Agric.Re~,23(2):
110-126,2002
SALT-AFFECTED SOILS AND THEIR MANAGEMENT
FOR SUSTAINABLE RICE PRODUCTION KEY MANAGEMENT ISSUES : A REVIEW
R. Chhabra
Division of Soil and Crop Management,
Central Soil Salinity Research Institute, Karnal-132001, India
ABSTRACT
Rice is a major cereal crop of India and many other countries in the world. Reclamation of
2.359 m ha alkali soils out of 8.373 m ha of salt-affected soils holds promise for an additional
area to inc.rease rice production in developing countries like India. A package of practices consisting of proper on farm development, application of amendments, appropriate agronomic practices
including fertilizer application have been evolved to get 4 to 7 t ha- 1 of rice in alluvial alkali soils.
To maintain productivity of salt-affected degraded soils it is important to manage these soils in
such a way so as to prevent their resodication, sustain their physical and chemical properties and
fertility status. Due to low use of fertilizers and organic manures, and imbalance application of
nutrients there is a decline in fertility of reclaimed alkali soils. Post-reclamation management of
nutrients in these soils is very crucial to sustain rice production. A major part of the rice growing
area is suffering due to declining water table affecting yields and escalating costs of pumping
groundwater from deeper depths. Changes in agronomic practices like banning of summer rice,
delayed transplanting and better management of irrigation water are required to save groundwater, arrest falling water table and to prevent deterioration in its quality. Storing rainwater in the
existing paddy fields and allowing it to seep through the soil is a natural, viable and practical
solution for recharging the groundwater. Irrigation should be so planned as to avoid water stress
in rice during its reproductive growth phase to minimize sterility.
To provide for an increasing population of an estimated 1000 million, India has to
increase its grain production manifold. Assured
irrigation and an increased area under irrigation from 22.6 million ha in 1950-55 to 99.3
million ha by the end of the 8th Five Year Plan
(1992-97), greater and balanced use of fertilizers, integrated pest management and development of high yielding varieties have helped
in increasing its grain production from 195.48
million tons during 1989-91 to 223.01 million tons in the year 1997 (FAO, 1998). Rice
alone has contributed more than 55% of the
total cereal production (Table 1). It must be
emphasized however, that area under rice has
not increased during this period, remaining
static at 42 million ha. Considering the limitation of these methods and pressure on good
land for other uses, there is a limited possibility to further increase rice production. Hence
soils, which were earlier considered unsuitable
for agricultural production, have to be reclaimed
E-mail address: [email protected]
and managed in such a way so as to provide
additional area for increasing food production
in the country. It is estimated that salt-affected
soils occupy nearly 7 per cent of the world land
area (Dudal and Purnell, 1986). Massoud
(1974) estimated this area as 932 million ha,
of which 316 million ha are in the developing
countries. Based on the estimates prepared by
Singh (1992), out of 8.373 million ha of saltaffected soils in India, 2.359 million ha are alkali, 3.829 million ha are saline while the remaining 2.185 million ha are coastal saline
soils. In India these soils are mostly found in
the states of Uttar Pradesh (U.P.), Haryana,
Punjab, Madhya Pradesh (M.P.), Bihar, Andhra
Pradesh (A.P.), West Bengal, Orissa and Tamil
Nadu. These soils, hitherto considered as wastelands, have a potential to increase area under
rice, wheat and other crops. Recent scientific
innovations have made it possible to reclaim
large areas of these degraded soils for increasing grain production in India.
111
Vol. 23. No.2. 2002
Table 1. Area and production of cereals and rice in India.
Year
Total area harvested. m ha
Total cereal production, m t
Area under rice, m ha
Rice production, m t
1989-91
1995
1996
1997
102.27
195.48
42.50
111.29
100.18
214.36
42.91
119.44
100.00
217.98
42.80
121.81
9993
223.01
42.20
123.01
Further, in canal command areas about
2.46 million ha which were earlier under dry
land agriculture have turned waterlogged and
have to be used for raising low land crop such
as rice. This study looks into various key issues
related to the management of degraded soils
for increasing rice production on a sustainable
basis.
Alkali soils
Alkali soils also known as sodic or solonetz soils have a pH of the saturation paste
more than 8.2, exchangeable sodium percentage (ESP) more than 15 and soluble salts,
mostly carbonates and bicarbonates of sodium.
capable of alkaline hydrolysis (Abrol et al,
1980). The electrical conductivity of saturation
extract (ECe) of the.;e soils is variable. Chemical characteristics of a representative alluvial
alkali soil are given in Table 2 (Bhumbla et al ,
1973). The saturation extract though contains
CI and 5°4 ions yet Na/CI+S0 4 is always more
than one. These soils contain 2 to 4 % amorphous CaC03 in the surface and a hard pan,
mainly dolomite, of variable thickness and
depth below the surface. The zone of calcic
horizon possibly indicates the zone of shallow
water table fluctuations.
Table 2. Chemical characteristics of an alkali soil in the alluvial region -Kamal Haryana, India.
