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Title: Nutrient relations in teff [E.tef (Zucc.) Trotter] and the effect of vesicular/arbuscular mycorrhizae on mediating its elemental composition
Author: Mamo, Tekalign
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1984
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Part I of this thesis dealt with a review of literature on the teff crop, soil -plant relationships, and on the role of vesicular -arbuscular mycorrhizal (VAM) fungi in plant nutrition. Part II was composed of the actual experimental studies, which included the experimental methods, soil physical and chemical characteristics, and growth response of teff plant to N and P applications, micronutrient additions, liming, and VAM fungal inoculations. Chemical and physical examination of the two Ethiopian teff growing soils showed that the light soil was generally more fertile than the black soil. A third Ethiopian saline-sodic soil was poor in its structure due to its excess Na content; Na has a dispersing effect and aggregation of soil particles is prevented. By studying the growth and shoot elemental composition of the plants when grown on the two soils receiving increasing levels of N, it was found that growth was initially slow but increased exponentially at later stages while nutrient offtake followed an opposite trend. Growth and nutrient offtake were greater on the light soil, but the offtake of both macro and micronutrients was greater between 35-52 days after emergence at all N levels and it followed the same trend on both soils. In sand solution culture studies, it was revealed that Fe and Mn. antagonisms existed in the teff plant. An increase in the concentration of one of these elements in solutions resulted in a decrease of the other in the plant. A comparison of Fe sources revealed that Fe was 2+ absorbed more by the plant either when it was supplied as an Fe form 3+ or when it was given as a chelated Fe as compared to the Fe form. In a separate study, it was found that Fe absorption by the plant decreased while Mn absorption increased with increase in pH of the nutrient solution. An attempt was also made to find the effect of P fertilization on the micronutrient status of teff plants and soils. In an incubation experiment, increased P addition to the two Ethiopian soils did not reduce DTPA-extractable Fe, Mn, Cu and Zn values for the two soils. On the other hand, reduced utilization of these elements by teff plants was observed due to increased P levels in the nutrient solution or in two soils, suggesting that the effect of P could have been physiological. Investigations on the role of VAM fungi on the growth and herbage quality of teff plants was carried out. Fungal root colonization and increased growth and nutrient offtake were observed with inoculation by G. fasciculatum (E3) of the two Ethiopian soils, but the effect did not show on the third saline-sodic soil. In an experiment in which both G. macrocarpus and G. mosseae were introduced in to an acid soil, limed to different pH levels, it was found that fungal root colonization and plant growth were increased by liming and fungal inoculation. Plants could not grow on the unlimed pots in the absence of both fungi. Unlike the mycorrhizal treatment, liming reduced the shoot micronutrient concentration. Both fungi were similar in their effect. The effect of increased P application on VAM fungal activity was also studied. Application at the rate of 150 mug P/g to a soil limed to a pH of 6.0 depressed both fungal root colonization by G. fasciculatum (E3) and shoot micronutrient concentration, especially of Cu and Zn, while mycorrhizal treatment increased the concentration of these elements. P application at the rate of 50 mug P/g brought little or no change on both fungal root colonization and shoot micronutrient concentration. In a separate experiment in which G. mosseae and G. macrocarpus were introduced to the acid soil, limed to a pH of 6.0 and microelements applied at a rate of 0 to 5 mug/g Cu and Zn and 0 to 10 mug/g Fe and Mn, no metal-induced reduction in root fungal colonization was observed, but P tended to decrease with increased metal load. Only Cu and Zn were increased by mycorrhizal treatment (both fungi gave similar results) while the concentration of the four elements increased in shoots with their increased concentration in the soil. It is suggested that results of growth studies in a controlled environment should be interpreted with caution when comparing with similar experiments on the field where growth conditions will be different.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available