Managing agricultural phosphorus to minimize water quality impacts

Abstract

Eutrophication of surface waters remains a major use-impairment in many countries, which, in fresh waters, is accelerated by phosphorus (P) inputs from both point (e.g., municipal waste water treatment plants) and nonpoint sources (e.g., urban and agricultural runoff). As point sources tend to be easier to identify and control, greater attention has recently focused on reducing nonpoint sources of P. In Brazil, agricultural productivity has increased tremendously over the last decade as a consequence, to a large extent, of increases in the use of fertilizer and improved land management. For instance, adoption of the "4R" approach (i.e., right rate, right time, right source, and right placement of P) to fertilizer management can decrease P runoff.Additionally, practices that lessen the risk of runoff and erosion, such as reduced tillage and cover crops will also lessen P runoff. Despite these measures P can still be released from soil and fluvial sediment stores as a result of the prior 10 to 20 years' management. These legacy sources can mask the water quality benefits of present-day conservation efforts. Future remedial efforts should focus on developing risk assessment indices and nonpoint source models to identify and target conservation measures and to estimate their relative effectiveness. New fertilizer formulations may more closely tailor the timing of nutrient release to plant needs and potentially decrease P runoff. Even so, it must be remembered that appropriate and timely inputs of fertilizers are needed to maintain agricultural productivity and in some cases, financial support might also be required to help offset the costs of expensive conservation measures.

A Century of Legacy Phosphorus Dynamics in a Large Drainage Basin

“…More than half the arable land in the drainage basin is tile-drained (Feick et al, 2005). Rapid transport pathways could be managed, however, through the timing of manure and fertilizer application, manure and fertilizer application methods, choice of tillage, and crop rotations that reduce transport (Schoumans et al, 2014;Sharpley, 2016). …”

“…Once identified, soil-P reserves could be utilized by actively reducing the labile pool to agronomically critical levels. Rowe et al (2015) also argued that "full exploitation" of legacy P requires a more holistic approach to agriculture that involves technological advances, such as breeding more P-efficient crops and engineering microbes to better mobilize soil P. Buffer strips and sedimentation ponds are examples of common practices to intercept nutrient loss and reduce transport to surface water (Schoumans et al, 2014;Sharpley, 2016). To be effective, these measures must be adapted to local conditions and informed by research that links farming practices with nutrient loss pathways (Withers, Neal, et al, 2014).…”

Impact of Tea Processing Water Wastes on Phytoplankton Composition of Tshinane River, Limpopo Province

“…The concentration of phosphates in water bodies is also an indicator of eutrophication, Singare et al [14], argues that, even at low level, phosphate pollutants accumulate in the form of sediments and settle down at the bottom. According to [15], there is a need to minimize the phosphate originating from commercial farming so as to protect aquatic ecosystem. Table 1 illustrates the identified phyla for all the areas that were sampled in May 2015.…”

The Implications of Economic Development, Climate Change and European Water Policy on Surface Water Quality Threats

“…Excessive amounts of nutrients, mainly nitrogen and phosphorus, get to water primarily from runoff from agricultural lands, untreated or insufficiently treated wastewater effluent and with precipitation. Eutrophication causes changes in ecosystem structure and limits ecosystem services, enabling rapid growth of cyanobacteria, algae and aquatic plants, decrease in fauna and flora species diversity, general water quality detriment, limited use of water resources, increased cost of water treatment [Correll 1998, Rabalais 2002, Moss et al 2011, Orzepowski et al 2014, Withers et al 2014, Dąbrowska et al 2016, Sharpley 2016, Bouwman et al 2017.…”