The nature of phosphorus in calcareous soils

Calcareous soils (containing free lime) are common in many arid and semi-arid regions of North America and occur as inclusions in more humid regions. Phosphorus (P) is very reactive with lime. Following fertilizer application, P undergoes a series of reactions that gradually reduce its solubility. In most calcareous soils, there does not appear to be a strong agronomic advantage of any particular P source when managed properly. Organic matter can inhibit P fixation reactions to some extent. Some fertilizer recommendations call for additional P to be added when the soil contains high amounts of free lime

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

Sorption of organic phosphorus compounds in Atlantic Coastal Plain soils

Organic phosphorus (P) can comprise a significant amount of the total P in animal wastes, yet there is little information on the potential for organic P to be transferred from soils to watercourses. We examined the adsorption of organic P compounds to soils typical of the southeastern United States, i.e., Blanton Sand (loamy, siliceous, thermic, Grossarenic Paleudult), Cecil sandy clay loam (fine, kaolinitic, thermic, Typic Kanhapludult), and a Belhaven sandy loam (loamy, mixed, dysic, thermic, Terric Medisaprist). The behavior of four organic P compounds was studied: adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP), and inositol hexaphosphate (IHP); while KH2PO4 (ortho-P) was used as an inorganic reference. Laboratory studies were conducted to determine the effects of concentration (0-130 p.g P mL-1 ), pH (4.6-7.6), and soil properties on P adsorption. All the organic P compounds had greater adsorption than KH 2PO4 on the Blanton and Cecil soils at all concentrations and ranges of pH. In the Belhaven soil, IHP had the greatest sorption followed by KH 2PO4 and the nucleotides (ATP, ADP, and AMP, respectively). Adsorption of organic P was positively correlated with soil organic matter and Fe and Al contents. The greater sorption of some organic P compounds over that of ortho-P suggests that these compounds may pose less of a threat to water quality, although this preferential sorption may increase soluble P in situations where there is displacement of ortho-P by organic P added in manures

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

Dynamic protein methylation in chromatin biology

Post-translational modification of chromatin is emerging as an increasingly important regulator of chromosomal processes. In particular, histone lysine and arginine methylation play important roles in regulating transcription, maintaining genomic integrity, and contributing to epigenetic memory. Recently, the use of new approaches to analyse histone methylation, the generation of genetic model systems, and the ability to interrogate genome wide histone modification profiles has aided in defining how histone methylation contributes to these processes. Here we focus on the recent advances in our understanding of the histone methylation system and examine how dynamic histone methylation contributes to normal cellular function in mammals

The nature of phosphorus in calcareous soils

Calcareous soils (containing free lime) are common in many arid and semi-arid regions of North America and occur as inclusions in more humid regions. Phosphorus (P) is very reactive with lime. Following fertilizer application, P undergoes a series of reactions that gradually reduce its solubility. In most calcareous soils, there does not appear to be a strong agronomic advantage of any particular P source when managed properly. Organic matter can inhibit P fixation reactions to some extent. Some fertilizer recommendations call for additional P to be added when the soil contains high amounts of free lime

Phosphorus losses in runoff after application of litter from broilers fed high-available phosphorus corn feed

Recent efforts to reduce phosphorus (P) content of corn grain fed to poultry have led to the development of low-phytic-acid corn. Research is needed to evaluate the environmental impact of the application to cropland of manure from animals fed low-phytic-acid corn. The purpose of this research was to determine P losses in runoff from a bare Piedmont soil (cecil clay loam; clayey, kaolinitic, thermic, Typic Kanhapludult) in the southeastern United States receiving surface applications of broiler litter from birds fed a low-phytic-acid corn (HAP broiler litter). The HAP litter was applied at rates of 0, 8, 16, 33, 49, 66, and 82 kg P ha-1 . Simulated rainfall was applied at a rate of 7.6 cm hr-1 on the same day the litter sources were applied to the plots. Runoff volumes were measured, and samples were collected at 5-min intervals for 30 min and analyzed for reactive P (RP), algal-available P (AAP), and total P (TP). Flow-weighted concentrations and mass losses of P increased linearly with litter application rate (r2 values ¼ 0.99). Flow-weighted concentrations of RP in runoff increased from 2.2 to 15.4 mg RP L-1, and mass loss of TP in runoff ranged from 1.3 to 7.3 kg P ha-1 over all application rates based on linear regression. Runoff volume losses were 47% greater after litter applications compare to the 0 application rate treatment. Reduced infiltration resulting from litter particles blocking pores in the soil surface is likely the reason for the increased runoff volumes

Sorption of organic phosphorus compounds in Atlantic Coastal Plain soils

Organic phosphorus (P) can comprise a significant amount of the total P in animal wastes, yet there is little information on the potential for organic P to be transferred from soils to watercourses. We examined the adsorption of organic P compounds to soils typical of the southeastern United States, i.e., Blanton Sand (loamy, siliceous, thermic, Grossarenic Paleudult), Cecil sandy clay loam (fine, kaolinitic, thermic, Typic Kanhapludult), and a Belhaven sandy loam (loamy, mixed, dysic, thermic, Terric Medisaprist). The behavior of four organic P compounds was studied: adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP), and inositol hexaphosphate (IHP); while KH2PO4 (ortho-P) was used as an inorganic reference. Laboratory studies were conducted to determine the effects of concentration (0-130 p.g P mL-1 ), pH (4.6-7.6), and soil properties on P adsorption. All the organic P compounds had greater adsorption than KH 2PO4 on the Blanton and Cecil soils at all concentrations and ranges of pH. In the Belhaven soil, IHP had the greatest sorption followed by KH 2PO4 and the nucleotides (ATP, ADP, and AMP, respectively). Adsorption of organic P was positively correlated with soil organic matter and Fe and Al contents. The greater sorption of some organic P compounds over that of ortho-P suggests that these compounds may pose less of a threat to water quality, although this preferential sorption may increase soluble P in situations where there is displacement of ortho-P by organic P added in manures

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

Use: What is needed to support sustainability?

Increased demands for agricultural output per unit of land area must be met in a way that encourages improved efficiency and better stewardship of natural resources, including phosphate rock. Modern crops remove between 5 and 35 kg P/ha, with P removal exceeding 45 kg P/ha for high-yielding maize. In situations such as Sub-Saharan Africa, where soil fertility is low and P removal exceeds average inputs of 2 kg P/ha/year, the resulting nutrient depletion severely restricts yields (e.g., maize yields < 1,000 kg/ha/year) and accelerates soil degradation. In other regions, excessive P inputs produce economic inefficiencies and increase the risk of P loss, with negative environmental consequences. During the year of application, plants recover 15–25 % of the added P, with the remaining fraction converting to less soluble forms or residual P which becomes plant available over time. Improving P efficiency requires a balance between the imperatives to produce more food while minimizing P losses. Utilizing transdisciplinary approaches, a number of social, economic, and environmental goals can be simultaneously achieved if progress is made toward short- and long-term food security and global P sustainability. This chapter provides an overview of efforts to improve P use efficiency in agriculture ranging from promising germplasm, improved crop, and soil management scenarios, additives in animal diets to reduce P inputs and surplus P in the manure, and opportunities for P recycling in food and household waste. Challenges and opportunities associated with each option are discussed and transdisciplinary case studies outlined