ISHS Acta Horticulturae 542: VII International Symposium on the Processing Tomato
PRE-SIDEDRESS SOIL NITRATE TESTING TO DETERMINE YIELD RESPONSE TO FERTILIZER APPLICATIONS IN PROCESSING TOMATOES |
| Authors: | H.H. Krusekopf, J.P. Mitchell, T.K. Hartz, D.M. May, E.M. Miyao, M.D. Cahn |
| Abstract:
Overuse of chemical N fertilizer is an economic loss to farmers and has been linked to nitrate–nitrogen (NO3–N) contamination of water supplies. The Pre-Sidedress Soil Nitrate Test (PSNT) has been shown to be a reliable tool for reducing N fertilizer inputs while maintaining yields. The PSNT is based on the correlation between soil NO3–N levels at early plant growth stage and the probability of crop yield response to subsequent sidedress N applications. Our research to test the viability of the PSNT for processing tomato production in California’s Central Valley was carried out at ten field sites during the 1998 and 1999 growing seasons. Sidedress N was applied at six rates from 0 to 280 kg·ha-1 N, with six replications of each rate per field. Soil NO3–N levels were measured immediately prior to sidedress N application. Only four fields showed a significant yield response to N application, and in only one field did yield increase with N application of >56 kg·ha-1 N. Yield response to sidedress N did not occur in fields with pre-sidedress soil nitrate levels above 16 mg·kg-1 in the top 30 cm of soil depth. These trials indicated that N fertilization could be reduced substantially below current industry standards without lowering yields, especially in fields with higher residual soil nitrate levels. | |
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