Grass Control in Sugar Beet with the Herbicides
PROCEEDINGS—EIGHTH GENERAL MEETING 131 One test was made at Longmont, Colo., to find what influence date of
application of IPC might have on results. Applications were made at about 2-week intervals starting February 3, and ending May 14. Using barley as the test plant, and a standard rate of 3 pounds per acre IPC, good prac- tical control was obtained from all dates of application. Soil moisture content and soil temperature were obtained at each time of application.
Moisture content varied from 5 to 13 percent, and temperature from 41°
to 59° F. With the exception of the February 14 date of application, soil temperature at the 1- to 2-inch depth was within the range of 55° to 59°
F. In this test the later applications gave slightly better control and were accompanied by more moisture.
In commercial use it was observed that IPC was more phytotoxic under conditions of warm temperature and good growing conditions. During cool temperatures the apparent action of IPC on plants was slow; however, under these conditions the persistence of IPC in the soil was much prolonged. T h e final control obtained with IPC was satisfactory even under cool tempera- tures, although there was a period in which it was questionable whether control would be satisfactory. In many instances during the spring of 1953 the wild oats and grain emerged and later died. This was a new ex- perience since, in experimental trials conducted during 1951 and 1952, these weeds usually died before reaching the surface of the soil. T h e eventual kill of emerged weeds was accompanied by warm temperatures and drying winds. Apparently, under these conditions, the restricted root sys- tem of the weeds did not provide adequate absorption of water to keep them alive. T h e emergence of the weed is proof that the level of IPC in the soil is inadequate under the existing conditions. Thus, in view of the lower activity of IPC under cool temperatures, rates of 3 to 5 pounds per acre might be considered by some growers making early application, espe- cially if the price of IPC is reduced so that chemical control at the higher rates would compete with other means of control. At the present prices of IPC, the rate of 3 pounds per acre does give fairly economical control, and the percentage control has usually been more than 85 percent.
Injury to sugar beets by IPC applications at the 3-pound per acre rate was negligible. In one case where IPC application was late (April 30) , and the farmer had an unusually hard seedbed so that discing was only 21/2 inches, there was noticeable retardation in growth of sugar beets in the early seedling stage. By thinning time, there was no apparent difference.
During sunny weather it is especially important to incorporate IPC into the soil immediately after spraying, plus immediate refirming of soil to prevent loss by volatilization. Loss of IPC at temperatures of 85° to 88° F.
was found to be about 80 percent within a 24-hour period by Anderson, et al, (1) when spread as a thin layer.
TCA and DCU
Eight field tests were initiated in the spring of 1953 to compare the effectiveness of T C A and DCU for control of foxtail (Setaria) and barn- yard grass (Echinochloa) . These followed tests in the greenhouse which
132 A M E R I C A N S O C I E T Y O F SUGAR B E E T T E C H N O L O G I S T S
showed D C U t o b e effective w h e n m i x e d w i t h t h e surface soil for c o n t r o l o f grass. Grass c o n t r o l w i t h D C U was i n d e p e n d e n t of d i r e c t i o n of m o i s t u r e m o v e m e n t in t h e soil. See F i g u r e 2.
Figure 2.—Test s h o w i n g control of green foxtail grass (setaria) w i t h D C U without stunting broadleaf weeds or sugar beets. T r e a t m e n t s : left to right—0, 10, 20 a n d 40 p o u n d s of 73 percent active f o r m u l a t i o n of D C U a p p l i e d as a spray a n d incorporated in surface soil to a d e p t h of 1 inch.
Foreground flats, sprinkle irrigated. B a c k g r o u n d flats, subirrigated.
T e s t s w e r e m a d e i n C o l o r a d o , W y o m i n g a n d M o n t a n a . R a t e s o f 7.3 p o u n d s p e r a c r e t e c h n i c a l d i c h l o r a l u r e a ( D C U ) a n d 7.2 p o u n d s p e r a c r e acid e q u i v a l e n t o f s o d i u m t r i c h l o r o a c e t a t e ( T C A ) w e r e used. I n some tests a r a t e o f 14.6 p o u n d s p e r acre D C U was used, also. T h e D C U u s e d was a w e t t a b l e p o w d e r , a n d was a p p l i e d in w a t e r s u s p e n s i o n at a v o l u m e e q u i v a l e n t to 20 g a l l o n s p e r a c r e . P l o t s w e r e 28x400 feet in size. A l l t r e a t e d p l o t s w e r e b o r d e r e d o n b o t h sides b y a check p l o t . T h e h e r b i c i d e s w e r e a p p l i e d a s a s p r a y p r i o r t o p l a n t i n g , a n d w o r k e d i n t o t h e soil b y s h a l l o w discing o r h a r r o w i n g . T h e c o n t r o l o f grass was g o o d o n all t r e a t e d p l o t s e x c e p t i n t h e case o f o n e test. I n t h i s test t h e c o n t r o l w i t h D C U was excel- l e n t , w h i l e T C A gave n o visible c o n t r o l . T h e test j u s t r e f e r r e d t o was s t a r t e d M a r c h 26, w h i l e o t h e r tests i n t h e s a m e d i s t r i c t w e r e a p p l i e d a p p r o x i m a t e l y o n e m o n t h later. T h e D C U , b e i n g w a t e r i n s o l u b l e , a p p a r e n t l y stayed i n t h e effective soil layer d u r i n g A p r i l a n d M a y w h e n m o s t o f t h e grass seeds g e r m i n a t e d . Grasses s u r v i v i n g o n D C U p l o t s w e r e m a l f o r m e d , a n d l a c k e d vigor t h r o u g h J u n e . Grass seedlings s t a r t i n g i n J u l y a p p e a r e d n o r m a l ; how- ever, t h e y s u c c u m b e d t o s h a d i n g b y t h e d e n s e b e e t foliage a t t h a t t i m e .