Depth,
cm
o -10
10 -48
48 -76
76- 104
104-163
pHs
10.6
10.2
9.8
9.5
9.6
ECe, CaCO J , ESP
dSm I <2mm, 'X,
22.3
6.3
4.2
2.3
1.3
5.1
8.9
9.4
12.6
13.8
96
91
88
85
69
Composition of saturation extract, me Ll
Na
248.3
81.9
49.1
25.3
12.3
Ca
0.7
1.0
0.7
1.0
1.0
Mg
0.2
0.2
0.2
0.5
0.5
K
0.4
0.1
0.1
0.1
0.1
CO)
141.6
56.4
26.8
5.6
3.8
HCO J
136.2
20.4
19.6
7.4
7.8
Cl S0.
6.6 3.9
2.8 1.7
0.8 1.1
1.4 0.6
0.3 0.5
Problems associated with these soils
• Antagonistic effect of high Na on K
for raising rice crop are high pH, high ESP,
nutrition.
high concentration of soluble C0 3 , HC0 3 and
Poor physical conditions leading to low
low amounts of organic matter (O.M.). A com- infiltration rate and poor air permeability, tobination of these factors leads to:
gether with a monsoon type of climate, make
these soils ideal for rice cultivation but unfit for
• Direct toxicity of excess Na.
• Low concentration of soluble and raising other crops. Rice is the major crop with
rice-berseem
(Trifolium
exchangeable Ca causing its nutritional rice-wheat,
alexandrinum)
,
rice-mustard,
rice-barley
and
deficiency.
rice-vegetables
as
important
rotations.
• Deficiency of available micronutrients (Zn,
Fe, Mn) due to their low solubility as a
Advantages of raising rice crop in
result of high pH and immobilization due alkali soils: Despite their low air and water
to high concentration of C0 3 and HC0 3 . permeability, alkali soils are suitable for grow• Low efficiency of applied N due to higher ing rice as the former do not adversely affect
its yield. Further, rice is relatively tolerant to
volatilization losses.
112
AGRICULTURAL REVIEWS
high amounts of exchangeable Na. up to ESP
50, and hence can be raised even after adding
lower doses of amendments. Rice once established also helps in reclaiming alkali soils
. f'Ie Id t n-.
(Chh aora an dAb ro I. 1977) . Ext ensIVe
als have shown that no other cereal crop can
be raised under such adverse physical and
chemical conditions of soils. In addition to the
good quality groundwater available in these
areas, monsoon rains help in meeting to a substantial degree, the irrigation needs of this crop.
These soils have been reclaimed by application of amendments like gypsum and are being extensively cultivated for raising rice, wheat
and a number of other crops. Approximately
1. 1 million ha of such soils have been reclaimed
in the states of Haryana. Punjab and Uttar
Pradesh and are contributing about 10 million
tons of food grains annually to the national
basket.
Issues related to sustain rice yield in aIkali soils
Though alkali soils, on reclamation,
are highly suitable for low land rice yet to
achieve and sustain higher yields these soils
face the following constraints:
.
.
.
..
1"Changes In SOli physIcal condItIOns:
On. a~p !Cation of gyp:um ESP ~ec~eases,
whlc.h Improves the ?h~slca.1 propert1e~ hke dlspersIan and water mflltratlon rate (FIg. 1) of
alkali soils (Chhabra, 1996). While in barren
alkali soils the applied water stays on the surface for 3 to 7 days because of low permeability, it disappears within one or two days when
these soils are reclaimed, adversely affecting
rice crop, which requires standing water for its
optimum growth. With time when them is a
decrease in soil pHI ESP of the surface as well
as of lower layers, there are serious losses of
applied water through deep percolation. Thus
while in the initial few years there is .no need
to puddle the soil, this practice becomes necessary to cut down percolation losses during
rice cultivation in the reclaimed alkali soils.
I
6
\,
5
':>,
\
III
"0
E
u
~
13
III
OJ
E
"-
4
\
\
3
OJ
Q.
"-
.2::
III
2
3
\
\
\\
...
"'-"
'''-.,.
I
o
!
10
I
20
I
30
""......
I
40
...... -...1
50
1.
60
I
70
I
80
90
Exchangeable sodium percentage
Fig. 1.
Water permeability of an alkali soil as affected by exchangeable sodium percentage,
:00
Vol. 23, No, 2, 2002
However, it should be clearly understood that despite improvements, reclaimed alkali soils continue to differ from the normal
non-alkali soils of the area for a long time to
come, They continue to suffer from stagnation of water on irrigation or on heavy rainfall
causing short duration waterlogging for wheat
and other arable crops, The lower layers of
these soils get compacted due to clay movement and pose resistance to root development
and water movement.
High pH/ESP leading to decrease
in yield: Though rice is relatively more tolerant (Fiq, 2) to soil exchangeable sodium (Abrol
113
and Bhumbla, 1979) than other cereal crops
(Table 3, Chhabra, 1996) yet high pH (> 9.5)
and high ESP (>50) is detrimental to its optimum growth, In these highly deteriorated soils,
even for salt tolerant rice cultivars (Table 4),
yield increases with an increase in application
of amendment (Mehta, 1996), though the significant response is limited to gypsum level
equivalent to 50% of gypsum requirement
(GR), Hence these soils must be chemically
ameliorated by application of amendments to
bring ESP within the threshold value for growing rice,
8
.'
