Soil & Tillage Research 77 (2004) 169–177

Pot study on wheat growth in saline and waterloggedcompacted soil

I. Grain yield and yield components

Muhammad Saqib∗, Javaid Akhtar, Riaz Hussain QureshiDepartment of Soil Science, University of Agriculture, Faisalabad, Pakistan

Received 24 April 2003; received in revised form 14 November 2003; accepted 15 December 2003

Abstract

The information of soil compaction effects on growth and yield of crops for saline and waterlogged soils is scanty. A potexperiment was conducted on a sandy clay loam soil during 2001–2002 to study the interactive effects of soil compaction,salinity and waterlogging on grain yield and yield components of two wheat (Triticum aestivum) genotypes (Aqaab andMH-97). Compaction was achieved at 10% moisture level by dropping 5 kg weight, controlled by a tripod stand for 20times from 0.6 m height on a wooden block placed inside the soil filled pots. Soil bulk density of non-compact and compacttreatments was measured as 1.21 and 1.65 Mg m−3, respectively. The desired salinity level (15 dS m−1) was developed bymixing the required amount of NaCl in soil before filling the pots. Waterlogging was developed by flooding the pots for 21days both at tillering and booting stages. Compaction aggravated the adverse effect of salinity on grain yield and different yieldcomponents of both the wheat genotypes. Average reduction in grain yield was 44% under non-compact saline conditionsagainst 76% under compact saline conditions. Similarly, the reduction was about 20% more for 100 grain weight and shootlength, 30% more for number of spikelets per spike, 37% more for number of tillers per plant, and 32% more for straw weightin compact saline treatment than in non-compact saline treatment. Compaction alone caused a reduction of 36% in grain yield.The effect of waterlogging on grain yield and yield components was mostly not changed significantly due to compaction.Rather waterlogging mitigated the effect of compaction for most of the yield components except for number of spikes perplant. Therefore, as for normal soils, the cultivation of salt-affected soils should employ implements and techniques whichminimize compaction of root zone soil. The effect of soil compaction can also be minimized by light irrigations with shortintervals and by using a stress tolerant crop genotype.© 2004 Elsevier B.V. All rights reserved.

Keywords: Salinity; Waterlogging; Compaction; Wheat; Grain yield; Yield components

∗ Corresponding author. Present address: Institute für Pflanzen-ernährung, Interdisziplinäres Forschungszentrum, UniversitätGießen, Heinrich Buff Ring 26-32, 35392 Gießen, Germany.Tel.: +49-641-9939164; fax:+49-641-9939169.E-mail address: drhmsab@yahoo.com (M. Saqib).

1. Introduction

In modern agriculture, soil compaction is a ma-jor cause of low crop yields. Frequent and un-timely cultural operations by heavy implements usu-ally cause a compaction hazard. Soil compactioncauses unfavorable changes in soil bulk density,porosity and soil–water relationships (Soane et al.,

0167-1987/$ – see front matter © 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.still.2003.12.004

170 M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177

1981; Alakukku and Elonen, 1994; Shafiq et al.,1994).

The degraded soil physical environment due to com-paction retards root and shoot growth, which resultsin low crop yields. Compacting a clay loam soil toa density of 1.52 Mg m−3 from an initial density of1.33 Mg m−3 reduced the grain and straw yields ofwheat by 12–23 and 9–20%, respectively (Oussibleet al., 1992). In another study,Ishaq et al. (2001a)ob-served 38 and 9% reductions in grain and straw yields,respectively, of wheat when soil was compacted to abulk density of 1.93 Mg m−3 from an initial bulk den-sity of 1.65 Mg m−3.

Salt affected and waterlogged soils are a seriousthreat to the sustainability of irrigated agriculture. Ex-cessive salts present in the root zone adversely af-fect the plants at all growth stages. Salinity decreasesgermination (Bernardo et al., 2000a), leaf cell expan-sion and ultimate leaf growth (Cramer et al., 2001),leaf area and dry matter accumulation, the rate of netCO2 assimilation, and relative growth (Bernardo et al.,2000b). Waterlogging on the other hand decreases theavailability of oxygen to the plants and disturbs thehydro-mineral uptake (Morard and Silvestre, 1996).

