XI0.I^3'3 PORTO RICO AGRICULTURAL EXPERIMENT STATION MAYAGUEZ, PORTO RICO Under the supervision of the UNITED STATES DEPARTMENT OF AGRICULTURE BULLETIN No. 32 EFFECT OF TOPPING ON YIELD OF COFFEE IN PORTO RICO BY T. B. McCLELLAND, Horticulturist Issued June, 1928 °£pos ITo UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON 1928 PORTO RICO AGRICULTURAL EXPERIMENT STATION, MAYAGUEZ [Under the supervision of the Office of Experiment Stations, United States Department of Agriculture] E. W. Allen, Chief, Office of Experiment Stations. Walter H. Evans, Chief, Division of Insular Stations, Office of Experiment Stations. STATION STAFF D. W. May, Director. T. B. McClelland, Horticulturist. H. C. Henricksen, Agriculturist. C. M. Tucker, Plant Pathologist. R. L. Davis, Associate Agronomist. H. L. Van Volkenberg, Parasitologist. J. O. Carrero, Assistant Chemist. A. Arroyo, Minor Scientific Helper. C. Alemar, jr., Clerk. PORTO RICO AGRICULTURAL EXPERIMENT STATION MAYAGUEZ, P. R. Under the supervision of the UNITED STATES DEPARTMENT OF AGRICULTURE BULLETIN No. 32 Washington, D. C. June, 1928 EFFECT OF TOPPING ON YIELD OF COFFEE IN PORTO RICO 1 By T. B. McClelland. Horticulturist CONTENTS Page Coffee branches 1 Treatment 3 Page Effect of topping and removal of suckers 4 Conclusions 7 The question of the advisability of topping coffee trees has recently received considerable attention from coffee growers in Porto Rico. The practice varies in different countries. In Colombia and Guade- loupe, for instance, heading back of coffee trees is universally prac- ticed, whereas in Porto Rico the trees are allowed to attain full height. COFFEE BRANCHES Dimorphism of branches must be taken into account in any system of priming coffee. The subject has been treated at length by Cook. 2 A knowledge of the habit of growth of the coffee tree and of the differences between the kinds of branches is essential to a proper understanding of any pruning system practiced. The coffee seedling first produces a single upright stem. When the stem is approximately a foot high, further elongation is accompanied by the development of lateral branches. A pair arises from extra - axillary buds at the base of the topmost internode. and the three stems — the upright and the two laterals — elongate simultaneously. 1 In this bulletin the term "coffee" refers to the common type of Coffea arabica only, some other species of the genus Coffea requiring wholly different treatment from that recommended for Arabian coffee. 2 Cook, O. F. dimorphic branches in tropical crop plants: cotton, coffee, cacao. THE CENTRAL AMERICAN RUBBER TREE. AND THE BANANA. U. S. Dept. Agl\. Bill*. Plant Indus. Bui. 19S. 64 p., illus. 1011. T6231— 2S 1 2 BULLETIN 3 2, PORTO RICO EXPERIMENT STATION (Fig. 1.) Thereafter a pair of laterals will develop in like manner at the base of most new internodes of the upright stem as this con- tinues growth, but occasionally one or more internodes may be skipped or a single lateral may develop instead of a pair. If a primary 1 IMF y' *^*» .N L* &■ W ^m 1 9 ^ . ^^BB HBJ .'Si ■*■■ «^w*^B b^^ ■ 1 B 7 ^0^ ■Ik. '^B ■P^^ati ■kg. ^"*\ •**^B Fig. 1. — A, simultaneous development of the primary lateral branches and the upright stem ; B, position of new uprights, developed from buds immediately below the primary laterals lateral be removed the loss is permanent, as the upright stem can replace no lost lateral. However, in the axils of the leaves and just below each lateral branch on the upright stem are buds from which there may develop new upright branches similar in structure and habit of growth to the original stem. In this way only can addi- EFFECT OF TOPPING OX YIELD OF COFFEE 6 tional primary laterals be produced. The normal function of lateral branches is to produce fruit and only occasionally is any fruit pro- duced on an upright stem. In addition to producing fruit, primary laterals may also produce from axillary buds secondary lateral branches, which are similar in function to the primaries. When growth is allowed to take its normal course, the original upright trunk bends under the weight of a heavy crop and various new upright branches develop from the axillary buds. These are similar in structure to the original stem, developing primary laterals, which in turn produce fruit. The tendency to develop secondary laterals varies somewhat with the variety, but on ordinary Arabian coffee, the growth of which has been unchecked by topping, the amount of secondary lateral growth is not very great. In conse- quence, by far the larger part of the crop is normally produced on primary rather than on secondary laterals. If upward growth is checked by topping and by the removal of new uprights as they appear, the production of secondary laterals on the primaries is greatly stimulated, and a large amount of such growth develops. For all practical purposes only flowers, fruit, and secondary lateral branches ma}' be expected to develop from the primary laterals, though observations at the station revealed two instances in