THE EFFECTS OF PHOSPHATE AND LIME APPLICATIONS ON

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1 FLORIDA STATE HORTICULTURAL SOCIETY, 9 progress with citrus trees growing on alkaline calcareous soils. Summary Several different zinc sources were applied alone and in combination with one or more other materials to the soil around orange trees growing on acid sandy soil. Methods of appli cation were as follows: () broadcast, () spot application in either or square-foot piles per tree, () smaller piles per tree, () application in holes of one square-foot cross section and inches deep, and () application in narrow bands. Zinc sources used included zinc sulfate monohydrate ( percent zinc), zinc chloride, zinc nitrate, zinc oxide, and two zinc chelates. All zinc sources applied alone were ineffec tive in substantially increasing zinc uptake by the trees regardless of method of application, although increases of to ppm zinc in the leaves were obtained in a few cases with or pounds of zinc sulfate per tree. A mixture of five pounds each of zinc sulfate and calcium chloride applied to Lakeland sand in piles each of one square-foot area or smaller piles increased the leaf zinc to levels of to 9 ppm, as compared with ppm in the untreated check trees. Preliminary results from application of this mixture in five piles per tree in 9 resulted in leaf zinc levels higher than ppm. A mixture of zinc chelate with soda ash ap plied in piles or in a narrow band in sufficient amounts to raise the soil ph to about. in the treated areas also resulted in very high concentration of zinc in leaves. All broadcast applications of zinc sources were ineffective. LITERATURE CITED. Alben, A. O. 9. Preliminary results of treating Rosetted Pecan Trees with Chelated Zinc. Proc. Amer. Soc. Hort. Sci. : -.. Barrows, Harold L, Matthew Drosdoff, and Armin H. Gropp. 9. Rapid Polarographic Determination of Zinc in Plant Ash Solutions. Agr. and Food Chemistry : -.. Benson, N. R., L. P. Batjer, and I. C. Chmelir. 9. Response of Deciduous Fruit Trees to Soil Applications of Zinc Chelate. Symposium on the Use of Metal Chelates in Plant Nutrition (Edited by Arthur Wallace, U.C.L.A., Los Angeles) pp. -.. Blackmon, G. H. 9. Pecan Variety Response to Different Soil Types, Localities, etc. Fla. Agr. Exp. Sta. Ann. Rept., pp. -.. Blackmon, G. H. and R. D. Dickey. 9. Zinc as a corrective for little-leaf of Peach in Florida. Proc. Fla. State Hort. Soc. : -9.. Brusca, Joseph N. and A. R. C. Haas. 9. Zinc Effect in Citrus and Avocado. Calif. Citrograph : - (August).. Camp, A. F. 9. Studies on the Effect of Zinc and other Unusual Mineral Supplements on the Growth of Horti cultural Crops. Fla. Agr. Exp. Sta. Ann. Rept., p... Gustafson, C. D. 9. Zinc Soil Treatment on Avo cados. Calif. Citrograph : Leonard, C. D., Ivan Stewart, and George Edwards. 9. Effectiveness of Different Zinc Fertilizers on Citrus. Proc. Fla. State Hort. Soc. 9: -9.. Parker, E. R. 9. Effect of Zinc Applications on the Crop of Grapefruit Trees Affected with Mottle-Leaf. Hilgardia : -.. Stewart, Ivan, and C. D. Leonard. 9. Use of Che lates in Citrus Production in Florida. Soil Science : -9.. Stewart, Ivan, C. D. Leonard, and George Edwards. 9. Factors Influencing the Absorption of Zinc by Citrus. Proc. Fla. State Hort. Soc. : -.. Stewart, Ivan, and C. D. Leonard. 9. Use of Iso topes for Determining the Availability of Chelated Metals to Growing Plants. Peaceful Uses of Atomic Energy (Proc. Intern. Conf. in Geneva, August, 9) Vol. : 9-.. Wallihan, E. F., T. W. Embleton, and Wilma Printy. 9. Zinc Deficiency in the Avocado. Calif. Agriculture (June), pp. -. THE EFFECTS OF OSATE AND LIME APPLICATIONS ON GROWTH, W. F. Spencer Florida Citrus Experiment Station Lake ROOT DISTRIBUTION, AND FREEZE INJURY Alfred Phosphates and limestone have been applied to citrus groves in Florida for many years. Wander (9) postulated that calcium phos phate accumulations may be helpful in re taining magnesium and manganese in sandy soils planted to citrus. Consequently, an ex periment was initiated in 9 to evaluate the effect of calcium phosphate accumulations from phosphate and lime additions on soil Florida Agricultural Experiment Station Journal Series, No. 9. OF YOUNG GRAPEFRUIT TREES properties and the resultant effect on growth of grapefruit trees. This paper reports the effect of the various phosphate and lime treat ments on tree growth, root distribution, soil ph, and cold injury to the trees during the severe winter of 9-. Other aspects of treatment effects will be reported in a separate paper. The literature concerning the role of phos phorus in citrus nutrition has been recently reviewed by Smith and Reuther (). There fore, only a few pertinent references will be mentioned here. Reuther, et al. (, ) did not obtain yield increases from phosphate ap plications to oranges growing on inorganic

