection, can enhance nutrient retention, but both may also enhance emissions of nitrous oxide (N₂ O), a powerful GHG. We assessed differences in soil N₂ O and carbon dioxide (CO₂ ) emissions, nitrate and ammonium retention, and crop yield and protein content under combinations of vertical-till, no-till, manure injection, and manure broadcast without incorporation in a corn (Zea mays L.) silage system. During the growing seasons of 2015-2017, GHG emissions and soil mineral nitrogen (N) were measured every other week or more frequently after management events. Crop yield and protein content were measured annually at harvest. No-till reduced CO₂ emissions but had no impact on N₂ O emissions relative to vertical-till. Manure injection increased N₂ O and CO₂ emissions, with the magnitude of this effect being greatest for 1 mo post-application. Manure injection also increased soil ammonium and nitrate but did not increase yield or crop quality relative to broadcast application. Similarly, tillage did not affect crop yield or protein content. Despite the tradeoffs between mineral N retention and elevated GHG emissions, manure injection in no-till systems benefits farmers by reducing soil carbon losses as CO₂ , retaining mineral N, and maintaining crop yields and quality.

Influence of low-disturbance fall liquid dairy manure application on corn silage yield, soil nitrate, and rye cover crop growth

Tillage incorporation of manure can mitigate nutrient loss but increases erosion potential and damages cover crops. More information on the effects of low-disturbance manure application (LDMA) on corn yield, cover crop establishment, and soil properties is needed to better predict manure management practice trade-offs. Here, corn silage (Zea mays L.) yield, winter rye (Secale cereale L.) establishment, and soil nitrate concentrations were compared for a range of manure application methods, including broadcast incorporation, broadcast/disk, fertilizer N (spring applied at 67, 134, and 202 kg N ha^-1 ), and a no-manure control, at the University of Wisconsin's Marshfield Agricultural Research Station from 2012 to 2015. Compared with the control, manure and fertilizer N treatments increased corn yield by an average of 1.1- to 1.6-fold and 1.4- to 1.6-fold, respectively. Of the LDMA treatments (sweep-, strip till-, and coulter-injection; aerator/band; broadcast), corn yield was greatest for sweep injection, which did not differ from the high N fertilizer rate (P < .0001). Corn yield averaged across LDMA treatments did not differ from the 134 or 202 kg N ha^-1 yields. Compared with disking, LDMA maintained more crop residue (P < .0001), with levels comparable to the control. Soil nitrate-N at depths of 0-30 and 30-60 cm was influenced by LDMA and fertilizer N; however, leaching to 60-90 cm was comparable among treatments. Results indicate that LDMA with injection conserved more N, caused less damage to winter rye, and had similar yields to fertilizer N treatments with improved soil aggregate stability and higher total carbon content.

Runoff water quality after low-disturbance manure application in an alfalfa-grass hay crop forage system

The impacts of low-disturbance manure application (LDMA) on runoff water quality in hay crop forages are not well known. Our objective in this study was to determine surface runoff losses of total nitrogen (TN), ammonium N (NH₄ -N), nitrate N (NO₃ -N), total phosphorus (TP), dissolved reactive P (DRP), and suspended sediment from alfalfa (Medicago sativa L.)-grass plots in central Wisconsin after surface broadcasting manure and LDMA compared with no application. Treatments were (a) surface banding (BAND), (b) surface banding with aeration (A/B), (c) shallow disk injection (INJECT), (d) surface broadcast (BCAST), and (e) a no-manure control (CONT). Runoff events were generated (n = 7) from replicated plots following a standardized rainfall simulation protocol. Although runoff was variable across plots and within treatments, mean runoff concentrations of TN (P = .03), NH₄ -N (P = .03), TP (P = .001), and DRP (P < .0001) were lower for incorporated (INJECT and A/B) vs. unincorporated (BCAST and BAND) treatments. INJECT had lower mean DRP concentration (P = .02) than A/B and was similar to CONT and had lower cumulative TN (P = .05), TP (P = .07), and DRP (P = .01) loads than A/B. Additionally, TP, TN, DRP, and NH₄ -N loads and concentrations were strongly related with soil surface manure coverage extent (R² = 0.50-0.84; P < .0001), suggesting that manure was a main source of N and P losses. Although INJECT appeared to be the most effective in mitigating nutrient loss in surface runoff, more research is needed to determine LDMA impacts on farm economics, soil properties, and runoff water quality.

