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All Graduate Theses and Dissertations Graduate Studies
5-1996
An Integration of Tillage and Herbicides to Control Jointed Goatgrass (Aegilops Cylindrica Host.) in Winter Wheat
Troy M. Price Utah State University
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Recommended Citation Price, Troy M., "An Integration of Tillage and Herbicides to Control Jointed Goatgrass (Aegilops Cylindrica Host.) in Winter Wheat" (1996). All Graduate Theses and Dissertations. 4602. https://digitalcommons.usu.edu/etd/4602
This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. AN INTEGRATION OF TILLAGE AND HERBICIDES TO CONTROL JOINTED
GOATGRASS (AEGILOPS CYLINDRICA HOST.)
IN WINTER WHEAT
by
Troy M . Price
f. thesis submitted in partial fu!fi!lrr.er:t of the requirements for the degree
of
MASTER OF SCIENCE
in
Plant Science
UTAH STATE UNIVERSITY Logan, Utah
1996 ii
ABSTRACT
An Integration of Tillage and Herbicides to Control Jointed
Goatgrass (Aegilops cylindrica Host.) in Winter Wheat
by
Troy M. Price, Master of Science
Utah State University, 1996
Major Professor: Dr. John 0. Evans Department: Plants, Soils and Biometeorology
An integrated management approach for jointed goatgrass control was investigated
at two farms in northern Utah using three tillage regimes and three herbicides. The tillage
regimes included no tillage, conservation tillage, and conventional tillage. Each regime
was composed of different tillage practices common in the Intermountain West. A
preemergence herbicide, clomazone, and two postemergence herbicides, 2,4-D and
glyphosate, were investigated. Greenhouse studies were also conducted to investigate
clomazone efficacy and depth of planting of winter wheat and jointed goatgrass.
Differential sensitivity to clomazone between jointed goatgrass and winter wheat did not occur in the greenhouse for the rates tested. A treatment ofO.ll kg ai ha·1 clomazone reduced wheat and jointed goatgrass fresh weights similarly by 49 and 63%, respectively. Ill
Jointed goatgrass did not germinate below 6.4 em and emergence was initially reduced at the 2.5 em soil depth. Winter wheat emergence was not lowered until the seed was planted 5.0 em deep or deeper and continued to 8.9 em deep.
2,4-D plus glyphosate provided over 95% jointed goatgrass control initially and by midsummer fallow especially when followed by tillage. However, extensive populations of jointed goatgrass seedlings and spikelets were found in the fall prior to initiation of the cropping season. Herbicides did not provide meaningful differences in the jointed goatgrass spikelet or seedling populations. Conventional tillage practices, such as fall or spring chiseling accompanied by three summer rodweedings, provided the greatest control ofjointed goatgrass spikelets and seedlings in the fall following the fallow season. Winter wheat yields reflected this relationship by having five times greater yields in the conventional tillage than in either no tillage or conservation tillage.
(66 pages) iv
ACKNOWLEDGMENTS
I would like to thank Dr. John 0 . Evans for his help and assistance with this research project I greatly appreciate the patience and understanding he demonstrated on my behalf and encouragement to continue on. I also appreciate the help of Dr. Steven A
Dewey for his advice and encouragement Special thanks goes to William Mace and Matt
Larson for their assistance in getting the work done in the fields. I especially appreciate their fiiendship and patience throughout this entire process. Thanks goes out to Richard
Peterson and Leo Erickson for the use of their farms and providing equipment when necessary. Without the use of these farms, this project would not have as easily been accomplished. I also thank my fellow students and other faculty members who provided assistance and encouragement.
I would especially like to thank my wife, Julie, for her patience and love.
Throughout this whole project, she was always there to pick me up and keep me going. thank my boys for their patience with their father and just for being there to support me. greatly appreciate the faith my family has in me. When times were difficult at home, they always showed their love and helped me to feel that I could accomplish this task.
I also would want to thank any fiiends and family members who were always there for me. I love you all and will forever remember the sacrifices you all made to keep me going.
TroyM. Price v
CONTENTS
Page
ABSTRACT ii
ACKNOWLEDGMENTS. . iv
LIST OF TABLES . . vi
LIST OF FIGURES . viii
INTRODUCTION
LITERATURE REVIEW. 3
MATERIALS AND METHODS . .14
Greenhouse Studies . .14 Fallow Season Evaluations .16 Within Crop Evaluations. .21
RESULTS AND DISCUSSION .23
Greenhouse Studies . .23 Fallow Season Evaluations .26 Within Crop Evaluations. .33
SUMMARY AND CONCLUSIONS . .40
LITERATURE CITED . .42
APPENDIX. .47 vi
LIST OF TABLES
Table Page
I. Results of 1993 jointed goatgrass survey reported by Ogg. 4
2. A comparison of tillage regimes regarding number of fallow operations and plant surface residue. . 20
3. Dry weights of wheat or jointed goatgrass plants following domazone treatments under subsurface and surface irrigation. . 23
4. Percentage wheat and jointed goatgrass seedlings emerging at nine planting depths in the greenhouse. . 25
5. Visual estimates of clomazone phytotoxicity to jointed goatgrass, Promontory, UT. (Aprill993) . .27
6. Number ofjointed goatgrass seedlings emerging in fallow following fall tillage and herbicide treatments, Promontory, UT. (April 1993) . 28
7. Number ofjointed goatgrass tillers in midsummer fallow following treatments of 2,4-D +glyphosate and spring and summer tillages, Promontory, UT. (July 1993) .29
8. Number ofjointed goatgrass tillers in midsummer fallow following treatments of clomazone and spring and summer tillages, Promontory, UT. (July 1993) . . 31
9. Influence of selected herbicides on jointed goatgrass emergence in the absence of tillage, Beaver Dam, UT. (July 1994) . .33
10. Numbers ofjointed goatgrass spikelets at three soil depths in seedling winter wheat, Promontory, UT. (October 1993) . .34
II . Numbers ofjointed goatgrass seedlings for three soil depths, Promontory, UT. (October 1993) .35
12. Numbers of jointed goatgrass spikelets for three soil depths, Beaver Dam, UT. (October 1994) .36 vii
13. Numbers ofjointed goatgrass seedlings for three soil depths, Beaver Dam, UT. (October 1994) .37
14. Percentages ofjointed goatgrass and winter wheat in harvest samples and wheat yield, Promontory, UT. (September 1994) .38
15. Analysis of variance for dry weights for greenhouse clomazone study .. .48
16. Analysis of variance for greenhouse depth study. .49
17. Analysis of varia..11ce f.:>r visual estimates of c!oml!.Zcne phytotoxicity. .50
18. Analysis of variance for number of jointed goatgrass seedlings emerging in fallow following fall tillage and herbicide treatments, Promontory, UT. . . 51
19. Analysis of variance for number ofjointed goatgrass tillers in midsummer fallow following treatments oftillages and herbicides, Promontory, UT. .52
20. Analysis of variance for comparison of herbicides in spring fallow, Beaver Dam, UT. .53
21. Analysis of variance for fall counts of jointed goatgrass spikelets in fallow following fall wheat planting, Promontory, UT. . 54
22. Analysis of variance for fall counts ofjointed goatgrass seedlings in fallow following fall wheat planting, Promontory, UT. . 55
23 . Analysis of variance for fall counts of jointed goatgrass spikelets in fallow following fall wheat planting, Beaver Dam, UT. . . 56
24. Analysis of variance for fall counts of wheat seedlings in fallow following fall wheat planting, Beaver Dam, UT. . 57
25. Analysis of variance for percent jointed goatgrass, percent wheat, and total winter wheat yield for harvest, Promontory, UT. . 58 viii
LIST OF FIGURES
Figure Page
I. Percent jointed goatgrass control in midsummer following herbicide and tillage treatments. .30 INTRODUCTION
Jointed goatgrass is one of the worst weeds to invade small grains in the
Intermountain West. Once started, it invades dryland and irrigated small grains, other crops, roadsides, rights-of-way, CRP acreage, and even rangelands. The seed is readily disseminated by wind, water, animals, and mechanically by human activities. It readily adapts to drought conditions that are prominent in dryland, winter wheat production and along dry gravelly roadsides. This allows jointed goatgrass to outcompete winter wheat and facilitates its increase. Jointed goatgrass is a winter annual grassy weed that is closely related to wheat both biologically and genetically and it negatively impacts crop quality and yield.
Recent estimates place the cost ofjointed goatgrass to U.S. farmers at $35 million in direct losses and the combined direct and indirect losses at probably over $145 million.
A 1993 survey in Utah revealed that of the 270 thousand acres of small grains, 52 thousand acres were infested with jointed goatgrass.
Due to the genetic similarities, chemical control ofjointed goat grass appears difficult to improbable because selective herbicides for jointed goatgrass are unlikely in winter wheat. Other control alternatives must be investigated, especially the integration of several control strategies.
The primary objective of this research was to investigate an integrated management strategy for jointed goatgrass control in winter wheat. This integration was a combination of herbicides and tillage applied in the fallow season. Three herbicides were investigated: clomazone, 2,4-D, and glyphosate at different rates. Three tillage regimes 2
were studied: no tillage, conservation tillage, and conventional tillage. Each of these
regimes consisted of different tillage practices. Two field locations were selected and the
experiments were initiated in the fall following crop harvest and continued during the
fallow season and one ensuing crop season. Fall tillage practices with and without
preemergence herbicides were compared with spring tillage practices with and without
postemergence chemicals. Experiments were designed to provide all combinations of
tillage and herbicides including tillage without herbicides and herbicides without tillage.
The specific objectives of the research were to:
1) Compare different tillage practices to reduce or eliminate jointed goatgrass.
2) Evaluate new herbicide efficacy ofjointed goatgrass control.
3) Determine interactions of tillage, herbicides, and cereal management strategies
to control jointed goatgrass.
4) Investigate biological characteristics ofjointed goatgrass that may lend to its
control.
