Impact of Planting Position and Planting Material on Root Yield of Cassava （Manihot esculenta Crantz）

Cassava （Manihot esculenta Crantz） is a perennial woody shrub with an edible root, which grows in tropical and subtropical areas of the world. In Africa, cassava provides a basic daily source of dietary energy. It plays an important role in food security and incomes of many rural households in the southern Ethiopia. However, information available on production practices of cassava for the region is insufficient. Hence, field experiment was conducted at Awassa Agricultural Research Center for two successive cropping seasons from 2004 to 2006 to investigate the response of cassava to planting position and planting material. The treatments used were three planting positions （slant, vertical and horizontal） and five planting materials （main stem top part, main stem middle part, main stem bottom part, branch stake top part and branch stake bottom part） were combined in factorial arrangement and laid out in randomized complete block design with three replications. The result revealed that root yield was significantly （P 〈 0.05） affected by the interaction effects of the planting position and planting material. The highest yield （25.2 ton ha^-1） was obtained from the main stem top part planted in slant position whereas the least yield （6.5 ton ha^-1） was obtained from main stem bottom part planted in horizontal position. Based on the findings of this study, areas like Awassa with moderate rainfall slant and vertical planting of main stem top and middle parts could be used as planting material.

Dry Matter Partitioning, Nodulation and Seed Traits of Medium and Late Maturing Soybean Varieties as Affected by Planting Pattern and Plant Density

An experiment was conducted on Fluvisols of Awassa for two consecutive years （2005-2006） to determine effects of planting pattern and plant density on dry matter accumulation, nodulation, protein and oil content in early and late maturing soybean varieties. Results indicated that Awassa-95 variety produced significantly higher （P 〈 0.05） number of nodules/plant （NDN）, nodule dry matter （NDM） and leaf dry matter （LDM at R2 （mid flowering） stage of soybean growth than that of variety Belessa-95）. Similarly, variety Awassa-95 （45%） produced significantly higher protein content than variety Belessa-95 （40%）. However, variety Belessa-95 accumulated significantly higher （P 〈 0.01） dry matter in straw, grain and total biomass at R7 （physiological maturity） stage of soybean growth than variety Awassa-95. Similarly, oil content of variety Belessa-95 （18.1%） was significantly （P 〈 0.05） higher than that of variety Awassa-95 （15.9%）. Equidistant rows produced significantly higher （P 〈 0.05） NDM than either rectangular or paired rows. Moreover, soybean plants grown in both rectangular and equidistant rows produced significantly higher （P 〈 0.01） straw dry matter than those grown in paired rows; but, grain dry matter/plant （GDM） was significantly higher （P 〈 0.01） paired and rectangular rows compared to equidistant rows. Plant density also affected the per plant GDM production as it was significantly higher （P 〈 0.01） in 20 and 30 plants/m2 than higher plant densities （40 and 50 plants/m2）. However, dry matter and yield components had strong negative association with protein content. In fact, strong positive correlation （R 〉 0.600） occurred between grain yield and its components with dry matter components at R2 （stem dry matter （SDM）, leaf dry matter （LDM） and stem ＋ nodule ＋ leaf dry matter together known as TDM） and straw dry matter at R7 in both varieties. This study depicted that soybean plants that produce higher dry matter components at R2 would probably produce more straw dry matter, greater grain yield components and higher grain yield dry matter at later stages.

Ultra-fast Maize （Zea mays L.） Hybrid Growth Response to Plant Population Density

Current arable land and increasing food demand necessitates the practice of double and multiple cropping systems with inclusion of ultra-fast maize hybrids, which are characterized by smaller size, fewer leaves per plant, lower leaf area and fewer self-shading problems, under irrigation. In this context, a field experiment was conducted for two successive cropping seasons 2008/2009 to 2009/2010 at Kenilworth Experimental Station to evaluate the effect of row spacings and plant density on growth. Three row spacing （0.225, 0.45 and 0.90 m） and five plant densities （5, 7.5, 10, 12.5 and 15 plants m^-2） were used. Treatments were combined in a factorial combination and laid out in a completely randomized design with replications consisting of five single plants randomly selected from each treatment for destructive sampling. Growth factors reacted differently to row spacing by plant density. At crop establishment, growth indicators were not significantly affected by either main effects or a combination thereof. However, at the end of the vegetative phase, almost all growth indicators reached a maximum and were significantly affected by treatment interactions. Growth analysis showed that there was an interaction effect of row spacing by plant density on plant height, dry matter （DM） accumulation, leaf area index （LAI）, crop growth rate （CGR） and net assimilation rate （NAR） of maize. Therefore, the current investigation demonstrated that a row spacing of 0.45 m or 0.90 m with a plant density of 10 plants m^-2 was optimum for the selected ultra-fast maize hybrid under irrigation.