of grain moisture reductions in situ; (2) on the moisture content of grain

-India" J. Pia"t PlJy$lol., Vol.

,

.

..

r

_I

XXIX No.1 pp. 1:13 (Marcb 1986)

PRE-HARVEST PARAQUAT SPRAY fOR GRAIN DRYING IN RICH

B. VENKATESWARLU', S. PADMAJA RA02, V.T. GAlBHIYE', AND N. AGNIHOTRI·

Directorate of Rice Research. Hyderabad

SUMMARY

Grain moisture content was reduced to 17 percent by 4 and 6 days

after spraying paraquat (0.1%) in dry and wet seasons respectively. Spraying 25 days after flowering (DAF) was found to be more effective.

Varieties Jaya and Prakasb sbowed slow reduction in moisture while Rasi

and Mabsuri were fast. The moisture content of grain stored in gunny bags immediately after spraying also reduced tbe moisture content considerably by tbe 4th and 6tb day. The residue content of grain was witbin tolerance limits. The germinabUity, filled grain proportion. kemel colour, flavour and grain yield were not affected.

INTRODUCfION

Rice being a major monsoon crop faces unpredictable.cyclones or typhoons at harvest and the weather is wet due to mist and high relative humidity during the ripening period. This situation exposes the grain to the problems of non­ uniform drying and intermittent wetting leading to untimely harvest due to lot of green material. Further. due to lack of drying facilities like drying floors and dryers in the third world countries, farmers are compelled to dry in the field itself: Consequently -the losses are huge particularly in milling as the paddy sheaves are amenable to rain, dew, and unpredictable cyclonic weather in all the coastal areas of Asia and Africa. Even in advanced countries, occurrence of similar conditions were posing problems to harvesting and threshing equipment like combines, harvesters and threshers.

Therefore. different types of desiccants were tested (Hinkle. 1952 and

1953; Smith et al., 1959; Williams, 1952; Ramanujam et al., 1979; Bastin. 1978,

1980) as preharvest methods of drying paddy crop to facilitate mainly timely harvest, and secondly to make the harvesting equipment more efficient. In the

I and I Senior and Junior Physiologists, respectively. at the Directorate

or

Rice Research.

Hyderabad.

J .and. Junior and Senior €hemists. respectively, at the Indian Agricultural Researcb Institute,

·

.

2 B. VENKATESWARLU BT AL.

present studies efforts are made to assess the influence of desiccants (I) on the nature of grain moisture reductions in situ; (2) on the moisture content of grain in stored conditions; (3) on discoloration, off-flavour. germinability and grain yields; and (4) on the residues in grain and straw.

MATERIALS AND MEmODS

The Mahsuri variety was grown in Kharif (wet) season (1980) adopting the standard cultural praCtices. The crop was managed to 60 kg N, 30 kg P20S and 30 kg K20/ha in all the experiments. At 25 days after flowering (DAF), the

crop Was sprayed with diquat (6, 7-dihydrol-dipyrida (I, 2-a: 2', l'c)

pyrazinadium ion (Reglone) at 0.05 and 0.1 %. Paraquat (I-1'-dimethyl-4-4'­ bipyridinium ion (dichloride salt-gramoxone) at 0.5 and 0.1%, and common salt at 5 a.nd 10.0% concentrations.

The study was repeated in rabi (dry) season (1981) with Rasi (early) and Prakash (medium duration) varieties. Only paraquat was sprayed at 0.05,0.1, 0.2 and 0.4% concentrations both at 20 and 25 DAF. The study was further repeated with Jaya and Mahsuri varieties in Kharif 1981 and Kharif 1982, and with Rasi and Prakash in rabi, 1982. Paraquat was sprayed at 0.1 % concentra­ tion at 20 and 25 DAF. Observations were recorded on grain moisture content at 2-day intervals till 8 days after spraying (DAS) and on germination percent, cbanges in colour of spikelets, moisture content of grain stored in gunny bags, test weight of grains and grain yield.

Multi-site study

The study was also organised at Calcutta, Cuttack, Karjat, Maruteru,

Patna and Titabar, besides at Hyderabad, mainly restricting to paraquat at 0.1 %

concentration but using the same varieties in both Kharif and raro seasons. Observations on grain moisture content both in situ and gunny bag stored condi­ tions. germinability and grain yield were recorded.

The residue content of paraquat in straw and grain was determined at the Indian Agricultural Research Institute, New Delhi, from samples collected at all the centres by adopting the coloro-metric procedure of Calderbank and Yuen (965).