2 SPENCER: OSATE-LIME STUDIES sandy soils at two locations in Florida. They reported depressed growth of Valencia orange trees, as measured by percentage increase in cross-sectional area of trunks, due to their medium and heavy phosphate treatments. In one of these same experiments, Smith () later found that phosphate fertilization caused a reduction in the quantity of the feeder roots in the surface foot of soil. Ford () also re ported a reduction in root growth associated with the higher rates of phosphate applied in a Pineapple orange block at the Citrus Experi ment Station. Forsee and Neller (9) reported increases in tree growth and yield of oranges from the application of various phosphatic ma terials to orange trees growing on the organic soils of the eastern Everglades. Experimental Methods The experiment reported here was carried out with Ruby Red grapefruit trees on rough lemon rootstock planted April 9, on a pre viously uncropped Lakeland fine sand at the Citrus Experiment Station. As outlined in Ta ble, the treatments encompass a wide range in rates of phosphate and limestone, applied separately and in combination. High calcium limestone was the source of liming material and triple superphosphate was the source of phosphate. Each plot is by feet, and consists of four "record" trees which are com pletely surrounded by buffer trees. The dif ferential treatments were applied to the entire area of each plot in three equal applications each year beginning in July 9. The experi mental design was a randomized block with three replications. All trees were fertilized with a -O---I-J fertilizer broadcast, with a fertilizer distributor three times each year at the rate of pounds per acre per application. The nutrients in this fertilizer mixture were from the follow ing materials: nitrogen & from ammonium sulfate and J from sodium nitrate; potash and magnesium from sulfate of potash-magnesia, with the remainder of the magnesium from magnesium sulfate; manganese and copper from their respective sulfate salts. The trees have received a zinc nutritional spray each year and a copper spray for melanose control each year since 9. Tree size was evaluated in August 9 by measuring tree height, trunk circumference, and periphery of the branches the circum ference of the tree drip margin. Tree height was measured with a -foot surveyor's rod. Table. The effect of phosphate and lime applications on size of five-year-old Ruby Red grapefruit trees. Treatment Tree Trunk Periphery Number po Limestone height, feet circumference, inches of branches, feet Avg. P + Avg. lime lime only Avg. P only L.S.D» (Treatment means) L^S.D.#, (Lime only vs. P)

3 FLORIDA STATE HORTICULTURAL SOCIETY, 9 Trunk circumference was measured with a flexible tape approximately inches above ground level. Periphery of the branches was calculated from the spread of the branches measured in an east-west and a north-south direction. Root concentration or density was measured by the method published by Ford (). One hole inches in diameter was dug at the drip margin of each tree, and all the feeder roots removed from each depth zone were dried and weighed. Roots less than approximately / millimeters in diameter were considered feeder roots. The effect of the treatments on freeze in jury during the winter of 9- was evalu ated by weighing the deadwood pruned from the trees in April 9. The trees also were rated December 9, 9, for relative degree of freeze damage to foliage caused by the first freeze of the winter on the night of Decem ber -. Soil samples were obtained at various depths from the surface to feet August, 9. Since soil reaction is of interest to many growers, the ph of the soil samples, as deter mined in a : soil: water suspension, are re ported here. Other soil analyses will be re ported elsewhere. Results Tree growth. Tree size measurements are presented in Table. By all methods of meas urement, the trees receiving