Research Article
Response of Potato Crop to Various Levels of NPK
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M. Masud Mahmood
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Khalid Farooq
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Shahid Riaz
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Potato (Solonum tuberosum) is an important crop of the world. It can produce 3-4 time more yield per unit area as compared to cereals. The average yield of potato crop is low (16.9 tons ha-1) in Pakistan as compared to advanced countries of the world (Anonymous, 1999). The reasons for low yield are many but unavailability of quality seed and inadequate and injudicious use of fertilizer are of prime importance.
Supply of nutrients plays an important role in growth and yield. Nitrogen is an essential constituent of protein and chlorophyll, where phosphorus fertilization contributes to early crop development and tuberization and enhances tuber maturation, whereas potassium influences both yield and tuber quality and also enhances plant resistance to withstand stress against drought and frost. In Northern Areas of Pakistan potato is grown on an area of 4700 ha (Anonymous, 2000). High altitude valleys of Northern Areas are ideal for production of disease free seed potato. Zanoni (1991) reported that the potato growers in Northern Areas do not use the chemical fertilizer. However, the contract growers of seed companies apply 1 to 2 bags of nitrophosphate (N:P=23:23) per one bag (50 kg) of potatoes planted for seed multiplication as recommended by the seed company. Undoubtedly fertilizer plays a remarkable role in increasing the yield of crops. Grewal and Sharma (1980) recommended fertilizer for potato in Indian Punjab as 150 Kg N, 80 Kg P2O5 and 120 Kg K2O. Malik (1995) reported recommended dose of fertilizers for Kalam valley as 200:150:75 NPK kg ha-1.
In Northern Areas the soils are different from the plains in their composition, physical properties and fertility status. Therefore, the present study was carried out to evaluate the effect of various levels of NPK on the growth and yield of potato crop.
The experiment was conducted at Daril valley district Diamer, Chilas during summer 2000. Potato variety Desiree (certified) was used as seed. Previous crops on the experimental plot were beans and maize. Experiment was planted on 20th of May 2000 using a seed rate of 2 tons ha-1 at row to row and plant to plant spacing 75 and 15 cm respectively. Experiment was layout in randomized complete block design with three replication having net plot size of 2.25 X 4 m2. Full dose of P2O5, K2O and half dose of nitrogen were applied at planting time. The remaining half dose of nitrogen was applied 45 days after planting (DAP). Crop was harvested on 15-10-2000. Following observations were recorded during the course of study.
Germination (%), soil coverage (%), no of stems/m2, plant height (cm), No. of tubers/m2, tuber size (three grades i.e. <35 mm (small), 35-55 mm (medium) and >55 mm (big), average tuber weight (g) and yield tons ha-1. Data on these parameters were recorded as described by Farooq et al. (2001) and Mahmood et al. (2002).
The detail of treatments is given below
Data were analyzed statistically through variance (based on randomized block design) and correlation was calculated using MSTAT main computer programme version 4.0 (Freed et al., 1987).
Data (Table 1) showed that maximum emergence 94.67 was recorded in T4 followed by 93.67 in T6 and lowest 90 in T5. Soil coverage was affected by fertilizer application at 60 days after planting (DAP). Treatments, T5 and T6 were significantly (0.05) different from other treatments. At 75 DAP there was no statistical difference between T3, T4, T5 and T6. At 90 DAP and 105 DAP all the treatments when fertilizer was applied at any rate was significantly different than control (T1). Number of stems m-2 was also lowest in control. The plant height (cm) increased linearly with the increase in fertility level (Table 1, Fig. 1). It was maximum in T6 (59.33 cm) and lowest in T1 (38.40 cm) control. Singh and Raghar (2000) reported that plant height was significantly affected by various doses of nitrogen. Maximum height (55.1 cm) was recorded with 160 kg N ha-1. In this study, plant height was 54.37 cm when 150 kg N ha-1 was applied and plant height was 59.33 cm when 200 kg N ha-1 was applied. The result revealed (Table 2) that maximum number of tubers/m2 was recorded in T6 (51.67) and lowest in T2 (41) and T1 (42), respectively. The % age of small size tubers (<35 mm) was higher in T1 (control) and T2 where only 100 kg N ha-1 was applied. Barches et al. (2000) reported that large size tubers were obtained when 175.5-125-125 Kg NPK ha-1 was applied along with 500 ppm cycocel, while medium size tubers with 112.5-75-75 kg NPK ha-1 with 250 ppm cycocel, where as with the application of 150-100-100 kg NPK ha-1 small tubers were produced.
Kumar et al. (2001) reported similar type of results that significant increase in yield from 100 to 150% of all grades was recorded with increase in recommended dose of NPK (160-60-120 kg NPK ha-1). It is evident from the data (Table 2) that all the fertilizer treatments increased the average tuber weight and yield over the control (Fig. 1), but among the treatments T3 and T4 were non-significant with each other in respect of yield. Highest yield of 44.10 tons ha-1 was recorded in T6 (200-150-75 kg NPK ha-1) which was significantly (0.05) higher with rest of treatments, followed by T5 (150-100-50 kg NPK ha-1), where yield of 38.50 tons ha-1 was recorded. These results are in conformity with the findings of Kushwah (1999) that yield increased linearly with the increase in fertility level.
All the fertilizer applications have shown marketable yield increase, however, the better responses and trends were observed with the use of fertilizers in the ratio of 200 kg N, 150 kg P and 75 kg K ha-1 under the soil condition prevailing in district Diamer.
Sultan et al. (1989) concluded that all fertilizer treatments showed considerable yield increasing with 135 kg N plus 120 kg P2O5 and 120 kg K2O under the soil condition prevailing in Mansehra district. The application of NPK (200:150:75 kg ha-1) is in accordance with the finding of Malik (1995).
The results of this study revealed that the fertilizer dose of NPK (200:150:75 kg ha-1) is found suitable in Darail valley (high hills of Northern Areas, Pakistan) to get the higher yields of potato crop.
Table 1: | Effect of NPK on growth characteristics of potato crop |
DAP = Days after planting, Means followed by different letters are significantly different at P < 0.05 |
Table 2: | Effect of NPK on yield components of potato crop |
Means followed by different letters are significantly different at P < 0.05 |
Fig. 1: | Response of plant height (cm), average tuber wt. (g) and yield (t ha-1) to different lavels of NPK |
Khan (1993) suggested 200 kg N, 100 kg P2 O5 and 75 kg K2O ha-1 to be economical combination, partially supported the results of present study. Where, higher dose of P2O5 150 kg ha-1 also give significance results along with N and potash combination. Therefore, it is suggested to the growers of this area to use the balance doses of NPK 200-150-75 kg ha-1for better yields.