Long term fertilizer Experiments - Effect on Soil Properties and Crop growth

1. LESSONS FROM LONG TERM FERTILISER EXPERIMENTS
Dhakshinamoorthy, M., Santhy, P., Selvi, D., Savithri, P. and T.M.Thiyagarajan
Directorate of Soil and Crop Management Studies
Tamil Nadu Agricultural University, Coimbatore-641 003
The continuously growing population and increasing demand for food call for
greater reliance on agriculture than had ever been witnessed. The mining of nutrients from
soil for ages along with their losses due to erosion and other causes if allowed to continue
would severely limit crop production in the coming years. Fertiliser inputs have
undoubtedly proved to be one of the major components of raising the soil productivity.
The increasing demand for plant nutrients grew by leaps and bounds with the introduction
of high yielding varieties which even under the best possible management cannot be met
from the inherent soil fertility . The present day agriculture all over the world has therefore
become much dependent upon chemical fertilisers to produce more and more from the
shrinking land area.
Since the early days of use of chemical fertilisers there has been some
apprehensions regarding the soil fertility and crop yield being adversely affected by their
prolonged usage. As a sequel to these had come the world's oldest classical manurial
experiments started by Lawes and Gilbert at Broadbalk fields in Rothamsted (England).
The succeeding decades saw permanent manurial experiments being set up in several parts
of the world. India started three such experiments after the Rothamsted model towards the
end of the last and the beginning of the present century at Kanpur (U.P.), Coimbatore
(Tamil Nadu) and Pusa (Bihar) followed by some more permanent field trials at other
locations.
These classical experiments did provide valuable information on the effect of
rotational cropping , use of bulky organic manures, nutrient application alone or in
combinations on crop yields, nutrient uptake and on changes in soil physico - chemical
properties of the soil. The change over of the cropping pattern based on high yielding
technology and multiple cropping and breaking of the age old yield barrier gave new
dimensions to agricultural production strategy in the country. The yield levels and the
nutrient input requirements have gone up several folds with a rapid turnover of the
nutrients in the soil plant systems. Multiple cropping, irrigation and pest control measures,
all directed towards achieving higher levels of production, necessarily have a much greater
impact on soil and crop environment than ever conceived before. It becomes imperative,
therefore, to examine how far the soil, which is one of the greatest natural resources can
be manipulated without seriously damaging the long term viability of the farm on which
the livelihood of all ultimately depends. There is a general agreement that long term
experiments play an important role in identifying the soil constraints that limit crop yields
and help in monitoring the soil conditions so as to protect the crop plants and food chain
from attaining harmful concentrations of various environmental pollutants in the years to

2. come, besides maintaining soil fertility and productivity through suitable soil ameliorative
measures as necessary warrants.
The Indian Council of Agricultural Research sponsored an All India Coordinated
Research Project on Long Term Fertiliser Experiments during the Fourth Plan Period to
examine as to what would happen to soil fertility and productivity on a long term basis
under high input soil management technology. Thus, a new set of statistically designed
field experiments in keeping with the modern intensive system of agriculture were started
at eleven selected centres in 1971. Six more centres were added during 1996 to provide
more wider representations for the major soil-climatic zones of the country.
The treatments adopted at these centres essentially consisted of 50, 100 and 150 %
optimum NPK, 100 % NPK with handweeding , ZnSO4 application @ 25kg ha-1 , S free
sources of NPK fertilisers and FYM @ 10 t ha-1, 100 % optimum NP, 100 % optimum N
and a control. The lessons learnt from these Long Term Fertiliser Experiments will be
discussed in this paper.
RESPONSE IN CROP YIELDS
Balanced application of 100 % NPK with FYM @ 10 t ha-1, produced highest
grain yield response in almost all the soils and cropping systems. However , 150 % NPK
recorded the highest yield response in alluvial soil of Barrackpore and New Delhi and the
red loam of Bangalore and Hyderabad. Among the various cropping systems studied, rice-
wheat rotation followed at Pantnagar on foot hill (Terai) soil produced the highest average
grain yield of the order of 10.7 t / ha / year over the years with an additional output of
about 4 t / ha of cowpea fodder. Similarly, the grain yield under maize-wheat, rice-rice and
soybean-wheat cropping systems averaged from 7.5 to 7.7, 6.9 to 7.5 and 4.1 to 6.5
t/ha/year, respectively. Thus, the importance of balanced NPK nutrition and FYM
incorporation was very much evinced in maintaining yield stability.(Santhy et al., 1998a)
In order to evaluate the net trend in yield over years in each treatment and
crop the average yield in each treatment in each year was related to time in a semilog
function as
Y = at b,
_1
where Y is yield in kg ha , t is the time in months and a and b are constants. A negative b
value is an indication of declining trend and a positive one , for yield sustainability.
