adapting to climate change by improving water productivity of soils in dry areas

ADAPTING TO CLIMATE CHANGE BY IMPROVING WATERPRODUCTIVITY OF SOILS IN DRY AREAS

M. QADIR1,2*, A. D. NOBLE3 AND C. CHARTRES2

1International Center for Agricultural Research in the Dry Areas (ICARDA), PO Box 5466, Aleppo, Syria2International Water Management Institute (IWMI), PO Box 2075, Colombo, Sri Lanka

3IWMI, South East Asia Office, National Agriculture and Forestry Research Institute, Ban Nongviengkham, Xaythany District, PO Box 4199, Vientiane,Lao People’s Democratic Republic

Received 11 April 2010; Revised 14 December 2010; Accepted 15 December 2010

ABSTRACT

Considering extreme events of climate change and declining availability of appropriate quality water and/or highly productive soil resourcesfor agriculture in dryland regions, the need to produce more food, forage and fibre will necessitate the effective utilization of marginal-qualitywater and soil resources. Recent research and practices have demonstrated that effective utilization of these natural resources in dry areas canimprove agricultural productivity per unit area and per unit water applied. This paper focuses on the following three case studies as examples:(1) low productivity soils affected by high levels of magnesium in soil solution and on the cation exchange complex; (2) degraded sandy soilsunder rainfed conditions characterized by low water-holding capacity, organic matter and clay content and (3) abandoned irrigated soils withelevated levels of salts inhibiting growth of income generating crops. The results of these studies demonstrate that application of calcium-supplying phosphogypsum to high-magnesium soils, addition of clays to light textured degraded soils and phytoremediation of abandonedsalt-affected soils significantly improved productivity of these soils. Furthermore, under most circumstances, these interventions wereeconomically viable, revealing that the efficient use of marginal-quality water and soil resources has the potential to improve livelihoods amidgrowing populations in dry areas while reversing the natural resource degradation trend. However, considerably more investment and policy-level interventions are needed to tackle soil degradation/remediation issues across both irrigated and dryland agricultural environments if themajor challenge of producing enough food, forage and fibre is to be met. Copyright # 2011 John Wiley & Sons, Ltd.

key words: salt-affected soils; magnesium-affected soils; sandy soils; soil management; phytoremediation; water productivity; soil productivity; climate

change adaptation

INTRODUCTION

Current demographic trends and future population growth

projections in dry areas necessitate a balance between the

functions (provision of goods and services) supplied by

natural resources and demands by societies exploiting these

resources particularly in the context of predicted changes

associated with climate change. This will necessitate

sustained increases in the provision of goods and services

that include food, forage, fuel and fibre (Safriel and Adeel,

2005) from existing production systems as lateral expansion

of the agricultural sector is no longer tenable without

significant losses in biodiversity and ecosystem function.

Recent assessments reveal that the functionality of these

natural resources (i.e. land and water) in providing these

goods and services has significantly declined (Bossio et al.,

2007; Qadir et al., 2007a). Freshwater scarcity, land

degradation and water quality deterioration have become

global concerns, which are expected to intensify in resource-

poor countries in dry areas due to anthropogenic interven-

tions and increasing possibility of extreme events of climate

change (Intergovernmental Panel on Climate Change, IPCC,

2007).

The resilience of an ecosystem to buffer change, including

resistance to shock, is a fundamental intrinsic property and

provides a measure of vulnerability to degradation (Stocking

and Murnaghan, 2001). The concept suggests that a system,

such as an agro-ecosystem, responds more or less gradually

to changes in its management or environment (e.g. climate)

but only up to a certain threshold. Once this threshold is

surpassed, adjustments cannot take place rapidly enough and

the system collapses. Realization of the existence of a

‘resilience threshold’ for natural resources has important

consequences for their management (Sayer and Campbell,

2002). For example, resilient soils (e.g. Vertisols) may be

degraded to a significant degree and still be restored to some

equilibrium state (e.g. in traditional slash-and-burn systems)

without a dramatic or irreversible decline in productivity.

Other soil types (e.g. Arenosols) are much less resilient.

land degradation & development

Land Degrad. Develop. (2011)

Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ldr.1091

*Correspondence to: M. Qadir, International Center for AgriculturalResearch in the Dry Areas (ICARDA), PO Box 5466, Aleppo, Syria.E-mail: [email protected]

Copyright # 2011 John Wiley & Sons, Ltd.

