HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Roberts, S. Articles by Phelps, J. P. Search for Related Content PubMed Articles by Roberts, S. Articles by Phelps, J. P. Agricola Articles by Roberts, S. Articles by Phelps, J. P.

Use of the Nitrate Soil Test to Predict Sweet Corn Response to Nitrogen Fertilization¹

ABSTRACT

A precise procedure for routinely interpreting soil test NO₃ as a fertilizer guide should help achieve more efficient use of N on crops with a high N requirement. The present study was designed to calibrate soil test NO₃ for predicting relative (percent of maximum) yield and the N-requirement index (NRI) of sweet corn (Zea mays L.) using Mitscherlich-type functions. The total N fertilizer requirement for the crop was equated to the potential yield increase multiplied by the NRI.

The NRI was calculated from N rate studies as the amount of N required per unit increase in sweet corn yield. ‘Stylepak’ sweet corn was grown 2 years in a row at a Warden silt loam (Xerollic Camborthids) site with rates of NH₄NO₃ the first year to give 84, 168, 252, 336, and 504 kg N/ha and a carry-over of from 10 to 70 ppm N the second year. Functions showed a range from 10 to 40 ppm soil NO₃-N was correlated with relative yields ranging from 62 to 98% of maximum and the NRI's range from 26 kg N/ton of yield increase up to 98 kg N/ton. It was concluded that with as low as 10 ppm NO₃-N, the potential yield increase multiplied by the NRI equated to a requirement of 251 kg N/ha. A soil test of 40–50 ppm NO₃-N correlated with 98–99% of maximum yield and indicated little or no fertilizer was needed. The NRI soil testing approach has definite advantages because it eliminates the controversial practice of calculating a fertilizer equivalent from soil NO₃ and fertilizer requirements can be calculated to fit different yield potentials of localized soil and cropping conditions.

¹ Scientific Paper no. 5380. Washington State College of Agric. Research Center, Pullman, Project 1990. Partial financial support was provided by Central Washington Research Assoc., Sunnyside. Presented before Div. S-4, Soil Sci. Soc. of Am., Los Angeles, Calif., 16 Nov. 1977.

² Associate Soil Scientist and Agric. Research Technologists III and I, respectively, at the Irrigated Agric. Research & Extension Center, Prosser, WA 99350.

Received for publication July 23, 1979. Accepted for publication October 18, 1979.