Soil conservation and chemical weed management in hillside orchard-香川大学学術情報リポジトリ

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Tech Bull Fac A ~ I Kagawa Univ, Vol 46, No ?, 163-168, 1994



Katsura MANABE and Matsuo ITOH*

Three foliar applied herbicides, glyphosate, glufosinate and the glyphosate/ bialaphos mixture, and a dwarf agent, pachlobutolazole, were studied to define potential of them for the replacement of hand mowing regarded a s the hard labor in hillside orchards Nine weed species naturally emerged at the Experimental Farm, Kagawa University, were examined The glyphosate/bialaphos mixture had the widest spectrum among 4 tested chemicals The mixture consistently provided excellent growth inhibition to 60-85 % on 8 species except Sterallta medta killed by the mixture Other 3 chemicals worked species-specifically The burndown activity of foliar applied herbicides appeared to provide the flexibility of chemical application timing, resulting in the grower's preferences to sod culture, because the application of dwarf agents is restricted to small plants

The regrowth of Imperata cyltndrtca and Artemtsta prtnceps applied with the glyphosate/bialaphos mixture was slower than that of those species mowed at 5 cm The mixture kept plants shorter than 50 cm for more than 60 days after application

Key words : dwarf agent, hand mowing, hillside orchard, foliar applied herbicide, sod culture


Terrace culture was introduced to hillside orchards in Japan for soil conservation(" Fruit trees are generally planted in the flat areas on the terrace As the flat area on the terrace is effective to achieve easy management of fruit trees, this cultivation has saved more operational time and labor than direct planting on the slope Perennial grasses are often seeded on the side of the terrace to prevent it from erosion especially in a rainy season") T h e soil conservation using the grasses in hillside orchards has been popular because it doesn't require any expensive construction However, annual and perennial weeds often take over the seeded perennial grasses in several years(') Thus, the weed management on the terrace side is one of the important work in orchard managements to conserve the terrace soil Hand mowings or herbicides such a s the paraquat/diquat mixture have been applied to control weeds to be short on the terrace side(3), while soil surface on the terrace has been kept clean with heavy use of herbicides to provide fruit trees with sufficient resources

Considered that hand mowings require hard labor in hillside farming, chemical weed management using herbicides or plant regulators such a s dwarf agents is regarded as the most convenient way to achieve the weed sod culture(2) However, the mixture of paraquat/diquat is * ~ o n s a n t o Japan Ltd 7712 Kawachi, Inashiki, Ibaraki, Japan 300-13


164 Tech Bull Fac Agr Kagawa Univ, Vol 46, No 2, 1994

not good enough in weed control term(34' Grass plants applied with the mixture generally regrow quickly after the herbicidal damage Soil applied herbicide or glyphosate enables orchards to be clean for a long time, but the heavy use of those herbicides sometimes causes poor weed vegetation resulting in the soil erosion in hillside orchards This study was carried out to investigate potential of 3 commercial foliar applied herbicides and a dwarf agent to replace for the hand mowing in hillside orchards




Three foliar applied herbicides, glyphosate, glufosinate and the glyphosate/ bialaphos mixture and a dwarf agent, pachlobutolazole, were examined in citrus and peach orchards a t Kagawa University in 1990 Chemicals were applied at the commercially recommended rates with 1,000 l/ha of water carrier T h e used rates were 0 9 kg ae/ha of glyphosate, 1 0 kg ai/ha of glufosinate, 0 7/0 4 kg ae/ai / h a of glyphosate/ bialaphos mixture and 2 0 kg ai/ ha of pachlobutolazole A total of 9 weed species, 5 annual weeds and 4 perennial weeds, were tested at rather small-sized stage (Table 1) Eight species among 9 were sprayed on at 10 to 20 c m height except Digztarza ad,scenden.s Exceptionally, rather large-sized plants of D adscendens (25 to 35 c m height) were used for this experiment due to the quick growth of this species a t the application time All species at the application time were short enough to keep them in sod culture with chemicals Chemical applications were carried out 3 times separately (Feb 15, March 23 and May 25) to cover weed species naturally emerged in various seasons Plots were randomized complete block design with 3 replications Plot size was 4 rn2 (2m x 2m) Visual assessments comparing to the untreated plot were made for each species With the concept of dwarf agent, plants controlled to 60 to 85 % against untreated ones were considered to be suitable for sod situation Plant height was measured on 2 perennial species,

Table 1 Size of tested weeds

Application Weed species Abbreviation Size (a) date (1990) Annual grass weeds

Dtgztarta ad.scendens A1opecuru.s aequalzs Annual broadleaf weeds

Sterallia media Vicia sativa Veroni'ca peregri'na Perennial grass weed lmperata c,ylindrica Perennial broadleaf weeds

Artemi.sia princep.s Solidago alti.ssima Rumex japonica May 25 Feb 15 Feb 15 Feb 15 Feb 15 May 25 March 23 March 23 Feb 25