The underlying goal of these studies is to reduce weed competition and contamination of crop seed by reducing or eliminating jointed goatgrass in cereal fields. LITERATURE REVIEW
Jointed goatgrass (Aegilops cylindrica Host.) has become one of the most
devastating weeds to infest winter wheat and other cereal grains in Utah and other winter
wheat-producing states. In 1993, a survey of the wheat-growing regions of the western
United States revealed the number of acres infested by jointed goatgrass exceeded five
million and was reported in 14 western states. The total economic loss to US agriculture
due to jointed goatgrass exceeded $145 million annually. Economic impacts for 1993 in
each state are shown in Table I (38). A survey conducted in Utah in 1993 revealed 52
thousand of the 270 thousand acres planted to small grains were infested with jointed
goatgrass (21 ). A mail survey conducted by Lyon et al. (32) identified jointed goatgrass
as one of the I 0 worst weeds in winter wheat. They also found jointed goatgrass infested
one out of five truckloads of wheat delivered to Nebraska elevators (29).
Jointed goatgrass can be found invading roadways, utility rights-of-way,
wasteland, fallow, and rangeland. It is common in all small grains, especially dryland
winter wheat. It is also a serious problem in Conservation Reserve Program (CRP)
acreages. Jointed goatgrass is well adapted to reduced tillage programs and has become
particularly threatening as conservation tillage programs have been implemented in dryland, winter wheat production (17, 21 ).
Invasion by this weed appears to have started in the Pacific Northwest from grain shipments around the tum of the century. Occurrence nfthP. weed in the Midwest is documented at about 1930 (53). Presently, jointed goatgrass has been found in most of 4 the lower 48 states. Efforts by many cooperators and researchers are underway through an integrated, multidisciplinary effort to reduce the impact ofjointed goatgrass in the U.S.
This integration involves four primary areas offocus: 1) integrated management, 2) population dynamics, 3) bioeconomics and, 4) technology transfer (38).
Jointed goatgrass is generally classified as a facultative winter annual. It does not
Table 1. Results of 1993 jointed goatgrass survey reported by Ogg (38). Acres infested with jointed goatgrass
Light Moderate/dense State infestation infestation Total
California 3,000 0 3,000
Colorado 234,000 233,000 467,000
Idaho 57,000 3,000 60,000
Kansas 288,000 124,000 412,000
Montana 27,000 3,000 30,000
Nebraska 170,400 42,600 213,000
New Mexico 333,000 167,000 500,000
Oklahoma 674,000 340,000 1,014,000
Oregon 70,000 30,000 100,000
South Dakota 3,000 0 3,000
Texas 1,386,000 0 1,386,000
Utah 10,300 41,700 52,000
Washington 439,000 111 ,000 550,000
Wyoming 52,000 26,000 78,000
TOTAL 3,746,700 i,i2i,300 4,868,000 5
require vernalization to flower but longer vernalization periods appear to reduce the time
required to flower (13). It usually germinates in early fall and overwinters as young
seedlings. In most cases, jointed goatgrass germinates on or just below the soil surface
(44). Donald and Zimdahl (18) found that 89% of the jointed goatgrass seed occurred in the upper 3 em of soil. Germination temperatures range from 2 to 40 C, with an optimum
temperature range from 10 to 30 C (53). Seedlings can be identified easily by pulling them
and noticing the characteristic spikelet still attached to the roots.
Vegetative growth and reproduction ofjointed goatgrass is similar to that of winter wheat. They both have spike inflorescences. The inflorescence ofjointed goatgrass is generally much more slender and longer than that of wheat and other grain crops. Unlike wheat, jointed goatgrass spikelets stay intact in the form of a cylindrical joint. Each spikelet contains one to three florets and each floret has a caryopsis or seed
(1 7). In the early spring, jointed goatgrass is bright green in appearance while most winter wheat varieties present a blue green appearance. The leaves of jointed goatgrass have extensive pubescence which aid in early identification and in late summer, jointed goatgrass often turns a reddish color which contrasts it with winter wheat, other cereals, and grasses along hillsides and fence lines. The spike becomes brittle as maturity progresses and the spikelets, often called joints, separate and fall to the ground.
Sometimes, a mild wind causes the inflorescence to shatter. Jointed goatgrass can easily be dispersed naturally by wind, water, rodents, and birds as well as by machinery and vehicles. One enormous problem associated with jointed goatgrass dispersal is the 6
movement of contaminated grain from fields in uncovered trucks. The lighter jointed
goatgrass spikelets move to the top of the load during transport and are blown off into
fields and roadsides (17, 36, 37, 52, 53).
Physiologically, jointed goatgrass and winter wheat are very similar. Jointed
goatgrass appears to be more winter hardy than winter wheat and can survive winters that
ml\y cause widespread winter killing of winter wheat(! 7, 22). Germination, gas
exchange, and growth are very similar for the two species and very little difference can be
found among the different accessions of jointed goat grass obtained from various locations
in the U.S. (14, 17, 23 , 24, 25). It has been found by Dotray and Young (19, 20) that
differences exist between wheat and jointed goatgrass with regards to root and shoot
development but the competitiveness of the two species cannot be explained from their
data.
Several biological characteristics are largely responsible for jointed goatgrass being
considered one of the worst weeds to infest winter wheat. As indicated earlier, jointed
goatgrass and winter wheat are biologically similar in genetics, physiology, and growth
habits and the two species can cross to form a hybrid. They compete for the same
environmental elements and habitat. Jointed goatgrass seed can remain dormant in soil for
long time periods. Jointed goatgrass is a host for pests and pathogens that affect winter
wheat. Jointed goatgrass dockage is a problem in harvested grain and since it is approximately the same height as winter wheat, selective harvesting is not practical.
Together, these factors make jointed goatgrass one of the most serious weeds in winter 7 wheat.
Jointed goatgrass and winter wheat are genetically related since they each possess the D genome. This close relationship makes selective control by herbicides most difficult, if not impossible. Jointed goatgrass is also a source for genetic variability in developing winter wheat cultivars (17). The cytoplasmic relationship and genetics are well discussed by Maan (33) artd further explained by Zemetra (57). Jointed goatgrass is an allotetraploid with 28 chromosomes containing a C and D genome. Wheat is an allohexaploid with 42 chromosomes containing A and B genomes, and also the D genome.
One of the most promising control strategies for jointed goatgrass would be an herbicide-resistant winter wheat cultivar. The risk is that jointed goatgrass and winter wheat cross naturally (17) and although the hybrid is usually sterile, Zemetra (57) found viable seeds sometimes occur. Further research is necessary to determine whether the herbicide resistance gene in wheat could be prevented from moving to jointed goatgrass.
Jointed goatgrass and winter wheat compete for the same environmental needs, i.e., sunlight, water, and nutrients. Anderson (4) demonstrated that jointed goatgrass and winter wheat share the same ecological niche and that winter wheat yields were not reduced ifjointed goatgrass is removed by early March. Control measures, therefore, must be conducted prior to wheat emergence in the spring. As few as 18 plants m·2 reduce wheat yields up to 30% (3, 4, 5) compared to uninfested wheat under similar conditions. Jointed goatgrass spikelets can remain viable in the soil for up to 5 years (5,
14, 17, 18, 28) but 99% of the original viable seed germinated in the first 2 years. 8
Viability of laboratory-stored seed remained above 95% for 2 years (14, 16, 28).
Jointed goatgrass is also a serious challenge in harvesting winter wheat crops.
