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Using dairy manure and legumes in crop rotations can reduce inorganic N inputs for corn (Zea mays L.), yet these practices can also contribute to nitrous oxide (N2O) emissions. In two crop rotations we investigated how different (i) organic and inorganic N amendments and (ii) prior legume crops with broadcast manure influenced direct N2O emissions from silt-loam soils planted to no-till corn. We measured N2O fluxes from April to December for two years using closed vented chambers from soils planted to corn with no spring residue to compare inorganic N fertilizer (S-UAN) and two liquid dairy manure application methods: surface broadcasted (S-BM) and injected (S-IM). Emissions were also measured to compare the effect of crop residue of perennial forages, a green manure legume, or soybean (Glycine max L. Merr.) from soils all amended with liquid dairy manure. Nitrous oxide emissions were greatest during the 15–45 days after manure was injected compared to broadcasting, and cumulative N2O emissions were larger from S-IM (2.8–2.5 kg ha−1) than S-BM (1.4–0.7 kg ha−1) and S-UAN (0.3 kg ha−1). Cumulative and yield-scaled N2O emissions did not differ among the prior legume treatments. A ranking approach based on random forests, identified the most important variable contributing to N2O emissions in both comparisons as corn growing degree days, indicative of the asynchrony of spring legume termination and manure application with corn planting and N use; and changing environmental conditions for N mineralization and denitrification.

Understanding the fate of nutrients in land-applied manure is key to improving the efficiency of their use in crop production. We developed nitrogen (N) budgets for 2 years of continuously cropped corn fertilized by dairy manure via broadcast application or shallow disk injection. Major pathways and pools of N loss were monitored on 12, 0.04 ha field lysimeters in central Pennsylvania, USA to estimate the impact of manure application method on N fate: gas emissions, off-site runoff (overland and subsurface flow), crop uptake, and, soil storage. The budgets illuminated trade-offs in N cycling with each management strategy. Crop removal accounted for the largest portions of manure N applied in both budgets (16–43%). Injection manure N balances were more difficult to close because balances included a large proportion of ‘unaccounted’ N (49% and 68% of applied N for two accounting periods). Even so, results point to cumulative differences in nutrient use efficiencies that can be attributed to the greater conservation of ammonia-N with manure injection. There was an apparent build-up of soil N with manure injection that was not observed with broadcast application (in pre sidedress nitrogen test measurements). However, these trends were preliminary; over the two growing seasons covered by this study, these findings did not result in significant differences in corn yield or crop N removal.

Warm season perennial grasses grown for biomass have been suggested as alternative cropping systems on marginal soils to increase farm profit, reduce nitrous oxide (N2O) emissions, and improve water quality. The objectives of this study were to determine: 1) how warm season perennial grasses, switchgrass (Panicum virgatum) and Miscanthus (Miscanthus x giganteus), compare to cool season grasses as streamside buffers on poorly drained marginal soils 2) if inorganic or organic nutrient additions improve biomass yield and affect environmental outcomes? 3) which soil variables influence N2O emissions in situ? We measured soil N2O emissions, soil solution nitrate (NO3−), ammonium (NH4+), O2, moisture, and temperature, along with shallow groundwater NH4+, NO3−, and ortho-phosphate during two growing seasons (2012–2013). N2O emissions were similar across unfertilized warm season grasses and cool season grasses. However, when switchgrass was fertilized with ammonium sulfate or broiler manure, N2O emissions increased significantly. N2O emissions were weakly correlated with soil solution NO3− concentrations and water filled pore space. Shallow groundwater N was elevated under switchgrass fertilized with ammonium sulfate, broiler manure, and when grown with the legume (Desmodium canadense) when compared to unfertilized switchgrass, Miscanthus, and cool season grasses. In 2013 dry aboveground biomass production did not differ among switchgrass treatments which averaged 10 Mg ha. Biomass production was significantly higher for Miscanthus (18.5 Mg ha). The results indicate that unfertilized switchgrass and Miscanthus are as effective as cool season grasses at mitigating N2O emissions and improving water quality, and that Miscanthus has potential production advantages over switchgrass grown on frequently saturated soils.

Management of manure and cereal rye (Secale cereale L.) has implications for crop production and nutrient cycling. This 1‐yr, full‐factorial experiment conducted in Pennsylvania quantified the effects of three management factors—(a) rye management (RyeM; early‐terminated cover crop [CC] vs. double crop harvested a week later [DC]), (b) manure application method (ManM; unincorporated broadcast manure [BM] vs. shallow disk injected manure [IM]), and (c) fall field operation prioritization (priority; manure priority [MP] manure application in late September with rye planting in mid‐October vs. rye priority [RP], rye planting in late September with manure application in early November)—on rye biomass, nutrient recovery, and forage yield and the effect of ManM and priority on DC forage nutritive value in a rye–corn (Zea mays L.) cropping sequence. This experiment was intended to be a repeated 2‐yr study, but due to MP treatment rye crop failure in the second year, the resulting 1‐yr dataset was analyzed to assess priority effects. Prioritizing rye planting in the fall with DC increased total forage production and apparent N recovery (ANR) when manure was broadcast. These results highlight the value of prioritizing fall rye planting in DC systems to increase rye spring biomass and nutrient recovery when manure is broadcast. More experiments should be conducted on fall field operation timing to develop reliable recommendations.

