Lou S. Saporito

Managing manure for sustainable livestock production in the Chesapeake Bay Watershed

Manure presents one of the greatest challenges to livestock (dairy and beef cattle, swine, poultry, equine, sheep, llamas, etc.) operations in the Chesapeake Bay Watershed, serving both as resource and liability. The Chesapeake Bay is threatened by excessive nutrient loadings, and, according to the US Environmental Protection Agency (USEPA), manure is the source of 18% of the nitrogen and 27% of the phosphorus entering the Chesapeake Bay annually (figure 1) (Chesapeake Bay Program 2010). Developing economical, practical, and effective manure management options for livestock producers will not only contribute to the restoration of the Chesapeake Bay, but will also provide a model for other areas where water quality and livestock production objectives must be balanced. The 166,000 km2 (64,000 mi2) Chesapeake Bay Watershed is home to 3.2 million animal units (animal unit = 454 kg [1,000 lbs] of livestock) generating roughly 36 million t (40 million tn) of livestock manure per year. In comparison, the 14 million humans who call the Chesapeake Bay Watershed home generate 3.6 million t (4 million tn) of waste annually (Brosch 2010; Blankenship 2005). The livestock manure contains approximately 259,000 t (285,000 tn) of nitrogen and 70,000 t (77,000 tn) of phosphorus. Most manure is…

Phosphorus leaching from agricultural soils of the delmarva peninsula, USA.

Leaching of phosphorus (P) mobilizes edaphic and applied sources of P and is a primary pathway of concern in agricultural soils of the Delmarva Peninsula, which defines the eastern boundary of the eutrophic Chesapeake Bay. We evaluated P leaching before and after poultry litter application from intact soil columns (30 cm diameter × 50 cm depth) obtained from low- and high-P members of four dominant Delmarva Peninsula soils. Surface soil textures ranged from fine sand to silt loam, and Mehlich-3 soil P ranged from 64 to 628 mg kg. Irrigation of soil columns before litter application pointed to surface soil P controls on dissolved P in leachate (with soil P sorption saturation providing a stronger relationship than Mehlich-3 P); however, strong relationships between P in the subsoil (45-50 cm) and leachate P concentrations were also observed ( = 0.61-0.73). After poultry litter application (4.5 Mg ha), leachate P concentrations and loads increased significantly for the finest-textured soils, consistent with observations that well-structured soils have the greatest propensity to transmit applied P. Phosphorus derived from poultry litter appeared to contribute 41 and 76% of total P loss in leachate from the two soils with the finest textures. Results point to soil P, including P sorption saturation, as a sound metric of P loss potential in leachate when manure is not an acute source of P but highlight the need to factor in macropore transport potential to predict leaching losses from applied P sources.

Using rare earth elements to control phosphorus and track manure in runoff.

Concern over the enrichment of agricultural runoff with phosphorus (P) from land applied livestock manures has prompted the development of manure amendments that minimize P solubility. In this study, we amended poultry, dairy, and swine manures with two rare earth chlorides, lanthanum chloride (LaCl(3).7H(2)O) and ytterbium chloride (YbCl(3).6H(2)O), to evaluate their effects on P solubility in the manure following incubation in the laboratory as well as on the fate of P and rare earth elements (REEs) when manures were surface-applied to packed soil boxes and subjected to simulated rainfall. In terms of manure P solubility, La:water-extractable P (WEP) ratios close to 1:1 resulted in maximum WEP reduction of 95% in dairy manure and 98% in dry poultry litter. Results from the runoff study showed that REE applications to dry manures such as poultry litter were less effective in reducing dissolved reactive phosphorus (DRP) in runoff than in liquid manures and slurries, which was likely due to mixing limitations. The most effective reductions of DRP in runoff by REEs were observed in the alkaline pH soil, although reductions of DRP in runoff from the acidic soil were still >50%. Particulate REEs were strongly associated with particulate P in runoff, suggesting a potentially useful role in tracking the fate of P and other manure constituents from manure-amended soils. Finally, REEs that remained in soil following runoff had a tendency to precipitate WEP, especially in soils receiving manure amendments. The findings have valuable applications in water quality protection and the evaluation of P site assessment indices.

Phosphorus and nitrogen leaching before and after tillage and urea application.

