Empirical Analysis of the Growth Response of Cassava Genotypes to Potassium Deficiency in South East Nigerian Soils

Potassium deficiency is a widespread but underrecognised soil fertility constraint in the intensively cultivated ultisols and oxisols of South East Nigeria, and characterising the differential sensitivity and tolerance of cassava genotypes to potassium stress provides important data for both variety recommendation and fertility management advisory. This study empirically analysed the growth and yield responses of eight cassava genotypes (four improved IITA varieties and four local varieties) to three potassium supply levels (0, 50, and 100 kg K2O ha-1) in Anambra State, South East Nigeria. A split-plot experiment with potassium rate as the main plot and genotype as the sub-plot was conducted at Ogbaru LGA over two seasons (2022 and 2023) with three replications. Plant height at 4 and 8 months, storage root fresh weight yield at 12 months, starch content, and leaf potassium concentration were measured. Results showed significant genotype x potassium rate interactions for storage root yield. Improved variety TMS 30555 showed the highest yield response to potassium (from 27.4 t ha-1 at 0 K to 42.1 t ha-1 at 100 kg K2O ha-1), while local variety Nwugo maintained comparatively stable yield across potassium rates, suggesting constitutive potassium acquisition efficiency. Leaf K below 1.2 percent was associated with visible chlorosis and reduced starch content. The study provides original genotype-specific potassium response data and recommends TMS 30555 cultivation should be accompanied by potassium fertilisation in K-deficient Anambra soils.

Keywords: cassava, potassium deficiency, genotype response, South East Nigeria, soil fertility