Nitrogen
- Nitrogen is the first limiting nutrient for
plant growth.
- Its application is indispensable for successful
potato production.
- An adequate amount of nitrogen increases root
and shoot number and size of tubes.
- So it should be applied in right amount at right
time through right method.
- The comprehensive studies results, quoted and
compiled in the bulletin No. 32 reveal the following
information with regard to nitrogen application.
- Nitrogen response varies with the soil type,
varieties, length of growing season, organic manures,
kind of fertilizers, time and method of application,
moisture supply and nutrient interaction affect
nitrogen needs of the crop.
- Long duration potato varieties like Kufri
Badshah, Kufri lalina and Kufri
Sindhuri producing large-sized tubers are
more responsive to nitrogen than short duration
ones producing small and medium sized tubers.
- The use of organic manure's, FYM, green manuring,
composts and oil cakes have been found to improve
the yield.
- On N basis, the organic manures are less efficient
than the fertilizers.
- However, the combined use of organic manures
and fertilizers has been found better than the
use of fertilizer alone.
- Ammonium Sulphate and Ammonium Sulphate Nitrate
are usually the best fertilizers followed by CAN,
Ammonium Chloride and Urea.
- Application of urea by furrow method affects
sprout growth and in turn crop emergence.
- Its application at planting by furrow method
should not exceed 40-50 Kg N/ha otherwise emergence
would be affected.
- Its application by broadcast or in bands 5 cm
away from the tubers is advocated.
- In case of CAN, Ammonium Sulphate furrow method
is better than broadcast.
- The application of urea at top dressing is as
effective as Ammonium Sulphate or CAN. Therefore,
the application of urea at top dressing is advocated.
- The split application of urea, ½ at planting
and ½ at earthing-up has been found better than
three splits where the duration of the crop is
short.
- Urea can also be applied through foliar sprays
where it should be preferably combined with fungicidal
or pesticidal sprays.
- Nitrogen depresses potassium composition in
the plant. So an adequate amount of potassium
in soil is necessary for getting full benefit
from nitrogen.
- Nitrogen applied to Potato leaves sufficient
residues in the soil so as to affect the nitrogen
needs of succeeding crop like wheat, sunflower,
onion etc.
- The residual effect reduces the N requirement
of succeeding wheat by about 50 per cent.
- Application of nitrogen has been found to increase
the crude and true protein content of tubers.
- Lower doses have little effect on dry matter
and ascorbic acid content but higher doses could
depress them.
- N-application has been found to adversely affect
keeping quality of Potato tubers.
- Its application increases the size of tubers
and respiration rate of tubers.
- Big tubers exhibit higher rate of respiration
than small ones and are prone to more rotting.
- Nitrogen was also effective in decreasing the
incident of leaf spot diseases but increased the
incident of early blight, late blight and charcoal
rot.
- Nitrogen also increased the incidence of cut
worms and aphids.
- Nitrogen needs are found to vary with the potato
growing zone.
- However, the application of 180 to 240 kg N/ha
is advocated for the Indo
- Gangetic plains, alluvial soil zone.
- For the seed crop, the N-needs are about 30-40%
lower than the main crop.
Top
Phosphorus
- Phosphorus improves yield by its positive effect on
tuber number as well as the size of potato tubers.
- In the event of P deficiency, leaves lose lustre and
show curling with purple pigmentation and sometimes marginal
scorching.
- P hastens maturity and thus it contracts the delayed
maturity induced by excessive N fertilization.
- P deficiency is there in the alluvial soils of Punjab,
Uttar Pradesh and Bihar.
- Potato needs varied from 50 to 150 kg P2O5 /ha.
- Attempts have been made to recommend application on the
basis of soil test.
- The information on the critical level of soil P and
organic carbon could help in deciding whether a particular
soil requires P incorporation or not.
- If soil P is below the critical level it requires P
fertilization, otherwise not.
- Critical level of soil nutrients for getting economic
response of Potato to P application.
Soil
|
Variety
|
Critical P level
|
Source
|
Alluvial
(Punjab) |
Kufri Chandramukhi
(Autumn) |
10 ppm
(Olsen) |
Grewal
and Singh (1976) |
Alluvial
(Punjab) |
Kufri Chandramukhi
(Spring) |
13 ppm
(Olsen) |
-do- |
Hill Soil
(HP) |
Kufri Jyoti
(Summer) |
35 ppm
(Bray P1) |
Grewal
and Sharma (1979) |
- P-needs also vary with the objective of Potato cultivation.
- If the crop is raised for seed propose, higher dose
may not be required as raising the dose from 40 to 80
Kg P2O5/ha resulted in a decrease in seed sized tuber
yield.
- But for main crop production, higher dose is required.
- The water soluble P-carrier namely superphosphate, mono,
diammonium phosphate and pyrophosphates are a better source
of P than rockphosphate and bonemeal (Negi et al., 1982).
- The recovery of P even from single superphosphate by
Potato is about 10-15%.
- This shows that most of P remains unutilized in the
soil.
- Lot of efforts have been made to improve P-use efficiency
as listed below.
- Soaking of mother seed tubers in a solution containing
1.5% single superphosphate and 0.5% urea for 4 hr before
planting has been found to economize on P input by about
50 Kg P2O5/ha.
- The soaking in NH4 PHO4 solution was also effective
in supplying P to Potato crop (Sharmal et al, 1977).
- Care should be taken that the seed tubers after soaking
treatment should be dried in shade before planting.
- Entire dose of P should be applied at planting as split
application has not proved advantageous (Sahote and Govinda
Krishnan, 1984).
