Brad C. Joern

Phosphorus indices: why we need to take stock of how we are doing.

Many states have invested significant resources to identify components of their Phosphorus (P) Index that reliably estimate the relative risk of P loss and incentivize conservation management. However, differences in management recommendations and manure application guidelines for similar field conditions among state P Indices, coupled with minimal reductions in the extent of P-impaired surface waters and soil test P (STP) levels, led the U.S. Natural Resources Conservation Service (NRCS) to revise the 590 Nutrient Management Standard. In preparation for this revision, NRCS requested that a review of the scientific underpinnings and accuracy of current P Indices be undertaken. They also sought to standardize the interpretation and management implications of P Indices, including establishment of ratings above which P applications should be curtailed. Although some states have initiated STP thresholds above which no application of P is allowed, STP alone cannot define a sites risk of P loss. Phosphorus Indices are intended to account for all of the major factors leading to P loss. A rigorous evaluation of P Indices is needed to determine if they are directionally and magnitudinally correct. Although use of observed P loss data under various management scenarios is ideal, such data are spatially and temporally limited. Alternatively, the use of a locally validated water quality model that has been shown to provide accurate estimates of P loss may be the most expedient option to conduct Index assessments in the short time required by the newly revised 590 Standard.

Simulating soil phosphorus dynamics for a phosphorus loss quantification tool.

Pollution of fresh waters by agricultural phosphorus (P) is a water quality concern. Because soils can contribute significantly to P loss in runoff, it is important to assess how management affects soil P status over time, which is often done with models. Our objective was to describe and validate soil P dynamics in the Annual P Loss Estimator (APLE) model. APLE is a user-friendly spreadsheet model that simulates P loss in runoff and soil P dynamics over 10 yr for a given set of runoff, erosion, and management conditions. For soil P dynamics, APLE simulates two layers in the topsoil, each with three inorganic P pools and one organic P pool. It simulates P additions to soil from manure and fertilizer, distribution among pools, mixing between layers due to tillage and bioturbation, leaching between and out of layers, crop P removal, and loss by surface runoff and erosion. We used soil P data from 25 published studies to validate APLEs soil P processes. Our results show that APLE reliably simulated soil P dynamics for a wide range of soil properties, soil depths, P application sources and rates, durations, soil P contents, and management practices. We validated APLE specifically for situations where soil P was increasing from excessive P inputs, where soil P was decreasing due to greater outputs than inputs, and where soil P stratification occurred in no-till and pasture soils. Successful simulations demonstrate APLEs potential to be applied to major management scenarios related to soil P loss in runoff and erosion.

Potassium and nitrogen effects on carbohydrate and protein metabolism in alfalfa roots

Abstract An investigation was conducted to determine the effect of potassium (K) nutrition on alfalfa (Medicago sativa L.) growth and metabolism of root total nonstructural carbohydrates (TNC) and proteins, and to study whether nitrogen (N) fertilization overcomes N deficiency and low root protein concentrations caused by K deficiency. In Experiment 1, nodulated alfalfa plants were grown in plastic pots containing washed quartz sand and provided minus‐N Hoaglands solution containing 0, 0.6, or 6.0 mM K. Shoot and root K concentrations increased with increasing solution K. Root N concentrations were higher in plants receiving 6.0 mM K than in plants receiving 0.6 or 0 mM K, but shoot N concentrations were similar for all treatments. Plant persistence, shoots per plant, and shoot mass increased as solution K levels increased. Root starch concentration and utilization were positively associated with K nutrition. Total amylase activity was higher, but endoamylase activity was lower in roots of plants receivi...

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.

Transport and Fate of Phosphorus during and after Manure Spill Simulations

Animal manure spills contribute to P loading of surface waters and little is known about the effectiveness of the current manure spill clean-up methods to mitigate P contamination. Manure spill clean-up consists of containing, removing, and land applying the contaminated water column, while P-enriched fluvial sediments remain in place. Therefore, the objectives of this study were to (i) understand how P partitions between the water column and fluvial sediments during a manure spill, and (ii) evaluate the efficacy of current manure spill clean-up methods to remediate manure contaminated sediments. Manure spill simulations were conducted using fluvarium techniques and sediments collected from three drainage areas of two drainage ditches. Sediments with the greatest clay content (33%) resulted in a significantly greater P buffering capacity (10.3 L kg(-1)) and removed P from the water column at the greatest rate during the manure spill simulation relative to sediments with < 6% clay. Phosphorus uptake length for all sediments ranged from 574 to 815 m and the adsorption flux ranged from 8.9 to 16.7 mg m(-2) h(-1). After simulating the current manure spill remediation methods, P desorbed to the water from all sediments exceeded the Environmental Protection Agency total P criteria (0.076 mg L(-1)) for the region by at least 67%. Furthermore, results from this study suggest that the current manure spill remediation method needs refining to mitigate P from the total fluvial system water column and sediment following a spill.

Effects of phosphorus nutrition on carbohydrate and protein metabolism in alfalfa roots

Abstract Alfalfa (Medicago sativa L.) root reserves are thought to provide nutrients to regrowing shoots, enhance stress tolerance, and improve plant persistence. Factors affecting carbohydrate and protein accumulation and metabolism in roots are important in alfalfa production. Our objectives were to determine 1) the influence of phosphorus (P) nutrition on alfalfa shoot growth and root carbohydrate and protein metabolism after defoliation and 2) how quickly growth and root carbohydrate and protein metabolism of P‐deficient alfalfa plants responds to supplemental P. In Experiment 1, nodulated alfalfa was grown in quartz sand with minus‐nitrogen (N) Hoaglands solution containing 0,1,2, or 6 mM P. Root P concentrations increased with increasing solution P levels. Phytate P in roots of plants grown with 6 mM P was greater than that of plants grown in 0, 1, or 2 mM P. Shoot mass and shoots per plant were reduced by 67 and 43%, respectively, in plants grown with 0 mM P as compared to plants grown with 6 mM P...

