Journal
of
RANGE
MANAGEMENT
Vozume
May,2o
1967Number
3
The Range Sociefy is af fhe Crossroads ____ .____.___.___ ._._ _____ __.___. Joseph F. Pechanec 125 Grazing and Ferfilizafion Affecf Roof Developmenf
of Range Grasses _.__ ______ ______ _ .___ _ ._.. ..Russell J. Lorenz and George A. Rogler Seeding Sherman Big Bluegrass ___________..______._____________________ ___.._._. . . ..Pat 0. Currie Effecf of Grazing on Soil Compacfion as Measured by Bulk Densify on A High Elevafion Caffle Range . . . ..William A. Laycock and Paul W. Conrad
129 133
136 Roof and Shoof Growfh of Five
Range Grasses __.._ _._______________,____ __.____ . . . ..R. L. Dalrymple and Don D. Dwyer 141 Plant Succession with Released Grazing on New Mexico
Range Lands _____ __ ______ _ ________________ . . . . ..Lcren D. Potter and John C. Krenetsky 145 Grazing of Alfalfa Variefies and Observafions
on Bloai ._ ______ _____ ______. _____________,___ ____ ________ _____.____ R. Ashford and D. H. Heinrichs 152 Responses of Soufhern Range Caffle fo
Profein Supplemenfafion ______ ______ _ _.____ ___ __..__ V. L. Duvall and S. L. Hansard 153 Ground Treatmenfs for Confrol of Winged
Elm on Rangeland _ ____ _____________ ______ B. Kirby, P. Stryker, and P. Santelmann 158 Esfimafing Foliage Yields on Ufah Juniper from Measuremenfs
of Crown Diamefer _____________ .____ _ .___. Lamar R. Mason and Selar S. Hutchings 161 Chemical Confrol of an Old Stand of Chaparral to Increase Range Productivity
Chester A. Perry, Cyrus M. McKell, Joe R. Goodin, and Thomas M. Little Fire Effecfs on Semideserf Grasses and Shrubs. __.__... ___ ____________. . ..Dwight R. Cable
166 170 Technical Noies:
Seasonal Profein Content of Four Southern Mixed
Prairie Grasses ______________ _____ ______ __ ________ J. Daniel Rodgers and Thadis W. Box Gross Energy Value of Aboveground Parfs
of Alpine Planfs ___._ _____ ____.._ ____. _.___________ ____ ______._ _... ___..__ ___.... ___._I .._.___ Dixie R. Smith Depfh fo Seed Fourwing Salfbush....H. W. Springfield and Donald G. Bell
177 179 180 Managemenf Nofes:
Applying Research Findings To Commercial
Beef Producfion _____ _ __.___ _._____._ ______.._________.__..._ _____ ______________ ___ __.__.________ 0. J. Barron Improvemenf and Managemenf of fhe Cub River Caffle Range
in Soufheasf Idaho __.____.___ _________ __._ _____ _ ___. __________ __ ___._....___.. _ .._. Ralph B. Roberts 182 185 Book Reviews _______ __._ _____ _____ _ ___________ __ ._.... __ .__.____________ ____ ____ ________ _.______._.___.___.____ __ ..____ _.__.._ .._._ Currenf Liferafure _____ ._____ _ _____________ _.__.___ ____...________ ___________ ________ _____ __._...__..__.____... _ _.___ _._._____ Sociefy Business ___ ____ __________ _____. ________ ___._______.___ _ ____..____ _ .__.__..__..________.___ ___ . .._.. _ _____..._ _______ __.__ _ Presidenf’s Message __________ ______ ___________ _________ ___ _______ ___ _._____ _________ ______ _._____________ ___.__ ___ ____ _._____._ News and Nofes ______________________ ____ ____ _________._.._.___. _ _..__..__.____________ ________._____..._.___ ___. _ ..______.._... _
187 188 190 190 202
cover
Photo-_-Applying
Research Findings-
The Range Society is at the Crossroads’
JOSEPH F. PECHANEC
Director, Intermountain Forest and Range Experiment Station, Forest Service, USDA, Ogden, Utah.
Highlight
The American Society of Range Management has come far in ifs first 20 years, as fhe sole professional or- ganization with conservation of rangelands as ifs dominant objec- five. Buf in the meantime, urbaniza- tion and increased leisure for more people have changed our environ- ment. The Range Socieiy should ac- cept broader professional concern for all matters pertaining fo range in io- morrow’s environment. We need to assemble facis and establish strong policy regarding conservafion and use of rangelands. Finally we need closer fies with user groups and ofher professional nafural resource organizaiions-io carry ouf our ob- jectives.
The Range Society’s mission in life, if we look at it with vision, is to assure that rangelands serve to the fullest the needs of people. We are the only Society with conservation of rangelands as its dominant objective. Thus, as a professional Society, we are champions of wise use of nearly half the total land area of con- tinental United States and a very substantial portion of Canada and Mexico.
More than two decades ago we recognized a void in strong concern by professional societies for the tremendous potential values involved on rangelands. We formed a Society dedicated to improving rangeland man- agement and use. In so doing we said to the world: “Here is a job worth doing, and we’ll do it!” With such an awesome prom- ise it is essential that we, as a Society, take a look at how well we are doing, and choose the road we want to follow in the years immediately ahead.
The Society’s objectives, devel- oped and published nearly two decades ago, embody the chal- lenge that we saw then. Each of
you
is intimately acquainted with the breadth and depth of these objectives.Today I shall briefly review with you four major questions. First, what foundations have we built since the Society was for- mally organized 19 years ago last month in Salt Lake City? Second, how has our socio- economic and political environ- ment changed? Third, how well have we progressed toward our objectives in this changed en- vironment? Fourth, what major challenges does our Society face today?
The Foundations on Which We Built In the short two decades of the American Society of Range Man- agement’s existence we have built well. We can point proudly to many notable accomplish- ments. Of these I shall mention only a few as illustrations.
Our broad membership base, accepted by the membership within the first year, provides real strength. In deciding to em- brace within our membership all men with strong interests in rangelands and their uses, we established an organization dedi- cated not only to grass, or forage, or livestock, or game, or any other aspect, but to a composite. By creating the opportunity for internal forums representing a variety of interests, backgrounds, and objectives, we avoided a mistake made by some other pro- fessional organizations.
At the same time, this broad membership base has created somewhat of an obstacle to rec- ognition of the Society as a pro- fessional organization. It also may be partly responsible for concern expressed by the Range Management Education Council in their 1963 Report, as follows: “The most critical problem fac- ing the range management pro- fession today is the lack of rec- ognition of range management
125
as a science and as a profession.” The Society has increased ten- fold in membership-from 400 to 4,000 - since our first annual meeting. This is good, but not dramatic when we consider the number of range-oriented peo- ple who are eligible for member- ship. Even though it is not as big as we need, it is approach- ing the number needed to be an effective force for achieving So- ciety objectives and to finance activities that need to be accom- plished.
