P. A. Moore

Abstract Phosphorus in agricultural runoff can cause accelerated lake and stream eutrophication. Where producers have applied P at rates exceeding crop uptake, soil P has sometimes become the main source of P in runoff. We hypothesized that soil test P (STP) correlation to dissolved reactive P (DRP) and bioavailable P (BAP) in runoff varies, depending on the extraction method. To investigate which STP extraction method would be best for predicting DRP and BAP concentration and load in runoff, soil samples were taken from the 0‐ to 2‐cm depth of 54 grass plots (5% slopes) on Captina silt loam (fine‐silty, siliceous, mesic Typic Fragiudult). The STP was extracted by six methods and the ranges of results (mg kg −1 ) were: 54–490 (Mehlich III), 27–592 (Bray‐Kurtz P1), 25–169 (Olsen), 14–110 (distilled water), 23–170 (Fe oxide paper), and 105–1131 (acidified ammonium oxalate). The soil P saturation ranged from 16 to 80%. Simulated rain was applied at 100 mm h −1 and runoff was collected for 30 min. The concentration of DRP in total runoff ranged from 0.31 to 1.81 mg L −1 , and BAP from 0.37 to 2.18 mg L −1 . The r 2 values for STP by each extraction method correlated with runoff DRP and BAP, respectively, were: 0.72 and 0.72 (Mehlich III), 0.75 and 0.73 (Bray‐Kurtz P1), 0.72 and 0.72 (Olsen), 0.82 and 0.82 (distilled water), 0.82 and 0.82 (iron oxide paper), 0.85 and 0.82 (acidified ammonium oxalate), and 0.77 and 0.76 (P‐saturation). All correlations were significant ( P < 0.001), but the high r 2 values of those obtained from distilled water, iron oxide paper, and acidified ammonium oxalate extractants indicate better precision for predicting DRP and BAP concentrations in runoff. Correlations of STP with DRP load (range: 43.4 to 472.8 g ha −1 ) and BAP load (54.2 to 542.0 g ha −1 ) were not useful ( r 2 < 0.18), possibly because runoff volumes were highly variable.

Abstract Soils that contain high P levels can become a primary source of dissolved reactive P (DRP) in runoff, and thus contribute to accelerated eutrophication of surface waters. In a previous study on Captina soil, several soil test P (STP) methods gave results that were significantly correlated to DRP levels in runoff, but distilled H 2 O and NH 4 ‐oxalate methods gave the best correlations. Because results might differ on other soils, runoff studies were conducted on three additional Ultisols to identify the most consistent STP method for predicting runoff DRP levels, and determine effects of site hydrology on correlations between STP and runoff DRP concentrations. Surface soil (0–2 cm depth) of pasture plots was analyzed by Mehlich III, Olsen, Morgan, Bray‐Kurtz P1, NH 4 ‐oxalate, and distilled H 2 0 methods. Also, P saturation of each soil was determined by three different methods. Simulated rain (75 mm h −1 ) produced 30 min of runoff from each plot. All correlations of STP to runoff DRP were significant ( P < 0.01) regardless of soil series or STP method, with most STP methods giving high correlations ( r > 0.90) on all three soils. For given level of H 2 O‐extractable STP, low runoff volumes coincided with low DRP concentrations. Therefore, when each DRP concentration was divided by volume of plot runoff, correlations to H 2 O‐extractable STP had the same ( P < 0.05) regression line for every soil. This suggests the importance of site hydrology in determining P loss in runoff, and may provide a means of developing a single relationship for a range of soil series.