RESULTS AND DISCUSSIONS

i

PARAQUAT IN ~ICB GRAIN DRYING 3

culady in cereals like rice which results in breakage of kernels, deterioration in keeping quality, mould development and fetch lower price if not dried adequatly.

Earlier studies (Hinkle, 1952, Williams, 1952; Smith et aI.. 1959; Eastin, 1978.

~. _{1980; Ramanujam et aI., 1979) examined desiccation of straw and grain and were}

mainly oriented to assess the amount of time taken for drying rather, than on the

nature of drying and the amount of moisture eliminated from the grain. In the

current studies it was found that grain moisture content reduced gradually to

around 22 to 16% by 6th DAS. In kharif 1980 experiment (Fig.

0,

paraquat

Fig." Infiuence of desiccants 00 grain moisture content of Mahsuri when sprayed at

25 DAF (Kharif 1980).

and diquat were more effective than the common salt which showed 20-22% moisture at 6 and 8 DAS also. Common salt has certain limitations like its deposits on grain create problems in the roUers during milling and would effect germination of the succeeding pulse crops besides being an inefficient drying

agent. Paraquat reduced moisture from 33% to 18 and 16% in 6 days which is

40

35

30

25

20

15

10

5

• -Control

o -

Commori salt - 5%

.& - Common salt - 10%

V - Diquat - 0.05%

X - Diquat - 0.10%

0 - Paraquat

• - Paraquat

- 0.05%

-

0.'

%

o

2 4 _{6 8}

B. VENKATESWARLU ET AL.

acceptable even for immediate marketability, while it decreased to around 13 to

14% by 8th DAS wluch is preferred for storage purposes. Diquat was only next to paraquat.

Groin moisture (Ok)

30

20

10

30

20

10

Sprayed 20 OAF

Control

0.1 }

0.2 Paraquat

0.3 0.4

o

2 4 6 8

Days after spraying

Sprayed 25 OAF

Control

0.1 }

0,2 Paraquat

0,3

0.4

o

2 4 6 8

Fig. 2. Influence or paraquat at different concentrations (%) on grain moisture content of Rasi, rabi 1981,

PARAQUAT IN R,ICB GR.A1N DRYING

s

In rabi (dry season) 1981, paraquate sprayed at 25 OAF was more

effective as the moisture content reached around 12% by 6th OAS. Apparently

dry weather conditions (high temperatures 33-37°C) might have further catalysed the dehydration process. Even 0.1 % concentration was equally effective as the

difference was negligible considering the moisture levels required for

marketability and storage.

In kharif 1981 and rabi 1982, where paraquat was used at 0.1% but sprayed at 20 and 25 OAF (Fig. 2), the reduction in moisture content was drastic when sprayed at 25 OAF in both 1aya and Prakash varieties. In 1aya at 4th OAS,

the moisture percent was around 26% in the treatment at 20 OAF while it ~as

at 20% in 25 DAF treatment. The desired effect is reached by 6th day when

sprayed in kharif. The advantage of spraying at 25 OAF was clear which wa~

more drastic in rabi than in kharif(Mahsuri variety).

The reduction in moisture content during kharif 1980 was from 3 to 10%, while in rabi 1981 from 5 to 7% in Rasi, and 8 to 13% in Prakash when sprayed at 20 OAF. The reduction was 5 to 7 and 7 to 11% in Rasi and Prakash respectively when sprayed at25 OAF. In kharif 1981 and 1982, the reduction in moisture content ranged from 5 to 8 and 2 to 11 % when sprayed a't 20 and 25 OAF respectively. Although the degree of reduction was less when sprayed at 25 OAF. it reached the desired level 2 days earlier and to even to very lower

levels. Further, 1aya and Prakash showed high grain moisture levels

intrinsically while Rasi and Mahsuri lower levels.

The earlier studies (Eastin, 1978, 1980) showed a maximum reduction of 4.4 to 7.0% which was determined only at the end of harvest. Therefore,

in thos~ studies the nature of moisture loss, the effect of the season, the basic

varietal differences in retaining more moisture and the magnitude of the water loss were not examined.

The study was also organised at 7 important locations in India which showed (Table 1) that the grain moisture content attained marketable levels at 4 and 5 centres by 4th day when sprayed at 20 and 25 OAF respectively. However, the moisture content reduced fast when sprayed at 25 OAF and at 2 locations it touched the desired level even on 2nd day. These observations strengthen the point that 4 to 6 days time is adequate enough for manifesting the desired effect on the grain moisture content.

6 B. VBNKATflSWARLU ET AL.

Gram moisture (%)

(i . .