The results indicated that in finger millet a declining yield growth over
years occurred in control and 100% N treatment whereas in other treatments the yield
growth was sustainable. In maize sustainable yield growth over years occurred in all
treatments including control. But in grain cowpea the yield growth was sustainable only
in 100% NP, 100% NPK + ZnSO4 and 100% NPK + FYM treatments whereas in other
treatments the yield growth was found to be declining (Table 1).
2

3. Table 1. Temporal effect of Treatments on yield
Treatments Finger millet Maize
a b a b
Control 639 (-) 0.0006 118 0.0103
100% N 916 (-) 0.0010 317 0.0061
100% NP 2392 0.0007 1525 0.0040
50% NPK 2101 0.0015 1212 0.0048
100% NPK 2101 0.0015 1480 0.0045
150% NPK 2416 0.0012 1737 0.0040
100% NPK + ZnSO4 2276 0.0010 1772 0.0035
100% NPK + FYM 2724 0.0011 1920 0.0039
100% NPK + HW 2441 0.0006 1669 0.0037
100% NPK (S free) 2392 0.0006 1604 0.0040
(Murugappan et. al., 1997)
RESPONSE TO NPK
Mean response of rice to N ( kg grain / kg N ) was found to be 18 kg in new
alluvium of Barrackpore, 6 to 10 kg in red loam of Hyderabad, 8 to 14 kg in laterite soil
of Bhubaneswar and 12 kg in Terai soil of Pantnagar. While response of wheat to N was
17 kg at Pantnagar, it was only 4 to 5 kg in medium black and acidic sub-montane soil.
The N failed to give any response in acidic red loam soils(Ranchi and Bangalore). Poor
response to N in medium black and acidic red loam soil was to be due to inadequate
availability of P.
Response to P was found to be very high in acidic red loams (Bangalore and
Hyderabad) medium black soils (Jabalpur and Coimbatore) and acidic sub-montane
(Palampur) soils where P has been found to be one of the major soil constraints limiting
crop production. Response to P in alluvial soils of New Delhi and Ludhiana have been
found to be quite encouraging (8 to 13 kg grain / kg P 2O5 ).
Effect of K on yield was found to be quite high in light alluvial sandy soil of
Ludhiana and red loam of Hyderabad . Increasing response to K was recorded in acidic
red loam, acidic sub-montane, foot hill and even in K rich medium black (Jabalpur) soil
when N and P were not limiting. Response to K was not observed in the mixed black soils
of Long Term Fertiliser Experiments at Coimbatore centre.
3

4. EFFECT OF CONTINUOUS N APPLICATION
Application of N alone had a deleterious effect on soil productivity resulting in
diminishing yields in acidic red loam (Ranchi and Bangalore) and sub-montane (Palampur)
soils where P and K were deficient. Even though the mixed black soils of Coimbatore
centre have medium P and high K status, continuous application of N alone has reduced
the yield to a tune of 70% over 100% NPK in finger millet and maize (Santhy et. al.
1998 b) and Jayasree et. al. 2000). This ensures the importance of P and K in determining
the response to N suggesting the need for balanced nutrition.
EFFECT ON SOIL PHYSICAL PROPERTIES
Bulk Density
Ploughing and cultivation increase soil aeration and the physical disruption caused
by intensive cultivation can result in break down of soil aggregates and produce a tilth that
is very fine and loose. The reduced aggregate stability is associated with increased
porosity and aeration and a decrease in bulk density within the plough depth. Such a
reduction in bulk density was observed due to combined application of 100 % NPK +
FYM in some intensive cropping systems (Table 2).