Once a threshold is reached, these systems collapse and

cannot easily be brought back to their former state. This has

been referred to as retrogressive succession as species

diversity and functionality changes due to pedogenesis and

landscape age (Jenny, 1941; Walker et al., 2000). Soils that

degrade beyond some threshold level are often damaged

beyond repair at time scales of human relevance and may

never recover. The cumulative loss of productivity from soil

degradation of virgin land in all agro-climatic zones is

estimated at 5 per cent (Crosson, 1995). However, this

estimate hides large differences between zones and the

particular vulnerabilities of soils in the tropics (Scherr and

Yadav, 1995; Stocking, 2003). It is pertinent to bear in mind

that crossing this threshold would result in declining

productivity of water resources, whether rainfed or irrigated.

Considering extreme events of climate change and

declining availability of appropriate quality water and/or

highly productive soil resources for agriculture in dryland

regions, the need to producemore food, forage, fuel and fibre

will necessitate the effective utilization of marginal-quality

soil and water resources (Bouwer, 2002; Wichelns and

Oster, 2006; Qadir et al., 2007b). Although such natural

resources are often viewed as representing major environ-

mental and agricultural challenges in terms of providing

goods and services, these resources are valuable and cannot

be neglected, especially in areas where significant invest-

ments have already been made in infrastructure in general

and irrigation systems development in particular. The

efficient use of marginal-quality water and soil resources

has the potential to improve livelihoods amid growing

populations in dry areas while reversing the natural resource

degradation trend.

With certain agricultural productivity constraint(s),

marginal soils mainly consist of a variety of salt-affected

soils (excess soluble salts and/or specific ions such as

sodium, magnesium and/or boron), low-fertility soils (low

nutrient-availability status with depleted availability of

essential plant nutrients), sandy soils (low water-holding

capacity, organic matter and clay content), wind- and water-

eroded soils (loss of topsoil and terrain deformation),

compacted soils (degradation of physical properties with

restricted movement of water and air) and waterlogged soils

(high groundwater level and low availability of soil air)

(Bossio et al., 2007). Similarly, there are two major types of

marginal-quality water resources—wastewater generated

from domestic and industrial sectors in urban and peri-urban

areas, and saline water generated from agricultural drainage

water or pumped from saline groundwater (Qadir et al.,

2007a).

Recent research and practices have demonstrated that

effective utilization of marginal-quality soil andwater resources

in dry areas can improve the agricultural productivity and

livelihood resilience of the farming communities (Noble

et al., 2004; Pretty et al., 2006; Qadir et al., 2007c;

Vyshpolsky et al., 2008). We review selected examples of

the interventions that have been shown to enhance the

productivity of degraded dryland soils that are expected to

contribute to the suite of adaptation strategies to ensure

continued sustainable food production.

PRODUCTIVITY ENHANCEMENT OF MARGINAL

SOILS IN DRY AREAS

There are several examples demonstrating productivity

enhancement of marginal soils in dry areas through different

management approaches (Noble et al., 2004; Pretty et al.,

2006; Bossio et al., 2007; Qadir et al., 2007c; Vyshpolsky

et al., 2010). We consider a range of such soils, from

abandoned areas due to extremely low or no productivity to

those areas with low productivity of common agricultural

crops. The focus is on the following three case studies as

examples:

� low productivity soils affected by high levels of magnes-

ium in soil solution and on the cation exchange complex;

� low productivity sandysoils affected by lowwater-holding

capacity, organic matter and clay content;

� abandoned salt-affected soils with elevated levels of salts

inhibiting growth of income generating crops.

In each case, we address the key elements of the nature of

the soil degradation and geographical distribution followed

by the description of potential interventions that have

resulted in agricultural productivity enhancement and

livelihood resilience.

Enhancing the Productivity of Magnesium-Affected Soils

under Irrigated Conditions

Excess levels of magnesium (Mg2þ) in irrigation waters and/or in soils in combination with sodium (Naþ) or alone resultin soil degradation through impacts on soil physical

properties (Oster and Jayawardane, 1998; Qadir and

Schubert, 2002). The major reason for the specific Mg2þ

effect is that the hydration energy and hydration radius of

Mg2þ are greater than calcium (Ca2þ) (Bohn et al., 1985).

Thus, the soil surface tends to absorb more water than where

exchangeable Ca2þ is present, resulting in weakening of the

forces that keep soil particles together. This, in turn,

decreases the amount of energy to break down soil aggregates

(Oster and Jayawardane, 1998). At low levels of exchangeable

Naþ, Mg2þ also enhances the effects of Naþ on clay

dispersion and hydraulic conductivity (Qadir and Schubert,

2002). In addition, high Mg2þ levels in soils tend to increase

surface sealing and erosion (Dontsova and Norton, 2002).

