Abstract
Garlic is an important cash crop for smallholder farmers in Ethiopia. Bulb quality is an important attribute that adds to the use and marketability of the crop. However, garlic bulb quality is constrained by several factors in the country among which imbalanced and low availability of nutrients in the soil is prominent. Therefore, a study was conducted on two soil types (Andosol and Vertisol) with the objective of elucidating the effect of nitrogen, phosphorus, and sulphur application on the quality of the crop. The treatments consisted of three levels of nitrogen (0, 92, 138 kg N ha-1), three levels of phosphorus (0, 40, 80 kg P ha-1), and three levels of sulphur (0, 30, 60 kg S ha-1). The experiment was laid out as a randomized complete block design in a factorial arrangement with three replications on each soil type. The results revealed that the main as well as the interaction effects of N, P, and S fertilizers on both soil types significantly (P ≤ 0.05) influenced bulb quality, namely, dry matter percentage, total soluble solids, pungency, bulb protein content, and bulb weight loss in storage, and concentrations of major nutrients in the bulb tissues. The bulb quality indices studied on both soil types correlated positively and significantly with each other but had a negative correlation with bulb weight loss. This result indicates favorable effects of integrated application of nitrogen, phosphorus and sulphur on garlic bulb quality. Combined applications of 92 kg N + 40 kg P + 30 kg S ha-1 and 138 kg N + 40 kg P + 60 kg S ha-1 led to the attainment of optimum bulb quality attributes on Andosol and Vertisol, respectively. However, it was application of 92 kg N + 40 kg P + 30 kg S ha-1 that was found to be economical for farmers. Key words: Andosol, bulb quality, inorganic fertilizer, nutrient concentration, soil type, Vertisol.
Highlights
The composition of a garlic bulb varies greatly depending on cultivar, agronomic practices, climate, soil fertility, and postharvest storage conditions that determine the quality and intensity flavor as well as nutritional and nutraceutical values of the crop
The present investigation was carried out to assess the effect of nitrogen, phosphorus and sulphur rates on the quality of garlic bulb grown on an Andosol and a Vertisol soils
The bulb total soluble solids (TSS) and protein content and bulb weight loss were significantly influenced by soil type with an increased in TSS and bulbs weight loss due to Vertisol as compared to those produced on Andosol, but the protein content was improved due to Andosol
Summary
The composition of a garlic bulb varies greatly depending on cultivar, agronomic practices, climate, soil fertility, and postharvest storage conditions that determine the quality and intensity flavor as well as nutritional and nutraceutical values of the crop. Different types of soils have different characteristics that influence growth and yield of crops Both macro and micro-nutrients have various levels of availability in different soils and their removal by different crops varies. Balanced fertilizer application is essential for the vegetative growth and, for producing crops with top quality and high yields especially on soils that are cultivated continuously. Phosphorus, potassium and other inputs in the soil could improve yields and quality of vegetables and other crops (Nai-hua et al, 1998). According to these authors, fertilizer management practices should balance the supply of N, P and K as well that other nutrients based on soil test results. The present investigation was carried out to assess the effect of nitrogen, phosphorus and sulphur rates on the quality of garlic bulb grown on an Andosol and a Vertisol soils
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