Optimizing Vermicompost Concentrations for the N Nutrition and Production of the Legume Lupinus angustifolius
2015
Allardice, Roderick P. | Kapp, Caro | Botha, Alfred | Valentine, Alex
Vermicomposts (VCs) are the solid excreta of earthworms known to contain plant available nutrients, large amounts of microbial life and diversity, and plant growth regulating hormones. VCs may play an integral role in the nitrogen nutrition of Lupinus angustifolius and function to reduce the reliance of legume crops on chemical fertilizers. The aim of the present study was to determine the role of varying concentrations of chicken manure VC on the biomass production and N nutrition of the legume, L. angustifolius . The effect of increasing concentrations of VCs has been investigated, in conjunction with commercial rhizobia inoculum additions on the biomass yield of L. angustifolius . Plants were germinated and allowed to establish for 10 days in various mixtures of VC, rhizobia inoculum, and quartz sand under glasshouse conditions. After cultivation of a further 30 days, the plants were harvested and analyzed for tissue nutrient concentrations. The VC-containing substrates were assessed for wide-spectrum soil analyses and microbial diversity via Biolog EcoPlates. The combined treatments of 5% VC and rhizobia inoculation yielded the greatest biomass response. Furthermore, the addition of VC allowed for bacterial nitrogen fixation within non-rhizobia treatments. Nematode numbers and diversity grew with increases in VC concentrations, likely driven by similar increases in abundance of their microbial prey. However, changes in VC concentration had no effect on bacterial guild structure. In conclusion VC concentrations should be an important consideration for substrate nutrient availability, microbial abundance, and bacterial nitrogen fixation.
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