Replacing 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 grasslegume 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 m 3 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 Nfertilizer 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.Abbreviations: ADG, average daily gain; AU, animal unit; BNF, biological N 2 -fixation; BW, bodyweight; CP, crude protein; DM, dry matter; GPA, gain per area; Grass+Clover, bahiagrass (no N fertilizer) during summer and a rye-oat-clovers mixture + N in winter; Grass+Clover+RP, bahiagrass (no N fertilizer in summer) with strip-planted rhizoma peanut during summer with a rye-oat-clovers mixture + N during winter; Grass+N, N-fertilized bahiagrass during summer with a mixture of N-fertilized cereal rye and oat during winter; IVDOM, in vitro digestible organic matter.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Plant litter deposition and decomposition play important roles in grassland nutrient cycling. The objective was to evaluate plant litter responses and estimate the N returns via plant litter in contrasting grazing systems, since legume inclusion is hypothesized to result in similar quantities of N return compared with N‐fertilized grass systems. Systems were (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer with a mixture of N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N); (b) bahiagrass (no N fertilizer) during summer and a rye–oat–clovers (Trifolium spp.) mixture + N in winter (Grass+Clover); and (c) bahiagrass (no N fertilizer in summer) with strip‐planted rhizoma peanut (Arachis glabrata Benth.) during summer with a rye–oat–clovers mixture + N during winter (Grass+CL+RP). Litter mass was greatest for Grass+N during October (4,430 kg organic matter [OM] ha−1) and least for Grass+CL+RP in June (490 kg OM ha−1). Litter N concentrations were greatest in Grass+N (16 g kg−1), with similar N concentration for Grass+Clover and Grass+CL+RP litter (14 g kg−1). Contribution of C3 species to litter mass increased from May to July but decreased thereafter. Overall, there was a net return of 47 kg N ha−1 yr−1 via litter across the three systems, and litter decomposition was similar in the three systems. Inclusion of forage legumes during cool and warm seasons in grazing systems has the potential to return similar amounts of N through plant litter deposition as grasses receiving moderate levels of N fertilizer.
Grass Forage Sci. 2020;75:153-158. wileyonlinelibrary.com/journal/gfs | 153
Bahiagrass (Paspalum notatum Flüggé) is the most utilized forage in Florida and requires N fertilization to optimize production. Integrating legumes into bahiagrass pastures may reduce N fertilizer inputs and improve forage nutritive value. This 2-yr, 2-location, on-farm study established two legumes, alfalfa (Medicago sativa L.) or rhizoma peanut (RP; Arachis glabrata Benth.), in mixtures with bahiagrass. We compared bahiagrass-legume mixtures + 45 kg N ha −1 harvest −1 with their non-N fertilized monocultures and with bahiagrass + 90 kg N ha −1 harvest −1 (N-fertilized bahiagrass). Treatments were bahiagrass, N-fertilized bahiagrass, bahiagrass-alfalfa, bahiagrass-RP, alfalfa, and RP. Variables analyzed included herbage accumulation (HA), botanical composition, forage N concentration, forage total N aboveground (TNAG), and N agronomic efficiency. Mixtures and N-fertilized bahiagrass resulted in similar cumulative HA (10,400 kg dry matter [DM] ha −1 yr −1 , on average) and they were greater than all other treatments (4,190 kg DM ha −1 yr −1 , on average). Alfalfa and RP represented low proportions of the mixed swards, with alfalfa proportion being as high as 16.1% and as low as 1.6%. Rhizoma peanut greatest proportion was 2.1% and the lowest was 0.5%. Mixtures and N-fertilized bahiagrass maintained similar N concentrations, but they were consistently lower than legume monocultures. The N-fertilized bahiagrass and mixture treatments resulted in the greatest TNAG in four out of the six sampling dates. The AE N of mixtures was typically greater than N-fertilized bahiagrass. Since legumes had low proportion in mixtures, 45 kg N ha −1 harvest −1 was the upper limit for reaching maximum HA in bahiagrass.
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