Quantification of heat units for chickpea under coastal environment of Andhra Pradesh

Chickpea (Cicerarietinum) commonly known as gram and Bengal gram is grown in India as winter season (rabi) crop and it requires cool and dry weather for optimum growth. Chickpea being a crop of low input requirement replaced the rice cultivation in some coastal tracts of Andhra Pradesh. The concept of thermal use efficiency has been used by several workers to compare the performance of different varieties or of several dates done elsewhere (Rajput et al., 1987; Rao et al., 1999; Aggarwal et al., 1999) but, it has not hitherto been reported from Andhra Pradesh.

Chickpea (Cicerarietinum) commonly known as gram and Bengal gram is grown in India as winter season (rabi) crop and it requires cool and dry weather for optimum growth. Chickpea being a crop of low input requirement replaced the rice cultivation in some coastal tracts of Andhra Pradesh. The concept of thermal use efficiency has been used by several workers to compare the performance of different varieties or of several dates done elsewhere (Rajput et al., 1987;Rao et al., 1999;Aggarwal et al., 1999) but, it has not hitherto been reported from Andhra Pradesh.
A field experiment was conducted at Agricultural College Farm, Bapatla (A.P) during rabi season of 2007-08. The soil (0-30 cm) of the experimental site is black clay loam in texture with pH of 7.4. The weather parameters were recorded at the meteorological unit. The experiment was laid out in split plot design with 12 treatment combinations comprising of four sowing dates (November 8 th , November 18 th , November 28 th and December 8 th ) and three cultivars (KAK-2, JG-11 andAnnegiri) with three replications. A uniform dose of 20 kg N + 50 kg P 2 O 5 was suppliedas basal through urea and single super phosphate.
The growing degree days (GDD), was calculated using base temperature of 5 0 C (Nuttonson, 1955), Heat use efficiency (HUE), which is a measure of amount of dry matter or grain yield produced per unit of GDD, was worked out as per procedures reported by Sahu et al. (2007).
The results revealed that the crop sown on 18 th November took 118 days for KAK-2, 111 days for JG-11 and 112 days for Annegiri from sowing to maturity, and it reduced under both early and delayed sowings. The accumulated growing degree days from sowing to maturity varied from 1979 to 2247 0 C d (Table 1) with different dates of sowing, maximum under second date of sowing and minimum under fourth date of sowing. GDD requirement was high for KAK-2 followed by Annegiri and low for JG-11.
The amount of total drymatter produced by the crop was maximum under 18 th November sowing (3019 kg ha -1 ) followed by 8 th November and minimum under 8 th December sowing (1828 kg ha -1 ). In both the earlier and later sown crops, the amount of total drymatter produced by the crop decline to an extent of 10.4 percent (8 th November) to 39.4 percent (8 th December). The amount of total drymatter produced by three varieties were in the order of JG-11 > KAK-2 >Annegiri.
The heat use efficiency was high for second sowing. It was low for November 28 th crop upto 45 days after emergence and later 8 th December sown crop recorded the lowest value. The heat use efficiency was maximum for 18 th November sown crop (1.567), followed by 8 th November (1.307) and minimum was with December 8 th (0.851). The increase in heat use efficiency was maximum at 45 to 60 days after emergence for November 8 th sown crop, 30 to 45 days after emergence for 18 th November sown crop, 15 to 30 days after emergence for November 28 th and December 8 th sown crop. A varietal difference was significant at all stages of crop growth. It was higher in KAK-2 upto 45days after emergence, JG-11 showed the highest. It was lower in Annegiri at all stages of crop growth (Table -2).
The correlation analysis between yield and phenophase wise heat units revealed that yield of KAK-2 was positively and significantly correlated (r=0.97*) with GDD during podding stage. In JG -11, yield was negatively significantly correlated (r=-0.99*) with GDD during vegetative stage was observed.