Jointed goatgrass is approximately the same size as winter wheat, which usually prevents
selective harvesting (17). The jointed goatgrass spikelets are approximately the same size
as the winter wheat kernels and seed cleaners are incapable of separating them from
wheat. They appear a~ chaff in barveste recognize the problem. At grain elevators, however, jointed goatgrass spikelets are discounted as dockage. The grain grade is decreased and farmers receive lower returns for their grain. When foreign matter is between 0. 5 and I. 0%, grain grade is reduced to No. 2 and a $0.57 m·3 grain volume (2 cents/bushel) penalty is assessed. As foreign matter increases, grade is reduced further and the penalty increases. Grain with more than 5% foreign matter is considered sample grade, and if accepted by dealers, is assessed a $4.26 m·3 grain volume (15 cents/bushel) penalty (7, 17). Jointed goatgrass is an overwintering host for pests that attack winter wheat. These pests include the Russian wheat aphid (Diuraphis noxia Mordvilko RKO) (27) and the following fungal diseases: Ascochyta sp. (leaf spot), Fusarium acuminatum Ell. Ev. sensu Gordon (pink mold), Pseudocercospore/la herpotrichoides (Fron) Deighton (foot rot), Puccinia graminis Pers. f sp. tritici Eriks. and Henn., P. recondita Rob. ex Desm. f sp . tritici, P. striiformis West, Pythium arrhenomanes Drechs. (root browning), P. debaryanum Hesse (damping off), Tilletia controversa Kuhn (dwarf bunt), Uromyces graminico/a Burr, and Tilletia indica Mitra (kernel bunt). There are no reports ofjointed 9 goatgrass hosting nematodes or other plant parasites. The wheat curl mite (A ceria tulipae ), which acts as a vector for the wheat streak mosaic virus, is also found on jointed goatgrass (17). Control alternatives for jointed goatgrass in winter wheat are currently very limited. Selective herbicides do not exist to remove jointed goatgrass from winter wheat crops. Integratio11 of available c.ontrol options appears to be the most prorPjsing to remove jointed goatgrass. Available control approaches include biocontrol, some chemical control, cultural practices including tillage, competition, but most importantly, prevention. The best way to keep jointed goatgrass from becoming a field problem is to keep it from establishing in the first place. The approach that the Forest Service uses to control wildfires is prevention of a problem before it starts. 1 Prevention of weed problems should always be the first tactic that producers employ. Planting fields with jointed goatgrass free seed and using clean machinery are prerequisites to effective jointed goatgrass avoidance. Always enter and leave fields at the same location to keep infestations isolated and manageable. Waste areas surrounding fields must be kept free of goatgrass with herbicides, tillage, or other strategies. Crop rotation to spring varieties, where possible, also helps to lower goatgrass seed production (17, 36, 37, 49). Where possible, use spring varieties of wheat or even other spring crops such as corn, millet, barley, sunflower, or safilower (17, 29, 36, 37, 49). Crop rotations benefit farmers in other ways too, 'Steven A. Dewey, personal conversation. 10 holding insect populations and soil diseases to tolerable levels and helping to maintain soil fertility (47). Studies by Anderson (5) and Westra (51) indicated that the best rotational crop for winter wheat is proso millet to lower jointed goatgrass seed banks. In areas where winter wheat is the only practical crop, the rotation of choice is fallow. Anderson (2, 6) indicated that incorporated crop resi(iues can eliminate jointed goatgrass seerlling growth hy 70 to RS % HowP.ver, residues did not decrease seedling emergence of winter wheat or jointed goatgrass. Crop residues interact with herbicides and thereby affect their effectiveness. Producers may find winter wheat showing a higher degree of competitiveness when using incorporated crop residues and banding N with winter wheat at planting (2, 5). Wheat contaminated with jointed goatgrass is docked at the grain elevators and reduced to sample grade and is often fed to cattle. Lyon et a!. (30) discovered that 75% of the seed that had passed through the rumen of cattle was still viable. This suggested that cattle may actually act as a mechanism for jointed goatgrass dispersal (29). A suggestion that jointed goatgrass spikelets be ground before feeding led to a second study by Lyon and Rush (31) where it was discovered that jointed goatgrass that had passed through a fine-grind hanuner mill and then fed to cattle did not germinate. Therefore, if grain is docked and reduced to sample grade, it is better to fine-grind it and feed it to cattle than suffer a dockage discount and attempt to clean it at elevators. In 1994, R. A. Caskey of the USDNARS National Forage Seed and Cereal Research Center designed a seed separator that cleaned jointed goatgrass spikelets from II winter wheat seed. Results are not given to establish effectiveness but he claimed, "there's no other technique as economical for getting jointed goatgrass seeds out of wheat" (54:22). Biological control research of jointed goat grass appears to have some possible bacterial strains that will suppress germination and/or growth ofjointed goatgrass. Over 2000 occurring strains of the Pseudomonas bacteria are being tested (8). Sorne resear.;h is also being conducted to investigate synergism of herbicides with biological controls (48). Some of these do show control of jointed goatgrass in winter wheat but the results are inconsistent. The prospects for biocontrol of jointed goatgrass in winter wheat are still many years in the future. Postharvest field burning of wheat stubble can be a control that farmers may consider for jointed goatgrass. Willis (52) and Willis eta!. (53) discovered that a one second exposure of jointed goatgrass spikelets to a flame reduced germination from 97.5% to 27.5% and oven temperatures of 150" C also can help to reduce germinability. Field burning, especially that with over 5 T ha·' surface stubble (52), is an effective method for control of small infestations ofjointed goatgrass following a winter wheat harvest (56). Tillage, especially the use of a rod weeder, throughout the fallow season provides very good jointed goatgrass control ( 44). Seed survival is also greatly reduced by tillage (14, 15). A combination of tillage and various herbicides in an integrated approach can often be the approach that farmers use to control jointed goatgrass in large fields. Cartee I2 et aL (II) recorded between 43 and 94% jointed goatgrass control using an integrated approach. No tillage, particularly in a fallow rotation, does not provide a deterrent to jointed goatgrass and the highest number ofjointed goatgrass plants was noted in no-till plots (4I, 42, 43, 44). Jointed goatgrass occurs more frequently on farms using conservation tillage than on farms using conventional tillage practices (I 7, 39). Jointed goatgrass seems to be particularly adapted to no-tiU situations because of its !!bility to germinate and grow at the soil surface with little moisture (15). Combinations of tillage and other cultural practices provide the greatest control of jointed goat grass without the use of herbicides. As conservation practices have been instituted, jointed goatgrass has adapted and is one of the worst weeds in winter wheat (I7, 39). Currently, no registered herbicides exist for selective control of jointed goatgrass in winter wheat. Herbicides that have been investigated include 2,4-D and glyphosate combinations for fallow control (II, 4I, 42, 43), ethiozin (2), ethyl metribuzin (9, IO, 26, 46, 50, 55), SMY-1500 (34), and clomazone (35, 4I , 42, 43). 2,4-D and glyphosate provided jointed goatgrass control throughout the fallow season but did not affect seeds that remained in the soil and subsequently appeared in the crop (41 ). Other herbicides provided partial control of jointed goatgrass in fallow rotation but were not adequate to eliminate jointed goatgrass in the crop. These herbicides need to be integrated with other control measures to provide satisfactory control. Miller and Neider (35) showed that clomazone has some promise as a control for jointed goatgrass with 90% controL Clomazone is a registered herbicide in soybeans and 13 fallow for many states and Canada(!). Clomazone symptoms include chlorosis and whitening of leaves (1, 12, 40, 45). It does have some carryover from year to year and this has a dramatic effect on its use. Clomazone is also highly volatile and is easily moved off site if not properly incorporated ( 40). Jointed goatgrass is a major weed of economic importance. Control of this weed ca11 only come by integrated ma.11agement techniques, especially prevev.tion. Jointed goatgrass not only drastically reduces yield but its presence can reduce grain quality because of dockage. 