Top
Potassium
- Potassium chloride (MOP) and Potassium sulphate (SOP)
are the two major fertilizers used for supplying the potash
needs of crop. MOP usually contains 60 percent K2O while SOP
contains 50 per cent K2O plus 18 percent sulphur.
- The Potato crop is highly influenced by the potassium on
account of the following reasons.
- The quality of Potatoes grown on soils low in Potash
becomes easily impaired by 'black spot' or bruise blue.
- The potato flesh under the skin turns bluish-black if
the tubers are mechanically injured in the course of
harvesting or of storing and parking.
- The tuber content of starch, ascorbic acid, cystine,
methionine and protein increased with increasing rates of
S-containing fertilizers and decreased by increasing the
rates of Cl-containing fertilizer (Duba L.V., 1973).
- Sulphate of Potash is a better source of K than Muriate
of Potash for yield as well as quality of Potato tubers
because of the adverse effect of Chloride (present in MOP)
on dry matter and starch. (Bhandari et al., 1987) Farmer and
Parliament 22(2):11-12.
- Sulphur source in SOP (sulphate of Potash) improves the
quality of Potatoes (Dande et al., 1986).
- Two possible influences of Chloride on the carbohydrate
metabolism were studied by Halder, H.E., 1976
(Lordwirstchaftliche Forschung, Sonderhelf 32/I, 122-131).
P. Takeduch.
i)Reduction of photosynthesis in the leves
ii)Retardation of assimilate transport into the
tubers.
- During the whole growing season Potato plants were
supplied with 3 different amounts of chloride and sulphate:
i)High amount of chloride (12 me/lt) and traces of
sulphate
ii)Chloride and sulphate in equal amounts
iii)high amounts of sulphate (12 me/lt) and traces of
Chloride
- When the growth rate of tubers was high (six weeks after
flowering), the distribution of labeled photosynthesis in
the plants was studied after they had been supplied with
14CO2 for 24 hours.
- Most of the 14CO2 was assimilated by the plants given
equal amounts of chloride and sulphate.
- The percentage preparation of labeling in the leaves did
not differ significantly between the three treatments.
- Therefore, chloride could not have inhibited the
photosynthesis in the leaves.
- But there was a negative correlation between the
proportions in tubers and in stems.
- In the so-called "sulphate plants" the proportion in the
tubers was much higher than in the stems. In the 'chloride
plants' it was reverse.
- This indicates that chloride has retarded the
translocation of photosynthates from the stem into the
tubers.
- The 'sulphate plants' yielded the highest tuber weight
in connection with a slightly higher starch content.
- Application of low rates of K reduced the tendency of
tubers (var. Bintje) to sloughing.
- After cooking the discolouration was not affected by the
amount of K. (Hojmarh J.V., 1977).
- Salinity demands specific care in the choice of mineral
fertilizer.
- Suitable for saline conditions are fertilizers that are
osmotically less effective and low in their content of salts
which are already present in the soil.
- Chloride is one of the constituents in saline soils.
- If taken up in excessive amounts, it may cause
physiological disorders and consequently diminish quality as
described with vegetables potato, fruit, tobacco and
sugarcane.
- Apart from being virtually free of chloride, SOP
contributes less to osmotic stress than other K sources and
provides two essential nutrients - potassium and sulphur.
- The latter becomes increasingly important in intensively
cropped areas with light-textured soils, high yields and
predominant use of high-grade fertilizers.
- A 'K' content of 7-8 per cent in petioles at the time of
tuber initiation was adequate for the production of maximum
yields.
- MOP generally resulted in higher petiole K levels (9-12
per cent) than did SOP (8-9 percent).
- Specific gravity of tubers was reduced with increasing
rates of K.
- It was lower at MOP than at SOP treatment (Mcdole et
al., 1978).
- Increased K application raised K contents in leaves and
tubers of Potatoes remarkably independent of the K source.
- Raised K contents in leaves and tubers in any case
lowered contents of reducing sugars, total sugar contents
and blackspot of potatoes as well. By this way the quality
of colour of baked chips was improved.
- Raising the K rate from 170 to 306 Kg K2O/ha increased
tuber yields but lowered starch contents.
- Starch contents were lower in the Cl treated plots and
higher in the SOP treated plots (Patletschny and Kick,
1979).
- Industrial food potatoes (chips, crisps) should be
manured somewhat more lightly than general table potatoes
but more heavily than starch potatoes so as to combine the
highest possible dry matter content with the least possible
tendency to undesirable browning (Prummel, J. 1983).
- K - application enhanced the yield of large sized
tubers. (Sadaphal et al. 1973).
- Potassium sulphate as a source of K was comparatively
more effective than MOP in acidic and alluvial soils with
respect to yield and K-uptake.
- Tuber drymatter, starch, total sugars, and ascorbic acid
content were comparatiely higher with SOP than with MOP.
- The beneficial effect of sulphate ion in SOP in acidic
or light textured alluvial soil may be due to sulphur
deficiency in soils (Sharma et al, 1980).
- Although potato is sensitive to excess Cl during early
growth, MOP and SOP give the same yield if the chloride ion
has the time to move.
- For starch production and for chipping / dehydration,
there seems to be an advantage for SOP as shown in Germany,
Japan, Switzerland and USA (Sprott and Storer, 1984).
- No doubt, SOP is more expensive but the extra cost may
will be repaid by the higher quality of the resulting
produce and consequently higher market price while SOP may
also offer the cheapest and most convenient means of
supplying the crop's need for sulphur.
Top |
|