Termites and agricultural production in the Sahel: from enemy to friend?

Termites are an important component of agroecosystems, particularly in developing countries where they are an alternative to high priced inputs. Given the major problems in the Sahel of soil crusting and nutrient depletion, this paper shows that termites associated with proper management techniques can play a vital role. Termites contribute to the rehabilitation of crusted soils, i.e. by opening up voids on the sealed surface leading to improved infiltration capacity, and consequently improved water availability. It is recommended, however, that participatory on-farm research should be carried out on how to increase the contribution of termites towards soil management and to reduce the harmful effects

The role of termites and mulch in the rehabilitation of crusted Sahelian soils

During recent decades Sahelian soils have gone through various forms of degradation, the most spectacular one being the extension of bare and crusted soils. Mulch, when placed on a crusted and bare soil, triggers termite activity within a few months. Many burrows are opened through the sealed surface of the soil due to the borrowing activity of the termites. Throughout the soil profile, macropores with irregular shapes and with different diameter sizes are created. As a result of changes in soil structure, other soil physical properties are also improved. Soil resistance to cone penetration is reduced from a critical to a suitable level for vegetation growth. Bulk density is decreased and soil hydraulic conductivity is greatly increased. Water infiltration and drainage are also greatly improved. The combination of the increase of porosity and infiltration and the cover effect of mulch results in an increase of soil water availability in the soil profile during the growing season. Termite activity enhances decomposition of the mulch and hence nutrient release in the soil. The change of soil characteristics due to termite activity was enough to create conditions necessary for natural vegetation development and crop production on previously degraded bare soils in the Sahelo-Soudanian zone of northern Burkina Faso

Le phosphore limite-t-il la production intensive du riz dans la plaine de Bagré au Burkina Faso ?

Le phosphore (P) est un élément important dans la nutrition minérale du riz et dans l’élaboration du rendement paddy. Des essais soustractifs ont été conduits en milieu paysan dans la plaine rizicole de Bagré au cours de trois campagnes successives pour évaluer l’effet de l’application de P sur le rendement paddy. La capacité nutritive du sol en phosphore a varié entre 7 et 15 kg P ha-1. L’application de P a augmenté l’efficacité physiologique interne de P qui a varié entre 211 et 290 kg paddy kg-1 P (moyenne 249 kg kg-1). L’efficacité agronomique de P a été de 33,7 kg paddy kg–1 de P appliqué. L’augmentation de rendement due à l’application de phosphore a été de 19%. En moyenne, 70% du phosphore total absorbé est contenu dans les grains. L’évolution du rendement paddy indique que P est le second facteur limitant dans la plaine de Bagré après l’azote. L’application de P_engrais à une dose moyenne de 30 kg P ha-1 était suffisante pour compenser les pertes dues aux exportations. Le phosphore limite la production de riz à Bagré mais son application comme engrais contribue à améliorer les rendements paddy et à compenser les pertes de P du système.Mots clés : Capacité nutritive des sols, rizières, efficacité d’utilisation de nutriments, bilan minéral

Micro-beam and pulsed laser beam techniques for the micro-fabrication of diamond surface and bulk structures

Micro-fabrication in diamond is involved in a wide set of emerging technologies, exploiting the exceptional characteristics of diamond for application in bio-physics, photonics, radiation detection. Micro ion-beam irradiation and pulsed laser irradiation are complementary techniques, which permit the implementation of complex geometries, by modification and functionalization of surface and/or bulk material, modifying the optical, electrical and mechanical characteristics of the material. In this article we summarize the work done in Florence (Italy) concerning ion beam and pulsed laser beam micro-fabrication in diamond.Comment: 14 pages, 5 figure

Towards truly simultaneous PIXE and RBS analysis of layered objects in cultural heritage

