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Ecological Engineering 58 (2013) 434– 440

Contents lists available at ScienceDirect

Ecological Engineering

j ourna l ho me pa g e: www.elsev ier .com/ locate /eco leng

odic soil reclamation potential of Jatropha curcas: A long-term study

ripal Singha,b,∗, Bajrang Singha, Rakesh Tuli c

Restoration Ecology Group, CSIR – National Botanical Research Institute, Rana Pratap Marg, Lucknow 226001, Uttar Pradesh, IndiaDepartment of Environmental Science, Babasaheb Bhimrao Ambedkar (Central) University, Raibarelly Road, Lucknow 226 025, Uttar Pradesh, IndiaNational Agri-Food Biotechnology Institute, Mohali 160 071, Chandigarh, India

r t i c l e i n f o

rticle history:eceived 19 January 2013eceived in revised form 22 May 2013ccepted 4 July 2013vailable online 15 August 2013

eywords:iomassnzyme activitiesicrobial biomass

rosopis julifloraodic soils

a b s t r a c t

Jatropha curcas L. (JCL) has been identified as a biodiesel plant globally. Efforts are underway to domesticateJCL for high seed yield. The plant has potential to grow on marginal/degraded/substandard lands to avoidcompetition with food crops, but little is known about its potential to reclaim degraded lands. At thisstudy, several accessions of JCL were planted in 2005 on sodic soil to assess soil amelioration potentialof the plant. After six years (2011) of plant growth, seed yield was not economically viable; however,soil properties improved significantly when compared to initial (0-year plantation) soil properties at0–15 cm soil depth. Random soil samples were collected from 0 to 15 cm soil depth beneath and outsidecanopies of JCL with high, medium and poor growth in the year 2008 (3-year plantation) and 2011 (6-yearplantation). Soil bulk density, pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP)decreased and soil organic carbon (SOC), nitrogen (N), phosphorus (P), microbial biomass (MB-C, MB-Nand MB-P) and enzyme activities (dehydrogenase, �-glucosidase and protease) increased significantlywith effect of JCL plantation. Significant decrease in soil pH, EC and ESP has been noticed from 8.6 to7.6, 1.29 to 0.98 dS m−1 and 20.7% to 13.8%, respectively. Similarly, soil fertility parameters like SOC,MB-C, dehydrogenase, �-glucosidase and protease increased significantly from 4.55 to 8.41 g kg−1, 98 to352 �g g−1, 16.3 to 51.2 �g TPF g−1 h−1, 75.8 to 338.2 �g PNP g−1 h−1 and 43.7 to 163.2 �g Tyrosine g−1 h−1,respectively after 6 years of JCL cultivation on sodic soil. Changes in soil properties were significantly

higher beneath the canopy than outside canopy. Soil sodicity parameters (bulk density, pH, EC and ESP)and fertility attributes (SOC, N, P, MB and enzymes) were significantly negatively and positively correlatedwith the height, biomass and litter fall of JCL, respectively. Furthermore, to test whether changes in soilproperties are induced by test crop, changes were compared with Prosopis juliflora plantation of sameage, which is generally planted for amelioration of sodic soils. The significant decrease in soil sodicity and

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. Introduction

Jatropha curcas L. (JCL) has been widely accepted as a biodiesellant which is supposed to contribute significantly in biodiesel pro-uction all over the world (Francis et al., 2005). Global attention oniofuel, ecosystem services, human well-being and utilization ofegraded lands with JCL plantations, has created a hyped inter-st in this species (Everson et al., 2012). Until now JCL is a wildpecies but has ample scope in the production of biodiesel. It has

een speculated that JCL has potential to: reclaim marginal lands,equester atmospheric CO2 (aboveground and belowground), grownder saline and sodic conditions, and use less water (high water

∗ Corresponding author at: Department of Environmental Science, Babasahebhimrao Ambedkar (Central) University, Raibarelly Road, Lucknow 226 025, Uttarradesh, India. Tel.: +91 8858355269.

E-mail addresses: kripalsingh04@gmail.com (K. Singh),singh471@rediffmail.com (B. Singh).

m2iotepco

925-8574/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.ecoleng.2013.07.006

e that JCL is equally good to reclaim the sodic soils.© 2013 Elsevier B.V. All rights reserved.

se efficiency) (Francis et al., 2005; Achten et al., 2008). It is alsolaimed as drought tolerant, has less nutrient requirement, lowabor inputs and does not compete with food production if culti-ated on marginal lands. The plant is tolerant to pests and disease,asily propagated and has a small gestation period (Abhilash et al.,011). Consequently, JCL is a potential biofuel plant for sustainablenvironmental development (Pandey et al., 2012).