Compact horizons that impede root growth usuallyresult from the forces applied to the soil by imple-ments and animals, and may develop as frequentlyunder saline soil as under non-saline soil conditions.Also surface crusting and the presence of a dense layerat any depth in the root zone of salt-affected soilsalso simulate the conditions of a compact soil hori-zon, hence restricting root penetration and aggravatingthe problems for plant growth.Ilyas (1988)reportedthat silt and a higher Na+ or sodium adsorption ratio,as well as crust formation, were the major problemsof sodic soils that affected seed germination and laterplant growth.

Soil compaction and other soil physical stresseshave been studied and documented widely (e.g.Kaspar et al., 1991; Unger and Kaspar, 1994; Lal,1996; Ishaq et al., 2001a,b). Similarly, the plant re-sponse to salinity and waterlogging has also been thesubject of many studies (e.g.Barrett-Lennard, 1986;Nawaz, 1993; Akhtar et al., 1994, 1998; Saqib et al.,1999, 2000). However, research work on the effectsof soil compaction on plant growth in relation tosalinity and waterlogging is scanty in Pakistan. Theobjective of this study was to assess the effects of

soil compaction on grain yield and yield componentsof two wheat genotypes (Aqaab and MH-97) undersaline and waterlogged conditions.

2. Materials and methods

2.1. Site

This study was conducted in outdoor conditions ina wire house (with walls and roof of iron net) at theDepartment of Soil Science, University of Agricul-ture, Faisalabad, Pakistan, during the year 2001–2002.Faisalabad is situated at 73.4◦ longitude and 31.5◦ lat-itude.

2.2. Treatment application

There were two sets of compaction treatments,namely non-compact and compact soil. In each set,four treatments were applied, viz. control (electricalconductivity of the saturated soil extract (ECe) mea-sured by EC meter: 2.6 dS m−1), waterlogging (flood-ing for 21 days at the tillering and booting stages),salinity (ECe: 15 dS m−1) and salinity×waterlogging.The treatments were replicated five times in a com-pletely randomized factorial arrangement. The soilused was non-saline non-sodic in nature with sandyclay loam texture (sand: 53.5%; silt: 24%; clay:22.5%). The soil has been under cultivation withwheat cotton crop rotation.

Soil was passed through a 2 mm sieve and filledin glazed earthen pots, with 12 kg per pot (height:0.31 m; diameter: 0.23 m). Compaction levels wereachieved at 10% moisture level (on dry mass basis) bydropping a 5 kg weight, controlled by a tripod standfor 20 times from a 0.6 m height on a wooden block(width/height: 0.05 m; diameter: 0.18 m) placed insidethe soil filled pot. The soil bulk density of non-compactand compact treatments was measured as 1.21 and1.65 Mg m−3, respectively, by core method (Blake andHartge, 1986). The desired salinity levels were devel-oped by mixing the required amount of NaCl in soilbefore filling the pots. Waterlogging was developed byflooding the pots for 21 days at the tillering as well asat booting stage. The 21 days include the last 5–6 daysthat pots took to come to the normal non-waterloggedconditions. During first 15 days of the waterlogging

M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177 171

treatment, the waterlogging was maintained by mak-ing up water level daily up to 0.01 m above the soilsurface. After 15 days pots were allowed to cometo normal dry conditions by evaporation and plantuse but with out draining. Other than the period ofwaterlogging, pots were irrigated when needed.

2.3. Seed source and raising of plants

The seeds of two wheat genotypes (Aqaab andMH-97) were collected from the Saline AgricultureResearch Centre, University of Agriculture, Faisal-abad, Pakistan. Aqaab is a relatively salt tolerantgenotype while MH-97 is relatively sensitive to salt(Saqib, 2002). The wheat crop was sown on 17November 2001 and harvested on 29 April 2002.