To avoid competition with food crops, biofuel feedstocks may need to be produced on economically marginal lands where yields are limited and replacement of existing vegetation will reduce soil C, foregoing some CO2 emission savings. Therefore, our first goal was to determine whether biochar application to marginal lands could improve switchgrass yield while sequestering sufficient soil C to eliminate the negative impact of cultivation. Because it may be difficult to obtain large quantities of biochar, our second goal was to compare small, incremental and large, all-at-once biochar applications. Our third goal was to determine whether biochar had any negative effects on earthworms, mycorrhizal fungi, soil bacteria, soil fungi, and soil enzyme activity. We grew switchgrass at two sites with poorly drained soils and two sites with excessively drained soils. Irrespective of site, biochar significantly increased yield when we rototilled in the entire amount before planting but not when we applied it incrementally between crop rows using a chisel plow. Biochar increased soil C stocks, in some cases increasing it beyond that found in soils of intact marginal land vegetation. Nevertheless, mixing biochar with soil had little or no impact on earthworm activity, mycorrhizal colonization, soil bacterial and fungal communities, and soil enzyme activities. We conclude that biochar may be part of an effective strategy for producing switchgrass on marginal lands, but the choice of application method depends on the relative importance of several considerations including biochar availability, switchgrass yield, C sequestration, soil erosion, and ease of application.

The aim of the current study was to identify major soil and leaf factors accounting for low natural rubber (NR, Hevea brasiliensis) productivity on tropical acid Acrisols in Vietnam. Twenty NR plot...

The livestock industries are a major contributor to the economy of the northeastern United States. Climate models predict increased average maximum temperatures, days with temperatures exceeding 25 °C, and higher annual precipitation in the Northeast. These environmental changes combined with increased atmospheric CO2 concentration are expected to either increase or decrease forage productivity depending on the crop, and may decrease protein content and forage digestibility. Winter damage to sensitive forage species may also increase. Predicted temperature increases are expected to reduce fertility in dairy cattle and heat stress-induced inflammation may limit energy available for productive functions. Additional loss in milk production due to decreased feed intake is estimated to be up to 1% of the projected annual milk production through 2100. The effects of climate change on the beef industry in the Northeast are expected to be minimal. Broiler production in the region may benefit from warmer winter and summer temperatures, but future housing will require greater insulation and ventilation fan capacity. Providing adequate housing and ventilation to offset climate changes will also be important for the layer industry and will likely increase the price of eggs. Climate change is expected to have an economic impact on the horse industry in the region through additional management of land and forage resources, building of shelters, and heat abatement at equine events. Increased temperatures and more intense storms will increase nutrient losses and gaseous emissions from animal manure. Uncertainties about how host animals, pathogens, and disease vectors will respond to climate change highlight the need for continued animal health monitoring.

Managing cropping systems to sequester soil organic C (SOC) improves soil health and resilience to changing climate. Perennial crops, no-till planting, manure, and cover crops can add SOC; however, their impacts have not been well documented in the northeastern United States. Our objectives were (i) to monitor SOC from a bioenergy cropping study in Pennsylvania that included a corn ( L.)-soybean [ (L.) Merr.]-alfalfa ( L.) rotation, switchgrass ( L.), and reed canarygrass ( L.); (ii) to use the CQESTR model to predict SOC sequestration in the bioenergy crops (with and without projected climate change); and (iii) to use CQESTR to simulate influence of tillage, manure, cover cropping, and corn stover removal in typical dairy forage (silage corn-alfalfa) or grain corn-soybean rotations. Over 8 yr, measured SOC increased 0.4, 1.1, and 0.8 Mg C ha yr in the bioenergy rotation, reed canarygrass, and switchgrass, respectively. Simulated and measured data were significantly correlated ( < 0.001) at all depths. Predicted sequestration (8-14 Mg C ha over 40 yr) in dairy forage rotations was much larger than with corn-soybean rotations (-4.0-0.6 Mg C ha over 40 yr), due to multiple years of perennial alfalfa. No-till increased sequestration in the simulated dairy forage rotation and prevented a net loss of C in corn-soybean rotations. Simulations indicated limited impact of cover crops and manure on long-term SOC sequestration. The low solids content of liquid dairy manure is the likely reason for the less-than-expected impact of manure. Overall, simulations suggest that inclusion of alfalfa provides the greatest potential for SOC sequestration with a typical Pennsylvania crop rotation.

