Johnson Grass Control
Heard, H. C.
College of Agriculture, University of Arizona (Tucson, AZ)
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University of Arizona
Agricultural Experiment Station
Rootstocks on seedling Johnson grass plant
By H. C. Heard
For about thirty years Johnson grass has spread, at first slowly and then with increased rapidity, at altitudes of 4000 feet and below, throughout Arizona. In some cases its introduction was no doubt acci-dental; but in other instances it is known to have been planted by irrigating farmers as a hay crop, and by stockmen as an emergency forage. Johnson grass is therefore now well distributed over grazing ranges, along water courses, and throughout the lower irrigated valleys of the State. While this plant, with its fleshy rootstocks, may serve beneficially as an emergency forage, and as a soil binder to prevent erosion, its main effect is as a pestiferous weed in irrigated valleys, preventing" the profitable culture of summer crops and depreciating land values seriously.
The State has endeavored to regulate this weed by means of a law prohibiting all traffic in Johnson grass plants and seed, or its culture, but with little effect upon the pest.
Many attempts have been made by the farmers themselves to exter-minate or control Johnson grass. Continuous dry fallowing of infested fields is practiced; sheep are to some extent being used along ditches and weedy roadsides; and "easy methods" of soil treatment by chemicals, steam, or otherwise, have been proposed; but more and more it is being found that intelligent and persistent cultural methods based on a knowl-edge of the plant and the effective use of crop rotations, are most cer-tainly successful. Intensive cultivation of valuable summer growing crops, such as cotton and Indian corn, is perhaps the most effective means of disposing of Johnson grass, seconded by winter growing crops of grain, lettuce and various vegetables,
Not only may Johnson grass be effectively and economically con-trolled "by cultural methods, but a benefit may be derived from it, inas-much as it is observed that old Johnson grass land enriched with quantities of organic matter derived from decayed rootstocks is more productive than ordinary soil. In 1917, 41 to 50 bushels of wheat per acre were grown at the Salt River Valley farm on land that had been badly infested with Johnson grass.
It may be, therefore, that Johnson grass, like some other apparent misfortunes, handled with energy and determination, will prove a -blessing in disguise,
R. H. FORBES, Director.
Introduction 339 Operations in detail • • 340 Field C ; summer fallow, winter grain • - —340 Field D ; summer fallow, winter grain 341 Field E; intensive cultivation, cotton and corn 343 Field F; intensive cultivation, corn and cotton 345 Field G; summer fallow, winter grain 346 Field H ; continuous dry fallow • • 347 1 interpretation of results • • 352 Summary and conclusions • • 354
Fig. 1. Vigorous Johnson grass rootstocks Frontispiece Fig. 2. Johnson grass rootstocks exhausted by close grazing with
sheep Frontispiece Fig. 3. Field E, August, 1915 342 Fig. 4. Field E, May, 1916, showing type of cultivator and sweeps used 343 Fig. 5. Field E, June, 1916 343 Fig. 7. Field F, October, 1916 344 Fig. 8. Johnson grass on Fields G and H, July, 1915 345 Fig. 9. Wheat on Field G, May, 1016; no Johnson grass in sight 346 Fig. 10. Field H, June, 1916; few Johnson grass plants appearing. 347
Table I Field C, 40 acres; summer fallow, winter grain 349 Table II. Field D, 20 acres; summer pasture, winter grain 349 Table III. Field E, 10 acres; intensive cultivation, cotton and corn , . .349 Table IV. Field F, 10 acres; intensive cultivation, corn and cotton 350 Table V. Field G, 20 acres; summer fallow, winter grain 350 Table VI. Field H, 20 acres; continuous dry fallow .351 Table VIT. Summaiy of costs and returns "from July, 1915, to November,
F'g. 1.—Vigorous Johnson grass rootstocks.
Johnson Grass Control
(Sorghum halep ense)
For several years the need for data on the control of Johnson grass in the irrigated valleys of Southern Arizona has been manifest. An excellent opportunity for experimental work in the eradication of this weed under average farm conditions was offered when the Agricultural Experiment Station began to operate the Salt River Valley Farm near Mesa. Half of this tract of land was infested with a perfect stand of Johnson grass and about 40% of the other half of the farm was very heavily seeded to the weed.
