Abstract: Number of plant emergence/m2 and 1000 grain weight were significantly affected by seed rates. The number of plants emerged per unit area increased while 1000 grain weight decreased with increase in seed rates. The effect of seed rates on productive tillers/m2, seed grade recovery and grain yield ha–1 were not significant. Emergence/m2, productive tillers/m2, 1000 grain weight, seed grade recovery and grain yield ha–1 significantly decreased as the sowing was delayed from the first week of November till the third week of December. In overall, November sowing was superior to the December sowing.
Introduction
Seed rates at superoptimal level impose stress of the available moisture, nutrients, light and temperature because, competation between individual plant for these resourses increases and hence adversely affect crop yield while crop seeded at suboptimal level usually have lower yield because of substandard plant population. Khan et al. (1970) concluded that a seed rate more than 80 kg ha–1 for Maxipak is westeful variety of wheat is not recommended because 80 kg ha–1 produced significantly higher yield than 100 or 120 kg ha–1 (Khan et al., 1977). Nazir et al. (1987) reported greater number of productive tiller and grain yield when the wheat was seeded at the rate of 100 kg ha–1 as compared with lower seed rates of 40, 60 and 80 kg ha–1. Mujahid (1972) obtained more productive tiller and compared with 60, 80 and 100 kg ha–1 but 1000 the grain weight reduced with increase in seed rate. Ahmad et al. (1995) observed decrease in seed weight with increase in seed rate from 40 to 120 kg ha–1. Seed size increases only when the plant densities are too low for optimum yield (McGraw et al., 1986) and seed size decreases only at very high plant density (Kromer and Gross, 1987).
Sowing times also plays an important role in the establishment of any crop and its production. Wheat sown in October is more profitable as compared with December sowing because of more productive tiller (Ishag and Taha, 1974; Khan and Salim, 1986). Mid November sowing is better than December because of greater number of spike/m2, heavier grain and grain yield (Razzaq et al., 1986; Zeb et al., 1987). December sowing produced lower grain yield of than November sowing (Waraich et al., 1982; Ahmad et al., 1992).
Materials and Methods
The was conducted at Malakhander Research Farm, NWFP. Agricultural University Peshawar during the crop season, 1997-1998. Wheat variety Bakthwar-92 was sown on November 1st ,10th, 20th, 30th and December 10th and 20th using four seed rates viz. 62, 74, 86 and 99 kg ha–1. The experiment was laid out in RCS design with split plot arrangement having four replications. Net sub-plot size of 1.8×5 meters having 6 rows of 30 cm apart used. A basal dose of 123 kg N/ha and 60 kg P/ha was used. All the Phosphorus and half of the nitrogen was applied at the time of sowing and remaining nitrogen was applied with the first irrigation. Data was recorded on emergence/m2, productive tiller/m2, 1000 grain weight, seed grade recovery and grain yield kg ha–1. For calculating seed grade recovery Round Commercial Stainer number 8/64 was used to seperate seed into different sizes i.e. (a). Plump grain(upper side one and (b). shrivelled grain (seived side).
Results and Discussion
Sowing dates and seed rates had significant effect on emergence/m2 (Table 1). The high number of 129 and 124 seedling were emerged in plots sown on 10th Nov. and 1st Nov., while lowest number of seedling/m2 (65) were recorded from late December sowing. Reduction in emergence/m2 with delay in sowing from Nov. to Dec. may be due to the fall in temperature from Nov. to Dec. Waraich et al. (1982) found significantly higher emergence/m2 when sowing was done on 26th Nov. as compared with those sown earlier or later than 26th Nov. Various seed rates had significant effect on emergenct/m2 as highest number of 106.67/m2 seedling emerged in plots seeded with 99 kg ha–1 while lowest (91.54) seedling were emerged when a seed rate of 62 kg ha–I was used. The higher number of seedling/m2 at high seed rates is mainly due to the more number of seed sown per unit area. Significantly higher seedling/m2 at the higher seed rate of 150 kg ha–1 as compared with 100 and 50 kg ha–1 have been reported by Ayaz et al. (1997). The effect of sowing dates was significant on number of productive tillers/m2 while seed rates had no significant effect on tiller production (Table 2). Significantly higher (432.64) productive tiller/m2 (433) were recorded in plots sown on 1st Nov., while lowest tillers of 243.63/m2 were noted in plots sown on 20th Dec. These results may be attributed to the favourable conditions (temperature etc.) which helped in establishing good crop stand by the earlier sowing. Highest tiller/m2 has been reported by Razzaq et al. (1986) from the plot sown on 15th Nov.and were at par with 31 Oct. in their study.
