Observations on Cassava (Manihot esculenta Crantz) Root Yield and Soil Fertility under Different K - Sources

Abstract

The lingering problem of scarcity and high cost of synthetic fertilizers in Nigeria, following changes in Government policies on subsidy, procurement and distribution of inorganic fertilizers, has made inorganic fertilizers unaffordable by the resource – poor farmers, who, incidentally, are the chief food producers in Nigeria. Therefore, the need arises to critically evaluate the potential of certain organic wastes in maintaining and improving soil fertility and crop productivity. To partly meet this need, hence, this paper reports the results of a two – year trial, aimed at evaluating efficacy of different K sources in improving fertility of an Alfisol and performance of cassava (Manihot esculenta Crantz).The experiment was laid out in a randomized complete block design with three replicates. The different K sources included: Muriate of potash (MOP); cocoa pod ash (CPA); NPK (15 – 15 – 15); bone ash (BA) and control or check (C). The results obtained indicated existence of significant (P = 0.05) differences among the K sources with respect to their effects on nutrient status of an Alfisol and cassava root yield. At the end of 2012 cropping season, K sources resulted in significant increases in soil organic carbon (SOC) from 0.40 g kg^-1 for C to 0.47, 0.64, 0.51 and 0.59 g kg^-1 for MOP, CPA, NPK, and BA, respectively. Similarly, at the end of 2013 cropping season, K sources significantly increased SOC from 0.22 g kg^-1 for C to 0.40, 0.69, 0.45 and 0.63 g kg^-1 for the respective MOP, CPA, NPK, and BA. At the end of 2012 cropping season, K sources significantly increased total N from 0.20 g kg^-1 for C to 0.23, 0.46, 0.41 and 0.35 g kg^-1 for MOP, CPA, NPK, and BA, respectively.  At the end of 2013 cropping season, K sources significantly increased total N from 0.07 g kg^-1 for C to 0.10, 0.52, 0.37 and 0.43 g kg^-1 for MOP, CPA, NPK, and BA, respectively. Mean values of cassava root yield data across the two years of experimentation indicated that, K sources significantly increased cassava root yield from 4.52 t ha^-1 for C to 6.70, 8.69, 5.97 and 6.28 t ha^-1 for MOP, CPA, NPK, and BA, respectively.

Keywords. Cassava, fertility, observations, yield, sources.