The recommended doses of NPK fertilizers at120–60–60 kg ha−1 were applied in the form of urea,single super phosphate and sulfate of potassium, re-spectively. The pots were irrigated with tap waterhaving an electrical conductivity (EC) 0.90 dS m−1.At soil water content about half of the field capacityconditions the soil was pulverized and the seeds weresown at a depth of 0.01 m. After germination, threeuniform seedlings were selected and the remainingwere uprooted.

2.4. Data collection

At maturity, plants were harvested and threshedmanually. The data regarding grain and straw yieldsand 100 grain weight, number of spikes per plant,number of tillers per plant, spike length, number ofspikelets per spike and shoot length were recorded.The meteorological data during the study period aregiven inTable 1.

Table 1Average monthly temperature, relative humidity and sunshine hours at University of Agriculture, Faisalabad during November 2001–April2002

Parameters November December January February March April

Minimum temperature (◦C) 12.3 6.0 4.8 7.8 13.2 19.8Maximum temperature (◦C) 27.5 23.2 16.4 24.2 29.1 33.9Minimum RH (%) 49.8 47.8 68.7 42.7 39.9 35.8Maximum RH (%) 78.2 83.7 91.6 78.1 70.0 59.0Daily sunshine (h min) 6–58 7–25 5–13 7–59 9–05 8–35

RH: relative humidity.

2.5. Statistical analysis

Data were analyzed statistically for analysis of vari-ance (ANOVA) following the methods described byGomez and Gomez (1984). MSTATC computer soft-ware was used to carry out the statistical analysis(Russell and Eisensmith, 1983). The significance ofdifferences among means was compared by using thestandard error. The standard error was computed ass/

√n, wheres is the standard deviation andn shows

the number of observations.

3. Results

3.1. Yields of wheat

3.1.1. Grain yieldUnder non-compact soil conditions, salinity, wa-

terlogging and saline–waterlogged treatments signifi-cantly reduced the grain yield of both the wheat geno-types as compared to the control (Fig. 1). The ad-verse effect of salinity was significantly more thanthat of waterlogging, while the salinity×waterloggingtreatment caused a significantly greater reduction thansalinity alone for MH-97 only.

The compaction× control treatment also reducedthe grain yields of both the genotypes significantlycompared to the non-compact control. The compactiontreatment also aggravated the adverse effects of salin-ity, and salinity× waterlogging treatments, but it didnot significantly alter the effect of waterlogging alone.However, the compaction× waterlogging treatmentproduced greater grain yield than the compaction×control treatment and, in the case of the wheat geno-type MH-97, the difference was significant. Also, incompact soil conditions, the salinity× waterlogging

172 M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177

0

1

2

3

4

5

6

7

Cont Wal Sal S x W Cont Wal Sal S x W

Non-compact

Gra

in y

ield

(g

pe

r p

lan

t)Aqaab MH-97

Compact

Cont.= Control, Sal.= Salinity, Wal.= Waterlogging, S x W = Salinity x waterlogging

Fig. 1. Effect of soil compaction on grain yield (g per plant) of wheat under saline and waterlogged conditions.

treatment produced significantly higher grain yieldthan salinity alone, which shows a mitigating effect ofcompaction even under saline soil conditions. Aqaabproduced significantly greater grain yield than MH-97in all the treatments except the non-compact controland the compact waterlogged treatments.

3.1.2. Straw weightThe straw weight of both the wheat genotypes was

decreased significantly by the salinity and salinity×waterlogging treatments, compared to the control un-der non-compact soil conditions (Fig. 2). The soil

0

2

4

6

8

10

12

14

16

Cont Wal Sal S x W Cont Wal Sal S x W

Non-compact

Str

aw

we

igh

t (g

pe

r p

lan

t)

Aqaab MH-97

Compact

Fig. 2. Effect of soil compaction on straw weight (g per plant) of wheat under saline and waterlogged conditions.

compaction (compaction×control treatment) also sig-nificantly decreased the straw weight of both the wheatgenotypes as compared to the non-compact control.However, the straw weight of Aqaab as well as MH-97in the compaction× waterlogging treatment was sig-nificantly higher than in the compaction×control treat-ment. The lowest straw weight was recorded in thecompact saline treatment, and it was also significantlyless than that in non-compact saline conditions, show-ing an intensification of the adverse effect of salin-ity by soil compaction. The two genotypes respondedsimilarly in the various treatments.

