STUDIES OF RHIZOBIUM INOCULATION AND FERTILIZER TREATMENT ON GROWTH AND PRODUCTION OF FABA BEAN (VICIA FABA) IN SOME 'YIELD~DEPLETED' AND 'YIELD SUSTAINED' REGIONS OF SEMIEN SHEWA

Abstract

The failure of faba bean pnx:iuction in some regions of Sl.'mim
Shewa necessitated a research for a possible explanation and solution to reverse the problem. Two regions with a failure in pulse production of faba bean for five to ten years Le.'yield-depleted' Molale and Mehal Meda, and two regions that are still capable of producing faba bean i.I', 'yield-sustained' Ankober and Keyt were sek>eted. Comparative assessments of their nutritional factors, rhizobial type, rhizobia I density, and inoculation and fertilizer treatments with respect to their soil types were undertaken. The soil analyses showed that 'yield-depleted' areas were generally characterized by a medium
to high concentration of nitrogen (0.1-0.2%), a low content of phosphorus (3--6 ppm) and potassium, a high concentration of calcium and magnesium, and a lower population density of rhizobia (1()1_102 g-I soil). The results also showed that shoot length,shoot dry matter, and nodule fresh weight were significantly affected (p=O.Ol) by soH type and different inoculation and fertilizer treatments. Although growth parameters, in general, were improved by different treatments, shoot dry matter and nitrogen contents were not significantly affected in 'yield-sustained' regions as compared to 'yieJddepleted' ones. The results also showed that the comparative symbiotic effectiveness of the indigenous strains and the type exotic' strain (reference strain) Tal 1397N was not different. It did not also show significant difference
on the above mentioned growth parameters with different treatments. This indicates that the indigenous strains are equally effective in nitrogen accumulation provided that the problems of other limiting nutritional factors can be alleviated in the soil. This suggests that combined inoculation and fertilizer treatments can improve growth and reverse production of pulses in 'yield depleted' regions of Semien Shewa.