Leaching Potential of Phosphite Fertilizer in Sandy Soils of the Southern Coastal Plain, USA

Abstract

Novel biotechnology on transgenic plants capable of metabolizing phosphite (Phi), a reduced form of P, could improve the effectiveness of P fertilizers and reduce the P footprint in agriculture with the benefit of suppressing weed growth. However, potassium Phi (K-Phi) salts used as fertilizer are highly soluble in water. At the same time, sandy soils of the Southern Coastal Plain are vulnerable to leaching losses resulting from long-term Pi fertilizer application. We performed a replicated leaching trial using five soil materials that included three surface and two subsurface layers from cultivated topsoil (Ap horizon) with contrasting Phi and Pi sorption capacities. Each soil received three treatments K-Phi at rates 0 (control), 24, and 49 kg P ha−1 and leached twice with de-ionized water. All K-Phi-treated soils leached Phi except for the controls. A phosphorus saturation ratio (PSR) calculated from P, Al, and Fe in acid extracts indicated increasing environmental risk of Phi leaching in soils with lower Phi and Pi sorption capacities at rising rates of applied K-Phi. Because plants rapidly absorb Phi, further studies on the environmental impact of K-Phi fertilizer use should include the interaction of plants with soil properties and soil microbial activity at optimal Phi application rates for growing transgenic plants able to use Phi as a nutrient source.

Phosphate leachate losses in sandy soil amended with different fertilizers and effects on cowpea yield

“…The high solubility of chemical fertilizers in soil as a result of their high water soluble P contents (Azevedo et al, 2018) explains the higher (436.5 and 229.7 mg l -1 equivalent to 873.0 and 459.5 kg P ha -1 in sole chemical and integrated fertilizer treatments, respectively) phosphate leachate losses in the low nutrient holding capacity sandy soil studied. Similar higher phosphate leachate losses have been documented for chemical fertilizer treated sandy soils (Szogi et al, 2021;Azevedo et al, 2018;Kang et al, 2011).…”

“…The low use efficiency placed at 30 to 35% for chemical fertilizer applied on sandy soils of the tropics (Li et al, 2019) has opened research areas for innovative ideas that will assure farmers in making optimal gains from every unit of chemical fertilizer applied. Achieving reduced nutrient leachate losses through careful selection of appropriate fertilizers for field application in sandy soils will not only increase economic returns (Kihara et al, 2020;Carstensen et al, 2020) to farmers but also significantly decrease the effects of nutrient leaching on water quality (Szogi et al, 2021;Xia et al, 2020;Bah et al, 2014) and global warming (Jantke et al, 2020;Schneider et al, 2019).…”