Effect of irrigation on reproductive efficiency of bunch and spreading types of groundnut ( Arachis hypogaea L.)

V. S. Bhatia, S. C. Bhargava, S. K. Sinha
1984 Journal of Agricultural Science  
Groundnuts are mostly grown during the rainy season (kharif) in India. Most of the cultivation is without irrigation. Consequently the crop experiences water deficits of different intensities and durations, depending upon the rainfall distribution. Yields are poor under such conditions. In other leguminous species irrigation at flowering usually improves yield, if the pod development period coincides with a break in rainfall or water deficit (Khanna-Chopra, Koundal & Sinha, 1980) . Thus, an
more » ... rstanding of reproductive behaviour and reproductive efficiency could be helpful in adjusting planting to coincide with favourable agroclimatic conditions. Alternatively, this understanding could help in scheduling irrigation. MATERIALS AND METHODS Groundnut (Arachis hypogaealL.) cvs J-ll and M-13, representing bunch and spreading types respectively, were planted on 3 July 1981 in the field. The plot size was 4 x 4 m, rows were 50 cm apart and there were three plants per metre of row length. Fertilizer (20 kg N, 40 kg P and 20 kg K/ha) was given at the time of sowing. There were three blocks of four plots each, and the plots were randomized to the four combinations of two varieties and two irrigation treatments. No irrigation was given till the plants started flowering. Subsequently, two plots in each block were irrigated during the 4th, 6th and 8th weeks after anthesis of the first flower. Data on rainfall and relative humidity were obtained from the Meteorology Laboratory of the Water Technology Centre. A daily record of opened flowers was maintained to establish the frequency of flowering and the absolute number of flowers per plant. The number of pegs (gynophores) formed per plant was recorded bimonthly. Pollen germination One of the factors responsible for the poor setting of pods could be sterility of pollen grains caused by water deficit. To study pollen germination, flowers were collected between 07.00 and 07.30 h from the irrigated and unirrigated plots. In vitro germination of pollen grains was studied in a medium containing 12-5% sucrose and 0-01 % boric acid at 25 °C (Vasil, 1964) . After 4 h of incubation, total and germinated pollen grains were counted under a microscope to calculate their germination percentage. The observations on pollen germination were made three times a week and the mean value of the three was taken as an average for the week. RESULTS Flowering behaviour Flowering started 24 and 30 days after planting in J-ll and M-13 respectively. For the first 4 weeks there was no difference in the number of flowers per plant between the cultivars with or without irrigation. Between the 4th and 7th weeks fewer flowers were produced in both cultivars in unirrigated plants compared with irrigated plants. However, following rainfall during the 7th and 9th weeks, more flowers were produced in M-13 but few in J-ll under unirrigated than under irrigated treatment in the subsequent period (Figs la and 2 a) . The total number of flowers produced during the whole flowering period in J-ll were 392 and 346 under irrigated and unirrigated treatments, respectively. The corresponding numbers in M-13 were 406 and 407 respectively (Table 1) . Thus, the total number of flowers produced during the whole flowering period was reduced by 12% in the unirrigated treatment in J-ll. There was no difference in the total number of flowers in M-13 produced under irrigated and unirrigated conditions. Ac-
doi:10.1017/s002185960004288x fatcat:obu4lusugjgoxpkcidet4pqtza