Our Society has a highly re- spected bimonthly Journal, now in its 20th volume. There is still, and I suspect always will be, criticism among our members about the balance between scien- tific, how-to-do, and popular types of articles. But you can- not scan through the 20 volumes, as I had occasion to do recently, without being impressed by the tremendous wealth of informa- tion and knowledge that this Journal has provided for our membership, and for other read- ers in North America and abroad.
Our 18 active Sections, three of which we share with our good friends to the north-canada- and one in Mexico, provide the real strength of the Society. Their meetings and their con- tacts are closely attuned to ex- change of technical information among their members, balanced discussion of conservation issues, and acquainting other groups with the importance of range- lands.
We have liaison with 11 allied scientific organizations, and we have had formal liaison with livestock associations. It is hard for me to appraise how actively, and in what depth, these highly essential relations are being con- ducted. But a recognition of the need and a mechanism for estab- lishing them has been developed.
126
RANGE SOCIETY
tries where there was
absolutely
no understanding ofthe term,
what it meant, or the importance of the resources involved. This establishment of widespread in- ternational relations has been achieved through hard work of our very vigorous International Relations Committee and our members abroad, through our former Middle East Section, and through widespread circulation of the Jo~~r~aZ. Granted, the un- derstanding of range manage- ment is extremely thin in many developing countries; but range education and technical assist- ance are very actively continu- ing.We have moved forward ag- gressively, t h r o u g h the Range Management Education Council, in improving uniformity and professional quality in range management curricula and in es- tablishing higher Civil Service standards for range-trained col- lege graduates.
We have established an order- ly basis for the development of effective and vigorous policy by the Society. But, as yet, the So- ciety has not carried out its re- sponsibility to any great extent. To do so in a manner that will engender the needed respect for our position will require a rec- ognition of broad public interest, time, effort, and careful thought. As you review the accomplish- ments I have named, it becomes clearly apparent that our Society has internally established good foundations for meeting the ob- jectives as we saw them two decades ago.
Our Environmenf Has Changed in today’s parlance, our en- vironment is different than it was two decades ago. Since the modest beginnings of this So- ciety, and while we were achiev- ing the accomplishments I just listed, times have changed, and will continue changing with ever-increasing speed. We must examine today’s environment and decide what role we want
the Society to play and where it needs to increase effort to achieve a position of prominence in the natural resources field. I will mention only a few of the major changes that have taken and are taking place.
Our rapidly growing popula- tion continues to shift from rural to urban residence. Four decades ago about half of our population was rural. Today, an average of less than one out of four persons is from such areas. In the year 2000, according to projections, only one out of ten is likely to be living in a rural area. Thus, any real understanding of land and its management is becoming increasingly a heritage of the minority.
Together with the effects of reapportionment, this popula- tion shift means that an increas- ing proportion of our State leg- islators and Members of Con- gress will be made up of leaders who will have little or no back- ground or understanding of land. These, our elected representa- tives, are the ones who formu- late State and National policy.
At the same time, the Amer- ican public has intensified its attention to wildlife, outdoor recreation, beauty of the land- scape, preservation of endan- gered species, and to pollution of air, soil, and water. Parallel with this shift has been a decreasing appreciation of land as a source of raw materials and products.
Administration, management, and use of rangeland are becom- ing infinitely more complex. The public interests just mentioned and such subjects as land law review, weather modification, widespread concern about pesti- cides, reorganization of natural resource agencies, rural reforms, and river basin commissions, have been or are being reviewed by select committees, conferences, legislative hearings, and similar groups at State and Federal levels. All of these affect our profession and the Society in one way or another.
There is an eruption of spe- cial-interest groups - groups Of persons with the common ob- jective of defending or promot- ing their specific interest in some single natural resource or fea- ture of a resource. These groups are frequently made up of dedi- cated, well educated and highly articulate people whose defini- tion of conservation relates di- rectly-often exclusively-to their own special interest.
All of the above changes in environment and personal inter- ests, plus increasing numbers of people, increasing affluence and leisure time, and mobility of our population, are resulting in
in-
creased pressures on the land. To satisfy these increased demands, management direction is shifting quite largely to the simultane- ous production of two or more goods and services from the land. Multiple outputs have be- come a necessity.At the same time, increasing doubt is being expressed about the importance of livestock graz- ing on rangeland. There is no question on a State or National basis that dependence of live- stock on range for feed and for a ge , percentagewise, is de- clining. Even in the State of Utah, it is now estimated that only 40% of the feed and forage used by beef cattle and sheep comes from rangelands.
But the doubt goes further. Some economists have recently shown by traditional methods of economic analysis that ranchers in certain range areas cannot make a profit. You will prob- ably get further insight into this situation during Dr. Upchurch’s paper later in this annual meet- ing. Those of you who attended the Wichita annual meeting may remember that Director C. Peairs Wilson, in his excellent talk, pointed out that rangeland is
in
a questionable competitive posi- tion with cropland as a basis for meat production.PECHANEC 127
What do they mean to the So- ciety and to us as members? of special-interest groups and
others reason for stating that we don’t need to continue livestock grazing on rangelands - our needs for beef and lamb produc- tion in the future will come from intensively managed pastures. A
few of our own prominent mem- bers have made similar state- ments in public meetings. These doubts also probably lead to statements by non-rangemen such as that of Dean Stephen H.
Spurr of the Graduate School, University of Michigan, in the November 1966 issue of the Jour- nal of Forestry; in writing of America’s natural resources he stated, “Range management has become a field of its own, but, in its turn, is becoming less im- portant as cattle and sheep in- creasingly are raised intensively and in concentrations.”
These uncertainties, or cer- tainties in the minds of some, in the absence of authoritative data, are leading to serious ques- tioning by high Government of- ficials of the need for expendi- tures for needed expansions in - range research and for manage- ment and improvement on pub- lic rangelands. They are affect- ing or doubtless will affect pri- vate investment in improvement and management of range. Un- doubtedly they will also affect the number and quality of stu- dents enrolling for college train- ing in range management.
Moreover, these doubts about the importance of rangelands for livestock forage, coupled with an increased vocal interest in their other uses, values, or attributes, are resulting in allocation of rangelands to uses other than livestock grazing. Decisions on land policy, always of a socio- economic and political nature, will be increasingly controlled by urban needs and desires.
Therein can lie a serious threat to one major reason for this SO- ciety’s existence. More than two decades ago, when formation of the Society was being consid- ered, the primary force stimulat- ing such a move came from the use of rangelands for livestock grazing. This, as a reason for the Society’s existence, would be seriously undermined if the be- liefs of some people regarding continued need and profitability of grazing livestock on range- lands remain unchallenged, and there were extensive, exclusive allocations of rangelands to rec- reation, production of wildlife, and other uses sought by domi- nant public interests. Should these changes take place, as pre- dicted by Dean Spurr’s state- ment, the Range Society under present circumstances is certain- ly not likely to be an influential force in management and policy development for natural re- sources.
