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Parker frost Pratt
A Dissertation Sabalttad t© the
Graduate Faculty la partial Falflllmmt of
The leqiiirsmmts for the Begree of
BfWftr&S At? tFlfYT AtSAIitfV
Major Sitojeoti Soil Fertility
Approved;
low State Collage
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UMI Number: DP13429
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IX*.
A* fetasaitat Release l^'Grgpping «wt'by Related
Methods * * * * * * * * * ****"• *********** * ***#**#*■#**• * * * * * * 3
1*. jMMun&n Release fern Sell Fractions and from
%eeifi© itoerala **********,,.«.****•*****•**#«**** 9
0* Relationship between fixation and Release of
Potassium 11
S« Potassium Release in Imi Soils 13
XXX* X13®S$lB8fiESIi **####»«#****#***#* * • * • • ****** *••*•»*• *«*•••* 16
A* FstassiaB Utloiis# to .Alfalfa «•»••••*#»*## •>*•»***** 16
1*. Methods and materials 16
2* Hssifllts 18
8* Potassium leleas# by Laboratory Methods sad
Correlations to Release to Alfalfa ................. 21
1. Methods and materials ...... *..... 21
t« Nitric acid extraction procedure ********* 22
b. Cation exchange resin extraction
procedure .... 23
e* Magnesium chloride extraction procedure «*• 23
■ d* Sxclwsgoabla potassium procedure
e. Total potassium prooodwe **********••** * * *
2* Result# ******* #*** ***"#•**.*.*•*►** * * #** ***** ** ** * * * 2lj
0*, . Potassium Release . from ■ iisse ■ fraeMms of Soils ****** 35
1. Methods and materials 3$
2* Results ............................ 37
8* Effect of Potassitaa Release on Subsequent
Fixation .52
1* Methods and materials ..... $k
2. Results ....................................... 52
T 3 7 0 3
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71. XSXSBtfBBB CITED ......................................... 68
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The mount of iaehaisgeitble 1 in most' Iowa soils is sufficient to supply
the needs of crops for only 1 to 3 years* The replenishment of exchangeable
S is thus topertabt even in * 1 to. 3 year craping period* Jlthough the
level of exchangeable 1 for * given soil, .is not constant throughout the year,
variations m e usually Paring the summer when crops ar@. growing
rapidly and absorbing relatively large amounts of nutrients the level of
exehgaigwbX® E decreases, but not in proportion to the amount removed by
the ©raps* luring the fall,, winter, and early spring the exchangeable I
increases to about the level of the preceding spring* Therefore, although
over a period of many- years the level of «ehaage®ble 1 usually decreases,
the year to year variation to not large* ft® win 'process whereby the ex
changeable I is maintained at a fairly constant levej is the release of
the nenexchaageable fora# of E to the exchangeable for®*
The toaetohangeabto I to assumed to be that which to held in the
crystal lattices of primary and secondary soil, minerals* §y weathering .
processes this. 1 to released and becomes an exchangeable cation which can
be replaced by other cations of the soil solution#
field eapertoents daring the past few years have shown a number of
ewes of S deflei®aoy in low soils* With more utlliMtion of I. fertilizers
to toeraas© production in these 1-deficient area®' there to need for more
information on E'release from- reserves of noa^sehangeable I in Iowa suite *
This, infoimation' can be of help in to# late*pr©totiofi @f field results and
may thereby lead to • a more efficient fertiliser use#
Previous studies of S- release • in Iowa soils had been conducted using
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laboratory methods (29,32, 33, 3k), tat there was a need for a study la
which release of X % laboratory methods was eerrelated with release to
plants * Saadf soils had been shown to release such smaller amounta of K
than fine toxtorad soils (3k), tat, there was a need for more infoamtioa
■on release of I from the silt and clay fractions of lows soils* Thar® ms
also need for infonaation which would clarify the aeebandsas involved in
I release* the studies reported herein were, conducted In an attest to
fill these needs*
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II. BBTHSBT QF IjXIJSAHJBS
4. Potassium I®l@aat by Cropping and. by
Related Methods
la field studies tb® velum# of soil fire® which th® plants absorb K
cannot ba mmmtely measured or eontrelled* As a resalt, there is a© '
assurance that any given sample of soil taken for laboratory studies is
representatives of this soil from which the plant® absorb I* For this
vmmm$ only qui&itatiw® or s«!-^«taiitailv® estisatlOM' of I release
east be Bad®"* leoaase in the greenhouse the soil volume emt be more ®as.i3y
controlled, gre«plioase preoodur®® 'have been .used almost entirely to ob
tain a quantitative measure of K release to pleats* The usual procedure
^ involves growing successive crops in a given weight of soil, analysing
the crops to obtain' 1 absorption,' and analysing the sell for exchangeable
I before sad after the cropping' period, fh® I absorbed by the plant® aims
the decrease in exchange*!© S gives, the amount of 1 release from non-
exchangeable forms during the cropping period#
Many lai»ratory methods have been used in I release studies* These
include aetractioa with .It. per cent 801, extraction with 1.0 I HNO3, moist
incubation after removal of the exchangeable K, alectrodialygis, freezing
and thswlng, and wetting and diying* ■ Neubocser methods have been used by
.■some- investigators*
Martin (355, by ©adaastiv® cropping in the .greenhouse, found striking
differences in the amount of I release among soa« soils of California.
Bntglwd and Ifarbin (26), by cropping with barley ..and tomato#®, demonstrated
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that the «cb*wig©abl® i decreased rapidly daring the first few crop® and
then, remained fairly constant during the remaining cropping periods. For
soils that were high In ■ soechimgeahle K> all or a major portion of the .1
absorbed by the first crops was balanced by a decrease in exchangeable I.
1® cropping continued, an increasing proportion of the I absorbed 'by the
plants represented K release from »on«a®l»g@able forms, until a point was
reached at 'which there ms ip farther redaction in axobttagoahlft K. With
cropping' btsfond this point' the 1 supply to the plants depended entirely on
1 release. Chandler* Peeob* and Chang (1$) conducted a similar study o»
several soils of lew lorfc using ladino ©lover as the experimental crop.
Their results also showed, that the exchangeable S decreased rapidly with
the first few crops and then decreased more slowly to a level at which the
1 aopply to the crop depended on I' release. . They found that I release in
tfaa greenhouse was related to the response to 1 fertiliser®, in field ex
periments.
Gedfolz (23) found that plants Rowing, in soils from which the m»
changeable K had been removed war# able to mature and-giir# good yields
without tli# us® of i fertilizers* In this ease the total I absorbed by
the plants represented 'release. Qholsten, and leover (2k) reported that
more than 0 per cent of the I «aofei from soils by eight crop® of millet
cam# from iwa®xel»ge«W,® font®. Bear, Prince* and Maleolst (H) reported
eonsMeratolt release of I £jem 20 lew jenaey soils when the soils. were
subjected to cropping, lyres* Takahasi, and Kanehire ( 8) I'li,
found that daring k*$ years of continuous cropping with napier grass the
K reltas^l from several Samiian soil® was several time® the mam% of .
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