Fertilizers produce profound effects upon turfgrass behavior. Much more research is needed in this phase of turfgrass management. ns®a Published by the United States Golf Association (C) 1964 by United States Golf Association. Permission to reproduce articles or material in the USGA GREEN SECTION RECORD is granted to publishers of newspapers and periodicals (unless specifically noted otherwise), provided credit is given the USGA and copyright protection is afforded. To reprint material in other media, written permission must be obtained from the USGA. In any case, neither articles nor other material may be copied or used for any advertising, promotion or commercial purpose. VOL. 2, no. 4 November 1964 Bluegrass-Fescue Versus Bentgrass-Poa Annua Fairways .... By James L. Holmes 1 A Modification for Thatching and Mowing Units .............. By Alexander M. Radko 5 Fertilizer - How Much? ........................................................ By Marvin H. Ferguson 6 On The Research Front By Marvin H. Ferguson, J. B. Beard, and J. G. Lebeau 13 Published six times a year in January, March, May, July, September and November by the UNITED STATES GOLF ASSOCIATION, 40 East 38th ST., NEW YORK, N. Y. 10016. Subscription: $2 a year. Single copies: 30£. Subscriptions and address changes should be sent to the above address. Articles, photo­ graphs, and correspondence relevant to published material should be addressed to: United States Golf Association Green Section, Texas A&M University, College Station, Texas. Second class postage paid at Rutherford, N. J. Office of Publication: 315 Railroad Avenue, East Rutherford, N. J. Editor: Dr. Marvin H. Ferguson Managing Editor: Don Weiss THE GREEN SECTION OF THE UNITED STATES GOLF ASSOCIATION Green Section Committee CHAIRMAN: Henry H. Russell, P.O. Box 57-697, Miami 57, Fla. DISTRICT CHAIRMEN: Northeastern: John P. English, Williamstown, Mass.; Mid-Atlantic: Martin F. McCarthy, Chevy Chase, Md. ; Southeastern: El­ bert S. Jemison, Jr., Birmingham, Ala. ; Mid­ Western: Charles N. Eckstein, Chicago, HL; South­ western: L. A. Stemmons, Jr., Dallas, Texas: Pacific Northwest: Edward A. Dunn, Seattle, Wash.; California: Lynn A. Smith, Pasadena, Calif. Rocky Mountain: J. W. Richardson, Magna, Utah. Green Section Agronomists and Offices EASTERN REGION Northeastern Office: P. O. Box 1237 Highland Park, N. J. Alexander M. Radko, Director, Eastern Region Holman M. Griffin, Northeastern Agronomist Raymond E. Harman, Northeastern Agronomist Lee Record, Northeastern Agronomist Southeastern Office: P.O. Box 4213, Campus Station, Athens, Ga. James B. Moncrief, Southeastern Agronomist MID-CONTINENT REGION Southwestern Office: Texas A&M University, College Station, Texas Dr. Marvin H. Ferguson, Director, Mid-Continent Region and National Research Coordinator Mid-Western Office: Room 221, LaSalle Hotel, James L. Holmes, Mid-Western Agronomist Chicago 2, Ill. WESTERN REGION Western Office: P.O. Box 567, Garden Grove, Calif. William H. Bengeyfield, Director, Western Region USGA OFFICERS AND EXECUTIVE COMMITTEE PRESIDENT: Clarence W. Benedict, White Plains, N. Y. VICE-PRESIDENTS: Wm. Ward Foshay, New York, N. Y. Hord W. Hardin, St. Louis, Mo. SECRETARY: Philip H. Strubing, Philadelphia. TREASURER: Robert K. Howse, Wichita, Kan. EXECUTIVE COMMITTEE : The above officers and : Fred Brand, Jr., Pittsburgh, Pa. ; William C. Campbell, Huntington, W. Va. ; Robert F. Dwyer, USGA HEADQUARTERS: “Golf House”, 40 Portland, Ore. ; Edward L. Emerson, Boston, Mass. ; Edwin R. Foley, San Francisco; J. W. McLean, Houston, Tex. ; Eugene S. Pul­ liam, Indianapolis, Ind. ; Henry H. Russell, Miami, Fla. ; Charles P. Stevenson, Buffalo, N. Y. ; Morrison Waud, Chicago, Ill. GENERAL COUNSEL: Lynford Lardner, Jr., Milwaukee, Wis. EXECUTIVE DIRECTOR: Joseph C. Dey, Jr. ASSISTANT DIRECTOR: P. J. Boatwright, Jr. East 38th Street, New York, N. Y. 10016 Bluegrass-Fescue Versus Bentgrass-Poa Annua Fairways By James L. Holmes, Mid-Western Agronomist, USGA Green Section Prior to World War II, the majority of country clubs had bluegrass fairways on their golf courses and few of them were watered. Since 1945, most private clubs and a number of the courses maintained for public use have installed, or are now in the process of planning or installing, fairway water­ ing systems. Before 1940, most players, including those who made a living at golf, played the ball clean, or picked the ball clean­ ly from the turf rather than pinching the ball into the turf and against the soil surface, or hitting down on the ball. The modern golfers (especially those who consider themselves the best players) insist they will “hit flyers” if the ball nestles slightly into turf or if any quantity of grass is beneath or behind the ball. Consequently, the bet­ ter players today insist upon a short cut. As a result of all this, fairway turf on many courses is being watered and cut short. When cut close, bluegrass and fescue simply will not grow, devel­ op, and spread sufficiently to present a suitable turf. These grasses are “high stooling” plants as the first leaf develops up to 34 inch on the stem. If they are cut lower than l1^ inches, sufficient leaf surface or photosynthe­ sizing area is