EFFECT OF FERTILISER AND STORAGE ON AFLATOXIN CONCENTRATION AND NUTRIENT COMPOSITION OF GROUNDNUT (Arachis hypogaea L.)

Abstract

Plant nutrient deficiency is a major limitation to crop production efficiency and nutritional quality, and a predisposing factor for infections. The study was aimed at determining the proximate composition and aflatoxin concentration levels in groundnuts cultivated using Yaralegume and Humate Green OK fertilisers at four (4) communities in the Lambusie-Karni District of the Upper West Region of Ghana. The experiment was laid and replicated thrice in a randomized complete block design (RCBD). Fluorometric and Proximate analyses were employed respectively in the measurement of aflatoxin concentration and proximate composition. The results indicated that moisture content, crude protein, crude fat, crude fibre, ash and carbohydrate contents ranged between (3.15- 4.16 %), (21.54- 28.54 %), (39.98- 47.78 %), (2.37- 10.24 %), (1.29- 3.18 %) and (13.79- 28.61 %) for fresh groundnuts and (3.46- 4.14 %), (25.13- 30.38 %), (44.67- 55.33 %), (3.16- 11.08 %), (1.59- 2.59 %) and (3. 36- 18.43 %) for stored groundnuts respectively. After storage, 83.33 %, 58.33 % and 66.67 % of the samples recorded increase in moisture and crude protein, fibre and ash content, and crude fat correspondingly. However, 91.67 % of the samples had reduced levels of carbohydrate after storage. All groundnut samples tested contained detectable concentrations of total aflatoxins (B1, B2, G1 and G2). Fresh and stored groundnuts contained aflatoxins in the range of 3.59- 13.21 ppb and 10.43- 93.43 ppb respectively indicating high concentrations after storage. Aflatoxin concentration in fresh groundnuts where fertiliser was not applied increased from 34.19-62.05 % after storage whilst it reduced significantly from 24.41-19.23 % and 37.40-18.72 % in fields where Yaralegume fertiliser only and Yaralegume + Green OK fertilisers were used. Two stored groundnut samples however recorded aflatoxin levels of 93.43 ppb and 52.92 ppb which were noted to be above Ghana Standards Authority maximum allowable limit of 20 ppb. Insignificant (p > 0.05) positive and negative correlations existed between aflatoxin concentration and parameters of proximate composition for both categories of groundnuts. Fertiliser application reduced pre-harvest and post-harvest aflatoxin concentration with no change in proximate composition of the groundnuts. Storage, however increased aflatoxin concentration with no significant change in proximate composition. The potential of reducing the concentration of aflatoxins in fresh and stored groundnuts cultivated using the Yaralegume fertiliser and the combination of Yaralegume and Humate Green OK fertilisers was observed and can be considered by farmers for use in groundnut cultivation especially in the study areas.