How Well Are We Attuned To These Changes?
I am not convinced that these events will take place. I am sure that many of you aren’t either. But we must critically examine ourselves and the Society in the light of many questions. Among these are:
l What role do we want this Society to play? The broad role of professional concern about rangelands and all goods and services they may provide people, mentioned in my opening remarks? Or a narrower role dealing pri- marily with forage production and livestock grazing, with only peripheral concern for other products and values? l Has this Society kept abreast
of the increasing complexity and breadth of natural re- source problems? Have we members accepted and broad- ened responsibilities in keep- ing with the changing times? @Has the Society assembled
facts that will convey to other We cannot afford to ignore or
dismiss lightly these changes and the challenges they present.
professionals and the general public an understanding of the goods and services that range- lands provide, the contribu- tions they make to the econ- omy, and the opportunities for increasing these?
l Is the Society recognized as authoritative regardingrange- lands and their values and use for livestock production? 01s the Society considered
equally authoritative regard- ing rangelands and their use by wildlife? as watersheds? for outdoor recreation? or for a composite ? Or do we just listen politely, hoping these other uses will go away, in- stead of recognizing them as legitimate, associated, or even competitive and alternative uses?
l Does the Society have policy positions related to future uses of rangeland resources? Are we as members willing to devote the time and effort necessary for sound policy
formulation and followup
action? Or are we willing to let our rightful leadership go by default?
l Is the Society known and re- spected by other natural re- source professional groups? Have we worked with them as closely as might be desir- able?
l Is the Society known and re- spected by special-interest groups? By urban groups? By legislative policymakers? l Has the Society or its Sections
128 RANGE SOCIETY
size of sphere we represent. With the other questions, if we examined ourselves objectively, we would find we have made some progress but still are sore- ly lacking in achievement. This does not mean that Society ob- jectives are inadequate, or that the course we followed up to now was wrong. But it does mean that there needs to be a
searching examination of priori- ties and urgencies in establish- ing the Society’s course for the years immediately ahead.
Some of you doubtless feel this appraisal is too severe. You can point to some excellent, well- balanced, annual meeting pro- grams such as the one for this meeting, to some fruitful rela- tions that have been established with user and other groups, and to some well-designed field trips. Even so, I dare say that interest and activity of the preponder- ance of our 4,000 members are confined to technical aspects of livestock grazing on rangelands.
Challenges For The Future The Range Society is at the crossroads. This I sincerely be- lieve. Dedicated and imaginative effort on the part of the officers and a22 members will be required if we fully accept the challenges for the future.
Internally, many things still must be done to strengthen our Society. Among these are enlist- ment of more members, achiev- ing a wider representation of stockmen and others interested in multiple uses of rangelands, establishing a better financial structure, obtaining a firmer rec- ognition of range management as a science and profession, estab- lishing better standards for range-trained men with inclu- sion of an understanding of uses and values other than for live- stock grazing, and publishing an increasingly useful Journal and other publications.
But the road ahead will need some change, if the American Society of Range Management is
to achieve its rightful place among the professional natural resource organizations. The di- rections I would suggest we pur- sue are as follows:
1. We need to examine criti- cally the role we want the
SO-
ciety to occupy in tomorrow’s en- vironment. I would hope we can accept the broader role of pro- fessional concern in all matters relating to the conservation and use of rangelands for all goods and services they may provide for the American people. If we do, we must make it clear by deed as well as word that this isn’t just a facade, but a deep conviction to which we are dedi- cated.
2. We need to assemble facts concerning rangelands, their im- portance now and in the future for livestock grazing, for wild- life habitat, for outdoor recrea- tion, and for other uses. This should be analyzed carefully, and a comprehensive, authorita- tive report prepared which could be used for a variety of pur- poses. It could be that this would substantiate to some extent what some people are saying. Even so, we would have a far better basis for shaping future actions than we now have.
3. We need to establish strong policy, and the first item is a clear statement of what the
So-
ciety stands for with respect to the conservation and use of rangelands. This is essential for unifying internal purpose, as well as conveying to others an understanding of the Society.
4. We need to seek and estab- lish far closer relations with user associations, and urban and special-interest groups.
5. We need to join hands with other professional natural re- source organizations. There was strength 1.n setting up a separate organization-but there are also weaknesses faced by ourselves and others. Even with its mem- bership of 16,000, the Society of American Foresters finds itself
in a position of weakness. The development of strong, balanced, national policy and pursuit of it will require joint effort by many professional natural resource or- ganizations. Perhaps some type of formal union might ultimate- ly be necessary, but the first step is to seek to develop joint uni- fied action through cooperative effort.
I would further suggest that the road the Society should fol- low is of such critical importance that at least one full session of an early annual meeting be de- voted to exploring various de- tails of it.
A Society that is standing for something concrete, that is ef- fective at the many levels of pol- icymakers, and whose counsel is being sought will, I submit, at- tract members. Thus, by extend- ing ourselves externally, we may at the same time resolve some of our more perplexing internal di- lemmas.
To meet these challenges ef- fectively-if the Society elects to go in this direction -we must keep in mind that we will have to spend the time and devote the effort that are necessary to do a thorough job. Anything less will not strengthen the Society to the extent needed.
If we don’t move forcefully in this direction, there are certain- ly others far less knowledgeable regarding rangelands who will. For choosing this direction the reward is a Range Society-our Range Society-standing as an effective force in the natural re- sources fields, known for its re- liability and professional con- cern that rangelands serve to the fullest extent the needs of peo- ple, now and in the future.
1 Address at Keynote Session, Twen- tieth Annual Meeting, American Society of Range Management, Seattle, Washington, February 14, 1967.
Grazing and Fertilization Affect
Root Development of Range Grasses
RUSSELL J. LORENZ AND GEORGE A. ROGLER Research Agronomists, Crops Research Division, Agri- cultural Research Service, U.S.D.A., Mandan, North Dakota.
Highlight
Grazing intensify of native range had little effect on total root weight, but under heavy grazing the per- centage of total roofs in the upper foot was greater than under mod- erate grazing. Thirty lb of N sig- nificantly increased roof weight in the 4-ff profile. Ninety lb of N did not further increase root weight al- though fop growth was significantly increased.
The root system of perennial grasses becomes doubly impor- tant when fertilizer or other in- tensive management practices are used to increase top produc- tion. Any reduction in root vol- ume reduces the effective mois- ture and nutrient reservoir. Effi- cient soil moisture extraction is vital to optimum production under semiarid conditions. A de- crease in root volume or in root: top ratio increases the demands on each unit of root material, and under adverse conditions may jeopardize survival.