removed so that adequate chlorophyll does not exist. Consequent­ ly, insufficient quantities of sugar are manufactured. It follows that a healthy, vigorous growth cannot be supported and therefore starvation re­ sults. Bluegrasses and fescues are deep- rooted, vigorous plants. The vast healthy root system will explore the soil to quite a depth. Therefore, fre­ quent, light waterings are not neces­ sary. Rather, such watering practices will tend to reduce root systems and result in a tender, weak plant much more subject to attacks by pathogenic fungi. Thus, weedy growth is encour­ aged. Poa annua is the primary in­ vader and it will gradually replace bluegrass and fescue under such en­ vironmental conditions. Poa Annua Too Vigorous In this process of “turf change” brought about by the demand for close mowing and frequent irrigation, many tons of seeds of various bentgrasses have been sown in an effort to estab­ lish bentgrass turf. Many and varied types of programs have been followed. These programs may comprise plowing, vigorous aeration, sodium arsenite “kill back,” sprigging or stolonizing and simply drilling seed into fairway areas. Generally speaking, very small amounts of bentgrass have become es­ tablished in planted fairway areas. Poa annua continues to cover the vast majority of such areas. Perhaps our technology or ability to grow bentgrass is lacking or perhaps Poa annua is simply too vigorous a plant during most of the growing season to allow bentgrass to become established. In any event, considering our current knowledge, as long as turf is cut short and watered daily or every other day, Poa annua is not only with us but will continue to produce the largest per­ centage of fairway grass. Not only must Poa annua - bentgrass turf be watered frequently but plant NOVEMBER, 1964 1 nutrients must be applied regularly. Both types of grass are supported by shallow root systems, especially during July and August. Fertilizer demands are such that between three and six pounds of actual nitrogen per 1,000 square feet and approximately one half this amount of phosphoric acid and potash are required annually. Applica­ tions must be spaced throughout the growing season. Of course, both water and fertilization programs are depen­ dent upon the type of soils present. More sandy soils usually require great­ er frequency of water and larger total quantities of fertilizer. A bluegrass - fescue turf demands considerably less frequent irrigation. Weekly watering is usually adequate even during periods of drought. Ferti­ lizer requirements for this turf are roughly one half that for Poa annua and bentgrass. Repeated observations prove that bluegrass - fescue should be fertilized in late August or early Sep­ tember and early October only. If fer­ tilized in spring or early summer, weeds receive the greatest benefit and severity of disease activity is in­ creased. Of course, if the turf is new or the soil excessively barren, spring fertilization may be necessary. Within reasonable limits, practically all types of herbicides can be used safely on bluegrass and fescue. There­ fore, weedy growth is eliminated prac­ tically at will. Few herbicides can be safely used on a Poa annua - bentgrass turf. By this it is meant that Poa an­ nua and bentgrass usually suffer from applications of herbicides, especially of the hormone type. Many times the evi­ dence of damage is not visible until the advent of hot, humid weather. At such times Poa annua fades out and bent­ grass may also suffer serious damage. If the summer season is not severe (or hot and humid), damage from herbi­ cide applications may not be especially noticeable. Disease activity is pronounced on both types of grasses. Leaf spot can be and often is quite severe on bluegrass - fescue turf. Damage to this grass is evident as “spotty, thin growth.” Se­ vere disease activity usually is limited to spring and early summer and again in September. When disease is severe the golf ball will “nestle” into the pit­ ted turf. On the other hand, a myriad of disease causing fungi are patho­ genic on Poa annua and bentgrass, es­ pecially during periods of extended heat and humidity in July and August. When environmental conditions are such that disease is active, turf on en­ tire fairways can fade out. A typical example was the “fadeout” condition on Poa annua - bentgrass fairways throughout the Midwest last summer. (Bluegrass - fescue turf on fairways was never better in most sections.) Ap­ plications of fungicides were not ef­ fective in stopping turf “fadeout” last summer on Poa annua - bentgrass fair­ ways. In a normal season, fungicide requirements would be about 50% less on bluegrass - fescue turf. Insect activity and control is similar for both types of turf. Threefold Reason The prime reason for developing this type of article is threefold. Many comments have been offered about fairway turf kill last summer. Anyone planning to switch to Poa annua— bentgrass fairways or anyone planning to build a new course should have as much information as possible before making a choice as to which kind of fairway turf is most suitable for his purpose and the cost relationship be­ tween the two programs. 