Recently, some of the physiological traits (water relations,tomatal conductance, drought stress and photosynthetic perfor-ance) in seedlings of JCL have been investigated (Maes et al.,

009, 2011; Achten et al., 2010; Ranjan et al., 2012), which supportts drought tolerance. Additionally, field performance of a numberf accessions of JCL has also been monitored to optimize agro-echnology (Behera et al., 2010; Srivastava et al., 2011; Everson

t al., 2012; Singh et al., 2013a,d). Soil carbon sequestrationotential of JCL plantations has been assessed in varying edaphiconditions (Srivastava et al., 2012; Wani et al., 2012). Restorationf fly ash landfills and phytoremediation of heavy metals from fly

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sh dykes through JCL plantations was addressed by Jamil et al.2009). Effect of reclaimed water irrigation on cultivation of JCLas recently investigated (de Miguel et al., 2013) to use reclaimedater as a complementary local energy option.

Although JCL plantation may results in soil fertility benefits andosses those were not included in above studies. Two recent studiesave investigated the effect of organic amendment on growth per-

ormance of JCL planted on a completely barren and degraded landn the Sahelian area of Burkina Faso following three restorationechniques (sub-soiling, half-moon and Zai) to conserve soil andater (Kagamebga et al., 2011; Sop et al., 2011). A study on the con-

ribution of JCL to increase structural stability and carbon–nitrogenontent in a degraded Indian entisol is also available in the liter-ture (Ogunwole et al., 2008). Similarly, Wani et al. (2012) havessessed land rehabilitation through JCL by measuring soil organicarbon, microbial biomass and microbial counts in a range of semi-rid degraded lands. In another study, JCL influenced the microbialommunity structure significantly in rhizosphere soils (Chaudharyt al., 2012). In the rhizosphere soils of JCL, fungi were higherhan bacteria and actinomycetes (Chaudhary et al., 2012) whichontribute greatly in soil amelioration as fungal hyphae promoteggregation of soils (Gupta and Germida, 1988).

Sodic soils are widely distributed in arid and semiarid part ofhe world and pose a serious environmental problem as a miss-ng sink for sequestration of atmospheric carbon dioxide (Singht al., 2013b). Sodic soils are characterized by high levels of soil pH>8.5), exchangeable sodium percentage (ESP) and insoluble CaCO3Shukla et al., 2011). Additionally, these soils showed poor micro-ial and enzyme activities (Singh et al., 2012b). Several efforts haveeen made to reclaim these soils through chemical and organicmendments (Gill et al., 2009). Phytoremediation techniques arelso in practice (Bhojvaid and Timmer, 1998; Rahi and Singh, 2013;ingh et al., 2012a,b). The monoculture plantation of Terminaliarjuna, Prosopis juliflora, Eucalyptus spp. and Albizia procera andstablishment of mixed forests for phytoremediation of degradedodic lands have been extensively adopted in semi-arid regionsBhojvaid and Timmer, 1998; Mishra and Sharma, 2003; Tripathind Singh, 2005; Haper et al., 2012; Vallejoa et al., 2012). Recently,ingh et al. (2013c) reported the potential of Cynodon dactylon forhe revegetation of abandoned sodic lands. The changes in physical,hemical and microbial properties of afforested sodic soils are likelyo depend on the age and species composition of the introduced

egetation. Mechanisms and processes driving phytoremediationf sodic soils have already been discussed in detail (Qadir et al.,002, 2007). In brief, plantation on calcareous sodic soils assists innhancing the dissolution rate of calcite (CaCO3) through plant–soil

10Ji

ig. 1. A view of Jatropha curcas plantation, [A] an intact plant showing luxuriant groworresponding author.

ering 58 (2013) 434– 440 435

nteraction resulting in increased levels of Ca2+ in soil solution,ncrease in partial pressure of CO2 due to root and microbial res-iration and release of H+ from plant roots to increase in Ca2+ andecrease soil pH and Na+ (Qadir et al., 2002, 2007).