14 MATERIALS AND METIIODS Experiments were conducted in the greenhouse and fields of northern Utah and the experimental methods and presentation of results will be separated accordingly. Greenhouse Studies The first greenhouse study was designed to investigate the movement of clomazone through the soil profile and its subsequent effect on jointed goatgrass. Another greenhouse study was designed to investigate the role of planting depth on jointed goatgrass germination and seedling emergence. The growth media for both greenhouse experiments was a mixture of silt loam soil, peat moss, and perlite at 2: I : I, respectively. The soil mix had a pH of 6.6 and 7.5% organic matter. Soil was mixed and measured to fill a sufficient number of 20-cm black plastic pots for both experiments. The first study was designed to determine the activity of clomazone on jointed goatgrass plants in the greenhouse to help establish dosage levels for field trials, and to determine clomazone movement through the soil profile. Two irrigation methods were investigated: subirrigation and surface watering. The study had three replications. Soil for the clomazone study was divided into four groups, one group for each herbicide treatment. All pots were filled to 15 em level with soil except the control pots with no herbicide and they were filled to the 20 em level. The remaining three soil groups were placed in three bags and clomazone was added to the bagged soil corresponding to 15 three clomazone rates: 0.11 kg ai ha·', 0.22 kg ai ha·', and 0.33 kg ai ha·'- Each soil bag was mixed thoroughly to simulate herbicide incorporation. The soil was removed from bags to fill appropriate pots to 20 em; therefore, herbicide incorporation was 5 em deep in the pots. All pots were initially surface watered with 200 ml water. Following watering, the pots were planted with I 0 seeds each. There were 48 pots total, 24 with wheat and 24 with jointed goatgrass. Two irrigation methods were used: subirrigation and surface irrigation. The sub irrigated pots were placed in square pans (three pots per pan) and the pans were filled with 600 ml (200 ml per pot) of water each morning. The water percolated up through the soil to provide adequate moisture for germinating seedlings. The surface-irrigated pots were watered on the surface with 200 ml each day as needed, supplying adequate moisture for the germinating seedlings. Pots were fertilized once a week with 250 m1 of a 1 solution containing 230 mg N, 190 mg P20,, and 170 mg K20 L" Plants were harvested after 8 weeks by clipping plants at the soil surface and measuring fresh weight. The clippings for each pot were bagged, labeled, and placed in a dryer and dry weights were recorded after a 48-hour drying period. A second greenhouse study was designed to investigate the role of planting depth on emergence ofjointed goatgrass. The study was established as a completely randomized design with four replications. Wheat and jointed goatgrass were planted at various depths. The depths ranged from 1.27 to 11.43 em at 1.27-cm increments giving nine depths. Twenty-em black pots were filled with soil as described above. No herbicide treatments 16 were used in this experiment. Pots were initially watered with 200 ml water and subsequently planted with 10 seeds at one soil depth in each pot. Each pot contained 10 seeds of either wheat or jointed goatgrass to avoid any germination interaction between the two species. The pots were watered each day with 200 ml water per pot and fertilized once per week with 250 ml of a solution containing 230 mg N, 190 mg P,O,, and 170 mg K,O L-'- Pots were observed for emergence ofjointed goatgrass and wheat seedlings md recorded weekly regarding the number of seedlings per pot. The study was terminated after 3 weeks when it appeared that no additional seedlings would emerge. Fallow Season Evaluations Two fields were used to conduct the field studies. The first field study was initiated in the fall of 1992 following wheat harvest and prior to a fallow season in 1993 at Promontory, Utah. The second field study was also initiated following wheat harvest in 1993 and prior to the 1994 fallow season at Beaver Dam, Utah. The Promontory experiment was established on a dry farm 12 km northeast of Promontory, Utah on Richard Peterson's farm. The farm primarily produces winter wheat because spring varieties do not establish well. The experimental field had been on a winter wheat-fallow rotation for over I 0 years. The Beaver Dam experiment was established on a dry farm 4 km west ofPetersboro, Utah on the Leo Erickson farm. This farm primarily produces winter wheat but safilower, barley, and alfalfa have been grown at this site in the past. It had been on a winter wheat-fallow rotation for the p~st 4 years. The initial treatments in Promontory and Beaver Dam consisted offal! tillages and 17 a preemergence herbicide, clomazone. These experiments were conducted in commercial fields that had even distributions of weeds across the field . The fallow treatments were selected to eliminate jointed goatgrass seedlings in the fallow and concomitantly from infesting the succeeding crop. Harvests were taken at Promontory on August 25, 1994 and at Beaver Dam at the end of the 1995 crop season. The annual precipit~tion average rer.ordt>.d at the ne;u-est weather st ~.tion at Thiokol Plant 78, approximately 10 km east of Promontory, Utah, was 35.92 em. The total precipitation for this site for the 1993 fallow season was above average at 40.44 em; however, the total precipitation for the 1994 crop season was below average at 30.22 em. The annual precipitation average for the Beaver Dam, Utah site is 45 .03 em. The total precipitation for 1994 fallow season at Beaver Dam was below the average at 3 5.15 em. Soils in the Promontory experiment were a fine-loamy over sandy-skeletal, mixed, mesic Calcic, Argixeroll. Soils at Beaver Dam were a fine-silty, mixed, mesic Calcic, Pachic, Argixeroll. Both experimental fields were arranged as randomized block designs with four replications. The main plots were tillages applied in strips and subplots, herbicides, were also applied in strips across main plots. Six tillage treatments and six herbicide treatments were used. Three tillage regimes were investigated: no tillage, conservation tillage, and conventional tillage. The no-tillage regime consisted of a no-till practice and served as a control for the tillage treatments. The conservation tillage regime consisted of two tillage 18 practices: fall chiseling with a spring seedbed preparation using a Calkins skewtreader in a single pass in the spring, and fall subsoiling with the single skewtreader pass in the spring. The conventional tillage regime consisted of three tillage practices: fall chiseling with three summer rodweeder treatments at 3-week intervals, fall subsoiling with three summer rodweeder treatments at 3-week intervals, or spring chiseling with three summer rodweeder treatments at 3-week intervals. The rodweeding was accomplished using a single pass at each interval. Three herbicides were investigated and a control without herbicide. The three herbicides included 2,4-D, glyphosate, and clomazone. The 2,4-D and glyphosate were premixed and applied together so these two herbicides were evaluated as one compound. The 2,4-D plus glyphosate combination was applied postemergence in the spring and clomazone was applied preemergence in the fall . Two dosage levels of clomazone were applied: 0.42 kg ai ha- 1 and 0.56 kg ai ha·'- Three rates of2,4-D plus glyphosate combination were applied: 0.53 kg ae ha-1 2,4-D with 0.42 kg ai ha- 1 glyphosate, 0.98 kg ae ha- 1 2,4-D with 0.79 kg ai ha-1 glyphosate, and a split application of0.26 kg ae ha-1 2,4- D with 0.21 kg ai ha-1 glyphosate at each application for a total of0.53 kg ae ha- 1 2,4-D with 0.42 kg ai ha-1 glyphosate. Treatments at Promontory were initiated with the application of fall tillages 4 weeks after the 1992 harvest. Plot size was 67 m2 and large enough to allow the farmer to till with common farm tillage equipment at normal speeds. Fall tillages included fall chiseling and fall subsoiling (also called ripping). After the tillage operations, the herbicide 19 clomazone was applied using a boom sprayer mounted on an ATV. Spring applications of tillage and herbicides were applied April20 at Promontory. Spring tillage included a spring chisel application and the operation of a skewtreader for the conservation tillage regime. Spring applications of herbicides included the postemergence treatments of the 2,4-D plus glyphosate combination. Counts were made 2 weeks after the spring treatments for the number ofjointed 2 goatgrass plants per square meter (m- ) for each treatment using a I 0 em by 10 em grid. Three counts were taken from each plot. At the time of this counting, the summer rodweedings bad not been applied. Four counts were made in each plot. Counts were not taken for the clomazone-treated plots but a visual estimate of the jointed goat grass injury from clomazone was employed using a scale of0-10 with 10 being complete death of the jointed goatgrass plants. The first rod weeding was made in early June 1993 . The objective of the rod weeding was to roll a rod just below the soil surface and uproot germinating seedlings to kill them. This implement was pulled behind a tractor and commonly used for weed control in the Intermountain West during fallow where it serves an integral role in conventional tillage regimes. Surface residues and tillage treatments varied for each tillage regime used in these experiments. Table 2 represents the tillage regimes and information with regards to each tillage regime. The second application of the split treatment of 2,4-D plus glyphosate was made 2 weeks after the initial rodweeding. Three rodweeder treatments were made, one every 3 to 4 weeks throughout the summer. 20 Table 2. A comparison of tillage regimes regarding number of fallow operations and plant surface residue. Surface residue Tillage regime Number of 1 fallow operations -----%------kg ha------ No tillage 0 undisturbed 3928 Conservation tillage >30 2020 Conventional tillage 3 <15 561 Another set of counts were taken in early July 2 weeks after the second application of the split herbicide and before the second rod weeding. Four counts were taken in each plot using the same grid as before. Experiments at Beaver Darn, Utah were initiated with the application of fall tillage 3 weeks after grain harvest in 1993 . The plot size at this location was 13 m2 These were smaller plots than at Promontory because the landowner did not perform the tillage operations. Implements from the USU Experiment Station were used for tilling this site. A chisel, subsoiler, and rodweeder similar, but smaller, to those used at Promontory were used at Beaver Darn. The implement used for the conservation tillage spring application was a cultipacker applied once. A skewtreader was not available that matched the plot size. Plots were treated similarly to those in Promontory. Fall tillage and herbicide applications were identical, spring applications were similar, and the plots received t re~tf'l e ttt s by a rodv-.reeder three se?a:-a!e tir:le !j during the fcllov; s~z o n ~t 3 --,,., c ~ k intervals. 