1. Comments about fairway turf kill last summer: Bluegrass-fescue turf was excellent this year in most 2 USGA GREEN SECTION RECORD cases. Poa annua - bentgrass turf killed out severely. The kill was quite general. If only a few isolated courses suffered fairway kill, the immediate consideration would be mismanage­ ment. However, because of the extent of damage, it is obvious that other factors are responsible. Disease acti­ vity was one of the important factors. It would seem that the best maintained courses (those with highest budgets) suffered the most severe kill-out, es­ pecially where total nitrogen applica­ tions were high and heavy watering practices were followed. This was es­ pecially true where soils were “heavy” and poorly drained and the course supported a large quantity of trees. Sandy, well-drained locations fared much better. Severe kill-out occurs about every 5-6 years in the north midwest. There­ fore, those who have had Poa annua— bentgrass fairways for a number of years report they are not interested in returning to bluegrass—fescue, but rather will live with what they have. On the other hand, many of those con­ templating converting to “so-called bentgrass” fairways have changed their minds at least temporarily and will live with their bluegrass-fescue. Also, they are interested in knowing why more suitable grass which can more successfully compete with Poa annua and can withstand a short cut has not been developed. 2. To those planning to switch to Poa annua-bentgrass or those build­ ing new courses: An effort has been made to outline the differences between the two basic fairway turf programs in the northern part of the country. The prime and perhaps the only reason for attempting to grow bent­ grass on fairway areas is simply that the best golfers (perhaps 10% of the players) insist they cannot play the ball unless it can be pinched against the ground. In order to do this, turf must be cut at % inch or preferably shorter. Poa annua-bentgrass can be cut at this height. Bluegrass-fescue turf must not be cut below 1% inches; therefore, it is more difficult or im­ possible to pinch the ball against the soil. The ball must be picked cleanly from longer turf. Of the profuse bentgrass seeding and overseeding which has been done, usually no more than 10% develops to any extent. Therefore, when discussing bentgrass fairways we really mean Supt. Elmer Michael, Oak Hill Country Club, Pittsford, N. Y. lays one strip of Merion bluegrass sod across fairways near the green to indicate where golf carts must terminate or turn. Once planted, the Merion strip lasts indefinitely, and stands out so well that even the unobservant player couldn't mistake the turn-off signal. NOVEMBER, 1964 3 our fair weather friend Poa annua. On bluegrass—fescue turf Poa annua is rarely a problem except in areas which receive excessive moisture. 3. Cost relationship: As can be de­ termined from what already has been said, maintenance cost for Poa annua —bentgrass fairway turf is approxi­ mately 50% greater than for blue­ grass—fescue turf. If you wish to have what is cur- rent’y considered (by some, especially the best golfers) “top” fairway playing conditions, install an adequate fairway watering system and sow bentgrass. But, be prepared to experience a few expensive troubles. Drainage is Essential In any type of fairway programs, especially for bluegrass—fescue cul­ ture, drainage, both surface and sub­ surface, is of prime importance. On many soils, adequate subsurface drain­ age simply cannot be obtained. There­ fore, all efforts must be made in con­ struction or reconstruction to assure that surface drainage is adequate. At least a 3% general fall must be ob­ tained if at all possible. Tile with ade­ quate and properly placed risers to insure rapid surface run-off is essen­ tial. After the area has been in play for a few years, wet spots or areas difficult to drain will be noticeable, even if reasonable tile drainage is afforded. In such cases simply dig a trench three feet deep by three inches wide through the wet area. Fill the trench to the surface with pea-size gravel. Turf will grow over the gravel is about two weeks. Do not place soil over the gravel and thus create a “perched” water table. If you are fortunate enough to have a sandy, well-drained soil, your fairway troubles are substantially reduced. In any event, do not build low-water 4 holding areas into your fairways. Also, do not cover a beautiful sandy soil with a layer of “heavier soil” thinking that it will be easier and cheaper to grow grass on the heavier silt or clay soil. It will not be so; it is much, much easier to apply water than to remove it. We have not meant to infer that the installation of a watering system is not advisable for culture or bluegrass —fescue. However, the superintendent must use prudence in his watering habits and be careful or he will tend to overwater. Otherwise, Poa annua and other weeds will gradually develop into a serious problem. Of course, arti­ ficial water is essential for the Poa annua—bentgrass fairway program. Conclusion : Although over 150 clubs have been visited this year and the fairway pic­ ture discussed with at least 200 people, it is difficult to say just exactly