•
••
6
'co
•
"
•
•
•
•
--.--------.
. • -------..........
• -----...
•
•
.c
'\
c
'iii
4
"
21
0
•
'~
~
's,
>(J
Rice
2C
I
4C
I
I
60
BO
-'- ~
•
\
•
I
100
ESP
Fig, 2,
Effect of ESP on yield of unhusked rice,
Grain yield of both rice and wheat
crops increases with an increasing level of gypsum application from 0 to 50 11\) GR (Table 5),
While for rice gypsum application @ 25% GR
is enough, for wheat increasing the amount to
50% GR is necessary to get optimum yields.
Application of FYM @ 20 t ha- 1 alone is inferior to gypsum, but when combined with gyp-
sum, it gives higher yield than gypsum alone
and hastens reclamation of soil (Swaroop and
Singh, 1993), Application of FYM as an
amendment is ecorlOmical when it is available
locally with the farmer and is free of cost., When
it is·to be purchased then it is not economical
as compared to application of gypsum alone.
114
AGRICULTURAL REVIEWS
Table 3. Relative tolerance of crops and grasses to soil ESP.
Tolerant
ESP, 35-50
Moderately tolerant
ESP, 15-35
Kamal grass (Leptochloa fusea)
Rhodes grass (Chloris gayana)
Para grass (Brachiaria mutica)
Bermuda grass (Cynodon dactylon,
Rice (OlJlza sativa)
Dhaincha (Sesbania aculeata)
Sugarbeet (Beta vulgarisj
Teosinte (Euchlaena maxicana)
Table 4.
Sensitive
ESP. <15
Wheat ( Triticum aestivurri}
Barley (Hordeum vulgare,
Oat (Avena sativa)
Shaftal ( Trifolium resupinaturri}
Lucerne (Medicago sativa)
Turnip (Brassica rapa)
Sunflower (Helianthus annusj
Safflower (Carthamus tinctoiusj
Berseem ( Trifolium alexandrinum)
Linseed (Unum siuqatissimuni)
Onion (Allium cepa)
Garlic (Allium sativum)
Pearl millet (Penisetum typhoitesj
Cotton (Gossypium hirsutuni)
Gram (Cicer arietinuni)
Mash (Phaseolus mungq
Chickpea (Cajanus cajan,
Lentil (Lens eseulentliJ
Soybean (Glycine max)
Groundnut (Arachis hypogaeliJ
Sesamum (Sesamum orienta~
Mung (Phaseolus aureusj
Pea (Pisum saccharaturri}
Cowpea ( lhgna unguiculata)
Maize (Zea maysj
Cotton (Gossypium hirsutuni)
Effect of graded levels of gypsum on the yield of rice (c.v. CSR-13)
in an alkali soil of Uttar Pradesh, India.
Amount of gypsum added,
o
7.5
15.0
30.0
45.0
Initial soil pH=10.32,
Table 5.
Grain yield,
t ha- l
°/" GR
thai
o
o
1515
30.30
60.60
90.90
0.390
1.128
2.552
2.603
GR= 49.5 t ha- '
Effect of gypsum levels and FYM on the yield of rice and wheat in an alluvial alkali soil.
Treatments
Grain yield, t ha- 1
1st year
Control
Gypsum @ 25 'X, GR
Gypsum @ 50 % GR
FYM @ 20 thai
Gypsum @ 25 % GR +
FYM @ 20 thai
Gypsum @ 50 % GR +
FYM @ 20 thai
LSD at P=005
Initial pH=10.4,
After three years
2nd year
3rd year
pH
ESP
Rice
Wheat
Rice
Wheat
2.98
5.10
5.44
4.05
5.78
0.20
1.67
1.99
1.42
2.14
4.55
5.23
5.46
5.20
5.76
1.00
2.30
2.30
2.00
2.80
20
5.30
5.30
5.30
5.80
1.20
2.30
2.40
2.20
2.80
9.5
9.2
9.1
9.3
9.1
55
48
42
56
38
6.13
2.36
6.01
2.80
5.90
2.90
9.0
:F)
0.33
0.35
0.41
0.36
0.40
0.34
ESP=89.
Rice c.v. Jaya,
Rice
Wheat
Wheat c.v. HD 2009.
A package of practices consisting of
proper on farm development Le. bunding and
land shaping, use of a higher number of seedlings per hill, closer plant spacing, use of older
seedlings (35 to 45 days instead of 21 days
old), incredsed application of fertilizer-N and a
proper dose of zinc sulphate have been evolved.
Following these practices it is possible to produce an average 6 tons of paddy and 4 tons of
wheat hal in alluvial alkali soils (Fig. 3).
115
Vol. 23, No.2, 2002
Rice
-
III
.c
:!i
's.
6
5
Q)
t:
.~
4
c.J
2
4
6
8
10 12 14
16
IS 20
Cropping years
Fig. 3. Grain yield of rice and wheat in fertilized plots ( N120 ,P22 , K50 .Zn5)
in a gypsum amended alkali soil over a period of 20 years.
any repeated problem of high pH and ESP
.(Chhabra and Thakur, 2000) for raising rice
crop. Surface application of amendments accompanied by leaching, and continuous cropping with high water requiring crops keeps a
downward flux of the replaced Na salts and
with time pushes these well below the active
root zone. As a consequence of that pH of the
surface 15 soil stabilizes around 8.2 to 8.5 (Fig.