For a long time, RBS and PIXE techniques have been used in the field of cultural heritage. Although the complementarity of both techniques has long been acknowledged, its full potential has not been yet developed due to the lack of general purpose software tools for analysing the data from both techniques in a coherent way. In this work we provide an example of how the recent addition of PIXE to the set of techniques supported by the DataFurnace code can significantly change this situation. We present a case in which a non homogeneous sample (an oxidized metal from a photographic plate -heliography- made by Niepce in 1827) is analysed using RBS and PIXE in a straightforward and powerful way that can only be performed with a code that treats both techniques simultaneously as a part of one single and coherent analysis. The optimization capabilities of DataFurnace, allowed us to obtain the composition profiles for these samples in a very simple way.Comment: 9 pages, 3 figure

Organic resources and earthworms affect phosphorus availability to sorghum after phosphate rock addition in semi-arid West Africa

A field experiment was laid out in Burkina Faso (West Africa) on an Eutric Cambisol to investigate the interaction of organic resource quality and phosphate rock on crop yield and to assess the contribution of earthworms (Millsonia inermis Michaelsen) to P availability after phosphate rock application. Organic resources of different quality were applied at a dose equivalent to 40 kg N ha¿1 with or without phosphate rock from Kodjari (Burkina Faso) at a dose equivalent to 25 kg P ha¿1, and were compared with control and single phosphate rock treatments in a factorial complete block design with four replicates. Sorghum (Sorghum bicolor L. Moench) variety SARIASSO 14 was grown. Sheep dung had the highest impact on earthworm casting intensity followed by maize straw. Combining organic resources with phosphate rock reduced earthworm casting activities compared to a single application of organic resources or phosphate rock. Addition of phosphate rock to maize straw reduced P availability in earthworm casts whereas combining sheep dung or compost with phosphate rock increased P availability. The contribution of earthworms to Kodjari phosphate rock solubilisation mainly occurred through their casts, as the available P content of casts was 4 times higher than that of the surrounding soi

Fertiliser requirements for balanced nutrition of cassava across eight locations in West Africa

Insufficient and unbalanced fertiliser use widens cassava yield gaps. We assessed the spatial variability of optimal fertiliser requirements of cassava for enhanced nutrient use efficiency and increased yield using the balanced nutrition approach of the QUEFTS model. Two datasets comprised of five fertiliser experiments conducted at eight locations across Southern Togo, Southern Ghana and Northern Ghana from 2007 to 2012 were used. The ratio of storage roots dry matter yield over the sum of available N, P and K expressed in crop nutrient equivalent from the soil and nutrient inputs was used as a proxy to estimate nutrient use efficiency. Nutrient use efficiencies of 20.5 and 31.7kg storage roots dry matter per kilo crop nutrient equivalent were achieved at balanced nutrition at harvest index (HI) values of 0.50 and 0.65, respectively. N, P and K supplies of 16.2, 2.7 and 11.5kg at an HI of 0.50, and 10.5, 1.9 and 8.4kg at an HI of 0.65 were required to produce 1000kg of storage roots dry matter. The corresponding optimal NPK supply ratios are 6.0-1.0-4.2 and 5.3-1.0-4.2. Nutrient use efficiencies decreased above yields of 77-93% of the maximum. Evaluation of the performance of blanket fertiliser rates recommended by national research services for cassava production resulted in average benefit:cost ratios of 2.4±0.9, which will be unattractive to many farmers compared to 3.8±1.1 for the balanced fertiliser rates. The indigenous soil supply of nutrients revealed that, at balanced nutrition, K was the most limiting nutrient to achieve storage roots yields up to 8Mg dry matter ha-1 at most sites, whereas N and P were needed at greater yields. Dry weight of storage roots measured on the control plots in our researcher managed experiment ranged from 5.6 to 12.2Mgha-1, and were larger than the average weight in farmers' fields in West Africa of 4Mgha-1. Substantial yield increase could be attained in the region with improved crop management and fertiliser requirements formulation on the basis of balanced nutrition.</p