There are emerging examples from irrigation schemes

worldwide where excess levels of Mg2þ on the cation

exchange complex result in soil degradation through a

Copyright # 2011 John Wiley & Sons, Ltd. LAND DEGRADATION & DEVELOPMENT (2011)

M. QADIR ET AL.

decline in soil physical properties (Garcia-Ocampo, 2003;

Qadir and De Pauw, 2007). For example in Kazakhstan part

of the Aral Sea Basin, Western Asia, more than 140,000 ha

fall under such type of degraded soils and irrigation water

contains higher levels of Mg2þ than Ca2þ, suggesting

Mg2þ:Ca2þ ratios greater than 1 (Vyshpolsky et al., 2008;

Karimov et al., 2009). More than 30 per cent of the irrigated

area in southern Kazakhstan is dominated by these soils that

have exchangeable magnesium percentage (EMP) in the

range of 25–45 per cent, and exchangeable sodium

percentage (ESP) remains below 2 per cent (Vyshpolsky

et al., 2010). Another example of magnesium-affected soils

is from South America where 117,000 ha are affected by

high levels of Mg2þ in the Cauca River Valley in Colombia.

The EMP levels range from 25 to 30 per cent, whereas ESP

remains as low as 4 per cent (Garcia-Ocampo, 2003). Table I

shows EMP and ESP levels in some soil samples collected

from Cauca River Valley and Aral Sea Basin.

Soil data from some parts of Australia reveal considerably

high levels of Mg2þ, although soils are not formally

classified as magnesium-affected soils. A comparison of

exchangeable cation data for a sodic soil at Condobolin,

New South Wales reveals ratio between exchangeable Ca2þ

and Mg2þ around 1 and EMP values around 40 per cent

(Abbott, 1987; Mckenzie et al., 1993). It is anticipated that

in addition to Naþ, the effects of Mg2þ would have

compounded the situation and caused greater deterioration

of such soils. Rengasamy et al. (1986) suggested that the

ratio between exchangeable Ca2þ andMg2þ should be above

1 to minimize dispersion problems in Red-Brown Earths of

Southeastern Australia.

With low infiltration rates and hydraulic conductivities,

magnesium-affected soils form massive clods upon drying

after irrigation events which impact water flow rates along

furrows and infiltration. The consequence of using high-

Mg2þ soils and waters in agricultural production systems

without suitable management practices has been a gradual

decline in crop yield.

The productivity of magnesium-affected soils can be

enhanced by increasing Ca2þ on the cation exchange sites to

mitigate the effects of excessive exchangeable Mg2þ. This isaccomplished by applying sufficient amounts of Ca2þ to the

soil (Ghafoor et al., 1992; Karajeh et al., 2004). Gypsum

(CaSO4�2H2O) is the most commonly available and low-cost

amendment that can be used as a source of Ca2þ. It is usuallyused to ameliorate sodic and saline–sodic soils, which are

characterized by excess levels of Naþ (Oster, 1982;

Shainberg et al., 1989; Chartres, 1993). Phosphogypsum

is another low-cost source of Ca2þ that can be used as a soil

amendment. As a major waste product of phosphorous

fertilizer factories, phosphogypsum supplies appreciable

quantities of phosphorous to the soil in addition to increasing

the Ca2þ levels (Alcordo and Rechcigl, 1993).

The results of a 4-year study conducted in Kazakhstan

demonstrated beneficial effects of applying phosphogypsum

to magnesium-affected soils on soil quality and cotton yield

(Vyshpolsky et al., 2008). The irrigation water was of

marginal-quality with Mg2þ to Ca2þ ratio ranging from 1.30

to 1.66 during irrigation period (Table II). The study site had

a smooth landscape with slopes from 0.002 to 0.0035. With

high summer temperatures (30–408C during June, July and

August), annual precipitation ranged from 50 to 250mm,

with 90 per cent occurring during October through May. The

soil was a heavy loamwith about 1 per cent organic matter in

the surface layer and a cation exchange capacity (CEC) of

11�� 1cmolckg�1. Soil bulk density was 1.46� 0.01Mgm�3

and pH varied narrowly from 8.1 to 8.2. There were three

treatments: (1) control without application of phosphogyp-

sum; (2) soil application of phosphogypsum at the rate of

4.5 t ha�1 and (3) soil application of phosphogypsum at the

rate of 8.0 t ha�1.

The application of phosphogypsum (4.5 and 8.0 t ha�1)

increased Ca2þ concentration in the soil and triggered the

replacement of excess Mg2þ from the cation exchange sites.

After harvesting the first crop, there was an 18 per cent

decrease in EMP of the surface 0.2 m soil over the pre-

experiment level in the plots where phosphogypsum was

applied at 4.5 t ha�1, and a 25 per cent decrease in EMP in

plots treated with phosphogypsum at 8 t ha�1 (Figure 1). The

additional beneficial effect of the amendment application

resulted in an increase in the soil phosphorus content.

