Vegetative Growth Responses of Castor (Ricinus communis) and Senna (Senna occidentalis) to Low Dose Zinc (Zn) Spiking of Agricultural Soil in Kano, Northern Nigeria

The aim of the research is to assess the viability of castor (Ricinus communis) and senna (Senna occidentalis) plants up to 90 days after planting (DAP) in agricultural soil spiked with different concentration of zinc in the screen house. Agricultural soil was collected from Bayero University Kano, at 11° 98ʹ 32.59″N; 8°42ʹ 43.97″E. Soil texture, pH, electrical conductivity (EC), organic carbon (OC), nitrogen (N), phosphorus (P) and exchangeable cations (K + , Ca + , Mg + and Na + ) were determined. Castor and senna were planted in soil spiked with 2 mg/kg, 4mg/kg and 8 mg/kg of zinc sulphate (ZnSO4) each. Control plants containing only  agricultural soil without spiking with zinc  were added and the set up replicated 4 times. Plant height, number of leaves and root length were assessed at 45 and 90 days after planting (DAP). The soil was sandy loam, slightly acidic, C, N, P and K+ had mean values of 0.41%, 0.33 mg/kg, 14.33 mg/kg and 0.39 cmol/kg respectively. There were significantly higher (p<0.05) mean values for height (16.85cm) and root length (17.35 cm) of control castor plants than those treated with zinc at 45 DAP.  At the termination of the experiment (90 DAP), senna plants in control had significantly higher mean values for height (29.5 cm) than all other treatments.  All concentrations of zinc used in this work did not seem to have much negative effects on the vegetative growth of both test plants.