Data pertaining to 1000 grain weight was significantly effected both by sowing dates and seed rates (Table 3). Plots sown in Nov. (between 1st Nov. and 30th Nov.) had significantly higher 1000 grain weight ranging from 28.78 to 30.16 g as compared with those sown in Dec. (10-20th Dec.). These results are in agreement with those reported by Razzaq et al. (1986) who found significantly heavier grain when wheat was sown upto 30th Nov. December sown plots have lower grain weight in their study. Zeb et al. (1987) have similar findings. Different seed rates had significant effect on 1000 grain weight. Significantly higher grain weight was observed in plots sown within the range of 62 to 86 kg ha–1 seed rate (28.71 to 29.32 g) while lowest 1000 grain weight of 27.53 g was obtained from 99 kg ha–1 sown plot obtaining grain weight at highbrseed rate, can be due to the competation among plants for all available resources, which was imposed by higher rate resulting in greater number of plant per unit area.
| Table 1: | Emergence/m2 of wheat cv. Bakhtwar-92 as affected by seed rates and sowing dates |
| Table 2: | Number of productive tillers/m2 of wheat cv. Bakhtwar-92 as affected by seed rate and date of sowilig |
| Means of the same category followed by different letters are significantly different using LSD test at 5% level of significance | |
| Table 3: | 1000 grain weight (g) of wheat cv. Bakhtwar-92 as affected by seed rate and sowing dates |
| Table 4: | Seed grade recovery (%) of wheat cv. Bakhtwar-92 as affected by seed rates and sowing dates |
| Means of the same category followed by different letters are significantly different using LSD test at 5 percent level of significance | |
| Table 5: | Grain yield kg ha–1 of wheat cv. Bakhtwar-92 as affected by seed rate and sowing dates |
| Means of the same category followed by different letters are significantly different using LSD test at 5 percent level of significance | |
Highest 1000 grain weight at the lowest seed rate of 40 kg ha–1 as compared with 60, 80,100 and 120 have been reported by Ahmad et al. (1995). Mujahid (1972) observed decline in 1000 grain weight when seed rate of 130 kg ha–1 was used as compared with 60, 80 and 100 kg ha–1 of seed rate although grain yield/ha was higher at 130 kg ha–1.
Seed grade recovery was significantly affected by date of sowing only (Table 4). Plot sown in Nov. (1st to 30th Nov.) had significantly higher seed grade recovery (70.56 to 72%) as compared with those sown in Dec. (56.63 to 63.06%). Thses results are in agreements with those reported by Zeb et al. (1987) who reported reduction in seed weight and grain yield with delay in sowing from 25th Oct. to 24th Dec.
Data recorded on grain yield kg ha–1 is presented in Table 5. The data showed that the effect of sowing dates was significant while seed rates had no significant effect on grain kg ha–1. Plots sown on 20th Nov. had highest grain yield of 3068 75 kg ha–1 followed by 10th and 1st Nov. plantation. The lowest grain yield of 1502.09 kg ha–1 was produced by 20th Dec. sown plots. These results are supported by Waraich et al. (1982). Ashraf (1968) obtained as much as double grain yield of wheat when sown in Nov. as compared with those sown in month of Dec. The non significant effect of seed rate in our study is in contrast to those reported by Mishra (1993) who found greator yield when crop was sown at a seed rate of 125 kg ha–1 as compared with 100 and 150 kg ha–1 seed rate. Chatha and Nazir (1984) studied the effect of five seeding rates ranging from 18 to 92.5 kg ha–1 and concluded that seeding rate below 92.5 kg ha–1 did not improve grain yield of wheat in timely sown crop. Nazir et al. (1987) have observed that 100 kg ha–1 of seed rate had significantly greater number of productive tiller and grain yield as compared with 40, 60 and 80 kg ha–1 sown seed. Our results suggest that seeding rate between 6299 did not effect the grain yield of wheat variety Bakhtwar-92, while delaying in sowing from November to late December significantly decreases the grain yield.