Table 2. Bulk density of soils (Mg m-3) under intensive cropping systems
Treatments Location/Soil type/Cropping system
Barrackpore Hyderabad Bhubaneswar Pantnagar Coimbatore
Alluvial Red loam Laterite Silty clay Inceptisol
loam
Rice-Wheat- Rice-Rice Rice-Rice Rice- Finger
Jute Wheat- millet -
Cowpea Maize -
fodder Cowpea
fodder
1. 100 % NPK 1.44 1.68 1.63 1.32 1.40
2. 150 % NPK 1.40 1.62 1.55 1.33 1.41
3. 100 % NP 1.41 1.58 1.62 1.29 1.42
4. 100 % N 1.46 1.78 1.61 1.28 1.36
5. 100 % NPK 1.40 1.34 1.56 1.31 1.30
+ FYM
6. Control 1.46 1.53 1.65 1.33 1.44
C.D.(P=0.05) 0.014 0.12 0.08 0.008 0.063
(Anon., 1989 and 1999)
No appreciable changes in B.D. were observed between the uncultivated A2
horizon and the cultivated Ap horizon of an Andisol under long term cultivation in Japan.
This has been attributed to the fact that the depletion of organic matter associated with
cultivation was low (Table 3). The application of 100% NPK with FYM recorded a
4

5. reduced bulk density value of 1.30 Mg m-3 compared to other treatments which could be
ascribed to better aggregation. (Anon., 1999)
Table 3. Effect of cultivation on soil properties
Property Uncultivated A2 horizon Cultivated Ap horizon
Organic C (g.kg-1) 93.9 ± 7.3 81.2 ± 14.2
Total N (g.kg-1) 5.76 ± 0.53 5.46 ± 0.76
C/N ratio 16.3 ± 0.7 14.8 ± 0.9
Bulk density (Mg.m-3) 0.56 ± 0.06 0.61 ± 0.04
(Higuchi & Kashiwagi, 1993 )
Porosity
Soil porosity is influenced by the amount of clay and the arrangement of soil
particles. An increase in clay content is likely to increase the capillary porosity.
Aggregation of soil particles into stable structure is bound to result in the proper
distribution of capillary and noncapillary porosity. Continuous incorporation of cattle
manure increased the porespace in the OPM and NPM experiments at Coimbatore.
Increase in total and noncapillary porosity and a decrease in capillary porosity due to the
continuous incorporation of 100 % NPK have been observed in an intensive cropping
system involving Fingermillet-Maize-Cowpea fodder (Table 4 ).
Table 4. Effect of intensive cropping and continuous fertilisation on soil porosity(%)
Treatment Total porosity Capillary porosity Non capillary porosity
100 % NPK 56.14 38.26 17.87
150 % NPK 56.98 39.47 17.51
100 % NP 52.11 35.76 17.15
100 % N 52.24 34.88 17.36
100 % NPK + FYM 58.85 40.86 20.50
Control 54.18 36.61 17.57
C. D. (P=0.05) 2.04 2.82 2.85
(Anon., 1999)
Hydraulic conductivity
Intensive cultivation results in less organic carbon, low porosity, few water stable
aggregates, a smaller mean weight diameter of water stable aggregates and lower
saturated hydraulic conductivity (Arvidsson and Hakansson, 1996). This is due to the fact
that ploughing largely restores the macroporosity of the soil within the plough layer. A
slight increase in saturated hydraulic conductivity has been observed in Barrackpore
5

6. alluvial sandy loam soil and in Vertic Ustropept of Coimbatore under FYM treatment. But
a reduction in hydraulic conductivity was observed in laterite soils of Bhubaneswar under
FYM treatment due to reduction in non capillary porosity.(Table 5 )
Table 5. Hydraulic conductivity under intensive cropping (cm.hr-1)
Treatments Barrackpore* Bhubaneswar* Coimbatore
Alluvial sandy Laterite sandy loam Inceptisol sandy clay
loam loam
100 % NPK 0.095 3.02 1.81
150 % NPK 0.099 3.00 1.87
100 % NP 0.095 3.02 1.66
100 % N 0.095 3.03 1.73
100 % NPK + FYM 0.106 2.90 2.61
Control 0.088 3.09 1.44
*(Nambiar and Abrol, 1989)
(Anon., 1999)
PHYSICO-CHEMICAL PROPERTIES
Soil reaction ( pH )
Suresh Lal and Mathur (1988) reported that continuous application of fertilisers
for eight years lowered the soil pH. However application of FYM alone had either
maintained or slightly increased the pH but the incorporation of fertilisers with it
decreased the same (Prasad et al., 1983). The rise in pH under FYM treatment was due to
the deactivation of Fe3+ and Al3+ with concomitant release of basic cations (Ca2+,Mg2+ and
K+ ) during its decomposition. They also stated that the pH of the control plot had also
increased after 28 years of continuous cropping. This may be due to the release of HCO 3-1
and OH-1 into the soil solution for the uptake of anions such as nitrate, phosphate,
sulphate, molybdate and borate.
