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North-West University (2020)

Assessment of maize productivity and soil health indicators following combined application of winery solid waste compost and inorganic fertilizers

Masowa, Manare Maxson

Titre : Assessment of maize productivity and soil health indicators following combined application of winery solid waste compost and inorganic fertilizers

Auteur : Masowa, Manare Maxson

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Agriculture with Agronomy 2020

Résumé partiel
Grape growing and winemaking process generate enormous amounts of solid waste materials that demand more economical and safe disposal technologies. In this study, co-composting and effective microorganisms (EM) technologies were employed to treat the winery solid waste (WSW), thereafter, the resultant compost was assessed for its physico-chemical properties, phyto-toxicity, nutrient release patterns and agronomic potential. Four WSW compost types produced comprised of EM inoculated or uninoculated compost with an initial heap height (hereinafter pile size) of 1.0 or 1.5 m. Samples of the cured composts were evaluated for physico-chemical properties and germination attributes at different extract concentrations (0, 10, 25, 50 and 100%) using cowpea, maize and tomato seeds. The results demonstrated that EM inoculation exerted a significant effect on compost Bray-2 P content while the interaction of EM inoculation and pile size similarly had significant effects on the ammonium-N content. The produced composts possessed high electrical conductivity values due to high concentrations of soluble salts that could be potentially toxic to crops and soil. The use of 1.0 m pile size promoted extended thermophilic phase during compost production that could ensure better sanitization of the final product. Maize and tomato showed higher degrees of phyto-toxicity at 50% extract concentration and above. The phyto-toxicity effects recorded in maize and tomato may be minimized by using lower application rates. The incubation study was carried-out using a buried-bag procedure to determine the P and K release patterns of inoculated compost with 1.0 m pile size in sandy loam soil under field conditions. Grounded compost was thoroughly mixed in zip-lock bags with 900 g surface soil at rates equivalent to 0, 5, 10, 20 and 40 t ha-1. One bag per treatment was destructively sampled at 0, 7, 21, 42, 63, 84, 105 and 126 days of incubation during which the available P and exchangeable K were analyzed. Net mineralized P ranged from -62 to 86 mg kg-1, while the net mineralized K varied between 41 and 2047 mg kg-1. The high net P and K mineralization suggests that the WSW compost can be used as a P and K source. However, its utilization as soil amendment must be cautious to mitigate the potential risks of unnecessary soil pH increase, nutrient imbalance, toxicity and the antagonistic effects of P and K on other plants nutrients.

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