The effects of grazing intensity and fertility level on root devel- opment of native grassland are often referred to, but controlled studies usually involve forage re- moval by mechanical means. Very few root data are available from grazing intensity studies
(Lorenz and Rogler, 1966). Materials and Methods Two pastures at the Northern Great Plains Research Center
near Mandan, North Dakota
were sampled to compare root development and distribution. One pasture had been heavily grazed and the other moderately grazed since 1916.
The soil of the pasture area is classified as Temvik (former- ly Eakin) silt, loam. Prior to initiation of the fertilizer study, total N in the 6 inches of surface soil was .257 and .250% for the
heavily and moderately grazed pastures, respectively. C h an g e s in chemical properties of the soil and soil moisture extraction pat- tern for the fertilized plot study were discussed by Smika et al.
(1961). Soil moisture was also measured gravimetrically in the grazed areas of the pastures in May and October of each year.
Vegetation of the area is mixed prairie. Dominant species are western wheatgrass (Agro- pyron smithii Rydb.) ; needle- andthread (hipa comata Trin. & Rupr.) ; blue grama (Bouteloua grucilis [HBK.] Lag. ex Steud.) ; and upland sedges (Curex spp.) . Continuous heavy use has re- duced the western wheatgrass and needleandthread, until blue grama and upland sedges are now the dominant species in the ‘heavily grazed pasture. The veg- etation in the moderately grazed pasture has remained relatively unchanged since 1916. Fringed sagewort (Artemisiu frigidu Willd.) and other forbs are pres- ent in varying amounts in both pastures.
Ammonium nitrate was ap-
plied in October of each year (1951-1961) at rates of 0, 30, and 90 lb N/acre to three replica- tions of plots isolated from graz- ing in each pasture. Rogler and Lorenz (1957) reported an in- crease in hay yield from appli- cation of N to these plots. Study of the effects of N on the vegeta- tion was continued through 1962.
Another set of plots which re- ceived no fertilizer was isolated from grazing in the heavily grazed pasture. A new plot was added to this isolation each year from 1952 through 1962. Forage was harvested from each isolated plot about August 1 of each year.
129
A tractor-mounted hydraulic soil probe was used to obtain cores from which the roots were separated by washing over a No. 18 soil sieve (16-mesh equiva- lent) as described by Lorenz and Rogler (1964). Twelve cores
(0.875 inch in diameter) per plot resulted in sampling accuracy within one standard deviation about the sample mean 90% of the time for sample weights of 6 g or greater, and 85% of the time for sample weights of less than 6 g. Samples consisted of 12 cores bulked by 6-inch incre- ments for the top foot and by 1-ft increments for the second, third, and fourth feet.
Roots were sampled in late fall of 1961, a season of below-normal precipitation and again in late fall of 1962, a season of above- normal precipitation (Table 1). Precipitation for the 4-year pe- riod prior to 1961 is shown as a guide to soil moisture conditions which may have influenced the roots as sampled in 1961 and 1962. Precipitation was near the 48-year average in 1957, but in 1958 and 1959 both annual and seasonal precipitation were far below average. In 1960, above- average se as 0 n a 1 precipitation included over 5 inches which fell during three heavy showers that resulted in extensive runoff. Thus the effective 1960 precipita- tion was nearer 8 inches than the 13.75 inches recorded for the season.
130 GRAZING AND FERTILIZATION
Table 1. Average precipifafion (in inches) for 6 years (1957-1962) and fhe 1915-62 average af fhe Norfh- ern Greaf Plains Research Cenfer, Mandan.
.______ -____ ____-
Precipitation
Year April-Aug. Annual
-__
1957 10.99 15.38
1958 8.77 12.64
1959 7.06 11.97
1960 13.75 14.98
1961 7.19 12.12
1962 12.34 14.95
1915-1962 ave. 10.97 15.71
Table 2. F values from sfafisfical analysis of roof weigh& from plofs of ferfilized nafive range sampled in 2 consecufive years.
_ _______~ ~_.~_ _ __ - ~ -~ _- _ Source of
variation F values ~____
Replication 0.76
Pastures 0.12
Nitrogen level 6.62**
Depth of sample 719.68**
Year 17.04””
NxP 0.18
NxD 2.96””
NxY 0.11
PxD 2.53*
PXY 4.26”
YxD 1.58
NxPxD 0.78
NxDxY 0.37
--* Significant at 5% level. ** Significant at 1% level.
crease resulted from the second increment of N. In comparison, forage production was doubled by 30-N and tripled by 90-N
(Rogler and Lorenz, 1957). Sim- ilarly, Hylton et al. (1965) found that Italian ryegrass (Lolium multiflorum Lam.) produced the most roots when low rates of N were applied, and with increas- ing N, root weight decreased even though top weight was still increasing.
Lack of significant difference between mean root weights from plots in the two pastures (Table 3) suggests that any effect of grazing intensity on root devel- opment was eliminated by the treatments imposed after isola- tion from grazing. Comparison of root-weight data from grazed
Table 3. Ovendry roof weighf in ihe 4-foof profile and percenf of fhe weighf af each depfh for N-levels, pasfures, and years.
Pastures
Average Moder-
root Depth N-levels Heavily ately Years
weight (In.) O-N 30N ____- 90N grazed grazed 1961 1962
Grams/sample Om.93 16.36 16.08 15.35 15.56 16.99 13.92
- -
Percent O-6 60.8 62.8 57.6 63.1 57.8 55.6 66.3
of total 6-12 15.9 15.1 15.9 14.9 16.4 16.4 14.7
o-12 76.6 77.9 73.5 78.0 74.2 72.0 81.0
12-24 13.9 13.5 16.1 13.6 15.3 16.8 11.6
24-36 6.3 5.5 7.3 5.5 7.3 7.7 4.8
36-48 ____ 3.1 3.1 3.1 2.9 3.2 3.5 ____- 2.6 ‘Means under the same main heading and underscored by the same line do
not differ significantly at the 5% level (Duncan 1955).
Table 4. Comparison of ovendry rooi weigh& and percenf of fhe weighi af each depfh in grazed areas with fhose from nonferfilized plofs isolafed from grazing in 1951 and mowed abouf Augusi 1 each year fhereaffer. _~~___~______
_________ -_________-
Root Depth Heavily grazed Moderately grazed
weight (Inches) Grazed Mowed Grazed Mowed
-~__-- ~__~______ _____p-
Grams/sample O-48 14.14 13.92 14.64 13.95
Percent O-6 66.6 65.8 57.3 57.2
of total 6-12 12.8 14.6 15.9 17.2
o-12 79.4 80.4 73.2 74.4
12-24 14.8 12.0 15.8 14.8
24-36 3.8 5.0 7.9 7.4
36-48 2.0 2.6 3.1 3.4
______ ________ ______- _______
areas in each pasture with data from non-fertilized plots mowed annually (Table 4) verifies the small difference in root weight between the two pastures. How- ever, comparison of percentages of roots at each depth shows that the moderately grazed pasture had a greater percentage of its roots at each depth below 6 inches than did the heavily grazed pasture. This was true for the area isolated from grazing as well as for the continuously grazed area. Thus the effects of previous grazing intensity were still evident when depth of root- ing was considered. Distribution in the profile as well as total root weight is important in eval- uating the effects of treatments on the root system.
