ORGANIC AND SYNTHETIC MULCHES AFFECT YIELD OF BASIL UNDER DRIP IRRIGATION

Yields of most vegetable crops have been improved by the beneficial effects of drip irrigation and mulching. The use of these crop management techniques reduces water use, increases water-use efficiency and improves yield and quality of vegetable crops. These benefits are significant in the Virgin Islands where water is a major limiting resource in crop production. Field experiments were conducted in 1991 and 1993 to evaluate the effects of organic and synthetic mulches on yield of basil (Ocimum basilicum L.) under drip irrigation. Basil was grown in plots with organic (compost or straw) and synthetic (black plastic or black fabric) mulches. A no-mulch control plot was also included. All plots were dripirrigated to maintain soil moisture tension at 30 kPa. In 1991, total plant fresh and leaf fresh and dry weights were highest in the compost mulch treatment. Fresh and dry basil yields in plots with black plastic mulch were almost identical with those in compost mulch, but did not differ from other treatments. In 1993, total plant and leaf fresh yields from plots under organic mulches were significantly higher than yields from plots with synthetic mulches. All mulch treatments resulted in lower water use, increased water use efficiency and lower weed population than the control (bare soil). Organic mulches reduced surface soil temperature by 2 to 5 °C. This study demonstrates the potential of organic mulches for improving production of herbs in the Virgin Islands