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III. Effects of Lodging on Crop Development and Yield

III. Effects of Lodging on Crop Development and Yield

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218



MOSHE J. PINTHUS



through them in many experiments fall into line with each other and enable

rather definite conclusions to be reached with regard to certain effects.

1 . Comparison between Samples from Lodged and from

Standing Areas within the Same Plot



This method has been used in early work (e.g., Welton and Morris,

1931) as well as in more recent studies (Das et al., 1966; Miladinovic,

1959; Mulder, 1954; Syme, 1968). It is based on the assumption that the

variations in lodging within the plots have not been caused by factors that

may per se affect the crop characters under investigation. In most cases

such an assumption will not be justified.

2 . Comparison of Lodging Plants in Untreated Plots with Erect

Plants in CCC-Treated Plots

A vast number of field experiments with 2-chloroethyl trimethylammonium chloride (CCC) on cereals, primarily wheat, have been conducted

throughout the world since 1961 and up to the present day. The reports

on these experiments provide much information on various plant characters, particularly grain yield, from lodged and from standing plots. However, many plant characters, including grain yield, are affected by CCC

also in the absence of lodging (Humphries, 196Sa). Moreover, strong

CCC x environment interaction effects should also be considered.

Some characters, e.g., those determining baking quality of wheat grain,

are hardly affected by CCC (Humphries, 1968a) and their response to

lodging can be ascertained by the method under consideration. This

method also enables us to deduce the effects of lodging on characters for

which reliable estimates on their response to CCC, in the absence of lodgig, are available, e.g., elongation of culm internodes. Moreover, considering information on the effect of CCC on the grain yield of wheat, in the

absence of lodging (Humphries, 1968b; Lowe and Carter, 1972; Pinthus

and Rudich, 1967; Primost, 1968; Schultz, 1971; Sturm and Jung, 1964;

Zadontsev et al., 1969), it can be assumed that this effect will in most

cases be slight or account for an increase of up to 15%. Consequently,

differences in grain yield beyond this limit, between standing treated plots

and lodging untreated plots, can be attributed to the effect of lodging on

grain yield.

3. Artificially Prevented Lodging



Within a crop which is liable to lodge, the plants in some plots are supported to prevent lodging. This method has been applied by Mulder



LODGING I N WHEAT, BARLEY, AND OATS



219



(1954) and by Zadontsev et al. (1969). Theoretically, this is the most

sound method. However, its restriction to rather small plots reduces its

practical usefulness.

4 . Artifically Induced Lodging



In order to be effective this method should be accompanied by supporting the plants in control plots in order to prevent their lodging.

Harrington and Waywell ( 1950) induced lodging by exposing plots individually to a strong controlled wind produced by an airplane propeller.

A movable chamber in which field plots can be subjected artificially to

various rainfall and wind intensities was constructed and applied by LekeS

and ZeniSEeva (1962) to induce lodging. A mobilc wind tunnel for the

same purpose was described by Udagawa and Oda (1967). Lodging induced by these techniques is most similar to that occurring in nature, but

their application is too cumbersome.

Spraying plants after anthesis with heteroauxin was used to induce lodging by Petinov and Urmantsev (1964). This technique will most probably

cause effects on plant characters in addition to lodging.

Lodging was accomplished by Laude and Pauli (1956) through bending

and pinching the culms between the fingers. The results obtained by this

technique, which involves mechanical injury, can pertain only to stem lodging following breakage of the culms.

Sisler and Olson ( 195 1 ) induced lodging by pushing the plants down

with a long board following irrigation of the plot. This was done gently

and with care to avoid damaging the culms or the roots. Consequently,

lodging accomplished by this technique resembles root lodging.

The most frequently applied technique was devised by Sisler and Olson

( 195 1 ) and used by them to induce lodging in barley. It was subsequently

applied with this crop by Day (1957) and by Day and Dickson (1958),

with oats by Norden and Frey (1958) and Pendleton (1954), and with

wheat by Jankovid (1966a) and Weibel and Pendleton (1964). In this

technique the plants are allowed to grow up through a wire netting which

is installed for each plot 30-60 cm above the ground. Lodging is obtained

by moving the wires of the respective plots horizontally; in the control

plots it is prevented by the support of the intact wire. The obvious advantages to this technique are the possibilities of inducing lodging at different

degrees from the perpendicular and at various growth stages, as well as

its maintaining the erect position of the control plants. The disadvantages

are some damage to the plants, which can hardly be avoided, and the difficulty of applying this technique to large field plots.



MOSHE J. PINTHUS



220



B.



EFFECTSON GRAINYIELD



1 . Degree of Lodging and Growth Stage at Which I t Occurs



The effect of lodging on grain yield is dependent on its severity and

on the time of its occurrence. Early lodging, during the period of intensive

stem elongation, may hardly affect grain yield because of the rapid recovery, which will restore the upright growth of the plant prior to heading.

Culm breakage at this stage, to which should be ascribed the yield reduction from lodging in Laude and Pauli's (1956) experiment, is not to be

expected under natural field conditions. Lodging close to maturity cannot

affect grain yield directly but may cause losses due to its interference with

harvest.