As JCL is recommended for cultivation on degraded soils; there-ore, it is important to assess its effectiveness to reclaim suchoils. Furthermore, as degraded lands are rehabilitated with JCLrop, focus has been on changes in soil carbon sequestration (Wanit al., 2012). Little attention has been paid to assess the impactsf JCL plantation on the microbial activities of rhizosphere soils.herefore, it is proposed to study the changes in physical, chem-cal (carbon, nitrogen and phosphorus) and biological (microbialiomass and enzyme activities) properties of sodic soil as a resultf JCL plantation. Changes in soil properties were measured using ahronosequence (0, 3, and 6 years) to obtain a clear understandingf the potential of JCL to reclaim sodic soils. It was hypothesized thatCL plantation may reduce soil sodicity and enhance soil microbialnd enzyme activities.

. Materials and methods

.1. Study site

The study was conducted at Banthra Research Station of CSIR National Botanical Research Institute, Lucknow (26◦40′–45′ N0◦45′–53′ E), India. The study site has an average (2006–2011)nnual rainfall of 950 mm. The average daily temperature for thetudy site is varied from 42 ◦C (maximum) during summer (June–ugust) to 6 ◦C (minimum) during winter (November–January).he soil is classified as Typic Halaquepts with poor drainage,rownish gray color, yellowish brown mottles and silty clay tex-ure. The soil was alkaline (pH = 8–10, ESP = 45–90%, SAR = 4–25%)ith a calcareous layer throughout the soil profile (0–100 cm). Theetails of the sodic soils of this site can also be found in Singh et al.2012a,b).

.2. JCL plantation, experimental approach and soil sampling

A total of 24 accessions of JCL were planted in a completely ran-omized block design (RBD) with four replicates in 45 cm3 refilledits with the same soil at a spacing of 2.5 m × 2.5 m (within a rows well as between rows), corresponding to a density of about

600 plants ha-1 in September 2005. The plantation covers about.5 hectare (ha) area. Fig. 1 shows growth and plant architecture ofCL. The field was irrigated after the plantation and subsequentlyn summer season as and when required. The objective of this

th on sodic soil and [B] plant architecture from bottom to top. Photograph by

4 Engineering 58 (2013) 434– 440

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Table 1Growth performance of Jatropha curcas after six years of plantation (September2005–September 2011).

Growth parameters Plant groups

High growth Medium growth Poor growth

Height (cm) 325.9 ± 17.5 232.2 ± 17.6 146.9 ± 31.6Stem diameter (cm) 9.60 ± 0.75 7.45 ± 0.52 5.57 ± 0.57Branches (number) 48.0 ± 5.90 34.7 ± 2.92 29.1 ± 3.00Canopy spread (cm) 251.7 ± 30.8 170.0 ± 17.5 102.4 ± 19.9Total biomass (kg plant−1) 24.6 ± 3.35 14.4 ± 1.58 9.55 ± 0.61

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lantation was to assess growth performance and seed yield ofeveral accessions of JCL on sodic soils as well as to observe theirffectiveness in amelioration of sodic soils. The findings of growtherformance and seed yield of different accessions have been pub-

ished (Singh et al., 2013d) and in this paper soil amelioration iseported.

Several random soil cores (15 cm soil depth, 4 cm diameter)ere collected in July 2005 from sodic land to know the actual

tatus of soil sodicity and fertility before JCL plantation. Initial soilroperties of plantation site are presented in tables as 0 year data.ut of total plantation, 54 plants were marked to assess ameliora-

ion potential of JCL in September 2008 (at 3 year growth). Theselants were further divided in three subgroups (eighteen for each)ith high, medium and poor growth to correlate plant growth dataith soil properties. Four random soil cores were taken at 50 cm

adius from the each plant stem (beneath canopy) and compositedo generate three samples for each growth group. Similarly, outsideanopy samples were taken from open interspaces between plants.oil samples were taken in September 2008 and 2011, and wereieved (2 mm), placed in plastic bags, transported to the laboratorynd divided in two parts for physicochemical and biological soilnalyses. One part of soil samples were air dried to analyze physico-hemical soil properties and other stored at laboratory temperatureor fifteen days before biological analysis.

