Long‐term effect of poultry litter application on phosphorus balances and runoff losses

Abstract

Assessment of annual and cumulative impacts of phosphorus (P) management strategies at field and watershed scales is needed to improve crop use efficiency and minimize environmental impacts. The objectives of this study were (a) to assess relationships among P balance, soil test P (STP) concentration, and runoff dissolved reactive P (DRP) concentration from fields receiving different poultry litter application rates (0.0-13.4 Mg ha -1 ) and (b) to determine the effect of long-term poultry litter application to fields on watershed DRP loss. Nutrient management practices, crop yield, STP, and runoff losses were assessed from nine fields and two watersheds located near Riesel, TX, from 2000 to 2015. Field-scale P balances were largely controlled by P application rate and exhibited a positive relationship with STP and runoff DRP flow-weighted mean concentration. Using a before-after control-impact experimental design that included monitoring at both field and watershed scales showed the influence of field P management on watershed DRP loss varied according to both source (i.e., P application rate, impacted area) and transport (i.e., hydrological connectivity) factors. Increased risk of watershed DRP loss was observed during wet years and years with two poultry litter applications to fields within the watershed.The percentage of the total watershed area receiving high rates of poultry litter also played a critical role in determining the risk of DRP loss. Findings highlight the impact of long-term P management strategies on DRP loss at both field and watershed scales and show the importance of incorporating hydrologic connectivity when assessing conservation effects on water quality.

Dual‐isotope approach for assessing agricultural management effects on nutrient dynamics: Proof of concept

“…Phosphorus is relatively immobile in soil compared to N due to a strong affinity for variable charged minerals and precipitation with Ca, Al, and Fe (Penn & Camberato, 2019). Additionally, P does not experience gaseous loss; thus, positive P balances often result in an accumulation of P within surficial soil layers (Bos et al., 2021; McLaren et al., 2015; Waldrip et al., 2015), as was observed in the current study (Table 1; see Soil Nitrogen Concentration and Isotopic Signature Section), which can lead to greater P losses in runoff and leachate (Bos et al., 2021; Harmel et al., 2019).…”

“…Runoff nutrient losses typically comprise a small fraction (N < 25%, P < 5%) of applied nutrients (Bos et al., 2021; Harmel et al., 2008), whereas crop nutrient uptake is not only influenced by nutrient application rate but also soil nutrient status, climate (e.g., precipitation amount and timing), management practices (e.g., tillage, nutrient placement, and nutrient timing), crop type, and crop genetics (Freeman et al., 2007; Torbert et al., 2001). Nutrient application rate therefore often determines nutrient balances in agricultural fields and watersheds (Bos et al., 2021; Hanrahan et al., 2019; Pease et al., 2018; Powers et al., 2016).…”

“…Native soil δ 15 N signatures were modified via cycling and loss because of increases in land use intensity following conversion to row crop agriculture in the decades prior to the nutrient addition trial (i.e., differences between SW12 and row crops in 2002), with annual N additions further separating signals between land uses and between fields receiving different N sources by 2017 (Figure 2). In contrast, when P was applied at agronomic rates pre-2002 (Mehlich-3 P was ∼23 mg kg −1 in 2001; Bos et al, 2021), P source signatures for both remnant prairie and row-cropped fields were similar and substantially less than the soil water equilibrium value, suggesting δ 18 Op signatures may largely reflect soil parent material (Figure 2). Annual P applications from 2002 through 2017, however, resulted in substantial increases in δ 18 Op for row-cropped fields (Figure 2).…”

“…Examining patterns in Hedley P fractions from 2002 through 2012 at the same study sites, Waldrip et al (2015) found similar trends in soil P concentration changes resulting from management practices in the nutrient addition trial. Increases in soil P concentration were related to field P balances (Bos et al, 2021; Figure 1) with greater P added with poultry litter than commercial fertilizer (Supplemental Table S2) and resulted in increased dissolved P losses in runoff (Harmel et al, 2009;Bos et al, 2021;Supplemental Table S2).…”

P‐FLUX: A phosphorus budget dataset spanning diverse agricultural production systems in the United States and Canada

“…Numerous studies have quantified P fluxes in cropland (Baker & Richards, 2002; Bos et al., 2021; Hanrahan et al., 2019; Lanyon et al., 2006; Ma et al., 2011; MacDonald et al., 2011), rangeland, and pasture systems (Obour et al., 2011; Rothwell et al., 2020; Sattari et al., 2016; Swain et al., 2007; Vendramini et al., 2007) across varying spatial and temporal scales. Accounting for P inputs (e.g., fertilizer application) and outputs (e.g., crop removal) to a defined system over a fixed time period is useful for determining P budgets.…”