Mine-soil treatment using stabilized manure rapidly sequesters large quantities of organic carbon and nutrients. However, the nutrient-rich soil conditions may become highly conducive for production and emission of N2O. We examined this possibility in a Pennsylvania coal mine restored using poultry manure stabilized in two forms: composted (Comp) or mixed with paper mill sludge (Man + PMS) at C/N ratios of 14, 21, and 28 and compared those with the emissions from conventionally treated soil. The mine soil was extremely well drained with 59% coarse fragments. Soil–atmosphere exchange of N2O and CO2 was determined using a sampling campaign of ten measurements between 16 June and 14 September 2009 (90 days) and 13 measurements between 28 June and 9 November 2010 (134 days) using static vented chambers at ambient and increased moisture (water added) content. Potential denitrification was determined in a laboratory incubation experiment. While non-amended mine soil did not have a measurable potential for denitrifying activity, the manure-based amendments introduced the potential. Soil water filled pore space was less than 60% on most sampling days in both ambient and water-added plots. Daily N2O-N emissions ranged between 40 and 70 g N ha−1 with cumulative emissions of 2–4 kg N ha−1 from non-amended, lime and fertilizer (L + F) and Comp, and 3–10 kg N ha−1 from Man + PMS treatments. The maximum emission obtained from Man + PMS represented

Temperate pastures in the Northeast USA are highly productive and could act as significant sinks for soil organic carbon (SOC). However, soils under mature pastures are often considered to have reached equilibrium such that no further sequestration of SOC is expected. This study quantified changes in pasture SOC over nine years using micrometeorological (eddy covariance) measurements of net changes in ecosystem C and direct measurements of changes in SOC (soil cores). Eddy covariance estimates of C flux were made both with and without corrections for sensor self-heating. Change in SOC as measured by the soil core method was non-significant for the Low-N pasture (19 ± 105 g C m −2 yr −1 , P = 0.89). However, a significant loss of −504 ± 91 g C m −2 yr −1 ( P = 0.01) occurred for the High-N pasture with the amount lost increasing with depth in the soil profile. Eddy covariance measurements without the self-heating correction differed only slightly between pastures with a net flux of −9 and −20 g C m −2 yr −1 for the Low- and High-N pastures, respectively. Applying the sensor self-heating correction to the eddy covariance data increased the estimated loss of ecosystem C by 94 g m −2 yr −1 for the Low-N and 102 g m −2 yr −1 for the High-N pasture. Both soil cores and eddy covariance suggest that the Low-N pasture was C neutral over the nine years of the study. A large amount of C was lost from deep in the soil profile from the High-N pasture which could not be explained by fluxes measured with the eddy covariance system. Comparison of eddy covariance and soil core data was not useful for determining the appropriateness of using the sensor self-heating correction at this location.

Mine-land reclamation for biomass production is often achieved by means of large applications of N and organic C with amendments that could create soil conditions favorable for N2O production and emissions. To investigate this possibility, we conducted a laboratory experiment using mine soil collected from an active surface coal mine site near Philipsburg, Pennsylvania. During a 37-d incubation period, we measured N2O and CO2 fluxes from non-amended soil and from soil amended with ammonium nitrate (L + F), composted poultry manure (Comp), poultry manure alone (Man) and mixed with 3 rates of paper mill sludge (PMS) to obtain carbon to nitrogen ratios of 14, 20 and 27 (Man + PMS14, 20 and 27), each at 60% and 80% water filled pore space (WFPS). Results showed that manure alone leads to a greater emission of N2O under laboratory conditions than with L + F. However, composting manure effectively reduced the emissions compared to that of L + F despite a large addition of organic C and N. Composted manure-treated soil emitted less than all other manure-based treatments at both 60% and 80% WFPS. The emissions were greater from soil amended with the Man + PMS treatments compared to non-amended and L + F-amended soil, and it increased during periods of intense microbial activity created by the application of manure and PMS. Higher water content increased emissions particularly during periods of intense microbial activity coupled with inorganic N availability. Cumulative N2O emissions from manure-treated soils represented less than 0·1% loss of total applied N. Copyright © 2014 John Wiley & Sons, Ltd.

A 4-unit dual-flow continuous-culture fermentor system was used to assess the effect of supplementing 7-d sprouted barley (SB) or barley grain (BG) with an herbage-based or haylage-based diet on nutrient digestibility, volatile fatty acid (VFA) profiles, bacterial protein synthesis, and methane (CH 4 ) output. Treatments were randomly assigned to fermentors in a 4×4 Latin square design with a 2×2 factorial arrangement using 7 d for diet adaptation and 3 d for sample collection. Experimental diets were (1) 55.5g of herbage dry matter (DM) + 4.5g of SB DM, (2) 56.0g of herbage DM + 4.0g of BG DM, (3) 55.5g of haylage DM + 4.5g of SB DM, and (4) 56.0g of haylage DM + 4.0g of BG DM. Forages were fed at 0730, 1030, 1400, and 1900h, whereas SB and BG were fed at 0730 and 1400h. Gas samples for CH 4 analysis were collected at 0725, 0900, 1000, 1355, 1530, and 1630h on d 8, 9, and 10. Fluid samples were taken once daily on d 8, 9, and 10 for pH measurements and for ammonia-N and VFA analysis and analyzed for DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber for determination of nutrient digestibilities and estimation of bacterial protein synthesis. Orthogonal contrasts were used to compare the effect of forage source (haylage vs. herbage), supplement (BG vs. SB), and the forage × supplement interaction. Apparent and true DM and organic matter digestibilities as well as apparent crude protein digestibility were not affected by forage source. However, true DM digestibility was greatest for diets supplemented with SB. Apparent neutral and acid detergent fiber digestibilities of herbage-based diets were higher than haylage-based diets but fiber digestibility was not affected by supplement. Diets supplemented with SB had higher mean and minimum pH than BG; however, maximum pH was not affected by diet. Supplementation with BG produced a greater concentration of total VFA compared with diets supplemented with SB. Haylage-based diets produced greater CH 4 output compared with herbage-based diets but supplementation did not affect CH 4 output. Efficiency of bacterial protein synthesis was greater for herbage-based diets compared with haylage-based diets, with no effect of supplementation. Overall, supplementation with SB marginally increased true DM digestibility of herbage- and haylage-based diets but did not affect fiber and crude protein digestibilities, CH 4 output, and bacterial efficiency, compared with BG.