.3. Soil analysis

Soil bulk density was calculated through known volume ofteel core and weight of soil sampled by core at a time. KR boxethod was applied for the measurement of water holding capacity

Kalra and Maynard, 1991). Soil particle distribution was ana-yzed with International Pipette method described by Kalra and

aynard (1991). Soil pH and electrical conductivity (EC) was esti-ated using soil:water (1:2) suspension with digital pH meter. Soil

rganic carbon (SOC) was determined by the Walkley and Blackichromate oxidation method (Kalra and Maynard, 1991). Totalitrogen was estimated with H2SO4 digestion and steam distil-

ation method (Kalra and Maynard, 1991) and available nitrogenas determined using KMnO4 solution followed by steam distilla-

ion (Kalra and Maynard, 1991). Extraction of available phosphorusas done with NaHCO3 (Kalra and Maynard, 1991). Exchange-

ble sodium (Na+) was extracted in 1 N CH3COONH4 (ammoniumcetate) and analyzed with atomic adsorption spectrophotometerKalra and Maynard, 1991). Microbial biomass (MB-C, MB-N, and

B-P) was estimated by the fumigation–extraction methods asuggested by Vance et al. (1987) and Brookes et al. (1982, 1985). Thectivities of soil enzymes, dehydrogenase, �-glucosidase and pro-ease were determined with the methods described by Tabatabai1994).

.4. Statistical analysis

Data was subjected to two way analysis of variance using aPSS Statistical Software SYSTAT 16.0 to determine the significancef growth years and canopy treatments on different soil proper-ies. Correlation coefficients (r2) were also determined with linearegression analysis to observe effect of growth parameters on soilroperties (SPSS 16.0). Results are presented as arithmetic meansf three measurements with their standard deviations.

. Results and discussion

.1. Tree growth, biomass and litter fall

Variation in height and biomass is a natural feature in planta-ions crops as JCL attained the maximum 326 cm and minimum

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Leal fall (kg plant−1 year−1) 1.95 ± 0.05 1.15 ± 0.09 0.95 ± 0.16

47 cm height with about 24.6 and 9.55 kg biomass (oven dry)lant−1 at 6 year of growth (Table 1). This might be due to dif-erent accessions of genetic variability or soil heterogeneity. Therowth of JCL in present study was similar to that of Srivastavat al. (2011) but different from Behera et al. (2010). Srivastavat al. (2011) found maximum 254 cm height at soil with 7.85 pHnd 3.60 g kg−1 SOC and minimum 190 cm height at soil with 7.54H and 4.60 g kg−1 SOC at 3 year growth of JCL. However, JCLttained maximum 141 cm height at soil treated with VAM (Vas-ular Arbuscular Mycorrhyza) and minimum 57 cm in agroforestryith Azadirachta indica (Behera et al., 2010) at same age. These

ariations might be due to status of planting material and inherentoil properties of study sites. Good growth performance of JCL atresent study site might be due to drought avoidance (low waterse efficiency) (Maes et al., 2009) and salt tolerant strategies of thelant. Even after salt tolerance strategies in JCL, there is a recenttudy in which JCL was inoculated with plant growth promotinghizobacterium, Enterobacter clocae (MSA), Pseudomonas pseudoal-aligenes (MSC) and Bacillus sp., with a mycorrhizal fungus, Glomusntraradices, to increase seed germination, vegetative growth, min-ral nutrient uptake in leaves and enhance antioxidant enzymectivities, phosphatase activity, solute accumulation under salineonditions, where the performance of JCL was not so good (Patelnd Saraf, 2013). Sodic soils have less water available for cropsue to high salt concentration in the soil solution (low osmoticotential) at which crop growth is negatively affected. JCL required

ess water so grew well on sodic soils. Furthermore, JCL planta-ion received life saving irrigation, during summer (36–40 ◦C), withespect to yield perspectives; which also played an important roleo reduce the sodicity stress.

.2. Effect of JCL plantation on physicochemical soil properties

The effect of JCL plantation on physicochemical properties ofodic soil was observed at 0 (before plantation), 3 and 6 year growthtages (Table 2). Differences in water holding capacity (WHC) andulk density were significant (P < 0.05) beneath the canopy of 3nd 6 year JCL plantation, when compared to control (before plan-ation) soil and outside canopy soils. Sodic soils generally have low

HC and high bulk density which inhibit the water movement andeaching of salts from the surface (Singh et al., 2012b). Increase in

HC beneath canopy can be explained by development of superfi-ial root carpet (Achten et al., 2008) due to vegetatively propagatedlants. The root system of JCL is shallow which enhances the pro-ortion of macropores to micropores which in turn result in higherHC and lower bulk density. As a result of JCL plantation, meaneight diameter of the soil and soil aggregate stability increased

1% and 2%, respectively. However, with application of nitrogen

nd phosphorus or without any amendment aggregate stabilitymproved from 6% to 30%. Soil structure recovery under cultivationf JCL implies a sustainable improvement in the surface integrity of

K. Singh et al. / Ecological Engineering 58 (2013) 434– 440 437

Table 2Physicochemical properties of soils beneath and outside canopy of Jatropha curcas L. at 0, 3 and 6 years growth stage. Mean ± SD (n = 3).