4). During the initial years, only surface soil is
reclaimed and depending upon the amount of
amendment added, leaching done and the internal drainage, the lower layers take time to
reclaim. But after 8 to 10 years. almost the
whole soil profile to a depth of one meter gets
reclaimed and attains an ESP <15 (Fig. 5). Use
of lower doses of gypsum than recommended
levels, prolonged fallowing, change to low water requiring crops, flooding from the outside
area, deterioration in groundwater quality being used for irrigation and a rise in water table
Alkali soils once reclaimed do not pose can result in a return of leached salts causing
Evolution of high salt tolerant varieties (Mishra and Singh, 2000) like CSR 1, CSR
2, CSR 3 CSR 10, CSR 13 and CSR 27, have
made it possible to get a moderate to good
crop of rice with relatively less amount of gypsum application (up to 25 % GR). Amelioration of alkali soils through the use of salttolerant rice varieties alone (without or with
less amount of amendments), referred as biological reclamation is another possibility for resource constrained farmers. However, this
method is slower and because of high soil pHI
ESP in the initial years promotes leaching losses
of phosphorus from the surface layers (Chhabra
et aJ., 1981), higher volatilization losses of N
resulting in lower efficiency of applied fertilizers (Bhardwaj and Abrol, 1978) and less availability of applied Zn (Singh et al, 1987). It
also deprives the farmers from growing moderate and sensitive crops following rice, and
thus is not economical over time.
116
AGRICULTURAL REVIEWS
resodication, These factors may necessitate a health (Chhabra and Kamra, 2000) for susrepeat application of gypsum to restore soil taining crop yields,
9-5
9-0
8'5
:r:
0.
~k>-'C'I~
8<>'7'5
('0 -
1:
L-l
R 'II
L.-l
W H W
R
2
L..11
R W RW
~
4
3
I
I JJ I
1....JU--J
RwRWRW
10
15
20
Years of cropping
Fig. 4.
Changes in pH of surface 15 cm soil as affected by rice-wheat cropping sequence
in a gypsum amended alkali soiL
ESP
20
0
t
:
15l-i
.
I
40
1
60
80
I
1
./
.
E
.c
15.
Cll
-0
~
.I
\..
90l105 I-
120
I
\..
60
75
Fig. 5.
.
i.
45
\
•
/
30~t
u
100
\...
\.
I
•
1
•_ .
Original
0
o
Xi
K After 4
u
... After 8
II
.• AfterI5
tl
..
.. _
After 1 )'eOl
I
Improvement in soil ESP over a period of time as a result of rice-wheat cropping in an alkali soiL
Vol. 23, No.2, 2002
Judicious use of irrigation water to arrest
decline in water table
Rice is cultivated as low land paddy in
alkali soils of north India. A major portion of
irrigation is met through rainfall and rest is
supplemented by tube wells or canals. Sharma
(1999) reported that due to over use of groundwater through tube w~lls, the water table in
these areas is falling continuously (Fig. 6). This
has led to low availability of groundwater and
117
also higher cost of pumping from deeper
depths. It is estimated that about 100 to 150
.cm of irrigation water (depending upon the ecological zone) is required to raise a successful
crop of rice. During initial periods of rainfall.
maximum amount of rainwater is either.used
for crop production or stored in soil while during peak rainfall P2riod a substantial part ot it
is lost through deep percolation and/or through
surface runoff.
Fig. 6. Rise and fall of water table, em/year, from 1974-94 in different districts of Haryana, India.
When one considers the water balance
(Fig. 7) during raising of a paddy crop in an
alkali soil, in a state like Haryana, it is observed
that there is a serious deficit in rainfall in meeting the water requirement of crop during early
growth and near maturity. It is compensated
through groundwater (tube wells) o.r canal water. Since it is a large fraction of the total
amount required and when tube well water is
the main source, it results in a big depletion of
groundwater causing decline in water table in
most of the rice growing areas. As a re.sult of
AGRICULTURAL REVIEWS
118-...
this, the fanners have to spend more money
to pump out water from deeper depths and
also risk the exposure- to the dangers of poisonous gases accumulated in the tube well pits
(Chhabra, 1988). To avoid such a situation, it
is important that agronomic strategies must be
evolved to mJnimize the irrigation needs of rice
and to conserve groundwater. Fewexperiments
have been conducted to see if irrigation water
can be saved by restonng to deficit irrigation
instead of continuous ponding as is thE! practice in many states. Singandube (1986) showed
that in alkali soils as much as 18 cm of irrigation water can be saved if it is given one day
after the disappearance of ponded water with
out any significant loss in grain production
(Table 6). A further saving of 35 cm water can
be achieved with only 13 % decrease in grain
production.
.
~ ~infQlf
0---0 Pohtl'ltiGI lIVOP-:ltronlfli:"Vtfllr.
