Plant height (cm)
Table
1 data show that there were significant differences in plant height among the four wheat cultivars i.e. Daman-98, Punjab-96, Dera-98 and Inqilab-91. The amount of nitrogen also significantly affected plant height. Interaction was non-significant among the four cultivars and the five nitrogen doses. Plant height increased, with increasing nitrogen level from the control level to 200 kg/ha. Maximum plant height (82.2 cm) was recorded when nitrogen dose was 200 kg/ha, while minimum plant height (65.6 cm) was recorded in the control. The plant height for the four cultivars averaged over doses of nitrogen showed that Daman-98 had maximum plant height (87.4 cm) while Dera-98 had the minimum plant height (63.3 cm). The interaction between nitrogen and the cultivars was found to be non-significant. However, maximum plant height (92.8 cm) was recorded for Daman-98 when nitrogen dose was 150 kg/ha, while Dera-98 had minimum plant height (53.5 cm) with 0 kg/ha N was applied. These results are supported by the findings of Saleem (
1987) and Khan et al.(
2000) who reported that increasing the level of nitrogen increased the plant height.
Plant population per meter squareTable
2 data show that there were significant differences in plants per meter square of the four wheat cultivars. The amount of nitrogen also significantly affected the number of plants per meter square. Interaction among the four cultivars and the five nitrogen doses was non-significant. Number of plants per meter square increased from the control level of nitrogen to 200 kg/ha. Maximum number of plants per meter square (351.4) was recorded when dose was 200 kg/ha. While the minimum number of plants per meter square (189.8) was recorded in control. The tillers per meter square for the four cultivars averaged over doses of nitrogen showed that Dera-98 produced the maximum number of plants per meter square (336.3) followed by Inqilab-91 (315) and Punjab-96 (256.1). Daman-98 produced the lowest number of plants per meter square (241.2).
Interaction between the nitrogen and the cultivars was found to be non-significant. However, maximum number of plants per meter square (456.8) was produced by Dera-98 when the dose was 200 kg/ha, while Punjab-96 grown with 0 kg N/ha produced the lowest number of fertile tillers per meter square (152.8). Tiller production is considered as an inherent genotype features but Bhorghi (2000) reported that by increasing nitrogen at plant level, the biomass increase is associated with larger leaves that stay green longer, tall stems and a large number of tillers surviving to maturity.
Number of spikes per meter square
Table
3 data show that the four wheat cultivars had no significant differences in total spikes per meter square. The amount of nitrogen significantly affected the total number of spikes per meter square. Interaction among the four cultivars and the five nitrogen doses was not significant. Total number of spikes per meter square increased from the control level of nitrogen to 200 kg/ha. The interaction of nitrogen amount with wheat cultivars showed that maximum number of spikes per meter square (315.4) was produced when dose was 200 kg/ha while the minimum number of spikes per meter square (154) was recorded in control. The total number of spikes per meter square for the four cultivars averaged over doses of nitrogen showed no significant differences. The interaction between nitrogen and cultivars was also found to be not significant regarding the total number of spikes per meter square. However, maximum number of spikes per meter square (422.5) was produced by Dera-98 when nitrogen dose was 200 kg/ha while Daman-98 produced with 0 kg N/ha lowest number of spikes per meter square (133). These results confirm the findings of Hussain et al.(
1984), who observed that increasing nitrogen application increased the number of fertile tillers per unit area. Geleto et al.(
1995) reported that grain yield is closely related to the number of spikes per unit area. Fertilized plots produced more spikes than the control. Such response can be attributed to the adequate nitrogen availability which might facilitate the tillering ability of the plants, resulting in a greater spike population. Ayoub et al.(
1994) also reported that spike population increased with increase in nitrogen level.
Single spike weight (g)
Table
4 data show that there were no significant differences in spikes weight of the four wheat cultivars. The amount of nitrogen significantly affected spike weight. Interaction among the four cultivars and the five nitrogen doses was non-significant. Spike weight increased as amount of nitrogen was increased from the control level to 200 kg/ha. Table
4 shows that maximum spike weight (3.5 g) was produced when the nitrogen dose was 200 kg/ha while the minimum spike weight (2.8 g) was recorded in the control. The spike weight of the four wheat cultivars averaged over doses of nitrogen showed that Daman-98 produced the heaviest spike (3.9 g) while Dera-98 produced the lowest spike weight (2.9 g). The nitrogen levels and wheat cultivars did not interact positively because all nitrogen doses were not significantly different from the spike weight in the control treatment, but these results are in conformity with Khan et al.(
2000) regarding the effect of nitrogen on the varietal means of spike weight.
