Most countries in West Africa suffers from problems such as erosion, salinisation and
spreading deserts. Mali is one of the poorest countries in this area with a surface that mostly consists of desert and semi-desert. Agriculture is the most important occupation for the people but is unfortunately endangered by poor water supply and over exploited soils. The river Niger that flows through the country is an important source for irrigation. By building the Markala dam and creating the Office du Niger, one of the largest irrigation schemes in West Africa, it has been possible to raise the groundwater level and increase the irrigation capacity in the area. This has ameliorated the conditions for rice production resulting in increased yields.
Iron and zinc are both essential elements for plants and humans. Zinc deficiency is a
widespread problem in Sub-Saharan Africa. More than half of the soils in Mali are affected
and approximately 80% of the population is considered to have an insufficient zinc intake.
Zinc is the most critical micronutrient to rice growth and a zinc deficiency in rice cultivation causes reduced yields, some times to as much as 50%.
Iron toxicity is also a common problem in rice cultivation and zinc deficiency in rice is often linked to this phenomenon. Dissolved ferrous iron is taken up by the plant and accumulated in the leaves, especially at low pH and low oxygen levels. If the concentration of ferrous iron is high in the root zone iron plaques are formed, preventing the plant from taking up other nutrients such as Zn.
The aim of this study was to investigate how the zinc uptake in lowland rice is affected by different nutrient managements and intermittent irrigation. The project was carried out at Centre Régional de Recherche Agronomique (CRRA) in Sotuba, Mali. A pot experiment was set up with soils from Office du Niger using 6 different treatments and 3 replicates. Two differing soils were collected; one from the zone of Macina, rich in iron, and one from Kouroumari with less iron content. Both were deficient in zinc. The rice plants were grown for 21 days and then a visual observation were made. The soil and plant residues were analysed on zinc and iron content by extraction of DTPA and measuring the concentrations with AAS.
There were visual signs of zinc deficiency and iron toxicity in most plants. The plants being treated with intermittent irrigation and addition of extra nutrients were the strongest and most beautiful ones. It is difficult to do an interpretation of the results since the measured concentration...