However, no perceptible change in soil reaction was observed in near neutral to
alkaline soils after a decade of intensive cropping and manuring under the ICAR's Long
Term Fertiliser Experiments including Coimbatore centre (Santhy et. al., 1999) (Table 6).
But there was an increase in acidity in acidic red loam soil of Bangalore and Ranchi and
sub-montane soil of Palampur. Maximum acidity was observed in 100 % N treatment, the
effect being more pronounced in acidic red loam soil where urea and ammonium sulphate
were used as N source. The increased acidity may lead to a decline in productivity in acid
soils in the long run.
Electrical conductivity ( EC )
The major source of salts to the soil is irrigation water and wherever the irrigation
water used contains considerable quantities of salts, it will result in increased electrical
conductivity of the soil over the years (Wang and Fang, 1978 ). In general, the electrical
conductivity of the soil does not vary markedly due to long term manurial practices
(Anon., 1979), unless the schedule involves the addition of heavy doses as in the case of
gypsum (Singh and Abrol,1988). Long term application of lime and K to a Typic
Haplustalfs soil increased the soil electrical conductivity where as continuous application
of inorganic fertilisers alone (N, NP and NPK) for 14 years did not change the electrical
6

7. conductivity in a sandy loam soil (Kapur et al., 1986). In the Long Term Fertiliser
Experiments at Coimbatore centre, continuous cropping and manuring did not alter the
soil electrical conductivity to any appreciable extent (Table 6).
Table 6. Effect of intensive cropping on soil physico-chemical properties
Treatments pH Electrical conductivity (dSm-
1
)
50 % NPK 8.1 0.95
100 % NPK 8.2 0.75
150 % NPK 8.2 0.80
100 % NPK + FYM 8.1 0.63
Control 8.1 0.62
CD (P=0.05) 0.05 0.03
(Santhy et. al., 1999)
Cation exchange capacity ( CEC )
The cation exchange capacity of a soil is influenced mainly by the content of
organic matter and clay fraction. Since long term application of manures and fertilisers is
likely to alter the organic carbon status of the soil, significant changes in soil cation
exchange capacity as a result of manurial practices over the years has been quoted in the
past (Krishnamoorthy and Ravikumar, 1973). Continuous application of N and compost to
rice crop in a permanent manurial experiment at Cuttack increased the cation exchange
capacity of the soil (Table 7).
Table 7. Effect of N and compost on CEC of rice soils ( C mol. p + kg-1 )
N levels (kg ha-1) Compost levels ( t.ha-1)
0 9.2 Mean
0 21.6 22.1 21.8
22.4 21.7 22.1 21.9
44.8 21.6 22.9 22.2
67.2 22.2 22.9 22.5
89.6 21.3 22.6 21.9
Mean 21.6 22.5
(Patnaik et al., 1989)
The cation exchange capacity of a sandy loam soil (Typic Ustochrept) was
practically unaffected due to the continuous application of inorganic fertilisers to a fixed
maize-wheat rotation (Kapur et al., 1986 ). Higher CEC was recorded under 100 % NPK
+ FYM in a Long Term Fertiliser Experiment at Coimbatore and this has been attributed
to the build up of humus due to the application of FYM and the presence of higher
amounts of crop residues (Sheeba, 1994).
SOIL NUTRIENT STATUS
Nitrogen
7

8. In a Long Term Fertiliser Experiment at Coimbatore, continuous intensive
cropping was found to have a general depletion in the total N status of the soil. The order
of depletion of soil N reserve with crops in the rotation was found to be Maize > Cowpea
fodder > Finger millet. The available N was also depleted in all plots including the control
due to intensive cropping except in plots receiving 100 % NPK + FYM ( Table 8 ).
Table 8. Total and available N status in a Long Term Fertiliser Experiment(mg kg-1)
Treatments Total N (mg. kg-1) Available N (mg. kg-1)
Finger Maize Cowpea Finger Maize Cowpea
millet millet
Control 288 293 281 62 66 62
100%N 516 509 510 72 71 75
100%NP 516 511 512 77 73 79
50%NPK 434 432 432 73 69 74
100%NPK 523 531 532 76 74 77
150%NPK 553 544 544 77 80 80
100%NPK+ ZnSO4 553 540 541 75 74 77
100%NPK + FYM 664 593 631 92 86 91
100%NPK + HW 490 492 487 77 73 75
100%NPK (S free) 497 486 487 74 72 72
*C.D.(P=0.05) 12.59 5.59
*Treatment Crop interaction effect (Velusamy, 1996)
Cultivation is an oxidative process since it typically promotes good aeration and
consequently promotes rapid decomposition of organic matter and mineralization of
organically bound N. Mineralized N may be denitrified or leached besides fulfilling crop
uptake and this may explain the reasons for depletion of N under intensive cropping.