The highest cotton yields were obtained during the first

year of the treatment application, which were 2.7 and

3.0 t ha�1, respectively, from the treatments where phos-

phogypsum was applied at 4.5 and 8 t ha�1 (Figure 2).

Cotton yield in the control plots (1.4 t ha�1) was almost half

the yield harvested from phosphogypsum treatments. There

was a 93 per cent increase in cotton yield from the

phosphogypsum treatment (4.5 t ha�1) over the control. In

the case of the 8.0 t ha�1 treatment, cotton yield increased to

114 per cent over that harvested from control plots. The yield

Table I. Characteristics of some soils in terms of exchangeablesodium percentage (ESP) and exchangeable magnesium percen-tage (EMP) levels

Soil location ESP EMP

New South Wales, Australia 12�1 41�9Cauca River Valley, Colombia 4�2 26�7Cauca River Valley, Colombia 0�7 24�8Cauca River Valley, Colombia 2�2 28�5Aral Sea Basin, Kazakhstan 1�9 28�0Aral Sea Basin, Kazakhstan 1�3 41�6Aral Sea Basin, Kazakhstan 1�6 37�8Based on the data from Australia (Abbott, 1987), Colombia (Garcia-Ocampo, 2003) and Kazakhstan (Vyshpolsky et al., 2008).


ADAPTING TO CLIMATE CHANGE THROUGH SOIL MANAGEMENT

pattern from the control plots for the subsequent years

showed a similar response trend (1.3–1.4 t ha�1). In the case

of phosphogypsum treatments, cotton yields gradually

declined in the subsequent years because of an increase

in EMP in the soil as the amendment was applied only at the

beginning of the experiment and it was fully utilized in

subsequent years. In the phosphogypsum treatment with

4.5 t ha�1, cotton yields decreased from 2.7 t ha�1 in first

year to 2.2 t ha�1 in fourth year. The yield decrease pattern

for the 8 t ha�1 phosphogypsum treatment was from 3.0 to

2.2 t ha�1 in 4 years. The 4-year average cotton yield in the

8 t ha�1 phosphogypsum application treatment was the

highest (2.6 t ha�1); the yield was 2.4 t ha�1 in the 4.5 t ha�1

phosphogypsum treatment, and 1.4 tha�1 in the control treatment.

The enhancement in cotton yield in phosphogypsum

treatments was due to the increased levels of Ca2þ in soil

solution and on cation exchange sites, thereby improving the

ionic balance and physical properties of the soil. The increase

in phosphorus levels from phosphogypsum application also

helped improve the phosphorous nutrition of the plants. Since

phosphogypsumwas applied once at the beginning, exchange-

able Mg2þ levels tended to increase after 4 years of

application, particularly in the treatment with 4.5 t ha�1

phosphogypsum. This necessitated the need for a booster dose

of phosphogypsum to such soils after every 4–5 years to

optimize the ionic balance and sustain higher levels of cotton

production. The economic benefits from the phosphogypsum

treatments were almost twice than those from the control.

Table II. Composition of irrigation water and agricultural drainage water during the cotton growing season (June, July and August) at theexperimental site in Kazakhstan (Adapted from Vyshpolsky et al., 2008)

Parameter Unit Canal watera Drainage waterb

June July August June July August

EC dSm�1 0�69 0�72 0�78 1�67 2�19 2�32pH — 7�95 8�00 7�90 8�00 8�10 8�30TSS mmolc L

�1 6�90 7�20 7�80 16�70 21�90 23�20Ca2þ mmolc L

�1 2�00 1�97 2�08 5�70 6�92 7�62Mg2þ mmolc L

�1 2�60 2�62 3�41 5�44 6�87 7�45Naþ mmolc L

�1 1�17 1�32 1�53 4�25 6�25 6�25Kþ mmolc L

�1 0�03 0�01 0�03 0�03 0�03 0�03HCO�

3 mmolc L�1 3�36 3�37 3�39 6�00 7�50 7�85

Cl– mmolc L�1 0�32 0�35 0�39 2�15 2�60 2�43

SO2�4

mmolc L�1 2�68 2�89 3�28 7�26 10�10 11�10

Mg2þ:Ca2þ — 1�30 1�33 1�66 0�95 0�99 0�98SAR — 0�77 0�87 0�92 1�80 2�38 2�28aWater sampled from Arys Turkestan canal used to irrigate cotton in southern Kazakhstan.bDrainage water generated in the area irrigated by Arys Turkestan Canal.

