Integrated Nutrient Management: Concepts and Experience from Sub-Saharan Africa

In Africa, 28 percent of its landmass, 874 Mha, is potentially suitable for agricultural production. Of the potentially suitable agricultural land, 34 percent comprises arid and semiarid lands (ASAL) that are too dry for rainfed agriculture. The semiarid regions have a shortened length of growing period (75-129 days) compared to the subhumid (180-269 days), and the humid (>270 days) zones. The dynamics of agroecosystems show that the farming systems practiced have gone through diverse changes from traditional shifting farming systems to permanent and intensified arable and mixed farming systems. The changes are coping strategies to respond to the environment, and its changing biophysical and socioeconomic circumstances..

Sustainable intensification of crop– livestock systems through manure management in eastern and western Africa: Lessons learned and emerging research opportunities

In the mixed farming systems that characterise the semi-arid zones of eastern and western Africa, low rural incomes, the high cost of fertilisers, inappropriate public policies and infrastructural constraints prevent the widespread use of inorganic fertilisers. As population pressure increases and fallow cycles are shortened, such organic sources of plant nutrients as manure, crop residues and compost remain the principal sources of nutrients for soil fertility maintenance and crop production. In this paper, the effect of manure on soil productivity and ecosystem functions and services is discussed. This is followed by highlights of the management practices required to increase manure use efficiency. We end with a discussion of emerging new research opportunities in soil fertility management to enhance crop–livestock integration. Although the application of manure alone produces a significant response, it is not a complete alternative to mineral fertilisers. In most cases the use of manure is part of an internal flow of nutrients within the farm and does not add nutrients from outside the farm. Furthermore, the quantities available are inadequate to meet nutrient demand on large areas. Research highlights have shown that efficiency is enhanced by different management practices including the timing and methods of manure application, its sources and integrated nutrient management. Research opportunities include analysing and understanding the ecosystem functions and services of manure use, the establishment of fertiliser equivalency for different manure sources, the assessment of the best ratios of organic and inorganic plant nutrient combinations, the crop–livestock trade-offs required to solve conflicting demands for feed and soil conservation and the use of legumes to enhance soil fertility and for animal feed. The establishment of decision support system guides and assessment of the economic viability of manure-based technologies in farmer-focused research are presented as powerful management tools intended to maximise output while preserving the environment in the mixed farming systems of the semi-arid zones

Effects of Acacia seyal and biochar on soil properties and sorghum yield in agroforestry systems in South Sudan

We studied the effects of Acacia seyal Del. intercropping and biochar soil amendment on soil physico-chemical properties and sorghum (Sorghum bicolor L.) yields in a two-year field experiment conducted on a silt loam site near Renk in South Sudan. A split-plot design with three replications was used. The main factor was tree-cropping system (dense acacia + sorghum, scattered acacia + sorghum, and sole sorghum) and biochar (0 and 10 Mg ha(-1)) was the subplot factor. The two acacia systems had lower soil pH, N and higher C/N ratios compared to the sole sorghum system. Biochar significantly increased soil C, exchangeable K+ contents, field capacity and available water content, but reduced soil exchangeable Ca2+ and effective CEC, and had no effect on soil pH. Acacia intercropping significantly reduced sorghum grain yields while biochar had no significant effect on sorghum yields. The land equivalent ratio (LER) for sorghum yield was 0.3 for both acacia systems in 2011, with or without biochar, but increased in 2012 to 0.6 for the scattered acacia system when combined with biochar. The reduction in sorghum yields by the A. seyal trees was probably due to a combination of competition for water and nutrients and shading. The lack of a yield response to biochar maybe due to insufficient time or too low a dosage. Further research is needed to test for the effects of tree intercropping and biochar and their interactions on soil properties and crop yields in drylands.Peer reviewe

Biochar successfully replaces activated charcoal for in vitro culture of two white poplar clones reducing ethylene concentration

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