Acidic soils limit the production potential of crops because of low availability of basic cations and excess of hydrogen (H+) and aluminium (Al3+) in exchangeable forms. In the western part of the country such as Assosa and Wellega, soil acidity is a well-known problem limiting crop productivity. A field study was conducted to assess the effects of lime, vermicompost and their combinations on selected soil physico-chemical properties and responses of soybean grown on acidic Nitisols of Assosa area during 2016 and 2017 main cropping seasons. Soil samples were collected from the experimental site before planting and from plots after harvesting. The collected samples were analysed following the standard methods for soil physico-chemical analysis. The treatments were factorial combinations of four levels of lime (0, 1.62, 3.62 and 4.90 t ha-1) and four levels of vermicompost (0, 1.50, 3.00 and 4.50 t ha-1). The results revealed that soil pH increased from 5.31 – 5.86 pH while exchangeable acidity decreased from 5.46 - 2.85 cmol (+) kg-1 with levels of lime and vermicompost (3.26 with 3 and 4.90 with 4.5) t ha-1 respectively, which resulted in improved soil physico-chemical properties. The combined application of lime and vermicompost also significantly improved the yield related parameters of soybean. The maximum grain yield (1.95t ha-1) was obtained from the combined application of 4.90 ton lime and 3.00 ton vermicompost ha-1 followed by combined application of 3.26 ton lime with 3.00 ton vermicompost ha-1 with non-significant variation. Therefore, the combined application of 3.26 ton lime and 3.00 ton vermicompost ha-1 is a promising alternative amendment for amelioration of acidic Nitisols of Assosa (Amba-12 Kebele) and other similar agro-ecologies for the improvement of soybean production.
Sorghum is an important cereal crop and occupies third place in production after Maize and Tef in Ethiopia. Striga hermonthica reduces sorghum yields by competing for water, nutrients, space, light and photosynthates with the host plants. Information on the influence of intercropping sorghum with legumes for management and control of striga in sorghum in the Assosa Zone is scanty. On farm experiments were they are conducted at three locations, for three years, to investigate the effect of eleven treatments (Intercrop ground nut with Sorghum 1:1 and Simultaneous planting, Intercrop ground nut with sorghum 1:1 and Relay planting, Intercrop ground nut with Sorghum 2:1 and Simultaneous planting, Intercrop ground nut with Sorghum 2:1 and Relay planting, Intercrop soybean with sorghum 1:1 and Simultaneous planting, Intercrop soybean with sorghum 1:1 and Relay planting, Intercrop soybean with sorghum 2:1 and Simultaneous planting, Intercrop soybean with sorghum 2:1 and Relay planting, Sole soybean, Sole Sorghum and Sole Ground nut.) and was laid out in a randomised complete block design (RCBD) with three replication. Significant influence on the grain yield of sorghum due to treatment application was recorded. During the all season, the sorghum/legume intercrop had the highest sorghum yield. The sorghum/Ground nut intercrop out yielded than the sorghum/soybean intercrop at all growing season. The gross income and Land equivalent ratio indicates greater economic benefit with this intercropping groundnut in 1:1 proportion and simultaneous planting than sole planting. As a result, intercropping groundnut in 1:1 proportion and simultaneous planting for the control striga is essential, ideal and useful to small-scale farmers, in order to achieve sustainable crop production.
Soil test based phosphorous (P) calibration study was conducted on Soybean on Nitisols of farmers' fields in Assosa Zone. The experiment was arranged in a randomized complete block design with six levels of phosphorous fertilizer (0, 5, 10, 15, 20 and 25 kg ha -1 ) with three replications. The results revealed substantial responses of Soybean to phosphorus fertilizer rates on plant height, pod numbers per plant and seed yield. Seed yield increased significantly from 1761 to 2300 kg ha -1 with increase in the level of P fertilizer from the control to 46 kg P ha -1 . The magnitude of increase in seed yield due to application of 46 kg P ha -1 was 30.6 % higher as compared to the control. Extractable soil P concentrations (Bray II, 0-20 cm depth) three weeks after planting significantly responded to P fertilizer rate. Correlations of relative yield with soil test phosphorous values showed that the critical soil P concentration and average phosphorous requirement factor (Pf) calculated from soil test phosphorous values of all treatments for the study area were 8.5 and 6.55 mg kg -1 , respectively.
The effects of seed rate and row spacing on yield and yield components of tef (Eragrostis tef) were studied on the Nitisols of Assosa, Benishangul-Gumuz Regional State. Three levels of seed rate (5, 10 and 15 kg ha -1 ) factorially combined with three rows spaces (15, 20, 25 cm) and an additional plot of broadcast of tef seed at 25 kg ha -1 as a standard check making a total of 10 treatments. They were laid out in a factorial RCBD with three replications. Significant influence on the grain yield of tef due to treatment application was recorded on trial locations. The maximum grain yield (1216.8 kg ha -1 ) was obtained from application of 10 kg seed per hectare and 25 cm spacing between rows. Grain yield highly significantly increased from 973.8 to 1216.8 kg ha -1 with decrease in the seed rate from the broadcast 25 to 10 kg ha -1 due to the fact that tef tillers, as there is enough space. 10 kg seed ha -1 with 25 cm spacing would be more suitable practices for attaining optimum grain yield for tef at the study area.
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