Sweet Potato Production with Organic Inputs from Mulches and Hedges in the Caribbean.

Alternatives to the use of agrochemicals in traditional farming practices are needed to safeguard the pristine environment of the Caribbean islands. Potentially useful plant species for on-farm production of organic inputs include Azadirachta indica A. Juss. (Neem) and Gliricidia sepium (Jacq.) Kunth ex Walp. (Gliricidia). These species are noted for pest repelling and nitrogen fixing properties, respectively, and can be useful for reducing farm use of inorganic pesticides and fertilizers.  Hedges and mulches of these species were tested for effects on soil properties, crop growth, pest damage levels and yield of sweet potato (Ipomoea batatas (L.) Lam.), an important crop for food security in the Region. Mulch material (10 t ha^-1 on average) was applied at planting and again after 12 weeks to sweet potato (Black Vine). In another study, two sweet potato varieties (Black Vine and Lovers Name) were compared at varying distances from a 0.5m tall hedge of Neem and Gliricidia plants alternating with 0.25m spacing. Both studies were conducted without inorganic fertilizer inputs, and with and without the application of an inorganic pesticide (Actara). Sweet potato yields (at 24 weeks) increased with the use of Neem or Gliricidia mulch with Gliricidia having a greater effect. However, yields declined when the two materials were combined in a 1:1 ratio at the same total mulch application rate.  Organic nitrogen inputs and possible nitrification inhibitor effects of Neem can alter nutrient ratios in the soil at the time of tuberization, which can influence yield. In the second study, yield was reduced by proximity to the Neem/Gliricidia hedge for the ‘Black Vine’ but not for the ‘Lovers Name’ variety for which tuberization occurs earlier. Mulches and hedges of Neem and Gliricidia can be useful components of ecological approaches for sweet potato production in the Region.