Assessment of the Status of Microelements in the Selected ERPP Irrigation Schemes in Unguja and Pemba Islands, Zanzibar

Abstract

Aims: To investigate the status of microelements in the selected expanding rice production project irrigation schemes in Unguja and Pemba Islands, Zanzibar Study Design:  Standard grid soil survey Place and Duration of Study: Unguja and Pemba Isles Zanzibar during October and December, 2017. Methodology: Detailed soil survey at a scale of 1:10,000 was conducted using pedogeomorphic approach from which composite soil samples were collected at a depth of 0 – 30 cm. Each mapping unit had a representative profile around which soil samples were collected at a radius of 20 – 30 m for microelements investigation. Results: Results showed that the status of micronutrients (Fe, Zn and Mn) in the selected irrigation schemes varied (P ≤ 0.05) with schemes and their respective mapping units, although in some cases, variations were not significant (P ≤ 0.05). In Unguja and Pemba irrigation schemes, there were generally moderate or optimum DTPA - extractable Fe, low DTPA - extractable Zn and high DTPA - extractable Mn levels. The data suggest that except for DTPA - extractable Zn which was low in all irrigation schemes, Fe and Mn were not limited to crop growth and development. However, in Kwalempona (KWA-MP1: Hi1) and Machigini (MA-MP1: Hi1) irrigation schemes, Fe levels were rated as high or above critical limits. Additionally, the overall soil reaction in these irrigation schemes ranged from neutral (N) to very strongly acidic (VSA). Conclusion: In all, these results suggest that to improve crop production in the selected irrigation schemes, low Zn availability should be addressed by including it into fertilizer programs as well as proper soil pH management by reducing soil acidity through liming in the higher elevations for irrigation development.