Because of climate change, insufficient soil moisture may increasingly limit crop productivity in certain regions of the world. This may be particularly consequential for biofuel crops, many of which will likely be grown in drought-prone soils to avoid competition with food crops. Biochar is the byproduct of a biofuel production method called pyrolysis. If pyrolysis becomes more common as some scientists predict, biochar will become more widely available. We asked, therefore, whether the addition of biochar to soils could significantly increase the availability of water to a crop. Biochar made from switchgrass (Panicum virgatum L.) shoots was added at the rate of 1% of dry weight to four soils of varying texture, and available water contents were calculated as the difference between field capacity and permanent wilting point water contents. Biochar addition significantly increased the available water contents of the soils by both increasing the amount of water held at field capacity and allowing plants to draw the soil to a lower water content before wilting. Among the four soils tested, biochar amendment resulted in an additional 0.8–2.7 d of transpiration, which could increase productivity in drought-prone regions or reduce the frequency of irrigation. Biochar amendment of soils may thus be a viable means of mitigating some of the predicted decrease in water availability accompanying climate change that could limit the future productivity of biofuel crops.

The use of enhanced efficiency N fertilizers can increase crop N utilization and lead to lower emissions of the greenhouse gas N₂O. To determine the potential benefit of four enhanced efficiency fertilizers with rainfed corn (Zea mays L.) production in central Pennsylvania, N₂O emissions and grain yield were monitored during a 4-yr field study and compared with untreated urea prills and urea–NH₄NO₃ (UAN). The tested enhanced efficiency products were ESN (polymer-coated urea), SuperU (urease and nitrification inhibitor treated urea), UAN treated with AgrotainPlus (urease and nitrification inhibitors), and PiNT (cation-stabilized amine-N). Additionally, 28-d laboratory incubations were conducted to verify the potential differences in N cycling rates among N sources. The laboratory incubations indicated that ESN, SuperU, and treated UAN all had the potential to delay accumulation of NO₃ relative to untreated urea and UAN, but N cycling was similar with PiNT and the untreated fertilizers. Extended dry periods limited the denitrification potential and overall N₂O emissions in the field, but spikes of N₂O emission were seen within 1 mo after fertilizer application in each year. However, variation in emission rates was high within treatments, and no consistent differences among N sources were seen. Cumulative growing season N₂O emissions and grain yield were similar for all N sources in each year of the study. Enhanced efficiency fertilizers do not appear to be an effective means to reduce N₂O emission in a rainfed system, at least when rainfall is inconsistent.

Amending soils with biochar can sequester C and improve soil properties, such as nutrient holding capacity and water retention. While biochars generally have a long residence time in soil, the turnover of biochar C can be influenced by both biochar characteristics and soil properties. Biochar can also potentially alter the rate of decomposition of native soil organic matter (SOM). The turnover of switchgrass (Panicum virgatum L.)-derived biochar C was evaluated in the laboratory using soil from four marginally productive sites in central Pennsylvania. Carbon dioxide emissions from unamended soil, biochar-amended soil, and pure biochar were monitored during 189-d incubations, and data were fit to a two-pool exponential model to estimate the amount and mean residence time (MRT) of C in labile and stable pools. Carbon-13 signatures of emitted CO₂ were also determined to estimate the proportion of emitted CO₂ derived from the biochar. Mixing biochar with each of the soils reduced the apparent MRT of C in both labile and stable pools, but the magnitude of change depended on the soil. Overall, the biochar was largely stable in each soil, with only 1.1 to 2.1% of the added biochar C emitted during incubation. There was no measurable effect of biochar amendment on the turnover of native SOM in any of the soils. Therefore, we conclude that amendment of our soils with switchgrass-derived biochar can effectively increase net C sequestration.

This lysimeter experiment was designed to investigate the effects of dietary crude protein (CP) concentration on nitrate-N (NO-N) and ammonia (NH) losses from dairy manure applied to soil and manure N used for plant growth. Lactating dairy cows were fed diets with 16.7% CP (HighCP) or 14.8% CP (LowCP) content. Feces and urine were labeled with N by ruminal pulse-doses of NHCl. Unlabeled and N-labeled feces and urine were used to produce manure for a study with 21 lysimeters in a greenhouse. Manure application rate was 277 kg N ha. Ammonia emissions were measured at 3, 8, 23, 28, 54, and 100 h after manure application. Manure was incorporated into the soil, and a leaching event was simulated. Spring barley was planted (387 plants per m) 7 d after the leaching event and harvested at senescence. Ammonia emission rates and the contribution of urinary N to NO-N were on average about 100% greater for HighCP vs. LowCP manures. With both LowCP and HighCP manures, a greater proportion of urinary vs. fecal N was recovered in leachate NO-N. There was no difference in whole-crop barley N yields between LowCP and HighCP manures, but barley kernel N yield tended to be greater ( = 0.09) for lysimeters treated with HighCP manures. Using a unique labeling approach, this lysimeter experiment demonstrated that when applied at equal soil N application rates, manure from cows fed the HighCP diet resulted in markedly greater NH emissions and urinary N losses with leachate NO-N than manure from cows fed the LowCP diet.