Figure 1. Exchangeable magnesium percentage (EMP) levels in a mag-nesium-affected soil as influenced by the application of phosphogypsum atthe rate of 4.5 and 8.0 t ha�1 (Based on the data from Vyshpolsky et al.,

2008)

Figure 2. Cotton yield as affected by different rates of phosphogypsumapplication (0, 4.5 and 8.0 t ha�1) to a magnesium-affected soil in Kazakh-stan. The error bars indicate standard error of means of three replications

(Adapted from Vyshpolsky et al., 2008)


M. QADIR ET AL.

Another study on a similar type of soil was conducted in

2006–2007 to find out the appropriate combinations of the

rates and timings of phosphogypsum application to mitigate

the effects of high levels of Mg2þ in magnesium-affected

soils. There were five treatments: (1) control without

application of phosphogypsum; (2) soil application of

phosphogypsum before snowfall at the rate of 3.3 t ha�1; (3)

soil application of phosphogypsum before snowfall at the

rate of 8.0 t ha�1; (4) soil application of phosphogypsum

after snowfall at the rate of 3.3 t ha�1 and (5) soil application

of phosphogypsum after snowfall at the rate of 8.0 t ha�1.

The results of this field study demonstrated the beneficial

effects of phosphogypsum application to a magnesium-

affected soil. The phosphogypsum treatments performed

better than the typical farming practice in terms of (1)

improved soil quality through a reduction in EMP levels, (2)

enhanced water movement into and through the soil vis-a-vis

increased moisture storage in the soil for use by the plant

roots, (3) increased cotton yield and water productivity and

(4) greater financial benefits (Vyshpolsky et al., 2010). In

addition, surface runoff was significantly reduced in the

phosphogypsum treatments, which improved the irrigation

efficiency and effectively provided more moisture to the root

zone through improved infiltration. This in turn increased

crop water productivity in the phosphogypsum treatments.

The 2-year average water productivity in control treatment

was 0.32 kgm�3, whereas it ranged from 0.44 to 0.52 kgm�3

in the phosphogypsum treatments. Figure 3 shows water

productivity of cotton as affected by different times (before

snowfall in January or after snowfall in April) and rates of

phosphogypsum application to a magnesium-affected soil.

In terms of crop growth and yield, cotton yields in the

phosphogypsum treatments were 19–46 per cent higher than

control.

Based on the overall effects, the amendment application

before the snowfall improved soil properties to a greater

extent compared to the application in spring after the

snowmelt. The economic benefits in terms of marginal rate

of return from phosphogypsum application at 3.3 t ha�1 were

double those of treatments receiving the amendment at

8.0 t ha�1, thereby suggesting that the lower rate was

optimal. This rate of phosphogypsum application was based

on the phosphogypsum requirement of the soil for 0.3m depth.

Enhancing the Productivity of Degraded Light Textured

Soils under Rainfed Conditions

Light textured sandy soils are ubiquitous globally and can be

found from the wet tropics to the arid and semi-arid regions

of the world. The World Reference Base (WRB) charac-

terizes sandy soils as having a clay content of < 18 per cent

with a sand content of> 65 per cent in the first 100 cm of the

solum (IUSS Working Group WRB, 2006) and are often

found in the following soil groups: Arenosols, Regosols,

Leptosols and Fluvisols. Arenosols are the dominant soil

group with a global areal extent of 900 million ha that are

often found in the dry zone. However, several million

hectares of these soils are found in the wet and semi-arid

tropics. For example in the semi-arid tropics of Northeast

Thailand, it is estimated that the region is dominated by 6.6

million ha of these soils and due to their low water- and

nutrient-holding capacity are a significant constraint to

agronomic productivity (Limpinuntara, 2001). These soils

form the focus of the following section where the impact of

land use change on soil chemical properties is highlighted

and a novel strategy that builds on indigenous knowledge

and addresses fundamental intrinsic soil properties soils are

discussed in the process of re-establishing the productivity

of degraded soils.

Over the past 40 years, massive re-engineering of the

landscape has occurred in Northeast Thailand with the

clearing of climax Dipterocarp forest for timber products

and agriculture. In their natural state, these Dipterocarp

forests maintain productive and diverse ecosystems that are

dependent on efficient resource utilization. A characteristic

of these systems is their reliance on soil organic matter

(SOM) to cycle nutrients from the soil through the plant and

back to the soil through plant debris; and to increase the

water-holding capacity of the soil. When these soils are

cleared for intensive agricultural production, there is a rapid

decline in fertility (Table III) and water-holding capacity and

a consequent decline in productive potential. It is clearly

evident that conversion of primary forest to rice and cassava

based systems there is a rapid decline in soil organic carbon,

basic cations and the CEC (Table III).