EFFECTS OF MANURE AMENDMENTS ON ENVIRONMENTAL AND PRODUCTION PROBLEMS

A number of different problems are associated with animal manures. These include ammonia (NH3) emissions to the atmosphere, excessive non-point source phosphorus (P) runoff, exposure of humans and animals to pathogens, heavy metal contamination in surface runoff, nitrate (NO3) leaching to groundwater, odors, and nutrient imbalances for crop production. Although manure amendments cannot solve all of these problems, various amendments can be used effectively to control NH3 emissions, reduce P and heavy metal runoff, decrease pathogen levels in manure and help alleviate nutrient imbalances in manure. Manure amendments can also greatly improve solid separation in liquid manures. The only problem mentioned above where amendments have had little effect is on control of odor (Miner, 1997).

Manure Spills and Remediation Methods to Improve Water Quality

Within the last 2 decades the transition in livestock production technology and intensity has resulted in an increase in annual livestock production and a drastic decrease in the number of livestock operations. Consequently, the susceptibility of current livestock operations to experience manure spills is far greater relative to livestock farms 20 years ago, due to increased herd size per farm. Therefore, manure spills in agricultural communities have become a pervasive issue and have led to the catastrophic contributions of nutrients and pathogens to surface and groundwaters, human health issues, and large fish kills. Furthermore, the current remediation methods for manure spills that reach surface waters focus on mitigating contaminants in the water column and give no attention to the manure-exposed ditch sediments that remain in the fluvial system and continue to impair the water column. Therefore, this chapter addresses the causes, environmental impacts, and current and alternative remediation methods for manure spills in agricultural streams. Geographic data suggest that the location of animal-feeding operations and the occurrence of manure spills were highly correlated with the location of tile-drained agriculture fields. In addition, at least 14% of reported manure spills were separately attributed to the failure in waste storage equipment and over-application of manure in the states of Iowa and Ontario, Canada. Evaluations of the downstream impacts of manure spills have reported ammonia, total phosphorus, and total N concentrations that were at least 28 times the average upstream concentrations before the spill occurred. Studies have also determined that the current manure spill remediation method results in soluble phosphorus and nitrogen concentrations significantly greater than the Environmental Protection Agency total phosphorus nutrient critical limit, 24 h after the plume of the spill has passed. However, supplemental treatment of manure exposed sediments resulted in at least a 50% decrease in the soluble phosphorus concentrations which was in compliance with the phosphorus nutrient criteria.

Effects of Nitrogen and Phosphorus Application from Swine Manure on Winter Wheat Growth and Nutrient Utilization

Two trials were conducted to determine the effect of swine manure application on wheat growth and nutrient uptake. Manure was added to soil on a nitrogen (N) basis at 325 kg plant-available nitrogen (PAN) ha−1 (experiment 1) and on a phosphorus (P) basis at 50 kg P ha−1, while maintaining a rate of 325 kg PAN ha−1 through ammonium sulfate addition (experiment 2). Manure treatments increased overall wheat growth by 29% (P < 0.005) compared to the negative control (NC) and increased plant tissue N mass 48% (P < 0.001) and P mass 61% (P < 0.002) (experiment 1). Fertilizer control tended to increase (P < 0.10) wheat growth and increased total vegetative tissue N mass by 23% (P < 0.006) and potassium mass by 20% (P < 0.002) compared to manure treatments. Manure treatments increased wheat growth by 23% (P < 0.03) compared to the NC at the first harvest (experiment 2).

Initial biochar properties related to the removal of As, Se, Pb, Cd, Cu, Ni, and Zn from an acidic suspension

This study tests the influence of a diverse set of biochar properties on As(V), Se(IV), Cd(II), Cu(II), Ni(II), Pb(II), or Zn(II) removal from solution at pH 4.5. Six commercial biochars produced using different feedstock and pyrolysis conditions were extensively characterized using physical, chemical, and spectroscopic techniques, and their properties were correlated to anion and cation removal using multiple linear regression. H/total organic C (TOC) ratio and volatile matter were positively correlated to cation removal from solution, which indicate interactions between metals and non-aromatic C. Defining the correlation of ion removal with specific OC functional groups was hindered by the inherent limitations of the spectroscopic techniques, which was exacerbated by the heterogeneity of the biochars. Ash was negatively correlated to Se(IV) and positively correlated to Cd(II), Cu(II), and Ni(II) removal from solution. Interference from soluble P in biochars may partly explain the low Se(IV) removal from solution; and Ca-, P-, and Fe- containing compounds likely sorbed or precipitated Pb(II), Cd(II), Cu(II), Ni(II) and Zn(II). Furthermore, Ca-oxalate identified using X-ray diffraction in willow, may be responsible for willows increased ability to remove Cd(II), Ni(II), and Zn(II) compared to the other 5 biochars. It was clear that both OC and inorganic biochar components influenced metal(loid) and Se(IV) removal from solution. The non-aromatic and volatile OC correlated to removal from solution may be readily available for microbial degradation, while Mg, N, P, and S are required for biological growth. Biological metabolism and uptake of these compounds may inhibit or destabilize their interaction with contaminants.