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This article in SSSAJ

  1. Vol. 65 No. 6, p. 1751-1760
     
    Received: Feb 20, 2001
    Published: Nov, 2001


    * Corresponding author(s): mulvaney@uiuc.edu
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doi:10.2136/sssaj2001.1751

A Simple Soil Test for Detecting Sites that are Nonresponsive to Nitrogen Fertilization

  1. S. A. Khana,
  2. R. L. Mulvaney *a and
  3. R. G. Hoeftb
  1. a Dep. of Natural Resources and Environ. Sci., Univ. of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801
    b Dep. of Crop Sci., Univ. of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801

Abstract

Recent work indicates that accumulation of amino sugar N in soil reduces the yield response of corn (Zea mays L.) to N fertilization, and that nonresponsive sites are detectable by determination of amino sugar N in soil hydrolysates. Unfortunately, the hydrolysis process is too complicated and time-consuming for use in routine soil testing. A much simpler technique was developed to estimate amino sugar N without the need for acid hydrolysis. In this test, 1 g of air-dried soil is treated with 10 mL of 2 M NaOH in a 473-mL (1-pint) wide-mouth Mason jar, and the sample is heated for 5 h at 48 to 50°C on a hot plate to liberate (NH4 + amino sugar)-N as gaseous NH3 The NH3 is collected in H3BO3–indicator solution, and subsequently determined by acidimetric titration. Recovery ranged from 97 to 102% when analyses were performed after treating samples with 15N-labeled (NH4)2SO4 or glucosamine, but did not exceed 6.5% with labeled glycine and was undetectable with labeled NO3 or NO2 Comparative studies using 12 nonresponsive and 13 responsive soils showed a very high correlation between soil-test N and hydrolyzable amino sugar N (r = 0.90***). Test values were significantly higher (P < 0.001) for nonresponsive (237–435 mg N kg−1) than for responsive (72–223 mg N kg−1) soils. The soil test described has important economic implications for production agriculture, and also should be of value for controlling NO3 pollution of ground and surface water.

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Copyright © 2001. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.65:1751–1760.