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To minimize environmental damage, conserve global diminishing fertilizer reserves, all while maximizing food production, it is essential that farmers apply phosphate fertilizers at the optimal rate. The purpose of this study is to assess grower attitudes and behavior, with respect to proper application of phosphorus, and to investigate how certain exogenous factors might influence such applications. Data were analyzed from a survey conducted in North Carolina, USA, with 122 farmer participants. The findings reveal that annual phosphorus applications consistently exceed recommendations, which indicates overapplication, leading to economic inefficiency and environmental concerns. Overapplication is neither due to knowledge gaps in nutrient concentrations in the soil nor the lack of interest in soil sampling, as 99% of farmers submit soil tests as frequently or more frequently than every two years. Only 36% of growers indicated that they would not apply phosphorus if their soil report indicated that levels were sufficient, and that none was required. Additionally, overapplication is not strongly influenced by price effects, as only nine percent of growers abandoned applications in 2021, following a dramatic spike doubling fertilizer prices. The adoption of reduced phosphate fertilization will depend on strong local trusted technical assistance and continued extension education. 

Abstract National nutrient inventories provide surplus phosphorus (P) estimates derived from county‐scale mass balance calculations using P inputs from manure and fertilizer sales and P outputs from crop yield data. Although bioavailable P and surplus P are often correlated at the field scale, few studies have investigated the relationship between measured soil P concentrations of large‐scale soil testing programs and inventory‐based surplus P estimates. In this study, we assessed the relationship between national surplus P data from the NuGIS dataset and laboratory‐measured soil test phosphorus (STP) at the county scale for Arkansas, North Carolina, and Oklahoma. For optimal periods of surplus P aggregation, surplus P was positively correlated with STP based on both Pearson (Arkansas:r = 0.65, North Carolina:r = 0.45, Oklahoma:r = 0.52) and Spearman correlation coefficients (Arkansas:ρ = 0.57, North Carolina:ρ = 0.28, and Oklahoma:ρ = 0.66). Based on Pearson correlations, the optimal surplus P aggregation periods were 10, 30, and 4 years for AR, NC, and OK, respectively. On average, STP was more strongly correlated with surplus P than with individual P inventory components (fertilizer, manure, and crop removal), except in North Carolina. In Arkansas and North Carolina, manure P was positively correlated with STP, and fertilizer P was negatively correlated with STP. Altogether, results suggest that surplus P moderately correlates with STP concentrations, but aggregation period and location‐specific factors influence the strength of the relationship. 

Fertilizer utilization is critical for global food security. This study examines the occurrence of trace elements (TEs) and Sr isotope (87Sr/86Sr) variations in phosphate rocks and mineral fertilizers from a sample collection representative of major phosphate producing countries. We show high concentrations of several TEs in phosphate rocks (n=76) and their selective enrichment in phosphate fertilizers (n=40) of specific origin. Consistent with the concentrations in parent phosphate rocks, phosphate fertilizers from the U.S. and Middle East have substantially higher concentrations of U, Cd, Cr, V, and Mo than in fertilizers from China and India. Yet, fertilizers from China and India generally have higher concentrations of As. The 87Sr/86Sr in phosphate fertilizers directly mimic the composition of their source phosphate rocks, with distinctive higher ratios in fertilizers from China and India (0.70955–0.71939) relative to phosphate fertilizers from U.S. and Middle East (0.70748–0.70888). Potash fertilizers have lower Sr and TEs and higher 87Sr/86Sr (0.72017–0.79016), causing higher 87Sr/86Sr in mixed NPK-fertilizers. Selective extraction (Mehlich III) of soils from an experimental agricultural site shows relative enrichment of potentially plant-available P, Sr, and TEs in topsoil, which is associated with Sr isotope variation towards the 87Sr/86Sr of the local utilized phosphate fertilizer. 

Phosphate fertilizers may contain elevated concentrations of toxic metals and metalloids and therefore, their excessive application can result in the accumulation of both phosphorus (P) and metal(loid)s in agricultural soils. This study aims to investigate the occurrence, distribution, and potential plant-availability of metal(loid)s originating from phosphate fertilizer in a long-term experimental field at the Tidewater Research Station in North Carolina, where topsoil (10-20 cm deep) and subsoil (up to 150 cm deep) samples were collected from five plots with consistent and individually different application rates of P-fertilizer since 1966. We conducted systematic analyses of P and metal(loid)s in bulk soils, in the plant available fraction, and in four sequentially extracted soil fractions (exchangeable, reducible, oxidizable, and residual). The results show that P content in topsoils were directly associated with the rate of P-fertilizer application (=1, p<0.05). Furthermore, P concentrations were highly correlated with concentrations of Cd, U, Cr, V, and As in the bulk topsoil (>0.58, p<0.05), as well as the potential plant-available fraction (>0.67, p<0.01), indicating the accumulation of the fertilizer-derived toxic metal(loid)s in the topsoil. Significant correlations (p<0.001) of metal(loid)s concentrations between the bulk soil and the potential plant-available fraction raises the possibility that P-fertilizer application could increase the accumulation of toxic metal(loid)s in plants, which could increase human exposure. Results from sequential leaching experiments revealed that large portions of the trace elements, in particular Cd, occur in the soluble (exchangeable and reducing) fractions of topsoil with higher P-fertilizer input, whereas the levels of redox-sensitive elements (As, V, U, Cr) were higher in the reducible and oxidizable fractions of the soils. Overall, the data presented in this study demonstrate the effect of long-term P-fertilizer application on the occurrence and accumulation of a wide range of toxic metal(loid)s in agricultural topsoil. 

Removing phosphorus (P) from water and wastewater is essential for preventing eutrophication and protecting environmental quality. Lanthanum [La(III)]-containing materials can effectively and selectively remove orthophosphate (PO4) from aqueous systems, but there remains a need to better understand the underlying mechanism of PO4 removal. Our objectives were to 1) identify the mechanism of PO4 removal by La-containing materials and 2) evaluate the ability of a new material, La2(CO3)3(s), to remove PO4 from different aqueous matrices, including municipal wastewater. We determined the dominant mechanism of PO4 removal by comparing geochemical simulations with equilibrium data from batch experiments and analyzing reaction products by X-ray diffraction and scanning transmission electron microscopy with energy dispersive spectroscopy. Geochemical simulations of aqueous systems containing PO4 and La-containing materials predicted that PO4 removal occurs via precipitation of poorly soluble LaPO4(s). Results from batch experiments agreed with those obtained from geochemical simulations, and mineralogical characterization of the reaction products were consistent with PO4 removal occurring primarily by precipitation of LaPO4(s). Between pH 1.5 and 12.9, La2(CO3)3(s) selectively removed PO4 over other anions from different aqueous matrices, including treated wastewater. However, the rate of PO4 removal decreased with increasing solution pH. In comparison to other solids, such as La(OH)3(s), La2(CO3)3(s) exhibits a relatively low solubility, particularly under slightly acidic conditions. Consequently, release of La3+ into the environment can be minimized when La2(CO3)3(s) is deployed for PO4 sequestration.