Madras Agric. J. 92 (10-12) : 715 - 717 October-December - 2005

715

RESEARCH NOTES

SEASONAL INFLUENCE ON NUT YIELD AND BARRENNUT PRODUCTION IN TALL AND HYBRID COCONUT S. RAJARATHINAM, S. VINCENT and P. JAYAKUMAR Coconut Research Station - Veppankulam

The barren nut production is common in coconut palms especially in those palms grown under rainfed condition without manuring. The barren nut production accounts for not less than three per cent of total annual gross yield (Gangolly and Nambiar, 1953). The types of barren nut differed based on certain morphological features. Menon and Pandalai (1958) classified the barrennuts into five distinct types. Among the five types of barren nut, nut with cracking is the most frequently occurring one. The production of barren nut fluctuates from year to year and within the year it was found to be high during the peak bearing period and low during the lean period. The preliminary work undertaken by Gangolly -and Nambiar (1953) showed that the production of barren nut was frequently observed in trees yielding an average of 40 to 60 nuts. However, very little information is available on seasonal variation on nut yield and barren nut production with reference to rainfall and temperature and hence the present study was under taken. East Cost Tall (ECT) and VHC 2 (ECT x MYD) were selected for the study at Coconut Research Station, Veppaankulam. The data were collected from 120 palms each in ECT and VHC 2 for four years from 1997 to 2000. The production of barren nuts was studied monthwise and the percentage worked out based on the number of good nuts produced. The meteorological data on rainfall as well as maximum and minimum temperature for previous five years (from 1996 to 2000) were also utilized to relate the nut yield with barren nuts. The variation in the yield of nuts during the four years from 1997-2000 was presented in Table 1. It was evident that the number of nuts produced by the hybrid was considerably higher when compared to ECT in all the four seasons in all the four years studied. Among the four seasons, south west monsoon period recorded higher nut yield in both

ECT and hybrid while during winter, the yield level was reduced. The production of barren nut was higher in hybrid than in ECT. The hybrids produced almost double the rate of barren nut than ECT. Higher number of barren nuts were produced during south west monsoon coinciding with the peak bearing season (Table 2). In spite of higher number of barren nuts, the hybrids registered higher yield than ECT. The effect of rainfall and temperature on barren nut production showed that the barrenness was considerably lower when the rainfall is high. When highest rainfall of 460.8 mm was received during winter season, less barren nuts were produced irrespective of the genotypes. ECT and VHC 2 produced 74 and 292 barren nuts respectively during winter which was the lowest in the four seasons of the year. The rainfall received during the previous years was found to be effective in reducing the number of barren nuts of the current year. However the effect of temperature on barren nut production was not determinable. It was clear that the hybrid was found to be superior in nut yield production in all the seasons of the year (Table 3). Highest nut yield was recorded during South West Monsoon season (May - July). Correlation studies were also made between the rainfall and yield as well as rainfall and barren nuts in ECT and VHC 2 (Table 4). A significant negative correlation found to exist between the rainfall and the number of barren nuts produced. The rainfall received during the previous year had reduced the number of barren nuts significantly during subsequent years. A significant positive correlation existed between nut yield and barren nut production in both ECT and hybrid. However the reduction in barren nuts due to higher rainfall in the previous year did not have any effect in increasing the nut yield.

S. RAJARATHINAM, S. VINCENT and P. JAYAKUMAR

716 This might be due to the hinderence to pollination by washing of pollens by heavy rainfall during the period. Davis and Ghosh (1982) reported that during the periods of low precipitation, the emergence of large number of spadice occur and successful pollination and fertilization was ensured. This was further emphasized by Abeywardena (1968). The important factor for higher production of nut was better distribution of rainfall over a longer period of years as reported by Patel et al. (1936). Vijayaraghavan et al. (1981) reported that moderate levels of rainfall (around 1000 mm) and relatively lower minimum temperature (around 20°C) were conducive for realising higher yields in coconut.