phosphate alone, or in combination with limestone, were signifi cantly smaller than trees receiving limestone only. Statistical analysis indicated that essen tially all the variation in growth was accounted for by variations in the phosphorus versus nophosphorus treatments. Hence, the major dif ferences in growth occurred between the trees receiving phosphate (alone and in combination with limestone), and the trees receiving lime stone only. Differences in growth among rates of P,O ( to pounds per acre) or among rates of limestone ( to pounds per acre) were not statistically significant. Comparing the growth of trees receiving lime only with trees receiving phosphate only and phosphate plus lime, there was an increase of.9 percent,. percent, and. percent in tree height, trunk circumference, and peri phery of branches, respectively. Table. The effect of phosphate and lime application on feeder root concentration at various depths.i' Treatment Depth, inches Number PO Limestone gnu.. Avg. P + lime b Avg. lime only b Avg. P only , [j.s.d.^, gms i'root concentration expressed as grams of dry feeder roots in a foot square column of soil the height of each zone.

4 SPENCER: OSATE-LIME STUDIES 9 Trees growing in the untreated check plots were smaller than trees in the treated plots. Leaf symptoms and analyses of leaves indi cated that trees in the check plots, with no limestone or phosphate additions, were very deficient in calcium. This apparently accounted for their smaller size. Root Concentration. Phosphate applications markedly reduced the concentration of feeder roots in the surface foot of soil (Table ). The effect of phosphate on root concentration was greater in the --inch zone, where phosphate concentration was highest, than in the -- inch zone. Comparing all non-phosphated plots with all plots receiving phosphate, there were seven times as many roots in the --inch zone of the non-phosphated plots as in plots receiv ing phosphate. Differences in root growth in the surface inches due to increasing rates of phosphate were not statistically significant, al though the root concentration tended to be lower at the higher rates of phosphate. How ever, the higher rates were much more effec tive than the lower rates of phosphate in re ducing root concentration in the deeper zones. This is due to much greater downward move ment of phosphorus at the higher rates of ap plication. The highest rate of phosphate caused a statistically significant decrease in root con centration to a depth of inches, and the effect was appreciable at the maximum depth of sampling. The data indicate that the detrimental ef fect of phosphorus on root growth was not lessened by lime applications. This alone would tend to discount any free acid or ph effect of the applied triple superphosphate as a contributing cause of root damage. There was a tendency for the root concen tration, especially in the deeper zone, to be less at the high rate of lime than at the two lower rates of lime. Freeze Injury. Trees receiving phosphate were more severely injured by the cold tem peratures during the winter of 9- than trees not receiving phosphate. Freeze damage to the trees varied due to differences in eleva tion in the grove; however, in all locations where phosphated and unphosphated plots were adjacent, the phosphated trees suffered considerably more from freeze damage than the unphosphated-limed trees. Figure is a diagram of the experimental plot with the FIGURE. DISTRIBUTION OF FREEZE INJURY AS AFFECTED BY LIME AND OSATE TREATMENTS <l Po Lo P* L. Pf L* Po L» Po Lo P Lo P, Lo P. L, P LJ PL Pt Li Pi Lo Po L PL Po L P. L, Po L PLo PaLo P. Le <l THE UPPER NUMBER IN EACH SQUARE IS THE POUNDS DEADWOOD PRUNED PER TREE Po.P,, P, P, REFERS TO P AT THE FOLLOWING RATES:,, AND LB. / A, L,L,, L, L, REFERS TO LIMESTONE AT THE FOLLOWING RATES! %,. AND LB./A amounts of deadwood pruned from the trees indicated on the diagram. Figures and illustrate the difference in freeze injury be tween trees in adjacent plots receiving lime only and lime plus phosphate. Freeze damage to the foliage of the trees was rated December 9, 9, following the first freeze which occurred the night of De- Fig.. Tree receiving limestone, but no phosphate, at the rate of pounds per acre per year. Three pounds of deadwood pruned from this tree in April 9. Higher rates of limestone resulted in similar trees. Stake is feet high...