60

30

20

10

40

30

20

·10

20

OAF}

ContrOl

25

OAF

20

OAF}

Paraquat 25 OAF

Khaof 1981 Variety: Jaya

o

2 4 6 8

Days offer sprayino

Rabi 1982

Variety Prakash

20

OAF}

Control

25

OAF

20

OAF}

. Paraquat

25 OAF

o

Days after sprayrng

1

,

'., ! \

.

"'.,.' ... "fable I : Influence of paraquat (0.1 'Yo) on moisture content of grain ('Yo) sprayed at 20 and 25 DAF (Mahsuri) at different locations in India. Kharif. 1982 Time of spraying DAS

Hyderabad S

C Calcutta Cuttack

---_._­

S C S C Karjat

---­

S C

Maruteru S

C Patna Titabar

---­

S C S C Mean

--­

S C

~ ~ >

20

DAF

0 2 4 6

31.0 26.6 24.4 17.2

31.0 27.2 26.1 22.2

30.0 25.2 16.7 15.1

30.3 28.0 26.0 24.6

22.5 19.1 IS.0 14.6 22.5 21.7 20.7 17.7

24.S 22.1 17.4 16.7

26.0 22.6 21.3 20.9

22.3 21.1 17.7 14.S

22.4 21.7 19.0 IS.4

32.5 2S.3 25.8 25.1

32.3 30.0 28.2 26.4

27.2 23.7 20.0 17.3

27.4 25.2 23.6 21.7

~

.-j .... Z

~

8 13:0 20.1 21.2 16.3 20.7 14.2 17.5 24.1 25.0 16.9 17.4

~

'Ii 2S DAF

0 2 4

24.6 19.6 17.4

24.6 21.1 20.5

26.S 20.3 17.S

26.4 23.8 22.0

19.3 15.6 14.3

19.0 17.3 1S.7

24.2 _20.S 14.8

28.4 23.4 20.2

20.5 19.3 17.4

21.1 20.1 19.6

22.1 19.4 IS.7

22.2 20.4 19.1

26.3 24.3 21.6

32.5 31.5 26.8

23.4 19.9 17.4

24.9 22.5 20.6

8 B. VENKAT,ESWARLU ET AL.

Drying in stored conditions

The wet and the threatening weather of the monsoon season could be

overcome relatively if the grain could dry in gunny bags wh~n stored after

immediate threshing. Interestingly such an. effort emerged successful and effective as could be seen in the current studies (Table II). The paraquat was sprayed at two concentrations (0.1 and 0.2%) in rabi 1982, and at 20 and 25 OAF in kharif 1982, and the grain immediately threshed and stored in gunny bags. The reducation in moisture content was apparent in the grain stored in gunny bags on the lines of in situ drying and sometimes even better than in situ drying. The fall was rapid in dry season as by 4th OAS it touched 12.4 and 8.4% in in situ and stored conditions respectively. Again it reduced to the desired levels when sprayed 25 OAF by 4th day while up to 6th day when sprayed at 20 OAF. Jaya showed slow reduction stretching up to 6 to 8th day

which appears to be due to its inherent high moisture retention capacity. Similar

study conducted at 3 more locations viz Calcutta, Maruteru and Patna, besides Hyderabad have conclusively shown that there is dependable reduction in moisture content of grain in gunny bag stored conditions (Table In). These findings have greater practical implications and particularly paraquat must be acting even in deionized conditions persistently.

Grain yield

Paraquat spraying did not affect grain yield in all the experiments except

in kharif 1982, where control had given relatively hi~er yields (Table IV). Even

tn the multi loCation trials conducted at 7 locations, !the yields were not effected except at Maruteru. The germinability although initially effected but improved gradually restoring to normalcy. The filled grain proportion, test weight of grains, grain or kernel colour and the flavour of grains were not affected nor off flavour felt; These findings are in conformity with the observations of the

. carlier workers (Eastin, 1978, 1980; Ramanujam et ali, 1979).

I

However. as paraquat is known for its poisonous nature, its higher residues are harmful. The current studies indicated that paraquat residue content showed

lower levels in grain samples sprayed at 20 and 25.Di\F.

It

touched a maximum

,,-~~

.---,..

...

.---....-...-..,t'-.

