Controlled Release N Fertilizer for Irrigated Arid-land Vegetable Crops: A Decade of Research

For over a decade we have been conducting field research with controlled release N fertilizers (CRN).   Initial studies were conducted at University Research Farms with lettuce (Lactuca sativa), broccoli (Brassica oleracea group Italica) , cauliflower (Brassica oleracea group Botrytis), carrots (Daucus carota) , celery (Apium graveolens), spinach (Spinacia oleracea), onions (Allium cepa ) tomatoes (Solanum lycopersicum), peppers (Capsicum sp.), watermelons (Citrullus lanatus), and sweet corn (Zea mays), using replicated, randomized, complete-block or split-plot treatment designs.  More recently, experiment-demonstrations were conducted in grower fields to expand the range of production scenarios and implement an outreach component to these studies.  CRN management frequently, but not always, provided production and economic advantages compared to traditional split application of standard fertilizers (sidedress and/or water run N).  Results show that it is of paramount importance to match product N release with crop N demand in specific crop production windows.  Placement can also be an issue when temperatures are extremely warm. Research also shows that the probability of positive production and economic outcomes is increased as soil texture becomes increasingly coarse or irrigation management more problematic. Specific outcomes to alternative production practices using CRN will be discussed.