• _ . 4ctUof noporation
90
Tron*p:Qr.f
.~
30
Fig. 7.
32
[[I]JJ]
r;:'; :.,;]
SUrpllJS rainMlttr
e:qz
Sui' waTer lrtt'il!~i~"
34
Vlflfer d.fieft
36
.38
Standard weeks
June
July
August
September
Water balance for rice duiing growing season in an alkali soil in Haryana, India.
40
Table 6. Effect of deficit irrigation on yield", water use efficiency and amount of water saved
Treatments
during rice cultivation in an alkali soil in Haryana, India
Yield, t· ha·1
Amount of
Grain
Straw
water given,
Continuous submergence,S ±2cm
Irrigation, 7 cm after 1 day of
disappearance of ponded water
Irrigation, 7 cm after 4 days of
disappearance of ponded water
LSD at P=0.05
. "Mean of three years "" Includes rainfall
4.70
4.52
6.25
5.85
em··
100
82
4.26
5.34
65
0.27
0.56
Initial pH=9.3
Water use Amount of
efficiency
water
saved; cm
47.0
55.8
18
65.7
35
Vol. 23, No.2, 2002
Sharma (2000) observed that 32.5
and 46.3 cm of water, amounting to 40 and
57% of the irrigation to be met from the
groundwater or canal water, can be saved if
instead of continuous ponding, water is applied
after 3 and 6 days of disappearance of the
ponded water, respectively to a rice (c.v. Jaya)
crop raised in an area with problem of RSC
(Table 7). In such areas deficit irrigation not
119
only saves the amount of water but also prevents the deterioration of the soil which otherwise will be adversely affected by higher use of
such waters. Not only saving of water but the
grain yield and water use efficiency was also
more when irrigation was applied after 3 days
of disappearance of ponded water instead of
continuous ponding.
Table 7. Effect of deficit irrigation on yield', water use efficiencyand amount of water saved
during rice cultivation under sadic ~ter conditions.
Treatments
Continuous submergence, 5± 2cm
Irrigation, 6.5 cm after 3 day of
disappearance of pond~ water
Irrigation, 6.5 cm after 6 days of
disappearance of ponded water
LSD at P=0.05
Grain yield,
Am unt of
t ha· 1
water g'iven, cm"
Water use
efficiency
Amount of
water saved, cm
2.97
3.73
da.l
100.6
22.31
37.08
32.5
3.17
86.8
36.52
46.3
0.29
'Average of two years.
"Quality olirrigation water used: EC1.7-1.9 dSm-l, RSC 7.5-8.6 meL-I, SAR 9.2-11.5.
"'Includes rainfall of 51.75 cm.
. Irrig'ation should be so planned as to
avoid water stress in rice during its reproductivegrowth phase. It is most crucial stage as
water stress during this period leads to higher
percent~ge of sterility and thus decreases the
number of filled spikelets. There is however,
no effect on 1000 grain weight. Adverse effects of water deficiency on growth of rice in
early stages is observed to decrease plant
height, number of tillers, total functional leaves,
leaf area and the accumulation of dry weight.
This decrease in agronomic attributes mayor
may. not affect the grain yield, if water is applied in good quantities for recovery of plants
before flowering.
Management of rainwater to recharge
groundwater
.
The storage of rainwater in rice fields
enhances its utilization in crop production,.
avoids moisture stress during. dry' spells and
minimizes irrigation water requirement and
induces groundwater recharge. The amount of
storage depends upon the quantum of rainfall
and its distribution, height of dikes around rice
fields, and the soil and varietal characteristics.
The dike height should be so planned that it
stores' maximum amount of rainwater in the
field. h has been observed that rainwater up to
15 cm storms can be safely stored in bunded
rice fields. Recharge of groundwater through
rainwater retained in the existing paddy fields.
so as to allow it to seep through the soil is a
natural, viable and practical solution.
. The excess wat~r after storage in the
rice fields should be stored in the dug-out ponds
located in the lower regions of the farm. This
water is to be recycled for irrigation during dry
spells. It can also be used to artificially recharge
the depleted aquifers through specially created
bore filters to arrest declining water table level
and to improve its quality in areas dominated
by groundwater irrigated rice. It has been observed that by adopting these strategies 80 to
90 per cent of the rainfall can be utilized within .
AGRICULTURAL REVIEWS
120
the farm area.
Change in date of transplanting:
Due to high temperature and low relative humidity before the onset of monsoon, there is a
maximum loss of applied water through evapotranspiration in the months of May and June.
. As a consequence of this, early transplanting
of rice Le. before first week of June leads to
higher losses of applied water. A study conducted in the Punjab (Anonymous, 1995)
showed that there is no decrease in yield of
rice when transplanting is completed up to June
(Table 8). Hence the farmers should not go in
for an early transplanting of rice so as to conserve groundwater.
Contrary to this, there is a practice in
the states of Punjab and Haryana to raise an
additional crop of rice, commonly known as
Sathi rice (c.v. Govinda is mostly used for this
purpose) during this period. Also known as May
planting of rice or summer rice, it is most unsustainable, as it demands pumping of large
quantities of underground water which may further worsen the water table in northern states.