Abstract Aluminum sulfate [Al 2 (SO 4 ) 3 ·14H 2 O] applications to poultry litter can greatly reduce P concentrations in runoff from fields fertilized with poultry litter, as well as decrease NH 3 volatilization. The objective of this study was to evaluate metal runoff from plots fertilized with varying rates of alum‐treated and untreated (normal) poultry litter. Alum‐treated (10% alum by weight) and untreated litter was broadcast applied to small plots in tall fescue ( Festuca arundinacea Schreb.). Litter application rates were 0, 2.24, 4.49, 6.73, and 8.98 Mg ha −1 (0, 1, 2, 3, and 4 tons acre −1 ). Rainfall simulators were used to produce two runoff events, immediately after litter application and 7 d later. Both concentrations and loads of water‐soluble metals increased linearly with litter application rates, regardless of litter type. Alum treatment reduced concentrations of As, Cu, Fe, and Zn, relative to untreated litter, whereas it increased Ca and Mg. Copper concentrations in runoff water from untreated litter were extremely high (up to 1 mg Cu L −1 ), indicating a potential water quality problem. Soluble Al, K, and Na concentrations were not significantly affected by the type of litter. Reductions in trace metal runoff due to alum appeared to be related to the concentration of soluble organic C (SOC), as well as the affinity of SOC for trace metals. Metal runoff from alum‐treated litter is less likely to cause environmental problems than untreated litter, since threats to the aquatic environment by Ca and Mg are far less than those posed by As, Cu, and Zn.

As part of a systemic assessment toward social sustainability of egg production, we have reviewed current knowledge about the environmental impacts of egg production systems and identified topics requiring further research. Currently, we know that 1) high-rise cage houses generally have poorer air quality and emit more ammonia than manure belt (MB) cage houses; 2) manure removal frequency in MB houses greatly affects ammonia emissions; 3) emissions from manure storage are largely affected by storage conditions, including ventilation rate, manure moisture content, air temperature, and stacking profile; 4) more baseline data on air emissions from high-rise and MB houses are being collected in the United States to complement earlier measurements; 5) noncage houses generally have poorer air quality (ammonia and dust levels) than cage houses; 6) noncage houses tend to be colder during cold weather due to a lower stocking density than caged houses, leading to greater feed and fuel energy use; 7) hens in noncage houses are less efficient in resource (feed, energy, and land) utilization, leading to a greater carbon footprint; 8) excessive application of hen manure to cropland can lead to nutrient runoff to water bodies; 9) hen manure on open (free) range may be subject to runoff during rainfall, although quantitative data are lacking; 10) mitigation technologies exist to reduce generation and emission of noxious gases and dust; however, work is needed to evaluate their economic feasibility and optimize design; and 11) dietary modification shows promise for mitigating emissions. Further research is needed on 1) indoor air quality, barn emissions, thermal conditions, and energy use in alternative hen housing systems (1-story floor, aviary, and enriched cage systems), along with conventional housing systems under different production conditions; 2) environmental footprint for different US egg production systems through life cycle assessment; 3) practical means to mitigate air emissions from different production systems; 4) process-based models for predicting air emissions and their fate; and 5) the interactions between air quality, housing system, worker health, and animal health and welfare.

Abstract Total P is increasing over time in the waters of Lake Okeechobee, Florida, but the concentrations do not correlate with external loads. The objectives of this study were to determine: (i) the P flux from various sediment types within the lake, (ii) the factors that control direction and magnitude of P flux, and (iii) the amount of P associated with various inorganic P phases within the sediment. Phosphorus flux was measured from intact sediment cores taken from eight sites that represent major sediment types and major inflows of Lake Okeechobee at four time periods in 1989–1990. At the same location‐times, dissolved reactive phosphorus (DRP) in porewater was determined using porewater equilibrators and/or sediment cores. Results indicate that P flux from sediments is very sensitive to changes in O 2 status of the overlying water, with anaerobic conditions promoting large P fluxes. Despite steep porewater DRP gradients in sediments (varying from 0.1 mg P L −1 at the sediment/water interface to more than 1 mg P L −1 at lower depths), P flux was not regulated by such gradients. Such lack of dependence of P flux on DRP gradients highlights the role redox reactions (involving Fe) can play in P chemistry in the top few centimeters of the sediment. Internal P loads (i.e., flux from bottom sediments) were found to be approximately equivalent to external P loads (≈1 mg P m −2 d −1 ).