Soil Fertility Assessment of Semiarid Soils from Nigeria Cropped to Sorghum

The aim of this study is to characterize the fertility status of the Dingyadi soils from semiarid Northern Nigeria, by using different methods of extraction to assess the potential for soil available macro and micronutrients to the sorghum crop. The study also compared concentrations of extractable nutrients between extractants for ascertaining the possibility of using one method to quantify a variety of plant-available nutrients in soils. Surface (0-15 cm) and sub-surface (15-30 cm) soil samples were collected along a topo-sequence at Dingyadi Sokoto-Nigeria, where sorghum had been grown, to characterize the soil chemical and physical properties that can influence soil fertility for sorghum production. The topo-sequence consisted of valley floor (TLL1), middle (TUP2), and crest (TUP3) positions of the slope. At each position 60 concentrations of each plant nutrient were used for the comparisons.Soil extraction for nutrients was carried out at the Environmental Soil Physics laboratory, Soil and Water Sciences Department, University of Florida, while analysis of aliquots for the elements was carried out at the Southwest Florida Research and Education Center, Immokalee, Florida. The study was carried out over a period of eight months, in 2016-2017. Soil samples were extracted using different extraction methods (Mehlich-3, Bray-1, Ammonium acetate, and DI-Water). A soil to solution ratio of 1:1 was used across all extraction methods to facilitate comparison between methods. However, a test was carried out to examine the effect of soil to solution ratio of (1:10) on extractable macro nutrients using Mehlich3 for randomly selected soil samples across the topo-sequence. Soil samples were also analyzed for texture, pH, organic matter, and cation exchange capacity (CEC). All soil soils were sandy, low in organic matter content, and CEC.With respect to sorghum production, the soils had adequate nutrients (Mg, Ca, K, and P) and soil pH. All soil samples contained no exchangeable K. Mehlich3 extracted higher available P than Bray1 in TLL1, but equal amounts in TUP2 and TUP3. Good correlations exist between extracting methods for macro nutrients (Mg, Ca, K, and P). Bray1 method used for available P is not suitable for soils that have pH greater than 7 determined in water. Mehlich3 is more suitable for the semiarid soils of Northern Nigeria that are acidic or alkaline. The Mehlich3 method should be calibrated with yield response of crops to substitute for Bray1 available phosphorus. Also, Mehlich3 method could be used for the multi-nutrient test with a good correlation with other methods like ammonium acetate for exchangeable bases.