M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177 173

0

1

2

3

4

5

Cont Wal Sal S x W Cont Wal Sal S x W

Non-compact Compact

100-g

rain

wt. (

g)

Aqaab MH-97

Cont.= Control, Sal.= Salinity, Wal.= Waterlogging, S x W = Salinity x waterlogging

Fig. 3. Effect of soil compaction on 100 grain weight (g) of wheat under saline and waterlogged conditions.

3.2. Yield components of wheat

3.2.1. Grain weightSalinity and waterlogging alone, and in combina-

tion, caused a significant reduction in the 100 grainweight of both the wheat genotypes as compared tothe control in non-compact soil (Fig. 3). The depres-sive effects of the salinity and salinity× waterloggingtreatments were significantly greater than for water-logging alone.

The compaction× control treatment also signifi-cantly reduced the 100 grain weight of both the wheatgenotypes. The compaction also aggravated the ad-verse effect of salinity significantly, but not of water-logging and salinity× waterlogging. Aqaab produceda higher 100 grain weight than MH-97 in all the treat-ments.

3.2.2. Spike lengthThe spike length of both the wheat genotypes

was decreased significantly due to the salinity andsalinity×waterlogging treatments in non-compact soilconditions, as compared to the control (Table 2, PartA). Waterlogging, however, did not decrease the spikelength of Aqaab significantly while it decreased thespike length of MH-97 significantly as compared tothe non-compact control. The salinity× waterloggingtreatment caused a significantly higher reduction thansalinity alone.

The compaction× control treatment significantlydecreased the spike length of MH-97 but not of Aqaabas compared to the non-compact control. The com-paction also accentuated the adverse effect of salinityfor both the genotypes. The development of waterlog-ging, however, decreased the compaction effect undernon-saline and saline soil conditions, resulting in anincreased spike length compared to the compaction×control and compaction× salinity treatments, respec-tively. Aqaab produced a significantly higher spikelength than MH-97 in all the stress treatments.

3.2.3. Number of spikelets per spikeThe salinity and salinity× waterlogging treatments

significantly reduced the number of spikelets per spike(NSS) of both the wheat genotypes as compared tothe control in non-compact soil conditions (Table 2,Part B). Waterlogging, however, caused a significantreduction in the NSS of MH-97 only.

The compaction× control treatment also decreasedthe NSS of both the genotypes significantly. Com-paction did not alter the effect of waterlogging, butit significantly increased the effect of salinity on boththe genotypes, as compared to respective non-compacttreatments. The genotypes Aqaab and MH-97 differedsignificantly only in the saline, saline waterlogged andcompaction× control treatments, and here the NSSof Aqaab was always significantly higher than that ofMH-97.

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Table 2Effect of soil compaction on performance of two wheat genotypes under normal, saline and waterlogged conditions

Non-compact Compact

Genotypes Control Waterlogging Salinity Salinity×waterlogging

Control Waterlogging Salinity Salinity×waterlogging

A: Spike length (cm)Aqaab 10.67± 1.25∗ 9.67 ± 0.47 8.67± 0.47 7.00± 0.41 9.00± 0.82 9.33± 0.47 4.67± 0.47 6.67± 0.62MH-97 9.00± 0.82 7.67± 0.47 6.00± 0.82 4.67± 0.33 7.00± 0.82 7.33± 0.47 3.33± 0.47 4.17± 0.51

B: Number of spikelets per spikeAqaab 17.00± 2.16 14.00± 2.10 12.67± 2.16 11.50± 1.63 13.00± 0.82 13.67± 1.25 6.83± 1.03 10.67± 1.25MH-97 16.67± 0.94 13.33± 1.70 9.33± 0.94 8.50± 0.82 11.33± 0.47 11.83± 1.43 4.83± 1.25 8.33± 1.70