Crop rotations have been suggested to reduce soil N depletion. Olsen et al.(1970)
found that crop rotation reduced NO3 leaching at a depth of 1.2 to 1.5 m by 34 to 82 per
cent compared to continuous corn. They found that the decrease in solution NO 3 was
directly proportional to the number of years in oats, meadow or alfalfa and attributed this
to the combined recovery of NO3 by shallow rooted oat crops followed by deep rooted
alfalfa crops.
In a Long Term Fertiliser Experiment on sugarcane for 11 years in a slightly acidic
soil, there was a drastic reduction in soil NPK status in the control treatment due to
intensive cultivation . Application of NPK with FYM improved the soil fertility ( Rabindra
and Gowda, 1986). Muthuvel et al.(1977) reported that the available N content was
higher in the organic manure treatment than in the fertilised plots due to optimum
microbial population and quicker mineralization enhanced by FYM application.
Balanced application of NPK at 100 % level reflected in a positive balance of N in
alluvial soil of Barrackpore, Ludhiana and New Delhi , medium black soil of Coimbatore,
red loam soils of Bangalore and Hyderabad, acidic sub-montane soil of Palampur and
8

9. laterite soil of Bhubaneswar. Negative N balance was observed in medium black soil of
Jabalpur, acidic red loam soil of Ranchi and Terai soil of Pantnagar. (Nambiar and Ghosh,
1984)
Phosphorus
In the Old and New Permanent Manurial experiments at Coimbatore, the
plots receiving inorganic P and cattle manure recorded higher available and total P
content. In the Long Term Fertiliser Experiments, considerable build up of P was noticed
in 100 % and 150 % NPK treatments at Barrackpore, Ludhiana and Delhi. Depletion of P
was noticed in 100 % N alone as compared to control, probably due to greater removal of
P for enhanced plant growth brought about by N application. Depletion of P (from the
initial level) after 10 years was 37, 47, and 77 % at New Delhi, Barrackpore and Ludhiana
while it was 37, 42 and 66 %, respectively under control (Nambiar and Ghosh, 1984).
Similar results have been observed at Coimbatore centre. The P reduction in the soil was
for a continuous addition of N alone was from 490 to 423 ppm in total P and 4.92 to 2.00
ppm in available P over a period if 20 years in the medium black soils of Coimbatore
(Jayasree et. al., 2000).
Potassium
In ongoing Long Term Fertiliser Experiment at Coimbatore centre, continuous
cropping even with the recommended dose of NPK + FYM had a declined on total as
well as available K status of the soil. The depletion was of high magnitude in situation
were no K additions were done (Murugappan et. al., 1999). The non exchangeable K
generally showed a declining trend indicating the role of this form of K in meeting the crop
requirement when the soil available pool remains constantly under K stress. The total K
also showed a declining trend with the progress in the number of crops, as a result of K
removal by the crops which far exceeded the fertiliser K input into the soil. The available
K also decreased due to crop uptake over and the quantity of fertilisers applied (Table 9).
Table 9. Content of K fractions in soil under Long Term Fertiliser Experiments
(mg. kg-1)
Treatments Water Exchange- Nonexcha Lattice-K Total K Available-
soluble-K able K ngeable-K K
50 % NPK 16 215 813 2621 3685 238
100 % NPK 20 231 899 2620 3788 255
150 % NPK 24 244 1036 2620 3939 273
100 % NP 7 108 514 1621 3275 127
100 % N 10 126 707 2627 3485 139
100 % NPK 23 254 971 2618 3890 281
+ FYM
Control 12 183 813 2643 3665 198
CD(P=0.05) 1 13 80 NS 89 13
(Santhy., et al.,1998b)
9

10. Similar results indicating a depletion in available K under intensive cropping had
been observed by Nambiar and Ghosh (1984 ).