Ta\>le

II:

Influence

of

paraquat

on

moisture

content

of

grain

(%)

in

situ

and

stored

in

sunny

bags

during

rabi

and

kharif,

1982.

at

Hyderabad

Days

arter

storage

o

days

---­

2

days

4

days

6

days

8

days

---­

Particulars

Concentra­ tlon

(%)

Grain in

situ

Grain in

situ

Stored

in

gunny bags

Grain _in situ

Stored

in

gunny bagl

Grain in

situ

Stored

in

gunny _bags

Grain in

situ

Stored in

gunny _bags

~

~

I I. I

Rabi

1982

Prakash

Kharif

1982

20

DA.F _{Mahsuri laya}

0.10 0.20

Control

0.10

Control 0.10 Control

23.0 23.S 23.3 _{31.0 31.0 30.5 30.0}

20.7 16.6 22.6 27.2 29.6 28.4 29.2

20.6 16.5 22.S _{26.6 29.0} 26.3 28.8

12.4 11.5 22.1 24.4 28.S 26.0 28.4

8.4 8.8 _19.4

20.7 26.4 23.2 _27.7

10.5 8.0 18.6 20.3 26.2 24.4 26.0

8.3 7.2 _{16.8 16.0}

24.0 22.0 26.4

8.5 8.3 _{14.9 19.9 23.0 22.8}

25.2

6.7 6.4 _{14.1 15.0 19.8 19.0}

23.4

~

2

'e! Q ~

2

~ 10(

~

""

25

DA.F _{Mabsuri laya}

0.10

Control 0.10 Control

24.6· 25.0 27.2 27.0

21.1 24.0 27.1 27.0

19.6 23.4 26.6 26.2

21.0 22.8 26.1 26.5

17.4 22.0 21.5 24.0

19.3 22.2 23.8 25.8

l!I.2 21.2 19.1 23.6

16.4 20.1 20.4 24.6

13.3 19.6 17.0 21.8

~

0

Table III: Inftuence of paraquat (0.1 %) on moisture content (%) of grain stored in gunny bags at different locations, Kharif 1982 Hyderabad Calcutta Maruteru Patna Moan Particulars DAS

---­

S C S C S C S C S C 20 DAP Jaya 0 310 31.0 20.0 21.4 20.0 21.4 18.8 19.1 22.0 23.2 2 26.3 21.4 16.5 19.3 18.4 21.3 IS.S 18.4 19.6 21.8

I

!:II 4 23.2 26.0 14.0 18.1 17.7 19.9 14.7 18.0 18.7 20.4 6 22.0 24.4 14.0 17.2 17.6 19.1 13.9 16.7 17.4 20.0 Mahsuri 0 31.0 31.0 20.3 21.2 21.0 22.1 19.0 19.3 19.3 21.8 2 26.6 27.2 16.3 19.6 16.7 20.6 15.0 17.0 18.0 20.9 4 20.7 24.,4 13.7 17.6 16.9 19.6 14.8 16.2 16.2 19.4 6 16.0 20.3 13.0

15.'

16.3 18.8 14.2 1S.6 14.7 17.4

'~ CI

12 B. VENKATESWARLU ET.~L.

Table V: Residues of paraquat (ppm) in paddy grain and straw when sprayed at 20 and 25 DAF but analyzed after harvest, Kharif 1982

Sprayed 20 DAF Sprayed 25 DAP

Location Variety

Grain Straw Grain Straw

Hyderabad Jaya 3.64 14.30 2.98 8'36

(AP) Mahsuri 4.56 13.70 5.25 9.33

CuttaCk (Orissa) Mahsuri 2.60 10.50 2.27 9.73

Calcutta (W.B) Jaya 1.23 3.25 0.55

Mahsuri 5.43 7.S3 3.87 6.73

. Karjat (Maharastra) Jaya 3.98 7.03 2.98 4.80

Mahsuri 2.20 1.76 2.15 083

Maruteru (A.P.) Jaya 1.90 13.66 2.33 11.50

Mahsuri· 2.57 ]0.60 2.63 12.86·

Titabar (Assam) Jaya 1.33 1.38 1.22 Q.96

Mansuri 1.25 1.90 1.15 1.10

while samples from Cuttack just touched 10.5 ppm and the rest of the centres showed lower levels. Singh and Agnihotri (1981) reported that the residues are below the tolerance limit in different fractions of paddy as the contents varied from 1.6 to 7.6 ppm. They stated that par boiHng had further reduced the residues. Again, Funderburk, Negi and Lawrence (1966) also stated that there was considerable photochemical decomposition of diquat and paraquat. These findings indicate that residues are not likely to pose serious problems. Further. as rough rice (paddy) is milled and washed before raw cooking, this process itself reduces the content.

Therefore, paraquat emerges as a potential chemical for monitoring grain· moisture content in rice and holds greater promise for rescuing from enersy crisis faced due to the use of dryers.

ACKNOWLEDGEMENTS