TECHNICAL BULLETIN 173 ISSN 0070-2315

PERSISTENCE OF FLUROCHLORIDONE

AND TERBUTRYN IN SOIL

N.A. Vouzounis and P.G. Americanos

:====....===

- 9MAY 1996 .•UCULTURAL R, .,Lt\RCH

INS1ITUTE

AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE, NATURAL RESOURCES AND

THE ENVIRONMENT

NICOSIA CYPRUS

OCTOBER 1995

PERSISTENCE OF FLUROCHLORIDONE AND TERBUTRYN IN SOIL

N.A. Vouzounis and P. G. Americanos

SUMMARY

The residual activity of flurochloridone and terbutryn on many vegetable crops sown in spring, autumn and winter was evaluated in two soil types by means of bio­assays. Persistence, measured as biological activity, was shorter for terbutryn than for flurochloridone. Degradation was most rapid in spring and slowest following autumn or winter application. Soil type affected the longevity of phytotoxicity in the case of spring application of flurochloridone only. Flurochloridone phytotoxicity persisted for more than 32 weeks on the most sensitive crops while terbutryn persisted for shorter periods (14-20 weeks). Carrot, celery, chickpea, coriander, okra, parsley and peanut were tolerant to the residues of both herbicides.

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I

INTRODUCTION with flurochloridone observed bleaching ef­fects for more than one year. Cesari et al.

Weeds in irrigated crops, and especially (1975) found terbutryn residues to be toxic in vegetables, have become a very serious to spinach and beetroot 82-144 days after the problem in Cyprus because of the favourable last application. In the present work, bioas­climate and the intensification of agriculture. says were used to study the persistence of The scarcity and high cost of labour make flurochloridone and terbutryn under different the use of soil-acting herbicides imperative. conditions. The objective was to determine A range of herbicides are used at appropriate the safe-sowing intervals for a range of crops rates for each soil type. Two residual herbi­ following application of flurochloridone and cides with long persistence namely fluroch­ terbutryn on two soil types in three different loridone and terbutryn, can have disastrous seasons. effects on succeeding sensitive crops. Al­though flurochloridone has not yet been reg­ MATERIALS AND METHODS istered in Cyprus it was found that it can be

Flurochloridone and terbutryn were ap­used effectively in potatoes to control spe­pliedcies of the resistant weed Gaiium (Ameri­ on two soil types, a clay-loam (35% clay, 1.25% organic matter (O.M.), 21%canos et ai. 1994), and as a pre-emergence CaC03, pH 8,0), and a clay (50% clay, herbicide in okra (Americanos and Vouzou­

nis 1991). 1.25% O.M., no CaC03, pH 7.4). For flu­lunila et al. (1994) using lettuce bioas­ rochloridone rates of application were 0.5 kg

says with soils cropped with potatoes treated on the clay-loam and 0.75 kg/ha on the clay

3

and for terbutryn 1.5 kg and 2.0 kg/ha on the c.lay-loam and c.lay, respectively. Applica­tIons were made In autumn (October), winter (January), and spring (March), so that the rate of dissipation of the herbicides under different weather conditions could be stud­ied. They were repeated in two years, i.e. 1991-92 and 1992-93. The herbicides were applied with a knapsack sprayer fitted with a flat fan nozzle delivering 500 l/ha on plots 3 x 1 m arranged in a randomized complete block and replicated four times. All plots w~re .sprinkler-i~ig~ted the day prior to ap­plIcatIOn and agaIn Immediately after.

Beginning two weeks after application and at three-or-four-week intervals thereaf­ter, 15 seeds of each test crop were sown in all treated as well as in untreated control pl?ts to dept~s appropriate for each species. Pnor to SOWIng the top soil (10-15 cm) was worked to a tilth with a spade in a way that mixed the soil thoroughly.

The plots were irrigated after sowing and subsequently as required for the duration of the trials. When germination was complete emerged seedlings were thinned to 10 in each plot.

Fast-growing crops were allowed to grow for three weeks and slow growing ones for four weeks before the activity of the herbi­cides was visually assessed. Visual assess­ment was preferred to fresh weight reduction determination since according to Krauskopf and Wetcholowsky (1990) this method seems to be a less time consuming and a more efficient tool for monitoring degrada­tion processes with bioassays. When reduc­tion in growth, as visually assessed, fell to 10% or less it was considered that the crop concerned could be safely sown in treated soil. The scientific names of test crops ap­pear in Appendix G while Fig. 1 shows the monthly mean temperatures during the peri­od of the trials.

