Abstract: Field experiment was conducted to study the performance of various maize varieties as affected by different NP levels. Analysis of the data revealed that days to tasseling (82.96), thousand grain weight (268 g), biological yield (20293 kg ha-1), and grain yield (3193 kg ha-1) was significantly affected by different varieties. In case of fertilizer levels days to tasseling (77), biological yield (20067 kg ha-1), grain yield (3073 kg ha-1), and harvest index (15.6) was significantly affected by different NP levels. Similarly, interaction between varieties and NP had a significant effect on days to tasseling, thousand grain weight, biological yield, harvest index and grain yield. Variety “Hybrid No. 922” produced maximum days to tasseling (83), thousand grain weight (268 g), biological yield (20293 kg ha-1), and grain yield (3193 kg ha-1) when compared to other varieties. When the effect of different levels of NP was taken into an account, it was revealed that plots treated with NP levels of 120: 60 kg NP ha-1 produced maximum grain yield (3070 kg ha-1) and harvest index (14.94).
Introduction
Maize is a crop with high yield potential and it occupies an important place in the cropping system of Pakistan. It not only provides food to the country fast growing population but also supplies raw materials to some of her industries. Pakistan though an agricultural country, is deficient in food grain and other food articles. The main cause of food shortage in the country has been failure of increased production of food grain to keep pace with the fast increase in population. To fill the gape between supply and demand, it is necessary to increase the production of food grain in the country. Production can be increased by bringing more culturable waste land under cultivation and increasing per unit of crop from the area already under cultivation. Maize is the third most important cereal crop in Pakistan after wheat and rice. It is grown extensively in the temperate, tropical and sub tropical regions in the world. However, it performs poorly under high temperature and low humidity conditions, damaging the foliage and interfere with proper pollination resulting in poor grain formation Much of increase in maize yield in recent decades has been closely associated with increased level of nitrogen and phosphorous. It is estimated that about 40-50% increase in yield of maize is possible if proper dose of N and P is applied. N and P above or below the optimum level will affect the maize crop severely. Alfoldi et al. (1994) investigated that concentration in the mature grains of maize were higher at high doses of nitrogen. N and P fertilizers at higher rate and especially in combination with lime markedly increased maize yield and NPK and Ca uptake (Invoilov et al., 1990). Kostic et al. (1991) reported that as compared to nitrogen alone, phosphorous increased average gain yield of maize by 11.5% at a lower and 14.2% at higher nitrogen rate. Singh and Duby (1991) concluded that grain yield and net returns increased with increase in nitrogen and phosphorous rates. Similarly, Thiraporn et al. (1992) reported that grain and biomass yield increased up to 80 kg N ha-1, higher application did not increase biomass. Manzor et al. (1983) and Silva (1992) reported that application of N increased significantly the yield of maize crop. Arian et al. (1989) and Mishra (1988) concluded that number of grains cob-1 and grain yield of different maize genotypes were significantly increased with increasing levels of N and P. Amoruwa et al. (1987) reported that grain and stover yield, number of grains cob-1 and 1000 grains weight increased when N was applied at the rate of 150 Kg ha-1.
Keeping in view, the role of N and P in the nutritional requirements of maize crop, the present research project was carried out to study the effect of different levels of NP on maize varieties.
Materials and Methods
In order to study performance of various maize varieties as affected by different NP levels, an experiment was conducted at Malakandher Research Farm, NWFP Agricultural University, Peshawar during summer 1999. Before sowing, a composite soil sample was taken for various physiochemical properties (Table 1). The experiment was laid out in randomized complete block design (RCBD) with split plot arrangements, and were replicated four times. Varieties were allotted to the main plots and NP levels to sub plot. All standard agronomic practices were followed during the course of study.
| Maize varieties |
| a. Hybrid No. 922 | b. Sarhad white | c. Sweet Corn |
| NP levels (kg ha-1) |
| F1 (00:00) | F2 (60:60) | F3 (60:120) |
| F4 (120:60) | F5 (180:60) | F6 (60:180) |
| F7 (120:120) |
| Table 1: | Physiochemical properties of the soil |
Data regarding days to tasseling, cob length (cm), 1000-grain weight, biological yield, harvest index, grain yield (kg ha-1) were recorded and analyzed according to RCBD and upon obtaining significant differences Least Significant Differences (LSD) test was applied (Steel and Torrie, 1980).
Results and Discussion
Days to tasseling: Mean values of the data revealed that varieties and NP levels had significantly (P ≤ 0.05) affected days to silking. Highest number of days (82.96) to tasseling was noted in case of Hybrid No. 922. NP levels showed a significant (P ≤ 0.05) effect on days to tasseling. Maximum number of 46.33 days to tasseling was recorded from control plots and minimum of 75.25 days to tasseling were kept in plots treated fertilizer at the rate of 120:60.
| Table 2: | Days to tasselling and cob length (cm) as affected by different varieties and NP levels on maize |
| Table 3: | Thousand grain weight (g) and biological yield (kg ha-1) as affected by different varieties and NP levels on maize |
| Table 4: | Harvest Index (%) and grain yield (kg ha-1) as affected by different varieties and NP levels on maize |
| Mean followed by different letters are significantly different from one another at P < 0.05 | |
The probable reason could be that nitrogen had enhanced vegetative growth, which delayed reproductive stage. Similar results are also reported by Onisie et al. (1993). In case of interaction between varieties and NP levels, it was significantly affected to days to tasseling. Maximum 86 days to tasseling was recorded from plots of Hybrid No. 922 variety at control plots.
