Balancing the phosphorus budget of a swine farm: A case study

Trends in animal production have moved the industry toward large confined animal feeding operations (CAFOs). These CAFOs concentrate large amounts of manure-based nutrients in relatively small areas, which increases the risk of nutrient loss to the surrounding environment. In response to water quality concerns, P-based manure application regulations are becoming more common. Mr. Pritchard is the owner and operator of two 4500-head swine (Sus scrofa) farms located in an area of intensive animal production in North Carolina. He has noticed an increasing trend in the soil P concentrations in his manure application fields and realizes that he does not have enough land to apply his anaerobically treated liquid swine manure based on crop P uptake. Mr. Pritchard is now faced with the dilemma of what to do to slow down the P accumulation in his soil. This case constructs a P budget for Mr. Pritchard's farm to examine ways of balancing on-farm nutrients. Students are encouraged to explore solutions related to animal nutrition, crop production, water quality, soil chemistry, and manure management. Furthermore, students should evaluate the appropriate role of government and industry in assisting Mr. Pritchard to protect the environment while remaining a profitable swine producer

Assessment of Phosphorus Retention in Irrigation Laterals

Irrigation laterals transport irrigation return flow, including water, sediment, and dissolved nutrients, such as phosphorus (P), back to surface water bodies. Phosphorus transformations during transport can affect both P bioavailability and the best management practices selected to minimize P inputs to waters of the United States. The objective of this study was to determine P retention in three irrigation laterals. Soluble reactive P (SRP) concentrations in lateral waters were increased from 0.08 to 0.25 mg L -1 (0.08 to 0.25 ppm) by constantly injecting a phosphate (PO4) solution for 2.5 hours. Bromide (Br) was used as a conservative tracer to determine dilution effects. Water was sampled at 10-minute intervals, beginning 30 minutes prior to injection and 120 minutes following injection, at one upstream location and various downstream locations to approximately 1,550 m (~1 mi) from injection sites. When at steady state, SRP concentrations only decreased by 5% over the lengths studied, equating to P uptake lengths of over 18 km (11.2 mi), which was one to two orders of magnitude greater than natural streams; the linear SRP uptake rate was 0.011 mg L -1 km -1 (0.018 ppm mi -1 ). Longer P uptake lengths and lower uptake rates in irrigation laterals, as compared to natural streams, may be due to the elevated sediment equilibrium P concentration, greater water velocities, and removal of vegetation causing a reduction in frictional resistance. Reducing water velocities should optimize irrigation lateral conditions to reduce uptake length and maximize P uptake

Water balance for a predominantly surface irrigated district in southern Idaho

Water quantity and quality are being measured in an 82,000 ha irrigation district in southern Idaho to determine the effects of conservation practices, primarily conversion from furrow to sprinkler irrigation, for the Conservation Effects Assessment Project (CEAP). The percentage of sprinkler irrigated land has steadily increased from about 10% in 1990 to more than 30% in 2005. The objective of this study was to calculate a preliminary water and soluble salt balance for April through November, 2005. The water balance was calculated by subtracting measured outflow and estimated crop water use from measured inflow and precipitation. Precipitation was about 250% of normal in April and May, which delayed irrigation for many crops and probably increased the amount of return flow during these months. Water diverted for irrigation was 82% of the total water input to the irrigation district (inflow plus precipitation). Precipitation contributed 16% of the total input. Thirty-six percent of the diverted water left the irrigation district as surface return flow from April through November. This percentage will increase on an annual basis because return flow continues through the winter months after irrigation diversions have ceased. The irrigation district was a source of suspended sediment and a sink for soluble salts. April through November 2005 monitoring showed a net gain of 1620 kg ha-1 of soluble salts in the irrigation district, which could be a long-term concern if these salts accumulate in the root zone. Net sediment loss was 102 kg ha -1 , which is less than the 461 kg ha-1 measured during a similar study in 1971. These preliminary results indicate that converting to sprinkler irrigation, along with other conservation practices, has reduced sediment loss from this irrigation district. However, solid conclusions cannot be made until at least one year of monitoring is complete to adequately characterize annual trends, particularly the quantity and quality of non-irrigation season return flows

Field-scale evaluation of phosphorus leaching in acid sandy soils receiving swine waste

Accurate descriptions of P leaching are important because excess P applied to soils can enter surface water via leaching and subsurface transport, thereby negatively impacting water quality. The objectives of this study were to monitor P leaching in soils with a long-term history of waste application, relate soil solution P concentrations to soil P status, and quantify P leaching losses. Soil solution was monitored for 20 mo with samplers installed at 45-, 90-, and 135-cm depths in two pits (1 X 3 X L5 m) in Autryville (loamy, siliceous, thermic Arenic Paleudults) and Blanton (loamy, siliceous, semiactive, thermic Grossarenic Paleudults) soils located in a grazed pasture in Sampson County, NC, which had received swine waste for >20 yr. Maximum soil solution P concentrations at 45 cm exceeded 18 mg L' in both soils. Soil solution P concentrations at 90 cm in the Blanton soil were similar to that at 45 cm indicating low P sorption. Soil solution P concentrations at 90 cm in the Autryville soil averaged 0.05 mg L-' compared to 10 mg L' at 45 cm. A split-line model related soil solution P concentration to the degree of phosphorus saturation (DPS), identifying a change point at 45% DPS. Phosphorus movement past 45 cm equaled or exceeded surplus P additions for both soils. Longterm waste applications resulted in DPS > 90%, high soil solution P concentrations, and substantial vertical P movement. Phosphorus leaching should be considered when assessing long-term risk of P loss from waste-amended soils