Organic matter
Organic matter is the centre of nearly all life activities in the soil. It serves
as a source of food for microflora, fauna and other living matter in the soil. Long term
recycling of crop residues can improve the organic matter content of soil as a result of
increased dry matter production( Bhat et al., 1991). The rotation which included only a
cereal crop gave only a lower organic matter status as against a rotation with a green
manure or legume crop( Havanagi and Mann, 1970 ; Campbell et al., 1991). The organic
matter is higher under continuous cropping than under fallow ( Jansen, 1987 ). The results
of 15 years of Long Term Fertiliser Experiments at Ludhiana, Hyderabad, Bhubaneswar,
Palampur and Coimbatore showed that organic matter levels increased due to intensive
cropping ( Nambiar and Ghosh, 1984).
Secondary and micronutrients
A decrease in exchangeable Ca and Mg by fertiliser additions but increase
under FYM treatment had been observed by several workers(Prasad and Singh, 1981 ;
Suresh Lal and Mathur, 1988; Patiram and Singh, 1993 ).The results of Long Term
Fertiliser Experiments from Barrackpore, Bhubaneswar and Coimbatore centres have
shown that the available S content was decreased due to intensive cropping especially
when S free fertilisers were added. Addition of S containing fertilisers and FYM with 100
% NPK maintained or improved the S status of the soil ( Nambiar and Ghosh, 1984). A
steep decrease in DTPA-Zn over years due to intensive cultivation of Coimbatore centre
was observed (2.58 to 0.90 mg kg -1). However the ZnSO4 application @ 25 kg ha-1 to
maize alone resulted in an increase in the available Zn status of the soil (2.86 mg kg -1)
(Selvi et. al., 2000). Zinc deficiency symptoms were not observed at Barrackpore even
after the 14th crop cycle ( Anon.,1989). Prasad et al.(1994) observed a similar pattern of
depletion of micronutrients under continuous maize - wheat rotations.
The biomass C, N and P were all found to be the highest for the content
application of 100% NPK + FYM. The activity of phosphorus enzyme was higher for the
intensive application of 100% NPK + FYM which was on par with 150% NPK (Santhy,
et. al., 2000). The biomass C : N ratio was narrower in the case of 100% NPK + FYM
and wider in unmanured control than 100% NPK. Depletion of P and K widened the
ratio in case of 100% N application (Selvi, et. al., 2000).
CONCLUSIONS
The data collected from experiments conducted over a period of 30 years indicated
little response to N fertilizer in the absence of P application on Vertic Ustochrepts
(Coimbatore) and Chromusterts (Jabalpur). Application of N fertilizer alone had a
deleterious effect on crop yields on both Haplustalfs (Ranchi) and Hapludalfs (Palampur),
and the crop yields in respect of N treatment were lower than the yields from unmanured
plots. The yield of crops appreciated markedly with the application of P fertilizer in
10

11. combination with N, which showed further improvement with balanced use of N, P and K
fertilizers. The integrated use of organic manures and chemical fertilizers was found to be
quite promising in maintaining stability in crop production through correction of marginal
deficiencies of secondary and micronutrient elements in the course of mineralization on the
one hand and providing favourable physical and soil ecological conditions on the other.
The deteriorating productivity was found to be associated with the imbalance in secondary
nutrients like S and micronutrients like Zn. The original productivity could be restored
with the application of nutrients which were otherwise yield-limiting. The role of S in
maintaining productivity was more marked in respect of certain crops than others in the
multiple-cropping systems. Its effect was more marked on kharif rice on both
Eutrochrepts (Barrackpore) and Haplaquepts (Bhubaneswar) after 2 and 3 annual
cropping cycles, respectively, as the available soil-S (Morgan’s-extractable S) dropped to
around 4 mg kg-1 soil.
No perceptible change in soil pH was observed over the years (1971-99) in respect
of soils with neutral to alkaline in reaction but the soil pH decreased by 0.9 - 1.0 from the
initial values on both Haplustalfs (Ranchi) and Hapludalfs (Palampur) under N treatment.
However, incorporation of farm yard manure along with NPK fertilizers showed some
moderating effect on soil pH. Appreciable improvement in soil organic carbon over the
initial level was noticed at optimal to superoptimal (100-150%) NPK doses on almost all
the soils except on Hapludolls (Pantnagar), Eutrochrepts (Barrackpore) and Haplustalfs
(Ranchi), where considerable reduction in organic carbon was noticed. However, the
initial level of organic carbon was maintained with NPK + FYM treatment.