21 Herbicides were applied using a bicycle sprayer because the booms of the four wheeler were too wide and for simplicity of application. Spring counts were taken using a round quadrant. Four counts were taken in each plot. Counts, however, were only taken for the no-till practice because the plots had been tilled the day of counting and no plants remained that could be counted. Within Crop Evaluations A winter wheat crop was planted September 20 at Promontory, Utah approximately I week before the soil samples were taken to determine the number of jointed goatgrass spikelets and young seedlings in each of three profile depths. This site was planted with the Promontory variety of winter wheat at 75 kg ha·'- Wheat was planted with a heavy deep furrow drill capable of planting into the no-till plots. Numbers ofjointed goatgrass seedlings and spikelets were determined in the fall to help understand the influence ofjointed goatgrass on the wheat crop and as an indication of their winter survival. A sampler was designed to extract soil samples to I 0 em deep and easily separate the depths needed. Sample depths of 0 to I em, I to 5 em, and 5 to I 0 em were examined for the numbers ofjointed goatgrass spikelets and seedlings. Soil samples were taken to the lab and each sample was counted individually by hand. Samples were filtered and spikelets and seedlings extracted from the soil and counted. Winter wheat was planted at Beaver Dam in late October. The Promontory variety was userl and planted at the same rate as at Promontory Winter whe from the soil samples. Fall counts of the numbers ofjointed goatgrass spikelets and seedlings were made for each of the three depths at Beaver Dam using the same procedure used for the Promontory site. The samples, however, were extracted later in the fall and after a recent snowstorm so soils were extremely wet and difficult to separate using soil separators. Therefore, samples were washed usi.FJg a soil elutriator at the USDA Crop Research facility in Logan. An elutriator is designed to wash the soil and force any seeds, spikelets, and seedlings from the soil and force them over cones, facilitating separation and counting. Counts were made of all spikelets and seedlings in each soil subsample. Harvests were taken at Promontory using a 2-m Massey Ferguson plot combine on August 25, 1994. The combine was specially designed to cut plots, weigh the total area cut, and give an electronic total harvest yield readout in the field. A representative sample from each plot was obtained for analysis. Samples were placed in paper bags and each plot was labeled and subsequently taken to a lab for further analysis. The bags were emptied onto separators and shaken to separate wheat from jointed goatgrass and each was gathered and weighed. Wheat yields were obtained by computing total yield from harvester computer totals and subtracting weights ofjointed goatgrass and inert material. 23 RESULTS AND DISCUSSION Greenhouse Studies The first greenhouse study was designed to measure clomazone phytotoxicity to wheat and jointed goatgrass grown under controlled conditions and irrigated either by surface watering or subsurface irrigation. Wheat and jointed goatgrass biomass means are depicted in Table 3 for dry weights. Mean dry weights (Table 3) for the I 0 wheat plants under subsurface irrigation and no herbicide were 2.9 g per plant. Jointed goatgrass mean dry weights for the same treatment were 1.8 g per plant. With a 0.11 kg ha·' treatment of clomazone the wheat dry weight dropped to 1.6 g per plant, a 45% decrease, and the jointed goatgrass dry weight dropped to 0.8 g per plant, a 55% decrease. The wheat and jointed goatgrass responded Table 3. Dry weights of wheat or jointed goatgrass plants following clomazone treatments under subsurface and surface irrigation. Clomazone Subsurface irrigation Surface irrigation 1 (kg ha- ) Wheat AEGCY' Wheat AEGCY ------g/plant------ 0.00 2.9 1.8 2.3 1.5 0.11 1.6 0.8 0.8 0.5 0.22 0.7 0.5 0.5 0.2 0.33 0.5 0.2 0.5 0.1 LSD @ 0.05 ------0.8 5------1 4-letter approved WSSA code for jointecl goHtgrass frorn C:ompo~it e List of Weeds, Revised 1989. Available from WSSA, 1508 West University Ave., Champaign, IL 61821- 3133 . 24 similarly to surface irrigation and treatment with 0.11 kg ha- 1 clomazone, resulting in a 65% decrease in dry weights in each species. Dry weights were reduced for wheat and jointed goatgrass under subsurface irrigation from approximately 50% with the lowest clomazone dosage to approximately 85% with 0.33 kg ha-1 clomazone. However, dry weights were reduced for the two species under surface irrigation from 65% to approximately 85% with inc.reasing clo~ages of cloma.znne. This experiment did not demonstrate jointed goatgrass to be more sensitive to clomazone treatments than winter wheat at the three herbicide dosages tested. This demonstrated that these two species respond in an essentially identical way to this herbicide since similar responses were recorded for the two species grown under surface or subsurface irrigation. Subsurface irrigation probably approximates dryland farming conditions and therefore casts little hope for clomazone as a selective jointed goatgrass herbicide under the predominate conditions where this species is becoming a serious weed. The values in each column for Table 3 are shown to be different at each level. However, the two species did not express differential sensitivity to clomazone at the rates tested and therefore a field trial would be necessary to further determine the overall effects of clomazone on either species. This greenhouse study demonstrated that clomazone has similar effects on both species at each treatment level and under similar environmental conditions. The planting depth study conducted in the greenhouse revealed that seed placement in the soil plays an important role in jointed goatgrass emergence. Average 25 seedling emergence for the two species is presented in Table 4. Jointed goatgrass emergence was reduced at planting depths greater than 2. 5 em, whereas wheat seedling emergence was not lowered until the seed was planted 5.0 em deep or deeper. Table 4. Percentage wheat and jointed goatgrass seedlings emerging at nine planting depths in the greenhouse. Seedlings emerged Planting depth Wheat ------em------%------1.3 93 93 2.5 90 85 3.8 90 75 5.1 65 45 6.4 18 7.6 8 0 8.9 3 0 10.2 0 0 11.4 0 0 LSD@ 0.05 ------5%------1 4-letter approved WSSA code for jointed goatgrass from Composite List of Weeds, Revised 1989. Available from WSSA, 1508 West University Ave., Champaign, ll.. 61821- 3133. Based on these results, jointed goatgrass did not germinate below 6.4 em and there is significantly more wheat than jointed goatgrass germinating below 2.5 em. A study to test these results in a field situ:~tia!! wa~ !!at conducted. Westra eta! (51) also stadie:l jointed goatgrass emergence in a greenhouse study but they found that 60% of the jointed 26 goatgrass seedlings emerged when the seed was planted 8 em deep. Farmers who attempt to plant jointed goatgrass-contaminated wheat at depths below 5 em may be able to obtain winter wheat without jointed goat grass emergence for a season but jointed goatgrass can survive in the soil for up to 5 years (17). However, Donald (I 5) found jointed goatgrass seed to be short -lived in frequently disturbed soils. Fallow Season Evaluations The number ofjointed goatgrass seedlings that emerged in each of the plots at the beginning of the fallow season was recorded in May 1993 in Promontory, Utah and in April 1994 in Beaver Dam, Utah and analyzed as randomized block designs with split plots. The tillage main effects were applied in strips and the secondary effects (herbicides) were applied in strips perpendicular across tillages. The number ofjointed goat grass seedlings was not determined in plots treated with clomazone because they were small and very chlorotic. Visual estimates were taken of the chlorosis exhibited by jointed goatgrass in response to clomazone and are given in Table 5. The visual injury estimates demonstrated a difference between 0.42 kg ai ha·1 and 0.56 kg ai ha· 1 clomazone treatments following either fall subsoil or fall chisel. Differences were also noted for tillage between plots that were treated with clomazone and those not treated. Clomazone at 0.42 kg ai ha·1 was equally damaging to jointed goatgrass at the 0.56 kg ai ha·1 dosage in the absence of tillage. When the visual injury ratings were made, it appeared that clomazone would control jointed goatgras~ becau~e the pl~nts looke-d extensively damaged and that clomazone may be useful as a chemical fallow herbicide. 27 Table 5. Visual estimates of clomazone phytotoxicity to jointed goatgrass, Promontory, UT. (Aprill993) Clomazone Tillage kg ai ha" 1 No-till Fall subsoil Fall chisel 1 ------Injury index ------ 0 0.0 0.0 0.0 0.42 7.5 7.5 73 0.56 7.8 8.0 8.0 LSD@ 0.05 ------0 .4 2------1 Injury index based on a 0-10 scale with O=no injury and 1O=dead plant. In subsequent evaluations, however, it was shown that plants recovered and clomazone treatments were nearly insignificant at the end of the fallow season and just prior to winter wheat planting. The number ofjointed goatgrass plants m·2 at Promontory ranged from near 300 plants in plots that had been fall tilled, either by subsoiling or chiseling, to near 3000 plants in plots not fall tilled (Table 6). It appears reasonable that jointed goatgrass growth before spring tillage cost the farmer in lost moisture and nutrients although these comparisons were not a part of this study. Fall subsoiling was as effective as fall chiseling in reducing jointed goatgrass seedling populations to approximately 13% of the untilled populations. It was apparent that with exceedingly large numbers ofjointed goatgrass seedlings as experienced in this field, 87% control left an unacceptable number (approximately 340 2 plants m" ) of the weeds in the field to deplete soil moisture and to replenish the jointed goatgrass seedbank in the soil, and reduce yield in the ensuing crop. Recent studies reveal 28 Table 6. Number of jointed goatgrass seedlings emerging in fallow following fall tillage and herbicide treatments, Promontory, UT. (April1993) 2,4-D + glyphosate 0.53 kg ae ha·' 0.98 kg ae ha·' Tillage No herbicide + 0.42 kg ai ha·' + 0.79 kg ai ha·' 2 ------No . m------ No-till 2685 2570 2701 Fall subsoil 322 351 325 Fall chisel 351 342 380 LSD @0.05 ------982------ that jointed goatgrass populations of 200 seed-producing tillers m·2 or greater cause more than 25% wheat yield loss. 2 Anderson ( 4) found that as few as 18 plants m·2 reduced wheat yield up to 30%. Obviously, some form of spring and/or summer tillage was needed to stop jointed goatgrass competition and seed production. The number of jointed goatgrass tillers remaining after treatments of2,4-D plus glyphosate and spring and summer tillage is displayed in Table 7. In the absence of any chemical treatment, jointed goatgrass numbers ranged from about I 0 to nearly 1000 plants m·2 following spring and summer tillages, very similar to the proportions observed after fall tillages. Plots not mechanically tilled had almost 1000 jointed goatgrass plants m·2 while those subjected to either skewtreading or rodweeding had approximately I 0 to 100 plants m·2 Jointed goatgrass control in midsummer following herbicide treatments and the ~vans, J.O., R.W. Mace. Unpublished Results. Regional Jointed Goatgrass Initiative. 