This practice not only promotes wastage of
irrigation water but also the quality of rice raised
during this period of high temp~rature and high
humidity at the maturing time is poor. Such
rice has low storage quality and gets higher
percentage of brokens during' mming, and due
to these reasons it fetches low price in the
market. Practice of raising summer rice must
be curbed by either levying additional electricity charges for tube wells or stopping the supply of canal water during this period so as to
save water. During th+s period the farmers
should be advised to take a pulse crop like green
gram or cowpea at least. on non-alkali and reclaimed alkali soils. Such crops demand less
water during summer months and contribute
to soil fertility by addition of organic matter
and fixation of atmospheric nitrogen. Raising
of Sesbania as a green manure crop for the
main season rice crop is the best solution.
Table 8. Yield of rice as affected by the date of transplanting in Punjab, India.
Yield, t ha· 1
Transplanting period
Up to 15 th May
• 16 - 31 May
1 - 15 June
16 - 30 June
1 - 15 ,July
16 - 31 July
After 31 July
1991-92
1992-93
1993-94
Mean
3.40
3.35
3.43
3.29
3.00
2.43
196
3.50
3.56
3.56
3.43
2.85
2.65
2.59
3.70
3.72
3.76
3.51
3.03
2.55
2.22
3.53
3.54
3.58
3.41
2.96
2.54
2.26
Deterioration in groundwater quality·
distributed uniformly through out the soil
There is more percolation from low
profile,
land rice fields as compared to from the fields
• lowering of the water table exposing it to
supporting upland crops. Percolating water
the saline aqUifers, and
from surface layers increases the salt load of
• leaching of N0 3 and pesticides applied to
groundwater and deteriorates its quality. Other
rice fields.
reasons for deterioration of groundwater qualMehta and Singh (1989) observed that
ity under rice cultivation are:
after 15 years of reclamation, groundwaters in
• less recharge of groundwater as compared district of Kaithal, Haryana, India became more
to.,its depletion.
saline (Table 9). Over time, not only were their
• contamination with salts which were earlier salt roads as measured by EC but also their
VoL 23, No.2, 2002
121
sodicity hazards in term of residual sodium car- tion, deterioration in its quality may be the cause
bonate (RSC), sodium adsorption ratio (SAR) of resodification of the surface soil necessitatand soluble sodium percentage (SSP) increased ing repeat application of gypsum in these arsignificantly. Since this water is used for irriga,-'·eas.
Table 9. Changes in groundwater quality after reclamation in Kaithal area of Haryana, India.
Constituent
Before reclamation
Ca, meL!
MgmeLl
Na meL!
KmeL!
C01 meL!
HCO"meLl
ClmeLl
SO. meLl
EC, dSm· 1
RSCmeLl
SAR, (mmol-') ·112
SSP
After 15 years of reclamation
1.63
4.00
5.68
0.27
1.23
673
1.98
0.90
1.06
3.65
2.85
48.25
1.15
3.45
4.18
0.10
2.90
4.45
1.25
1.08
0.69
1.95
2.75
45.80
Table 10. Groundwater quality as affected by depth in village Golewala, Faridkot district of Punjab, India.
Water table depth, m
EC, dSm 1
3.0 - 10.5
10.5 - 12;0
12.0 - 15.0
>15.0
0.43 - 0.45
0.45·0.60
0.60 - 1.77
1.77 - 2.32
RSC, meL'l
Quality rating
-0.1 -0.8
0.8'· 3.8
3.8 -12.1
12.. 1-16.3
Fit for irrigation
Marginal
Unlit
Unfit
In arid areas there is generally dete- increased, mainly due to the contributions of
rioration in groundwater quality with depth. But excessive salts from the soil profile. These inin such areas when canal irrigation is intro-vestigations point·· out that there is a serious
duced, the quality of water at shallow depth~. risk of groundw,atet quality deteriorating on inimproves due to continuous seepage from
troductionqf.canal irrigation in riye growing
distribution system. Hira and Murty (1985k~ areas, the degree being more in zones already
a case study conducted in Golewala villag~'ln having brackish water. Further, as a CQnseFaridkot district of Punjab found that a thin quent~ of easy availability of canal water, the
layer of fresh water floats over the saline water f.P.r..mers do not use underground brackish wain most of the canal command areas (Table tel"' resulting in rise in water table and ultimately
10) and is used for irrigation. But as the water formation of waterlogged saline soils.
table declines, due to over exploitation, thlt Decrease in soil fertility
groundwater quality deteriorates increasing the
Salt-affected soils are poor in a.M. and
risk of salinization of soil.
available N. In the initial years due to high pH,
Wheni! groundwaters are already sa- ESP and high a,mounts of CaC0 3 , about 32 to
line like that in R"ohtak, Bhiwani, Hisar, Sonepat 50 lXl of the applied N-fertilizer is lost through
and Jind districts of Haryana, India, seepage volatilization (Bhardwaj and Abrol, 1978) refrom the canal irrigation system have not shown suiting in lower efficiency Of applied chemical
any improvement in their quality. On the con- fertilizer. Along with this due to low symbiotic
trary, inmost cases the groundwater salinity fixation of atmospheric N and low activity of
toe·
i
122
AGRICULTURAL REVIEWS
soil microorganisms, the contribution of N for
plant need from these sources is very low. As
a result of this N needs of alkali soils for crop
production are relatively higher as compared
to that of normal soils. Since these soils contain less amount of O.M. and it is not possible
to build inorganic-N reserves in the soils; it is
necessary to apply appropriate amount of Nfertilizers (120 - 150 kg N ha- 1) to sustain rice
production even after reclamation of theSe soils.
