भारत के आलू उगाने वाले क्षेत्रों में पी उपलब्धता के आधार पर फॉस्फोरस उर्वरकों की सिफारिश

Phosphorus is one of the key nutrients required for higher and sustained productivity of potato and its influence on tuber yield is very well established. Maximum potato yield occurs when sufficient P is available during early vegetative development and the entire period of tuber growth.

Total plant P uptake increases rapidly during tuber initiation, levels off to a constant rate during tuber bulking, and ceases with plant maturation occurs primarily through the transfer of P reserves from the vine and roots.

Phosphorus uptake by potatoes is relatively low compared with uptake of potassium or nitrogen but similar to uptake of sulfur.  The amount of P in the soil solution that is readily available for plant uptake is very small compared with the total amount of P in the soil. 

Upon addition to the soils, soluble phosphates react with the constituents of the soil and form compounds which are less soluble, depending upon the soil type.

In acid soils, the reaction products are aluminium and iron phosphates and in the predominantly calcareous soils, the reaction products are calcium phosphates. As a result most of the P applied (often as much as 90%) is rendered unavailable for crop uptake but is still retained in insoluble form.

This is the reason that the potato based cropping system in different potato growing pockets generally show positive P balance resulting into its build up. Annual applications are often necessary to maintain adequate labile P.

Thus, soils commonly have large reserves of ‘fixed’ P that could support long term crop requirements if it could be mobilized through appropriate soil management.

A general blanket application of fertilizer leads to its poor efficacy and wastage of costly resources as well as of environmental pollution.  This becomes more relevant in case of P as unlike nitrogen applied P remains in soil and adds to its build up.  In addition, this has resulted in severe imbalance of nutrients in soil.

Keeping this in view, a multi location experiment was conducted in the major potato growing states of India under the All India Coordinated Research Project on Potato during 2005-06 to 2006-07 to evaluate suitable dose of P based on soil test on P economy in potato. Exact quantification of Phosphorus fertilizer based on soil test is very important. 

Eighteen field experiments were conducted at eleven centres of AICRP (Potato) representing different agro-climatic regions of the india namely, Bhubaneshwar (Orissa), Chhindwara (MP), Deesa (Gujarat), Dholi (Bihar), Hisar (Haryana), Kalyani (West Bengal), Kota (Rajasthan), Ooty (Tamilnadu), Patna (Bihar), Jalandhar (Punjab), and Pantnagar (Uttrakhand) with popular potato cultivars of the regions during 2005-06 and 2006-07  to investigate the soil test based P application in potato.

Experimental details of the trial at different centers are given in table 1.  The four manurial treatments involving P through inorganic fertilizer, based on soil test,  phosphorus recommendation for potato were applied (table 1) and tried in randomized block design with four replications at all the centers.

Soil of the experimental field was classified as low (≤10 ppm),   medium (10-20 ppm) and high (≥20 ppm). At all the centers, Olsen’s P method was used for testing available P in the soil (Table 2).

Initial available P, in experimental plots is given in table 3.  At all the centres the crop was grown during rabi (winter) season, following recommended package of practices except at Ooty centers where the trials were conducted in summer/ kharif 2006 and 2007.

Nitrogen was applied in two splits as per recommendation i.e. half at planting and rest at earthing up at 40 days after planting. Basal application of P and K was done using single super phosphate and muriate of potash respectively, as per treatments at the time of planting. Crop was harvested at maturity and tuber yield and numbers were recorded from all treatments.

Table 1: Experimental details of different locations for 2005-06 and 2006-7 

 Table 2: Treatments details for different locations of AICRP (Potato) centers based on soil test

 Table 3: Initial availability of “P” in experimental plots at different locations

Results and Discussion

Potato tuber yield from soil having low P availability (≤10 ppm)

Soils of experimentation field at Bhubaneshwar (Orissa), Chhindwara (MP), Dholi (Bihar), Hisar (Haryana), Jalandhar (Punjab), Ooty (Tamilnadu), Kalyani (West Bengal) and Kota (Rajasthan) had available P less than 10 ppm, therefore 75% of recommended P and 125% of recommended P  were applied as T3 and T4 respectively (table 4, 5 and 6).

 At Chhindwara, during both the year, total tuber yield (28 and 26.12 t/ha) and net return (Rs. 71580 and 88740/ha) were highest in treatment receiving 125% of recommended P applied followed by application of recommended dose of P (27.2 and 25.51 t/ha and Rs 69191 and 86455/ha), respectively. Highest total number of tubers was also obtained with 125% of recommended P application followed by application of recommended dose of P. 

During first and second years of experimentation the percent increase in yield was 2.9 and 2.4% and net return was 3.5 and 2.6%, respectively in the treatment receiving 125% recommended dose of P over 100% recommended dose of P. During both the year, application 125% of recommended P   gave maximum numbers (447.3 and 442.9 thousand /ha,) followed by recommended dose of P (439.0 and 417.6 thousand /ha,).

