December 1, 2007
- best management practice,
Because reclaimed water may contain up to 9.9 ppm of nitrate-nitrogen, it may be a source of N that should be counted in the fertilization programs of seepage-irrigated tomato (Solanum lycopersicon L.). The objective of this study was to assess the contribution of non-fertilizer N sources on tomato grown with seepage irrigation and reclaimed water. The study was conducted in Spring 2006 in Palmetto, FL, with N rates ranging from 20 to 420 lb/acre. Based on a 50% use of N in reclaimed water and organic matter mineralization, an estimated 56 lb/acre of N were supplied by non-fertilizer sources. Sap NO3-N concentrations were similar and "sufficient" with N rates between 116 and 476 lb/acre throughout the season. Extra-large yield at first harvest (70% of total yield) responded slightly negatively to N rates. Total marketable, total extra-large, total first and second harvest yields, and fruit quality parameters did not respond to N rates. These results with spring-grown tomato harvested twice suggest that 1) the N contribution of the reclaimed water to the crop should be counted in the overall N fertilization program; 2) tomato yields and nutritional status responses to N rates from all sources were small; 3) more than 50% of the N supplied by the reclaimed water was used by the plant; and (4) grower's N rate could be reduced by 50% to 100% of the NO3-N contribution of the reclaimed water without reducing yield or quality, thereby resulting in a $18 to $37/acre reduction in fertilization cost.