The incorporation of swine manure with tillage effectively reduces ammonia (NH3) emissions and conserves crop available nitrogen (N) but is not compatible with no-till and many other conservation tillage programs. Rolling-tine aerators potentially provide a means to enhance manure infiltration with limited disruption of the soil surface; however, the impact of the range of aerator configurations and manure placements has not been widely studied. We measured NH3 emissions, conducted presidedress nitrate (NO3) tests (PSNT), monitored corn (Zea mays L.) grain yield when swine manure was incorporated with combinations of two aerator toolbar offset angles (0° and 10°) and two manure placements (broadcast before aeration and banded behind aerator), and compared those measurements to unincorporated surface application and an unmanured control. Additional plots were established with five rates of mineral N fertilization to determine N response curve and estimate fertilizer N equivalent of the applied manure. Measurement of cumulative NH3 emissions using a dynamic chamber method showed that offsetting the aerator toolbar by 10° reduced emissions by 65% to 75%, with both manure placements, compared to surface application. However, no consistent reductions in NH3 emissions were observed when the toolbar was not offset. While reduction in NH3 with the offset toolbar could conserve substantial amounts of plant available N, the soil disturbance caused by the offset tines would not be compatible with most conservation tillage programs. Presidedress NO3 test values increased when NH3 emissions were reduced. In 2009, both the angled and straight aerator treatments with manure banded behind the aerator resulted in significantly higher corn grain yield than all other treatments despite reductions in NH3 emissions only when the toolbar was angled. Correlation of yield from manure application treatments with the N response curve for multiple mineral N application rates showed a greater than expected response to manure application. Yield responses are an indication that aeration has benefits in addition to N conservation. We do not recommend the rolling-tine aerator if reducing NH3 emissions in conservation tillage is the primary goal, but future study into other yield-increasing benefits of aeration is needed.

The efficient use of water and nitrogen represents a primary concern to agricultural production in Northwest China. A 2-year field experiment was conducted to assess the separation of nitrogen (N) fertilizer and irrigation water with alternating furrow irrigation (SNWAFI) in a maize (Zea mays L.) production system. Irrigation water use efficiency and nitrogen use efficiency with SNWAFI were generally greater than with conventional irrigation and fertilization (CIF). Response surfaces indicated that maximum maize yields were obtained with 238 kg urea-N ha−1 and 106 mm irrigation water in 2008 and 244 kg urea-N ha−1 and 95 mm of irrigation water in 2009. When the predicted yields were highest (6,384 and 6,549 kg ha−1), water use efficiency, N uptake, and N use efficiency were greater with SNWAFI than CIF. Conversely, soil NO3–N change during maize growing season decreased with SNWAFI compared CIF. With SNWAFI, optimizing irrigation water and N fertilizer rates can maximize yield, save irrigation water, and reduce N leaching.

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.

Injection of cattle and swine slurries can provide soil incorporation in no-till and perennial forage production. Injection is expected to substantially reduce N loss due to ammonia (NH3) volatilization, but a portion of that N conservation may be offset by greater denitrification and leaching losses. This paper reviews our current knowledge of the impacts of subsurface application of cattle and swine slurries on the N balance and outlines areas where a greater understanding is needed. Several publications have shown that liquid manure injection using disk openers, chisels, or tines can be expected to Sreduce NH, emissions by at least 40%, and often by 90% or more, relative to broadcast application. However, the limited number of studies that have also measured denitrification losses have shown that increased denitrification with subsurface application can offset as much as half of the N conserved by reducing NH3 emissions. Because the greenhouse gas nitrous oxide (N2O) is one product of denitrification, the possible increases in N2O emission with injection require further consideration. Subsurface manure application generally does not appear to increase leaching potential when manure is applied at recommended rates. Plant utilization of conserved N was shown in only a portion of the published studies, indicating that further work is needed to better synchronize manure N availability and crop uptake. At this time in the United States, the economic and environmental benefits from reducing losses of N as NH3 are expected to outweigh potential liability from increases in denitrification with subsurface manure application. To fully evaluate the trade-offs among manure application methods, a detailed environmental and agricultural economic assessment is needed to estimate the true costs of potential increases in NO2O emissions with manure injection.

Managing manure in reduced tillage and forage systems presents challenges, as incorporation by tillage is not compatible. Surface-applied manure that is not quickly incorporated into soil provides inefficient delivery of manure nutrients to crops due to environmental losses through ammonia (NH3) volatilization and nutrient losses in runoff, and serves as a major source of nuisance odors. An array of technologies now exist to facilitate the incorporation of liquid manures into soil with restricted or minor soil disturbance, some of which are new: shallow disk injection; chisel injection; aeration infiltration; pressure injection. Surface banding of manure inforages decreases NH3 emissions relative to surface broadcasting, as the canopy can decrease wind speed over the manure, but greater reductions can be achieved with manure injection. Soilaeration is intended to hasten manure infiltration, but its benefits are not consistent and may be related to factors such as soildrainage characteristics. Work remains to be done on refining its method of use and timing relative to manure application, which may improve its effectiveness. Placing manure under the soil surface efficiency by injection offers much promise to improve N use efficiency through less NH3 volatilization, reduced odors and decreased nutrient losses in runoff, relative to surface application. We identified significant gaps in our knowledge as manyof these technologies are relatively new, and this should help target future research efforts including environmental, agronomic, and economic assessments.