A t r a t e s used, T C A was m o r e i n j u r i o u s t o s u g a r b e e t s t h a n D C U . T h i s i s i n d i c a t e d i n p r e - t h i n n i n g s t a n d c o u n t s o n o n e f i e l d . T h e r e was n o in- d i c a t i o n in a n y of t h e tests t h a t t h e chemicals m i g h t adversely affect yield.
I t was e x p e c t e d t h a t i n o n e f i e l d w h i c h was especially foul w i t h foxtail grass a yield increase w o u l d b e o b t a i n e d o n t h e t r e a t e d p l o t s . T h i s was sub- s t a n t i a t e d i n h a r v e s t results o b t a i n e d for L o c a t i o n 15, a n d r e p o r t e d i n T a b l e 1.
PROCEEDINGS—EIGHTH GENERAL MEETING 133 Table 1.—Stand, Yield and Percentage Sugar of Sugar Beets Grown on DCU and TCA
Treated Plots.
1 Weights of paired samples of beets grown on treated and untreated soil were adjusted proportionately for local area affected by an obvious variation in field. Most of area within test was uniform, and thus only a single check value is carried.
NS = no significant differences at indicated level.
Location 16, sampled for yield and sugar, showed no significant differ- ence in yield, Table 1. T h e latter field was practically free of weeds all season, and use of herbicides under such conditions would not have been expected to be beneficial.
T h e commercial use of TCA on a limited scale during 1950 through 1953 in territories served by the Great Western Sugar Company has indicated that 5 pounds per acre TCA, acid equivalent, is about the highest rate one might advocate for use on sugar beets of this area. Even then injury has occurred on occasions, and in other cases no effect on beets or weeds has been noticeable.
Summary
In tests and in commercial use IPC has been found to give effective control on wild oats and volunteer grain in at least 85 percent of all cases, as observed in areas within Colorado, Wyoming and Montana served by the Great Western Sugar Company. General usage to date, which included 4,800 acres treated in the spring of 1953, has been to apply as a spray 3 pounds per acre technical IPC during seedbed preparation, and double discing to a depth of 3 to 4 inches immediately after application. Final seedbed preparation and planting of sugar beets followed as soon as practical.
Tests using TCA and DCU were made to compare effectiveness of treat- ments in controlling foxtail and barnyard grass. Applications of TCA at 7.2 pound per acre, and DCU at 7.3 and 14.6 pounds per acre, were made prior to planting, and chemicals incorporated with soil surface by harrow- ing or shallow discing. In most tests TCA and DCU controlled foxtail grass equally well. Under conditions where TCA failed to controll grass DCU gave good control. DCU was less injurious to sugar beets than TCA. In
134 A M E R I C A N S O C I E T Y O F SUGAR B E E T T E C H N O L O G I S T S
the l i m i t e d c o m m e r c i a l use of T C A a r a t e of 5 p o u n d s p e r acre, acid equiva- lent, i s a b o u t t h e u p p e r r a t e o n e m i g h t a d v o c a t e for use w i t h i n areas o b s e r v e d , i n c l u d i n g p a r t s o f w e s t e r n N e b r a s k a , C o l o r a d o a n d M o n t a n a .
Literature Cited
( 1 ) A N D E R S O N , W . P O W E L L , L I N D E R , P A U L J . a n d M I T C H E L L , J O H N W . 1952. E v a p o r a t i o n of some p l a n t g r o w t h r e g u l a t o r s a n d its possible
effect on t h e i r activity. Science 116:502-503.
(2) D E M I N G , G. W.
1950. Use of I P C for w e e d c o n t r o l in sugar beets. P r o c . A m e r . Soc.
S u g a r Beet T e c h . 453-455.
(3) N E L S O N , R . T .
1951. Some results o n c h e m i c a l w e e d c o n t r o l . T h r o u g h t h e Leaves 3 9 (5) :41-44.
(4) N E L S O N , R . T .
1952. T r i a l s w i t h h e r b i c i d e s for weed c o n t r o l in sugar beets. P r o c . A m e r . Soc. S u g a r B e e t T e c h . 121-125.
(5) N E L S O N , R . T .
1953. O b s e r v a t i o n s o n c o m m e r c i a l use o f I P C . T h r o u g h t h e Leaves 41 (4) : 16-19.