Toposequence effect on soil properties and suitability rating for selected crops in Northern Guinea Savanna, Nigeria

Abstract

A toposequence at Giwa, Kaduna State was studied with the aim of assessing the effect of topography on soil properties and suitability ratings for rainfed rice, cowpea, and tomato. Three slope positions namely, lower slope (LS), middle slope (MS) and upper slope (US) were delineated, and their properties were assessed. Results indicated that soils on all locations were very deep (167 – 192 cm) with occurrence of plinthite at subsurface of MS and US. Slope position of the soils was noted to influence morphological, physical and chemical properties. Content of silt and sand fractions, available water content and moisture retention at field capacity were all significantly influenced by slope. Melanization, braunification, plinthization and argilluviation were some pedogenetic process notable in the soils. Suitability studies revealed that 29.12% of the area was moderately suitable (S2) for rice cultivation with limitations of climate, soil physical property and fertility, while 70.88% of the area were marginally suitable (S3), with an additional limitation in wetness. For cowpea, 68.13% of the soils were S2 with limitations in fertility, while MS was highly suitable (S1). Tomato was rated S2 for the entire area with general limitations in climate and fertility. Suitability for rice increased down the slope from US, while that of cowpea and tomato increased along the slope from LS to US. This effect was attributed to distribution of nutrient and water, as preconditioned by topography. Management practice suggests the use of LS for rice, while MS and US may be rotated for cultivating tomato and cowpea.