Number of grains per spike
Table
5 data show that there were no significant differences in number of grains per spike of the four wheat cultivars. Nitrogen at 0 to 200 kg/ha significantly affected the number of grains per spike. Interaction among the four cultivars and the five nitrogen doses was significant. Application of nitrogen resulted in more grain production per spike as compared to the control. But at higher doses, grain production per spike did not differ significantly from that of the non-fertilized plots. The number of grains per spike of the four wheat cultivars averaged over doses of nitrogen also showed no significant effect. Punjab-96 produced the maximum number of grains per spike (51.8) followed by Dera-98 (51.8) and Inqilab-91 (51.6) while Daman-98 produced the lowest number of grains per spike (50.0). Maximum number of grains per spike (59.1) was produced by Inqilab-91 when dose was 200 kg/ha while Inqilab-91 at 0 kg N/ha also produced the lowest number of grains per spike (43.0 g). These results coincide with the results of Ashraf (
1986) who concluded that nitrogen increased the number of grains per spike. Meynard (
1987) reported that the number of grains per spike is the best indicator of wheat response to nitrogen and that grains per spike is negatively affected by nitrogen deficiency.
Thousand grain weight (g)
Thousand grain weight is an important yield parameter. Table
6 data show that there were no significant differences in the 1000-grain weight of the four wheat cultivars. The nitrogen levels significantly affected 1000-grain weight. Interaction among the four cultivars and the five nitrogen doses was also found not significant. Nitrogen at high rate produced heavier grains. The thousand grain weight of four wheat cultivars averaged over doses of nitrogen showed no significant differences. These results showed that the 1000 g weight of the four wheat cultivars were Inqilab-91>Punjab-96, Daman-98>Dera-98. It is obvious from these results that an increase in the nitrogen dose resulted in an increase in the grain weight. These results agree with the findings of Chaudhary and Mehmood (
1998) who reported that 1000-grain weight of wheat was significantly affected by different nitrogen levels.
Biological yield (t/ha)
The total dry matter produced by a plant as the result of photosynthesis and nutrients uptake, minus that lost by respiration is called biological yield (Shah,
1994). Table
7 shows the biological yield of wheat varieties as affected by nitrogen levels. There were no significant differences in biological yield (t/ha) of the four wheat cultivars. Interaction among the four cultivars and the five nitrogen doses was significant. The biological yield increased as amount of nitrogen applied was increased from the control level to 200 kg/ha. Maximum biological yield (9.6 t/ha) was recorded at 200 kg/ha, which was not significantly different from the recommended dose of nitrogen (100 kg/ha). The biological yield of the four cultivars averaged over doses of nitrogen showed no significant differences. Daman-98 produced the maximum biological yield, which could be attributed to the plant height characteristics, followed by Inqilab-91 (8.3 t/ha) and Punjab-96 (7.0 t/ha). Dera-98 produced the lowest biological yield (6.8 t/ha). The nitrogen levels and the cultivars interacted significantly. These results agree with those obtained by Hayee et al.(
1989), who concluded that by increasing level of nitrogen increased biological yield. These results confirmed the results of Khan et al.(
2000) who obtained maximum biological yield in plots treated with 285 kg nitrogen per hectare.
Grain yield (t/ha)
Table
8 data on grain yield show that there were significant differences in grain yield of the four wheat cultivars. The amount of nitrogen also significantly affected grain yield. Interaction among the four cultivars and the five nitrogen doses was found to be significant. Grain yield increased as amount of nitrogen was increased from the control level to 200 kg/ha. The nitrogen levels interacted positively with wheat cultivars.
The highest grain yield of any crop is the result of all positive relationships of the yield components. Fertilizer (especially nitrogen) application enhances the grain yield of wheat varieties.
The different wheat varieties belong to the same Triticum aestivum L. species. But the soil nitrogen level was very low (0.02%), the experimental site located in the arid region of the country where organic matter level is low (0.5%) (Table 9).
