Yield assessment and aflatoxin contamination in groundnut in Mozambique

Abstract

Groundnut (Arachis hypogaea L) is an important crop, both in subsistence and commercial agriculture in Mozambique. However, its underground nature of fruiting and its indeterminate growth habit makes it difficult to determine the time of maximum maturity of pods. This results into either harvesting the crop too early or too late, which in-turn results into reduced crop yields and exposes the crop to fungal invasion and subsequent aflatoxin contamination. The objectives of the study were therefore to evaluate the effect of (i) harvesting time on yield and yield components of groundnut and (ii) harvesting time and drying methods on aflatoxin contamination of the crop at two locations namely; Nampula Research Station (PAN) and Mapupulo Agricultural Research Center (CIAM) in Northern Mozambique. In order to assess the effect of harvesting time on yield and yield components of groundnut a randomized complete block design in a split plot arrangement was used. The varieties (ICGV- SM-99568, ICGV-SM-01514 and JL-24) were the main factor and three harvesting dates (10 days before physiological maturity, at physiological maturity and 10 days after physiological maturity) were the sub-plots. Results from the study showed that harvesting at physiological maturity resulted into higher groundnut yields (1390.22 Kg/ha) compared to harvesting 10 days before (927.3 Kg/ha) and 10 days after (938 Kg/ha) physiological maturity. Furthermore, yield losses ranging from (16-25 %) and (30-40 %) were incurred as a result of harvesting groundnut 10 days before and 10 days after physiological maturity respectively. Evaluation of the effect of harvesting time and drying method on aflatoxin contamination of groundnut involved experimental trials arranged in a randomized complete block design in a split-split plot arrangement with four replications. Three groundnut varieties (ICGV-SM- 99568, JL-24 and ICGV-SM-01514), were considered as main plots and two drying methods (A-frame and tarpaulin) and three harvesting dates (10 days before physiological maturity, at physiological maturity and 10 days after physiological maturity) as the sub-plots. Aflatoxin contamination of groundnut kernels was lower at physiological maturity (≤ 10) compared to harvesting 10 days before (≤ 15 ppb) and 10 days after (≥ 20 ppb). It was also observed from this study that both the A-frame and tarpaulin drying methods were effective in reducing groundnut kernel moisture to the recommended level of ≤ 7 % which is ideal to prevent growth of fungi including aflatoxigenic strains