29 Table 7. Number of jointed goatgrass tillers in midsummer fallow following treatments of 2,4-D +glYJ?hosate and spring and summer tillages, Promontory, UT. (July 1993) 2,4-D + glyphosate 0.53 kg ai ha-1 0.98 kg ai ha·' Tillage No herbicide + 0.42 kg ae ha-1 + 0.79 kg ae ha- 1 2 ------No. tillers m· ------ No-till 985 6 0 Fall subsoil + Spring skewtread 50 2 Fall subsoil + Summer rodweed 13 2 4 Spring chisel + Summer rodweed 7 0 Fall chisel + Spring skewtread 89 6 Fall chisel + Summer rodweed 12 0 0 LSD @0.05 ------1 52------ first rod weeding are shown in Table 7 and Figure I. Percent control (Figure I) was determined from the average number ofjointed goatgrass plants in each treatment revealed in Table 7 as a percentage of those appearing in no-till plots with no herbicide. When 2,4-D plus glyphosate treatments were integrated with spring and summer tillage, the number ofjointed goatgrass plants ranged from 0 to 6 seed producing tillers m·2 The 2,4-D plus glyphosate treatments in the absence offall and spring tillage were as effective in controlling jointed goatgrass as when integrated with tillage. Meaningful differences were not observed among the various tillage operations when integrated with either of the miJ A = no herbicide miJ B = clomazone (0.42 kg ailha) - C = clomazone (0.56 kg ailha) ~ 100 Clill 0 = 2,4-0 + glyphosate (0.53 kg ae/ha + 0.42 kg ailha) e 100 80 c iml'J E = 2,4-0 + glyphosate 0 t) 80 60 (0.98 kg ael ha + 0. 79 kg ai/ha) (f) (f) ~ 60 roOl 0 Ol "0 ClJ c fall chisel + summer rodweed '6 ...., fall chisel + spring skewtread spring chisel + summer rodweed fall subsoil + summer rodweed 1-ter6 · fall subsoil + spring skewtread ~Cir~ "f3s no-till Fi gure 1. Percent jointed goatgrass control in midsummer following herbicide and tillage treatments. w 0 31 two 2,4-D plus glyphosate treatments. When no herbicide was applied, the best controls were treatments of fall tillage coupled with summer rodweeding, resulting in 99% jointed goatgrass control by midsummer (Figure 1). However, when 2,4-D plus glyphosate treatments are integrated with tillage, 99 to I 00% control was achieved with the tillages investigated. Perfect jointed goatgrass control was acco111plished by midsu111mer with either of the 2,4-D plus glyphosate treatments when integrated with fall and summer tillage. The number of jointed goatgrass seed producing tillers remaining after treatments of clomazone and spring and summer tillage is displayed in Table 8. The number ranged Table 8. Number of jointed goatgrass tillers in midsummer fallow following treatments of clomazone and spring and summer tillages, Promontory, UT. (July 1993) Clomazone Tillage No herbicide 0.42 kg ai ha·' 0.56 kg ai ha·' 2 ------No. tillers m------ No-till 985 798 585 Fall subsoil + Spring skewtread 50 31 20 Fall subsoil + Summer rodweed 13 9 10 Spring chisel + Summer rodweed 7 II Fall chisel + Spring skewtread 89 81 39 Fall chisel + Suiumei rudweed 12 9 7 LSD @0.05 ------15 2 ------32 from less than I 0 plants m-2 when 0.42 kg ha·• clomazone was combined with fall and summer tillage to nearly 800 if no tillage occurred. The 0.56 kg ha-• clomazone treatment allowed jointed goatgrass tiller populations ranging from 5 tillers m·2 when combined with fall and summer tillage to about 600 if no tillage was performed. Percent jointed goat grass control is also depicted in Figure I for the interaction of clomazone treatments •.nd tillag~ . Under no-till, 0.42 kg ha·• clomazone was measurably better (19%) than I!O herbicide and the 0.56 kg ha-' clomazone rate (41% control) was better than the lower dosage. Clomazone did not provide satisfactory jointed goatgrass control in the absence of tillage. When clomazone was integrated with fall and summer tillages, 99% jointed goatgrass control was achieved by midsummer. For each of the herbicides investigated, the summer rodweedings provided the best control and were perhaps the most effective treatment used in these experiments. Jointed goatgrass densities in Beaver Dam were recorded in June 1994 (Table 9) only from the no-till plots because an errant spring tillage had buried or knocked down jointed goatgrass seedlings, making it difficult to make accurate density counts. The jointed goatgrass densities in the no-till revealed that fall-applied clomazone was essentially ineffective in stopping jointed goatgrass emergence. Foliar herbicides applied in the spring reduced jointed goatgrass densities about 50% but allowed far too many weeds to be considered a practical approach. What appeared to be the best herbicide in 1 1 the no-till was 2,4-D (0.98 kg ae ha- ) plus glyphosate (0.79 kg ai ha- ), which left 318 2 plants m· ; a jointed goatgrass density of this magnitude is too detrimental for winter 33 Table 9. Influence of selected herbicides on jointed goatgrass emergence in the absence of tillage, Beaver Dam, UT. (July 1994) Herbicide AEGCY' 2 ------plants m· ------clomazone (0.42 kg ai ha"') 661 1 clomazone (0.56 kg ai ha" ) 628 1 1 2,4-D (0.53 kg ae ha" ) + glyphosate (0.42 kg ai ha" ) 401 1 2,4-D (0.26 kg ae ha ') + glyphosate (0.21 kg ai ha" ) 378 1 1 2,4-D (0.98 kg ae ha" ) + glyphosate (0.79 kg ai ha" ) 318 Control (no herbicide) 790 LSD@ 0.05 ------138------'4-letter approved WSSA code for jointed goatgrass from Composite List of Weeds, Revised 1989. Available from WSSA, 1508 West University Ave., Champaign, IL 61821- 3133 . wheat production. The highest clomazone dosage was measurably better than no herbicide and the three 2, 4-D plus glyphosate treatments appeared better than clomazone. None of the herbicide treatments tested showed much promise for control of jointed goatgrass in a no-till program. Within Crop Evaluations Following the fallow season at each site, a winter wheat crop was planted. Winter wheat was allowed 2 weeks to germinate before jointed goatgrass densities were determined in the wheat crop. Jointed goatgrass spikelets and seedlings were counted in soil samples to determine population densities. Herbicides did not provide any meaningful differences regarding jointed goatgrass densities in the crop and will therefore not be 34 discussed further. Jointed goatgrass densities at Promontory (Table I 0) in the winter wheat crop ranged from zero spikelets m·2 in the conventional tillage, namely those with three summer rodweedings, to about 1800 in the no-till at the 0-1 em soil depth. Significant differences were found between the conventional tillage and the conservation tillage (those with the spring skewtrei\ding application). Both sk~wtreader treatments had approximately 600 2 spikelets m· , whereas all rodweeder treatments provided 100% control of spikelets at the soil surface (0-1 em). Table 10. Numbers ofjointed goatgrass spikelets at three soil depths in seedling winter wheat, Promontory, UT. (October 1993) Depths Tillage 0- I em 1-5 em 5- 10 em 2 ------No . m · ------ No-till 1883 747 65 Fall subsoil + Spring skewtread 616 292 0 Fall subsoil + Summer rodweed 0 33 0 Spring chisel + Summer rodweed 0 0 0 Fall chisel +Spring skewtread 616 228 0 Fall chisel + Summer rod weed 0 33 0 LSD@ 0 05 ------461------35 In the 1 to 5 em depths at Promontory, the no-till plots had significantly greater numbers ofjointed goatgrass spikelets than any of the other tillages. There were no meaningful differences among any ofthe tillage treatments even though skewtreading had about 10 times more jointed goatgrass spikelets than those that received three rodweedings. The 5 to 10 em depth produced zero spikelets m·2 for all ofthe tillages investigate Seedling counts for the 0 to 1 em depth at Promontory (Table II) ranged from zero seedlings m·2 in the three conventionally tilled treatments (three summer rodweedings) to over 2000 in no-till. Conservation tillage (skewtreader treatments) Table 11. Numbers of jointed goatgrass seedlings for three soil depths, Promontory, UT. (October 1993) Depths Tillage 0-1 em I- 5 em 5-10 em 2 ------No . m" ------No-till 2176 2338 98 Fall subsoil + Spring skewtread 1343 1343 171 Fall subsoil + Summer rodweed 0 1201 65 Spring chisel + Summer rodweed 0 390 0 Fall chisel + Spring skewtread 1300 1134 66 Fall chisel + Sunm.et rudwteti (j 779 130 LSD @0.05 ------860------36 showed a significant improvement in control over no-till, but with over 1300 seedlings m· 2 the following winter wheat crop will be devastated. The conventional tillage provided I 00% control ofjointed goatgrass seedlings at the soil surface. Jointed goatgrass densities ranged from 390 seedlings m·2 in the spring chisel plus summer rodweedings (Table II) to over 2300 in no-till. The only treatment that appeared to provide good overall control ofjointed goatgrass seedlings for all three depths was the spring chisel plus summer rod weeding. No difference was noted in the 5 to I 0 em depth. Jointed goatgrass spikelet and seedling densities at Beaver Dam were taken in 1994 , one year after they were taken at Promontory. Spikelet densities at Beaver Dam (Table 12) Table 12. Numbers of jointed goatgrass spikelets for three soil depths, Beaver Dam, UT. (October 1994) Depths Tillage 0- I em I- 5 em 5- 10 em ------No. m-z ------ No-till 1167 50 13 Fall subsoil + Spring skewtread 500 50 60 Fall subsoil + Summer rodweed 267 67 0 Spring chisel + Summer rodweed 433 67 33 Fall chisel + Spring skewtread 433 83 67 Fall chisel + St:mmer ro:lwe~d 133 117 33 [email protected] ------3 