As is well known, Johnson grass at an intermediate stage in its growth sends out a fleshy rootstock in which is a considerable quantity of stored up substances, capable of supplying new plants formed at the nodes of this rootstock. As a result, if the above-ground part of the plant is destroyed, food materials stored in the rootstock are capable of producing new foliage,-which, after it again has made a slight growth, is maintained by its fibrous roots and by the nutritive pro-cesses which are carried on in the leaves and stems. Since the growth of all of the higher plants is dependent upon plant foods derived from two sources ; first, the soil solution through roots, and second, from the air by means of synthetic processes carried on in leaves and sterns and assisted by sunlight; and since neither is sufficient in itself to maintain the life of the plant, the destruction of Johnson grass may be accomplished by cutting off one of these sources of supply, thus forcing the stored up substances in the rootstocks to maintain the plant, continuing this process until the reserves in the rootstocks are exhausted. Two means of thus disturbing the normal processes of Johnson grass plants were chosen; the destruction of the stems and leaves by cultivation, and by close-grazing with livestock. For the latter method sheep were selected.*
* Acknowledgements.—The writer desires to state that the experimental work leading to this publication was planned by Professor John F. Nicholson prior to his departure in February, 1917, the program being carried out and the publication written by himself.
340 BaLLivriN 82
It was also deemed advisable to attempt the control of Johnson grass by reducing the vitality of the rootstocks by exposing them to intense sunlight, sun-heat, and aridity. It appeared desirable to sup-plement this method with more or less cultivation.
In carrying out the above plan six fields were laid out : Field C, a 40-acre tract, was set aside to be held fallow from the time of removal of a wheat crop in June, 1915, until December, 1916, at which tune another grain crop was to be planted. After the removal of the second crop, when the land was sufficiently freed from Johnson grass, it was planned to seed it to alfalfa.
Field D, containing 20 acres, had been in sorghums for a number of years until November, 1915, v\hen it was plowed and seeded to barley After the removal of the barley crop plans \\ere made to pasture the field with sheep until such time as the Johnson grass should be under perfect control.
Fields E and F, each containing 10 acres, were set aside for the use of summer crops which demanded considerable cultivation. The crops chosen were Egyptian cotton and dent corn, to be alternated each year Field G, containing 20 acres, \\as to be dry fallowed during the summers and planted to grains during the winters.
Field H also contained 20 acres on which a continuous dry fallow \\ as to be maintained until the experiment should close.
OPERATIONS IN DETAIL
FIEXD C ; SUMMER FALLOW, WINTER GRAIN
Following the removal of wheat in June, 1915, Field C was kept dry and plowed during the following August, being left rough through-out the succeeding winter. Early in the spring of 1916 there was a luxuriant growth of volunteer grains. The summer plowing of the previous year had very greatly reduced the vitality of the Johnson grass rootstocks and almost all of the weed that was evident in the spring of 1916 was a seedling growth which had been germinated by the winter rains just preceding. To prevent these seedlings from attaining sufficient maturity to send out new rootstocks the land was again plowed in April, 1916. Summer rains caused the germination of still more seed and a third plowing was made in August, 1916, prior to seeding small grains in December. At the time of seeding virtually no old Johnson grass plants with appreciable vitality were noted The small grains planted at this time were harvested in June, 1917, and the land was left dry until August at which time it was plowed prior to seeding to alfalfa in November. By the time of this last plowing
JOHNSON GRASS CONTROL 341 almost all of the Johnson grass had been destroyed and without ques-tion the pest can easily be controlled in future by digging out the very few remaining plants with a shovel or a grub hoe.
FIELD D; SUMMER PASTURE, WINTER GRAIN
The stand of Johnson grass on this field in 1915 was about as heavy as could be grown. It was plowed in November of that year and seeded to barley in December. The perfect stand and vigorous growth of barley in the spring of 1916 served to hold the Johnson grass well m check until the harvest in May. At this time the land was sufficiently dry to prevent rapid growth of Johnson grass without irrigation. In the middle of June, 1916, the land was irrigated and enough sheep were turned in to graze closely all edible weeds. In order to force the Johnson grass to send out new foliage and thereby hasten the exhaustion of the rootstocks the irrigations which followed were frequent enough to keep the land very moist at all times. In a very few weeks a marked diminution in the vigor of the grass was noted and, to supply winter pas-ture to supplement the growth of the Johnson grass in late fall and early spring, the land was thoroughly disked in November and seeded to barley in December. Part of this crop, which was more than suffi-cient for the needs of the sheep, was harvested in June, 1917, at which time the Johnson grass appeared to be destroyed. In September it was again plowed preparatory to seeding for pasture and hay purposes, and by the middle of November the remaining Johnson grass plants were so few that a few hours' work of one man sufficed to clean up entirely the 20 acres.