Figure 3. Two-year average water productivity as affected by differenttimes (before snowfall in January or after snowfall in April) and rates ofphosphogypsum application to a magnesium-affected soil. The error barsindicate standard error of means of three replications (Adapted from

Vyshpolsky et al., 2010)



In order to maintain the productive output of these soils,

farmers have traditionally applied cattle manure and

composts derived from household waste and leaf litter to

both upland and lowland fields along with sparing amounts

of inorganic fertilizer. The effects of these organic

amendments may not be long lasting due to rapid

mineralization and therefore require regular routine addi-

tions. For more intensive high input systems on these light

textured soils, farmers have resorted to rehabilitating soils

through the addition of locally available termite mound

material. This clearly demonstrates the ability of traditional

farmer knowledge in perceiving and implementing strat-

egies to address the issue of declining fertility associated

with their production practices. These materials are

commercially excavated from large mounds that are the

products of termite activities (Macrotermes spp.). Farmers

will apply up to 7,200 t ha�1 to small plots where intensive

vegetable production is undertaken (Noble et al., 2004).

The climate of Northeast Thailand is classified according

to Koppen as tropical savanna (Oliver and Wilson, 1987).

Annual rainfall ranges from 900 to 1,300mm, while

averaging 1,183mm (Noble et al., 2000; Gobius et al.,

2001). The region’s mean maximum temperature and annual

pan evaporation are 32.58C and 1862mm, respectively

(Noble et al., 2000). A study undertaken in Northeast

Thailand to assess the efficacy of a range of soil amendment

techniques in rejuvenating degraded light textured sandy

soils under rainfed conditions has shown that the incorp-

oration of locally source bentonite clay significantly

increases the yields of forage sorghum over consecutive

years. The following treatments replicated four times were

applied: (1) Control (current farmer practice); (2) Dred.¼ -

dredged material at 240 t ha�1; (3) Comp.¼ leaf litter

compost at 10 t ha�1; (4) Term.¼ termite mound soil at

120 t ha�1; (5) Bent.¼ local bentonite at 50 t ha�1 and (6)

Bent.þComp.¼ local bentonite at 50 t ha�1 with leaf litter

compost of 10 t ha�1.

Cumulative dry matter (DM) production over 2 years

ranged from 0.22 tDMha�1 in the control treatments where

plant production completely failed in the second year of

cropping to 10.8 and 22.4 t DMha�1 for the locally sourced

termite mound material (120 t ha�1) and local bentonite

(50 t ha�1)þ leaf litter compost (10 t ha�1), respectively

(Figure 4). Analysis of the CEC 8 months after application

of treatments clearly demonstrates significant increases in

the surface 0–20 cm depth intervals that would significantly

increase the nutrient supply/holding capacity of the soil

(Figure 5). Further, measurements of the water retention

characteristics of soils treated with bentonite indicated a 12 per

cent increase in water-holding capacity (Suzuki et al., 2007).

These results clearly demonstrate the intrinsic importance

of CEC and the available water content of soils on the growth

of crops in rainfed production systems. By addressing these

constraints, greater utilization of the resources available to

farmers could be achieved. For example, a simple measure

of water productivity associated with the application of a

range contrasting soil treatments in Northeast Thailand

clearly demonstrates the positive benefits associated with

soil improvements on water use efficiencies under rainfed

Table III. Selected soil chemical properties of the surface 0–10 cm depth interval from paired sites in Northeast Thailand indicatingdifference in attributes associated with conversion to agricultural production (Adapted from Noble et al., 2003 )

Attribute Undisturbed Disturbed Undisturbed DisturbedLand use Dipterocarp forest Rice Dipterocarp forest Cassava

Organic carbon (g kg�1) 8�5 2�1 6�7 3�3Ca2þ (cmolc kg

�1) 0�34 0�24 0�74 0�25Mg2þ (cmolc kg

�1) 0�20 0�03 0�40 0�11Kþ (cmolc kg

�1) 0�07 0�04 0�09 0�03CEC pH 5�5 (cmolc kg

�1) 1�33 0�48 1�57 0�83Clay content (per cent) 4�9 2�9 4�9 4�7

Figure 4. Yield response of forage sorghum to selected treatments appliedto a degraded light textured soil in Northeast Thailand over two consecutiveyears. Treatments include control¼Control (current farmer practice);Dred.¼ dredged material at 240 ton ha�1; Comp.¼ leaf litter compost at10 t ha�1; Term.¼ termite mound soil at 120 t ha�1; Bent.¼ local bentoniteat 50 t ha�1 and Bent.þComp.¼ local bentonite at 50 t ha�1 with leaf littercompost of 10 t ha�1. Vertical bars are the standard error of treatment means

(Adapted from Noble et al., 2004).