Physicochemical soil properties 0 year 3 year 6 year

No plantation Beneath canopy Outside canopy Beneath canopy Outside canopy

WHC (%) 36.3 ± 1.52 40.0 ± 5.29a* 36.7 ± 3.05A 43.5 ± 1.25b* 38.6 ± 4.16A

Bulk density (g cm−3) 1.55 ± 0.08 1.38 ± 0.06a* 1.48 ± 0.08A 1.24 ± 0.12b* 1.50 ± 0.01A

pH 8.60 ± 0.15a 8.00 ± 0.24a 8.36 ± 0.15A 7.60 ± 0.15b* 8.20 ± 0.20A

EC (dS m−1) 1.29 ± 0.05a 1.12 ± 0.12a 1.41 ± 0.18A 0.98 ± 0.11b* 1.35 ± 0.09A

Na+ (c mol kg−1) 2.12 ± 0.12 1.88 ± 0.38a* 2.06 ± 0.12A 1.92 ± 0.32a* 2.15 ± 0.25A

K+ (c mol kg−1) 1.79 ± 0.21 1.88 ± 0.23a* 1.82 ± 0.34A 1.92 ± 0.24a 1.93 ± 0.25A

Ca++ (c mol kg−1) 5.50 ± 0.50 6.82 ± 0.60a* 6.20 ± 0.20A 8.78 ± 0.22b* 5.65 ± 0.98B

Mg++ (c mol kg−1) 0.87 ± 0.10 1.28 ± 0.15a* 1.35 ± 0.12A 1.15 ± 0.15a 1.15 ± 0.13A

ESP (%) 20.7 ± 1.14 16.0 ± 2.05a 18.0 ± 1.44A 13.8 ± 1.84b* 19.6 ± 0.75A

SOC (g kg−1) 4.55 ± 0.39 6.40 ± 0.38a* 5.00 ± 0.95A 8.41 ± 0.15b* 5.10 ± 0.15A

Nitrogen (�g g−1) 39.7 ± 3.68 53.0 ± 1.73a* 43.0 ± 3.60A 57.0 ± 6.80b* 48.0 ± 3.50B

Phosphorus (�g g−1) 35.3 ± 2.51 43.5 ± 1.15a* 37.6 ± 1.52A 48.5 ± 5.20b* 38.5 ± 3.05A

EC, electrical conductivity; WHC, water holding capacity; ESP, exchangeable sodium percentage; SOC, soil organic carbon.V nt at

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egraded Indian entisol, which will ensure more water infiltrationather than runoff and erosion (Ogunwole et al., 2008).

Significant decrease in soil pH and EC was observed only in soilseneath canopy of JCL after 6 year of growth. In agreement witharlier studies (Qadir et al., 2002; Tripathi and Singh, 2005; Singht al., 2012a,b) phytoremediation of sodic soils thorough JCL culti-ation reduces the soil pH and EC. Soil respiration (CO2 emission),rganic matter decomposition and root exudates may be respon-ible for reduction in pH of sodic soils. Carbon dioxide emissionCO2 emission) from soil by microbial respiration, root respirationnd faunal respiration increases partial pressure of CO2 in sodicnvironment which mainly initiate the reclamation process as fol-ow: (i) dissolution of CO2 in water to form H2CO3, (ii) dissociationf H2CO3 resulting in H+ (reduce soil pH) and HCO3