RESULTS AND DISCUSSION

The se!1sitive periods for all crops after flurochlondone and terbutryn application are shown in Table 1. Appendices A to F show the progress in time of the reduction in growth of the crops. In both the table and the appendices absence of data indicates that it was either too cold or too hot to sow the crop concerned or that sowings were discontinued

4

because of germination problems. Thus, for example February is too cold to sow cucum­ber while June is too hot for onions.

Flurochloridone Following spring application of fluroch­

loridone, cabbage, cauliflower, chard, pep­per, cucumber, eggplant, lettuce, marrow, melon, onion, radish and watermelon were sensitive to residues for 14 to over 23 weeks while carrot, celery, chickpea, okra, parsley and peanut were tolerant. Cowpea, French bean, purslane and tomato were found to be intermediate, with sensitivity ranging from 8-11 weeks (Table 1). Flurochloridone at 0.5 kg/ha was shown to be suitable as a pre­emergence treatment in okra (Americanos and Vouzounis 1991). Similar results were obt.aine? for the above crops following appli­catIon In autumn and winter but herbicide persistence was prolonged, ranging from 20 to over 41 weeks for the most susceptible crops (Table 1).

Broadbean, cowpea and French bean, all me~~ers of the Leguminoseae family, were senSItIve to flurochloridone residues for 8-17 weeks, while spinach and the graminaceous crops barley, oat, ryegrass and wheat were sen.sitive fo: m?re than 20 weeks. Following sprIng applIcatIOn of flurochloridone sensi­tivity. of most c~ops was shorter in the heavy' than In the medIUm soil. This is attributed to greater adsorption of the herbicide on the clay colloids of the heavy soil. Walker et al. (1985), a~d. Harper (1988), working with ?ther herbICIdes found that their adsorption Increased as the clay content of the soil in­creased. After autumn application sensitivity to flurochlori~one residues lasted, for many crops, longer In the heavy than in the medi­um soil. This is attributed to the high amount of rainfall which followed the application in that period and leached the herbicide faster in the medium than in the heavy soil. Ando et al. (1987) investigating the movement of other herbicides found that they moved more easily in soils of low clay content and that the degree of movement increased with in­creasing value of precipitation.

Terbutryn Terbutryn was less persistent than flu­

rochloridone, with phytotoxicity lasting for 11 wee~s following spring application, 17 weeks In autumn and 20 weeks in winter

Table 1. Safe sowing interval for various crops following application of flurochloridone and terbutryn* in spring, autumn and winter on a clay loam soil (M) and a clay soil (H)

Safe sowing interval (weeks after application)