Winter-Season Gaseous Nitrogen Emissions in Subtropical Climate: Impacts of Pig Slurry Injection and Nitrification Inhibitor

Controlling nitrogen (N) losses from pig slurry (PS) is a challenge under no-till because amendments are left on the soil surface. We investigated the potential of shallow injection of PS, with and without addition of the nitrification inhibitor dicyandiamide (DCD), to abate gaseous ammonia (NH) and nitrous oxide (NO) emissions in winter crops in subtropical soils. Injection was compared with surface broadcasting of PS, with and without DCD. The significance of winter season on annual NO emissions was assessed. Injecting PS reduced NH volatilization compared with surface application. However, this reduction was partly offset because NO emissions increased by 77% (+1.53 kg NO-N ha) when PS was injected. Adding DCD to injected PS reduced NO emission below levels of surface-broadcast PS without the inhibitor, indicating that DCD may be a management option when injecting PS. Compared with a reference urea treatment, PS without DCD increased cumulative NO emissions 5.7-fold (from 613 to 3515 g NO-N ha) when injected, and 3.2-fold (from 613 to 1980 g NO-N ha) when surface applied. Adding DCD significantly reduced emissions with injected PS, whereas reduction was not always significant with surface-applied PS. Nitrous oxide emissions during the winter cropping season contributed 30 to 44% of annual emissions, indicating that controlling gaseous N losses in that season is required to reduce the environmental footprint of the whole cropping system. Overall, combining PS injection with DCD was an efficient practice for reducing winter-season gaseous N losses from no-till soils under subtropical climate.

Varying Influence of Dairy Manure Injection on Phosphorus Loss in Runoff over Four Years

Surface application of manure on no-till farms can exacerbate P losses in runoff, contributing to the eutrophication of surface waters. We monitored 12 400-m field plots over 4 yr to compare P losses in surface runoff and lateral subsurface flow with shallow disk injection and broadcast application of dairy manure. Given the substantial variability in annual P losses, as well as a gradual, annual buildup of residual soil test P, significant differences in runoff P losses were detected in only 1 of 4 yr: in 2014, total P losses in runoff were 68% greater from broadcast manure plots than injected manure plots. Dissolved and particulate P were roughly even in their contribution to runoff. Even so, there were significant relationships between annual dissolved P losses and P in the soil surface, which pointed to soils as a regular source of P in runoff. Overall, results confirm the potential for injection to reduce P loss in runoff relative to broadcast application, but because in a few sampling dates injection resulted in greater losses, this study also highlights the importance of assessing mitigation benefits of manure application practices over longer timeframes.

Nitrous Oxide and Ammonia Emissions from Injected and Broadcast-Applied Dairy Slurry

Trade-offs associated with surface application or injection of manure pose important environmental and agronomic concerns. Manure injection can conserve nitrogen (N) by decreasing ammonia (NH) volatilization. However, the injection band also creates conditions that potentially favor nitrous oxide (NO) production: an abundant organic substrate-promoting microbial activity, anaerobic conditions favoring denitrification, and large local concentrations of N. We assessed differences in NH volatilization and NO emissions with broadcast application versus shallow disk injection of dairy slurry during the 2011 to 2013 growing seasons on a well-drained silt loam that received average manure-N application rates of 180 kg N ha via injection or 200 kg N ha via broadcast. Ammonia emissions were measured using a photoacoustic gas analyzer and chambers, and NO emissions were measured using syringes to draw timed samples from vented chambers with analysis by gas chromatograph. Results point to a 92 to 98% (3.02-11.05 kg NH-N ha) reduction in NH volatilization (for the initial sampling) with injection compared with broadcasting manure but also reveal 84 to 152% (725.9-3187.8 g NO-N ha) greater cumulative NO emissions. Although losses of N via NO emission were at least three orders of magnitude less than NH volatilization, their potential role as a greenhouse gas is of concern. Despite the potential greenhouse gas trade-offs associated with shallow disk injection of manure, decreasing NH volatilization provides a substantial benefit, especially to farmers who are trying to conserve N and improve the N/P ratio of soil-applied manure.