5 FLORIDA STATE HORTICULTURAL SOCIETY, 9 by the cold temperatures than unphosphatedlimed trees, wherever they occurred in adja cent plots in the experimental grove. Fig Tree in adjacent plot receiving limestone and phosphate at rates of, and pounds per acre per year, respectively. Nineteen pounds of deadwood resulting from freezes of 9- pruned from this tree in April, 9. cember -. The effect of the various rates of phosphate and lime on freeze injury, as measured by loss of wood and relative foliage damage scores, are presented in Table. A comparison of the treatment averages pre sented in Table is not nearly as striking as a visual comparison of trees in adjacent plots in the field. Likewise, the amounts of deadwood pruned from trees in one of the highphosphate plots (-A) do not reflect the actual severity of damage, since the trees sub sequently died. Due to variability of the freeze damage between locations in the grove, the differences between relative foliage damage scores were not significantly different. How ever, a highly significant correlation (r=.) existed between the ratings of foliage damage and amounts of deadwood loss. This high de gree of correlation indicates that a good pro portion of the freeze injury to the trees pos sibly occurred during the first freeze Decem ber -, 9. The data indicate a tendency for the freeze damage to be more severe at the higher rates of phosphate. However, trees receiving the lower rate of phosphate were damaged more Soil ph. Soil ph was greatly increased by lime additions (Table ). The ph was in creased more by lime without phosphate than lime with phosphate. However, comparing the ph in the unlimed-unphosphated check with the phosphate-only treatments, the phosphate additions resulted in a surface soil ph approxi mately. ph unit higher than the untreated check. Thus, the effects of phosphate applica tions were to decrease the ph in the presence of lime and slightly increase the ph in the absence of lime. The effects of the highest rate of limestone, both with phosphate and without phosphate, were apparent to depths of at least four feet the maximum depth of sampling. The - pound annual rate of limestone had increased the ph of the --inch zone from to. and maintained the ph of the --inch zone approximately. ph unit higher than the untreated check, i.e.,. as compared to. All rates of limestone were effective in main taining a subsoil ph higher than phosphateonly to a depth of at least inches. Below inches only the higher rates of limestone were effective in increasing the soil ph above that of the phosphate-only treatments. An examination of the root distribution and soil ph data in Tables and indicates no relation between soil ph and feeder root con centration in the soil. Root concentration in the untreated check plots, which have the lowest ph, was as high as the root concentration in the plots receiving lime without phosphate. This would rule out any simple relationship between ph and root growth. Discussion The results indicate that phosphate applica tions to Ruby Red grapefruit trees decreased tree growth, decreased root concentration, and increased susceptibility to cold injury. The mechanism of these effects, or the reason for their occurrence, is not definitely known. The primary, or most direct, effect of phosphate was undoubtedly on root growth, which in turn resulted in a smaller tree in a poorer condition to withstand freezing temperatures. Lawless () studied freeze damage to citrus trees in relation to grove practice and con-