development of female flowers which were fertilized already and thus reduced the number of barren nuts. REFERENCES Abeywardena, V. (1968). Fore casting coconut crops using rainfall data. Third session of the FAO technical working party on coconut production, protection and processing, Jagiakarta; Indonesia PL: CNP 68/29. Davis, T.A. and Ghosh, S.S. (1982). Effect of rainfall on production of coconut. Indian Coconut J. 8 : 3-5. Gangolly, S.R. and Nambiar, M.C. (1953). Studies on the occurrence of barrennuts in coconut Indian Coconut J. 7 : 5-19. Menon, K.P.V. and Pandalai, K.M. (1958). The coconut palm. A monograph. Indian Central Coconut Committee. Ernakulam. pp. 78-80. Patel, J.S. and Anandan, A.P. (1936). Rainfall and yield of coconut. The Madras Agric. J. 24:514. Vijayaraghavan, H. Raveendran, T.S. and Ramanathan, T. (1986). Influence of weather factors of the yield of rainfed coconut. Indian Coconut J. 18: 7-9.

It was concluded that the production of barren nuts was highly and significantly influenced by the rainfall of a particular year. Though the barren nut production was reduced by the rainfall, the number of nuts produced was not significantly increased. Probably the rainfall was not distributed over a longer period of days. Higher rainfall would have affected the pollination of current female flowers causing eventual shedding. At the same time, the higher rainfall would have helped in the Table l.

Yield of nuts in East Coast Tall (ECT) and hybrid (VHC2) coconuts in different seasons(Mean of 120 plants)

SEASONS ECT

1997 VHC2

1998 ECT VHC2

1999 ECT VHC2

2000 ECT VHC2

Mean ECT VHC2

South West Monsoon 26.6

37.8

27.1

36.2

30.2

46.6

23.5

36.7

26.9

39.3

North East Monsoon 19.1

26.1

22.2

37.3

27.6

36.2

26.1

31.8

23.8

32.9

Winter

12.8

22.3

16.5

25.4

16.8

34.8

14.1

20.6

15.1

25.8

Summer

17.0

37.8

18.8

28.3

25.1

30.4

15.0

34.5

19.0

32.8

Table2.

Yield of barren nuts in East Coast Tall (E7CT) and hybrid (VHC2) coconuts in different seasons (Mean of 120 plants)

SEASONS

East Coast Tall(ECT)

hybrid (VHC2)

Nut yield

barren nuts Percentage barren nuts

Nut yield nuts

barren

Percentage

South West Monsoon

3252

268

8.25

4728

700

14.81

North East Monsoon

2880

106

3.68

4048

323

7.98

Winter

1704

74

4.34

3240

292

9.01

Summer

2200

169

3936

494

12.55

717

SEASONAL INFLUENCE ON NUT YIELD AND BARRENNUT PRODUCTION IN TALL AND HYBRID COCONUT

Table 3.

Effect of rainfall and temperature on nut yield of East Coast Tall(ECT) and hybrid (VHC2) different seasons (Mean of 120 plants)

SEASONS

Mean Rainfall (mm)

Mean Temp.(°C) No. of Max. Min. rainy days

ECT Nut barren yield nuts

hybrid (VHC2) Nut Barren yield nuts

South West Monsoon

128.0

7.3

32.4

25.5

3252

268

4728

700

North East Monsoon

319.7

16.3

32.6

25.0

2880

106

4048

323

Winter

460.8

19.1

29.3

21.9

1704

74

3240

292

Summer

327.8

6.6

31.6

23.6

2280

169

3936

494

Table 4.

Correlation co- efficient between Rainfall and Nut yield and barenuts of East Coast Tall(ECT) and hybrid (VHC2 coconuts

Parameter

‘r’ value East Coast Tall(ECT)

hybrid (VHC2)

Rainfall Vs Nut yield

-0.3975

-0.5447

Rainfall Vs barren nuts

-0.6220*

-0.6871*

Nut yield Vs barreness

-0.5799*

-0.6523*