Estrogen Transport in Surface Runoff from Agricultural Fields Treated with Two Application Methods of Dairy Manure

This study compares two methods of dairy manure application-surface broadcast and shallow disk injection-on the fate and transport of natural estrogens in surface runoff from 12 field plots in central Pennsylvania. Ten natural surface runoff events were sampled over a 9-mo period after fall manure application. Results show that the range of estrogen concentrations observed in surface runoff from the broadcast plots was several orders of magnitude higher (>5000 ng L) than the concentrations in runoff from the shallow disk injection plots (<10 ng L). Additionally, the transport dynamics differed, with the majority of the estrogen loads from the surface broadcast plots occurring during the first rainfall event after application, whereas the majority of the loads from the shallow disk injection plots occurred more than 6 mo later during a hail storm event. Total estrogen loads were, on average, two orders of magnitude lower for shallow disk injection compared with surface broadcast. Independent of the method of manure application, 17α-estradiol and estrone were preserved in the field for as long as 9 mo after application. Overall, injection of manure shows promise in reducing the potential for off-site losses of hormones from manure-amended soils.

Injection of Dicyandiamide-Treated Pig Slurry Reduced Ammonia Volatilization without Enhancing Soil Nitrous Oxide Emissions from No-Till Corn in Southern Brazil

There is a lack of information on how placement in soil and nitrification inhibitors affects nitrous oxide (NO) and ammonia (NH) emissions from pig slurry (PS) applied under no-till (NT) conditions. Our objective was to determine the impact of injecting PS and treating it with the nitrification inhibitor dicyandiamide (DCD) on NH and NO emissions from soils under NT in subtropical southern Brazil. The emissions of these gases were compared for shallow (∼ 10 cm) injection and surface broadcasting of PS with and without DCD (8.1-10.0 kg ha; 6.5-8.4% of applied NH-N). Measurements were made at two sites during two summer growing seasons under NT corn crops. Injection reduced NH volatilization by 70% but increased NO emissions 2.4-fold (from 2628 to 6198 g NO N ha) compared with surface broadcast application. Adding DCD to PS inhibited nitrification and reduced NO emissions by an average of 28% (730 g NO-N ha) for surface broadcast and 66% (4105 g NO-N ha) for injection but did not increase NH volatilization. Consequently, NO emission factors were much higher for injection (3.6%) than for surface broadcast (1.3%) application and were reduced (0.9%) when DCD was added to injected PS. In conclusion, the injection of DCD-treated slurry is a recommendable practice for reducing NH and NO emissions when applying PS on NT corn in southern Brazil.

Phosphorus losses from low-emission slurry spreading techniques

Low emission slurry spreading techniques are known to improve nitrogen use efficiency, but their impact on phosphorus (P) losses in surface runoff has received little attention. The current study was designed to examine the effect of slurry spreading technique on P losses in runoff. Twelve treatments were examined on 0.5- m by 1.0-m plots in a nominal 2 × 6 factorial design experiment. Treatments comprised grass swards at two different stages of growth, a stubble and a 4-wk regrowth, and six different slurry application treatments: control (no slurry), and slurry applied to simulate splash-plate, injection (across and down slope), and trailing shoe (across and down slope) spreading. Slurry was applied by hand (40 m ha). Rainfall simulations (40 mm h) were conducted at 2, 9, and 28 d post-slurry application. When slurry was applied to the stubble, dissolved reactive P (DRP) concentrations in runoff at Day 2 were 47 and 37% lower ( < 0.05) from the injection and trailing shoe treatments compared with the splash-plate treatment. Similarly, at Day 2, TP concentrations in runoff from the injection treatments were 27% lower ( < 0.05) than the splash-plate treatment. In contrast, application technique had no effect ( 0.05) on P concentrations in runoff following slurry application to the regrowth treatment. Phosphorus concentrations in runoff were unaffected by direction of slurry spreading (across or down) at both applications. Our results indicate that trailing shoe and injection techniques offer the potential to reduce DRP concentrations in runoff during the period immediately after slurry application.