K MANABE and M ITOH : Chemical weed management in hillside orchard

Imperata c ylzndrzca and Artemzsza prznceps in comparison with hand mowings

Results and Discussion

Growth inhibition of 9 weed species at 55 to 64 days after application is shown in Fig 1 T h e glyphosate/bialaphos mixture had the widest spectrum among 4 tested chemicals T h e mixture consistently provided excellent growth inhibition to 60-85 % on 8 species except S medza killed by the m i x t u ~ e A dwarf agent, pachlobutolazole, worked species-specifically T h e compound a t 2 0 k g ai/ ha inhibited the growth of 4 weed species, Alopecurus aequalzs, Sterallza medza, Artemzsza prznceps and Rumez ~aponzca However, almost no practical

inhibition was observed on Vzcza satzva, Imperata cylzndrzca and Solzdago altzsszma with

pachlobutolazole Species-specific activity was also observed with glyphosate and glufosinate Glyphosate a t 0 9 kg ae/ha stunted 4 perennial weeds and V satzva, but it almost killed other

4 annual weeds Glufosinate a t 1 0 kg ai/ha inhibited the growth of D adscendens, Veronzca peregrzna and A prznceps, but it killed other 3 annual weeds T h e activity of glufosinate at this rate was not good enough to stunt perennial weeds except R laponzca

Inhibition patterns with time after application were shown in Fig 2 Pachlobutolazole didn't show any visible burndown symptoms with foliar applied herbicides Glyphosate worked a s slow a s pachlobutolazole, but it killed annual weed species, unlike pachlobutolazole T h e glyphosate/bialaphos mixture and glufosinate burndowned plants quickly up to more than 85 % inhibition, and then the plants injured gradually started growing again In 3 species, D

adscendens, I cylzndrzca and A prznceps, plants applied with the glyphosate/ bialaphos

mixture regrew more slowly than the ones applied with glufosinate Mo~eover, the regrowth of plants applied with the glyphosate/bialaphos mixture was slower than that of plants mowed a t 5 c m (Fig 3) T h e mixture kept plants shorter than 50 cm for more than 60 days after

Pachlobutolazole Glyphosate


bialaphos Glyphosate Glufosinate

Fig 1 Activity of 4 tested chemicals on 9 weeds species at 55 to 64 days after application Bars represent the inhibition on, from the left, DA, AA, SM, VS, VP, IC, AP, SA and RJ respectively @, annual weeds :

0 ,

perennial weeds The range from 60 to 85 % inhibition represents the acceptable activity at the observation times on each species


166 'Tech Bull Fac Agr Kagawa Univ, Vol 46, No 2, 1994

Days after treatment

Fig 2 Changes in activity on Dtgttarta adscendens (DA), Sterallza medta (SM), Imperata c yltndrtca (IC) and Artemzsza prtnceps (AP).


pachlobutolazole at 2 0 kg ai/ ha


0 , glyphosate+bialaphos mixture at 0 7


0 4 kg ae/ai/ha : A , glyphosate a t 0 9 kg ae/ha :


glufosinate a t 1 0 kg ai/ha

Days after treatment

Fig 3 Changes in plant height of Imperata cyltndrtca (IC) and Arterntsta prtndeps (AP). 0 , glyphosate


bialaphos a t 0 7


0 4 kg ae/ai/ha : A , mowing a t 5 cm height




A s mentioned above, t h e mixture of glyphosate/bialaphos current1.y appears to be t h e best way among tested chemicals t o keep plants short in t e r m s of spectrum and control term T h i s


K MANABE and M IIOH : Chemical weed management in hillside orchard 167 is because the mixture has burndown activity from bialaphos and the growth inhibition from glyphosate(5) T h e burndown activity of foliar applied herbicides seems to be one of the great preferences of the growers to sod culture, a s well a s strong inhibition of plant growth T h e burndown removes the top of plants a s mowing does, resulting in providing growers with the flexibility of application timing of chemicals This is one of the reasons why growers use herbicides widely T h e application of dwarf agents applied postemergence is generally restricted to small plants(2)

A s shown in Fig 1 , no chemicals stunt all weed species consistently This result suggests that chemical mowing will change the weed vegetation a s herbicides have done in orchards In general, perennial plants are more suitable than annual plants a s cover plants for soil conservation Therefore, it seems to be desirable to choose chemicals stunting perennial weeds effectively

A s reported previously, winter weeds are taken over by summer weeds in early summer in Setouchi region@) T h e emergence of summer weeds is dependent on when winter weeds die Killing winter weeds with mowings or foliar applied herbicides in March to April accelerates the takeover by summer weeds, while intact winter weeds grow up to June If winter weeds were killed in spring t o early summer, two more chemical applications would be required to control summer weeds in this region, because summer weeds would emerge earlier than normal and grow for a long time Considered the labor saving with chemical applications, it is desirable to let winter weeds be short until they die naturally in summer Therefore, chemicals stunting plants for 2 months should be applied in March to April when winter weeds are still short enough, and then another application will be required after rainy season to keep summer weeds short T w o chemical applications in a cropping season will be possible with this concept T h e glyphosate/bialaphos mixture will fit for the concept mentioned above Stunt plants applied with this mixture were short enough in about 2 months although they gradually regrew with time to the unacceptable level after then

In order to use the glyphosate/bialaphos mixture effectively for chemical mowing, it is required to list up the weed species stunt with the mixture, and to investigate the application timing in a year-long calendar


T h e authors wish to thank to Mrs H Deguchi, H Yabuki and H Yamasaki of Experimental Farm, Kagawa University, for their assistance in this study


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