Peanut (Arachis hypogaea) crop within a circular economy perspective: potential use of biomass as forage

The use of annual peanut (Arachis hypogaea) as dual-purpose crop providing both seeds for human consumption and fodder for ruminant feeding may be of interest to connect food and feed chains in a perspective of circular economy and agricultural waste valorization. In this study we examined yield and chemical composition of epigeal biomass of peanut as influenced by both cultivar (Cv) and cutting height. Three late-maturing peanut Cv, namely IPG 1288, AG 44, and Lotus, were sown in three 1-ha fields near Caserta (Italy) in May 2020. At harvesting maturity of pods (September 2020), three 2 x 1 m strips/field were randomly selected, and the plants (n. 10) were manually cut at the ground level. The plants were weighted to determine biomass yield and then fractionated into 3 layers corresponding to the upper (first 20 cm in height), middle (20-40 cm), and basal (from 40 cm to the root insertions) parts of the plants. Each layer was further separated into stems and leaves to assess plant traits and yield components. The samples so generated were oven dried to determine chemical composition. Data on plant height, whole plant crude protein (CP) content, and dry matter (DM) and CP yield ha-1 were analyzed by one-way anova with Cv as factor. Data on leaf to stem ratio, and chemical composition were analyzed by a two-way anova (proc GLM) with Cv, layer, and their interaction as factors. The Cv IPG 1288 was taller than AG 44 and Lotus (p<0.01) and showed the highest DM and CP yield ha-1 (p<0.001) followed by AG 44 (p<0.001) and Lotus (p<0.001). The CP and NDF contents of the whole plant did not differ among Cv and averaged on a DM basis 18.3±0.38 SEM and 40.3±0.79, respectively. The interaction Cv*layer was always significant. All Cv were leafier in the upper layer with the higher value observed for IPG 1288 followed by AG 44 (p<0.001) and Lotus (p<0.001). In similarity, the CP content was higher in the upper layer of IPG 1288 followed by AG 44 (p<0.001) while Lotus presented the greatest protein content in the middle layer. The basal layer was the poorest in proteins with the lower value observed for IPG 1288. Overall, the DM and CP yield of peanut biomass are quite variable in relationship to the botanical variety, but chemical composition can be significantly modified through a careful choice of the cutting height. The chemical characteristics propose biomass peanut as medium quality legume forage.