Indigenous knowledge systems and climate change management in Africa

Climate change presents a profound challenge to food security and sustainable development in Africa. Its negative impacts are likely to be greatest in the African region, which is already food insecure. In the face of global climate change and its emerging challenges and unknowns, it is essential that decision makers base policies on the best available knowledge. In recent years, the knowledge of local and indigenous people, often referred to as indigenous knowledge (IK) has been increasingly recognised as an important source of climate knowledge and adaptation strategies

Green manure in coffee systems in the region of Zona da Mata, Minas Gerais: characteristics and kinetics of carbon and nitrogen mineralization.

The use of green manure may contribute to reduce soil erosion and increase the soil organic matter content and N availability in coffee plantations in the Zona da Mata, State of Minas Gerais, in Southeastern Brazil. The potential of four legumes (A. pintoi, C. mucunoides, S. aterrimum and S. guianensis)to produce above-ground biomass, accumulate nutrients and mineralize N was studied in two coffee plantations of subsistence farmers under different climate conditions. The biomass production of C. mucunoides was influenced by the shade of the coffee plantation.C. mucunoides tended to mineralize more N than the other legumes due to the low polyphenol content and polyphenol/N ratio. In the first year, the crop establishment of A. pintoi in the area took longer than of the other legumes, resulting in lower biomass production and N2 fixation. In the long term, cellulose was the main factor controlling N mineralization. The biochemical characteristics, nutrient accumulation and biomass production of the legumes were greatly influenced by the altitude and position of the area relative to the sun

Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.

Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and(lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants

Soil fertility replenishment through agroforestry systems in two contrasting agro-ecological zones of Zimbabwe.

The main limiting nutrient in most communal areas of Zimbabwe is nitrogen (N). There is also deterioration of soil physical properties without continual addition of organic matter to the soil. Soil fertility replenishment through agroforestry technologies such as biomass transfer and improved fallows are discussed in terms of their potential to alleviate N limitations to increase maize yield. Various management practices to enhance the nutrient use efficiency on these systems are discussed. Areas of future resources are suggested. Transactions of the Zimbabwe Scientific Association Volume 72 (Supplement) 1998, pp. 31-4

Evaluation of Leucaena leucocephala leaf prunings as a source of nitrogen for maize

Prunings of leucaena [Leucaena leucocephala (Lam.) De Wit] have long been regarded as a useful alternative to N fertilizer, but N use efficiency by crops is often low. The potential exists to synchronise nutrient release with crop nutrient demand through variation in the rate and placement of prunings. A 2x2x3 factorial experiment was conducted to evaluate the potential of leaves of leucaena to supply N to maize (Zea mays L.) plants grown in pots of soil (Grossarenic Paleudult) under glasshouse conditions. Factors tested were two rates of application (3 and 6 Mg ha-1), two methods of placement (surface vs incorporation), and 3 levels of N fertilizer (0, 50, and 150 kg ha-1 equivalent of urea in solution form). Surface applied prunings significantly increased maize shoot dry weight with increasing levels of N fertilizer. Although incorporation of prunings increased maize shoot dry weight, the incorporated treatments did not show any significant response to N fertilizer, indicative of adequate N supply from prunings. Both shoot and total dry weight significantly increased with increasing rates of prunings applied. Nitrogen recovery was increased by applying prunings together with N fertilizer. There was a higher N recovery with incorporation compared to surface application. Prunings applied at a rate of 3 Mg ha-1 gave higher %N recovery than 6 Mg ha-1. At the final harvest date, application of 6 Mg ha-1 of prunings produced taller plants than 3 Mg ha-1.Les emondes de leucaena (Leucaena leucocephala (Lam.) De Wit) ont longtemps ete considerees comme une alternative aux engrais azotes, mais l'utilisation efficace de N par les plantes est souvent limitee. Il existe le potentiel synchroniser la liberation des substances nutritives avec la demande des nutritifs par une variation du nombre et du placement des emondes. Une experience factorielle (2x2x3) a ete effectuee pour evaluer le potentiel des feuilles de leucaena de fournir de lte aux plantes de mas (Zea mays L.) eleves en pots de terre (Grossarenic Paleudult) en conditions de serres. Les facteurs examines etaient les suivants: taux duplication (3 et 6 Mgha-1), deux methodes de placement (surface vs incorporation), et trois niveaux de fertilisation d'azote (0,50 et 150 kg ha-1) equivalent de en forme de solution. Les emondes appliquees la surface font augmenter d'une facon significative le poids sec des pousses de mas avec des niveaux plus eleves d'engrais azotes. L'incorporation des emondes augmente le poids sec des pousses de mas, mais il n pas de reponse significante avec les engrais azotes; ceci indique que sous cette forme duplication, les emondes fournissent de lazote d'une facon efficace. Le poids sec des pousses et le poids sec total augmentaient avec des taux plus eleves dndes. La recuperation dte augmentait par une application simultanee dndes et drais azote. La recuperation d'azote etait plus importante quand les emondes incorporees etaient comparees avec une application la surface. 3 Mg ha-1 dndes appliquees donnaient une plus grande recuperation (%) d'azote que 6 Mg ha-1. Au moment de la recolte, 6 Mg ha-1 demondes appliquees produisaient des plantes de plus hautes tailles que 3 Mgha-1

Management of organic matter in the tropics: Translating theory into practice

Inputs of organic materials play a central role in the productivity of many tropical farming systems by providing nutrients through decomposition and substrate for synthesis of soil organic matter (SOM). The organic inputs in many tropical farming systems such as crop residues, manures, and natural fallows are currently of low quality and insufficient quantity to maintain soil fertility hence there is need to find alternative or supplementary sources of nutrients. Knowledge gained over the past decade on the role of organic resource quality in influencing soil nutrient availability patterns (Synchrony Principle) and SOM maintenance (SOM Principle) provides a strong scientific basis on which to develop management tools. This scientific information must be linked with farmer knowledge and circumstances to provide a realistic approach to soil fertility and SOM management in the tropics. A decision tree has been developed for testing hypotheses about the resource quality parameters that affect nitrogen release patterns and rates. The decision tree is linked to an Organic Resource Database (ORD) with detailed information on the resource quality of agroforestry trees and leguminous cover crops providing a systematic means of selecting organic resources for soil fertility management. The decision tree has also been translated into a practical field guide for use with farmers in evaluating organic materials. The longer-term effects of organic inputs on SOM might also be addressed through the decision tree and database. It is generally believed that materials good for short-term soil fertility will not build or maintain SOM; if true then it is difficult to imagine practical means of maintaining SOM in the African context where short-term fertility issues will take precedence over longer-term maintenance of SOM