Difference between the mean root weights at various depths sampled and the N x Depth in- teraction was highly significant.
However, the percentage of the total root weight at each depth often changed very little, even though N increased total root weight. Within each year, the root distribution by depths was more consistent for the plots in the moderately grazed pasture than for those in the heavily grazed pasture. The percentage of the root weight below the first foot increased with increasing N- level for the plots in the heavily grazed pasture, but it changed very little or decreased for the plots in the moderately grazed pasture.
ever, a higher percentage of the roots was found in the upper foot, with a lower percentage at each of the lower depths in 1962. The difference in root weight between years (Table 5), and the increase in percentage roots below 1 ft from use of N, were greater for the plots in the heav- ily grazed pasture than for those in the moderately grazed. During the relatively dry season of 1961, root development below 1 ft was increased in the heavily grazed pasture, especially when N was applied. Perhaps these extra roots exhausted the subsoil mois- ture during 1961 and died prior to the 1962 sampling. During the moist season of 1962, root con- centration increased in the upper foot. This was evident for the plots in the moderately grazed pasture and for the O-N plots in the heavily grazed pasture. How- ever, the percentage of roots in the second foot increased for the N plots in the heavily grazed pasture.
The plots isolated from graz- ing for various lengths of time in the heavily grazed pasture were not replicated, and al- though root data were consistent with the variation that was due to year of sampling, no pattern of response to length of isolation was established (Table 6). Fol- lowing a slight increase during the first 2 or three years, root weight tended to decrease with time in isolation. Distribution by depth did not vary much within each sampling year and was sim- ilar to the averages for the fer- tilized plots and grazed areas of the heavily grazed pasture. Years and N appeared to have had greater influence on root de- velopment and distribution than did isolation from grazing.
There is no way of knowing root weight and distribution prior to application of N, because the pastures were not sampled at that time. If we assume that the relative root development in the grazed areas was the same
LORENZ AND ROGLER
then as when root samples were taken from the plots, we can make other .assumptions. Soil moisture in the 6-ft profile of the heavily grazed pasture aver- aged 17.90 and 17.15 inches in May and October, respectively, for the ‘I-year period, 1952 through 1958. Comparable aver- ages for the moderately grazed pasture was 13.87 and 12.08 inches. In both May and Octo- ber, the heavily grazed pasture had an average of 4.05 inches more water in the 6-ft profile than did the moderately grazed pasture. Of this additional water, less than 0.40 inch was in the upper 2 ft and over 3.65 inches were in the rest of the 6-ft pro- file. Soil moisture used from the upper 2 ft was very similar for the two pastures; but much less of the subsoil moisture was used in the heavily grazed pasture. This suggests a more active root system at greater depths under moderate grazing, a possibility which would agree with the ac- tual percentage root distribution found when these pastures were sampled.
Soil moisture samples were not taken in the fertilized plots dur- ing the first 3 years after fer- tilizer application began. How- ever, soil moisture was mea- sured in the grazed area and in the fertilized plots of the heav- ily grazed pasture from 1954 through 1958. Average water content of the 6-ft profile in Oc- tober was 16.04, 11.58 and 10.33 inches for the grazed area, the 30-N and 90-N plots, respectively. Again differences in the upper 2 ft were small, ranging from 3.78 for the grazed area to 3.06 for the 90-N plot. Averages for the lower 4 ft sampled were 12.26, 8.11 and 7.27 for the grazed, 30-N and 90-N treatments, re- spectively. Evidently N stimu- lated root development and ex- traction of soil moisture from the subsoil. May and October soil moisture was almost identical in the lower 4 ft, but in May the
131
upper 2 ft contained more water than in October. Winter precipi- tation generally brings the soil moisture of the upper 2 ft to about the same level for all treat- ments. Cool-season grasses start to use moisture very early in the spring; thus the N plots, which
are dominated by western
wheatgrass, had extracted from 0.5 to 1 inch of water from the upper 2 ft before the May sam- pling. Apparently, if subsoil moisture has accumulated, N will stimulate root development in the moist soil. The stored subsoil moisture under heavily grazed range may account for the burst of production reported during the early years of fertilization of this study (Rogler and Lorenz,
1957). After extraction of subsoil moisture from the N plots, the vegetation used seasonal precipi- tation as it accumulated which prevented recharging of the sub- soil. Consequently, root growth below the 2-ft depth was limited by lack of subsoil moisture in the N plots.
The nutrient removal pattern also suggests that N increased the root activity substantially at the greater depths at some time prior to sampling. Smika et al. (1961) reported a significant in- crease in total soil N for the 0- to 6 and 6- to 12-inch depths, as N rates increased on the plots in the heavily grazed pasture. How- ever, when N was applied total soil N decreased in the third foot and remained the same at greater depths. As N rates in- creased, available P decreased at all except the top foot of the 6- ft profile.
_-
132 GRAZING AND FERTILIZATION
Table 5. Ovendry roof weight in the 4-foot profile and the percent of the iota1 weight found af each depfh from fertilized plots in the heavily grazed and moderately grazed pastures.
Heavily grazed Moderately grazed
Average 1961 1962
root Depth 1961 1962
weight (Inches) O-N 30N 90N O-N 30N 90N O-N 30N 90N O-N 30N 90N Grams/sample O-48 15.89 19.00 18.05 11.92 13.83 13.40 15.51 16.56 16.90 12.35 16.04 15.96
Percent O-6 62.4 64.5 56.2 69.1 67.5 61.2 49.6 52.6 46.7 64.8 67.3 67.7 of total 6-12 14.7 14.4 16.7 14.5 12.7 15.9 17.8 18.1 16.9 16.6 14.8 13.9
o-12 77.1 78.9 72.9 83.6 80.2 77.1 67.4 70.7 63.6 81.4 82.1 81.6 12-24 15.5 12.4 16.9 8.5 11.9 15.0 18.1 17.8 20.7 11.7 11.7 11.2 24-36 4.7 5.3 7.0 5.4 5.1 5.1 10.3 7.6 11.8 4.4 4.0 4.7 36-48 2.7 3.4 3.2 2.5 2.8 2.8 4.2 3.9 3.9 2.5 2.2 2.5
Table 6. Ovendry roof weighfs and percent of fofal weighi af each depth sampled in 2 consecufive years from plots isolated from grazing for various lengths of time in the heavily grazed pasture.
