Abstract
Green manuring is recognized as a viable alternative to improve nutrient cycling in soils. The aim of this study was to evaluate the phytomass production and nutrient accumulation in shoots of the summer green manures jack bean [Canavalia ensiformis (L.) DC.], dwarf pigeon pea (Cajanus cajanvar var. Flavus DC.), dwarf mucuna [Mucuna deeringiana (Bort) Merr] and sunn hemp (Crotalaria juncea L.), under nitrogen fertilization and/or inoculation with N-fixing bacteria. A split plot design was arranged with the four Fabaceae species as main plots and nitrogen fertilization (with and without) and inoculation with diazotrophic bacteria (with and without) as the subplots, in a 2² factorial. The experiment was arranged as a randomized complete block design with four replications. In the conditions of this trial, the sunn hemp had the highest production of shoot phytomass (12.4 Mg ha-1) and nutrient accumulation, while the dwarf mucuna had the lowest production of shoot phytomass (3.9 Mg ha-1) and nutrient accumulation. The results showed no effect of nitrogen fertilization or inoculation with N-fixing bacteria on the production of shoot phytomass and nutrient accumulation, except for inoculation without nitrogen fertilization, resulting in greater P accumulation (p <0.05) in the sunn hemp and greater Zn and Mn accumulation in the dwarf mucuna. These findings indicate that N fertilization or inoculation with N2-fixing bacteria for Fabaceae are low efficiency practices in the edaphoclimatic conditions of this study.
Highlights
Green manuring is a practice that allows the input of large amounts of biomass, increasing, over the years, nutrient content and organic matter in the soil for subsequent crops through nutrient cycling
The Fabaceae to be used as green manure is selected preferably among species that produce greater volume of dry matter, are less susceptible to pests, diseases and water and nutritional stresses and have relatively uniform seeds that are suitable for seeders (Miyasaka, 1984)
Flavus DC), jack bean [Canavalia ensiformis (L.) DC] and dwarf mucuna [Mucuna deeringiana (Bort) Merr.] are annual plants that can achieve on average dry matter yields of 19.3, 7.0, 6.6, and 3.3 Mgha-1, respectively (Calegari et al, 1993)
Summary
Green manuring is a practice that allows the input of large amounts of biomass, increasing, over the years, nutrient content and organic matter in the soil for subsequent crops through nutrient cycling. Within the steps of nutrient cycling, shoot biomass and nutrient content are the main components of the nutrient balance in the soil-plant system. Subsequent steps, which are important for green manuring success, will depend on the quality of residues produced, amount of nutrients released during decomposition and temporal synchronization between nutrients released by residue decomposition and crop requirement (Matos et al, 2008). The Fabaceae to be used as green manure is selected preferably among species that produce greater volume of dry matter, are less susceptible to pests, diseases and water and nutritional stresses and have relatively uniform seeds that are suitable for seeders (Miyasaka, 1984). Flavus DC), jack bean [Canavalia ensiformis (L.) DC] and dwarf mucuna [Mucuna deeringiana (Bort) Merr.] are annual plants that can achieve on average dry matter yields of 19.3, 7.0, 6.6, and 3.3 Mgha-1, respectively (Calegari et al, 1993)
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