Heading and early grain debelopment are obviously the most crucial

stages. Artificially induced lodging at heading reduced grain yield by

27-40%, whereas the yield reduction due to lodging at about the softdough stage surpassed 24% only at one location (Table I ) .

TABLE I

Reduction of Grain Yield Due to Artificially Induced 90' Lodging at Two Growth Stages

Lodging

induced at:



Crop



Location



Winter wheat

Winter wheat



Kansas

Illinois



Spring barley

Fall-sown barley

Oats

Oats



Manitoba

Arizona

Iowa

Illinois



Heading



15-20

Days

after

heading



Reference



(%I



(%I



Laude and Pauli (1956)

Weibel and Pendleton

(1964)

Sisler and Olsoii (1951)

Day (1957)

Norden and Frey (1958)

Pendleton (1954)



27

31



22

20



34

40

36

37



24



39

23



17



In other experiments reported by Sisler and Olson (1951) and in those

of Jancovid ( 19866a), lodging at heading reduced grain yield by 65 % , perhaps because in these experiments plants were forced to remain flat on

the ground. Artificially induced lodging at 45" caused one-fourth to onehalf the reduction of that at 90" (Day, 1957; Norden and Frey, 1958;

Pendleton, 1954; Sisler and Olson, 1951) .



LODGING IN



WHEAT, BARLEY,



AND OATS



22 1



Comparison of the yields in lodged plots with those of supported plants,

in experiments in the Netherlands (Mulder, 1954) showed that reductions

of 4-33%, 4-22%, and 0-31 % for spring wheat, barley, and oats, respectively, were obtained, depending on the severity and time of occurrence

of lodging.

As mentioned above, experiments with CCC may also supply information on the effect of lodging on the grain yield of wheat. In these experiments, which were conducted primarily in Europe, the greatest increase

in grain yield from treated plots was 82% (Humphries, 1968a). However,

an estimated increase of up to 40% would be more realistic. The effect

of the growth stage at which lodging occurs may also be deduced from

some of the CCC experiments. This is illustrated by some of our own (unpublished) results from an experiment with F.A. 8193 wheat at two locations in Israel, where severe lodging was effectively controlled by CCC. The

grain yield at one location, where lodging started 3 days after heading, was

3130 kg/ha in control plots and 4400 kg/ha in CCC-treated plots; at

another location, where lodging started 20 days after heading, the yield

both in treated and in control plots was 4500 kg/ha.

2. E#ect on Grain-Yield Components



The above cited reports on artificially induced lodging, as well as

Mulder’s experiments, indicate that lodging at heading affects both the

number of kernels per head and the individual kernel weight. Lodging that

occurs later affects primarily kernel weight. The increase in wheat yield

from plots in which lodging had been prevented by the application of CCC,

was associated in many cases with an increase in the number of kernels

per spike, whereas kernel weight was only rarely, and then slightly, affected

(Humphries, 1968a; Lowe and Carter, 1972; Martin, 1968).

c.



EFFECTSON GRAINQUALITY



Lodging may cause shriveling of the grain and reduce its test weight

(bushel or hectoliter weight). In most of the experiments in which lodging

was artificially induced or prevented, a similar reduction in test weight was

found amounting to about 8 % for wheat and barley and 15% for oats.

In these experiments as well as in others (Gately, 1968; Hirano et al.,

1970; Miladinovic, 1959), the N (or protein) content of the grains from

lodged plots exceeded that from standing plots by 3-20%.

Lodging may reduce milling quality of wheat (Hirano et al., 1970)

whereas its effect on baking quality seems to be negligible and may sometimes even be advantageous (Miladinovic, 1959). Lodging, however, ad-



222



MOSHE J. PINTHUS



versely affects the malting quality of barley (Coenradie and Wilten, 1961;

Day and Dickson, 1958).

Sprouting in the heads has also been found to occur more frequently

in lodged than in standing crops (Kivi, 1961 ) .



D. EFFECTS

ON



CULM



DEVELOPMENT

AND TILLERING



The elongation of the two upper culm-internodes, which is not completed until 5-10 days after heading, can be affected by lodging which occurs up to this period. Thus, although CCC reduces internode elongation,

the two upper culm internodes of erect treated plants have often been

found to be longer than those from lodged untreated plants (see, e.g.,

Pinthus and Halevy, 1965). Since these internodes comprise about twothirds of the total culm length, any interference with their development

may affect straw yield considerably. Straw yield was indeed as much as

25 and 21% lower for lodged wheat and oat plants, respectively, than

for supported plants (Mulder, 1954).

Lodging may sometimes promote the development of late tillers, presumably because of the reduction in the competition for minerals and carbohydrates by the lodging culms. However, these tillers rarely attain normal growth.

E.



PHYSIOLOGICAL EFFECTSOF LODGING



The most obvious effect of lodging on the plant’s physiological processes

is its interference with carbohydrate assimilation (Mulder, 1954). This results from a large part of the foliage and other photosynthesizing parts

being shaded by plants which are leaning or lying on top of them. The

heads of low-lying plants in a lodging crop may sometimes be completely

empty, whereas those of the plants lying on top develop normal grain. The

reduced carbohydrate assimilation will, of course, affect primarily their accumulation in the grains, but, depending on the time of lodging, may affect

any process or plant part demanding carbohydrates during that time.

