EVALUATING THE MICRONUTRIENT FERTILITY OF NIGERIAʼS SEMIARID SAVANNA SOILS

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Abstract
Evaluation of plant-available zinc in 55 representative soils of the seasonally dry Nigerian savanna soils showed that both 0.1 N HCl-extractable and double-acid-extractable Zn were, in general, low, ranging from 0.54 to 4.14 ppm and 0.35 to 3.90 ppm, respectively. About 35 percent of the soils had less than 1 ppm HCl-extractable Zn. However, under greenhouse conditions, appreciable yield reduction was recorded on only five soils, each of which had less than 0.9 ppm available Zn. Zinc availability appeared to be a function of soil organic matter content, soil pH, and leaching intensity. The Sudano-Sahelian soils developed under relatively dry conditions and sparse vegetation are low in organic matter, but the effect of this is compensated for by the lower intensity of leaching. The favorable effect of the higher organic matter levels in the southern Guinea savanna is mitigated by increased leaching intensity and the coarse-textured nature of the soils. However, leaching is less, and the soil organic matter levels are relatively high in the northern Guinea savanna. This explains the relatively high amounts of available Zn in the soils from that zone.Zinc deficiency, although reported in only a few isolated areas at present, seems to pose an imminent soil fertility problem in these soils in the near future. The most likely problem area seems to be southern Guinea savanna Oxisols and Ultisols. Evaluation of plant-available zinc in 55 representative soils of the seasonally dry Nigerian savanna soils showed that both 0.1 N HCl-extractable and double-acid-extractable Zn were, in general, low, ranging from 0.54 to 4.14 ppm and 0.35 to 3.90 ppm, respectively. About 35 percent of the soils had less than 1 ppm HCl-extractable Zn. However, under greenhouse conditions, appreciable yield reduction was recorded on only five soils, each of which had less than 0.9 ppm available Zn. Zinc availability appeared to be a function of soil organic matter content, soil pH, and leaching intensity. The Sudano-Sahelian soils developed under relatively dry conditions and sparse vegetation are low in organic matter, but the effect of this is compensated for by the lower intensity of leaching. The favorable effect of the higher organic matter levels in the southern Guinea savanna is mitigated by increased leaching intensity and the coarse-textured nature of the soils. However, leaching is less, and the soil organic matter levels are relatively high in the northern Guinea savanna. This explains the relatively high amounts of available Zn in the soils from that zone. Zinc deficiency, although reported in only a few isolated areas at present, seems to pose an imminent soil fertility problem in these soils in the near future. The most likely problem area seems to be southern Guinea savanna Oxisols and Ultisols. © Williams & Wilkins 1983. All Rights Reserved.

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