Dairy slurry application method impacts ammonia emission and nitrate in no-till corn silage

Reducing ammonia (NH3) emissions through slurry incorporation or other soil management techniques may increase nitrate (NO3) leaching, so quantifying potential losses from these alternative pathways is essential to improving slurry N management. Slurry N losses, as NH3 or NO3 were evaluated over 4 yr in south-central Wisconsin. Slurry (i.e., dairy cow [Bos taurus] manure from a storage pit) was applied each spring at a single rate (-75 m3 ha(-1)) in one of three ways: surface broadcast (SURF), surface broadcast followed by partial incorporation using an aerator implement (AER-INC), and injection (INJ). Ammonia emissions were measured during the 120 h following slurry application using chambers, and NO3 leaching was monitored in drainage lysimeters. Yield and N3 uptake of oat (Avena sativa L.), corn (Zea mays L.), and winter rye (Secale cereale L.) were measured each year, and at trial's end soils were sampled in 15- to 30-cm increments to 90-cm depth. There were significant tradeoffs in slurry N loss among pathways: annual mean NH3-N emission across all treatments was 5.3, 38.3, 12.4, and 21.8 kg ha(-1) and annual mean NO3-N leaching across all treatments was 24.1, 0.9, 16.9, and 7.3 kg ha' during Years 1, 2, 3, and 4, respectively. Slurry N loss amounted to 27.1% of applied N from the SURF treatment (20.5% as NH3-N and 6.6% as NO,-N), 23.3% from AER-INC (12.0% as NH3-N and 11.3% as NO3-N), and 9.19% from INJ (4.4% as NH3-N and 4.7% as NO3-N). Although slurry incorporation decreased slurry N loss, the conserved slurry N did not significantly impact crop yield, crop N uptake or soil properties at trial's end.

Environmental and economic comparisons of manure application methods in farming systems

Alternative methods for applying livestock manure to no-till soils involve environmental and economic trade-offs. A process-level farm simulation model (Integrated Farm System Model) was used to evaluate methods for applying liquid dairy (Bos taurus L.) and swine (Sus scrofa L.) manure, including no application, broadcast spreading with and without incorporation by tillage, band application with soil aeration, and shallow disk injection. The model predicted ammonia emissions, nitrate leaching, and phosphorus (P) runoff losses similar to those measured over 4 yr of field trials. Each application method was simulated over 25 yr of weather on three Pennsylvania farms. On a swine and cow-calf beef operation under grass production, shallow disk injection increased profit by $340 yr(-1) while reducing ammonia nitrogen and soluble P losses by 48 and 70%, respectively. On a corn (Zea mays L.)-and-grass-based grazing dairy farm, shallow disk injection reduced ammonia loss by 21% and soluble P loss by 76% with little impact on farm profit. Incorporation by tillage and band application with aeration provided less environmental benefit with a net decrease in farm profit. On a large corn-and-alfalfa (Medicago sativa L.)-based dairy farm where manure nutrients were available in excess of crop needs, incorporation methods were not economically beneficial, but they provided environmental benefits with relatively low annual net costs ($13 to $18 cow). In all farming systems, shallow disk injection provided the greatest environmental benefit at the least cost or greatest profit for the producer. With these results, producers are better informed when selecting manure application equipment.

Novel manure management technologies in no-till and forage introduction to the special series

Surface application of manures leaves nitrogen (N) and phosphorus (P) susceptible to being lost in runoff, and N can also be lost to the atmosphere through ammonia (IH3) volatilization. Tillage immediately after surface application of manure moves manure nutrients under the soil surface, where they are less vulnerable to runoff and volatilization loss. Tillage, however, destroys soil structure, can lead to soil erosion, and is incompatible with forage and no-till systems. A variety of technologies are now available to place manure nutrients under the soil surface, but these are not widely used as surface broadcasting is cheap and long established as the standard method for land application of manure. This collection of papers includes agronomic, environmental, and economic assessments of subsurface manure application technologies, many of which clearly show benefits when comparedwith surface broadcasting. However, there remain significant gaps in our current knowledge, some related to the site-specific nature of technological performance, others related to the nascent and incomplete nature of the assessment process. Thus, while we know that we can improve land application of manure and the sustainability of farming systems with alternatives to surface broadcasting, many questions remain concerning which technologies work best for particular soils, manure types, and farming and cropping systems.