The results presented in Table 8 reveal that low to high nitrogen application significantly increased the grain yield over that of the control. Wheat grain yield resulting from application of 50 to 200 kg/ha nitrogen differing insignificantly from each other could be attributed to the low soil organic matter content. Wheat grain yield resulting from nitrogen application at 200 kg/ha did not differ significantly from the yield resulting from application of recommended dose of nitrogen for the area. It was obvious that the low dose was not significantly different from 100, 150 and 200 kg N/ha. This non-significant difference indicates the positive effect of nitrogen supply on wheat. This difference of 0.74 t/ha between the lowest and the highest N dose seems to provide high benefit from a high dose of nitrogen application under the experimental conditions. The application of nitrogen at 200 kg/ha resulted in boosting the grain yield of wheat (Triticum aestivum L.). The response of varieties to application of nitrogen at different rates was found to be significant. First, the difference of grain yield can be attributed to variations in the grain yield potential of tested varieties. Second, their different response to differently applied nitrogen. The variety means averaged over the nitrogen levels shows that Daman-98 and Inqilab-91 are varieties superior to Punjab-96 and Dera-98. Both superior and inferior varieties differ significantly from each other but there were non-significant differences within the group. Punjab-96 did not differ significantly from Dera-98 but these two varieties had a lower grain yield than Daman-98 and Inqilab-91, and so, were inferior varieties. The interaction between two factors (N levels×varieties) was statistically significant. The interaction results indicated that except for Inqilab-91, the remaining three varieties showed similar interaction with application of 50 to 200 kg N/ha. The low dose (50 kg N/ha) was significantly different from the high dose of N but it did not differ significantly from the recommended dose of fertilizer (100 kg N/ha).
It can be summarized from these results that all four varieties performed well and showed positive response to the high dose of nitrogen under the climatic conditions of Dera Ismail Khan (NWFP) Pakistan. Nitrogen can be applied at high rate of 200 kg N/ha to any wheat variety without having adverse effect on the recommended yield. These results agree with the findings of Gandapur and Bhatti (1983), Rustam and Yasin (1991), and Bakhsh et al.(1999), who reported that by increasing the level of nitrogen, the grain yield was also increased.
Grain protein content (%)
The data regarding the grain protein content in Table
10 data on grain protein content show that there were significant differences in the quality of four wheat varieties tested under the climatic conditions of D.I. Khan (NWFP) Pakistan. The amount of nitrogen also significantly affected the quality of grain protein. Interaction among the four cultivars and five nitrogen doses was found to be significant. Evidently protein content increased as amount of nitrogen was increased from the control level to 200 kg/ha. Maximum grain protein content (14.5%) was noted at the highest dose of 200 kg/ha in variety Dera-98. The minimum grain protein content (8.5%) was recorded in the control for variety Dera-98.
The grain protein content of the four wheat cultivars averaged over doses of nitrogen showed that grains of Inqilab-91 contained maximum grain protein content (12.3%) followed by Dera-98 (12.2%) and Punjab-96 (11.9%). Daman-98 produced the lowest grain protein content. These results agree with the findings of Chaudhary and Mehmood (1998) who reported that grain protein content was significantly affected by levels of nitrogen. Guaer et al.(1992) concluded that application of N fertilizer increased grain protein content compared with the control in all cultivars. Positive responses to increasing nitrogen have been associated with increase in grain protein content. Inqilab-91 proved to be the best in protein content which might be due to its better genetic response to the applied nitrogen. This was confirmed by Banziger et al.(1992), who reported that genotypic variability in grain protein content may be affected not only by physiological traits but also by N supply in the soil. Our finding that protein content varied among the tested varieties confirms the findings of Zhu et al.(1991), who reported variation of protein content in seven wheat varieties.
It can be concluded from these results that Inqilab-91 is richer in protein, compared to Daman-98, Punjab-96 and Dera-98 wheat varieties. The results showed that high quality grains of wheat i.e., rich in protein and high grain yield can be obtained only by application of nitrogen at high rates especially in fields surrounded by Eucalyptus camaldulensis as its allelopathy had no ill effect on the protein content of wheat.
Answers to all your Biology Questions