At Dholi, the trial was conducted on soil with available P 18 kg/ha. Higher tuber yield (13.09 t/ha) and net return (Rs. 22450/ha) were obtained by the application of 125% of recommended P. The yield at recommended dose of P was though at par,   the net return was Rs 4300/ha less as compare to 125% recommended dose of P.

The availability of P in the experimental plot before planting at Hisar was 22 kg P/ha (< 10 ppm). Total tuber yield and total number of tubers was highest in recommended dose of P followed by 125% of recommended P. However, the difference was not significant. These parameters were lowest where P was not applied. Net gain was highest in the treatment of recommended dose of P (Rs. 37025/ha) and lowest without P application (Rs. 26365/ha).  Which was Rs 1538/ha higher than net return at 125% of recommended P application.

At Jalandhar, recommended P application recorded higher values for total tuber yield (29.6 t/ha) and net returns (Rs. 39750/ha) followed by 125% of recommended P (28.4 t/ha and Rs. 35980/ha, respectively). The least values for these two attributes were recorded without P application (23.5 t/ha and Rs. 22150/ha, respectively). 

During second year, 125% recommended P application recorded higher values for total tuber yield (29.06 t/ha) and net returns (Rs. 38080/ha) followed by application of recommended dose of P (28.71 t/ha) yield and Rs.37050/ha net return).

The total number of tubers were highest with application of recommended dose of P (477.4 thousand/ha) followed by 75% of recommended P (447.2 thousand /ha).  The tuber yield however, was statistically at par with recommended P and 125% of recommended P during both the year.

At Ooty, during both the year, tuber yield (34.73 t/ha), net returns (Rs.84613/ha) and total tuber numbers (690.1 thousand/ha) were higher with 125% recommended dose of P followed by application of recommended dose P. During second year, yield followed similar trend but the number of tubers were not influenced by the treatments. 

At Kalyani, during both the year, the differences among treatments for yield were also non-significant except for total number of tubers which was highest at 75% of recommended P.  Highest net return (Rs. 52851/ha) was recorded for the recommended dose of P.

During second year, the highest yield of tubers (28.53 t/ha) and net return (Rs. 36586/ha) was recorded with 125% of recommended P followed by application of recommended dose of P (28.10 t/ha tuber yield and Rs.35639/ha net returns). These two treatments were statistically at par. Total tuber numbers (597.2 thousand /ha) were higher in treatment where 75% of recommended P applied.

At Kota, highest total yield (23.89 t/ha) and net returns (Rs. 55345/ha) were obtained in treatment receiving 125% of recommended P which was 4.4 and 6.9% higher as compared to application of recommended dose of P. Highest numbers of total tubers (688 and 642 thousand /ha) were harvested in treatment where P was not applied. 

During second year, the highest total yield (20.11 t/ha) was obtained in treatment receiving application of recommended dose of P was applied followed by 125% of recommended P (20.03 t/ha). The highest net returns (Rs. 38980/ha) were obtained with application of recommended dose of P followed by 125% of recommended P (Rs. 38047/ha).

At Bhubaneshwar, highest tuber yield (15.19 t/ha) was obtained with 125% of recommended P application which was significantly better than any other treatments and this treatment also gave the highest net return. Under low P conditions, application of recommended dose remains insufficient and optimum yield was not achieved at all the center.

At these centers when 100-125% of recommended P was applied, yield improved. This result confirms the recommendation that at deficient soils application of P may be increased by 25% above recommended dose

Table 4 : Total yield (t/ha) in the soils having < 10ppm  initial P at different locations

T1: No phosphorus application, T: Application of recommended dose of P, T3: 75% of recommended P and T4: 125% of recommended P

Table 5 : Total tuber number  in the soils having < 10ppm  initial P at different locations (thousand/ha).

T1: No phosphorus application, T: Application of recommended dose of P, T3: 75% of recommended P and T4: 125% of recommended P

Table 6 : Net return (Rs/ha)  in the soils having < 10ppm  initial P at different locations

T1: No phosphorus application, T: Application of recommended dose of P, T3: 75% of recommended P and T4: 125% of recommended P

Potato tuber yield from soil having medium P availability (10 -20ppm)

 Soils of experimental field at location namely Patna (Bihar), Pantnagar (Uttrakhand) and Bhubaneshwar (Orissa),  had available P (Olsons, P) between 10-20 ppm, therefore 25% of recommended P and 50% of recommended P were taken T3 and T4, respectively (table 7, 8 and 9).

At Patna, recommended P gave highest tuber yield (36.87 t/ha) and the net return (Rs. 65535/ha) followed 50% of recommended P.  During second year also, the higher tuber yield (24.98 t/ha) was obtained at recommended dose of P, which was statistically superior to any other treatments.  