9 8 ------37 ranged from 267 spikelets m·2 in the fall subsoil plus summer rodweeder treatment to 1167 spikelets m·2 in no-till at the soil surface (0 to I em); however, no differences were found among tillages for the two lower depths (1 to 5 em and 5 to 10 em). Seedling densities at Beaver Dam (Table 13) followed the same pattern as spikelet densities in that no differences were found among tilled plots. Seedling densities for Beaver Dam at the surfaGe range(! from 100 (fall 2200 seedlings m·2 (no-till). As with spikelet densities, no differences existed among tillages for seedling densities at the two lower depths (1 to 5 em and 5 to 10 em). Although surface densities ofjointed goatgrass spikelets (Table 12) and seedlings Table 13 . Numbers ofjointed goatgrass seedlings for three soil depths, Beaver Dam, UT. (October 1994) Depths Tillage 0- 1 em 1-5 em 5- 10 em 2 ------No. m------ No-till 2167 58 13 Fall subsoil + Spring skewtread 300 33 0 Fall subsoil + Summer rodweed 800 67 0 Spring chisel + Summer rodweed 467 33 20 Fall chisel + Spring skewtread 433 42 27 Fall chisel -i SullmJe, rvdwc:eJ 633 50 20 LSD @0.05 ------581------38 (Table 13) for the tilled plots were significantly better than no-till, these densities were still not adequate for jointed goatgrass management from an economic perspective or in the minds of most farmers. Harvests were made in August 1994 at Promontory. The harvested samples were divided into jointed goatgrass and winter wheat. Total weight was measured and the weights ofjoint.,d goatgras s and winter wheat "!ere 3.l~o weighed individually. Th() values presented for the first two columns in Table 14 under percent jointed goatgrass and winter wheat were percentages in the harvest samples, representative of total percentages in the Table 14. Percentages of jointed goatgrass and winter wheat in harvest samples and wheat yield (kg ha-'), Promontory, UT. (September 1994) Tillage AEGCY1 Winter wheat Wheat yield ------%------kg ha·'------No-till 53 .2 44.3 371 Fall subsoil + Spring skewtread 73.7 24.6 461 Fall subsoil + Summer rodweed 5.4 93 .8 2031 Spring chisel + Summer rodweed 6.0 93 .3 2309 Fall chisel + Spring skewtread 60.2 37.5 418 Fall chisel + Summer rodweed 12.3 87.1 2018 [email protected] 9.7 9.6 412 1 4-letter approved WSSA code for jointed goatgrass from Composite List of Weeds, Revised 1989. Available from WSSA, 1508 West University Ave., Champaign, IL 61821- 3133. 39 plots. Notably, the percentages do not total I 00% because samples contained small amounts of inert material, such as other weed seeds, pebbles, dirt, chaff, and other debris. Percentage ofjointed goatgrass in wheat yield samples ranged from 5 to 74% and winter wheat percentages ranged from 25 to 94%. The three treatments with summer rodweedings (conventional tillage) had the lowest percentage of jointed goatgrass and the highest percentage of winter wheat. The treatment with the highest amount Qfjointed goatgrass and lowest winter wheat was the fall subsoil plus spring skewtreading. Wheat yields ranged from 418 to 2309 kg ha-1 The conventional tillage treatments provided the highest yields and were about five times greater than any of the other three tillage treatments. The conventional tillage did not provide perfect jointed goatgrass control; therefore, in the absence of a perfect control, it was difficult to predict wheat yield loss from the jointed goatgrass infestation at harvest. 40 SUMMARY AND CONCLUSIONS Greenhouse experiments suggest that winter wheat and jointed goatgrass react similarly to treatments of clomazone and that jointed goatgrass does not show differential sensitivity. Clomazone herbicide, therefore, is not a good candidate herbicide for selective control ofjointed goatgrass in winter wheat. Although planting winter wheat seed contaminated with jointed goatgrass is not a good practice, greenhouse experiments suggest that seed placement in the soil does play an important role in emergence of wheat and jointed goatgrass seedlings. Jointed goatgrass emergence was initially reduced at 2.5 em soil depth and did not germinate below 6.4 em, whereas wheat emergence was only initially reduced at the 5 em soil depth. Field studies were not conducted to verity greenhouse results. Presently available herbicides do not provide selective jointed goatgrass control in the winter wheat crop nor do they provide adequate control for jointed goatgrass control in fallow. However, treatments of2,4-D plus glyphosate in the spring of a fallow year provide good seedling control early and preemergence treatments of clomazone provide observed control. When conventional tillage, such as fall or spring chiseling, is followed by summer rodweedings, jointed goatgrass seedling control throughout the fallow can be achieved. This, however, does not provide control of or elimination ofjointed goatgrass seedbanks in the soil. By late fall, after planting winter wheat, no meaningful differences regarding jointed goatgrass control were found hetween the herhi"ides test<·d in tl>ese experiments, namely, 2,4-D, glyphosate, and clomazone. 41 The majority ofjointed goatgrass spikelets and seedlings in late fall of the fallow year are found at or very near the soil surface. The best seedbank control of jointed goatgrass throughout the fallow and the best hope for eliminating spikelets and seedlings prior to a cropping season is conventional tillage. Jointed goatgrass spikelet and seedling densities were so great in the conservation tillage and no-tillage regimes that economical wheat yields could not be achieved. In the absence of perfect jointed goatgrass control in any of the plots, it is difficult to determine, with reasonable accuracy, wheat yield loss from jointed goatgrass infestations; however, conventional tillage plots yielded five times more winter wheat than either conservation tillage or no tillage. Perfect jointed goatgrass control was not achieved in these experiments but the most likely management approach that farmers could use for jointed goatgrass control would be an integrated approach using 2,4-D plus glyphosate in the spring of the fallow year followed by conventional tillage. Other integrated approaches could also include crop rotations, burning, and possibly biocontrol. 42 LITERATURE CITED I . Ahrens, W.H. and E.P. Fuerst. 1990. Carryover injury ofclomazone applied in soybeans (Glycine max) and fallow. Weed Techno!. 4:855-861. 2. Anderson, R.L. 1989. Environmental factors influencing ethiozin bioactivity on jointed goatgrass. Proc. West. Soc. Weed Sci. 42:84-85. 3. Anderson. R.L. 1992. Effect of duration ofjointed goatgrass interference on winter wheat grain yield. Res. Prog. Rep .. West. Soc. Weed Sci. p. VI/2-VI/3 . 4. Anderson, R.L. 1993. Jointed goatgrass (Aegilaps cylindriea) ecology and interference in winter wheat. Weed Sci. 41:388-393. 5. Anderson, R.L. 1993. Managing the jointed goatgrass seed bank and assessing yield loss in winter wheat. Pages 43-47!.!! P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 6. Anderson, R.L. 1993 . Crop residue reduces jointed goatgrass (Aegilaps cylindriea) seedling growth. Weed Techno!. 7:717-722. 7. Anonymous. 1988. Official United States Standards for Grain. United States Standards for Wheat. U.S. Dep. Agric. Fed. Inspection Serv. 5 p. 8. Boerboorn, C.M. 1993. Current research in jointed goatgrass at Washington State University. Pages 27-28!.!! P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 9. Buman, R.A., D.R. Gealy, and A. G. Ogg, Jr. 1991. Inhibition of photosynthesis in downy brome (Bromus tee/arum) and jointed goatgrass (Aegilops eylindriea) protoplasts by metribuzin and its ethylthio analog. Weed Sci. 39:13-17. 10. Buman, R.A., D.R. Gealy, and A. G. Ogg, Jr. 1992. Effect of temperature on root absorption ofmetribuzin and its ethylthio analog by winter wheat (Triticum aeslivum), jointed goatgrass (Aegi/ops eylindriea), and downy brome (Bromus tee/arum). Weed Sci. 40:517-521. 43 11. Cartee, R.L., J.H. Slade, C.B. Thompson, and 1.0. Evans. 1993 . Effect of tillage treatments on annual grasses in winter wheat. Proc. West. Soc. Weed Sci. 46:117. 12. Curran, W.S., R.A. Liebl, and F.W. Simmons. 1992. Effects of tillage and application method on clomazone, imazaquin, and imazethapyr persistence. Weed Sci. 40:482-489. 13 . Donald, W.W. 1984. Vernalization requirements for flowering ofjointed goatgrass (Aegilops cylindrica). Weed Sci. 32:631-637. 14. Donald, W.W. 1991. Seed survival, germination ability, and emergence ofjointed goatgrass (Aegilops cy/indrica). Weed Sci. 39:210-216. 15. Donald, W.W. 1993 . Can knowledge ofjointed goatgrass biology help better manage this weed in winter wheat. Pages 52-57 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 16. Donald, W.W. 1994. A method of validating the tetrazolium assay for testing viability of dormant jointed goatgrass (A egilops cylindrica) seed. Weed Sci. 42:502-508. 17. Donald, W.W. and A.G. Ogg, Jr. 1991. Biology and control ofjointed goatgrass (Aegilops cylindrica), a review. Weed Techno!. 5:3-17. 18. Donald, W.W. and R.L. Zimdahl. 1987. Persistence, germinability, and distribution ofjointed goatgrass (Aegi/ops cylindrica) seed in soil. Weed Sci. 35 :149-154. 19. Dotray, P .A., and F.L. Young. 1988. Rooting development and its relationship to shoot growth in jointed goatgrass (Aegi/ops cy/indrica). Proc. West. Soc. Weed Sci. 41:74 (Abstract). 20. Do tray, P.A. and F.L. Young. 1993 . Characterization of root and shoot development ofjointed goatgrass (Aegilops cy/indrica). Weed Sci. 41 :353-361 . 21. Evans, J.O., T.M. Price, and S.A. Dewey. 1993 . Jointed goatgrass (Aegi/ops cy/indrica) response to integrated pest management programs in Utah. Pages 29- 36 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 44 22. Fleming, G.F. , F.L. Young, and A.G. Ogg, Jr. 1988. Competitive relationships among winter wheat (Triticum aestivum), jointed goatgrass (Aegilops cylindrica) and downy brome (Bromus tectorum). Weed Sci. 36:479-486. 23 . Gealy, D.R. 1987. Gas exchange properties ofjointed goatgrass (Aegi/ops cylindrica). Weed Sci. 35:482-489. 24. Gealy, D.R. 1988. Growth, gas exchange and germination of several jointed goatgrass (Aegi/ops cylindrica) accessions. Weed Sci. 36: 176-185. 