The protein in cereal grain originates primarily from nitrogen which has

accumulated in the foliage prior to heading. Therefore, its absolute amount

in the kernels is hardly affected by lodging, which occurs at heading or

thereafter. Consequently, the percentage of N, or protein, in the grain of

lodged plants may rise due to the decrease in carbohydrate accumulation.

Lodging which involves culm breakage will also interfere with the translocation of carbohydrates and of minerals (Hashimoto, 1959; Pauli and

Laude, 1959). In this case the absolute content of N and other minerals

in the grain may also be reduced if lodging occurs during heading or early

grain development.



LODGING I N



F.



IMPACT



OF



WHEAT, BARLEY,



AND OATS



223



LODGING

ON GRAINHARVEST



Very few data are available on the quantitative effects of lodging on

combine harvesting. Considering the report of Baumgartner ( 1969), it may

be concluded that, in a lodged crop, harvest capacity can be reduced by

up to 25% and the loss of unthreshed heads may be doubled. The moisture

content of lodged grain will be higher than of unlodged grain, which also

interferes with the harvest and may increase the expenses for grain drying

by 30%.



G.



INCIDENCE OF



DISEASESI N LODGING

CROPS



Some environmental factors and several plant characters which promote

lodging also improve the growing conditions for rots and leaf diseases.

Moreover, these diseases are often favored by the microclimate prevailing

within a lodged crop. These facts have been recognized by various workers

(e.g., Bauer, 1963; Mulder, 1954; Weibel and Pendleton, 1964), but no

relevant data seem to be available.

The eyespot disease, which itself may cause lodging, seems to be enhanced by the conditions within a lodged crop. Its reduction due to the

application of CCC can be attributed partly to the control of lodging by

this chemical (Bockmann, 1968).



IV.



Plant Characters Associated with lodging



Culm length and the shape of the head affect the magnitude of the lodging-inducing torque whereas the plant’s resistance to the torque is dependent on various other characters. The information on the association of

these characters with lodging is derived predominantly from the study of

varieties or lines differing in lodging resistance. In evaluating this information, which is often contradictory, the following points should be considered: First, the reliability of the assessment of lodging resistance, considering the strong variety x environment interaction effects on lodging

(Section VII, A, 1 ). Moreover, in certain cases lodging assessments have

been based on mechanical properties rather than on direct field observations.

Second, varietal differences in lodging are accompanied by differences in

many other characters which may or may not be correlated with each

other. Partial correlation and path-coefficient analyses can be useful in this

respect. Third, interaction effects of variety x different characters on lodging cast much doubt on the relevance of studies performed on a small

number of varieties. Similarly, the association with characters which are



MOSHE J. PINTHUS



224



strongly affected by variety x environment interaction effects must be

based on extensive tests of these characters. Finally, a high correlation

between a certain plant character and lodging does not necessarily imply

a causal relationship. This reservation also holds for the information obtained through comparison of lodged and erect plants in the same plot.

A.



CULMCHARACTERS

1 . Length



Culm length, which comprises the lever of the lodging-inducing torque,

is obviously associated with lodging. Nevertheless, in many of the investigations in which no dwarf or semidwarf varieties were included, no marked

correlation between these traits was ascertained (Baier, 1965; Rodger,

1956; Zimina, 1968). This may be ascribed to the occurrence of lodging

prior to complete culm elongation as well as to culm length X maturity

interaction effects. An early, short-strawed variety close to maturity will

be taller and more prone to lodging than a late, long-strawed variety, which

at that time has attained only the late boot or heading stage.

With regard to lodging at heading, the length of the three or four lowest

internodes is of greater effect than that of the two uppermost internodes,

which, although comprising about two-thirds of the final culm length, have

not yet completed their elongation at this stage.

2 . Basal Internodes

From the mechanics of lodging it is apparent that the properties of the

basal culm internodes should affect lodging resistance. Some durum and

rivet wheats have solid stems, and this character has also been bred into

certain common wheat varieties in order to achieve sawfly-resistance

(Dahms, 1967). However, in most wheat varieties, as well as in barley

and oats, the internodes are hollow. Therefore, their flexural rigidity is

greatly dependent on both diameter and wall thickness (Section 11, B ) .

Varietal differences in lodging resistance were indeed found to be significantly positively associated with the diameter and wall thickness of the

basal internodes-primarily the second one-in many studies (Hamilton,

1941; Hansel, 1957; Jellum, 1962; Mukherjee et al., 1967; Multamaki,

1962; Oda et al., 1966; Sechier, 1961). In other studies, marked positive

correlations were established between these characters and culm bending

or breakage (Bhamonchant and Patterson, 1964; Hancock and Smith,

1963; Norden and Frey, 1959). The coefficients for the correlations which

were found between these culm characters and lodging, bending or breakage, rarely exceeded the value of 0.7.



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