C: Number of spikes per plantAqaab 3.33± 0.47 3.0± 0.82 1.67± 0.47 1.0± 0.00 2.80± 0.82 2.33± 0.47 1.00± 0.00 1.0± 0.00MH-97 3.73± 0.47 2.67± 0.47 1.33± 0.47 1.0± 0.00 1.67± 0.47 1.67± 0.47 1.00± 0.00 1.0± 0.00

D: Shoot length (cm)Aqaab 76.00± 4.97 76.67± 6.02 67.00± 2.83 62.67± 4.19 68.33± 4.71 74.00± 1.41 53.00± 4.97 61.00± 3.74MH-97 74.33± 1.25 71.33± 2.62 62.33± 2.05 53.67± 3.86 59.67± 3.49 67.00± 7.48 46.00± 3.74 54.67± 2.62

∗ Mean of five values± S.E.

M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177 175

3.2.4. Number of spikes per plantIn non-compact soil conditions, the salinity and

salinity×waterlogging treatments caused a significantreduction in the number of spikes per plant (NSP) ofboth the wheat genotypes as compared to the control(Table 2, Part C). The saline waterlogged treatmentcaused a significantly higher reduction than salinity.Waterlogging alone, however, significantly decreasedthe NSP of MH-97 only.

The compaction×control treatment reduced signifi-cantly the NSP of MH-97, but not of Aqaab. It also ag-gravated the effect of salinity and waterlogging, but thechange was not significant for Aqaab in case of water-logging. Compaction, however, did not alter the effectof the salinity×waterlogging treatment. The responseof two genotypes also differed non-significantly underall the treatments.

3.2.5. Shoot lengthSalinity alone, and in combination with waterlog-

ging, significantly reduced the shoot length of boththe wheat genotypes in non-compact soil conditions(Table 2, Part D). The shoot length of MH-97 was alsosignificantly lower in the saline waterlogged treatmentthan in saline alone.

The compaction×control treatment caused a signif-icant reduction in shoot length of MH-97 as comparedto the non-compact control. Compaction did not ac-

0

1

2

3

4

5

6

Cont Wal Sal S x W Cont Wal Sal S x W

Non-compact Compact

Num

ber

of tille

rs p

er

pla

nt

Aqaab MH-97

Cont.= Control, Sal.= Salinity, Wal.= Waterlogging, S x W = Salinity x waterlogging

Fig. 4. Effect of soil compaction on number of tillers per plant of wheat under saline and waterlogged conditions.

centuate the adverse effects of salinity×waterlogging,but it did increase the effect of salinity. Aqaab pro-duced significantly higher shoot length than MH-97in the non-compact salinity× waterlogging andcompaction× control treatments.

3.2.6. Number of tillers per plantThe number of tillers per plant (NTP) of both the

wheat genotypes was reduced significantly due to thesaline and salinity× waterlogged treatments undernon-compact soil conditions (Fig. 4). The adverse ef-fect of salinity×waterlogging was significantly higherthan that of salinity alone.

The compaction× control treatment caused a sig-nificant decrease in the NTP of both the wheat geno-types as compared to the non-compact control. Soilcompaction did not alter the effect of the waterlog-ging and salinity×waterlogging treatments. However,compaction intensified the effect of salinity, signifi-cantly. Both the genotypes also produced statisticallythe same NTP in each treatment.

4. Discussion

Compaction aggravated the adverse effect of salin-ity on yield and yield components of both the wheatgenotypes. Average reduction in grain yield of both the

176 M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177

genotypes relative to control was 44% in non-compactsaline conditions against 76% in compact saline con-ditions. Similarly, the reduction was about 20% morefor 100 grain weight and shoot length, 30% more fornumber of spikelets per spike, 37% more for numberof tillers per plant and 32% more for straw weight incompact saline treatment than in non-compact salinetreatment.