which program offers the most under all cir­ cumstances. The general thinking at this time is that Poa annua—bent­ grass fairways simply are too expen­ sive to maintain with too great a possi­ bility of going-out in the area south of a line running through Columbus, Ohio, Indianapolis, and Omaha. North of this line, the Poa annua—bentgrass will not go out more often than approx­ imately every six years; thus players and those responsible for maintenance tend to favor Poa annua—bentgrass if adequate water and money are available. Lower budget courses and those without water must stay with bluegrass—fescue. If the writer were to have the re­ sponsibility of maintaining a golf course he certainly would wish that bluegrass—fescue was the accepted fairway cover by the membership, but he is fully aware of the limitations of such turf and that his wish might not become a reality. USGA GREEN SECTION RECORD A Modification for Thatching and Mowing Units Gen. Wlnsfon points to bracket and wheel as­ sembly that he devised to prevent scalping of high spots on fairways. A front view of the bracket, wheel assembly and chain hitch. By Alexander M. Radko, Eastern Director, USGA Green Section In September officials of the Somer­ set Hills Country Club, Bernards­ ville, N. J. embarked on a program of renovation of some of their weaker fairways. In the process of renovating they made use of their hammer mower machine by substituting that­ ching blades for mowing blades. This was making good use of a machine al­ ready on their inventory but in proc­ ess of thatching they found that they were badly scalping the high spots. Somerset Hills, like many north Jer­ sey clubs, has rolling and sometimes sharply abrupt terrain. This troubled the Green Chairman, Maj. Gen. John L. Winston, and he modified the mow­ er by purchasing a pair of brackets and dolly wheels (made as standard equipment for a York rake) and clamped them to the front of the frame of the thatcher. He then re­ moved the upper link of the three- point hitch and substituted a small length of chain in order to be able to lift the rig. This flexible upper link is a must! The result is that instead of hav­ ing a wheel base of about 5^2 feet (from tractor wheels to the thatcher roller) the thatcher has a wheel base of less than 20 inches (from dolly wheels to thatcher roller) and now rides along this short wheel base over terrain irregularities, and indepen­ dent of the tractor. Chairman Win­ ston believes this modification could also be used to excellent advantage on rotary mowers. NOVEMBER, 1964 5 Fertilizer-How Much? By Marvin H. Ferguson, Mid-Continent Director, USGA Green Section ? f T7 aed them whatever they want, J- whenever they need it,” is a summary of one of the modern philos­ ophies of infant feeding. It might also be adapted to the feeding of turf plants. Of course, we must not attrib­ ute to grass plants an ability “to want.” We can, however, attempt to ascertain the requirements of plants for optimal growth and to meet those needs. The grower of turfgrass determines by careful observation and by soil tests the nutrient status of his plants and he supplies or withholds fertilizer according to his judgment of the plant’s requirements. This kind of management requires very careful ob­ servation, a knowledge of the effects of nutrient shortages, a knowledge of fertilizer materials, and a degree of clairvoyancy in regard to the effects of weather. While it is easy to exhort the grower to “observe carefully, consider all fac­ tors, and use good judgment” in fer­ tilizing, the multitude of factors which form the basis for good fertilizer prac­ tice are complex and varied. The prac­ titioner of turf management may not consciously consider each of the ques­ tions involved before using fertilizer but the successful grower is instinc­ tively aware of the implications of the variables. Plant requirements How do we know how much calcium or phosphorus a plant requires for op­ timal growth? This seemingly simple question has been the basis for years of research effort by students of min­ eral nutrition. Von Liebig, one of the first students of plant nutrition, of­ fered his concept of “the law of the minimum” in which he contended that any nutrient element which was de­ ficient controlled the amount of growth. Thus if the plant growth was limited by one element, the grower could sup­ ply an ample quantity of that nutrient, then the element which was next low­ est would become limiting. This early concept has not been completely dis­ credited even though subsequent re­ search has brought about modifica­ tions. The “balance of nutrients” concept is another which is controversial but which is accorded a degree of validity by many mineral nutritionists. Brief­ ly stated, this concept holds that the amount of each nutrient element pres­ ent in the plant produces an effect on growth but that the total amount is modified by its relationship to the amounts of other elements present. H. D. Chapman considered these com­ plex interrelationships to be impor­ tant and he summarized his views by stating “. . . . it is both the balance and the total which count.” The use of tissue analysis to deter­ mine the levels of nutrient elements existing in plants has been helpful in relating growth to nutrient content. However, there is not a direct rela­ tionship except in the case of deficien­ cies. Lundegardh states, “It has been objected against leaf analysis that the nutrients can vary a great deal with­ out a corresponding variation in yield. A thorough investigation shows that this is true only at supra-optimal per- 6 USGA GREEN SECTION RECORD CONCENTRATION OF NITROGEN (%) m e. PO«/IOOg. FIG. 1 The relationship between the concentration of nitrogen (on a dry weight basis) and yields of clippings. FIG. 2—The relationship between the concentration of phosphorous (on a dry weight basis) and yields of clippings. m e. K/IOOg. CONCENTRATION OF CALCIUM m.