1961 sampling 1962 sampling
Root Depth Years after isolation Years after isolation
weight (Inches) 10 8 6 4 2 0 11 9 7 5 3 1 0
Grams/sample O-48 12.52 14.66 17.58 15.33 18.45 18.15 11.48 11.15 11.74 12.37 13.23 8.54 10.08
Percent O-6 58.0 57.2 63.0 65.2 72.0 60.3 68.3 68.3 78.8 73.6 78.5 72.7 73.0 of total 6-12 14.5 18.1 12.9 15.3 11.2 15.2 14.5 13.0 10.0 12.5 10.1 15.2 10.4
o-12 72.5 75.3 75.9 80.5 83.2 75.5 82.8 81.3 88.8 86.1 88.6 87.9 83.4 12-24 18.2 18.3 20.0 10.8 9.9 16.0 11.5 12.6 7.4 10.1 7.9 8.4 13.5 24-36 5.9 4.1 3.1 6.7 4.2 5.5 3.6 4.0 2.5 2.3 2.1 1.8 2.1 36-48 3.4 2.3 1.0 2.0 2.7 3.0 2.1 2.1 1.3 1.5 1.4 1.9 1.0
grazing, but the percentage of the total root weight found at each depth was not the same for both pastures. A larger percent- age of the root material was found at each depth below the upper foot in the moderately grazed than in the heavily grazed pasture. Application of N to plots isolated from grazing greatly reduced this difference.
N significantly (1% level) in- creased root weight. Although the second increment of N sig- nificantly (1% level) increased top growth, it did not produce any additional root weight. Thus the root:top ratio was much lower for the 90-N than for the 30-N treatment.
Differences between years of sampling were significant (5% level). The total root weight was greatest in the drier of the 2 years. We found a higher per- centage of the roots in the upper foot in the wetter year.
An attempt was made to
re-
late the root data to previously published soil moisture and soil chemical data obtained from the same plots. The pattern of soil moisture and nutrient extraction suggests that, sometime after fer- tilization began (but prior to sampling) the root system must have been larger at the greater depths. Precipitation was too low during this period to recharge the subsoil; thus, after the sub- soil moisture which had accumu- lated under the heavily grazed pasture was depleted, the root system was restricted to the area of the profile recharged by an- nual precipitation. Soil moisture data explain the unusually large forage production during the first few years of fertilization in the heavily grazed pasture.
LITERATURE CITED DUNCAN, DAVID B. 1955. Multiple
range and multiple F tests. Bio- metrics 11: l-42.
HYLTON, L. O., JR., A. ULRICH, AND D. R. CORNELIUS. 1965. Comparison of nitrogen constituents as indi- cators of the nitrogen status of Italian ryegrass, and relation of top to root growth. Crop Sci. 5:21- 22.
LORENZ, RUSSELL J., AND GEORGE A. ROCLER. 1964. Effect of row spacing and nitrogen fertilizer on produc- tion of irrigated Russian wildrye
(Elymus junceus Fisch.). II. Rela- tive crown and root development. Agron. J. 56:7-10.
LORENZ, RUSSELL J., AND GEORGE A. ROGLER, 1966. Root growth of northern plains grasses under various fertilizer and manage- ment treatments. Amer. Forage
and Grassl. Council Proc. Feb. 1966: l-10.
ROGLER, GEORGE A., AND RUSSELL J. LORENZ. 1957. Nitrogen fertilization of northern Great Plains range- lands. J. Range Manage. 10: 156-
160.
SMIKA, D. E., H. J. HAAS, G. A.
Seeding Sherman Big Bluegrass
PAT 0. CURRIERange Scientist, Rocky Mountain Forest and Range Experiment Station,1 Fort Collins, Colorado.
Highlight
Sherman big bluegrass was suc- cessfully esiablished by pJanfing info summer-fallowed land with a double- disc, depfh-band drill fo confrol seed- ing depfh at %-inch. Planting during July and Augusf inio a moisi seed- bed gave optimum seedling esfablish- menf. Weed competition and erosion on the summer-fallowed land was reduced by leaving fhe ground in rough-plowed condition until im- mediately before seeding.
Sherman big bluegrass, a se- lected strain of Poa ampla Merr. indigenous to the Pacific North- west, has been introduced to sev- eral areas within the Rocky Mountain Region (McGinnies et al., 1963). For this region, it has been most successful at eleva- tions above 7,000 ft, and where average annual precipitation ap- proaches or exceeds 14 inches. Big bluegrass is a productive bunchgrass, but it frequently has been difficult to establish in its adapted range (Hyder and Sneva, 1963). Because of the establish- ment problem, some cultural and environmental requirements of this species such as seedbed prep- aration, seeding depth, and time of seeding were studied at the Manitou Experimental Forest, Colorado, from 1963 to 1965, pre- liminary to planting it for graz- ing experiments.
Study Area and Seeding Methods The Experimental Forest is situated 28 miles northwest of Colorado Springs, Colorado, in the ponderosa pine zone at an elevation of approximately 8,000 ft. Summer temperatures are cool; they seldom exceed 90 F. in the daytime and at night are near freezing. Winters are open, but are cold with temperatures occasionally as low at -40 F. Plant growth usually begins in late March or early April, with the growing season ending in
September or October. However, frosts, which temporarily retard plant growth, are common early or late in the growing season.
Annual precipitation at Forest
Headquarters averages 15.5
inches, with approximately three-fourths of it falling during the spring and summer months. Plant growth or forage produc- tion, particularly on seeded ranges, is closely associated with the amount of rainfall received during the growing season (Cur- rie and Smith).2
Alluvial soils derived from Pikes Peak granite are charac- teristic of the area. These soils are sandy loams or sandy-clay loams that are porous when wet and very hard when dry. They are highly erodible and of low fertility, with only moderate amounts of organic material.
Abandoned fields, which were last farmed during the late 1930’s, were plowed and seeded to grass for re- search purposes in the mid 1940’s. For the present work, the study areas were plowed with a moldboard plow and cultipacked before seeding, fol- lowing the recommendations of Mc- Ginnies (1962) for firming light-tex- tured soils. Seeds were planted in rows 12 inches apart except for the broadcast treatment. This is the maximum spacing recommended by Hyder and Sneva (1963) for seeding big bluegrass. All treatments were seeded at a rate of 5 lb/acre. The seed was registered Sherman big bluegrass grown near Pullman, Washington, but obtained locally.