Compaction alone caused a reduction of 36 and 34%in grain and straw yields, respectively. The reductionin yield components due to compaction was mostly inthe range of 15–30%. This reduction in grain and strawyields and different yield components may be due todecreased soil porosity and permeability and increasedroot penetration resistance as a result of increased soilbulk density in compact soil conditions. The move-ment of air and water is also restricted in a compactsoil layer causing problems for root growth. Similareffects of compaction on grain and straw yields havealso been reported earlier byOussible et al. (1992)andIshaq et al. (2001a).

Salinity caused 44 and 46% reduction in the grainand straw yields, respectively, which may be due tothe water stress, ion imbalance and ion toxicity un-der saline conditions over the growth period of plants.Akhtar et al. (1994)andSaqib et al. (1999)have alsoreported decreased grain yield due to salinity.

The data of this experiment show that compactionand salinity interacted to cause a reduction higher thandue to their individual effects. Greater reduction ingrain yield and various yield components due to com-pact saline conditions may be due to poor root elonga-tion growth and reduced soil exploration due to com-paction coupled with reduced water and nutrient up-take and utilization under saline conditions. This isalso evident from reduced concentrations of Na+, K+and Cl− and K+:Na+ ratio in leaf sap under compactsaline conditions compared with non-compact salinetreatment (companion paper).

The effect of waterlogging on grain yield and yieldcomponents was mostly not changed significantlydue to compaction. Rather waterlogging mitigatedthe effect of compaction. Although the differencesremained non-significant for most of the yield com-ponents. However, straw weight of both the geno-types and grain yield of MH-97 only, increasedsignificantly under compact-waterlogging treatmentcompared with compact control. A negative corre-

lation between soil water contents and penetrationresistance has been observed (Shafiq et al., 1994).Waterlogging of a compact soil therefore, decreasedthe penetration resistance and favored the root growththat improved plant growth and yield. The improvedroot growth is evident from more root length den-sity in compaction× waterlogging treatment than incompaction× control treatment (companion paper).Thus, it may be possible to circumvent the adverseeffects of compaction by keeping the soil sufficientlymoist so that soil strength does not seriously ham-per root penetration. Similar views have also beenexpressed byUnger and Kaspar (1994).

The imposition of waterlogging in addition to salin-ity reduced the salt tolerance of both the wheat geno-types as assessed on the basis of growth and yield re-duction. Oxygen deficiency due to waterlogging undersaline conditions accentuates the problems for plantsby reducing the production and availability of energy(Barrett-Lennard, 1986) which in turn reduces the abil-ity of plants to control the accumulation of toxic levelsof Na+ and Cl−, and to maintain K+ accumulation andK+:Na+ ratio in its growing leaves (Saqib et al., 1999).As in the case of waterlogging alone, the response ofwheat genotypes to salinity× waterlogging treatmentwas also not affected significantly due to impositionof compaction except for grain yield. However, com-pared to compact saline treatment, the performance ofboth the genotypes under compact saline waterloggedconditions was better for many of the yield compo-nents that shows a decrease in compaction stress byoccasional waterlogging for a few days even undersaline soil conditions.

Genotypic comparison under various treatmentsshowed a relatively better performance by Aqaab thanMH-97 particularly in saline and saline waterloggedtreatments under compact as well as non-compact soilconditions. It shows that a genotype selected againstsalinity and waterlogging in controlled conditions canalso give better results in field even in the presenceof other allied stresses like compaction.

5. Conclusions

Soil compaction of a salt-affected soil resulted ina more drastic effect on plant growth and yield thancompaction of normal soil. However, occasional wa-

M. Saqib et al. / Soil & Tillage Research 77 (2004) 169–177 177

terlogging of a soil for few days decreased the com-paction stress, both under non-saline as well as salineconditions. The decrease was less in non-saline thanin saline soil conditions. Therefore, like normal soils,in salt-affected soils also such cultivation implementsand techniques should be used that result in a less com-paction of the root zone. The effect of soil compactioncan also be minimized by light irrigations with shortintervals and by using a stress tolerant crop genotype.

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