the effect of subsoiling on soil resistance and cotton yield

Soil & Tillage Research 77 (2004) 203–210

The effect of subsoiling on soil resistance and cotton yield

Ibrahim Akincia,∗, Engin Cakirb, Mehmet Topakcia, Murad Canakcia, Onal Inanca Department of Agricultural Machinery, Faculty of Agriculture, Akdeniz University, 07070 Antalya, Turkey

b Department of Agricultural Machinery, Faculty of Agriculture, Ege University, 35100 Izmir, Turkeyc Akdeniz Agricultural Research Institute, Ministry of Agriculture, Antalya, Turkey

Received 7 March 2003; received in revised form 19 November 2003; accepted 15 December 2003

Abstract

Soil compaction occurs due to heavy wheeling or repetitive tillage in the field. Soil compaction changes the soil physicalparameters and water infiltration that cause reduction in the crop yield. Proper subsoiling alleviates the negative effect ofsoil compaction. The objectives of the research was to examine the effects of subsoiling on the resistance of the soil and tofind out deep tillage effects on the cotton yield and the convenient time for applying subsoil treatment for reducing the soilcompaction. One-pass (B) and two-passes (C) subsoil treatments were applied in the fields where wheat, silage maize (Zeamays L.) and cotton (Gossypium hirsutum L.) crops were grown by 2 years rotation. The experiment was started in 1998and carried out for 4 years. Soil penetrations were measured during the experiments years at thaw conditions of silty-claysoil (43% clay, 50% silt, 7% sand) before seedbed preparation in autumn seasons. According to the results, the subsoilingtreatments created statistically significant effects on the soil resistance (P < 0.05) comparing the control plots (A). The initialdisruption in subsoiled plots has almost disappeared after 2 and 4 years in B and C plots, respectively. The soil resistancein C plots was lower than in B plot. The percentage of decrease in the soil resistance from A to B and A to C plots wascalculated as 13.3 and 26.2%, respectively, in the first year. In the effective subsoiling area from 0.20 to 0.50 m depth, theratio of penetration decrease in both plots was about 7–8% per year. The difference of penetration decrease between B andC plots was found to be about 15.8% level. Cotton yields at each subsoiled plots increased slightly comparing with controlplots (A) where subsoiling was not applied. However, these increments were found to be statistically insignificant. It may beconcluded that the subsoiling treatments does not affect the crop yield in intensive and fully irrigated field conditions.© 2004 Elsevier B.V. All rights reserved.

Keywords: Subsoiling; Soil penetration; Cotton yield

1. Introduction

At intensive agricultural land use, soil compactioncaused by wheel traffic and natural forces essentiallyaffects the soil physical properties, water infiltrationand crop performance. Soil compaction leads to soilstructure degradation, i.e. the size and number of

∗ Corresponding author. Tel.:+90-242-310-2464;fax: +90-242-227-4564.E-mail address: [email protected] (I. Akinci).

macropores is reduced. Associated with these changesare increased bulk density and soil resistance. In com-pacted layer, water, nutrients and airflow towards theplant roots are also restricted. These restrictions mayreduce the crop growth and yield.

Soil compaction plagues many parts of the worldand affects many different crops. In fields wheresoil compaction is a problem, subsoiling (also calledripping, chiseling and aerating) has been found tohelp alleviate it. Subsoiling severely compacted soilreduces the soil resistance and provides increased

0167-1987/$ – see front matter © 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.still.2003.12.006

204 I. Akinci et al. / Soil & Tillage Research 77 (2004) 203–210

rooting depth that helps the plants withstandshort-term drought conditions (Cooper et al., 1969;Campbell et al., 1974; Raper et al., 1998). Subsoil-ing enables the roots to penetrate into a deep layer.Under non-irrigated conditions, subsoiling increaseswater uptake and may lead to significantly highercrop yields. In contrast, under fully irrigated condi-tions, subsoiling could be insignificant; and in thiscase extraction of water from the subsoil is much lessimportant (Anonymous, 2002).

