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Potato production in the Tri-County Agricultural Area of northeast Florida accounts for nearly half of the state's $120 M, 18-K hectare annual crop. Concern over nitrate movement into watersheds from potato production have stimulated research into alternative fertilizer sources and practices. This study evaluated the potential of several controlled-release fertilizer (CRF) products to release nutrients over a 100-day growing season under field temperature and precipitation conditions. In 2003 and 2004, 6 and 3 CRF products were evaluated, respectively. Meshbags containing 3 g of product mixed with 200 g of soil were buried 15 cm below the top of the potato row. Meshbags were removed at 2-week intervals. Samples were dried and sieved to remove soil. Fertilizer prills were ground and mixed with DI water to dissolve residual fertilizer. Samples were analyzed for total N by the Dumas (combustion) method (2003) or for TKN (2004). In 2003, initial release (after 20 days) ranged from 23% to 85% for the six products. In 2004, initial release (after 9 days) ranged from 34% to 65% for the three products. In 2003, total N release from CRF prills after 104 days ranged from 72% to 99%. In 2004, total N release from samples ranged from 79% to 92% release after 91 days. The shape of the release curve described some release patterns comparable to water-soluble fertilizers while others exhibited sustained-release properties. If release characteristics are designed to match potato plant uptake requirements in time and quantity, CRF products may be used to reduce off-site N movement while maintaining potato production.

Weed management is a major constraint of organic vegetable production and perennial weeds such as purple nutsedge (Cyperus rotundus) are particularly difficult to control. A study was initiated in 2005 to determine how summer fallow techniques impact purple nutsedge population density, tuber number and tuber viability; and to evaluate the impact of the treatments on the yields of two fall crops differing in canopy size and rate of development. Clean fallow treatments accomplished with weekly tillage or weekly flaming were conducted for 12 weeks. Two sets of summer cover crop treatments of sunn hemp (Crotalaria juncea) were established by broadcasting 40 lb of seed per acre and were undercut at 13 weeks after seeding. Cover crop residue was either incorporated before transplanting or retained on the surface as mulch for the fall crops of lettuce and broccoli. Soil solarization was initiated on 2 July and the transparent solarization film was maintained in place until mid-October. A weedy fallow treatment was included as a control, which was tilled before establishing the fall crops. Before the initiation of the summer fallow treatments, no difference in viable tubers or nutsedge shoot density was observed. After fallow, flaming had the highest number of viable tubers, with all other treatments similar to the weedy control. Nutsedge shoot density was suppressed by all fallow treatments to lower levels than with the weedy control, but solarization was the least effective. Leaf-cutting insects eliminated the crops in the sunn hemp mulch treatment within days of being transplanted. Lettuce stands with all other treatments were similar and greater than with the weedy control. Highest broccoli stands were obtained with flaming, solarization, and tillage; but broccoli stand with incorporated sunn hemp was similar to the weedy control. Highest lettuce yields occurred with incorporated sunn hemp, solarization, and weekly tillage. However, lettuce yields with flaming and the weedy control did not differ statistically. Broccoli yields were greatest with flaming, solarization, and tillage. Broccoli development was delayed with the weedy control and incorporated sunn hemp treatments and no significant yield was obtained.