Crop Soil Flurochloridone Terbutryn type

Spring Autumn Winter Spring Autumn Winter

Barley M >20 8 H >20 11

Beetroot M 20 14 >11 14 H 20 11 >11 14

Broadbean M 8 2 H 17 2

Cabbage M >23 >41 <20 11 H <20 >41 <20 11

Carrot M 2 2 2 2 2 2 H 2 2 2 2 2 2

Cauliflower M >23 >41 <20 5 H <20 >41 <20 8

Celery M 2 <23 <11 2 <23 <11 H 2 <23 <11 2 <23 <11

Chard M 14 17 17 11 14 17 H 14 20 17 11 14 20

Chickpea M 2 2 2 2 2 2 H 2 2 2 2 2 2

Coriander M 2 2 2 2 H 2 2 2 2

Cowpea M 11 <23 11 5 <23 2 H 8 <23 11 5 <23 2

Cucumber M 20 32 20 8 <23 11 H 14 32 20 11 <23 14

Eggplant M 20 32 23 2 <23 <8 H 14 35 20 2 <23 <8

French bean M 8 <23 8 5 <23 2 H 8 <23 8 8 <23 2

Lettuce M >23 38 20 2 <20 <8 H 17 >38 20 2 <20 <8

Marrow M 23 32 17 5 <23 11 H 14 35 20 8 <23 14

Melon M 20 32 23 8 <23 11 H 14 32 20 8 <23 11

Oat M >20 8 H >20 11

Okra M 2 <23 <8 2 <23 <8 H 2 <23 <8 2 <23 <8

Onion M 17 32 23 11 11 14 H 14 32 23 11 11 14

Parsley M 2 2 2 2 2 2 H 2 2 2 2 2 2

Pea M 5 2 2 2 H 5 2 2 2

Peanut M 2 <26 <11 2 <26 <11 H 2 <26 <11 2 <26 <11

Pepper M 14 35 20 5 <23 <8 H 14 35 20 5 <23 <8

Ito be continued

5

Table 1 continued

Purslane M 11 29 17 8 <26 <11 H 11 29 20 8 <26 <11

Radish M >23 41 32 5 8 5 H 17 41 26 5 11 5

Ryegrass M >20 11 H >20 11

Spinach M >20 >11 14 11 H >20 >11 17 11

Tomato M 8 <23 8 2 <23 <8 H 8 <23 11 2 <23 <8

Vetch M 2 2 H 2 2

Watermelon M 17 32 23 5 <23 <8 H 14 32 17 5 <23 11

Wheat M >20 11 H >20 11

* Rates of application, kglha in a medium and heavy soil respectively:flurochloridone 0.5, 0.75, terbutryn 1.5,2.0

30

/ / .--­ --- --­

/•/

"""""-.25 1--- 1991-92 --- 1992-93 1 '/

/

/

/•/

>- I \ /\ /

\ /\ / \ I

~

I I

I I

I I

I /

/ •10 ..........- //

/

~~.

5 o N o J F M A M J J A s month

Figure 1. Average manthly mean temperature (0C) during the experimental period. Athalassa meteor­ological Station.

6

(Table 1). Thus, damage was observed in chard, cowpea, cucumber, French bean, mar­row, melon, onion, pepper, purslane, radish and watennelon for 5-11 weeks after spring application, whereas following autumn or winter treatments, symptoms were evident for 11-14 weeks in most of those crops. The most sensitive crops were spinach after au­tumn and chard after winter treatment, with phytotoxic symptoms appearing for upto 17 and 20 weeks respectively.

The cereals barley, oat, ryegrass and wheat were affected for a period of 11 weeks. Many crops exhibited good tolerance of ter­butryn and were safely sown in treated soil two weeks after application (Table 1). They included broadbean, carrot, celery, chickpea, coriander, eggplant, lettuce, okra, parsley, pea, peanut, tomato, and vetch. Terbutryn is recommended in Cyprus for pre-emergence application to peas, broadbeans and okra (Americanos 1984; 1986; Americanos and Vouzounis 1991). The longevity of the phy­totoxicity of terbutryn in the two soils was in most cases similar because higher rates were applied to the heavy soil to compensate for the increased adsorption on the clay. Barriuso and Calvet (1992) in their investigations with different residual herbicides, including terbu­tryn, found a clear relationship between soil types and herbicide adsorption but the latter was also highly dependent on the electrical state of the herbicides (i.e. whether cationic, anionic or neutral).

Season and, therefore by implication tem­perature, was the major factor influencing activity of biological residues. Thus, the two herbicides dissipated faster after spring ap­plicaf'Jn when ambient temperatures were higher (Table 1, Fig. 1). Similar results have been reported for several other herbicides (Walker and Allen 1984; Vouzounis and Americanos 1992, 1995; Americanos and Vouzounis 1995).

In conclusion, the use of bioassays to de­termine safe-sowing intervals provides use­ful infonnation for Cypriot farmers enabling them to select crop rotations within multiple cropping sequences least likely to suffer damage from herbicide residues. However, the data in Table 1 must be viewed as an in­dication only, since the safe-sowing intervals reported here will be influenced by environ­mental factors (temperature, rainfall and irri­gation), soil type and crop cultivar sown.

One way to reduce the risk of toxicity from herbicide residues is to plough deeply in preparation for follow-up planting (Gottes­bueren et al. 1992).

ACKNOWLEDGEMENTS

We express our thanks to Dr. G. Orpha­nides and Dr A. Papasolomontos for the crit­ical reading and helpful criticism of the man­uscript. The technical assistance of Mr G. Economides in the field is acknowledged with thanks.