Tillage of any nature was considered to be thecause of accelerated mineralisation of organic matter,loss of nutrients and soil stability, and reduced in soilfauna and microbes. Zero tillage systems tend to re-tain more organic matter in the soil, most of which isheld near the surface. Non-inversion compared withinversion tillage leads to different weed populationsand species, and more targeted cultivation strategiesshould be adopted to control weed problems (Chamen,2000). In a study on using in-row subsoiling to min-imise soil compaction,Raper et al. (1998)studiedthe field traffic effect on the soil physical conditions.They examined the four cotton tillage systems alongwith two traffic applications, including a conservationtillage practice of in-row subsoiling and planting intowheat residue stubble. They got the best soil condi-tion resulted from the conservation tillage practiceof in-row subsoiling and planting. This practice pro-duced the lowest cone index and the deepest hardpandepth.

Diaz-Zorita (2000)reported that the seedbed prepa-ration using either mouldboard or chisel ploughingwith or without deep-tillage increased the vegetativeand corn yield when compared with the no-tillage sys-tem. Deep-tillage decreased significantly the penetra-tion resistance in the 0.03–0.35 m layers at seeding in1995. This effect was also observed in the 0.10–0.15 mlayers during the remainder of the 1995–1996 seasonbut not 2 years after deep-tillage treatment application.Subsoiling did not modify the corn grain yield of thecrops, which were independent of the tillage practice.

Velykis (2000)experiments showed that the effectof subsoiling depended on the method of loosening,and on the species of crops grown. He found that ahigher amount of productive moisture accumulated inthe soil loosened deeply; especially in the subsoil butsubsoil bulk density decreased only when long-rootingcrops were grown after subsoiling.

Taylor and Brar (1991)found no direct effect ofsoil compactness on root development. But they foundits indirect effect on soil physical properties such asporosity, volumetric water content, soil hydraulic con-ductivity and gaseous diffusion of the soil. Accordingto their findings, although the root development is al-tered by changes in soil compactness, the plant growthabove the ground may be normal if the plant gets suf-ficient water and nutrients.

Sommer and Zach (1992)studied the traffic inducedsoil compaction by using conservation tillage. Theyapplied five tillage methods (conventional tillage, con-servation tillage with no loosening, and with looseningwith wide blade chisel plough before winter barley,before cover crop of mustard or California bluebelland before winter barley and cover crop). They exam-ined the effect of compaction in 6 years experiment.They observed pore space on the wheel-tracked plotsof the conventional treatment was quite lower than theno-wheel-tracked plots. In general, they found no dif-ference in the plants yield between the conventionaland conservation tillage.

In a study on changes in the properties of Verti-sol and responses of wheat after compaction withharvester traffic,Radford et al. (2000)measured anarray of soil properties before and immediately afterthe application of a known compaction force to a wetVertisol. Differences in soil properties were mostlyrestricted to the top 0.20 m of the soil. The greatestmeasured depth of effect was decreased soil porosityto 0.40 m measured from intact soil clods. There was72% emergence of wheat crop planted into the com-pact soil and 93% in the uncompact soil. Wheat yieldwith a mean of 5.24 t/ha, however, was not affectedby the compaction. This may demonstrate that wheat,growing on full profile stored soil water, as did thecurrent crop, may be little affected by compaction.

Raper et al. (2000)conducted a study from 1995 to1998 to investigate conservation tillage systems thatincorporated a rye cover crop to maintain surface coverand in-row tillage to disrupt root-impeding soil lay-ers. Energy requirements for shallow tillage (0.18 m)and deep tillage (0.33 m) performed in the autumnand spring were also assessed. Factors investigated in-cluded time of tillage, dept of tillage and use of covercrop. They resulted that a rye cover crop was found tobe the largest single factor in increasing seed cottonyield. Of somewhat lesser importance, autumn tillage

I. Akinci et al. / Soil & Tillage Research 77 (2004) 203–210 205

and shallow tillage increased seed cotton yield in thoseyears. The conservation tillage practice of shallow, au-tumn, in-row subsoiling in conjunction with a covercrop may offer the best alternative for farmers trying toreduce the negative effects of subsoiling of soil com-paction, maintain adequate residue cover and improveseed cotton yield.