«.Ca/l00g FIG. 3—The relationship between the concentration of potassium (on a dry weight basis) and yields of clippings. FIG. 4—The relationship between the concentration of calcium (on a dry weight basis) and yields of clippings. m e. Mg / 100 g FIG. 5—The relationship between the concentration of magnesium (on a dry weight basis) and yields of clippings. FIG. 6—The relationship between the concentration of boron (on a dry weight basis) and yields of clippings. These figures show the relationship between varying levels of six nutrient elements and the growth of the plants as determined by measurement of the clippings. The turf used in these studies is Meyer Zoy­ sia. In figures 3, 4, and 5, a vertical line shows the concentration considered to be a "level of sufficiency" beyond which additional quantities of this nutrient will produce no further favorable effect upon growth. NOVEMBER, 1964 centages. A distinct limit can be dis­ tinguished, below which growth inev­ itably decreases. Values below this limit are the only ones which have an interest from the standpoint of fer­ tilization.” Lundegardh’s concept is one with which the author’s investiga­ tions show agreement. (See Fig. 1.) Unfortunately for the turf grower, there has been relatively little research aimed at relating the nutrient content of plant tissues to optimal growth or to the supply of nutrients in the soil, and in turn to the need for fertilizers. One notable effort in this direction is that of Noer and co-workers in which clip­ pings from bermudagrass putting greens in Memphis and bentgrass put­ ting greens in Milwaukee were weighed and analyzed to determine the quantities of nitrogen, phosphorus, and potassium removed by the plant. These were well-fertilized greens in both cases. The conclusion may be drawn that the amounts of materials contained in grass clippings is indica­ tive of the ratio in which these ele­ ments are needed by the plant. It has been used as a basis for the compound­ ing of fertilizers of a 3-1-2 ratio. Level of Potassium One of the facts which serves to confuse such conclusions is that potas­ sium, particularly, is subject to being taken into the plant in much larger quantities than are needed. This “lux­ ury consumption” appears to be more nearly related to the amounts of potas­ sium present in the soil and to the lev­ els of other cations present than to the needs of the plant. Hence, it is dif­ ficult to establish the necesary level of potassium. Likewise, it is recognized that addi­ tional nitrogen will result in increased vegetative growth. The increase of growth may not be desirable. It may result in a soft succulent, disease sus­ ceptible turf. Therefore in drawing conclusions with respect to the need for nitrogen, we must be sure to relate nitrogen supply not only to total growth but to turf quality and to those other management factors such as mowing frequency, mowing height, and irrigation. We must conclude that we still are in need of research to answer clearly the question “What does the plant re­ quire?” The direction of the research appears clear. (1) We must measure the growth of turfgrass plants sup­ plied with various definite levels of nutrients. (2) We must measure the amounts of nutrients contained in plants and relate these findings to the amounts of nutrients supplied. (3) We must determine at what levels (in the tissue) we observe less than maximum growth and at what levels we achieve less than the best quality turf. While such aims are simple to state, they will require painstaking, tedious, and thor­ ough research effort to achieve. From the practical standpoint, a turfgrass grower solves the problem by making use of soil tests to insure that there is an excess of nutrients such as calcium, magnesium, potash, and phosphorus. He then judges the need for nitrogen by the amount of growth which occurs. Lacking com­ plete knowledge of precise nutrient needs, the grower finds such an ap­ proach to be effective and practical. 