REFERENCES

Americanos, P.G. 1984. Herbicides for peas. Technical Bulletin 62, Agricultural Re­search Institute, Nicosia. 7p.

Americanos, P.G. 1986. Herbicides for broad­beans. Technical Bulletin 76, Agricultural Research Institute, Nicosia. 4p.

Americanos, P.G. and N. A. Vouzounis. 1991. Herbicides for okra. Technical Bulletin 127, Agricultural Research Institute, Ni­cosia.6p.

Americanos, P.G., N.A. Vouzounis and S. Chris­tofi. 1994. Chemical control of Galium in potatoes. Technical Bulletin 164, Agricul­tural Research Institute, Nicosia. 7p.

Americanos, P.G. and N.A. Vouzounis. 1995. Re­sidual activity of chlorthal-dimethyl, me­tribuzin and prometryn determined by bi­oassays in field trials. Technical Bulletin 167, Agricultural Research Institute, Ni­cosia.8p.

Baniuso, E. and R. Calvet. 1992. Soil type and herbicide adsorption. International Jour­nal of Environmental Analytical Chemis­try 46: 117-128.

Cesari, A., P. Flori and G. Malucelli. 1975. Effetti fitotossici determinati da residui di diser­banti su colture in rotaziene. Notiziario sulle Malattie delle Piante. No 92/93: 191-208. Bologna, Italy.

Gottesbueren, B., W. Pestemer and D. Bunte. 1992. Application of a simulation model (VARLEACH) for calculation of herbi­cide distribution in the soil under field conditions. Part. 2. Implementation into the expert system HERBASYS. Zeits­chrift-fuer-Pflanzenkrankeheiten-und­Pflanzenschutz 13:327-336.

7

Harper, S.S. 1988. Sorption of metribuzin in sur­face and subsurface soils of the Mississip­pi Delta region. Weed Science 36:84-89.

Junnila, S., H. Heinonen-Tanski, L.R. Ervio, P. Laitinen and R. Mutanen. 1994. Phytotox­ic persistence and microbiological effects of flurochloridone in Finnish soils. Weed Research 34:79-88

Krauskopf, B. and I. Wetcholowsky. 1990. Col­laborative study comparing different bio­assay methods to monitor the behaviour of herbicides in the soil. Preliminary re­port, European Weed Research Society, Leverkusen. 3p.

Vouzounis, N.A. and P.G. Americanos. 1992. Ef­fect of temperature and soil moisture on degradation of alachlor, pendimethalin and prometryn. Technical Bulletin 147, Agricultural Research Institute, Nicosia. 5p.

Walker, A. and R. Allen. 1984. Influence of soil and environmental factors on pesticide persistence. Monograph, British Crop Protection Council 27:89-100.

Walker, A., P.A. Brown and P.R. Mathews. 1985. Persistence and phytototoxicity of na­propamide residues in soil. Annals Ap­plied Biology 106:323-333.

8

I

Appendix A. Growth reduction (%) In seasonal crops following field application of flurochloridone and terbutryn* on a clay-loam soil in spnng 1992 and 1993

Sowing time (weeks after application)

Crop Flurochloridone Terbutryn

2 5 8 11 14 17 20 23 2 5 8 11 14 17 20

Cabbage 25 20 0 Carrot 0 0 0 0 Cauliflower 25 20 0 Celery 0 0 0 0 Chard 70 55 40 20 5 0 85 70 30 0 0 Chickpea 0 0 0 0 Cowpea 30 20 15 5 0 15 0 0 Cucumber 100 90 50 20 20 15 0 20 15 0 0 Eggplant 75 60 45 25 20 15 5 0 0 0 French bean 40 20 0 0 20 0 0 Lettuce 100 100 100 75 45 20 15 10 0 0 Marrow 95 85 50 35 25 20 15 0 20 8 0 0 Melon 95 80 45 25 20 15 8 0 30 15 0 0 Okra 0 0 0 0 Onion 100 90 70 25 20 0 0 50 30 20 0 Parsley 0 0 0 0 Peanut 0 0 0 0 Pepper 100 70 30 15 0 0 15 0 0 Purslane 100 90 70 0 0 80 75 0 0 Radish 100 90 70 50 20 25 20 15 15 0 0 Tomato 35 20 0 0 8 0 0 Watermelon 90 80 40 25 15 5 0 20 5 0

