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Conservation agriculture (CA) is often promoted as a set of cropping practices to reduce soil erosion and maintain soil fertility, while decreasing production costs and increasing crop yields. However, CA adoption is extremely low in Africa. Most investigations on constraints of its adoption leave out (i) the characteristics of CA as an emerging innovation and (ii) the wider institutional context. A comprehensive self-assessment tool for a systematic evaluation of factors influencing the CA adoption process at the field, farm and regional scale in a variety of regional contexts in Africa is still lacking. In an attempt to fill this knowledge gap, this article presents the motivation, development and testing of a Qualitative expert Assessment Tool for CA adoption in Africa (QAToCA) and its application. QAToCA is directed to regional experts, research teams and managers of development projects with a focus on CA, and allows them to assess their CA activities along a systematic, expert-based list of questions and criteria. Specifically, it aims at assessing the adoption potential of CA under the varied agro-ecological, socio-economic, cultural and institutional conditions of Africa as well as the specific supporting and hindering factors influencing this process. As an example, its application in Kenya and Tanzania identified a relatively high CA adoption potential. The following factors, however, are noticed to require further improvement: accessibility of markets for CA products and inputs; adaptation of machinery and seeds to the CA practices; introduction of quality implementation measures; and a renewed motivation (interest) among CA service providers. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In many parts of Central America long fallow periods are no longer feasible due to increasing land pressures. Farmers in northern Honduras have developed and diffused from farmer-to-farmer a maize cropping system using velvetbean (Mucuna spp.) as a short-term fallow. High total annual rainfall in a bimodal distribution is favorable to the system because it allows the completion of two rainfed cropping cycles annually. The first season is dedicated to the production of the mucuna crop and the second season is dedicated to maize. Soil pH and exchangeable Ca were not reduced during a 15-year period of continuous mucuna use. Soil organic matter, infiltration, and porosity increased with continuous mucuna use. Maize yields in fields with continuous rotation of mucuna were on average double those obtained without mucuna. The mucuna system was more profitable than the existing alternative bush-fallow system due to higher returns to land and labor resulting from higher yields, lower weeding and land preparation costs, and reduced risk of drought stress. The relative profitability of the mucuna system was also enhanced by seasonally high maize prices during the second season when maize is harvested in the mucuna system. Relativelyeasy access to land through inexpensive land ownership and land rental markets has made it possible for even small-scale farmers to dedicate land to the mucuna system. Land-use intensity is increasing in the region, however, as land is converted to pastures for cattle production. The opportunity costs of keeping land in the mucuna system, while also accessing land for first-season maize and other crops, are also increasing. These experiences remind us that a viable livelihood is the primary factor in farmers' decision making about adoption particular components of farming systems. [ABSTRACT FROM AUTHOR]

Abstract: Smallholder farmers in semi-arid Africa are in an increasingly vulnerable position due to the direct and indirect effects of climate change, demographic pressure and resource degradation. Conservation agriculture (CA) is promoted as an alternative to restore soil productivity through increased water and nutrient use efficiencies in these regions. However, adoption of CA is low due to a number of technical reasons, but fundamentally due to the fact that CA has been often promoted as a package, without proper adaptation to local circumstances. Farmers engagement in designing and implementing locally suited CA practices, as part of a long term strategy of soil rehabilitation is the core approach followed by the ABACO initiative, which brings together scientists and practitioners from West, East and Southern Africa coordinated through the African Conservation Tillage Network (www.act-africa.org). ABACO relies on agro-ecologically intensive measures for soil rehabilitation and increased water productivity in semi-arid regions, implemented, tested and disseminated through local co-innovation platforms. Rather than using rigid definitions of CA approaches that might not work in all sites, ABACO proposes to explore best engagement approaches for different sites. Simulation modelling is used as a support of long-term cross scale tradeoffs analysis from field to farms and territories, in order to inform effective policy-making. Preliminary results form the field are used here to illustrate and discuss the principles of ABACO, which may apply as well to regions other than semi-arid Africa. [Copyright &y& Elsevier]

Despite the reported benefits of conservation agriculture (CA), its wider up-scaling in Sub-Saharan Africa (SSA) has remained fairly limited. This paper shows how a newly developed qualitative expert assessment approach for CA adoption (QAToCA) was applied to determine its adoption potential in SSA. CA adoption potential is not a predictor of observed adoption rates. Instead, our aim was to systematically check relevant factors that may be influencing its adoption. QAToCA delivers an assessment of how suitable conditions "and thus the likelihood for CA adoption" are. Results show that the high CA adoption potentials exhibited by the Malawi and Zambia case relate mostly to positive institutional factors. On the other hand, the low adoption potential of the Zimbabwe case, in spite of observed higher estimates, is attributed mainly to unstable and less secured market conditions for CA. In the case of Southern Burkina Faso, the potential for CA adoption is determined to be high, and this assessment deviates from lower observed figures. This is attributed mainly to strong competition of CA and livestock for residues in this region. Lastly, the high adoption potential found in Northern Burkina Faso is explained mainly by the fact that farmers here have no alternative other than to adopt the locally adapted CA system-Zaï farming. Results of this assessment should help promoters of CA in the given regions to reflect on their activities and to eventually adjust or redesign them based on a more explicit understanding of where problems and opportunities are found.

The muscarinic agonist carbachol stimulated phospholipase D (PLD) in rat submandibular gland (RSMG) ductal cells in a time and concentration-dependent manner. This effect was inhibited by chelation of extracellular calcium with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). PLD could also be activated by epinephrine and AlF(4)(-), two polyphosphoinositide-specific phospholipase C (PPI-PLC) activators, and by the phorbol ester o-tetradecanoylphorbol 13-acetate (TPA) which activates protein kinase C (PKC). Ionomycin and thapsigargin only slightly increased PLD activity. Ortho-vanadate, a tyrosine phosphatase inhibitor, also stimulated PLD activity. Both carbachol and o-vanadate increased the formation of inositol phosphates and the tyrosine phosphorylation of at least two proteins (55-60 and 120 kDa). Calphostin C (a PKC inhibitor), U73122 (a PPI-PLC inhibitor) and genistein (a tyrosine kinase inhibitor) blocked the activation of PLD, of PLC and the phosphorylation of tyrosyl residues in response to carbachol and vanadate. Taken together, these results suggest that rat submandibular gland ductal cells express a calcium-dependent PLD activity. This enzyme is regulated by carbachol via a PLC-PKC-tyrosine kinase pathway., (Copyright 2002 Elsevier Science Inc.)