The available soil-N improved appreciably at optimal to superoptimal (100-150%)
NPK doses over the initial levels on almost all the soils. It declined to a very low level in
unmanured plots. The available soil-P at optimal to superoptimal (100-150%) NPK doses
was raised from low to high status on Chromisters (Jabalpur), medium to high on
Ustochrepts (Delhi), Haplustalfs (Ranchi), Hapludolls (Pantnagar) and Vertic Ustropept
(Coimbatore), high to very high on Eutrochrepts (Barrackpore) and Haplustalfs
(Palampur) and low to very high on Ustochrepts (Ludhiana). An appreciable build-up in
the available soil-K (N NH4Oac-extractable K) was noticed even at the optimal (100%)
NPK dose on Ustochrepts (Ludhiana and Delhi) and Haplustalfs (Ranchi) and it was at
superoptimal (150%) NPK dose on Hapludalfs (Palampur) and Hapludolls (Pantnagar).
However, available soil-K declined over the years on Vertic Ustropepts (Coimbatore),
Chromusterts (Jabalpur) and Tropaquepts (Hyderabad) even at superoptimal NPK dose,
indicating considerable soil mining of its available K. The highest depletion in available
soil-K was noted under NP treatment. Incorporation of farm yard manure (along with
optimal NPK dose) improved soil physical properties like bulk density, total porosity and
hydraulic conductivity over other treatments.
REFERENCES
Anonymous. 1989. Annual Report of the AICRP on Long Term Fertiliser Experiments,
ICAR, New Delhi.
11

12. Anonymous. 1999. Annual Report of the AICRP on Long Term Fertiliser Experiments,
TNAU, Coimbatore.
Aravidsson, J. and I. Hakansson. 1996. Do effects of soil compaction persists after
ploughing? Results from 21 long term field experiments in Sweden. Soil Tillage
Res. 39: 175-197.
Bhat, A.K., V.Beri and B.S. Sidhu. 1991. Effect of long term recycling of crop residues
on soil productivity. J. Indian Soc. Soil Sci. 39: 380-382.
Campbell, C.A., K.E.Bowren, M.Schnitzer, R.P.Zentner and L.T.Smith. 1991. Effect
of crop rotations and fertilisation on soil organic matter and some biochemical
properties of a thick black chernozem. Can. J. Soil Sci. 71: 377-387.
Havangi,G.V and H.S.Mann. 1970. Effect of rotations and continuous applications of
manures and fertilisers on soil properties under dry farming conditions. J.Indian
Soc.Soil Sci., 18 : 45 - 47
Higuchi , T. and S. Kashiwagi. 1993. Changes of Soil Morphological Characteristics
and Organic Matter Content after Long Term Cultivation in Andisols on the
Musashino Plateau, Japan. Soil Sci. Plant Nutr. 39(1):89-97.
Jansen, H.H. 1987. Soil organic Characteristics after long term cropping to various
spring wheat rotations. Can. J. Soil Sci. 67: 845-856.
Jayasree Sankar, P.Santhy, P.Muthuvel and V.Murugappan. 2000. Land
degradation due to P depletion under intensive cropping. Agropedology. 10(1) :
34-39.
Kapur, M.L., N.C. Talukdar and D.S. Rana. 1986. Influence of continuous application
of inorganic fertilisers in a maize wheat rotation on some soil chemical properties.
J. Indian Soc. Soil Sci. 34: 198-199.
Krishnamoorthy, K.K. and V.Ravikumar. 1973. Permanent Manurial Experiment
conducted at Coimbatore. TNAU Publication , Coimbatore.
Murugappan, V., P.Santhy, D.Selvi and Rani Perumal. 1997. Long Term Fertilizer
Experiment on an Inceptisol with high intensive cropping - High lights of two
decades of Research. Technical Bulletin, TNAU, Coimbatore. pp:1-84.
Murugappan, V., P.Santhy, D.Selvi, P.Muthuvel and M.Dhakshinamoorthy. 1999.
Land degradation due to Potassium mining under high intensive cropping in semi
arid tropics. Fert. News. 44 (5) : 75-77.
Muthuvel, P., P. Kandasamy and K.K. Krishnamoorthy. 1977. Availability of NPK
under long term fertilisation. Madras Agric. J. 64: 358-362.
Nambiar, K.K.M. and I. Abrol. 1989.Long Term Fertiliser Experiments in India- An
overview. Fert. News. 34(4): 11-20.
