Phosphorus Flows, Surpluses, and N/P Agronomic Balancing When Using Manure from Pig and Poultry Farms

Abstract

The pig and poultry industries continue to grow across the world and together they provide the majority of meat consumed. The European Union (EU) in particular has the highest global relative meat production by monogastrics (i.e., pig and poultry). The fate of phosphorus (P) in pig and poultry farming was studied, accounting for P content in feed, animals, manure, soil, and runoff. P input from manure, and P offtake in crops receiving manure, were plotted against each other to arrive at “safe” P loading rates, in order to minimize soil P surpluses along the lines of the EU Nitrogen Expert Panel in their work with nitrogen (N). However, it was observed that it is the N/P ratio and the background soil P levels that determine whether a certain manure will end up producing surplus levels of soil P. Critical N/P weight ratios were derived over different crop P offtake rates when applying stored manure to croplands. At spreading rates of 170 and 250 kgN/ha/year and a crop P offtake of 15 or 30 kgP/ha/year, stored pig and chicken manure result in soil P surpluses. An important factor in determining effective N/P ratios is the plant availability of N in stored manure, which runs at around 47%, estimated from previously published results. The minimization of N losses to the atmosphere and to groundwater in housing, storage, and spreading of manure has a major impact on the N/P weight ratio of the manure that ends up on fields. In most cases, half of the ex-animal N content has been lost in stored or degraded manure, with N/P weight ratios running at two and less. Following only the EU Nitrates Directive, which allows for a maximum of 170 kgN/ha/year in NVZs (Nitrate Vulnerable Zones), will often result in soil P surpluses leading to runoff losses to adjacent water bodies. Therefore, for the pig and poultry industries to continue thriving, measures are required to better manage manure, including improved storage and spreading techniques, acidification, separation, struvite extraction and ammonia stripping of pig slurry, and drying and pelleting of poultry litter. This way, excess manure and derived biofertilizers from animal farms can find their way back into the commercial market, instead of ending up as legacy P in watersheds and coastal zones.

Predicting the short‐ and long‐term effects of recycling organic wastes in cropping systems with the PROLEG tool

“…Concerning P and K, a simpler approach than for N was included in the PROLEG tool: a balance between crop exports and fertilizers and OW inputs was computed:These balances were used to verify whether inputs (mineral fertilizers and OWs) were compensated for crop exports at the crop rotation scale and whether surpluses were limited (Rosemarin et al, 2021). Optionally, the tool used this balance to compute P and K mineral fertilization requirements.…”

“…These balances were used to verify whether inputs (mineral fertilizers and OWs) were compensated for crop exports at the crop rotation scale and whether surpluses were limited (Rosemarin et al, 2021). Optionally, the tool used this balance to compute P and K mineral fertilization requirements.…”

“…It may also increase soil‐carbon storage and soil physical and biological fertility depending on the type and quantity of OW applied (Bhogal et al, 2018). However, recycling OWs is associated with risks of soil contamination by metals, organic contaminants or pathogens (Fijalkowski et al, 2017), groundwater pollution by nitrate leaching (Asada et al, 2015), excess phosphorus application (Rosemarin et al, 2021), air pollution because of ammonia volatilization and greenhouse gas (GHG) emissions with possible trade‐offs between these emissions (Duncan et al, 2017) and soil compaction because of the use of heavy machinery (Stettler et al, 2014). Depending on the balance between carbon storage, omitted GHG related to saved mineral fertilizers, upstream (process, storage, transport) and field GHG emissions, the contribution to climate change mitigation varies with the type of OW and their treatments (Kreidenweis et al, 2021).…”

Annual Ryegrass (Lolium multiflorum Lam.) Growth Response to Nitrogen in a Sandy Soil Amended with Acidified Manure and Municipal Sludge after “Quick Wash” Treatment

“…Several studies on the acidification of organic wastes show that this treatment effectively decreases NH 3 gas losses during their handling and disposal [11][12][13]. Acidification impacts multiple chemical and microbial processes in organic wastes, changing their composition and promoting the release of soluble P [14], thus increasing the risk of P pollution following land application [6,15,16]. As an alternative to reduce the environmental risks from land disposal of P-rich wastes, the U.S. Department of Agriculture (USDA) developed and patented a process called "Quick Wash" (QW) to selectively extract and recover P from organic wastes, such as poultry litter, livestock manure, and MS, before land application [17,18].…”

Legacy phosphorus in Alabama Hartsells soil after long‐term amendment with broiler litter

“…While BL has long been used as crop fertilizer, nutrient contents can be highly variable due to animal diet, CAFO management, and other factors. Generally, BL application rate is based on the recommended crop N requirement, but the low N:P ratios of most BL results in P overapplication (Pagliari & Laboski, 2014; Rosemarin et al., 2021).…”