Agriculture Reference
In-Depth Information
(54,000 tons) as compared to 1995-1996 (70,000 tons) (Prasada Rao,
2002). In 1996-1997, moist weather due to moderate dew fall with mean
minimum temperature of 20 °C during reproductive phase led to moderate
flowering and enhanced the incidence of Tea Mosquito Bug (TMB) result-
ing in low nut yield. In 1997-1998, low dewfall with slightly higher mean
minimum temperature of 21-22 °C during reproductive phase reduced
flowering with consequent yield losses. Cashew genotypes distinctly vary
in their heat units (day °C) requirement. Early variety 'Anakkayam-1' re-
quires only 1953 day °C for reproductive phase, while late variety 'Mada-
kkathara-2' requires 2483 day °C. Delayed flowering and fruiting in late
varieties is likely to experience moisture stress, which can be managed by
supplemental irrigation.
The mean maximum temperatures of 34.4, 36.1 and 36.2 °C were re-
corded during February 1992-1993, 2003-2004 and 2004-2005 and the
corresponding RH in the afternoon was 33.0, 18.5 and 19.7%, respective-
ly. Lower nut yield obtained during 2003-04 and 2004-05 as compared to
1992-93 was mainly due to drying of flowers. A rise in night temperature
(>20 °C) coupled with fewer dew nights during flowering phase is detri-
mental for cashew flower production. Heavy cloudiness during flowering
phase is detrimental for the opening of hermaphrodite flowers. Continuous
rains without critical dry spells and late winter rains delay the bud break
in cashew. A dry spell of 7 days is usually necessary 30 days prior to the
bud break. Late and extended winter rains reduce the number of bright
sunshine hours invariably which results in delaying of bud break and bet-
ter availability of soil moisture during flowering (December and January).
Incessant rains until November in 1998 delayed the bud break. The delay
in bud break was prominent in early varieties. In late varieties, bud break
was normal, because the required dry spell of 7 days was met 22-26 days
before bud breaking (Table 6.7) (Prasada Rao et al., 2001).
TABLE 6.7
Time of Bud Break of Test Varieties at RARS, Pilicode from 1995-1996 to
1998-1999
Time of bud break (25%) of test varieties
Variety
1995-1996
1996-1997
1997-1998
1998-1999
Mean
Anakkayam-1
26 September
30 October
23 October
3 November
21October
Madakkatha-
ra-1
22 September
2 November
5 October
3 November
16 October
