Influence of Plant Population and Harvest Date on Peanut (Arachis hypogaea) Yield and Aflatoxin Contamination

Establishing the optimum plant population and harvesting at optimum pod maturity are important in maximizing yield of peanut ( Arachis hypogaea L.). The interaction of these two practices have not been documented in Malawi with respect to both yield and aflatoxin contamination in peanut. Research was conducted in Malawi at Mpatsanjoka farm in Salima district during the 2015-2016 and 2016-2017 growing cycles to determine interactions of plant population and harvest date on peanut yield and aflatoxin concentration in peanut at harvest with the cultivar CG7.  Peanut was seeded in raised beds spaced 75-cm apart with three different planting patterns to establish three final plant populations. A single row planting pattern consisted of one row of peanut on each center with seed spaced 15-cm apart was used to plant seed at a density of 89,000 seed/ha (referred to as the low plant seeding rate).  A twin row planting pattern included two rows of peanut spaced at 25 cm apart with 15 cm between seeds was used to plant seed at a density of 178,000 seed/ha (referred to as the medium plant population). A triple row planting pattern consisted of three rows of peanut spaced 25 cm apart with 7 cm between seeds was used to plant seed at a density of 278,000 seed/ha (referred to as the high density). Peanut for seeding density was dug 10 days before physiological maturity of pods, at physiological maturity, and at 4 and 6 weeks after physiological maturity. Pod yield increased as seeding rate and subsequent plant population increased but decreased as harvesting was delayed past physiological maturity. Yield of peanut with the highest plant population exceeded that of low and medium populations; yield of the medium plant population was greater that the low population in one of two years. Aflatoxin concentration at harvest was not affected by plant population but increased as harvest was delayed past physiological maturity. Harvesting peanut 10 d prior to physiological maturity did not affect grain yield or aflatoxin contamination compared with harvesting at optimum maturity.