Flue gas desulfurization gypsum and grass buffer strip influence on runoff and nutrient loss from inorganically and organically fertilized corn on a US Coastal Plain soil

Abstract

Broiler litter (BL) and flue gas desulfurization gypsum (FGDG), both readily available in the US Southeast, can potentially ameliorate soil constraints adversely affecting agricultural productivity and environmental quality in the region. However, benefits and risks must be evaluated prior to making recommendations to producers. The effectiveness of a combination of FGDG and grass buffer strips (GBS) to reduce edge-of-field nutrient losses from corn (Zea mays L.) production under inorganic (NPK) or organic (BL) fertilization was evaluated on Coastal Plain soils near Tifton, Georgia, from April of 2014 through January of 2017. Nine treatments were randomly established in each of three replications on plots instrumented to collect runoff. This was the first phase of a three-phase study. Treatments consisted of combinations of three fertilizer treatments (NPK, BL, and BL+FGDG) and three GBS treatments (no GBS [–GBS], GBS without FGDG [GBS−FGDG], and GBS with FGDG [GBS+FGDG]). A tenth treatment of NPK+FGDG without GBS was also included. Annual rates for BL and FGDG were 13.45 Mg ha−1 each. The BL rate was based on a high nitrogen (N) demand of corn and would represent a risky scenario for nutrient loss. Runoff and concentrations and loads of nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), total Kjeldahl nitrogen (TKN), dissolved reactive phosphorus (DRP), and total P (TP) were determined in runoff from 29 storms from May of 2015, through January of 2017. Rainfall partitioned into runoff (percentage runoff) decreased by 50% to 70% under –GBS with BL or BL+FGDG compared with NPK fertilization, and under GBS–FGDG or GBS+FGDG compared with –GBS for NPK and BL fertilization. Under –GBS, concentration of DRP and TP increased by ~160% from BL compared with NPK fertilization, and by 150% for DRP and by 115% for TP from BL+FGDG compared with NPK fertilization. On the other hand, the combined BL+FGDG and GBS+FGDG treatment reduced nutrient concentration by 65% to 80% compared with BL with –GBS (a standard practice), and nutrient load by 40% to 70% compared with NPK with –GBS (another standard practice) or BL with –GBS. Results indicate the potential for FGDG to improve edge-of-field runoff water quality when applied to fields with BL and to edge-of-field GBS. In planned follow-up articles, results will be compared with phase-2 when BL and FGDG rates were reduced by a third and phase-3 when BL application was discontinued.