6 SPENCER: OSATE-LIME STUDIES Table. The effect of phosphate and lime applications on freeze injury to -/-year-old Ruby Red grapefruit trees during the Winter of 9-. Treatment Deadwood, Foliage Number PO Limestone lb./a, lb./tree!/ damage^' Avg. P + lime Z. 9 Avg. lime Avg. P only only L.S.D i'deadwood pruned in April 9. /Daraage to foliage rated December 9, 9, following the freeze of December H-, 9. Scores were based on percentage of leaves damaged as follows:. Less than percent. # percent.. percent.. percent.. More than percent. eluded "that the extent of cold damage is a reflection of tree condition which is deter mined by the proper or improper use of tree nutrients." Some workers (,,, 9,,,) have reported a depression in uptake of minor elements, especially copper and zinc, due to phosphate fertilization. Leaf analyses from trees in this experiment, not reported here, in dicated that phosphate did decrease the up take of some elements, but none were de creased to a deficient level. Growth-depressing effects of high levels of phosphate have been found by a number of workers. For example, Rossiter () in Australia reported that phos phate applied as monosodium phosphate at rates equivalent to only to pounds superphosphate per acre, depressed the growth of subterranean clover and oats grown on Muchea sand in pot culture. The source of phosphate in this experiment was triple superphosphate. There is no ex perimental evidence in the literature to indi cate that the results would have been different if any other source of water-soluble phosphate had been used. Depressed root growth of citrus trees due to phosphate reported by Smith () and Ford () and depressed growth of Valen cia trees reported by Reuther et al. (, ), were brought about by the application of ordi nary superphosphate. Neller () studied dif ferent sources of phosphate for Everglades peat (a soil with a phosphate-fixing capacity of the same magnitude as Lakeland sand). He found that growth and yield of sugar cane,

7 FLORIDA STATE HORTICULTURAL SOCIETY, 9 Table. The effect of phosphate and lime applications on soil ph at various depths.i' (Sampled --.) Treatment Depth, inches Number P Limestone ph Each value is an arithmetical mean of three replications. Table. The amount of phosphorus applied in the fertilized area of young citrus trees based on the application of an percent PO fertilizer material at the rate of one pound of fertilizer per application per year of tree age. Year grove in Diameter lertiiized ft. of area, Applications per year Fertilizer rate, lb./applic./tree PO applied in fertilized area Yearly, -year total.,,,,,,9, corn, and sorghum were adversely affected by too much soluble superphosphate. Ordinary superphosphate and triple superphosphate were equally effective in reducing yield in his experiments. The fact that the phosphate effects noted herein were not altered by the simultaneous application of limestone with triple superphos phate would indicate that the effects were not due to the acidifying nature of triple super phosphate or the chemical form of phosphate present in the applied material. The limestone was mixed with triple superphosphate before application; thus, any free acid would have been neutralized by the lime before it came in contact with the tree roots.

