Effectiveness of Controlled-release Formulas in Strawberry Production in California, Poster Board #173

Strawberry is the second heavily produced crop in the central coast of California and its estimated value is $605 million according to the Monterey County Crop Report. Consequently, it is one of the contributing crops to the increase in nitrate contamination of groundwater. New stringent requirements of nitrate-N (NO₃–N) levels in soils and groundwater in California may be soon applied. It became important now more than ever to use fertilization practices that minimize leachate beyond the root zone while maintaining optimal strawberry yields. Among fertilization practices adopted by growers throughout California is the use of controlled-release formulas (CRF). Pre-plant CRF’s are expected to provide plant nutrients need efficiently, reduce contact between the transplanted daughter plants and the fertilizer to avoid any root damage, and potentially reduce nitrogen leaching. Field study conducted in the production season of 2009–10 and 2010–11 in Salinas Valley, CA, to evaluate yield in response to CRF’s fertilizers containing various rates of N, P, K and micronutrients in a commercial production scale. The study was designed in a randomized complete-block design with four replicates of each treatment. Nutrient levels were assessed in both soil and plants tissues. Strong positive correlation was found between soil and plant (NO₃–N) suggesting that most of (NO₃–N) was taken by plants.  At the end of the season, N (NO₃–N) levels were 8.9 ppm and 5.7 ppm from soil treated with growers’ standard supply of soluble N and soil treated with CRF’s, respectively. In midseason of 2010, yields were 1247 and 1091 (g/plant) from plants grown in plots treated with formulas 15–7–18 and 18–6–12, respectively; suggesting that high N rates did not necessarily provided higher yields. Additionally, in July 2010, marketable yield from plots fertilized with CRF 16–5–17 produced yield at a significantly higher rate than those fertilized with growers’ standards water soluble fertilizer, 31.9% compared to 23.1%. Pre-plant CRF’s can be promising soil fertilization practice that potentially reduces negative impact on the environment, reduces labor cost, and maintains optimal levels of yield.