PAPER CANELAND CULTIVATION IN MAURITIUS A. NORTH COOMBES. Agronomist, Department of Agriculture, Mauritius

Transcription

1 Double planting gave a total tonnage of cane per cent higher than single planting, the increment being statistically significant. As might have been expected, the increment was secured mainly in the first five weeks of growth and, to a lesser extent, in the second five weeks. The higher mortality in the doubleplanted plots was not sufficient to offset the marked superiority of these plots in number of stalks per acre. The tonnage of late shoots was practically identical for the two types of planting, although the double planting averaged 998 stalks per acre more (table 2) than the single. In table 6 certain other effects of the two types of planting are compared. It will be seen that single and double planting had no statistically significant differential effects on the juice purity, the sucrose content of the cane, the glucose ratio or the weight per stalk. In the case of length per stalk, the double planting tended to produce longer first and second order stalks, and in the late stalks the difference in favor of double planting was statistically significant. A paper by A. N. Coombes was presented by Dr. Schreiner. PAPER CANELAND CULTIVATION IN MAURITIUS A. NORTH COOMBES Agronomist, Department of Agriculture, Mauritius Sugarcane was introduced into Mauritius in 1650, but it was not until one hundred and seventy-five years later, i.e., about 1825, that it began to be cultivated on a large scale and gradually assumed the position which it holds today in the economy of the island. For over a century successive generations of planters have grappled with the crop, and the methods of cultivation now in vogue are the result of long experience coupled with keen observation and a progressive scientific outlook. The methods briefly described in this paper refer exclusively to "estate" cultivation. In order fully to appreciate the "raison d'etre," it is necessary to consider briefly the conditions under which the cane is cultivated in various parts of the island. For the present purpose the cane lands of Mauritius may be divided into three broad groups, as follows: (a) the northern and coastal areas* characterized by a low altitude and a deficient water-supply, (b) the Black River area where the crop depends almost exclusively on irrigation, and (c) the southern, eastern and central areas where the natural water-supply increases with altitude to a point beyond the optimum. A further point to be considered is the nature of the soil. Broadly speaking, there are large areas of both stony and gravelly soils and of soils altogether free from stones. The soil is lateritic in formation, the degree of laterisation increasing with rainfall. As a rule, except for some stony lands, the arable soil layer is * Parts of this area are irrigated.

2 thin and, underlying it, is a stiff, sterile subsoil deficient in all plant food elements but particularly poor in phosphates. Stony soils are generally richer in plant food content being geologically immature, while soils free from stones are mature. Stony soils, however, present the practical difficulty of the stones having to be removed before the land can be prepared for planting. Caneland cultivation in Mauritius is characterized by the following factors: 1. Absence of pre-planting cultivation. 2. Exclusive dependence on cheap labor. 3. Abundant use of pen-manure in plant canes. 4. Return to the soil of all available residues. 5. Long ratoonage. 1. Absence of $re-planting cultivation. Owing to the stony nature of many areas, the soils have to be "de-stoned" prior to planting. While there are various ways of disposing of the stones, the general tendency nowadays is to build stone walls along the interlines of canes-along every alternate, third, fourth or fifth interline according to the quantity of stones present and the soil type. When every alternate interline is covered-the commonest means of getting the stones out of the way-one-third of the surface is covered over with stones and will not receive any cultivation whatsoever for a period of six to eight years, i. e., until the field having to be replanted, the stones are moved. Holes (furrows being but rarely opened) are then dug along rows separated from each other by a distance of 44-5 feet, center to center. Stones found embedded at the bottom of the holes are then removed with the crow-bar, and the bottom, on one or two estates, is forked sometime before planting. With very few exceptions the plow is never used; even where there are no stones and where implements are worked, the whole surface is never plowed nor is it cultivated in any other way before planting. 2. Exclusive dependence on cheap labor. The Mauritian sugar industry depends exclusively on hand labor of East Indian origin permanently established in the island. Mechanical cultivation has made no headway for a variety of reasons, the chief of which are: cheap and abundant labor supply, stony soils, nature and proximity of underlying subsoil and topography. Over the largest part of the sugarcane lands every operation is hand done. However, should labor ever become scarce or expensive, there is little doubt that other difficulties will be overcome, at least in part, and mechanical implements introduced wherever possible. 3. Abundant use of pen-manure in plant canes. The local method of applying pen-manure to plant canes at planting and also four to six months later is several decades old. The total quantity of manure used varies between 22 and 30 tons per acre of which about one-third or one-fourth goes in at planting. This liberal treatment with pen-manure does not preclude the use also of artificial fertilizers of which plant canes receive larger quantities than ratoons. There has been a tendency of late, in some parts, of applying pen-manure at planting only, while a few planters are paying considerable attention to applying increased amounts of fertilizers in the place of a large part, if not all, of the pen-manure.