12

13. Nambiar, K.K.M. and A.B. Ghosh. 1984. Highlights of research on Long Term
Fertiliser Experiments in India. LTFE Res. Bull. 1.,ICAR,New Delhi.
Olsen, R.J., R.F.Hensler, O.J.Attoe, S.A.Witzel and L.A. Peterson. 1970. Fertiliser N
and crop rotation in relation to movement of NO 3-N through soil profile. Soil Sci.
Soc. Am. Proc. 34: 448-452.
Patiram and K.A. Singh. 1993. Effect of continuous application of manures and N
fertiliser on some properties of acid Inceptisols. J. Indian Soc. Soil Sci. 41: 430-
433.
Patnaik, S., D. Panda and R.N.Dash. 1989. Long Term Fertiliser Experiment on wet
land rice. Fert. News. 34(4):47-52.
Prasad, B. and R.P.Singh. 1981. Accumulation and decline of available nutrients with
long term use of fertilisers, manures and lime on multiple cropped lands. Indian J.
Agrl. Sci. 51: 108-111.
Prasad, B., R.P.Singh, H.K. Roy and H.Sinha. 1983. Effect of fertilisers, lime and
manure on some physical and chemical properties of a red loam soil under multiple
cropping. J. Indian Soc. Soil Sci. 31: 601-603.
Prasad., B.C., Biswas and R.K.Tewatia. 1994. Nutrient depletion and agriculture
sustainability in Punjab. Fert. News, 39: 11
Rabindra, B. and H. Gowda. 1986. Long range effect of fertilisers, lime and manures on
soil fertility and sugarcane yield on a red sandy loam soil. J. Indian Soc. Soil Sci.
34 : 200 - 202.
Santhy, P., P.Muthuvel, V.Murugappan and D.Selvi. 1998 a. Long term effects of
continuous cropping and fertilization on crop yields and soil fertility status. J.
Indian Soc. Soil Sci. 46 (3) : 391-395.
Santhy, P., S. Jayasree Sankar, P.Muthuvel and D.Selvi. 1998 b. Long Term Fertiliser
Experiments- status of N, P and K fractions in soil. J. Indian Soc. Soil Sci. 46 (3) :
395-398.
Santhy, P., M.S.Velusamy, V.Murugappan and D.Selvi. 1999. Effect of Inorganic
Fertilizers and Fertilizer - Manure combination on soil physico-chemical properties
and Dynamics of Microbial Biomass in an Inceptisol. J. Indian Soc. Soil Sci. 47 (3)
: 479 - 482.
Santhy, P., D.Selvi, M.Dhakshinamoorthy and K.K.Mathan. 2000. Microbial
biomass P, labile P and phosphatase activity under intensive cultivation in Long
Term Fertilizer Experiment. pp.3. Proceedings of the National Seminar on
Environmental awareness, education and management for sustainable rural
13

14. development held at Sri Venkateswara University, Tirupati, during Aug. 24 - 26,
2000.
Selvi, D., P.Santhy, M.Dhakshinamoorthy and K.K.Mathan. 2000. Long Term
application of organic and inorganic fertilisers on micronutrient status, biomass
carbon and biomass nitrogen in an Inceptisol. pp.5. Proceedings of the National
Seminar on Environmental awareness, education and management for sustainable
rural development held at Sri Venkateswara University, Tirupati, during Aug. 24 -
26, 2000.
Singh, S.B. and I.P.Abrol. 1988. Long term effect of gypsum application and Rice-
Wheat cropping on changes in soil properties and crop yield. J. Indian Soc. Soil
Sci. 36: 316-319.
Sheeba, 1994. Effect of long term fertilization on soil physico-chemical properties.
M.Sc.(Ag.) thesis submitted to the Department of Soil Science and Agricultural
Chemistry, TNAU, Coimbatore-3.
Suresh Lal and B.S.Mathur. 1988. Effect of long term manuring, fertilisation and liming
on crop yield and some physico-chemical properties of acid soil. J. Indian Soc.
Soil Sci. 36 : 113-119.
Velusamy, M.S. 1996. Studies on sustainability of soil fertility due to continuous
application of fertilisers. M.Sc.(Ag.). Thesis, TNAU, Coimbatore.
Wang, C.C. and I.J. Fang. 1978. The effect of long term application of hog wastes on
the soil properties of TSC's sugarcane fields. Taiwan Sugar. 25: 196-204.
14