No abstract

A field experiment was conducted to assess the effect of the combined use of farmyard manure and inorganic fertilizer on the growth and yield of sorghum and on soil chemical properties in a semi-arid area in northeastern Ethiopia. Twelve treatments comprising factorial combinations of four levels of farmyard manure (0, 5, 10, and 15 t ha −1 ) and three levels of inorganic fertilizers (0%, 50%, and 100% of the recommended rate) were compared in a randomized complete block design with three replications over a period of six years. The results revealed significant improvements in the growth and yield of sorghum due to the main and interaction effects of farmyard manure and inorganic fertilizer application. The combined application of farmyard manure and inorganic fertilizers increased post-anthesis dry-matter production by 147%-390% and grain yield by 14%-36%. The main effects of farmyard manure and inorganic fertilizers increased stover yield by 8%-21% and 14%-21%, respectively. Farmyard manure application increased total nitrogen (N) uptake by 21%-36%, grain protein yield by 8%-11%, and grain protein concentration by 20%-29%. Application of farmyard manure along with 50% of the recommended inorganic fertilizer rate resulted in a grain yield equivalent to, or greater than that for 100% of the recommended inorganic fertilizer rate, thus effecting a 50% savings of inorganic N and phosphorus (P) fertilizer. Application of 5, 10, and 15 t farmyard manure ha −1 along with 100% of the recommended fertilizer rate and 5, 10, and 15 t farmyard manure ha −1 along with 50% of the recommended fertilizer rate can be recommended for farmers who can and cannot afford to buy inorganic fertilizers, respectively.

Morphological and anatomical studies demonstrated the root formation characteristics of sweet potato (Ipomoea batatas (L.) Lam.). In this study, the presence and importance of preformed root primordia is recorded for the first time. On the vines, preformed root primordia are present in sets of 4–10 adjacent to the leaf bases, even those of young leaves. Macroscopically, the root tips of preformed root primordia protruding through the cortex and epidermis of the stems are prominent. These root primordia originate from the procambium on both sides of the leaf gap and produce adventitious roots, with pentarch, hexarch or septarch steles. Under normal conditions, storage roots will only develop from thick roots originating from undamaged preformed root primordia on the nodes of cuttings or nodes of newly formed vines, or from wound roots originating from the cut ends of stem or leaf cuttings. Terminal vine cuttings produce more tubers as a result of fewer damaged root primordia. Lateral roots originating from damaged preformed root primordia, or directly from the adventitious roots, exhibit tetrarch steles and develop into fibrous roots without the potential to develop into storage roots. This understanding of the origin, anatomy and morphology of sweet potato roots and the use of terminal vine cuttings with a higher percentage of undamaged root primordia, should improve production practices, which will contribute to improved crop establishment and increased yield.

Two similar field trials were carried out during 2003 in a hot tropical region of eastern Ethiopia to investigate the effect of leaf and soil applied paclobutrazol on the growth, dry matter production and assimilate partitioning in potato. A month after planting paclobutrazol was applied as a foliar spray or soil drench at rates of 0, 2, 3, and 4 kg a.i. paclobutrazol ha À1 . Plants were sampled during treatment application and subsequently 2, 4, 6 and 8 weeks after treatment application. The data was analyzed using standard growth analyses techniques. None of the growth parameters studied was affected by the method of paclobutrazol application. Paclobutrazol decreased leaf area index, crop growth rate, and total biomass production, and increased specific leaf weight, tuber growth rate, net assimilation rate, and partitioning coefficient of potato. At all harvesting stages, paclobutrazol reduced the partitioning of assimilate to the leaves, stems, and roots and stolons and increased allocation to the tubers. Although paclobutrazol decreased the total biomass production it improved tuber yield by partitioning more assimilates to the tubers. Paclobutrazol improved the productivity of potato under tropical conditions by redirecting assimilate allocation to the tubers.

Sub-Saharan Africa contains soils that have been cropped for generations. Consequently, their inherent fertility has been severely depleted. In such soils, net negative balances of nutrients are a common problem. The current soil nutrient depletion rates are contributing towards decreasing crop yields. The search for sustainable soil fertility replenishment techniques is, therefore, an urgent need. A key resource in this respect is animal manure. Such manure can increase and maintain soil fertility by providing N, P, K, S, Ca, Mg, Na and other trace elements such as Fe, Mn, Cu, Zn. It also improves the pH of acid soils and calcareous soils, increases soil organic matter content and cation exchange capacity, improves soil aggregate stability, soil macro-structure, infiltration, water holding capacity and erosion resistance. However, animal manure cannot meet crop nutrient demand over large areas, because of the limited quantities available and the relatively low nutrient content W. Bayu is affiliated with the