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III. Botanical and Physiological Considerations

III. Botanical and Physiological Considerations

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RATOON CROPPING



295



FIG.2. Longitudinal section of a plant crop pineapple developed from a slip planted

22 months earlier. (Photo by courtesy of Pineapple Growers Association of Hawaii.)



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D. L. PLUCKNETT, J. P. EVENSON, A N D W. G. SANFORD



stem may also develop into shoots, but these usually do not produce

satisfactory yields. A very unusual selective harvest system in horseradish (Armoracia rusticana) has been employed in Czechoslovakia

(Courter and Rhodes, 1969). In this system the original or mother plant

is left in place and only the young side roots are harvested annually.

In dicotyledons new growth may occur from new shoots on the lower

branches or stems following harvest. Total harvest ratooning may be

necessary to produce satisfactory regrowth, but not always. Cotton, for

example, can produce ratoon crops either by taking a second harvest

from old plants, or by cutting to near ground level and harvesting from

new growth (Fig. 3) (Thomson, 1964).

Because more is known of tillering in sugarcane than for most other

crops, a detailed discussion of this subject may be of value in pointing

out the important botanical and physiological factors of ratooning.

A.



TILLERING

OF SUGARCANE



Upon removal of the apical bud at harvest, lateral buds develop into

tillers. Tillering is governed by such factors as inherent varietal qualities,

soil moisture and irrigation, time of planting, spacing, soil nutrient supply,

soil tilth and aeration, temperature, and other factors (Subba Rao and

Prasad, 1962).

In sugarcane, underground buds that develop into ratoon tillers are

borne on joints of the tapered base of the primary stalks (Martin et al.,

196 1). The old “stubble piece” or stool left after harvest usually consists

of 3 to 10 short joints, each having a bud (Edgerton, 1938). Upper buds

germinate first, and are most susceptible to cold or mechanical injury

(Edgerton, 1938). N. J. King et al. (1965) recommended discing or other

tillage to damage these surface buds, thus allowing germination of deeper

buds to ensure a deeper root system in the ratoon crop.

The sequence of tiller origin in sugarcane is as follows: lateral buds of

the primary stalk develop into secondary shoots, buds on secondary

shoots develop into tertiary shoots, etc. (Martin et al., 1961).

Loh and Tseng (1956) distinguished four types of tillers in sugarcane,

based on the angle formed by the tiller stalk and the ground. More or less

erect tillers displayed most active growth, semidecumbent or sprawling

tillers were least active. Tiller mortality was determined by the time of

emergence of indi-idual tillers and by tiller growth type. As in many crops

only a portion of total tillers produced may survive, perhaps as few as

one-third (Sastry and Venkatachari, 1962). In subtropical areas where

frost injury may occur it has been observed that early tillers have greater



RATOON CROPPING



2 97



FIG.3. Ratoon crops in cotton may result in two ways, differing in method of management following harvest. (A) Ratoon cotton not slashed to ground level following harvest.

(B) Left: ratoon cotton, not slashed; center: ratoon cotton slashed to ground level following

harvest: right: sown cotton o f same age as ratoon cotton in center (small plants almost indiscernible).



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D. L. PLUCKNETT, J. P.



EVENSON,

A N D w.



G. SANFORD



chance of survival than later shoots (Raheja, 1956). Stokes (1956) found

that carbohydrate reserves in stubble were influenced by date of harvest,

and highest brix and sucrose were found in stubble of the late-harvested

crop: further, h.e attributed poor ratoon growth to low food reserves of the

early harvested crop. Edgerton ( 1938) found poor ratooning varieties

had a lower number of viable healthy buds in late winter.

Raheja ( 1 956) examined physiological factors relating to tiller growth

of sugarcane. Heavy tillering was found to be desirable. Early-formed

tillers had greater chance of survival and contributed more to yield, mainly because crop quality was higher with early tillers. Nitrogen applications and irrigation greatly influenced tillering, while ambient temperatures below 70°F retarded tiller formation. Tillering of ratoon crops was

earlier and more profuse than in the plant crop.

Tang and Ho (1962) studied six successive sugarcane ratoons in a

sandy loam soil in Taiwan. Total tillers per acre ranged from 77,000 to

125,000 while millable stalks ranged from 36,000 to 40,000. Yields were

highest in the fourth ratoon, lowest in the fifth ratoon. The authors concluded climatic effects had more influence on yield than the number of

ratoon crops harvested.

B. ROOTFACTORS



The question of whether roots of the old sugarcane stool continue to

function after harvest has been a matter of controversy. Baver et al.

( 1962) presented rather convincing evidence that the old root system

ceases to function soon after harvest. Ratoon shoots contained 32Pwhen

labeled fertilizer was applied 4 inches deep within a split stool, but not

when the phosphorus was applied 4 inches deep and either 6 or 12 inches

on either side of the stool. The authors concluded the old roots did not

absorb 32Pfrom the root zone, but rather that only the new roots were

active. Water extraction curves following harvest were identical with

those of the preceding plant crop, indicating little function of the old root

system in water uptake for the new shoots. Additional evidence was

supplied by time-lapse cinegraphy of ratooned plants using a window

box technique. Rapid deterioration of the old root system and rapid

growth of the new root system resulted following harvest.