8 USGA GREEN SECTION RECORD Source of nutrients The supply of nutrients for turf (or for any other plant) is derived from the soil or from added fertilizers. The relative amounts derived from each of the two sources are dependent upon the residual fertility of the soil and upon the management practices. Golf course roughs are seldom fer­ tilized. For this type of growth fer­ tilizer might be harmful because it might change the composition of the vegetative cover and it might cause so vigorous a growth that mowing would become much more of a problem. Some fairways are fertilized very little. Carpetgrass fairways in the South and buffalograss fairways in the Great Plains area may do very well with only the nutrients they derive from the native soil. On the other hand, bermudagrass, bluegrass, and bentgrass fairways re­ quire additional nutrients and these must come from the fertilizer bag. Ap­ parently grass responds equally to plant nutrient supplied, regardless of the source. When plants respond ad­ versely, the trouble usually lies in the amount, the timing, or the method in which the nutrients are supplied. Soil texture The inherent fertility of a soil de­ pends to some extent upon the texture of that soil. Texture is related to the soil particle size and therefore to the amount of surface of soil particles in a given volume. Because sandy soils have the least surface they can hold relatively small amounts of plant nu­ trients and they are notoriously low in fertility. Clays on the other hand have tremendous surface area and these tiny particles are negatively charged. Thus the positively charged mineral nutrient ions (the cations such as Ca++, Mg++, and K+) are held on the clay by an electrical bond. Silts are intermediate in size and in surface area. Thus we may see that with respect to nutrient supplying power the clays rank high­ est, with silts being poor, and sandy soils are very low. The texture of a soil also affects the fate of added fertilizer materials. Po­ tassium, calcium and magnesium are likely to find a place on the clay par­ ticle where they will be held tightly and prevented from leaching. Also, since clays usually are associated with slow water movement, leaching does not occur so rapidly. In coarse textured soils, those nu­ trients which go into solution are sub­ ject to ready leaching or to ready up­ take by the plant. In both coarse tex­ tured and fine textured soils, some of the nutrients are likely to react with other elements to form insoluble or slowly soluble compounds. The cations which are held on the clay particles by electrical charges may be removed for use by the plant through the phenomenon of “base ex­ change.” Thus clay soils may be the repository for substantial quantities of plant nutrients. It has been said that clay acts as a wise banker which will accept and hold the nutrient ions until they are needed and will relin­ quish them upon demand to the plant. Soil structure Soil structure is related to texture in determining nutrient supplying power. Structure is also interrelated to the content of cations in the soil. NOVEMBER, 1964 9 Cations such as hydrogen (H+), so­ dium (Na+), and potassium (K+) carry one positive charge and they sat­ isfy one of the negative charges of the clay particle. On the other hand, the cations such as calcium (Ca++) and magnesium (Mg++) carry two posi­ tive charges. They sometimes will be linked to two clay particles having one of the charges satisfied by a single negative charge from each of two clay particles. Enough of this “bridging” or “linking” occurs to cause clay particles to become aggregated. Very acid clay soils, known some­ times as hydrogen saturated clays, have a large percentage of their negative charges satisfied by hydrogen ions (H+). Because of the single charge of the hydrogen ion, there can be no ag­ gregation as a result of cationic “bridging” and such a soil is usually puddled or “run together.” This is the reason that liming often produces an improvement in soil structure. Thus we see that the chemistry of the soil affects structural characteris­ tics. Structure and texture are both important in determining the distribu­ tion of pore space in the soil. Capillary pore space holds water even after good drainage has removed the excess water. Non-capillary pore spaces are larger and after drainage occurs they are filled with air. If a soil is high in silt and clay, the non­ capillary pore space percentage will be quite small unless the soil is well ag­ gregated. When non-capillary pore space is limited then air is necessarily limited also and this implies a shortage of oxygen in the soil. Aggregation of soil particles is a function of the kinds of cations present and it depends also upon cultivation or the maintenance of good tilth. Because the ability of a grower to cultivate the soil under turf is limited, adequate supplies of calcium and magnesium become particularly important in the maintenance of a crumb-like soil structure under a turf cover. Pursuing the interrelationships fur­ ther, we note that oxygen in the root zone is necessary to the process of res­ piration. Respiration is a process wherein carbohydrates in the plant are used to produce the energy whereby nutrients are taken into the plant and transported. In the absence of oxygen respiration ceases or is drastically re­ duced, the permeability of membranes in the root cells is brought about and the uptake of moisture and nutrients cannot occur. Thus the chemistry of the soil affects the physical characteristics and both biochemistry and biophysics are in­ volved in the supplying of nutrients to the plants. In light of these facts it is not surprising that the world’s fertile soils