In a study on compaction and subsoiling effects oncorn and soybean yields and soil physical properties,Adawi and Reeder (1996)investigated that the effectof annual compaction (1987–1989) of 9 and 18 Mgaxle loads and subsoiling for a corn/soyabean rota-tion on a Hoytville silty-clay loam soil. The effect onsoil physical properties was also examined. They con-cluded that 9 and 18 Mg loads significantly reducedyields through 1992 and 1994, respectively. Measuredin 1995, soil cone index, dry density and total poros-ity were still affected by the compaction. Subsoilingthe compacted plots removed the compaction effect,and improved yields of corn and soyabean crops sub-stantially.

Several studies have been reported on soil com-paction, subsoiling effects on soil physical proper-ties and crop performance, and relationship betweensoil–machine–plant interactions. For an intensive andirrigated field farms, the effects of different subsoilingtreatments on soil resistance and determination of sub-soiling period for reducing the soil compaction havenot been explained yet.

The objectives of this study were:

• to investigate the effects of some subsoiling treat-ments on soil resistance;

• to determine the subsoiling period for reducing thesoil compaction;

• to identify the effects of deep tillage on cotton yield.

2. Materials and methods

Field experiments were conducted between 1998and 2001 at Agricultural Research and DevelopmentFarm of Akdeniz Agricultural Research Institute, An-talya, Turkey. Plots were 30 m× 30 m in size withsilty-clay soil having a texture of 43% clay, 50% silt,and 7% sand (Fig. 1).

Two different subsoiling treatments, one-pass (B)and two-passes (C) were applied in dry soil conditions

Fig. 1. Experiment design for subsoiling treatments.

after wheat harvest only in 1998 comparing controlplots (A) which received no subsoiling treatment. Thesecond pass of subsoiling was performed vertical tothe direction of the first pass for two-passes of subsoil-ing application. Completely randomised experimentaldesign with three replications was used for statisticalanalysis of the data.

Cotton was grown in 1999 and 2001; wheat andsilage maize were planted for the rest of the yearsby rotation. All field operations (soil tillage, planting,spraying, harvesting, etc.) were conventionally doneon a regular schedule as permitted by weather condi-tions. The number of operation was 12 times for wheat,19 times for silage maize and 24 times for cotton pro-duction. MF 375 tractor, 4WD and 58.2 kW enginepower was used to operate a conventional subsoilerwith a depth of 0.60 m and width of 1.65 m in row.

Soil penetrations were measured during the experi-ments from 1998 to 2001. These measurements werecarried out for each year at thaw soil before seedbedpreparation in autumn seasons. Penetration resistancewas measured by using Eijelkamp Stiboka penetrom-eter with 10.5 mm in diameter, 60◦ in angle cone. Themeasurements were made with 0.05 m increments to0.60 m depth at each location with five replications.The penetration data were averaged in depth incre-ments of 0.05 m for all replications.

Soil moisture samples were taken from each plotin range of 0.05–0.40 m depth before the penetrationmeasurements of the soil at each year. Three locationswithin each subplot were sampled. Water contents ofthe plots in years were presented inTable 1. The


Table 1Water contents of the plots in years

Soil depth (m) Water content (%)

1998 1999 2000 2001

0.00–0.10 21.2± 0.5 22.2± 0.7 21.8± 0.5 22.0± 0.20.10–0.20 23.8± 0.3 24.4± 0.5 22.7± 0.2 24.0± 0.30.20–0.30 23.9± 0.3 24.6± 0.8 23.9± 0.3 24.3± 0.40.30–0.40 24.0± 0.6 24.7± 0.5 24.2± 0.2 24.4± 0.1

statistical analysis for soil resistance and crop yieldwas performed with a standard analysis of varianceand significant means separated by the LSD test (P <

0.05).