−, (iii) reaction+ with soil CaCO3 to produce Ca++, (iv) increased concentrationf Ca++, replace Na+ from exchange complex, (v) leaching ofeplaced Na+ in percolating water through root channels and (VI)ronounced reduction in soil sodicity (pH, EC and ESP) (Qadir et al.,002; Mishra and Sharma, 2003; Mishra et al., 2004; Qadir et al.,007). Organic matter (added by leaf litter and root mortality)n decomposition produces organic acids (humic and fulvic) thateduce soil pH. Root exudates are made up of organic acids, sugars,mino acids, hormones and mucilage (Jamaluddin and Shukla,012) that also play important role to reduce soil pH. We foundignificant decrease in ESP beneath canopy at 3 and 6 year growthge of JCL in comparison to control, while ESP outside canopy6 year) was significantly higher than that of beneath canopy

Table 2). The ESP declined more markedly beneath canopy due toncreased availability of Ca++. This difference can be explained inart by the fact that maximum dissolution of native calcite (CaCO3)ccurs beneath canopy in presence of maximum organic matter.

t3ii

able 3iological properties of soils beneath and outside canopy of Jatropha curcas L. at 0, 3 and 6

Biological soil properties 0 year 3 year

No plantation Beneath canopy

MB-carbon (�g g−1) 98.0 ± 6.55C 230.0 ± 13.2a*

MB-nitrogen (�g g−1) 16.0 ± 1.94C 82.70 ± 6.80a*

MB-phosphorus (�g g−1) 15.6 ± 3.51C 30.50 ± 4.95a*

Dehydrogenase (�g TPF g−1 h−1) 16.3 ± 1.92A 48.8 ± 3.56a*

�-Glucosidase (�g PNP g−1 h−1) 75.8 ± 10.6C 330.0 ± 12.2a*

Protease (�g Tyrosine g−1 h−1) 43.7 ± 10.2A 146.2 ± 8.78a*

B, microbial biomass.alues with the different lowercase letters (a, b) are significantly different at P < 0.05 benalues with the different uppercase letters (A, B) are significantly different at P < 0.05 out* Significantly different at P < 0.05 beneath and outside of canopy of particular growth

P < 0.05 between growth years beneath canopy. P < 0.05 between growth years outside canopy.year.

onsidering the fact that sodic soil reclamation is accomplished byroviding a source Ca++, most of the sodic soils contain a source ofa++ i.e. calcite at varying depth within the soil profile (Qadir et al.,007).

When compared to control soil, significant increase in SOCas found beneath canopy of 3 and 6 year JCL growth; however,

utside canopy differences were not significant, while differencesn SOC were also significant between beneath and outside canopyTable 2). Wani et al. (2012) reported that carbon increased in theegraded surface soil layer by 19%, resulting in about 2500 kg ha−1

oil carbon sequestration during 4 years of JCL cultivation. Maxi-um SOC beneath canopy of JCL may be correlated to leaf fall and

ne root mortality. Development of vegetation cover on degradedodic land incorporates substantial organic matter in the soilystem which alters physicochemical and biological properties.artial increase in SOC outside canopy, 9% and 11% may alsoe ascribed to weed growth and their mulching during manualeeding and irrigation.

.3. Effect of JCL plantation on biological soil properties

The growing trees of JCL (biomass production and litter fall),ontribute to reduce soil sodicity, increase soil organic matternd consequently enhance biological processes in sodic soils. Inomparison to 0-year plantation (before plantation), significantncrease in soil microbial biomass (MB-C, MB-N and MB-P) andctivities of soil enzymes (dehydrogenase, �-glucosidase and pro-

ease) have been observed beneath as well as outside canopy at

and 6 year growth (Table 3). This indicates that root systemnteracts with sodic soil (rhizospheric interaction) to deliver pos-tive effect on soil microbial biomass and enzyme activities.

years growth stage. Mean ± SD (n = 3).

6 year

Outside canopy Beneath canopy Outside canopy

132.0 ± 11.8A 352.0 ± 6.08b* 211.0 ± 11.5B

48.00 ± 6.08A 126.6 ± 4.60b* 68.00 ± 6.00B

19.00 ± 4.58A 50.00 ± 5.30b* 38.50 ± 6.50B

15.1 ± 2.88A 51.2 ± 9.14b* 29.0 ± 4.58B

85.4 ± 9.60A 338.2 ± 10.1a* 115.4 ± 6.36B

48.5 ± 6.88A 163.2 ± 10.4b* 97.6 ± 12.5B

eath canopy of different growth years.side canopy of different growth years.year.