Chicory (Cichorium intybus L.) has the potential to provide abundant, high quality forage during periods of drought, but poor persistence limits its usefulness in permanent pasture. This experiment compared the effectiveness of three seeding methods to reestablish chicory into a grazed multi-species pasture where it had previously provided a major proportion of total forage yield. Seedling methods included: frost-seeding in February; no-till seeding in late March; and broadcast seeding followed by hoof incorporation of the seed in May. The three methods did not differ from each other, and all resulted in adequate seedling emergence. However, survival was poor with mortality rates of 77 to 84% by early October of the seeding year. It is likely that greater seeding rates and more vigorous suppression of existing vegetation will be necessary to successfully reestablish chicory into existing cool-season pastures.

Incorporating managed rotational grazing into a dairy farm can result in an array of environmental consequences. A comprehensive assessment of the environmental impacts of four management scenarios was conducted by simulating a 250-acre dairy farm typical of Pennsylvania with: (i) a confinement fed herd producing 22,000 lbs of milk per cow per year; (ii) a confinement fed herd producing 18,500 lbs; (iii) a confinement fed herd with summer grazing producing 18,500 lbs; and (iv) a seasonal herd maintained outdoors producing 13,000 lbs. Converting 75 acres of cropland to perennial grassland reduced erosion 24% and sediment-bound and soluble P runoff by 23 and 11%, respectively. Conversion to all perennial grassland reduced erosion 87% with sediment-bound and soluble P losses reduced 80 and 23%. Ammonia volatilization was reduced about 30% through grazing, but nitrate leaching loss increased up to 65%. Grazing systems reduced the net greenhouse gas emission by 8 to 14% and the C footprint by 9 to 20%. Including C sequestration further reduced the C footprint of an all grassland farm up to 80% during the transition from cropland. The environmental benefits of grass-based dairy production should be used to encourage greater adoption of managed rotational grazing in regions where this technology is well adapted.

Loss of soil nutrients in runoff accelerates eutrophication of surface waters. This study evaluated P and N in surface runoff in relation to rainfall intensity and hydrology for two soils along a single hillslope. Experiments were initiated on 1- by 2-m plots at foot-slope (6%) and mid-slope (30%) positions within an alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.) field. Rain simulations (2.9 and 7.0 cm h(-1)) were conducted under wet (spring) and dry (late-summer) conditions. Elevated, antecedent soil moisture at the foot-slope during the spring resulted in less rain required to generate runoff and greater runoff volumes, compared with runoff from the well-drained mid-slope in spring and at both landscape positions in late summer. Phosphorus in runoff was primarily in dissolved reactive form (DRP averaged 71% of total P), with DRP concentrations from the two soils corresponding with soil test P levels. Nitrogen in runoff was mainly nitrate (NO3-N averaged 77% of total N). Site hydrology, not chemistry, was primarily responsible for variations in mass N and P losses with landscape position. Larger runoff volumes from the foot-slope produced higher losses of total P (0.08 kg ha(-1)) and N (1.35 kg ha(-1)) than did runoff from the mid-slope (0.05 total P kg ha(-1); 0.48 kg N ha(-1)), particularly under wet, spring-time conditions. Nutrient losses were significantly greater under the high intensity rainfall due to larger runoff volumes. Results affirm the critical source area concept for both N and P: both nutrient availability and hydrology in combination control nutrient loss.

Increasing plant species diversity could enhance forage yield, resistance to weed invasion, and soil C accumulation in grazed pastures. Threeforagemixtures(2,3,or11species)wereestablishedonafarmin eastern Pennsylvania and grazed by dairy heifers or managed under a three-cuthaysystemfrom1999to2002.Netcanopyphotosynthesiswas measured from early April to early October 2000 to 2002. Root distribution to a depth of 60 cm was measured in mid-September each year, and soil C and N concentrations to a 15-cm depth were determined in May 1999 and September 2002. The 11-species mixture yielded43%moreforagedrymatterthanthe two-speciesmixture.This difference was mainly due to the inclusion of a few highly productive forage species in the 11-species mixture. Canopy photosynthesis did not differ among mixtures in the spring, but in the summer was 50% greater in the 3- and 11-species mixtures than the two-species mixture. The 11-species mixture also had 30 to 62% greater root biomass than the other two mixtures and a greater proportion of roots in deeper soil layers. Soil C either remained unchanged or decreased, depending on species composition, with the greatest decrease occurring in the 11species mixture. No relationship existed between changes in soil C concentration and either canopy photosynthesis or above- and belowground productivity. Deeper rooting could reduce drought stress by increasing access to deep soil moisture. Selecting forage mixtures to include specific desirable traits, such as greater rooting depth, could result in improved pasture performance.