8 SPENCER: OSATE-LIME STUDIES Several studies (,,, ) have shown that applied phosphates have accumulated in sandy soils within the rooting zone of citrus trees, even though significant quantities may move from the surface inches of the soil. Many older groves contain large quantities of phosphorus from previous fertilizer additions. The effect of this accumulated phosphorus on performance of mature trees has not been con clusively evaluated. The usual practice of ring-fertilizing young citrus trees results in a very high application of phosphate in the area fertilized. Data in Table illustrates phosphate accumulations resulting from the application of an percent PoOr. material at the old formula rate of pound of fertilizer per tree per year of age (). Calculations of phosphate accumulation in the fertilized area resulting from fertilizers con taining other than percent PO, or applied at different rates of application, can be calcu lated from the data presented in Table. For example, if a percent PO material were ap plied at the rates outlined in Table, the amounts of PO applied in the area fertilized would be one-fourth as large as those indi cated. Consequently, in order to decrease the concentration of applied phosphate to a rea sonable level, the rate of application must be lowered as well as the percent PO in the mixture. From these calculations it can be seen that many growers are applying exceedingly high rates of PO to the root area of their young citrus trees. The rates of phosphate many growers are applying are equal to the medium to high rates of phosphate application in the experiment reported herein. Thus, one might conclude that the amounts of phosphate being applied to young citrus trees are unnec essarily high and may be detrimental. In contrast with the effects of phosphate, there was a noticeable lack of effect of high rates of limestone on tree growth or freeze injury. There were no symptoms of injury due to overliming as described by Floyd () and others. This indicates that it is difficult to induce this type of injury when all essential nutrients are adequately supplied. Summary A wide range in rates of phosphate and lime stone were applied, separately and in combi nation, to Ruby Red grapefruit trees growing on previously uncropped Lakeland fine sand at the Citrus Experiment Station. The effect of treatment on tree growth, root concentration, freeze injury, and soil ph are reported herein. Tree growth was evaluated by measuring the height, trunk circumference, and periphery of the branches when the trees were just over five years of age. By all methods of measure ment trees receiving phosphate alone, or in combination with limestone, were significantly smaller than trees receiving limestone only. Phosphate applications markedly reduced the concentratio nof feeder roots, especially in the surface foot of soil. Reductions in root growth were noted in deeper zones at the highest phosphate rate. Trees receiving phosphate were more se verely injured by the cold temperatures during the winter of 9-, than trees not receiving phosphate. The average amounts of deadwood pruned from the trees were.,., and.9 pounds per tree, from plots receiving lime stone only, phosphate only, and limestose plus phosphate, respectively. The effects of high rates of limestone on soil ph were apparent to depths of at least four feet. Phosphate applications decreased ph in the presence of lime, but increased it when applied alone. Acknowledgments The writer wishes to express his sincere appreciation to Dr. I. W. Wander, former Soil Chemist at the Citrus Experiment Station, who was instrumental in initiating the experiment; Dr. H. W. Ford who assisted in measuring root distribution; and Mr. H. O. Sterling who supervised fertilization, insect control, and other cultural practices as well as the applica tion of the differential treatments to the ex perimental area during the writer's absence from the Citrus Station. LITERATURE CITED. Bingham, F. T. and Martin, J. P. Effects of soil phos phorus on growth and minor element nutrition of citrus. Soil Sci. Soc. Amer. Proc. : Bingham, F. T., J. P. Martin, and J. A. Chastain. Effects of phosphorus fertilization of California soils on minor element nutrition of citrus. Soil Sci. : Bryan, O. C. The accumulation and availability of phosphorus in old citrus grove soils. Soil Sci. : Camp, A. F. Citrus Industry of Florida. Part. Citrus growing in Florida, p., Florida State Department of Agri culture. Tallahassee, 9.. Chapman, H. D., G. F. Liebig, Jr., and A. P. Vanselow. Some nutritional relationships as revealed by a study of mineral deficiency and excess symptoms on citrus. Soil Sci. Soc. Amer. Proc. : Floyd, B. F. Some cases of injury to citrus trees* apparently induced by ground limestone. Fla. Agr. Exp. Sta. Bui. : H