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ncreased microbial activity promotes decomposition of organicatter and recycling of the nutrients in the sodic soils. It has been

iscussed well that plantations (pure, mixed or agroforestry) canmprove soil quality through sequestration of atmospheric CO2o soil system (Bhojvaid and Timmer, 1998; Pandey et al., 2011;ingh et al., 2012a,b). Similarly, in this study the supply of litter,oot mass and rhizospheric associated microbial activities mighte responsible for enhanced microbial biomass and enzyme activ-

ties beneath canopy. We found higher increase in MB at old agelantation than young plantation when compared to initial values.

t was 48% and 10% higher than values observed by Behera et al.2010) in three year old JCL plantation. The relatively higher con-entration of MBC in current study can probably be ascribed tohe long term (6 years) C and N inputs through JCL biomass. Singht al. (2012a) have observed that sodic land under phytoremedia-ion through crop cultivation exhibited increases in MB-C, MB-Nnd MB-P by 81%, 66% and 49%, respectively at 0–30 cm soil depth.hese values are close to those found in this study, with 58%, 81%,nd 48% and 73%, 88%, and 60% increase in soil MB (C, N and P)eneath canopy at 3 and 6 year old JCL plantations, respectively.ani et al. (2012) reported 22% and 24% increase in MBC and MBN,

espectively in the rhizosphere of JCL in comparison to adjacentrassland. Litter and root turnover and standing biomass increasedith plants age which had direct positive effect on clustering of soilicrobial communities (Singh et al., 2012a).JCL plantation enhanced the activities of enzymes involved

n the cycling of carbon (dehydrogenase and �-glucosidase) anditrogen (protease) (Table 3). The activities of soil enzymes wereignificantly (P < 0.05) higher beneath canopy at 3 and 6 yearsrowth in comparison to 0 year plantation as well as outside canopyTable 3). The higher inputs and diversity of ground vegetationesidues under canopy provides substrate for microbial growth andtimulation of enzyme production. The enzyme activities dependn substrate quantity and quality, enzyme localized in root cells,oot remains, microbial cells, microbial cell debris, microfaunalells, root exudates (Chaudhary et al., 2012) and free extracellularnzymes in the soil colloids (Nannipieri et al., 2003). On averag-ng the data of both the years, we found 3.5 times increase inehydrogenase and protease activities but increase in the activ-

ty of �-glucosidase was 4.5 times higher in comparison to 0 yearlantation. This indicates that chemistry (carbon and nitrogen) ofrganic matter received from JCL plantation may favor the produc-

ion of �-glucosidase. Root exudates of JCL promote colonization ofrbuscular mycorrhizal fungi, which in turn improve the soil bio-ogical health and growth of JCL (Jamaluddin and Shukla, 2012). Thencreased level of SOC by 29% beneath canopy at 3 years of growth

able 4elationship (r2*) between growth parameters (height, biomass and litter fall) andoil properties of JCL planted on sodic soils (n = 9).

Soil properties Growth parameter

Height Biomass Litter fall

Water holding capacity 0.81 0.59 0.75Bulk density −0.68 −0.62 −0.64pH −0.85 −0.89 −0.82Electrical conductivity −0.82 −0.79 −0.76Exchangeable sodium percentage −0.81 −0.88 −0.78Organic carbon 0.89 0.88 0.87Total nitrogen 0.88 0.90 0.92Microbial biomass carbon 0.98 0.94 0.93Microbial biomass nitrogen 0.95 0.93 0.90Microbial biomass phosphorus 0.90 0.89 0.89Dehydrogenase 0.78 0.69 0.65�-Glucosidase 0.78 0.73 0.67Protease 0.83 0.77 0.73

* Significant at P < 0.001.

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ed to increase in activities of dehydrogenase, �-glucosidase androtease by 67%, 77% and 71%, respectively. While 46% increase inOC beneath canopy after 6 year of growth led increase in activitiesf soils enzymes almost similar (69%, 78% and 74%) to that of 3 yearCL plantation. This indicates that increase in availability of organic

atter on bare sodic land through leaf fall and fine root biomassf JCL enhances the activity of soil enzymes maximum during ini-ial growth phase (3 year). In later years increase in nutrient (C and) availability suppressed enzyme activities through negative feed-ack mechanism. For instance, microbes produce enzymes perhapsnly when availability of substrate is sufficient and enzymes canelp to release nutrients and therefore lead in microbial growthnd metabolism (Shi, 2011; Singh et al., 2012c). This enzyme pro-uction can be low when the end products (C and N in this study)f enzymatic reaction, are abundant (Shi, 2011).