The availability of N limits productivity in tallgrass prairie. Spring burning is common because it results in greater plant productivity despite reducing net N mineralization. To better explain how burning affects inorganic N availability in tallgrass prairie, the partitioning of 15N among plant and soil pools was measured in June and August 1994. Approximately 2.5 microgram N g(-1) soil was injected as either NH4 or NO3 to a depth of 15 cm within cores in burned and unburned prairie. Cores were removed from the field 6 d after injection, and 15N recovery in plant and soil N pools was determined. No more than 14% of the applied 15N remained in inorganic form 6 d after application. The largest portion of the applied 15N (35-80%) was recovered in the soil organic nitrogen pool (N(o)). Burning significantly increased the immobilization of both NH4 and NO3 within N(o), and microbial biomass accounted for greater than or equal to 50% of the 15N recovered in N(o). Accumulation of 15N in plants accounted for less than or equal to 35% of the applied 15N with a majority recovered from roots. Burning had little effect on 15N recovery in plants; however, 15N accumulations in roots were significantly greater when NO3 was used. Results indicate that immobilization within soil organic matter (SOM) controls the availability of both NH4 and NO3 to plants. Increased immobilization in soils with burning probably results largely from increased microbial N demand resulting from greater litter inputs with wider C to N ratios. Further research is needed to determine if abiotic mechanisms for N immobilization also significantly influence N availability in prairie soils.

Soils with excessive phosphorus (P) levels due to manure application are an environmental concern because water extractable P (WEP) in runoff from these soils can contribute to increased amounts P in surface water, which can contribute to eutrophication of freshwater. Phosphorus based manure management is an option to reduce WEP and thereby reduce agricultural P runoff. In P based manure management, manure is applied to meet the P needs of a crop or not to exceed a given soil test level. Because P base manure management does not supply enough nitrogen (N) to meet the needs of the crop, addition fertilizer N needs to be applied. Fertilizer N applied to soils may increase the rate of mineralization of organic matter and lowers soil pH and therefore may affect the solubility of soil inorganic and organic P pools. The extent to which this may affect WEP or plant P availability is not known. Thus, laboratory and greenhouse studies were conducted to determine the effects of P based manure management on WEP and ...

Microbial biomass and enzyme activities are affected by management practices and can be used as sensitive indicators of ecological stability. Microbial biomass C (MBC), microbial biomass N (MBN) and eight enzyme activities involved in the cycling of C, N, P and S were studied in the surface (0–5 cm) of an Irwin silty clay loam soil (fine, mixed, mesic, Pachic Arguistoll) in a tallgrass prairie ecosystem. Treatments of annual spring burning and N fertilization were initiated in 1986 and encompassed: (1) unburned–unfertilized, (2) burned–unfertilized, (3) burned–fertilized, and (4) unburned–fertilized. Activities of dehydrogenase, β-glucosidase, urease, deaminase, denitrifying enzyme, acid phosphatase, alkaline phosphatase, and arylsulfatase were assayed. Long-term burning and N fertilization of the tallgrass prairie soil reduced MBC and MBN relative to the unburned–unfertilized treatment. The effects of burning and N fertilization varied among the enzymes and the time of sampling. Long-term burning significantly (P

Although livestock production accounts for a sizeable share of global greenhouse gas emissions, numerous technical options have been identified to mitigate these emissions. In this review, a subset of these options, which have proven to be effective, are discussed. These include measures to reduce CH4 emissions from enteric fermentation by ruminants, the largest single emission source from the global livestock sector, and for reducing CH4 and N2O emissions from manure. A unique feature of this review is the high level of attention given to interactions between mitigation options and productivity. Among the feed supplement options for lowering enteric emissions, dietary lipids, nitrates and ionophores are identified as the most effective. Forage quality, feed processing and precision feeding have the best prospects among the various available feed and feed management measures. With regard to manure, dietary measures that reduce the amount of N excreted (e.g. better matching of dietary protein to animal needs), shift N excretion from urine to faeces (e.g. tannin inclusion at low levels) and reduce the amount of fermentable organic matter excreted are recommended. Among the many 'end-of-pipe' measures available for manure management, approaches that capture and/or process CH4 emissions during storage (e.g. anaerobic digestion, biofiltration, composting), as well as subsurface injection of manure, are among the most encouraging options flagged in this section of the review. The importance of a multiple gas perspective is critical when assessing mitigation potentials, because most of the options reviewed show strong interactions among sources of greenhouse gas (GHG) emissions. The paper reviews current knowledge on potential pollution swapping, whereby the reduction of one GHG or emission source leads to unintended increases in another.

Research from the eastern U.S. indicates that no-till crop production (NT) will typically lead to the sequestration of ~0.5 Mg soil organic C (SOC) ha − 1 yr − 1 for several years after adoption, largely due to a high potential for SOC sequestration near the soil surface. However, the impact of conservation tillage deeper in the soil profile is less clear. Careful consideration of both sampling depth and adequate sample numbers, especially when accessing multiple soil series, is needed in future research to conclusively determine effects that practices have below the upper few cm of soil. While conservation tillage, cover crops, and manure application are generally expected to increase SOC, data are needed for a broader range of practices and soils within the region. Even in cases where no net increase in SOC is achieved, conservation practices are highly valuable for erosion control, enhanced nutrient cycling, and improved water and air quality.