The net return was also highest with recommended dose of P (Rs. 48349/ha) followed 50% of recommended P (Rs. 39818/ha). 

At Pantnagar, the highest total yield (34.21 t/ha) were recorded in treatments where application of recommended dose of P applied which was significantly better than any other treatment. The 50% of recommended and recommended dose of P produced highest number of total tubers (487.1 and 459.7 thousand/ha, respectively).

The net return was also higher in treatment receiving 50% of recommended P (Rs. 36219/ha) followed by recommended dose of P (Rs 34882/ha) as compared to other treatments. During first and second years, yield increased by 7.08 and 10.09% and net return increased by 11.4 and 21.042%, respectively at recommended dose of P as compare to 50% P application.

At Bhubaneshwar, application of recommended doses of P gave the highest yield (22.54 t/ha) which was significantly better than any other treatments. The treatment not receiving any P resulted in lowerest yield. Recommended dose of P also produced significantly highest number of tubers 460.1 thousand/ha.

In terms of net returns, recommended dose of P produced highest return (Rs.29154/ha) followed by 50% of recommended dose of P (Rs. 22699/ha).  Therefore, at these centers, as available P was in medium range, the recommended P application gets the best yield. However, statistically at many places 50% of recommended P did not decrease the yield significantly and was at par with recommended P .

Potato tuber yield from soil having high P availability (≥20ppm)

Soils of experimentation field at Deesa (Gujrat) had available P (Olsons, P) more than 10 ppm, therefore 12.5% of recommended P and 25% of recommended P (T3 and T4) were taken. Results revealed non-significant differences among the treatments for tubers yield.

Highest tubers yield (46.21 t/ha) was obtained at recommended dose of P followed by the treatment receiving 25% of recommended P (45.69 t/ha, whereas, maximum number of tubers were recorded in treatment receiving recommended dose P (601944/ha) followed by the treatment not receiving any P (590139/ha).

Treatment that received 25% of the recommended dose of P recorded highest net return (Rs.163749/ha) followed by the recommended dose of P application (Rs. 162836/ha).

Since the soil was high in available P, no significantly effect of P application was observed. This is due to build up of available P has reached a level where response of its application may not be obtained in next few coming crops.

However, minimum maintains dose od P may be applied to avoid the risk of yield loss in subsequent years, P level may get depleted and need to be supplemented with recommended dose based on soil test .

Table 7: Total yield (t/ha) in the soils having 10-20 ppm and > 20ppm  P at different locations

*T1: No phosphorus application, T: Application of recommended dose of P, T3: 25% of recommended P and T4: 50% of recommended P for soils having 10-20 ppm

**T1: No phosphorus application, T: Application of recommended dose of P, T3: 12.5% of recommended P and T4: 25% of recommended P for soils having ≥20 ppm

Table 8: Total tuber number in the soils having 10-20 ppm and > 20 ppm   P at different locations

*T1: No phosphorus application, T: Application of recommended dose of P, T3: 25% of recommended P and T4: 50% of recommended P for soils having 10-20 ppm

**T1: No phosphorus application, T: Application of recommended dose of P, T3: 12.5% of recommended P and T4: 25% of recommended P for soils having ≥20 ppm

 Table 9: Net return (Rs/ha)  in the soils having  10-20 ppm and > 20ppm   P at different locations

*T1: No phosphorus application, T: Application of recommended dose of P, T3: 25% of recommended P and T4: 50% of recommended P for soils having 10-20 ppm

**T1: No phosphorus application, T: Application of recommended dose of P, T3: 12.5% of recommended P and T4: 25% of recommended P for soils having ≥20 ppm

Conclusion:

Study to economize on P dose from fertilizer in different P status of soils in different location revealed that soil having low P availability (≤ 10 ppm) responded to P fertilizers and there is need of P application.

Thirteen experiments conducted at low P status soils (≤ 10ppm), at different centers 100-125% recommended dose of P gave best tuber yield and also net returns. However, in case of medium P availability soils (10 to 22 ppm), the recommended dose of P fertilizer was found superior compared to other treatments.

Four experiments conducted at medium P status soils (10-20 ppm) 50% recommended dose of P or recommended dose of P was sufficient to meet P need of the crop and gave higher yield and also net returns. In case of high P status soils (≥ 20ppm), application of P did not respond.  

Therefore, finding clearly outlined the importance of soil test in efficiently use of costly P fertilizer and economize the cost of cultivation in soils testing high in P.

 Authors:

MK Jatav¹, Manoj Kumar², VK Dua³, Sushil Kumar³ and Jagan Singh Gora⁴

¹ Central Institute for Arid Horticulture, Bikaner-334006  (Rajasthan)

 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

² Central Potato Research Station, Patna–801 506, Bihar, India.

³Central Potato Research Institute, Shimla-171 001, Himachal Pradesh, India

⁴ Central Institute for Arid Horticulture, Bikaner-334006  (Rajasthan)