.4. Effect of JCL growth, biomass production and litter fall on soilroperties

Soil physicochemical and biological properties were correlatedith height, biomass and litter fall to determine the effect of JCL

n soil properties (Table 4). Soil sodicity parameters (bulk density,H, EC and ESP) and fertility attributes (SOC, N, P, MB and enzymes)ere significantly negatively and positively related to the height,

iomass and litter fall, respectively. Significant negative effect ofrowth parameters on soil sodicity showed that increase in growthf JCL played an important role to reduce soil sodicity and increaseoil fertility.

.5. Potential of JCL to reclaim sodic soils

P. juliflora (PJ) has been used extensively for reclamation ofodic soils in northern India (Garg, 1999; Mishra and Sharma, 2003;ishra et al., 2004; Singh et al., 2012b) as well as in other countries

Vallejoa et al., 2012). On the other hand this tree provides gooduality of fuelwood for rural mass. Therefore, to assess the recla-ation potential of JCL, we selected 3 and 6 year old monoculture

lantation of PJ developed for reclamation of sodic soils adjacent tour study site (see Mishra and Sharma, 2003; Mishra et al., 2004).hanges in soil physicochemical properties due to effect of PJ plan-ation are presented in Table 5. Increase in desirable (WHC andOC) and decrease in undesirable (bulk density, pH, EC and ESP)oil properties with effect of PJ and JCL plantations, calculated fromables 2 and 5, are presented in Fig. 2. Increase in WHC was almostqual to P. juliflora after three years of growth; however, at 6 yearrowth WHC was significantly higher at JCL planted site. Similarly,oil pH decreased significantly much at JCL planted sites in com-

arison to P. juliflora planted site. However, the contribution of P.

uliflora was little higher to increase SOC and decrease ESP. Thisndicates that buildup of soil organic matter through JCL planta-ion is less than P. juliflora. This might also be due to leguminous

able 5ffect of Prosopis juliflora plantation on physicochemical properties of sodic soil after

and 6 year of growth.

Plant height and soil properties 0 year 3 year 6 year

Height (cm) 0.00 1.00 1.25WHC (%) 43.3 47.8 48.7Bulk density (g cm−3) 1.66 1.37 1.24pH 9.77 9.64 9.05EC (dS m−1) 1.90 1.05 0.87ESP (%) 70.6 26.9 18.1Organic carbon (g kg−1) 2.00 3.90 6.60Total nitrogen (g kg−1) 0.18 0.45 0.60

ource: Mishra and Sharma (2003) and Mishra et al. (2004).

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ig. 2. Reclamation effect (%) of Prosopis juliflora (PJ) and Jatropha curcas (JCL) plan-ations on properties of sodic soil after 3 and 6 years of growth.

ature of P. juliflora (easily decomposable litter), quality and quan-ity of fallen litter and fine roots, and ground layer vegetation atoth the planted sites.

. Conclusions

This study supported the assumptions (Francis et al., 2005;chten et al., 2010; Abhilash et al., 2011; Pandey et al., 2012) that

CL has potential to reclaim degraded lands. JCL plantation reducesoil sodicity (bulk density, pH, EC and ESP) and improves the fertil-ty (soil organic carbon, microbial biomass and enzyme activities)n accordance with growth and age of the plantation. Our hypoth-sis that JCL plantation on sodic soils would improve soil qualityas confirmed in part by the results of this study. As this is natu-

al to be, the reclamation efficiency of JCL was significantly highereneath canopy than outside canopy. In future interspaces betweenCL plants should be utilized for cultivation of local shade lovingwarf crops those can grow on sodic soils. This will ensure returnsnd provide greater amount and diversity of plant residues foraximum carbon storage in sodic soils.

cknowledgements

The study was supported by Council of Scientific and Indus-rial Research (CSIR), New Delhi, India under the New Millenniumndian Technology Leadership Initiative (NMITLI) program as apecial grant (CSIR-NMITLI) in eleventh five year plan of gov-rnment of India (GOI). We are thankful to Director, Nationalotanical Research Institute, Lucknow, for constant support andritical advice to complete this work. Kripal Singh expressesis sincere thank to the CSIR for Senior Research Fellowship31/8/(233)2009/EMR-1). Thanks to anonymous reviewer for hisseful suggestions.

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