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Kwame Nkrumah University of Science and Technology (2015)

Integration of remote sensing and geographic information system in soil fertiliy management in Mali

Djenebe, Dembele

Titre : Integration of remote sensing and geographic information system in soil fertiliy management in Mali

Auteur : Djenebe, Dembele

Université de soutenance : Kwame Nkrumah University of Science and Technology

Grade : Doctor of Philosophy in Soil Science, 2015

Résumé
A study was carried out using remote sensing and GIS to support decision making for appropriate land management practices aimed at improving the soil fertility status as well as millet and sorghum yield on the acid soils at Siguidolo in Mali. Aster image was used to identify elevation levels. Landsat image and visual interpretation were used to delineate soil units and to perform stratified random sampling. Quick bird image was utilized to assess vegetation concentration with normalized difference vegetation index (NDVI). On-site field measurements and surveys were carried out using GPS for ground verification and soil sampling. Laboratory analysis of soil samples was performed to generate values for mapping the spatial distribution of soil clay, sand and silt content as well as soil pH, C, N, P and K content using ArcGIS. Soil textural triangle was used to identify the soil textural classes. Twenty five soils units were delineated comprising loam (78.21 ha), loamy sand (68.99 ha) and sandy loam (689.06 ha). The pH of the soils ranged from moderately acid (5.5-6.1) to very strongly acid (4.7-5.1). The organic carbon and NPK content of the soils were very low. Soil fertility was therefore very low. The vegetation cover consisted of bare soil (278.26 ha), grassland with scattered trees (451.1 ha) and woodland with grass cover (148.93 ha). The cropping system was mainly cereal-based cultivated either sole or intercrop. Continuous cereal production is predominant but legume-cereal rotation has significantly increased over the three year period of 2011 to 2013. To facilitate the recommendation of improved land management for the Siguidolo area, a factorial experiment comprising two tillage practices (ridge and hoe tillage) and five soil amendments (No amendment ; sole Profeba ; Profeba + Urea ; Profeba + Urea + TPR ; and Profeba + Urea + Lime), arranged in a randomized complete block design with three replications was set up. The results were analysed by Analysis of variance using Lsd (0.05). Soil pH increased by 10-12% and 7.2 to 8.8% under ridge and hoe tillage respectively. The soil amendments generally increased the initial pH of 4.78 in the order of P4 > P3 > P2 > P1>P0 with a range of 4.80 to 5.56. Soil organic carbon was enhanced under ridge and hoe tillage with their respective increases being 18-23% and 11 to 22% over the control. Soil amendments also increased SOC in the same order as pH. Ridge and hoe tillage increased available phosphorus by 0.9 to 37% and 24% respectively under millet and sorghum. Available phosphorus as affected by soil amendments ranked as P3 > P4 > P2 > P1 > P0 under sorghum with a range of 1.65 to 4.01 mg kg-1. The range under millet was 1.39 to 2.47 mg kg-1. Tillage x soil amendment significantly (P<0.05) affected available P under sorghum in 2014 with P3 x R1 and P2 x R1 recorded higher values. There was a general decline in total N and exchangeable K. The grain yield of sorghum and millet was consistently higher under ridge tillage than hoe tillage. The Profeba compost + Urea and Profeba compost + Urea + TPR were the most promising soil amendments for sustainable crop production in the Siguidolo area.

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