Though all alkali soils under natural
conditions are calcareous and contain appreciable quantity of CaC0 yet due to its low
3
solubility at high pH, the crop suffers from its
deficiency. Lack of Ca also results in disturbed
Ca, Na and K ratio causing excess of Na and
affecting yield. In the-initial years of reclamation, application of amendments like gypsum
help in lowering pH, ESP and meeting the Ca
needs of plants. During next phase, Ca needs
of the plants are met through solublization of
native CaC03 through the action of roots, Ca
contained in the irrigation water and that supplied through the chemical fertilizers like single
super phosphate and calcium ammonium nitrate (Chhabra and Kamra, 2000). Due to these
reasons rice plants grown in reclaimed alkali
soils seldom suffer from Ca deficiency:
Alkali soils though deficient in a.M.
and available N, are rich in extractable phosphorus. This is mainly due t~he fact that
Na CO and NaHCO present in these soils
rea~t with native apatite to form soluble sodium phosphate. Trivalent phosphate ions of
this are converted into H PO ions when these
come in contact with the piant roots in the
rhizosphere and thus meet the P needs of the
crop. Due to high amounts of extractable P in
these soils, rice and wheat grown in the first
few years do not respond to application of
phosphatic fertilizers (Chhabra, 1985). Butwith
time, the soluble P decreases (Fig. 8) due to
leaching from the surface to the lower layers,
conversion of Na 3 PO 4 into less soluble
Ca(HpO 4)2' higher fixation of soluble P by soil
due to decrease in pH and depletion as a result
of plant uptake. Hence on reclamation avail'able P of the surface soil decreases below the
critical level which results in low yields espe.'cially of rice crop which depends on the fertility of the surface soil. However, with time even
the yields of w~ crop start declining in P
control plots-}ig. 9}. From a long term field
study, Orflabra and t~ur (2000) suggested
to aW1y 22 kg P ha- 1 aftet three to five years
of fe~lama~o~ to b~th rice. an~ wheat crops to
sustaIn their YIelds In alkah s01ls.
Alkali soils also contain high amounts
of extractable potassium and do not respond
to application of potassic fertilizers. But with
time there is high removal of exchangeable K
as well as the one released due to solubility of
cl(\,Y minerals (Pal and Mondal, 1980). ~s a
re!Llt of this though the rice crop does not suffer due to K deficiency in the initial years, its
level may become critical if farmers do not practice balanced use of fertilizers. Rice crop raised
in high ESP soil, shows high Na-K ratio that
may prompt application of potassic fertilizers.
But the remedy lies in correcting Ca-Na-K balance by judicious application of amendments
(Chhabra and Abrol, 1983) rather than applyin~ potassic fertiliz~rs to a.lready K.rich alkali
~011~: Among the mlcro~utnents, ~n IS th~ m~st
hm~tI~g fo~/growth of nce c.ro p In alkah s01ls.
ThiS IS maInly as a result of ItS decreased solubility due tq hig~ ~~, CaC03 , and soluble. phosph~tes: In the Initial stages o~ re~lamatlon alkah s01ls n~ a r~gular fipphcatlon of 10 to
1
20 kg zinc stJ.lphate ha- whe~ opti~um d~se
of gypsum a~ an .amendment IS apphed. ~Ith
passage of tIme, the ~eed for supple~en~Ing
Zn can be reduced With out any loss In YIeld
(Chhabra et al., 1982).
Post reclamation management of nutrients in alkali soils is very crucial to maintain
their fertility for sustaining rice production.
Along with application of chemic~1 fertilizers,
O,"-..I-....1.-..L-..J--J--J--.L.....J.--I_L-1.--l
RW~WRWRW~WRW
I
'Fig. 8.
o
CIl
%
2!
4
5
e
Cropping year
Changes in Olsen's extractable P as affected by reclamation and application of P and K
in an alkali soil fol1owing rice (R) - wheat (W) cropping sequence.
X
10
e"E 20
0
u·
0..
.5
~
30
X X
~40
"".
. .
:p
u
.
.
•
;:l
.
Cll
..
Rice
• •
c§!.
2
Fig.
4
I
6
8
10
12
14
16
IS" 20
Nos. of cropping years
9. Relative response of rice and wheat crops to P application as per cent reduction in yield in P control
plots over those receiving 22 kg P ha· l in a gypsum amended alkali soil over a period of 20 years.
124
AGRICULTURAL REVIEWS
proper maintenance of O.M. through the use
of green manuring, FYM, compost, poultry
manuure and recycling of~rop residues in these
soils is crucial for obtaining higher efficiency
of inorganic fertilizers, to maintain good physical properties and to improve their biological
health.
