Water footprint, herbage, and livestock responses for nitrogen‐fertilized grass and grass–legume grazing systems

Abstract

AbstractReplacing N fertilizer with forage legumes may increase sustainability of grazing systems. The objectives were to evaluate herbage and animal responses and to quantify the water footprint associated with beef production in N‐fertilized grass or grass–legume systems during 4 yr under continuous stocking. The three year‐round forage systems were: Grass+N which included N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer which was overseeded with N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter; Grass+Clover included bahiagrass without N fertilizer during summer which was overseeded with rye, oat, and a mixture of clovers (Trifolium spp.) during winter; and Grass+Clover+RP included rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture during summer which was overseeded with a similar rye–oat–clover mixture as for Grass+Clover. Clover inclusion improved uniformity of herbage distribution throughout the winter. Including rhizoma peanut increased cattle average daily gain (ADG) by 74% during summer. The ADG in Grass+Clover+RP was 0.61 kg d−1 compared with 0.35 kg d−1 on Grass+N and Grass+Clover. The water footprint during summer was less in Grass+Clover+RP than Grass+Clover (18 and 25 m3 kg−1 bodyweight, respectively). Gain per area (GPA) was similar across all treatments through the year, indicating similar productivity in grass–legume and N‐fertilized grass systems. The N‐fertilizer inputs were reduced from 224 to 34 kg N ha−1 yr−1 in Grass+Clover+RP, compared to Grass+N. Inclusion of rhizoma peanut and clovers contributes to developing sustainable grazing systems with reduced levels of off‐farm inputs.