which this failed to hold true. A tree which was topped at 4 feet in December, 1910. and the growth of which was forced into the laterals by the removal of all subsequently developing uprights, was observed in May. 1916, to have developed three "upright* branches from near the tip of a primary lateral. Their structure was that of the up- right, not the lateral, and their lateral branches were in pairs and arose from extra-axillary buds. The position of these " upright * branches was more nearly horizontal than perpendicular and one showed a marked tendency to produce laterals in a somewhat hori- zontal plane. In 1918 a second, tree was noted with several similar uprights arising from a lateral. These uprights were rather spindling and lacked the vigor of the normal upright. Although in the case of neither tree was the development that of the wholly nor- mal or typical upright, it partook more of the nature of the upright than of the lateral. TREATMENT The field selected for testing the effect of topping contained 161 trees at the beginning of the experiment in December, 1910. These had been set in the summer of 1908. The size of the seedlings at transplanting time was such as to indicate that the seed had been derived presumably from the 1906 crop. The variety was Blue Mountain of Jamaica, typical of the ordinary Coffea arabica and indistinguishable in appearance and habit of growth from the Porto Rican variety. The trees were set in 24 short rows of unequal length. Rows 1 and 2 were left untopped, rows 3 and 4 were topped at 6 feet, and rows 5 and 6 at 4 feet. In the same alternating sequence the remaining 18 rows were similarly treated. The first of each of the four pairs of untopped rows received no pruning whatever, all suckers and growth BULLETIN" 3 2, PORTO RICO EXPERIMENT STATION" of every kind being allowed to develop freely. In the second row in contrast to the first, all uprights or suckers developing along the main stem were removed, thus holding the growth to the single original stem or trunk and developments from its laterals. Topping forced the growth of many new uprights or suckers. These were removed from time to time, thus holding the growth to the single - topped stem and branches developing from the laterals. The first pruning was given in Decem- ber, 1910. During the next six years the suckers were removed from the trees from 3 to 5 times annually, and during the fol- lowing five years from 2 to 3 times annually. The trees w ere young when they were topped and therefore well sup- plied with primary laterals. Figure 2 shows the condition of one of the better developed trees sev- eral months before the first priming. This tree was 8 feet high and carried 42 lateral branches, the middle ones being more than 3 feet long. Some other trees had developed less rapidly and at the time of the first priming lacked the necessary height for topping. These were subse- quently topped as their growth permitted. EFFECT OF TOPPING AND REMOVAL OF SUCKERS The appearance of the topped trees at four years after topping is shown in Figures 3 and 4. The dense mass of foliage is attractive to the eye. The picking of the crop is greatly facilitated through the production of the fruit on low branches within easy reach of the pickers. Fig. 2. — Coffee tree which carried 42 branches and more than 1,500 cherries. Photographed in September, 1910, prior to pruning EFFECT OF TOPPIXG OX YIELD OF COFFEE 5 The yield of the trees was recorded over a 10-vear period. 1912- 1921, the first record being taken at a little less than two years after the first pruning. The depressing effect on production exercised by severe pruning or topping was less evident in the early years of the test than later. In the three-year period, 1912-1914. both the trees Fig. 3. — Topped at 6 feet December, 1910, and photographed August, 1914 which were held to a single trunk and those which were topped at 6 feet produced each year within 10 per cent of the production of the unpruned trees. Table 1 shows the average annual production of coffee cherries per tree as affected bv pruning for the period 1912-1921. 6 BULLETIN 3 2, POETO EICO EXPEEIMENT STATION ^ -^ so 00 CO "O i-H c3 K. . . . . -*-2 »1NOO(0 O ~ IN (N N •-< h H i OS CN i fe"3-2 i o « 3 X) o CO 60 eS •— CO > o CN OS CO 53 CO 02 1— I OS CO i ^ bo co 3? £3 O I a. ?2 p CO XJ O CO 60 a !-, CO > < If T— I OS CO 1— I OS CN OS t o os o Tt< ; co <-h CN i-i ,_, ^ OS CN 00 r-1 h © co co © gXJ O 1 ■£! CN i-l H H 2 o-s'o ^ p. 2 oc 00 CN CO CN K , • • ■ V CN 1-1 l"H M toNiOOiOO Co 00 —H © CN s- . . . . o S co t^ co o -Cf< S(N>ON ^> ^ i^ CO S to co co «J CO CO Tt< S CT> 02 00 o ^ t^ 00 CO VCDCO^f S tJH CN CN ^ O C3 C75 ff OS ^cH CO « O O 00 CJ i— I i— I Scoo ^> i— I OS 00 a 3 CO , — I — ' «- 60 CO CO co co ^ -gcacs Q, CO CO oftfl floo •V c3 CO D< E C£ CO 3 co >> CN 3-t2 ^ I- ^ ® >, ° CO _ *« £, *° 3 S? 3' 35 .S ea co 3 3 a>, mT3 co O 3 STJ 3 5g a o cs .y co m 3 g g.H co D. co t? S o fc - 60*^ O .3-3 3 CO C3 o g . 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