25. Gealy, D.R. 1989. Response of gas exchange in jointed goatgrass (Aegi/ops cylindrica) to environmental conditions. Weed Sci. 37:562-569. 26. Gealy, D.R. and R.A. Buman. 1989. Response of photosynthesis and growth of jointed goatgrass and wheat to photosynthetic herbicides and temperature. Proc. West. Soc. Weed Sci. 42 :151-152. 27. Kindler, S.D. and T.L. Springer. 1989. Alternate hosts of russian wheat aphid (Homoptera: Aphididae). J. Econ. Entomol. 82:1358-1362. 28. Lish, J. , D. Thill, T. Carpenter, and F. Young. 1988. Jointed goatgrass longevity and dormancy in soil. Proc. West. Soc. Weed Sci. 41:32 (Abstract). 29. Lyon, D.J. 1993 . Jointed goatgrass research in Nebraska. Pages 17-21 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 30. Lyon, D.J. , D.D. Baltensperger and I. G. Rush. 1992. Viability, germination, and emergence of cattle-fed jointed goatgrass seed. J. Prod. Agric. 5:282-285. 31. Lyon, D.J. and I. G. Rush. 1993 . Processing reduces seed germination and emergence of jointed goat grass. J. Prod. Agric. 6:395-398. 32. Lyon, D.J., J.A. Smith, and D.D. Jones. 1994. Sampling wheat (Triticum aestivum) at the elevator for jointed goatgrass (Aegilops cylindrica). Weed Techno!. 8:64-68. 33 . Maan, S.S. 1976. Cytoplasmic homology between Aegilops squarrosa L. and A. cylindrica Host. Crop Sci. 16:757-761. 34. Miller, S.D. and J.M. Krall. 1988. Jointed goatgrass control in winter wheat. Res. Prog. Rep., West. Soc. Weed Sci. 41 :348. 45 35 . Miller, S.D. and T.L. Neider. 1993 . Jointed goatgrass research in Wyoming. Pages 22-26 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 36. Miller, S.D. and T. Whitson. 1987. Jointed goatgrass. Univ. Wyo . Coop. Ext. Serv. Bull. B-875. 3 p. 37. Nelson, J.E. 1985. A problem in winter wheat: Controlling jointed goatgrass. Mont. State Univ. Coop. Ext. Serv. Montguide 8516. 2 p. 38 Ogg, AG. 1993. Jointed goatgrass survey-- 1993, Magnitude and scope of the problem. Pages 6-12 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 39. Peeper, T.F. and J.A Koscelny. 1993 . Jointed goatgrass in Oklahoma wheat. Pages 58-59 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 40. Poster, J. 1986. Command herbicide: the rookie battles controversy. Crops and Soils Mag. Oct. p. 9-11. 41. Price, T.M. and J.O. Evans. 1995. Tillage and herbicide effects on jointed goatgrass populations and winter wheat yields. Proc. West. Soc. Weed Sci. 48 :in press. 42. Price, T.M. and J.O. Evans. 1995. Evaluation oftillage and herbicides in an integrated management approach for the control ofjointed goatgrass in winter wheat. Res. Prog. Rep., West. Soc. Weed Sci. In press. 43 . Price, T.M., J.O. Evans and S.A. Dewey. 1994. Integrating herbicide and tillage to manage jointed goatgrass densities in summer fallow of a wheat-fallow rotation. Res. Prog. Rep., West. Soc. Weed Sci. p. Ill/82-Ill/83. 44. Price, T.M., J.O. Evans and S.A. Dewey. 1994. Influence oftillage practices on emergence ofjointed goat grass in fall planted winter wheat. Proc. West. Soc. Weed Sci. 47:106-107. 45 . Renner, K.A. and G.E. Powell. 1992. Response of navy bean (Phaseolus vulgaris) and wheat (Triticum aestivum) grown in rotation to clomazone, imazethapyr, bentazon, and acifluorfen. Weed Sci. 40:127-133 . 46 46. Rydrych, D.J. I 986. Ethyl metribuzin for jointed goatgrass control in winter wheat. Res. Prog. Rep. , West. Soc. Weed Sci. p. 244. 47. Senft, D. I993. Stopping jointed goatgrass in winter wheat. USDNARS Agric. Res. Jan. I p. 48. Stahlman, P.W. I993 . Summary of research on jointed goatgrass in Kansas. Pages 48-5I in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 49. Swan. D.G. I984. Jointed goatgrass. Pac. Northwest Ext. Pub!. PNW0256. 4 p. 50. Westra, P. and T. D'Amato. I989. Jointed goatgrass control with ethyl metribuzin. Res. Prog. Rep ., West. Soc. Weed Sci. p. 398-399. 51. Westra, P., W. Stump, Z. Kebede, and K. Howatt. I993. Jointed goatgrass grass research and extension activities in Colorado. Pages 37-42 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 52. Willis, B.D. I990. Burning, flaming and herbicides for control ofjointed goatgrass (Aegi/ops cylindrica Host.) M. Sc. Thesis, Utah State University, Logan. 69 p. 53 . Willis, B.D., J.O. Evans, and S.A. Dewey. I988. Effects of temperature and flaming on germinability ofjointed goatgrass (Aegi/ops cylindrica Host.) seed. Proc. West. Soc. Weed Sci. 41:49-55. 54. Wood, M. 1994. New seed separator gets the goatgrass out. USDNARS Agric. Res. Jan. I p. 55 . Yenne, S.P., D.C. Thill, and R.H. Callihan. 1986. Jointed goatgrass control in winter wheat. Res. Prog. Rep ., West. Soc. Weed Sci. p. 240-243 . 56. Young, F.L., A. G. Ogg, Jr., and P.A. Dotray. 1990. Effect of postharvest field burning on jointed goatgrass (Aegilops cy/indrica) germination. Weed Techno!. 4:123-127. 57. Zemetra, R.S., J. Smith, J. Hansen, and M. Lauver. 1993 . The genetics ofjointed goatgrass and goatgrass X wheat hybrids. Pages 13-16 in P. Westra and R.L. Anderson, eds. Jointed Goatgrass: A Threat to U.S. Winter Wheat. Colorado State University, Ft. Collins, CO. 47 APPENDIX 48 Table 15. Analysis of variance for d!:,Y wei~ts for !£eenhouse clomazone study.' Parameter Source df ss MS F DryWts. Crop 304.0 304.0 116.35 ** Treatment 2380.6 793.5 303.71 ** C*T 3 95.3 31.8 12.16 ** Irrigation 119.7 119.7 45.81 ** C*I 6.0 6.0 2.30 T*I 3 38.9 13 .0 4.96 ** C*T*I 3 21.8 7.3 2.77 Error 32 83 .6 2.6 Total 47 3049.9 '* * represents significance at the I% level. 49 Table 16. Analysis of variance for greenhouse depth study. • Source df ss MS F Crop 8.00 8.00 12.17 ** Depth 8 1168.69 146.09 222.22 ** C*D 8 14.25 1.78 2.71 Error 54 35.50 0.66 Total 71 1226.44 '** and * represent significance at the I and 5% levels, respectively. 50 Table 17. Analysis of variance for visual estimates of clomazone Eh:z:!otoxici!_y.• Source df ss MS F Rep 0.2292 0.0764 Tillage 5 03542 O.o708 0.37 R*T 15 2.8958 0.1931 Chemical 4.6875 4.6875 61.35 ** R*C 0.2292 0.0764 r•c 5 0.6875 0.1375 1.09 Error 15 1.8958 0.1264 Total 47 10.9792 ' * * represents significance at the 1% level. 51 Table 18 . Analysis of variance for number ofjointed goatgrass seedlings emerging in fallow following fall tillage and herbicide treatments, Promontory, UT.' Source df SS MS F Rep 7129040 2376347 Tillage 469478816 93895763 76.90 .. R*T 15 18315440 1221029 Chemical 336605 112202 0.55 R*C 9 1833626 203736 T*C 15 2805680 187045 1.18 R*T*C 45 7149991 158889 Error 288 30348412 105376 Total 383 537397610 '* * represents significance at the I% level. 52 Table 19. Analysis of variance for number ofjointed goatgrass tillers in midsummer fallow following treatments of tillages and herbicides, Promonto!:Y, UT.' Source df ss MS F Rep 390632 130211 Tillage 5 11836296 2367259 21.30 ** R*T 15 1667068 111138 Chemical 3511067 702213 23 .83 ** R*C 15 442107 29474 T*C 25 12593275 503731 19.05 ** R*T*C 75 1982960 26439 Error 432 1447695 3351 Total 575 33871100 ' * * represents significance at the 1% level. 53 Table 20. Analysis of variance for comparison of herbicides in spring fallow, Beaver Dam, UT.' Source df ss MS F Rep 3 19047 6349 Herbicide 2148407 429681 17.13 •• R*H 15 376157 25077 Error 48 195476 4072 Total 71 2739087 •• • represents significance at the I% level. 54 Table 21 . Analysis of variance for fall counts of jointed goatgrass spikelets in fallow following fall wheat ~Ianting, Promonto!:Y, UT.• Source df ss MS F Rep 246049 82016 Tillage 5 18334580 3666916 23.30 ** R*T 15 2360750 157383 Herbicide 5 5018194 1003639 20.78 ** R*H 15 724582 48305 T*H 25 9719844 388794 4.02 ** R*T*H 75 7251715 96690 Depth 2 8270057 4135029 41.89 ** R*D 6 592267 98711 T*D 10 14059890 1405989 16 .16 ** H*D 10 4287359 428736 4.93 ** T*H*D 50 7518264 150365 1.73 ** R*T*H*D 210 18270974 87005 Total 431 96654525 '* * represents significance at the I% level. 55 Table 22. Analysis of variance for fall counts of jointed goatgrass seedlings in fallow following fall wheat Elanting, Promonto!)::, UT.' Source df ss MS F Rep 8864218 2954739 Tillage 5 44476780 8895356 29.25 •• R*T 15 4561879 304125 Herbicide 5 15038970 3007794 9.77 ** R"H !5 4619502 30?967 T*H 25 11714849 468594 1.26 R*T*H 75 27897730 371970 Depth 2 75285680 37642840 25.79 •• R*D 6 8758760 1459793 T*D 10 32478326 3247833 10.52 •• H*D 10 7185581 718558 2.33 T*H*D 50 20163098 403262 1.31 R*T*H*D 210 64807048 308605 Total 431 325852421 •• • and • represent significance at the 1 and 5% levels, respectively. 56 Table 23. Analysis of variance for fall counts ofjointed goatgrass spikelets in fallow following fall wheat Elanting, Beaver Dam, UT.• Source df ss MS F Rep 3 3055312 1018437 Tillage 5 579971 115994 1.01 R*T 15 1722706 114847 Herbicide 5 43961 8792 0.12 R~H 15 1088550 72570 T*H 25 1301927 52077 0.82 R*T*H 75 4748361 63311 Depth 2 19954218 9977109 10.87 R*D 6 5504830 917472 T*D 10 1401722 140172 2.03 H*D 10 134221 13422 0.19 T*H*D 50 2514432 50289 0.73 R*T*H*D 210 14466773 68889 Total 431 56516984 '*represents significance at the 5% level. 57 Table 24. Analysis of variance for fall counts of wheat seedlings in fallow following fall wheat Elanting, Beaver Dam, UT.' Source df ss MS F Rep 39100 13033 Tillage 5 284760 56952 3.24 R*T 15 263713 17581 Herbicide 101990 20398 1.75 R*H 15 174553 11637 T*H 25 378147 15126 1.10 R*T*H 75 1028063 13708 Depth 2 1543949 771975 113.75 •• R*D 6 40720 6787 T*D 10 796534 79653 5.66 •• H*D 10 225216 22522 1.60 T*H*D 50 751497 15030 1.07 R*T*H*D 210 29541 37 14067 Total 431 8582379 •• • and • represent significance at the I and 5% levels, respectively. 58 Table 25. Analysis of variance for percent jointed goatgrass, percent wheat, and total winter wheat ~eld for harvest, Prornonto!:Y, UT. • Parameter Source df ss MS F %JGG Rep 274.8 91.6 Tillage 112891.5 22578.3 200.83 ** R*T 15 1686.4 112.4 Herbicide 5 88.8 17.7 0.33 R*H 15 814.0 54.2 T*H 25 1267.2 50.6 1.12 Error 75 3384.1 45.1 Total 143 120406.8 %Wheat Rep 298.3 99.4 Tillage 5 122525.3 24505.0 215.06 ** R*T 15 1709.2 113.9 Herbicide 60.5 12.1 0.26 R*H 15 711.6 47.4 T*H 25 1176.1 47.0 1.10 Error 75 3213.2 42.8 Total 143 129694.2 Harv. Wt. Rep 23.1 7.7 Tillage 2248.9 449.7 77.02 ** R*T 15 87.6 5.8 Herbicide 5 15.1 3.0 2.29 R*H 15 19.8 1.3 T*H 25 24.0 0.9 0.94 Error 75 77.0 1.0 Total 143 2495.5 .-. represents significance at the 1% level.