3. Results and discussion

3.1. Soil resistance

Soil mechanical impedance in A and B and A and Cplots during the experiment years from 1998 to 2001,using with the soil penetration resistance as a functionof soil depth and experiment years, was given inFigs. 2and 3, respectively.

The soil penetration in B plot subsoiled by one-passdiffers substantially from A plot especially in first

Fig. 2. Changing of the soil resistance in B plot in time.

and second years. The initial disruption in B plothas almost disappeared after 2 years and the soilcompaction is similar to A plot received no subsoil-ing treatment. The area of low soil compaction is0.25–0.45 m depth in the first year and 0.40–0.50 mdepth in the second year. The subsoiling effectsdecrease with experiment time from 1998 to 2001(Fig. 2). These results show that the one-pass sub-soiled fields should be subsoiled at each 2 years foran intensive tilled and irrigated field farms.

The soil penetration in C plot in where two-passesof subsoiling was performed differs greatly from Aplot in all experiment years. The subsoiling effectsalso decrease during the study from 1998 to 2001.The soil compaction in plot C gets much closer toplot A after 4 years (Fig. 3). It may be concludedthat the fields subsoiled with two-passes should be


Fig. 3. Changing of the soil resistance in C plot in time.

subsoiled at each 4 or 5 years to prevent soil com-paction occurring due to heavy traffic in the field, toimprove infiltration and to increase the yield.

In both B and C treatments, the soil compactionincreases throughout the years. A similar phenomenonwas reported byMonroe and Burt (1989), Hakansson(1990), Schaffer et al. (1992)andRaper et al. (2000).Those cases mainly depend on soil properties, wheeltraffic and natural forces.

In 1998, the first year of the experiments, the pen-etration resistance and its percentage of decrease in

Table 2Subsoiling effect on soil resistance in the first year

Soil depth (m) Soil resistance (MPa) Percentage of decrease

A B C A–B A–C

0.10–0.15 1.23 a 1.11 a 1.04 a 9.8 15.40.15–0.20 1.26 a 1.18 ab 0.98 b 6.5 22.10.20–0.25 1.45 a 1.13 b 1.09 b 22.4 25.20.25–0.30 1.62 a 1.22 b 1.11 b 24.8 31.80.30–0.35 1.79 a 1.44 b 1.15 c 19.4 35.40.35–0.40 1.89 a 1.41 b 1.14 c 25.5 39.60.40–0.45 1.97 a 1.56 b 1.21 c 21.0 38.90.45–0.50 2.04 a 1.87 b 1.43 c 8.4 29.70.50–0.55 2.11 a 2.07 a 1.81 b 2.1 14.40.55–0.60 2.20 a 2.25 a 2.01 a −2.6 8.6

Mean 1.76 a 1.52 ab 1.30 b 13.3 26.2

Different letters indicate the statistical difference in rows (P < 0.05).

A–C plots, were given inTable 2. The effect of sub-soiling on C plot was greater than in B plot. So, thesoil resistance in C plot was also found smaller than inB plot. The effective subsoiling area in both plots wasfrom 0.25 to 0.45 m and 0.20 to 0.50 m depth, respec-tively. This result can be explained by the subsoilingoperations are two-passes in C plot and one-pass in Bplot.

The means of soil resistance in A–C plots werefound to be 1.76, 1.52 and 1.30 MPa and, the percent-age of decrease from A to B and A to C plots were


Fig. 4. Percentage of penetration decrease in B and C plots in time.

calculated as 13.3 and 26.2%, respectively. In the firstyear, the percentage of decrease in plot C was abouttwo times greater than in plot B. The subsoiling treat-ments showed statistically significant effects on thesoil resistance (P < 0.05).