3 In the north of the island, 6-10 tons of pen-manure are given per acre at planting and tons six months later. The second dose, however, is often replaced by 8-15 tons of a compost of filter-press muds, bagasse, molasses, ashes and sand in varying proportions known as "saccharogcne." In other localities, an application of 5-10 tons of pen-manure per acre at planting is followed by another of tons three to five months later. Whenever available, however, scums or "saccharogene" are now preferred for planting, the usual dose averaging about 3 tons per acre although up to 6 tons are sometimes given. 4. Return to the soil of all available residues. For several decades it has been customary in Mauritius to return all possible residues-trash, scums, furnace ashes, molasses-to the fields. As shown in the preceding paragraph, scums, ashes and molasses form part of a compost used to fertilize plant canes. Scums are also used alone at the rate of 3 tons per acre, being given almost exclusively to plant canes, usually at planting. Molasses is applied in so many different ways that it is impossible to generalize. In plant canes it is applied either in the holes about a fortnight before planting or in the interlines when the cane is three to six months old. It is also applied to manure or "saccharogene" at planting or later. Sometimes also the trash left from the last ratoon crop is composted with molasses before the field is replanted and is turned under when the second application of manure is made to the young canes. In the North, molasses is not given to virgins as such except via manure when the canes are a few months old. Molasses is also used in ratoons and in humid places is poured directly on the stools. In the dry places, it is spread either on the lined-up trash or on the interlines beneath the trash. As to the category of ratoons treated with molasses, practice again varies much. Some planters apply to first ratoons, others to second, third or fourth ratoons, older ratoons being seldom, if ever, treated. The more usual dose of molasses whether to plant canes or to ratoons is four tons per acre, but the quantities given vary from two to ten tons, the heavier doses constituting a recent departure from established practice. With regard to trash, it is nowadays never burnt but is usually lined up on alternate inter-rows. It is also to a smaller extent disposed of by burying in furrows dug in every other interline after the crop has been cut. There is a slowly growing tendency to spread the trash over all the interlines after the usual ratoon cultiv&ion is completed. While not a residue, mention may be made here of the practice of turning in a green manure crop taken between two cane crops. The green crop is always a legume: Mucuna deeringiana being grown in the South, and Phaseolus lunatus being preferred in the North where longer resting periods (8 months to 3 years" as against 5-6 months in the South) are lavorecl. Wherever the green crop cannot be turned under it is carted to the manure heap. Canavalia ensiformis is widely grown as an intercalary green manure between cane rows, being sown just after # The tendency is towards a reduction of this period.

