MAGNESIUM STATUS OF THE SAVANNAH SOILS OF NIGERIA IN RELATION TO TOBACCO PRODUCTION

MAGNESIUM STATUS OF THE SAVANNAH SOILS OF NIGERIA IN RELATION TO TOBACCO PRODUCTION

Abstract:

Under a system of continuous cultivation in northern Nigeria, a number of nutrients which were hitherto considered adequately supplied by the soil are becoming deficient, one such nutrient is Mg. There is need to establish the various availability indices for the nutrient under the semi-arid savannah conditions. Six extraction procedures of analysis involving two extractants (Ammonium acetate and Calcium chloride) were used. The amounts of magnesium extracted by these various methods differed significantly. Increasing extraction time or the concentration of the extractant tended to increase the Mg extracted. Plant uptake of Mg correlated well with Mg extracted by all methods, though, repeated and single extraction with 1 N NH4 OAc appeared the most suitable. Magnesium status of the surface soils of different locations as assessed by the single extraction with ammonium acetate procedure showed that the savannah soils of northern Nigeria are generally low in Mg. The mean values of Mg of the Sudan savannah, Guinea savannah, and southern savannah zones were 0.54; 0.96 and 0,56 meq/ lOOg respectively. Regression analysis showed linear relationships between exchangeable Mg and soil CEC, clay Ca, organic matter and silt in descending order indicating their relative importance in predicting Mg levels of these soils. Profile sampling in some tobacco growing areas revealed that Mg content increased with depth, the top soil containing the lowest amount. This distribution pattern is attributed to leaching and clay illuviation. High correlation existing between Mg content and each of organic matter and clay at all depths stresses their importance and the need to maintain the organic matter content of these soils. Magnesium content of field tobacco was considered low averaging about 0.26% and there was no correlation between plant and soil Mg which suggests that the latter may not be the only factor controlling Mg uptake under field condition. However, in the green house, Mg uptake was largely dependent upon soil Mg status. Application of Mg to generally acid scils, sandy to silty loam, low in organic matter, CEC, and nutrient status, particularly Mg and K improved the growth of tobacco plants and increased the leaf yield most especially at 24 kg Mg/ha, Magnesium content of leaves was increased but that of calcium, potassium, nicotine, total nitrogen and reducing sugar were not significantly affected, though there was a tendency tof decrease of reducing sugar with Mg application. There was no interaction between Mg and K on the chemical components of tobacco leaves and yield within the range of application of both elements. The generally low level of plant – available Mg in the soils studied coupled with the significant response obtained to Mg application suggest that Mg deficiency may attain wide scale importance in the semi-arid savannah zone of Nigeria in no distant future

MAGNESIUM STATUS OF THE SAVANNAH SOILS OF NIGERIA IN RELATION TO TOBACCO PRODUCTION

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