In the effective subsoiling area from 0.20 to 0.50 mdepth, the percentage of penetration decrease due tothe years in B and C plots was illustrated inFig. 4.The percentage of penetration decrease in both Band C plots linearly decreases with experiment timefrom 1998 to 2001. These trends can also be usedto estimate the subsoiling periods. The ratio of pen-etration decrease in both plots was about 7–8% peryear. The main point of that the soil was regularlycompacted from year to year due only to the effectof field traffic. In percentage of penetration decrease,a significant difference between B and C plots wasabout 15.8% level. This result can be attributed tothe two-passes of subsoiling operation was more ef-fected on the soil disruption than subsoiling withone-pass.

In the absence of subsoiling, the two-passes ofsubsoiling operation is more effective method thansubsoiling with one-pass for overcoming the soilcompaction. This method may be suitable treatmentfor improving the soil physical characteristics. How-ever, farmers should consider the power, fuel, timeand labour consumptions for choosing the subsoilingmethods.

Fig. 5. Subsoiling effect on cotton yield.

3.2. Crop yield

In the experiment, only cotton yield was taken intoconsideration. Subsoiling effects on the cotton yieldsin years of 1999 and 2001 were illustrated inFig. 5.The cotton yields in B and C plots slightly increaseat each growing periods comparing with control plotA. The cotton yields in A–C plots were obtained as4.00, 4.15 and 4.30 t/ha in 1999 and 3.65, 3.94 and4.19 t/ha in 2001, respectively. Also, the percentage ofyield increase in B and C plots was about 3.75 and7.50% in 1999 and, 7.95 and 14.8% in 2001, respec-tively (Fig. 5). However, these increments were foundto be statistically insignificant (Table 3). TheP valueswere found at 0.126 and 0.075 for year and treatments,respectively. This value for subsoiling treatments wasvery close to theP > 0.05 limit. There seems to havea difference regarding the subsoiling treatments espe-cially between plots A and C in same years according

Table 3ANOVA table for subsoiling effect on cotton yield

Source of variation d.f. Mean squareF (counted) P value

Year (Y) 1 0.224 2.665 n.s. 0.126Treatment (T) 2 0.271 3.218 n.s. 0.075Y × T 2 0.021 0.251 n.s. 0.783

n.s.: not significant.


to the statistical results. The difference between thesubsoiling treatments in the same year vanishes af-ter certain year due to the changing soil conditionsthrough the years. Although there was found no sta-tistically difference between the years and the treat-ments.

A similar phenomenon was reported byRadfordet al. (2000)for wheat,Raper et al. (2000)for cottonand Anonymous (2002)at specific soil physical andnutritional conditions. In contrast, some researcher re-ported that deep tillage was greatly affected on cropgrowth and yield such as irrigated cotton, corn andsoybean and dryland corn (Adawi and Reeder, 1996;Coelho et al., 2000; Diaz-Zorita, 2000; Raper et al.,2000). This variation especially depends on soil andclimate properties, growing conditions and efficientwater use in plant production.

4. Conclusions

1. The soil penetration in both plots one-pass andtwo-passes subsoiled is much smaller than no sub-soiled plots. The two-passes of subsoiling treatmentin C plot is more effective method than one-passin B plot for reducing the soil compaction. Thistreatment may allow farmers to improve their soilphysical properties and crop yield.

2. The soil resistance, after the subsoiling, increaseswith the time from year to year. The subsoiling pe-riod was determined as 2 years for one-pass and4–5 years for two-passes. So, the fields should besubsoiled at the time of subsoiling periods to pre-vent the soil compaction occurring due to the in-tensive farming and heavy traffic in the field.

3. The measurements indicated that, at intensive andirrigated field farms, subsoiling the soils withtwo-passes and one-pass treatments increases thecotton yield. However, no statistical sound conclu-sion could be drawn on the effect of subsoiling oncrop yield.

Acknowledgements

This project was supported by Ministry of Agri-culture in Turkish Republic and Scientific Research

Fund of Akdeniz University and carried out withAkdeniz University, Faculty of Agriculture and Ak-deniz Agricultural Research Institute cooperation,Antalya, Turkey.

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the effect of subsoiling on soil resistance and cotton yield

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