* Rates of application : flurochloridone 0.5 kg, terbutryn 1.5 kg/ha - : crop not sown

Appendix B. Growth reduction (%) in seasonal crops following field application of flurochloridone and terbutryn on a clay soil in spring 1992 and 1993

Sowing time (weeks after application)

Crop Flurochloridone Terbutryn

2 5 8 11 14 17 20 23 2 5 8 11 14 17 20

Cabbage 0 a a Carrot a a a a Cauliflower 8 a a Celery a a a a Chard 70 65 40 20 a a 80 70 40 a a Chickpea a a a a Cowpea 30 20 8 a a 15 8 a Cucumber 100 90 40 20 a a a a 40 20 15 a a Eggplant 70 60 40 20 a a a a French bean 40 20 a a 15 15 a Lettuce 100 100 100 60 25 8 a a 8 a Marrow 95 80 50 20 a a a a 30 15 8 a Melon 95 90 40 20 a a a 0 40 15 a a Okra a a a a Onion 100 90 60 20 a a a 50 30 20 a Parsley a 0 0 a Peanut a 0 0 a Pepper 100 70 40 20 a a 30 8 a Purslane 100 100 100 a 90 80 a a Radish 100 100 100 40 20 8 a a 15 a a Tomato 20 15 5 a a a a Watermelon 90 80 40 20 a a a 15 8 a

* Rates of application : flurochloridone 0.75 kg, terbutryn 2.0 kg/ha -: crop not sown

Appendix C. Growth reduction (%) in seasonal crops following field application of flurochloridone and terbutryn* on a clay-loam soil in autumn 1991 and 1992

Sowing time (weeks after application)

Crop Flurochloridone Terbutryn

2 5 8 11 14 17 20 23 26 29 32 35 38 41 2 5 8 11 14 17 20 23 26

Barley Beetroot Broadbean Cabbage Carrot Cauliflower Celery Chard Chickpea Coriander Cowpea Cucumber Eggplant French bean Lettuce Marrow Melon Oat Okra Onion Parsley Pea Peanut Pepper Purslane Radish Ryegrass Spinach Tomato Vetch Watermelon Wheat

100 95 90 90 100 70 60 30 20 15 0 0

100100 80 80 0 0

100100 100 70

90 60 30 30 0 0 0 0

100100 90 90

100100 100 75 0 0

12 0

100100 100 100 100 60 50 25 100100 100 90

0 0

100100 100 90

80 20

80

70

15

70

75

90 20 80

60

70 10

80

60

0

50

70

80 15 70

50

60 0

60

50

0

-

100 -

-

30

50

-

75 15 40

-

20

30

40 0

0 40 50

0 80 60 60

0 25

40 -

80

0

30

30

35

30 20

60 30 30

15

0 15 70 60

15

25

35

15 15

30 20 15

15

15 0

30

12

20

30

0 0

30 0 0

0

15

30

0

20

25

15 0 0

0

0

15

15

15

8

12

-

-

15

15

-

-

-

5 -

-

-

70 100

0 80

0 30

100 0 0

75

100 0 0

30 50 90

0

50

15 60

0 40

0 8

40 0 0

15

90 0 0

20 20 60

0

20

0 50

15

0

40

0

45

5 10 40

12

0 40

0

30

0

0

0 0

25

0

0

0

0

0

0

0

0 0 0 0

0 0

0

0

0

0

0

0

• Rates of application : flurochloridone 05 kg, terbutryn 1 5 kg/ha - : crop not sown

Appendix D. Growth reduction (%) in seasonal crops following field application of flurochloridone and terbutryn* on a clay soil in autumn 1991 and 1992

Sowing time (weeks after application)

Crop

2 5 8 11 14

Flurochloridone

17 20 23 26 29 32 35 38 41 2 5

Terbutryn

8 11 14 17 20 23 26

Barley Beetroot Broadbean Cabbage Carrot Cauliflower Celery Chard Chickpea Coriander Cowpea Cucumber Eggplant French bean Lettuce Marrow Melon Oat Okra Onion Parsley Pea Peanut Pepper Purslane Radish Ryegrass Spinach Tomato Vetch Watermelon Wheat

