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MITR''0*tf FfRTilJ aTION Of SMALL GfiAXH AMD ITS
IFfFGT m CQfefffTITIOl WITH THF LTPQOMB-QBASS COMPARE OK GSOP
by
11 Liam iawreae# Frltofeett
A M ssertatioa Snbaittad to the
Graduate Faculty la Partial in If 1 Ilmen t of
The lefuireiaesb® for the Begrea of
DOCTOM 01 PHILOSOPHT
'Major Subject; Soil fe r tility
Approved;
'^oSSaeiiTWfiljor foil
'm m if'ifsfo r' 'fcepartmeii't
Iowa State College
1950
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UMI Number: DP13432
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S6 5 i
P 9 5 9 ^
YAHE Of OOMfWfS
IITEOIXJOT 1 0 1 ............. . . . . . . 1
STTOW Of U TRU J0P ............. 4
iiwsffOATioss ................. a®
• Mature of Competition Between Legume-Crass Seeding®
ami 1b• Oat companies Crop 18
Experiment 1. Tie Ids of three legumes grown
with nitrogen fe rtilise d ■ oats ........................................ 19
Plans • and procedures ...................... I t
Results and discussion SI
Experiment S. Yields of" alfalfa and. brome
grass grown with and without h itro g e a -fe rti-.
lized companion crops .......................................................... 27
Plans and procedures ........................................................ 27
Results and discussi o n .............................. 30
Experiment 3. Creeahouse studies on'the
growth of" alfalfa and bfoa#' grass wi th Tarring
lig h t in te n s itie s ................................... 41
Plans and procedures . . . . . . . 41
Results and ■ discussion 44
Experiment 4* field studies on the growth of ■
alfa lfa and bros© grass wi th varying lig h t
in ten sities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Plans and p r o c e d u r e s 62
Results, and discussion . . . . . . . . . . . . . . . . . . . . . . . . 66
Experiment 5. Yields, of alfa lfa and brome
grass with varying levels o f'n itre gen. and
phosphorus fe rtiliz e rs applied, to the ©at
companion crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Plans and procedures ................................. 72
Results and discussion .......... 78
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......... 77
■. Methods-of Decreasing 'the Competition Between
: legume-grass' See dings 'and the oat Companion
. .Crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Experiment 6. Yields of alfa lfa and brome
.grass with varying' tim es' of removal of the
companion crop ..................... ............ 80
Plans and procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Results and discussion ............................... 81
T9¥¥f
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-111-
xxp»rineat 7. stands and yields ©f alfa lfa
mad hroa# grass with varying Mae® of ap
plication of nitrogen to oat a ........... 85
Plans .and procedures . . . . . . . . . . . . . . . . . . . . . . . . . 85
Hesuits and dlsous sion . . . . . . . . . . . . . . . . . . . . . . . @6
vxperiasgt 8. Yields of seeding® with d if
ferent spacings of the oat companion crop . . . . . . 93
Flans and procedures . . . . . . . . . . . . . . . . . . . . . . . . . 93
..Insults and .discussion ................................................. 94
f t a m a x y 10®
OKfflRBAL DISC08810IT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............... 111
swmmt — u s
Lim m m m -'m m D . . . . . . . . . . m
ACXWWI*®0TO:TO!B . . . . . . . . . . . . . . . . . ............. 115
APPWmiX 127
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INTRODUCTION
'la th# mid-west small grains .have long been grown as
companion trope .for legum© sad grass seeding®* . In this thesis -
seediags are defined as legumes, .©r . legume -and grass mixtures,
used fo r hay or pasture purposes* the legumes.used are primari
ly a lfa lfa , red clover, or sweet clover, and the grasses are
brom© grass or timothy* Th# fa st growing small 'grains -are
planted with the' Seedlags to keep weeds in check until the
seeding® are established*
Oats-, the most emmon small grain in Iowa, occupies about
5,000,000 mores annually and Is second only to corn in acreage
In the state* ' With the introduction of disease-resistant,
stiff-straw ed varieties* oats can be grown'at high levels of