Two experiments were conducted to investigate the effect of dietary crude protein concentration on ammonia (NH(3)) and greenhouse gas (GHG; nitrous oxide, methane, and carbon dioxide) emissions from fresh dairy cow manure incubated in a controlled environment (experiment 1) and from manure-amended soil (experiment 2). Manure was prepared from feces and urine collected from lactating Holstein cows fed diets with 16.7% (DM basis; HCP) or 14.8% CP (LCP). High-CP manure had higher N content and proportion of NH(3)- and urea-N in total manure N than LCP manure (DM basis: 4.4 vs. 2.8% and 51.4 vs. 30.5%, respectively). In experiment 1, NH(3) emitting potential (EP) was greater for HCP compared with LCP manure (9.20 vs. 4.88 mg/m(2) per min, respectively). The 122-h cumulative NH(3) emission tended to be decreased 47% (P=0.09) using LCP compared with HCP manure. The EP and cumulative emissions of GHG were not different between HCP and LCP manure. In experiment 2, urine and feces from cows fed LCP or HCP diets were mixed and immediately applied to lysimeters (61×61×61 cm; Hagerstown silt loam; fine, mixed, mesic Typic Hapludalf) at 277 kg of N/ha application rate. The average NH(3) EP (1.53 vs. 1.03 mg/m(2) per min, respectively) and the area under the EP curve were greater for lysimeters amended with HCP than with LCP manure. The largest difference in the NH(3) EP occurred approximately 24 h after manure application (approximately 3.5 times greater for HCP than LCP manure). The 100-h cumulative NH(3) emission was 98% greater for HCP compared with LCP manure (7,415 vs. 3,745 mg/m(2), respectively). The EP of methane was increased and that of carbon dioxide tended to be increased by LCP compared with HCP manure. The cumulative methane emission was not different between treatments, whereas the cumulative carbon dioxide emission was increased with manure from the LCP diet. Nitrous oxide emissions were low in this experiment and did not differ between treatments. In the conditions of these experiments, fresh manure from dairy cows fed a LCP diet had substantially lower NH(3) EP, compared with manure from cows fed a HCP diet. The LCP manure increased soil methane EP due to a larger mass of manure added to meet plant N requirements compared with HCP manure. These results represent effects of dietary protein on NH(3) and GHG EP of manure in controlled laboratory conditions and do not account for environmental factors affecting gaseous emissions from manure on the farm.

Sustainable nutrient management requires redistribution of livestock manure from nutrient-excess areas to nutrient-deficit areas. Field experiments were conducted to assess agronomic (i.e., corn yield) and environmental (i.e., ammonia volatilization and surface nutrient loss) effects of different poultry litter application methods (surface vs. subsurface) and timings (fall vs. spring) in a potential manure-importing region in the Chesapeake Bay Watershed in the United States. All four litter treatments (205 kg nitrogen ha-1) produced grain yields (10.9–12.8 Mg ha-1) nearly equivalent to or higher than the 11.5 Mg ha-1 yield expected from the same mineral nitrogen rate. Compared with surface application, subsurface application significantly reduced ammonia emission (p < 0.0001), runoff volume (fall: p = 0.02; spring: p = 0.004), and loads of nitrate nitrogen (p < 0.0001; p = 0.003) and dissolved phosphorus (p < 0.0001; p = 0.004) soon after application. Integrating subsurface manure application technologies into the manure redistribution programs would help ensure that the surplus nutrients being relocated provide a maximum agronomic impact and minimum environmental impact to the importing region. J. Liu and D.B. Beegle, Dep. of Plant Science, Pennsylvania State Univ., University Park, PA 16802, USA; P.J.A. Kleinman, C.J. Dell, T.L. Veith, L.S. Saporito, and R.B. Bryant, Pasture Systems and Watershed Management Research Unit, USDA-ARS, University Park, PA 16802, USA; K. Han, State Key Laboratory of Crop Biology, Key Laboratory of Crop Water Physiology and Drought-tolerance Germplasm Improvement, College of Agronomic Sciences, Shandong Agricultural Univ., Tai’an, Shandong 271018, China; D.H. Pote, Dale Bumpers Small Farms Research Center, USDA-ARS, Booneville, AR 72927, USA. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. USDA is an equal opportunity provider and employer. Core Ideas • Manure redistribution adds fertility benefits to recipient fields. • Subsurface application of poultry litter has environmental benefits. • Redistribution plus subsurface application benefits both farmers and the environment. Published February 12, 2016

A dairy farm simulation model was used to compare the environmental and economic impacts of using alternative manure application methods on a dairy farm in Pennsylvania. Model predictions of ammonia emissions, nitrate leaching, and phosphorus runoff were compared to field measurements following no manure application and five application methods. Application methods included broadcast spreading without incorporation, broadcast spreading with immediate incorporation by tillage, band application with aeration, shallow disk injection, and high pressure injection. Following model evaluation, manure application methods were simulated over 25 years of weather on a representative Pennsylvania dairy farm. Immediate incorporation by tillage and the use of the two manure injection techniques reduced ammonia emissions, but nitrate leaching losses were increased. Reductions in ammonia N loss and runoff loss of P were obtained with the use of shallow disk injection without adversely affecting farm profitability.