100100 100 100100 70 40 30 20

100 100 100 0 0

100100 100

100100 90 0 0 0 0

100100 100

100100 100 0 0

12 0

100100 100 100 90 85 100100 100

0 0

100100 100

90 40 15

100

100

90

100

100

100 60

100

90

90 70 25 15 12 0

100 100

100 100

45 20

-

90 70

100 80

100 100 100 60 100 80

80 70

60 0 0

90 60

100 90 0

0

0 - 50 - 60

0 100 100

- 70 70

40 0

75 60

- 70 -

100 95 50 50

0

- 40 70

60

80

35 30

70 40 35

40

0 40 90 60

20

40

60

20 15

40 35 20

20

20 0

40

12

30

40

0 15

40 15 0

8

15

40

0

25

30

0

20 0 0

0

0

25

20

25

20

15

-

-

15

20

-

-

-

8 --

-

90 100

0 60

0 45

100 0 0

90

100 0 0

60 60 95

0

100

50 90

0 30

0 25

90 0 0

50

80 0 0

30 20 90

0

60

15 80

15

8

90

20

40

20 15 45

30

0 80

0

0

85

0

0

0 0

30

8

0

15

0

0

-

0

0

0 0 0 0

0 0

0

0

0

0

0

0

* Rates of application : flurochloridone 0.75 kg, terbutryn 2.0 kg/ha -: crop not sown

Appendix E. Growth reduction (%) in seasonal crops following field application of flurochloridone and terbutryn' on a

Crop

clay-loam soil in winter 1991-92 and 1992-93

---' - ---­ ~~_._-

Sowing time (weeks after application)

--------

Flurochloridone

2 5 8 11 14 17 20 23 26 29 32 2 5

Terbutryn

8 11 14 17 20

Beetroot 50 40 Carrot 0 0 Celery Chard 40 30 Chickpea 0 0 Coriander 0 0 Cowpea 30 20 Cucumber Eggplant -

French bean 30 20 Lettuce -

Marrow Melon Okra Onion 100 100 Parsley 0 0 Pea 0 0 Peanut Pepper Purslane Radish 100 100 Spinach 100 70 Tomato Watermelon

30

35

20 30

100 5

100 30 40

0 100

90

70 80

0 20

20

0 15

5 30 50 0

90 20 30

80

0 50 70 70 70

0 30

0

15

0 20 30

80 15 30

60

25 50 60 40

25

8

15 15

40 5

15

30

15 0

30 20

15

0

0 10

0 0

15

10

0 0

25 0

10

0

0

0

20

0

15 10 5

60 0

60 0 0 0

0

65 0 0

30 50

45 0

60 0 0 0

0

50 0 0

0 45

40

60

10 0

0 10 10 0

40

8

0 25

0 0

25

0 35

8

5 0

30

0 0 0

0

0

15

0

0

0

8 0

* Rates of application : flurochloridone 0.5 kg, terbutryn 1.5 kg/ha -' crop not sown

Appendix F. Growth reduction (%) in seasonal crops following field application of flurochloridone and terbutryn* on a clay soil in winter 1991-92 and 1992-93.

Sowing time (weeks after application)

Crop

2 5 8

Flurochloridone

11 14 17 20 23 26 29 32 2 5

Terbutryn

8 11 14 17 20

Beetroot 30 30 Carrot a a Celery Chard 30 25 Chickpea a a Coriander a a Cowpea 30 20 Cucumber Eggplant -

French bean 30 20 Lettuce -

Marrow Melon Okra Onion 100 100 Parsley a a Pea a a Peanut Pepper -

Purslane Radish 100 100 Spinach 100 60 Tomato Watermelon

15

20

15 70

100 a

100 70 60 a

90

100

80 60 20 50

0

a 20

a 50 70

90 60 30

80

a 80 90 80 70

0 40

15

40 40

80 50 45

65

50 70 60 40

30

5

15 15

50 25 20

35

25 20 30 15

a

a

a a

a a a

15

a a

20 a

a

12 5 a

90 a

90 a a a

a

70 0 a

25 70

80 a

90 a a a

a

60 a a

a 60

60

85

20 a

a 15 20 a

60

a

40 a

15

35

a 60

10

10 a

35

a

a

a

a

a

25

a

a

a

15 a

* Rates of application : flurochloridone 0.75 kg, terbutryn 2.0 kg/ha - . crop not sown

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