9 FLORIDA STATE HORTICULTURAL SOCIETY, 9. Ford, H. W. The influence of rootstock and tree age on root distribution of citrus. Proc. Amer. Soc. Hort. Sci. : Ford, H. W. Root Distribution of Citrus Trees. Ann. Rpt. Fla. Agr. Exp. Sta. p Forsee, W. T., Jr., and J. R. Neller. Phosphate re sponses in a Valencia grove in the eastern Everglades. Proc. Fla. State Hort. Soc. : Lawless, W. W. Effect of freeze damage on citrus trees and fruit in relation to grove practice. Proc. Fla. State Hort. Soc. : Neller, J. R. A comparison of different sources of phosphorus for use on Everglades peat. Soil Sci. Soc. Fla. Proc. IV B: Reuther, W., and Crawford, C. L. Effect of certain soil and irrigation treatments on citrus chlorosis in a cal careous soil: I. Plant Responses. Soil Sci. : Reuther, W., F. E. Gardner, P. F. Smith, and W. R. Roy. A progress report on phosphate fertilizer trials with oranges in Florida. Proc. Fla. State Hort. Soc. : Reuther, W., F. E. Gardner, P. F. Smith, and W. R. Roy. Phosphate fertilizer trials with oranges in Florida. I. Effects on yield, growth, and leaf and soil composition. Proc. Amer. Soc. Hort. Sci. : Rossiter, R. C. Phosphorus toxicity in subterranean clover and oats grown in Muchea sand, and the modifying effects of lime and nitrate nitrogen. Aust. J. Agr. Res. : Smith/ P. F. Effect of phosphate fertilization on root growth, soil ph, and chemical constituents at different depths in an acid sandy Florida citrus soil. Fla. State Hort. Soc. Proc. 9: Smith, P. F. and Reuther, W. Citrus Nutrition. Chap ter of Mineral Nutrition of Fruit Crops. Horticultural Pub lications, Rutgers University, New Brunswick, New Jersey. 9.. Spencer, W. F. Distribution and availability of phos phates added to a Lakeland fine sand. Soil Sci. Soc. Amer. Proc. : Wander, I. W. The effect of calcium phosphate ac cumulation in sandy soil on the retention of magnesium and manganese and the resultant effect on the growth and production of grapefruit. Proc. Amer. Soc. Hort. Sci. : West, E. S. Zinc cured mottle leaf in citrus induced by excess phosphate. Jour. Aust. Council Sci. and Ind. Res. : WEED CONTROL IN CITRUS PLANTING SITES W. A. SlMANTON Florida Citrus Experiment Station Lake Alfred Much of the new grove acreage planted in recent years has been on sites that were for merly pastures. It was pointed out by Simanton and King () that considerable trouble has been experienced with the pasture grasses in caring for the young grove once the trees are set. Where ground cover cannot be readily suppressed when desired by usual grove culti vation, it can present a fire hazard, cause a rough surface that impedes grove equipment, intensify cold damage, and generally retard normal growth of trees. The trouble, expense, extra labor, and tree competition that has oc curred in groves with an excessive weed prob lem is such that growers should eliminate as far as possible these potential weed pests be fore planting the first tree. A grove is a long time investment; thus elimination of pest weeds may justify a substantial expense as part of the initial development cost. Pasture grasses known to give trouble in clude bermuda (Cynodon dactylon (L.) Pers.), pangola (Digitaria decumbens Stent), bahia (Paspalum notatum Flugge), para (Panicum purpurascens Raddi), guinea (P. maximum Jacq.), maidencane (P. hemitomon Schult.), and torpedo (P. repens L.), although these are Florida Agricultural Experiment Station Journal Series, No.. by no means all of the pest species. In the coastal areas para, guinea, and bermuda grasses are likely to be troublesome, but on the ridge pangola, bahia, and bermuda are often the problem. Maidencane, although not a planted pasture grass, is also a common grove pest. Torpedograss has been widely planted for pasture and in some areas it has become a particularly serious problem where the land is to be cultivated. Maidencane and torpedo produce rhizomes which can extend laterally underground for several yards. Where torpedo is established, aggressive pencil-thick rhizomes bearing tuber-like swellings may be found to inches below the soil surface. Viable rhizomes are known to exist even though all topgrowth has been suppressed for as long as six months. The grass competes severely with young citrus trees, and if the grove does become established it is likely to be less vigorous and require considerably more fertilizer, water and care than a noninfested grove. Until a method is found to eradicate torpedo or control it effectively, lands infested with this grass should not be used for citrus planting sites. If pasture woodlands, forest lands, and ham mocks are cleared for citrus groves, numerous plant species including vines, brambles, scrub oak, palmetto, and various root sprouts and bushes are likely to be troublesome weeds for a year or two after clearing. Generally the grass, broadleaf and woody weed problems