M. QADIR ET AL.

conditions (Figure 6). As rainfed agriculture is practiced on

approximately 80 per cent of the agricultural land globally

and will remain the dominant source of food production

during the foreseeable future (Parr et al., 1990; Rockstrom

et al., 2003), increasing the productivity of these production

systems in order to take advantage of annual rainfall is an

important priority in maintaining global food security.

Although it may be argued that the costs of adding clay to

soils may be prohibitive, a recently completed survey of 250

farmers in the Northeast Thailand has shown that clay users

although having higher input costs both through the

application of clay material (average rate 177 t ha�1) and

higher rates of fertilizer inputs (Saleth et al., 2009).

However, due to the higher level and quality of yield, clay

famers were able to meet these costs and still achieve a much

higher net return compared to farms not using clay. For

example, the average cost per hectare of clay-using farms

was 57 per cent higher than that of non-users, but per hectare

gross revenue of the former group was twice as high. As a

result, clay-using farms had a net return that was more than

twice the net revenue of their counterparts. A comparison of

the net return values of the treated and control groups, clay

application leads to a net benefit of about 120 per cent

(Saleth et al., 2009).

Rehabilitating Abandoned Saline Irrigated Lands

Through Phytoremediation

Water logging and salinization are major constraints

affecting irrigated cotton and wheat growing regions of

Central Asia. The predominant reasons for their develop-

ment are poor irrigation water management and inadequate

drainage, rising groundwater-tables and associated mobil-

ization of primary salts within the soil profile. Bucknall et al.

(2003) report that approximately 600,000 ha of irrigated

cropland in Central Asia have become derelict over the last

decade due to water logging and salinization. It is estimated

that approximately 20,000 ha of irrigated land in Uzbekistan

is lost annually to salinity and invariably abandoned

representing a significant loss of production and, more

importantly, underutilization of irrigation infrastructure. The

conventional approach to rehabilitating these salinized areas

requires major technical expertise and investments that are

beyond the means of national budgets as well as farmers’

investment capacity in these emerging economies.

Phytoremediation is an attractive low cost option in the

rehabilitation of abandoned salinized lands that can be

undertaken by farmers. There is clear evidence in the

literature that plant-assisted approaches in the reclamation

of saline, saline–sodic and sodic soils can be achieved

through the selection of appropriate crop and plant species

(Kumar and Abrol, 1984; Robbins, 1986; Mishra et al.,

2002; Qadir et al., 2002; Qadir et al., 2007c).

The introduction of the halophyte Glycyrrhiza glabra

(commonly referred to as licorice) in the reclamation of

saline soils and the subsequent restoration of irrigated

cropping systems has been studied by Kushiev et al., 2005

on abandoned irrigated land in Uzbekistan. After four years

under a crop licorice, grown for both its roots and above

ground biomass, the field was reverted back to a cotton/

wheat rotation. The yields of both crops were significantly

Figure 5. Influence of treatments on the cation exchange capacity at threedepth intervals 8 months their application. Treatments include control¼Control (current farmer practice); Dred.¼ dredged material at 240 t ha�1;Comp.¼ leaf litter compost at 10 t ha�1; Term.¼ termite mound soil at120 t ha�1; Bent.¼ local bentonite at 50 t ha�1 and Bent.þComp.¼ localbentonite at 50 t ha�1 with leaf litter compost of 10 t ha�1. Vertical bars arethe least significant difference between treatment means at respective depthintervals (Adapted fromNoble et al., 2004). This figure is available in colour

online at wileyonlinelibrary.com/journal/ldr

Figure 6. Relationship between dry matter production and water pro-ductivity for a range of soil based treatments in Northeast Thailand.Control¼ current practices; Term¼ termite mound soil at 120 t ha�1;Comp¼ leaf litter compost at 10 t ha�1; Dredge¼ dredged material at240 t ha�1; WB¼ acid waste bentonite at 50 t ha�1; WBþLime¼ acidwaste bentonite at 50 t ha�1þ 5 t ha�1 lime; S¼ Slotting; SþB¼ Slottingþþ 50 t ha�1 bentonite; SþBþC¼ Slottingþ 50 t ha�1 bentoniteþ 10 t ha�1

compost; B¼Local bentonite at 50 t ha�1; BþC¼Local bentonite at50 t ha�1þ compost at 10 t ha�1 (Adapted from Noble et al., 2004).



higher than crops grown on adjacent saline fields (Figure 7).