Season and depth of pZantinb.- A complete factorial experiment in three replications of randomized blocks was used to evaluate spring and fall planting and three seed placement treatments. The plantings were made on lo- by 25-ft plots at two seasons: fall, October 2-3, 1963, and spring, April 13-14, 1964. Seeds were hand broadcast and raked, drilled to a 0.5-inch depth or drilled to a l-inch depth. Drilled plots were
planted with a single-row double- disc cone-type seeder.3”
Seedlings on each plot were counted within three random l- by 5-ft subplots. Where seeds were drilled, the plot frame was placed across adjacent rows and the plants counted in five individual rows. Since seeds planted to the l-inch depth in the fall germinated and emerged soon after planting, seed- lings on this treatment were first counted in November 1963. Seedlings on all trials were counted in June 1964, including plants on the fall- drilled, l-inch treatment.
Fertilizer trials--A summer seed- ing was made during the first week of August 1964, with only a %-inch planting depth. Plot size, row spac- ing, and seeding rate were the same as before, but commercial fertilizers were applied to determine whether they increased grass establishment as reported by Cosper and Alsayegh
(1964). At the time of planting, 50 lb/acre of elemental N, P, or K was applied as a top dressing in all possi- ble combinations to plots in three replications. Plant counts were made as described previously.
Field seedings-In the summer of 1965, two 45-acre blocks were seeded to Sherman big bluegrass for a graz- ing experiment. One block, plowed during the summer of 1964, was fallowed over-winter and then disked just prior to cultipacking and planting. The small area used for the 1964 fertilizer trials was withdrawn from this block. The other block was plowed in the spring of 1965, fal- lowed until mid-summer, and then cultipacked immediately before planting. It was not disked except to level furrows or break up old plant clumps that remained on a few isolated areas.
Planting was started the last week in July and continued intermittently until late August. Seeds were drilled to a %-inch depth with the double- disc, depth band, grass drill described by Bement et al., (1965).s” These areas were also planted at a rate of 5 lb/acre in rows 1 foot apart. Random counts of the number of seedlings per foot of row on square-foot plots were made throughout the go-acre seeding in September 1965. Seedlings on 100 plots were counted in each 45-acre block.
Germination tests - Germination was tested at the U.S.D.A. National
FIG. 1. On plots which received 50 lb/acre of nitrogen (left), plants were taller and
more vigorous than those which received no fertilizer (right).
FIG. 2. Sherman big bluegrass planted in
Manitou Experimental Forest.
Seed Storage Laboratory in Fort Collins, Colorado, to determine the length of time big bluegrass normal- ly requires to germinate and the temperature levels which provide good germination. The tests were made following standard procedures in germinators which controlled light, and the degree and duration of a temperature regime.
Results and Discussion Environment-Bluegrass R e 1 a-
tions-Maximum germination of 79’;: was obtained with a 12-hr alternating temperature of 15 C
(59 F) and 30 C (86 F) . This was 1% more than the guaranteed
late July 1965. Photo October 6, 1965,
germination given in the seed analysis. Sixty-six percent of the seed germinated within the first 10 days, and an additional 13% germinated in the next 12 days. The seed was non specific for light, and germinated quickly with favorable moisture and temperatures. It did not have a dormancy problem.
At Manitou, both moisture and temperature were closest to opti- mum for planting bluegrass dur- ing July and August (Table 1). Moisture increases considerably from March to May, then de- creases slightly until convection-
al storms in July make this the wettest month. These intermit- tent storms usually continue into late August or early September. Storm activity then decreases, with a resultant decrease in moisture. Thus, over 6 inches or almost one-half of the average growing-season rainfall is re- ceived in July and August, which are also the warmest months.
Season and depth of planting- The differences in number of bluegrass seedlings per ft2 on the spring and fall plantings were significant at the 5% level for season, planting treatments, and the interaction of planting treat- ments within a season. More seedlings came from spring seed- ing than fall seeding on all plant- ing treatments (Table 2). For the 0.5-inch fall planting, an average of only 2.5 seedlings ft2 were counted the following spring; on the l-inch treatment there was a small decrease in plant numbers from the fall count. These results showed that, to obtain a success- ful seeding, big bluegrass should be planted only when conditions are favorable for rapid germina- tion and emergence.
Drilling the seed in the spring to a 0.5-inch depth was the most successful planting treatment. It produced almost twice as many seedlings per ft2 as the l-inch depth, and 10 times more than the broadcast treatment (Table 2). Also, the seedlings on the 0.5- inch treatment were rather uni- formly distributed, with one or more plants per foot of row, while seedlings in the broadcast treatment were unevenly dis- tributed.
CURRIE 135
Table 1. Average precipitation (inches) and maximum-minimum air temperatures (c) from March through September at the Manitou Experimental Forest Colorado.
~~ ___- Maxi- Mini-
mum mum
Precip. Temp. Temp. Month 1941-65 1960-65 1960-65
-_ March
April May June July August Sept.
0.76 11 -15
1.67 18 - 9
1.83 20 - 7
1.55 24 - 1
3.33 29 3
2.88 28 2
1.03 26 ______ - 2 bers averaged 1.8/ft of row in November 1963. By June of 1964, there was an inconsequential re- duction in plants, which showed that winter mortality was of minor importance. In addition, the seedlings which overwintered became large, robust plants that produced seedstalks the follow- ing summer. Seedlings on the 0.5- inch planting treatment that emerged in the spring grew slow- ly, however, and did not produce seedstalks that year. This rapid emergence and better plant growth were believed to be re- sponses to higher soil moisture at the deeper planting depth. Thus a compromise, although small, of planting to a s/s-inch depth was used for the fertilizer trials and summer field plant- ings.
Fertilizer trials-There were no statistically significant differ- ences in the number of big blue- grass plants established as a re- sult of fertilizer treatment, which agrees with results from fertil- izer trials in Oregon (Hedrick et al., 1964). Establishment from summer seeding in 1964 was good, even though precipitation during July and August was about 1 inch less than average in each month. By June of 1965, the number of l-year-old plants averaged 6.5 with a standard error of 0.91/ft of row, and there were noticeable differences in plant growth. As shown in Fig. 1, plants which received nitrogen
were larger and much more
Table 2. Average number of Sherman big bluegrass seedlings (per ff? by season and planiing treatment, Manifou Experimenfal Forest.
-__ ~~_ __ _ __~
Season planted’ Planting treatment2 ____~
and date Drilled Drilled
plants counted Broadcast 0.5-inch deep l-inch deep Average Fall 1963:
November 1963 June 1964 Spring 1964:
0 1.0
June 1964 Average:
1.4
June 1964 1.2
~___
Significance level P = .05 1 Sx = t 1.41 plants 2 Sx = t 2.46 plants
vigorous than the others. The benefits of adding either phos- phorous or potassium were small, but they too increased vigor and plant growth a small amount.
