Best management practices for vegetable production emphasize optimal yields with the least amount of fertilizer to reduce environmental impact. Rainfall and irrigation often leach fertilizer nutrients away from the root zone (Hochmuth, 2003). Various types of slow-release fertilizers may extend the availability of nutrients, especially N, to the plant (Maynard and Lorenz, 1979) and reduce N leaching losses from soil (Wang and Alva, 1996). Research has been conducted with sulfur-coated urea on vegetables in Florida (Simonne and Hutchinson, 2005); polymer-coated fertilizers on greenhouse/nursery plants (Ristvey and Lea-Cox, 2004) and strawberry (Fragaria spp.; Albregts and Chandler, 1993); and methylene-urea slow-release fertilizers on citrus (Citrus spp.; Zekri and Koo, 1991) and processing tomato (Solanum lycopersicum; Koivunen and Horwath, 2005). Slow-release fertilizer can produce yields at least equal to those observed with split applications of soluble fertilizers in lettuce (Lactuca sativa; Khah and Arvanitoyannis, 2003), tomato (Senthil-Valavan and Kumaresan, 2006), and bell pepper (Wiedenfeld, 1986).
A slow-release methylene-urea polymer-based liquid N fertilizer, Nitamin® (Georgia Pacific Resins, Atlanta) releases nitrogen by microbial decomposition (not coated). It is completely water soluble and can be blended with other liquid fertilizers and then used in drip irrigation. The manufacturer claims the urea polymers convert to plant-available forms of N [i.e., ammonia (NH4) and nitrate (NO3)] over a 60-d period under most soil conditions. The release rate is affected by microbial activity, and anything that affects soil microorganisms such as soil temperature, oxygen concentration, and water availability has the potential to impact the N release rate (e.g., the release rate of N will be slower under cooler soil temperatures). No minimum soil temperature is required, and there does not appear to be a delay in N release after soil fumigation because of the rapid buildup of microorganisms shortly after fumigation and before the start of fertilizer injections (J. Wargo, unpublished data)
The objective of this study was to compare the effectiveness of two formulations of slow-release fertilizers under drip irrigation and applied at different rates with conventional fertilizer programs for bell pepper production. Experiments were conducted in two regions of North Carolina on two different soil types. Yield and fruit quality were examined.
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