Sowing Depths and Nut Sizes Effects on Seedling Emergence and Growth of Cashew (Anacardium occidentale L.)

Abstract

Damage on aerial cotyledons from emerging cashew (Anacardium occidentale L.) by rodents severely affects seedling establishment in the field. The objective of this study was to evaluate sowing depth of cashew as a possible means of reducing pest attack and damage to seedlings during establishment via in-situ sowing. The study was conducted under shade of Gliricidia sepium trees at the Cocoa Research Institute of Nigeria (CRIN) central nursery, using two nut sizes: jumbo ( ≥ 16 g) and medium (6 - 8 g) and five sowing depths: 5.0, 7.5, 10.0, 12.5 and 15.0 cm in 2005; 2.5, 5.0, 7.5, 10.0 and 12.5 in 2006. The treatments were arranged in a randomized complete block design (RCBD) with four replications. Data were collected on days to emergence, percentage emergence, position of cotyledons (above or below soil level), plant height, stem diameter and analyzed using ANOVA. Means were separated using least significant difference (LSD). Jumbo and medium nuts emerged at similar periods (22 and 21days respectively). Depth of sowing enhanced both the rate and total emergence. Nuts sown at 2.5 cm emerged 12 days earlier and 22% higher in emergence than those sown at 12.5 cm depth. The difference was significant (P =.05). Similarly, seedling emergence was earlier for cashew nut sown at 5.0 cm compared to those sown at 12.5 and 15.0 cm depths with significant (P = .05)  difference. Seedling emergence, growth and cotyledon concealment were in the order of 7.5 > 10.0 > 12.5 cm for the two nut sizes. The cashew seedling height and stem diameter were higher in jumbo-size nut seedlings than in medium-size with significant (P =.05) difference. Sowing at 7.5 cm soil depth gave the best performance in terms of seedling protection and growth. Jumbo nut size may be preferred by farmers to medium size in terms of initial seedling growth performance.