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A Simple Soil Test for Detecting Sites that are Nonresponsive to Nitrogen Fertilization
Author(s) -
Khan S. A.,
Mulvaney R. L.,
Hoeft R. G.
Publication year - 2001
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2001.1751
Subject(s) - sugar , amino sugar , chemistry , hydrolysis , soil water , human fertilization , nitrogen , amino acid , hydrolysate , titration , soil test , soil ph , zoology , agronomy , food science , biochemistry , inorganic chemistry , biology , soil science , organic chemistry , geology
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 (NH 4 + amino sugar)‐N as gaseous NH 3 The NH 3 is collected in H 3 BO 3 –indicator solution, and subsequently determined by acidimetric titration. Recovery ranged from 97 to 102% when analyses were performed after treating samples with 15 N‐labeled (NH 4 ) 2 SO 4 or glucosamine, but did not exceed 6.5% with labeled glycine and was undetectable with labeled NO 3 or NO 2 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 NO 3 pollution of ground and surface water.