Cob length (cm): Data revealed that number of cob length was non significantly affected by different varieties (Table 2). Variety Sarhad white showed maximum (20.66 cm) cob length, while minimum cob length (18.18 cm) was recorded from those plots, which were sown with sweet corn variety. Mean values of the data (Table 2) showed that NP levels had a non significant effect on cob length. Maximum (20.49 cm) cob length was recorded in those plots, which were treated with 120:60 kg NP ha-1, while minimum cob length (17.48 cm) was noted from plots in which fertilizer was used at the rate of 60:60 kg NP ha-1. Similar results are also reported by Amoruwa et al. (1987). Mean value of the data also suggested that interaction between varieties and NP levels did not affect cob length significantly. However, highest longer cobs was recorded in case of Sarhad white treated with 180:60 or 120:60 kg NP ha-1, while minimum (15.75 cm) cob length was produced from those plots, which were sown with Sweet corn and received 60:120 kg NP ha-1.
Thousand grain weight (g): Data regarding thousand grains weight revealed that there was significantly (P < 0.05) affected by different varieties. Heavier grains (286.50 g) were recorded from Hybrid No. 922, while lighter grains were noted in case of sweet corn (181.50 g). NP levels had a non significant effect on thousand grain weight. Maximum grain weight (240.50 g) was produced in those plots, which were treated with NP levels of 180:60 kg ha-1. While minimum 1000 grains weight (225.58 g) was recorded from plots fertilized at the rate of 60:60 kg NP ha-1 (Table 3). In case of interaction between varieties and NP levels, it was significantly affected on thousand grains weight. Also indicated that maximum of 285.30 g thousand grains weight was recorded from Hybrid No. 922 and receiving 180:60 kg NP ha-1, while minimum thousand grain weight (171.30 g) was noted from Sweet corn in those plots which were treated with NP levels of 60:60 kg ha-1. Similar results were also reported by Ram et al. (1993).
Biological yield: Data showed that biological yield was significantly (P ≤ 0.05) affected by different varieties (Table 3). Maximum biological yield (20293 kg ha-1) was produced (Table 3) by plots sown with Hybrid No. 922, while lowest biological yield was recorded from Sarhad white (14840 kg ha-1). NP levels showed a significant (P < 0.05) effect on biological yield. Maximum biological yield (20067 kg ha-1) was produced by those plots which were treated with NP levels of 120:60 kg ha-1, while minimum biological yield (15947 kg ha-1) was recorded from plots when fertilizer was used at the rate of 60:180 kg NP ha-1. Similarly, in case of interaction between varieties and NP levels, a significant effect on biological yield was noted. Maximum biological yield was recorded from plots sown with Hybrid No. 922 and treated with 120:60 kg NP ha-1, while minimum biological yield was in which NP was treated with 120:120 kg ha-1 and plots sown with Sarhad white. These results agree with Muhammad et al. (2002).
Harvest index: Harvest index was non significantly affected by different varieties (Table 4). However, maximum harvest index (15.6 %) was recorded from plots sown with Hybrid No. 922. When the effect of different NP combinations was taken into consideration, it was revealed that various NP levels had a significant (P ≤ 0.05) effect on harvest index. Mean value of the data indicated that harvest index was maximum when plots were treated with NP combination of 60:180 kg ha-1 while minimum was noted from control plots. In case of interaction between varieties and NP levels a significant effect was noted. It can be inferred from the data that maximum harvest index was noted from plots when sown with Hybrid No. 922 and treated with 120:60 kg NP ha-1, while minimum was recorded from control plots and the plots were sown with Sweet corn. Similar results were also reported by Muhammad et al. (2002).
Grain yield: It can be inferred from the data concerning grain yield that different varieties had a significant (P ≤ 0.05) effect on grain yield (Table 4). Maximum grain yield was produced from plots sown with Hybrid No.922 (3193 kg ha-1). While minimum grain yield (1993 kg ha-1) was recorded from Sarhad white. Similarly analysis of the data also revealed that NP levels had a significant (P < 0.05) effect on grain yield. Highest grain yield (3073 kg ha-1) was noted from plots treated with 120:60 kg NP ha-1 while lowest grain yield (2040 kg ha-1) was recorded from control plots. Statistical analysis of the data also revealed that interaction between varieties and NP levels had significantly (P ≤ 0.05) affected grain yield. Maximum grain yield (4480 kg ha-1) was produced by those plots, which were sown with Hybrid No.922 and treated with 120:60 kg NP ha-1. While minimum grain yield (1667 kg ha-1) was noted from those plots sown with Sarhad white and 60:180 NP. These results are in line with those reported by Sharma and Sharma (1991). Similar results are also reported by Ram et al. (1993), Sharma (1991), Nigrila and Negrila (1994) and Brar et al. (1989) and Ali et al. (2002).
In conclusion hybrid No. 922 and 120:60 kg ha-1 NP is the best dose of fertilizer for maize to achieve the highest yield.
Acknowledgement
The financial support of Department of Agronomy, NWFP Agricultural University Peshawar is gratefully acknowledged.