Yields of wheat after licorice increased from 0.87 t ha�1 on

saline fields to 2.42 t ha�1—a 2.8-fold increase. Similarly,

cotton yields increased from 0.31 to 1.89 t ha�1—a 6-fold

increase due to the remediation effects of licorice. The

average yields of wheat and cotton for the Hungary Steppes

of Central Asia are 1.75 and 1.5 t ha�1, respectively, clearly

demonstrating the potential of licorice to increase the

productivity of these abandoned saline fields, thereby

generating increased incomes for farmers. The rehabilitation

of these abandoned saline waterlogged soils is attributed to a

combination of lowering of the water table to below 2 m; a

decrease in the total salt content of the profile due to

enhanced leaching of salt associated with improved

hydraulic conductivity; and an increase in the soil organic

carbon content over the 4-year period under licorice (Kushiev

et al., 2005). Such an approach to reclamation of abandon

saline/sodic soils offers farmers a low cost option in bringing

lands back into production. However, this approach does not

negate the need for the judicious application of irrigation water

and adequate and functional drainage.

CONCLUSIONS AND PERSPECTIVES

The fragility of our current agriculture systems was brought

into sharp focus during the recent global food crisis of 2007–

2008. It has been argued that this crisis was the confluence of

a range of drivers that included but not limited to, the effects

of competition for cropland from the growth in biofuels; low

global cereal stocks; high oil prices; speculation in food

markets; restrictions on grain exports in key countries and

extreme weather events (Nellemann et al., 2009). However,

there is an underlying causal element that is missing from

the aforementioned list, that is, the declining productive

potential of our agricultural systems that are associated with

land degradation and water quality deterioration. For

example, globally some 20 per cent of irrigated land is

salt-affected, with 2,500–5,000 km2 (250,000–500,000 ha)

lost from production every year as a result of salinity alone

(UNEP, 2008). In some countries and regions, the extent of

salt-affected soils is even greater. For instance, more than

half of the Central Asian region’s irrigated lands are affected

by varying levels of salinity and waterlogging. The largest

part of salt-affected soils and salinewaters exists in the lower

reaches of Amu-Darya and Syr-Darya Basins, where salinity

is one of the main factors threatening food production and

rural livelihoods. These are staggering figures when one

considers the investment in irrigation infrastructure alone

that is left lying idle. In addition, the policies that could

reverse the land and water resources degradation in Western

and Central Asian states are not supportive and need

attention from the respective governments for interstate

cooperation and policy-level interventions to make efficient

use of these natural resources to meet food demands and

generate employment and additional income opportunities

(Qadir et al., 2009).

The rehabilitation of degraded land and water resources

will be critical in meeting future global food demand in the

context of future climate variability and in addressing

associated negative impacts on the environment that are a

consequence of current agricultural systems. The three

examples presented offer insights into approaches that can

be used to raise the productivity of soils that have undergone

degradation due to irrigation and inappropriate land

management. Based on the first example, application of

calcium-supplying amendment, phosphogypsum, to mag-

nesium-affected soils has the potential to save 0.2m3 (200 L)

of water for each kilogram of cotton produced (Vyshpolsky

et al., 2010). Such water savings when translated to larger

scales will have considerable importance in dry regions

where land degradation and water quality deterioration are

widespread. Restoration of these degraded systems to a level

at which they are economically viable is the first step in a

process of rehabilitation. Clearly, there is a need to rethink

the way agriculture is undertaken if we are to prevent a

recurrence of these problems. Revisiting our agricultural

production systems so that they provide a sustainable level

of output along with delivering ecosystem services may offer

opportunities for maintaining and enhancing productivity.

The challenge for achieving sustainable agriculture

production systems and livelihoods lies with the establish-

ment of planned and well-coordinated changes at the

national as well as interregional levels. Thus, appropriate

supportive policies and functional institutions at the national

level would be needed to capture the potential for improving

Figure 7. Yields of cotton and wheat after of 4 years of growing licoricecompared to an adjacent saline field (Adapted from Kushiev et al., 2005)This figure is available in colour online at wileyonlinelibrary.com/

journal/ldr


M. QADIR ET AL.

agricultural productivity in general and water productivity in

particular to meet the food demands and to generate

employment and additional income opportunities. In

addition, sustainability of soil rehabilitation and pro-

ductivity enhancement would need to address capacity

building of farmers, researchers and regulatory institutions.

The farmers alone cannot tackle the huge task of

rehabilitating and managing degraded soils and marginal-

quality water resources. In addition to researchers, the

involvement of non-governmental organizations, and farmer

and water-user associations would be important to address

the long-term management and sustainability of marginal-

quality water and land resources. This would drive

community-based management of these resources to help

strengthen linkages among researchers, farm advisors and

farmers. The management options for marginal soils and

water resources built on the accumulated wisdom of relevant

stakeholders will assist in the adoption of conservation

measures at the community level. Such participatory

approaches would create a sense of ownership among the

farmers and help in strengthening linkages among farmers,

researchers and policy makers.

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adapting to climate change by improving water productivity of soils in dry areas

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