Evaluation of Zinc and Iron Availabilities in Soils of Selected Areas of Ethiopia for Haricot Bean Production under Greenhouse Condition

Abstract

The availability of zinc and iron in soils of Kontela, Taba, Jole Andegna, Tenkaka Umbulo, Alage and Huletegna Choroko was not evaluated for production of Haricot bean. Therefore, this study was conducted to verify the results of laboratory analysis for micronutrients and evaluate the availability of zinc and iron in the above soils for haricot bean production. A greenhouse experiment was conducted in soils collected from the above sites using the following treatments: (1) no fertilizer (2) application of N and P; (3) application of N, P and Zn; (4) application of N, P, and Fe; (5) application of N, P, Zn and Fe (6) application of Zn only; (7) application of Fe only. Sources of Zn, iron, N and P were zinc sulfate heptahydrate (ZnSO₄.7H₂O (21% Zn)), iron sulfate heptahydrate (FeSO₄.7H₂O (20% Fe)), urea and TSP, respectively. Haricot bean variety Nasir was planted in a pot filled with 5 kg soil. ZnSO₄∙7H₂O and FeSO4.7H₂O were sprayed on the leaves, and urea and TSP were applied to the soil just before planting. Four haricot bean seeds per pot were sown and, later, thinned to two seedlings. Grain yield, plant height, number of pods per plant and number of seeds per pod were collected. Leaves and seeds were analyzed for micronutrients using Microwave Plasma Atomic Emission Spectrometer (MPAES). Results indicated that application of NPZn and NPFe did not significantly (p<0.05) influence haricot bean yield compared to NP fertilizers. However, application of Zn with NP significantly increased grain yield compared to the no fertilizer treatment. The highest grain yield (16.60 g/pot) was observed at application of NPZn, while the lowest grain yield (12.80 g/pot) was observed with Fe only treatment. Plant height also followed similar trend with grain yield. Although not significant, application of Zn increased number of pods per plant compared to the no fertilizer. The most pods per plant (7.50) were observed with application of NP, while the least pods per plant (6.22) were obtained with Fe only treatment. Application of Fe and Zn either alone or combined with NP produced significantly higher tissue concentrations of the minerals than the other treatments. Therefore, fertilization of haricot beans with Fe and Zn is important in the soils of the study sites especially for quality production.

Keywords: Fe concentration, Haricot bean, NPZnFe, Zn concentration.