are neither sands nor very heavy clays but rather the loam and clay loam soils such as are found in our prairie states and in our river flood plains. Thus soil texture and structure af­ fect the answer to the question—how much fertilizer? Kinds of fertilizer In an earlier statement we have said that plants respond equally to nutri­ ents, regardless of the source. The well-being of the plant, however, does depend upon a steady, balanced supply of nutrients, and it is adversely af­ fected by a “feast and famine” type fertilizer program. In order to provide the steady, balanced diet the turf 10 USGA GREEN SECTION RECORD grower must recognize the characteris­ tics of different fertilizer materials and use them in such a way that he achieves desired results. With all the major elements the turf grower has a choice between materials in which nutrients are readily soluble and therefore quickly available and those which are less soluble and which release nutrients more slowly and over a longer period of time. His choice will depend upon how the materials fit into his schedule and which approach he takes in feeding his turf. So—HOW MUCH? When wre consider all the rather com­ plicated interrelationships of plant needs, soil effects, and fertilizer char­ acteristics, we find that there is no pos­ itive answer that can be given to the question of “how much.” We must es­ tablish this as our aim—to supply the plant, at a steady rate, the nutrient elements it needs for efficient growth consistent with our use of it. Note that we have not said maximum growth. Maximum growth may be com­ pletely unsuitable for our needs. We must determine what the needs of the plant are. This has been done for Mey­ er Zoysia. (Figs. 1-6.) We have some ideas about the needs of other turf plants but definitive research is re­ quired to establish these needs more precisely. Each grower must determine the characteristics of his own soil as these characteristics pertain to the nutrient holding and supplying power. It may be possible in some cases to supply potash, phosphorus, lime and similar materials on an infrequent schedule. While nitrogen offers less flexibility in relation to the soil type, it too may be used more or less frequently depend­ ing upon the choice of the source. Fer­ tilizer materials should be chosen to fit the soil, the needs of the plant, and the personal preference of the user. A PRACTICAL APPROACH The grower of turf seldom can choose his soil, he uses the variety of grass suited to his geographic area and his need, and he often finds him­ self restricted in the use of adequate fertilizer by budget considerations. Nevertheless he must carry on and ad­ just his program to his needs as well as possible. A few rules stated rather briefly and simply should keep a super­ intendent out of serious trouble. 1. In a sandy soil, apply nutrients frequently and in small amounts. Study production of clippings and turf quality. Adjust rates and fre­ quency accordingly. 2. In heavier soils, applications may be spaced at greater intervals. Study production of clippings and turf quality. Adjust rates and fre­ quency accordingly. 3. With a readily available nitrogen fertilizer, apply lightly and frequent­ ly. With a slowly available nitrogen fertilizer interval may be increased. In either case, study production of clippings and turf quality. Adjust rates and frequency accordingly. 4. Depend upon soil tests to guide you in keeping soil reaction near neu­ tral. Tests also are reliable indicators of the soil supply of potassium, mag­ nesium, calcium, phosphorus, and sul­ fur. 5. Learn as much as possible about fertilizers. No other management tool available can do more to determine the quality of your turf. NOVEMBER, 1964 11 Supt. John Cook of the Country Club of Virginia, Richmond, Va., inspects work of power edger which keeps bermudagrass runners in apron from in­ festing the bentgrass green. The edger is used weekly to keep the bentgrass green uncontam­ inated. Above, a close-up of the defined bermuda- bentgrass line. COMING EVENTS November 15-18 American Society of Agronomy Meeting Kansas City, Missouri November 18-20 MGCSA Turf Conference Normandy Hotel Minneapolis, Minn. December 3-4 Winter Turf Conference Illinois Turfgrass Foundation Urbana, Illinois December 7-9 Texas Turfgrass Conference Texas A&M University College Station, Texas January 4 - March 12 Winter Course for Turf growers Rutgers College of Agriculture New Brunswick, N.J. January 27-28 Virginia Annual Turfgrass Conference John Marshall Hotel Richmond, Virginia January 29 United States Golf Association Green Section Educational Turf Conference Biltmore Hotel New York, N.Y. February 1-3 Southern Branch of the American Society of Agronomy Adolphus Hotel Dallas, Texas February 7-12 GCSAA Conference Sheraton-Cleveland Hotel Cleveland, Ohio February 22-23 Southern Turfgrass Association Conference. Peabody Hotel Memphis, Tenn. 12 USGA GREEN SECTION RECORD On The Research Front Editor’s Note: These are abstracts of papers prepared for the 1964 annual meet­ ings of The American Society of Agronomy and published in Agronomy Abstracts. Physiological Mechanisms of Winter Injury to Plants By Marvin H. Ferguson, United States