E; INTENSIVE CULTIVATION, COTTON AND CORN
This 10-acre tract, which was very foul indeed (see Fig. 3), was partially mowed and burned over in the fall of 1915. In February, 1916, it was plowed preparatory to planting to cotton. Considerable leveling was necessary and to facilitate this the land was irrigated twice. Soon there was a solid mass of Johnson grass over the entire field and in spite of the fact that the leveling necessitated replowing in March the effect on the Johnson grass was negligible. The cotton was planted about the middle of April and in a couple of weeks was almost hidden by the growth of the weed. Cultivation with sweeps, which cut every bit of vegetation within their path, was started early in May and hoes were used at the same time to chop out the weeds in the cotton rows. A great deal of hoeing' and cultivating was necessary for the next two months, by which time the vigor of the Johnson grass had materially diminished. It was very easy to keep the grass in check the remainder
of the summer, and by December, 1916, virtually no Johnson grass was noticed in the field except that which had grown from seed brought in with the irrigation water used during July and August. At the time of the germination of these plants the cotton was too large to permit of further cultivation, which would easily have destroyed the seedlings. In January and February, 1917, this land was plowred
pre-paratory to a green manuring crop to be turned under before planting to corn. Accordingly the field was irrigated and late in March tepary beans were drilled in very thickly. These beans came up readily and at
Fig. 3.—Field B, August, 1915.
first made satisfactory progress, but due to the lack of nitrogen fixing bacteria in the soil their growth during May was slow. At the same time Johnson grass plants, which had come up from rootstocks devel-oped on the seedlings introduced by the irrigating water of the previous July and August, appeared in such great numbers that the beans were plowed under very early in June. Johnson grass again came up and made necessary the use of a weeder in late June. In the middle of July the land was planted to corn and aside from the necessity for consider-able cultivation and hoeing during the first three or four weeks, the weed was very easily kept under control for the remainder of the sum-mer. Since it was possible to cultivate the corn until quite late in the summer, most of the seedling plants that were brought in with the
Joiixsox GRASS CONTROL 343
Fig. 4.—Field E, May, 1916, showing type of cultivator and sweeps used.
Fig. 6.—Field F, August, 1915.
JOHNSON GRASS CONTROL 345
irrigating water were destroyed. After the corn got too large to culti-vate, a very little hand hoeing removed all traces of Johnson grass.
FIELD F : INTENSIVE CULTIVATION, CORN A N D COTTON
This field, having been mowed and burned over in the fall of 1915, was plowed in April the following year. Plowing, levelling and culti-vating necessitated irrigations late in March, early in June, and early
Pig. 8.—Johnson grass on Fields G and H, July, 1915.
in July. Since the land was held moist during this part of the season great numbers of Johnson grass plants came up, and in the absence of a suitable weeder, had to be kept in check by means of a cultivator. In the middle of July, 1916, corn was planted and for a short time
consid-346 BULLETIN 82
erable cultivation and hoeing was necessary to hold back the Johnson grass. By late fall of that year, however, only seedling Johnson grass brought in by late summer irrigating water, was in evidence. In January and February, 1917, the land was plowed and a good deal of leveling done. This necessitated frequent irrigations, and the soil was at all times moist until after it had been planted to cotton in the mid-dle of March. Very little Johnson grass emerged, however, and what did appear was easily controlled by means of the cultivator and by hoes.
Fig. 9.—Wheat on Field G, May, 1916; no Johnson grass in sight.
FIELD G; SUMMER FALLOW, WINTER GRAIN
This 20-acre field was partially mowed and burned over in the fall of 1915. In March of the following year it was plowed dry. The Johnson grass soon came up again in abundance. The growth was kept in check by means of a weeder until August when the field was replowed. A three-inch rain early in September gave new life to the almost exhausted plants and for a time the weed was nearly out of control. In the middle of December the field \vas irrigated and sown to wheat. A very heavy stand and luxuriant growth of wheat held the Johnson grass in check until June, 1917, when the grain was harvested. The ground being very dry, the growth of weeds fol-lowing the removal of the wrlieat was not rapid but by September
JOHNSON GRASS CONTROL 347
a considerable stand was noted and a large number of rootstocks were being formed. At this time the land was irrigated and deeply plowed. Shortage of labor and horse power prevented plowing immediately after the removal of the grain but if the land could have been worked at that time very much better results would have been obtained. As the field appears in the fall of 1917 the Johnson grass is under control but by no means eradicated.
