Influence of Farming Systems on Aflatoxin Contamination of Groundnut Crops under Field Conditions in Zambia
Juliet Akello1, Mweshi Mukanga2, Henry Njapau3, Joseph Atehnkeng4, Joao Augusto5, Peter Cotty6, Ranajit Bandyopadhyay7
1International Institute of Tropical Agriculture (IITA), Zambia
Groundnut is one of Zambia's cash and food security crop, and yet it is highly susceptible to pre- and post-harvest aflatoxin contamination. Aflatoxins are carcinogenic, immune suppressant and growth retardant substances that often undermine improved nutritional health status and livelihoods of smallholder farmers in Africa. However, limited information exists on the effect of farming systems on aflatoxin occurrence in Zambian agricultural commodities. This study assessed, on-farm, the impact of agronomic practices on aflatoxin contamination of groundnut. Groundnut samples were collected from different agro-ecological zones of Zambia from the field at harvest and from local markets. Of the 300 analysed samples, the occurrence of aflatoxin was found to be very high with 53% of harvest and 98% of market samples testing positive for the contaminant. Total aflatoxin was noted to vary from 0.4-6,095 ppb (harvest samples) and 0.1-5,325 ppb (market samples). Mean aflatoxin contamination level in harvest samples (246ppb) was higher than the market samples (180 ppb). Contamination of harvest samples, however, was enhanced by the farming practices. The groundnut variety Chalimbana (438 ppb) and Kamulomo (454 ppb) appeared more susceptible than MGV5, MGV4 or Njute varieties (1.3-203 ppb). Timely planting at the onset of rains (mid-November to mid-December, 67 ppb) reduced aflatoxin contamination by over 5 times when compared to late planting (beyond 20 December, 396 ppb). Growing groundnut in a virgin land or after a fallow period supported less contamination levels (1.4-20 ppb) than when the crop was cultivated in a field where maize (202 ppb) or other legumes (247 ppb) were previously grown. Mono-cropping (311 ppb) doubled aflatoxin contamination in harvested groundnuts compared to those collected from intercropped fields (132 ppb). The present study confirms the role of good agronomic practices in reducing aflatoxin contamination of groundnut in the field. Farmers need to integrate variety selection with good agronomic practices if they are to consume and market healthy groundnut commodities.
Keywords: Aflatoxin, agronomic practices, groundnut, sub-Sahara Africa
Contact Address: Juliet Akello, International Institute of Tropical Agriculture (IITA), 32 Poplar Avenue Avondale, Lusaka, Zambia, e-mail: j.akellocgiar.org