Sprinkler and surface irrigation effects on return flow water quality and quantity

A major conservation practice in the Upper Snake-Rock (USR) watershed is the conversion from furrow irrigation to sprinkler irrigation. We compared the effect of irrigation system type on water quality and quantity at the watershed scale. Six small watersheds (150-700 ha) were identified with 5 to 70% of the cropland sprinkler irrigated and the remaining fields surface or furrow irrigated. Other agricultural land uses, cropping practices and soils were similar among watersheds. Water quality and quantity entering and exiting each watershed were measured with automated samplers during the irrigation season. Irrigation inflow to watersheds and outflow from watersheds did not decrease as sprinkler irrigated area increased. This probably results from the flow rate allocation system used on the Twin Falls irrigation tract. Annual sediment loss (r=-0.19, P=0.40) and concentration (r=-0.38, P=0.30) also did not correlate with the relative amount of sprinkler irrigated area. Annual sediment loss (r-0.87, P=0.03) and concentration (r-0.84, P=0.05) correlated with irrigation inflow—the more irrigation water delivered to a watershed the greater the outflow sediment concentration and loss. These preliminary results indicate that irrigation water delivery should be managed in addition to converting to sprinkler irrigation to improve water quality in this irrigated watershed

Conservation practice effectiveness in the irrigated Upper Snake/Rock Creek watershed

The Upper Snake River/Rock Creek Conservation Effects Assessment Project was initiated in 2005 to determine the effectiveness of conservation practices in an irrigated watershed. Our objectives were to determine water and salt balances and water quality effects of using sprinkler rather than furrow irrigation in the Twin Falls irrigation tract in southern Idaho. Data from the current study were compared with earlier studies conducted from 1968 to 1971. Irrigation water diverted from the Snake River supplied 73% and 83% of the hydrologic input to this 82,000 ha (202,000 ac) watershed in 2005 and 2006, respectively, with approximately 40% flowing back to the Snake River through furrow irrigation runoff, unused irrigation water, and subsurface drainage. Net suspended sediment loss decreased from 460 kg ha–1 (400 lb ac–1) during the 1971 irrigation season to 220 kg ha–1 (190 lb ac–1) in 2005 and 10 kg ha–1 (9 lb ac–1) in 2006 by switching from furrow to sprinkler irrigation, applying polyacylamide, and installing sediment ponds. The relative amount of sprinkler irrigation in a subwatershed did not correlate with the total loss of suspended sediment for July 2005 and 2006 (r = 0.12). The lack of correlation was primarily due to extremely high sediment concentrations in two of the five subwatersheds, possibly due to furrow irrigation management. Two potential concerns identified during this initial analysis were an accumulation of total salts in the watershed and increased nitrate concentrations in four return flow streams compared to earlier studies. Future analyses will determine the effects of specific practices with this watershed

The Promise, Practice, and State of Planning Tools to Assess Site Vulnerability to Runoff Phosphorus Loss

Publication history: Accepted - 23 October 2017; Published online - 1 November 2017.Over the past 20 yr, there has been a proliferation of phosphorus (P) site assessment tools for nutrient management planning, particularly in the United States. The 19 papers that make up this special section on P site assessment include decision support tools ranging from the P Index to fate-and-transport models to weather-forecast-based risk calculators. All require objective evaluation to ensure that they are effective in achieving intended benefits to protecting water quality. In the United States, efforts have been underway to compare, evaluate, and advance an array of P site assessment tools. Efforts to corroborate their performance using water quality monitoring data confirms previously documented discrepancies between different P site assessment tools but also highlights a surprisingly strong performance of many versions of the P Index as a predictor of water quality. At the same time, fate-and-transport models, often considered to be superior in their prediction of hydrology and water quality due to their complexity, reveal limitations when applied to site assessment. Indeed, one consistent theme from recent experience is the need to calibrate highly parameterized models. As P site assessment evolves, so too do routines representing important aspects of P cycling and transport. New classes of P site assessment tools are an opportunity to move P site assessment from general, strategic goals to web-based tools supporting daily, operational decision

Mapping and characterization of structural variation in 17,795 human genomes

A key goal of whole-genome sequencing for studies of human genetics is to interrogate all forms of variation, including single-nucleotide variants, small insertion or deletion (indel) variants and structural variants. However, tools and resources for the study of structural variants have lagged behind those for smaller variants. Here we used a scalable pipeline1 to map and characterize structural variants in 17,795 deeply sequenced human genomes. We publicly release site-frequency data to create the largest, to our knowledge, whole-genome-sequencing-based structural variant resource so far. On average, individuals carry 2.9 rare structural variants that alter coding regions; these variants affect the dosage or structure of 4.2 genes and account for 4.0–11.2% of rare high-impact coding alleles. Using a computational model, we estimate that structural variants account for 17.2% of rare alleles genome-wide, with predicted deleterious effects that are equivalent to loss-of-function coding alleles; approximately 90% of such structural variants are noncoding deletions (mean 19.1 per genome). We report 158,991 ultra-rare structural variants and show that 2% of individuals carry ultra-rare megabase-scale structural variants, nearly half of which are balanced or complex rearrangements. Finally, we infer the dosage sensitivity of genes and noncoding elements, and reveal trends that relate to element class and conservation. This work will help to guide the analysis and interpretation of structural variants in the era of whole-genome sequencing