FIELD H ; CONTINUOUS DRY FALLOW
This field was partially mowed and burned over in 1915. In March and April, 1916, the land was plowed dry and the growth of Johnson grass visibly retarded. Leakage from an irrigating ditch and a heavy rain early in September encouraged the grass until it was very difficult to control with a weeder. By the fall of 1916, while a visible improve-ment had been made, the results obtained were far from what had been hoped for. Late in February, 1917, the field was disked and
partial-Fig. 10.—Field H, June, 1916; few Johnson grass plants appearing.
ly plowed, and during the remainder of the season a weeder was used quite frequently. In September the land was plowed dry preparatory to seeding to grains later in the year. At the present time, November, 1917, the growth of Johnson grass is not very noticeable although there
348 BULLETIN 82
aie many old rootstocks scattered through the field, and the summer rams have brought up a number of seedling plants.
Below is given a series of tables itemizing costs and returns from operations on the various fields.
Labor costs were high, from 25c to 30c per hour being paid for most of the work performed. Prices for crops produced were, however, also high, as much as $3,95 per cwt being received for wheat, and as much as 79c per pound for Egyptian cotton
JOHNSON GRASS CONTROL 351 TABLE vi.—FIELD H, 20 ACRES; CONTINUOUS DRY FALLOW
Year 1916 1917 Grand total--Plowing costs $207.75 56.53 $264.28 Harrow-ing- and disking costs $35.00 30.39 $65.39 Cultivating costs $37.62 $8808 $125.70 Other costs $11538 7414 $189.52 Total costs $395 75 24914 $644.89 Cost per acre $1978 1245 $32.23 Returns per acre None None None
TABLE VII.—SUMMARY OF COSTS AND RETURNS FROM J U L Y , 1915, TO NOVEMBER, 1917 Field
cSummer fallow winter grain. D Summer pas-ture, winter grain. E Intensive culti-vation, cotton and corn. F Intensive culti-vation, corn and cotton. G Summer fallow, winter grain. H Continuous dry fallow. Size in acres 40 20 10 10 20 ' 20 Total costs $1,66030 $89758 $1,46833 $1 767.46 $952 67 $644.89 Total returns $3 440 45 $1 353 55 $1,552,76 $3 885 OC $190623
1Gam $1 78015 $455 97 $8443 $211754 $953.56 vjram per acre in two >rs. $4450 $2280 $8.44 $211.75 $47.67 -$32.24* *Loss Remarks
Johnson grass entirely wiped out except for occasional s e e d 1 i n gs from seed carried in irrigation water.
Very few rootstocks re-maining and vitality of these seriously depleted.
Johnson grass entirely destroyed except for very few seedling plants from seed carried by irrigating water. Johnson grass well un-der control but with a
considerable number of v i g o r o u s rootstocks scattered through the field. With carefully conducted operations on this field Johnson grass will soon be wiped out, but if neglected will be as bad as ever in one
F e w remaining root-s t o c k root-s root-scattered uni-formly over field but with vitality seriously diminished.
352 l » i lit** UN 82
INTERPRETATION OF RESl LTS
In figuring gam or loss in the above tables actual profits were not reckoned since no charge was made for interest on investments, depre-ciation of implements, etc., taxes, and shares of general supervision costs which should be divided among the fields, \ccordingly, actual losses were sustained both by fields E and 11 and actual profits were materially lower on the other fields than figures represented as gam indicate.
Field C: The hardest blow given to Johnson grass on Field C \\as the dry plowing of August, 1915. Leaving this ground rough through-out the succeeding winter also assisted materially. The plowing m April of 1916 made the remainder of the fight easy. In addition, actual profits were swelled materially by the abnormally high prices of grain in 1917
Field D: In spite of the fact that this field did not return a great deal of profit we are led to favor the control of Johnson grass by means of close pasturage. Much greater profits should be realized when such a field is allowed to grow grain in winter and when hogs are turned in to feed upon the rootstocks turned up by plowing. A combination of winter grains and pasturing with both sheep and hogs in the summer is one of the most practicable methods of quickly and surely bringing Johnson grass into subjection.