Golf Association Desiccation appears to be the most frequent cause of winter injury inso­ far as turfgrasses are concerned. Other physiological mechanisms of injury are associated with flooding and ice sheet formation. Deficiency of oxygen, accumulation of carbon dioxide, leach­ ing of cellular contents, mechanical rupture of cells by ice crystal forma­ tion and dehydration of tissues are among the mechanisms which are sug­ gested. Injury caused by late spring cold spells after grass has begun growth is common. Cell rupture and desiccation appear to be the chief causes of injury under these condi­ tions. Causal Agents in Winter Injury of Turfgrasses and Their Relative Importance By J. B. Beard, Michigan State University Winter injury encompasses a num­ ber of types and causes including des­ iccation, heaving, disease, direct low temperature kill and injury associated with ice and snow covers. Injury asso­ ciated with ice and snow covers can be subdivided into oxygen suffocation or toxic accumulations under an ice sheet, leaching of vital cellular constituents when submerged in water during thaw, and direct low temperature injury to meristematic areas during spring freeze and thaw periods. The relative importance of these causal agents de­ pends on the location, grass species, hardiness of the plant, severity and type of winter, and nutritional level at which the plant has been maintained. Significant variations in susceptibility to low temperature and ice cover injury have been shown between grass species and within the bluegrasses, bentgrass­ es and fescues. The hardiest species tested are the vegetative bentgrasses and roughstalk bluegrass. Our current state of knowledge suggests a need for more detailed studies concerning ice crystal formation in grass plants. Pathology of Winter-Injured Turfgrass By J. G. Lebeau, Canada Agriculture Research Station, Lethbridge, Alberta Winter killing of turfgrass is seldom due to sub-zero temperatures alone but is also caused by desiccation or attack by psychrophylic fungi. In western Canada snow mold on turfgrass is caused by an unidentified basidiomy- cete. Investigations on snow mold of turfgrass in Alberta showed that dam­ age was consistently associated with accumulation of HCN in the host tis­ sues. Snow mold on turfgrass was con­ trolled in southern Alberta by raising the temperature of the soil a few de­ grees during cold periods in the winter. Minimum temperatures were main­ tained in the plots by soil-heating ca­ bles controlled by thermostats. The temperature required for control was critical. Cold-hardy varieties of turf­ grass were more resistant to snow mold than non-hardy varieties. NOVEMBER, 1964 13 USGA GREEN SECTION RECORD 40 Eest 38th Street, New York, N. Y. 10016 TURF TWISTERS PUTTING GREEN SPECIFICATIONS Question: As a golf course architect, I am most interested in the USGA Specifications for Putting Green Construction. I have contact­ ed a local soil testing laboratory and enclose a copy of their letter. Would you care to comment? (California). Answer: We were very much interested in the information supplied by your local soil testing laboratory. We sincerely wish them well in their belief that their “services would improve the performance of putting greens.” Nevertheless, the construction method recom­ mended by the USGA Green Section is just as “guaranteed” as any practical method now known. It may be of interest to review some of the background in soil studies for putting green use. For the past twelve years, the USGA has sponsored research at universities throughout the country on this subject. Before the Specifications were published, they were re­ viewed by several of the outstanding soil physicists and agronomists at universities throughout the country. The Specifications are sound, documented and will withstand the test of time. After the Specifications were published, a number of soil labor­ atories and “soil experts” claimed that they could carry out all of the tests as recommended by the USGA Green Section. In some instances, soil laboratories have also claimed that they could “improve upon” these Specifications. In other words, there was a sudden rash of of “experts” on the subject. They apparently have “all the answers” but very little research in this specific area to back them up. The Green Section has no direct argument with such laborator­ ies or soil experts in their recommendations. Similarly, there is no control over golf course architects or construction firms wishing to follow such recommendations. However, we do strongly object to misuse of the term “USGA Specifications will be used in construc­ tion.” This has happened a number of times and the final product has been less than satisfactory. The USGA Green Section has been criticized where, in fact, our Specifications were not followed. In conclusion, the Specifications are just as applicable in Alaska as they are in New York, Illinois, Texas or California. They should be followed exactly as outlined, including the all-important physical soil analysis. Any Green Section office will be happy to send you the names of laboratories that have provided satisfactory physical anal­ ysis work based on our Specifications.