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Indexes of Sulfur Deficiency in Alfalfa. I. Extractable Soil SO}4{-S

Westermann, D.T. (1974) Indexes of Sulfur Deficiency in Alfalfa. I. Extractable Soil SO}4{-S. Agronomy Journal. 66(4):578-581.

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Sulfur deficiencies occur on many of the undeveloped
agricultural soils found in the mountain valleys of the
western United States; however, the majority of the S
soil-test correlation studies have been conducted on
leached and weathered soils. Identification of S deficiency
on alfalfa (Medicago sativa L.) growing in three
mountain valleys permitted the collection of S soil-test
correlation data for these undeveloped soils. This paper
reports the relationships found between extractable soil
SO₄-S levels and the response of alfalfa to S fertilization.

Soil samples were taken from 13 experimental sites before
active plant growth commenced in the spring in 30-cm
depth increments to 92 cm. Soil SO₄-S was extracted by
water, 0.1 M LiCl, and 0.032 M KH₂PO₄ and measured
by the methylene-blue reduction method. Significant correlations
were obtained between the SO₄-S extracted by
all three extractants from the 0- to 30-cm soil layers and
relative forage yields and total S uptake by the first harvest
of alfalfa at early bloom. Critical soil SO₄-S levels
of 3.0, 3.0, and 4.0 ppm in this soil layer were found when
extracted by water, LiCl, and KH₂PO₄, respectively. Inclusion
of KH₂PO₄-extractable SO₄-S to 92 cm did not
improve the curvilinear regression relationships, nor did
inclusion of percent soil organic matter. Increasing the
soil:extractant ratio from 1:2 to 1:3 did not significantly
change the amount of SO₄-S extracted by the KH₂PO₄
solution. The 0.1 M LiCl solution is recommended for
extracting SO₄-S from soils with relatively small amounts
of absorbed SO₄-S.

Item Type: Article
NWISRL Publication Number: 0290
Subjects: Irrigated crops > Alfalfa
Soil > Chemistry > Sulfur
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:51
Last Modified: 15 Feb 2017 23:33
Item ID: 262