Potential of Rhizobium sullae–Sulla coronaria Symbiotic Biological Nitrogen Fixation to Supplement Synthetic Mineral Nitrogen in Olive Tree Fertilization

Abstract

The aim of the present work is to compare olive tree nitrogen fertilization over two years of trials, using synthetic chemical fertilizers along with organic fertilizers composed of the green manure of sulla (Sulla coronaria) inoculated with the symbiont Rhizobium sullae or left uninoculated. The tests indicated that symbiotic nitrogen fixation promoted by the sulla-R. sullae symbiosis represents an important source of nitrogen that can replace or supplement synthetic nitrogen fertilizers for olive tree cultivation when sulla is inoculated with R. sullae in a soil already populated by the symbiont. Integration of the indigenous population of R. sullae via sulla inoculation with a selected strain yielded nodule formation in 100% of plants and produced a sufficient amount of biomass rich in nitrogen with a low C/N ratio. On the contrary, olive tree fertilization using the green manure of sulla that was not inoculated with the symbiont supplied significantly less organic nitrogen in 2017 and 2018, respectively, compared to the control. Optimal management of the multi-factorial approaches involved in green manure olive fertilization are also reported.

Cover crops mixtures with more legumes maximize biomass and N input in irrigated fruit crops in Brazil

“…This corroborates the usual recommendation of planting legumes as cover crops (Dakora and Keya, 1997;Douxchamps et al, 2010;Zullo et al, 2020), but the combination of several species, including nonlegumes, although in smaller proportion than the legumes, seems to be a better option (Grüner et al, 2020;De Notaris et al, 2021). The mixture maximizes the rapid formation of a soil cover, the exploration of the soil volume and the use of the available growth factors, from light to nutrients and water.…”

“…However, they are usually available in limited quantities and sometimes are produced far from the irrigated elds, implying in high transportation costs, due to their bulk volumes. An alternative is the use of cover crops, especially legumes, that can incorporate large volumes of biomass with part of the N content originated from symbiotic xation of atmospheric N 2 (Douxchamps et al, 2010;Couedel et al, 2018;Zullo et al, 2020;Hu et al, 2023).…”