http://www.bashanfoundation.org/gmaweb/pdfs/P-removal.pdf

Recent advances in removing phosphorus from wastewater and its future use as fertilizer (1997-2003).

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1434&context=agron_pubs

Biochar impact on nutrient leaching from a Midwestern agricultural soil.

A critical review on inhibition of anaerobic digestion process by excess ammonia.

Anaerobic digestion (AD) for biogas production leads to several changes in the composition of the resulting digestates compared to the original feedstock (ammonia content, pH, carbon to nitrogen ratio, etc.), which are relevant for the plant availability of macro- and micronutrients after field application. Increased NH4+-N content in digested slurries compared to undigested slurries does not guarantee improved uptake efficiency of slurry nitrogen and increased savings in fertilizer nitrogen. AD of crop residues and cover crops leads to an increase in the total amounts of mobile organic manures within the farming system, resulting in a higher nitrogen use efficiency and an increased scope for target-oriented nitrogen application in time and space, when needed by the crop, as an alternative to the site-bound soil incorporation as green manures. AD of dairy manure appears to reduce the fraction of immediate plant available phosphorus and micronutrients. This does, however, not affect short-term crop availability under field conditions. More studies are needed to improve current knowledge on sulfur losses during AD and fertilizer value of digestates.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/elsc.201100085

Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1133&context=agronomyfacpub

Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review

Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant.

Total world consumption of fertilizer N, P2O5, and K2O in 1990/1991 was 78, 37, and 26 million tons per annum, respectively, with a projected yearly increase of demand of about 2 to 3%. Trends in crop production (maize and wheat) in the last four decades show that N application rates increased about 15 times whereas its accumulation in grain increased only 3 to 4 times. At the same time nutrient recovery by crops remained relatively low (e.g. about 50% for N). This represents a potentially alarming situation from environmental, economic and resource conservation points of view and indicates an urgent need for improving efficiency of fertilizer use.

Controlled-release fertilizers to increase efficiency of nutrient use and minimize environmental degradation - a review

Using diverse technological approaches, many types of delivery devices have been used to supply plant nutrients at a controlled rate in the soil. One new approach is the use of hydrophilic polymers as carriers of plant nutrients. These polymers may be generally classified as 1) natural polymers derived from polysaccharides, 2) semi-synthetic polymers (primarily cellulose derivatives), and 3) synthetic polymers. By controlling the reaction conditions when forming the polymers, various degrees of cross-linking, anionic charge, and cationic charge can be added, thereby changing their effectiveness as fertilizer carriers. When fertilizer-containing solutions are mixed with hydrophilic polymers to form a “gel” prior to application in the soil, the release of soluble nutrients can be substantially delayed compared with soluble fertilizer alone. The effectiveness of a specific controlled-release polymeric system is determined in part by its specific chemical and physical properties, its biodegradation rate, and the fertilizer source used. Addition of some polymers with nutrients has been shown to reduce N and K leaching from well-drained soils and to increase the plant recovery of added N, P, Fe, and Mn in some circumstances

Using hydrophilic polymers to control nutrient release

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.

/pdf/sorption-of-organic-phosphorus-compounds-in-atlantic-coastal-2m6wirvc2a.pdf

Sorption of organic phosphorus compounds in Atlantic Coastal Plain soils

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.

/pdf/field-scale-evaluation-of-phosphorus-leaching-in-acid-sandy-4vguddh5ms.pdf

Robert L. Mikkelsen

Papers

Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant.

Controlled-release fertilizers to increase efficiency of nutrient use and minimize environmental degradation - a review

Using hydrophilic polymers to control nutrient release

Sorption of organic phosphorus compounds in Atlantic Coastal Plain soils

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