Field plantings - By applying the information obtained from the several plot trials, good stands of Sherman big bluegrass were obtained on the 1965 field plantings. Moisture in the upper few inches of soil was near field capacity from mid-July through August, when the plantings were made. Because seed was drilled into a moist seedbed with favor- able temperatures, much of it germinated and emerged in 7 to 10 days. The rows were uniform- ly filled, and by the first week in October 1965, the plants aver- aged approximately 5 inches tall (Fig. 2). Seedling numbers throughout the 90 acres averaged 24/ft of row, and there were no large differences in seedling numbers between the two blocks.
The field plantings showed, however, that invasion of weeds and soil erosion were influenced by land treatment and should’be considered in establishing big bluegrass. In July 1964, for ex- ample, the area plowed for the field seeding included the plot trial area used for the fertilizer study. This small area was culti- packed immediately, but the re- mainder was left in a rough- plowed condition. Many undesir- able species invaded the culti- packed area, while the adjacent plowed area remained relatively
__-_____- --__-
0 1.8
2.5 1.5 1.7
13.2 6.4 7.0
7.8 3.9 4.3
__~__~
free of competing vegetation. The fertilizer treatments un-
doubtedly stimulated weed
growth, but the check or unfer- tilized plots were also occupied by weeds. Fringed sagebrush (Artemisia frigida Willd.), which was common on the whole area prior to plowing, was particular- ly abundant on the small area which was cultipacked soon after plowing but not on the area left rough plowed.
Erosion was not a problem un- til after the area was cultipacked. The area left rough plowed from July of 1964 until the early sum- mer of 1965 accumulated mois- ture in the furrows, but there was very little soil movement even during intense storms. After it was cultipacked, rill and sheet erosion became a problem. For control of erosion and weeds, therefore, it is beneficial to leave an area rough plowed until just prior to planting. If summer seeding conditions are favorable, the area can then be cultipacked and planted. With rapid germi- nation and establishment of seed- lings, the land is vulnerable to erosion for a minimum amount of time. If summer seeding does not seem feasible because of in- sufficient moisture, seeding could be delayed until the following spring to take advantage of over- winter moisture accumulation.
136
ful establishment of Sherman big bluegrass were studied at the Manitou Experimental Forest, Colorado, from 1963 to 1965. Rec- ommendations for seeding areas having similar soil and climatic conditions are as follows:
1. Sherman big bluegrass should be planted into a moist seedbed in July or August. The seedlings can be expected to emerge 7 to 10 days after plant- ing and be well established with- in 2 to 3 months. Bluegrass emer- gence is poor if the seed must remain in the ground for a pro- longed period of time. Although spring seeding is less favorable, it is a possible alternative pro- viding soil moisture is good.
2. On sandy-loam or sandy- clay-loam soils, seed should be drilled as uniformly as possible to a 0.5- or %-inch depth. Five pounds per acre at a maximum la-inch row spacing is a sug- gested seeding rate. A double-
SEEDING BIG BLUEGRASS
disc, depth-band or comparable grass drill is recommended for controlling seed placement depth. 3. Leave the soil rough plowed until just prior to seeding to re- duce the establishment of weeds and the interval the ground is susceptible to erosion.
1 Forest Service, U.S. Department of
Agriculture, with headquarters at
Fort Collins, Colorado, in coopera- tion with Colorado State Univer- sity.
2 Currie, Pat 0. and Dwight R.
Smith. Response of seeded ranges to different grazing intensities in the Ponderosa Pine Zone of Colo- rado. 1966. (In preparation, Rocky Mountain Forest and Range Exp. Sta., U.S. Forest Serv., Fort Col- lins, Cola.).
3 Special seeding equipment used in
the study was obtained from: a)
Crops Research Division, Agricul- ture Research Service, Fort CoZ- lins. b) Forestry and Range Sec- tion, Colorado Agricultural Experi- ment Station, Colorado State Uni- versity, Fort Collins.
%
Effect of Grazing on Soil Compaction
as Measured by Bulk Density on
A
High Elevation Cattle Range
WILLIAM A. LAYCOCK AND PAUL W. CONRAD
Plant ecologist and assistant range scientist, at the U.S. Forest Service Intermountain Forest and Range Experi-
ment Station’s Forestry Sciences Laboratory, ‘Logan,
Utah. Highlight
Bulk density of fhe soil in grazed plofs was similar fo fhaf in ungrazed exclosures both in early summer be- fore grazing and in lafe summer affer grazing. Increases in bulk den- sify during fhe summer bofh in grazed and ungrazed areas were af- fribufed fo changes in soil moisture. Soils in early summer were moisf and swollen and fhus weighed less per unif volume fhan did fhe dry soils in laie summer.
Rotation and rest-rotation grazing systems are now being applied with increasing frequen-
-
1 In this paper the term “significant” will refer to the 5% level of proba-
bility and “highly significant” will refer to the 1% level.
cy on the arid rangelands in the West. These systems require heavy concentrations of livestock during one grazmg season or por- tion thereof, followed by com- plete rest from grazing during the remainder of the season or the following year. Some land managers fear such concentra- tion of animals may cause seri- ous soil compaction that will not be overcome during the rest period.
Relatively few studies have been made to determine how trampling by grazing animals af- fects the soil. Studies conducted
LITERATURE CITED
BEMENT, R. E., R. D. BARMINGTON, A. C. EVERSON, L. 0. HYLTON, JR., AND E. E. REMMENGA. 1965. Seed- ing of abandoned croplands in the Central Great Plains. J. Range Manage. 18: 53-59.
COSPER, H. R., AND A. Y. ALSAYEGH. 1964. Can fertilizer aid in estab- lishing grass on native range. Range Improvement Notes 9 (3) :
5-9. U.S.D.A., Intermountain Re-
gion, U. S. Forest Service.
HEDRICK, D. W., D. N. HYDER, AND F. A. SNEVA. 1964. Overstory-un- derstory grass seedings on sage- brush-bunchgrass range. Ore. Agr. Exp. Sta. Tech. Bull. 80. 31 p. HYDER, D. N., AND F. A. SNEVA. 1963.
Studies of six grasses seeded on sagebrush-bunchgrass range. Ore. Agr. Exp. Sta. Tech. Bull. 71. 20 p. MCGINNIES, W. J. 1962. Effect of seedbed firming on the establish- ment of crested wheatgrass seed- lings. J. Range Manage. 15: 230-234. MCGINNIES, W. J., D. F. HERVEY,
J. A. DOWNS, AND A. C. EVERSON. 1963. A summary of range grass seeding trials in Colorado. Colo. Agr. Exp. Sta. Tech. Bull. 73: 81 p.
9
in the more humid eastern or midwestern States have found bulk density is higher in grazed areas than in similar ungrazed areas (Lull, 1959; Reynolds and Packer, 1963; Linnartz, et al., 1966). Studies of soil compaction on arid rangelands, however, have produced somewhat con- flicting results. Daubenmire and Colwell (1942) and Meeuwig