Leaching of nutrients through agricultural soils is a priority water quality concern on the Atlantic Coastal Plain. This study evaluated the effect of tillage and urea application on leaching of phosphorus (P) and nitrogen (N) from soils of the Delmarva Peninsula that had previously been under no-till management. Intact soil columns (30 cm wide × 50 cm deep) were irrigated for 6 wk to establish a baseline of leaching response. After 2 wk of drying, a subset of soil columns was subjected to simulated tillage (0-20 cm) in an attempt to curtail leaching of surface nutrients, especially P. Urea (145 kg N ha) was then broadcast on all soils (tilled and untilled), and the columns were irrigated for another 8 wk. Comparison of leachate recoveries representing rapid and slow flows confirmed the potential to manipulate flow fractions with tillage, albeit with mixed results across soils. Leachate trends in the finer-textured soil suggest that tillage impeded macropore flow and forced greater matrix flow. Despite significant vertical stratification of soil P that suggested tillage could prevent leaching of P via macropores from the surface to the subsoil, tillage had no significant impact on P leaching losses. Relatively high levels of soil P below 20 cm may have served as the source of P enrichment in leachate waters. However, tillage did lower losses of applied urea in leachate from two of the three soils, partially confirming the studys premise that tillage would destroy macropore pathways transmitting surface constituents to the subsoil.

Evaluating the spatial and temporal dynamics of farm and field phosphorus and potassium balances on a mixed crop and livestock farm

Methods to track P and K on farms over time at varying spatial scales can improve farm agronomic and environmental performance monitoring. An annual nutrient balance was used to determine P and K balances at varying spatial scales on a 128 ha mixed crop and dairy farm in a central Pennsylvania limestone valley for each of nine years. Alfalfa (Medicago sativa L.) and corn (Zea mays L.) occupied 60% and 40% of the cropland, respectively. Inputs of P and K to the farm exceeded outputs over the study period. Net increases of P and a decrease in K were determined in the aggregate of all fields over the 9-yr period. The balance of P and K varied with time within a field, and by field within a year because nutrient inputs and removals varied with crop selection, management tactics, and year in the rotation. Recognizing that increases in field P are in proportion to P entering the farm can help reduce P accumulation in fields by addressing surpluses at their source or balancing managed flows for the farm. Conversely, decreases in field K associated with forage crops may be the reason for additional supplemental K inputs to the farm. Monitoring nutrient stocks (soil testing) and flows (input/output balances) at different scales in conjunction with spatial patterns of nutrient balances can be the foundation for integrating farm activities and information technologies in a new generation of performance enhancing tools.

Subsurface Application Enhances Benefits of Manure Redistribution

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

Assessing the Impact of Manure Application Method on Runoff Phosphorus using Controlled and Natural Rainfall

Due to widespread adoption of no-till, there is considerable interest in methods of incorporating manure into soil with minimal disturbance. Watershed and nutrient trading programs rely upon empirical water quality findings to promote manure application methods and to extrapolate the water quality benefits of those methods. Rainfall simulation studies have been a key source of input into the water quality benefits of manure management alternatives. Rainfall simulation studies offer a means of controlling key storm variables and selecting the timing of events, often with an eye to representing worst case scenarios. However, the control offered by these studies results in limited representation of management, climatic, and hydrologic variables. To better understand the effect of assessment method on management recommendations, we compared edge-of-field findings from controlled rainfall events with those obtained under natural conditions.

A Phosphorus Transport Study: Influence of Poultry Litter Application Method on Leaching

Phosphorus (P) transport to surface waters via subsurface pathways contributes to eutrophication. This study was conducted to compare the extent and mechanisms of vertical P translocation after application of poultry litter by broadcast, broadcast-then-disked, and subsurface incorporation methods to a Coastal Plain soil on the University of Maryland-Eastern Shore Research Farm near Princess Anne, MD. Treatment and unamended control replicates were collected in undisturbed soil blocks 61 by 61 by 61 cm and prepared for two rainfall simulation events that were separated by 11 semi-weekly soaking-type irrigation events. Then FD&C No. 2 blue food dye was applied to the soil surface and leached through the profile. The blocks were inverted and the soil was removed in 10-cm layers. Separate soil samples taken around the dye-stained surface of macropores and within the soil matrix were analyzed for P content. Calcium chloride-extractable P (CCEP) levels for the soil associated with macropores were significantly elevated over the soil matrix within treatment at the 30-cm depth for all manured treatments, but not for the control, confirming that macropores are a pathway for translocation of recently applied litter P. Among treatments, macropore CCEP levels at the 30 and 40-cm depths were greater for the broadcast treatment than for the other litter application treatments, whose methods involved soil disturbance. CCEP concentrations in the soil matrix at the 30-cm depth were significantly higher for the unamended control, suggesting that matrix flow P losses from these high-P content soils will continue after cessation of litter application.