As in sugarcane, sorghum seems to produce a new root system very

quickly after harvest. Plucknett et al. (1970) observed a direct relationship between ratoon performance of both grain and forage sorghum lines

and the extent and vitality of root development (Fig. 4).

In banana the parent corm gives rise to buds usually on its middle

or upper section: these buds develop into sucker corms which pro-



RATOON CROPPING



299



t i c , . 4. Root system5 of sorghum, lifth ratoon, in Hawaii: ( A ) Roots of Haygrazer, a

ready-ratooning forage hybrid. The grid over the roots is spaced on a 6-inch scale: thus

Haygrazer roots extend over 12 inches deep and spread over 12 inches laterally from the

crown. ( B ) Shallow, poor root system of RS-610, a temperate grain sorghum. RS-610 ratoon performance is relatively poor.



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D. L. PLUCKNETT, J. P.



EVENSON,



A N D W. G. SANFORD



duce the ratoon crop (Simmonds, 1960). Because more sucker corms

develop than are necessary or desirable for high fruit yield and quality,

sucker corms and shoots which are located too close to the surface are

pruned, otherwise the entire plant “mat” complex will be shallow-rooted

and ratoon crops may not succeed. Other reasons for pruning include

undesirable orientation of the sucker corms in the row and selection of

suckers according to age in order to schedule fruit production during the

most favorable season.

IV. Ratooning a n d Environmental Factors



A. GENERAL

The fundamental basis for ratooning is the ability of the plant concerned

to behave as a perennial and to continue growth beyond one fruiting or

harvest cycle, environment permitting.

Ratooning may be used in any of the following situations:

1 . To carry a crop over from one season to the next for a period of

years without replanting, as in sugarcane (Antoine and Ricaud, 1963;

N. J. King et al., 1965), cotton (Harland, 1949; Ellern, 1966; Evenson,

1969, 1970), and rice (Garcia Duran, 1962, 1963; Evans, 1956, 1957;

Szokolay, 1956).

2. To allow multiple harvesting from a single sowing to be carried out

throughout one year or more as in sorghum (Parbery, 1966; Plucknett

and Younge, 1963; Mackenzie and Parbery, 1966; Plucknett et al.,

1970) and rice (Garcia Duran, 1962, 1963).

3. To ensure maximum use of a growing season that may be too short

for two sown crops in succession, as in rice (Evatt, 1966).

4. To develop the subsequent crop in situ from basal suckers as in

bananas (Simmonds, 1960) and pineapples (Collins, 1960;Johnson, 1935).

5. In slow-growing species to develop a crop on the already established root system of the previous cycle. In particular the coppicing system of producing timber is an extreme example (Edlin, 1944; Wilson,

1968).

6. To reschedule crops that have gone out of phase with agronomic

schedules as is the case with early-sown cotton in northern Western

Australia that may ripen while the monsoon is still on, with disastrous

boll rot (Shedley, 1969).

The influence of environmental conditions on survival of ratoon crops

depends largely on the adverse effects of low temperatures and drought.

Cotton (Ellern, 1966; Evenson, 1969), sorghum (MacKenzie and Par-



RATOON CROPPING



30 1



bery, 1966), and rice (Evans, 1957) can withstand long periods of water

stress under tropical conditions when ratooned, and before regrowth

commences.

When crops which ratoon well in tropical areas are moved farther out

of the Tropics or into areas of increasing altitude within the Tropics, low

temperatures can become critical for ratoon survival. In northern parts

of the United States cotton belt, ratoon crops cannot survive the winter,

therefore cotton in these areas is essentially an annual (Templeton, 1925).

In the western United States ratooned cotton can survive in California

and Arizona (Wene, 1965; Van Schaik et al., 1962: Peebles and Fulton,

1944). In southern Australia low winter temperatures cause up to 95%

mortality of ratoons in the Murrimbidgee Irrigation Area unless the

“stubs” are adequately covered with soil, and even then 50% mortality

is recorded (Low, 1968). Rice cannot be grown all year round on the Gulf

Coast of Texas because low temperatures in winter will kill the ratoons

(Evatt, 1958a,b). Declining yields and crop failure have been reported in

sorghum grown at higher elevations in Hawaii, and this has been ascribed

to low-temperature effects (Plucknett et al., 1970).



B. EFFECTO F ENVIRONMENT

O N REGROWTH

OR TILLERINC

As the regrowth system differs among crops, the effect of environmental factors will be considered in two categories depending upon whether

the plant tillers or suckers as in monocotyledons, or reproduces from

basal suckers or shoots formed on the stems or branches of the plant as in

the majority of dicotyledons considered.



I . Tillering in Grasses

Little published work exists on the effect of environment on tillering in

grasses other than in those used for pasture. However, by analogy the

work on tillering in pastures is of considerable interest. In pasture, tillers

are considered to be the primary growth unit (Mitchell, 1954; Langer,

1963) and the sward to be a community of tillers, each contributing to

total yield. This analogy is not true for crops like bananas, where control

of sucker density is maintained (Simmonds, 1960) and where satisfactory

yields depend upon adequate pruning.

The effect of increasing tiller density with successive ratoons is likely

to be a critical factor in crops such as grain, sorghum, and rice. When

these crops are ratooned the yield is likely to show an inverse relationship with density, as has been shown for several crops (Bleasdale, 1967).

In sugarcane, where there is a close relationship between total cane yield



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III. Botanical and Physiological Considerations

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