Long-Term Effects of Grazing and Haying on Soil Nutrient Dynamics in Forage-Based Beef Cattle Operations

Abstract

ABSTRACT Nutrient levels over a 15-year period (1988–2002) were compared to evaluate the long-term effects of differing pasture management treatments (grazed-only or grazed and hayed) on soil phosphorus (P) and other crop nutrients (K, Ca, and K) in subtropical pastures planted with either bahiagrass (BG, Paspalum notatum Flügge) or rhizoma peanut (Arachis glabrata Benth)-mixed grass association (RP-G). Pasture management (P ≤ 0.001) significantly affected the levels of soil P and other crop nutrients. Mehlich-1 concentrations of P tended to be smaller (21%) in pasture fields that were both grazed and hayed than pasture fields that were grazed only. This may have occurred because hay removal lowered soil P levels. During the last 15 years (1988–2002), Mehlich-1 concentrations for P, K, Ca, Mg, and soil pH have declined by about 7, 38, 46, 61, and 23% in pastures with BG and 27, 55, 76, 56, and 22% for pasture fields with RP-G that were grazed in spring and hayed in early fall, respectively. Calcium appears to be decreasing more rapidly at a rate of 11.5 mg kg−1 yr−1 than Mg, which declined by about 0.8 mg kg−1 yr−1, leading to a significant increase in the Ca:Mg ratio (+2.4% yr−1). The combined grazing in spring and haying in early fall can be considered a pasture best management practice (BMP) for maintaining nutrient balance in the pastures, thereby avoiding the potential negative impact to the environment. The levels of soil P in 2002 (averaged across pasture management) of 57.6 ± 23.4 mg kg−1 was not high enough to be of environmental concern, so annual additions of P fertilizers especially for pastures with RP-G would still be practical to sustain forage productivity in subtropical beef cattle grazing system. Soil fertility management is important for ensuring that nutrient resources within the ecosystems are depleted and that nutrients lost from haying are replenished through fertilizer additions.