fe rtility with little danger of lodging* With th© high yields
possible under these'conditions,. oats may now be considered a
profitable grain'crop* rather than simply a source of early
forage, or a- nurse crop serving to keep weeds in check u n til
the new seeding becomes established*
Intensive investigations la lo ss during th© past six
■years have shown th a t nitrogen fe rtilise rs are especially ef
fective la increasing the yield of oats. Over 90 per cent of
the field s studied gave a significant and profitable increase
to nitrogen fe rtiliz e rs (3®}* An average yield increase of 7.7
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bushels of date per acre was ©fetainsd from an application of
SO pounds of nitrogen and'a IS bushel increase from'- the use of
' 40' founds ©f nitrogen per acre. Likewise, fe rtiliz a tio n with
®0 pounds or more of nitrogen greatly increased the yield of ■
eats over the check plots'when, lodging did net' occur*
these results are what might he' expected, 'In the f ir s t
place, oat® are normally grown la the rotation following one
or' more years 'of corn. Bits' leaves a low level of nitrogen'
in -the so il for th© small grain. Secondly, the oat crop oast
obtain its nitrogen in a relativ ely short growing period of
three and one-half months la the cool spring season when ammonia
and n itrate production in %« so il 'are relativ ely -low*.
■ Probably one of the most important factors determining
th# profitable use of nitrogen on the ©at' companion crop Is the
indirect effect th at th#1 fertilizer-m ay have upon legumes seeded
in the o ats, tb lie the' failure, of forage •••dings was .not un
common before the advent-of. relatively'heavy fe rtiliz a tio n ©f
small - grains, 'and-the loss of sta sis was accepted as a frequent
and-alm ost..inevitable hazard 'is many parts of'the gr&ln-belt,
the problem now takes on 'added significance, fbere are Indica
tions- that the stand# and yield# of legumes 'are reduced when
the m ounts of nitrogen fe rtiliz e r added to the-oat companion
crop are above a certain level (37).
fb© magnitude -©f the reduction ©f th© stand and yield of
the seeding at all. levels o f'fe rtiliz a tio n appear# to fee la-
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flmenced by -«Bfironaeatal conditions existing during the period
of growth, of tiie ©at companion crop. Competition between the
legume and oats 1® probably Intensified by nitrogen fertiliza
tion of the amall grain.
Since legume hay or-pasture occupies the key position in
many.com-belt rotations, iafoaastioa on the nature of the
competition between the legume seeding and the ©at companion
:erop and methods ©f reducing this competition were considered
of sufficient importance t© warrant th is study.
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11VIFW OF LXTKRMRfRf
a # causes. of the depression of hay yields following th®
nitrogen fe rtiliz a tio n ©f nurse crops May© met been widely
_ investigated*. nor are they clearly understood* al though seme
'■work Mas been dome eoacerslmg the competition between companion
crops aat betwees field crops and weeds,
the increased competition between fe rtiliz e d small grain
end the legune-grass companies. crep may involve one or several
environmental factors* ■ Sh«t©her# et al* (52^ reported t.he
d iffic u ltie s usually attributed to drought are largely due to
the crops with which th# forages are seeded* Harper (26) also
.reported that • the us# of small grain, companion crops resulted
In poorer stands of legumes* ' Sweet clover plants grown with a
companion crop were sm aller and weaker and less, able to endure
the w inter or dry periods than plants which did not have such
competition. l&atober* et a l. (§1) reported that bad effects
of either dry or wet weather ©a the young legume are accentuated
when a companion crop is used,' la a dry season- the roots of
the sm all.grains outgrow these of the fferog# seedlings and may
s© rob them, of moisture a® to cause stand failu res. In a wet
season the rank growth of the companion crop may shade the
young seedlings- so much that i t w ill weaken or k ill them.
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