Saline soils
Saline soils have excess soluble sqJ{s,
mostly ECe >4 dSm l , pHs <8.2 and ESP <15.
In areas affected by primary salinity Le. where
salt accumulation is due to lack of leaching of
weathering products, rice is not grown. But in
areas suffering due to secondary salinisation
i. e. salinity developed due to rise in water table
as a result of introduction of canal irrigation,
rice is being grown as a major crop. This is
mainly due to compulsion of using these waterlogged soils, as no other crop will grow under such situations. As per the estimates of
Ministry of Water Resources (Anonymous,
1991) an area of 2.46 million ha has become
waterlogged in various major irrigation commands in India alone. Such areas are increasing at an alarming rate due to non-judicious
use of canal irrigation in otherwise dry land
areas.
izer on soil test basis to obtain and sustain optimum yields.
Since these soils have shallow water
table which fluctuates between surface undulation at the time of rice transplanting to 2 meters
belowft\e surface at the time of maturing, vari~s adaptable to such fluctuating water table
should be evOlved. These varieties should also
be more tolerant to toxic concentration of elements like F, Se, Mo and B present in these
soils and high levels of salinity at the time of
maturity.
Deterioration in soil properties due to use
of brackish groundwater
large parts of Haryana, Punjab and
Uttar Pradesh in India and in many other countries have a problem of brackish underground
waters. These waters have low salt concentration (EC 1. 7 to 1. 9 dSm l) but high RSC (7.5
to 8.6 mel'l) and high SAR [9.2 to 11.50
(mmoleL-I)'1/2). Some times these waters also
contain high amounts of toxic elements like F,
B, Si, Se an.d Mo. These elements are less toxic
to rice plant but may be-harmful to the animals
that feed on straw of crops raised with such
waters (Singh et aI, 1979). Soil crust formed
due to use of RSC waters leads to low germiRice crop raised under saline environ- nation and poor stand of upland crops. low
ment suffers due to the following problems:
infiltration rate causes stagnation of rainwater
during monsoon and leads to failure of many
• Osmotic stress due to high soluble salts.
• Toxic effects due to high concentration 6f arable crops. Due to these reasons the farmers are resorting to cultivation of rice as a ma. CI and S04'
jor crop in these areas.
• Fluctuating water table.
• Water stress near maturity leading to
Most of RSC waters found in Punjab
sterility.
have low EC and low Ca content «2 meL-I).
In areas, where with the provision of Such waters are more harmful as these cause
drainage facilities, water table can be lowered soil deterioration much faster, lead to rise in
and salinit'I,: managed, rice crop should never SAR quickly and pose problems of soil permebe grown. Where groundwater is saline and ability (especially during rainy season) due to
shallow and there is no drainage, rice with salt low electrolyte concentration. While most of
tolerant varieties is the only choice. This has the RSC waters found in Haryana have relato be managed as mono-cropped area. These tively high EC and soluble Ca (>2 meL-I). Such
soils have low to medium.fertility status and waters are less harmful as their high Ca conneed a regular application of balanced fertil- tent together with high amount of CaC03 found
Vol. 23, No.2, 2002
in these soils and the monsoon type of climatic conditions of the area causes less deterioration in soil.
Use of such waters leads to rise in pH,
ESP, deterioration of physical and chemical
properties of soils, After a continuous and prolonged use of such waters, the upper soil layers also show increase in EC affecting the yield
of crops following rice, These soils are then
labelled as saline-alkali soils,
To sustain rice yields and to prevent
the failure of other crops following rice, it is
recommended to treat irrigation water to neutralize its RSC so as to bring it within the' safe
:tin ±.of2 5 meL!, Soils, which due to the use
of high RSC waters have developed high pH
and ESP should be treated as alkali soils and
reclaimed through the use of gypsum as discussed earlier. "
CONCLUSIONS
From the foregoing discussions,it is
evident that to sustain rice production in degraded soils like alkali and saline soils, to maintain their productivity and groundwater balance,
the following points should be considered:
• Ban cultivation of summer rice to avoid
the period of maximum evaporation and
to conserve groundwater for the main season crop, Raising a pulse crop like, green
gram or cowpea at least on reclaimed al~
kali and non-alkali soils during this period
will lower the water demand and improve
125
soil fertility, Sesbania should be raised as
agreen manure crop for the main season
rice crop dUring this period.
• Encourage farmers to transplant paddy
late, i.e. by the end of June, to avoid the
period of maximum evapotranspiration
and hence reduce the demand on groundwater,
• Shift from conventional ponding/submergence to irrigation for maintaining soil
saturation so as to save water in declining
water table areas.
• Decrease the area under rice and produce
more from the existing area, Diversify the
cropping pattern to horticulture,
olericulture and floriculture on those reclaimed alkali soils that have a good water
supply.
• Recharge groundwater through rainwater
to maintain water balance and to prevent
degradation of its quality,
• Gypsum treated RSC water should be used
for"irrigation to minimise their deleterious
effects on soil physical and chemical properties,
• Maintain optimum soil fertility through
balanced and integrated nutrient management.
• Develop varieties suitable for saline soils
with fluctuating water levels, tolerant to
toxic levels of Fe, S and high levels of salinity at maturity.
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