4 I planting the cane. The green material is buried at the time when the second dose of pen-manure is applied. 5. Long ratoonage. It has always been customary in Mauritius to take as many ratoons as possible. As early as the 'forties' it was usual to replant cane fields every five years. The number of ratoons cropped has of course varied from time to time, according to various influences, resulting in the practice followed today of growing up to fifth ratoons in the North and lower parts, while in the elevated regions it is usual to replant after sixth or seventh ratoons. In some places it is not unusual, with very good cultivation, to produce eighth and even tenth ratoons on an economical basis. The growing of such old ratoons only became a possibility when cultivation reached a high degree of perfection as a result of the methods employed in building up fertility in the soil. As ratoon canes are produced more cheaply than plant canes (as a matter of fact, plant canes often show but a meager profit, if any), every endeavor is made to delay replanting as long as possible consistent with sound cultivation and profitable management. Plant canes in the North and at Black River are planted between April and July, while in other parts the planting season extends from September to March according to altitude and the cane varieties grown. The White Tanna cane, which is still largely cultivated in the wet central regions, is planted early to be cut months later; other varieties require a shorter growing period, about months. The above are classed as "long-season" canes. To a much smaller extent "short-season" canes are also grown being planted about September to be cut 14 months later. Pen-manure or "saccharogene" is placed directly in contact with the sets, either just above or beneath them according as to whether the locality is dry or humid. Phosphatic guano is also applied in the holes at planting at the rate of kilos per acre. When the canes are from 6-8 weeks old, kilos of fertilizers (usyally a mixture of sulphate of ammonia and nitrate of potash) are applied directly on the stools. The fields are maintained dean and pen-manure is applied again 4-6 months after planting. The soil is dug out from around the stools to make place for this manure and, after this operation, which coincides with a further and often larger application of fertilizers (either a complete mixture or one containing sulphate of ammonia and nitrate of potash only), plant canes are forked or cultivated with the hoe in the intcrlines. Long season canes often receive a third dose of fertilizers, mostly nitrogenous, the following December or January. Thereafter weeds are kept down and the canes are stripped twice before the field is ready Lo be harvested, the second stripping being done just prior to cutting the canes. CULTIVATION OF RATOON CANES As soon as possible after cutting, the trash is lined-up or buried on alternate interlines, the uncovered interlines being forked. Forking is restricted to the first

5 two or three categories of ratoons only. Molasses is applied on the stools or in the interlines as described earlier in this paper. Fertilizers are also spread on the stools prior to earthing-up which is considered the most important operation in ratoon cultivation; every effort is made to complete this work before the end of December,* i.e., at the time when the summer rains set in and when the temperature is high. In connection with fertilizing ratoons, it must be mentioned that first ratoons often get an extra dose of nitrogen just after virgins are cut; subsequently they receive the same treatment as other ratoons, but the older ratoons almost always get smaller quantities of fertilizers. Moreover, while the younger ratoons are given complete fertilizers, this is rarely the case with the oldest ratoons which receive nothing but sulphate of ammonia or a mixture of sulphate of ammonia and nitrate of potash. Except in the North, ratoons are usually stripped prior to harvest. Before concluding, a word or two may be said about the more recent advances made in cane cultivation in Mauritius of which the following will be mentioned: the trial and spread of better cane varieties, a tendency to reduce the quantity of pen-manure applied coupled with an increase in the amount of fertilizers, soaking the cuttings in a saturated solution of lime overnight, the application of coral sand to cane soils, the more extended use of the fork in both plant and ratoon canes, subsoiling to about 18 inches depth. A few other items could be mentioned but they are still in the experimental stage; however, the distribution of fertilizers partly on the stools and partly on the interlines deserves special mention. A paper by Takashi Fukuchi was presented by Dr. Schreiner. PAPER INTERPLANTING OF SUGARCANES TO PADDY RICE B TAKASHI FUKUCHI Government Sugar Experiment Station, Tainan, Formosa I In Formosa, sugarcane production depends largely upon the peasant farming, which comprises eighty per cent of the total acreage of cane. Consequently, the cultivation of cane, so far as it concerns land utilization in general, is intensive. Farmers are commonly very diligent and anxious to raise more crops per unit area, and therefore, canes are not infrequently cultivated with other companion crops. In the uplands, for instance, sweet potatoes or peanuts are often raised as an intercrop when canes are young, and recently cotton has come to be another intercrop in cane. The most intensive one among these, however, is the companion cropping of rice and cane, in which canes are interplanted to paddy