Fields E and F: The results from Field E appear to be inconsistent with those of Field F. The only difference in treatment of the fields has been the planting of cotton in Field R in 1916 followed by corn the succeeding year, and the reversal of this rotation in Field F. How-ever similar the treatment may appear to have been there is a material advantage in following corn with cotton for the following" reasons: Since corn is not usually planted until late in June or early in July, the most rapid growth of the Johnson grass, which takes place earlier in the season, may be combated by clean cultivation with weeders and results can be obtained more cheaply than with row cultivators and hand hoes. If this early cultivation is carefully done the Johnson grass will be fairly under control by corn planting time and the work neces-sary to keep it in subjection is much less than that demanded earlier in the season. Furthermore, corn can be cultivated later than cotton, and even after it is too large to cultivate with horses the few remaining Johnson grass plants can be easily handled with hoes. In this way plants from seed brought in by the irrigating water of late summer may be destroyed before they have reached the stage where the root-stoclrs are formed. This makes the fight against Johnson grass much
JOHNSON GRASS CONIROL 353 easier the next year when cotton is planted. If cotton is used first the Johnson grass must be fought the hardest at a time when the young cotton plants must be handled with greatest care; and while the old rootstocks of Johnson grass can be brought under control, the growing cotton interferes with late cultivations that should destroy seedling plants from seed brought in by late summer irrigations. Many of these seedling plants by fall form quite large and vigorous rootstocks. This necessitates a great deal of work the following spring before the plant-ing of the next year's crop of corn. If a green manurplant-ing crop is planted on this land prior to putting it in corn a very troublesome growth of Johnson grass will appear before the crop is large enough to be of material advantage to the ground. Thus in Field E, in 1917, a crop of tepary beans had to be turned under before their value as a green manure had paid for the expense of planting them. The financial returns from Field F have been materially increased over those from Field E by virtue of the fact that the prices of cotton in 1917 were almost double the prices for 1916, which also were abnormally high, while the prices of corn did not change correspondingly On account of conditions not regulated by the experiment we secured in 1917 double the yield of cotton obtained in 1916.
Field G - When land is held fallow in summer and seeded to small grains in winter, ample time is available to put the seed bed in perfect shape, and on such land a very high yield of gram may be obtained. Yields of 45 to 50 bushels of wheat per acre, and the abnormally high prices of grains in 1917, left considerable profit from the treatment of Field G. Shortage of labor at critical times and the thorough wetting of the land by a 3-inch rain in early September, 1916, materially reduced the efficiency of our Johnson grass control work on this field. Lack of plowing facilities immediately after the removal of the 1917 grain crop, allowed further opportunity for the recuperation of Johnson grass. As a result, the land is still quite badly infested though not so seriously as to make it particularly difficult to control. If it had been possible for us to conduct all our cultural operations on this field as soon as the need was manifest, there is no question that the Johnson grass would have been almost completely destroyed
Field H: Continuous dry fallow is very effective and does not demand a very great expenditure of labor; but the danger that a heavy rain will undo a good deal that has already been accomplished and the loss of the use of the land makes this method impracticable. While continuous fallow does not demand a great deal of labor it sometimes requires considerable work in a very short time, usually at a season
354 BULLETIN 82
SUMMARY AND CONCLUSIONS
Plowing dry in midsummer is slow, expensive and ver} hard on horseflesh, yet it is much more effective than plowing \\hen the ground is moist or at other seasons of the year. Costs of cli*} plowing m summer with horses have run as high as seven dollars per acre in the work described abo\ e and usually are not lesh than four and one-half dollars per acie Deep plowing in midsummer when the land is very dr) can best be accomplished by means of tractors
The quickest \vay to ncl land < > t Johnson ^rass is to ovei$>raze with sheep, meanwhile inigating irequcntl). The most effective \\ay, as well as the most economical, is the ficqucnt cultivation of a Lite summei crop, such as corn, followed b> another crop demanding much tillage, such as cotton. The exact crops to be chosen should depend upon the market outlook and the probable price \\hich can be realized. The method demanding the least labor and outla> ot cash is dr) fallow in summer followed by winter grams This system ma) be \ cry profitable when grain prices are high.
It is rarely feasible to attempt to rid a place of Johnson grass by following one method alone, but a combination of methods \\ Inch prop-erly distributes the labor, keeps up the fertility of the soil, and returns a steady income, should be adopted.
To control Johnson grass successfully provision must be made for carrying on the desired operations as soon as the need is manifest. A delay of one week may overcome the good effects of several weeks of careful and consistent work.
A method including dry fallow is reasonably effective and econom-ical, but a heavy ram or an accidental leakage of irrigation water may undo a great deal of work.
If Johnson grass is to be eradicated by grazing with sheep more animals must be pastured than the land will satisfactorily maintain, and additional feed must be supplied since the effectiveness of this method depends upon the grass being grazed as closely as possible Further-more, the growth of the Johnson grass must be encouraged in every feasible way, particularly by supplying plenty of moisture, in order to more quickly exhaust the stored up food in the rootstocks.
When Johnson grass is to be killed by the tillage of ordinary farm crops some provision must be made to take care of the seed which is brought in by irrigating water during late summer. In the absence of a suitable seed trap or screen, hand hoeing is usually necessary. John-son grass does not form a rootstock until about the boot stage, which is the time the head is appearing from its enclosing sheath. Prior to
J O I I N S O V GR\SS Co\ IROL 355 this time a Johnson grass plant is killed by any operation which severs it beneath the surface of the ground Therefore, it is especially desir-able to destroy it before the rootstock is formed