effect of homogeneous and heterogeneous soil compaction on shoot and root growth of field bean and...

J. Agronomy & Crop Science 157, 105—113 (1986)© 1986 Paul Parey Scientific Publishers, Berlin and HamburgISSN 0044-2151

Aus dem Institut fur Acker- und Pflanzenbau der Universitdt Hohenheim

Effect of Homogeneous and Heterogeneous Soil Compactionon Shoot and Root Growth of Field Bean and Soybean

G. KAHNT, L. A. HIJAZI and M. RAO

Authors' address: Prof. Dr. G. KAHNT, Dr. L. A. HIJAZI and Dr. M. RAO, Institut fiir Acker-und Pflanzenbau der Universitat Hohenheim, Fruwirthstr. 23, D-7000 Stuttgart 70, F.R.G.

With eight figures

Received October 2, 1985; accepted February 11, 1986

Abstract

The study was done to observe the effects of soil compaction on field bean and soybeangrowth in greenhouse. Plastic cylindrical tubes of 58 cm height and 12 cm diameter were filledwith silty loam soil with three bulk densities i.e., low (1.25 g/cm^), medium (1.45 g/cm^) andhigh (1.65 g/cm^) either separately or in combination of low/medium (level 1), low/high (level 2)and medium/high (level 3) as top and sub-soil densities.

General effect of compaction was a reduction in shoot and root growth and in yield of boththe legumes; probable reason seemed to be mechanical impedance. At homogeneous compac-tion throughout the soil profile high bulk density decreased the root dry matter from 6 to 32 %and total root length from 30 to 57% but total root volume was not much affected due tothickening of the roots. From 4 to 31% reductions were also observed in shoot dry matter.Increase in only subsoil density from medium to high (level 2) decreased shoot and root drymatters (8 to 36% and 16 to 39%, respectively) but not the total root length. Plant growth wasmore hampered when both top and subsoil densities were increased (level 3) but the total rootlength was not highly affected in the upper (0 to 20 cm) and middle (20 to 40 cm) layer.

I. Introduction

The adverse effect of soil compaction on plant growth is an integration of multidirec-tional influences produced by compaction hke reduced O2 supply to the roots (BERTRAND

and KoHNKE 1957, FLOCKERet al. 1959), lower soil — water content (WARKENTIN 1971) anddecreased rate of water movement (GRUMBS and WARKENTIN 1972). These hazards furthercreate a problem of nutrient availability (AMER and BARTHOLOMEW 1951, KEMPERet al. 1971)and their absorption by plants (PHILLIPS and KIRKHAM 1962, SILBERBUSH et al. 1983). Allthese factors along with increased resistance to root penetration (DREW and Goss 1973)resuk in a stunted root growth (WIERSUM 1957, SCOTT and ERICKSON 1964). The cumulativeworking of all these factors is a reduced crop yield.

In our field experiments field beans performed better than soybeans in compacted plots.For a better understanding of the processes it was decided to study root and shoot growthof these legumes in pots with different compactions.

U.S. Copyright Clearance Center Code Statement: 0044-2151/86/5702-0105$02.50/0

106 KAHNT, HIJAZI and RAO

II. Material and Methods

The experiment was done in a glasshouse, in summer 1981, in plastic cylindrical tubes of58 cm height and 12 cm diameter. The homogeneous bulk densities in 0—50 cm soil profiletaken are as under:

Bulk densities Total pore volume

1.25 g/cm^ 49.6% (Low)1.45 g/cm' 46.4% (Medium)1.65 g/cm^ 44.1% (High)

To create heterogeneous soil profile following combinations of soil bulk densities were taken:

low (1.25 g/cm^) upper 20 cm soil(level 1; control)

med. (1.45 g/cm^) lower 30 cm soil

low (1.25 g/cm^) upper 20 cm soil(level 2)

high (1.65 g/cm^) lower 30 cm soil

med. (1.45 g/cm-') upper 20 cm soil(level 3)

high (1.65 g/cm"̂ ) lower 30 cm soilA silty loam soil was mixed with 30 % sand with the following chemical analysis of the

mixture:Total N 0.18%

C 1.40%C : N 7.8P2O5 14.5K2O 31.2pH 6.5

field capacity 23.0%Upper 20 cm of soil was mixed with P and K at the rate of 100 and 150 kg/ha P2O5 and K2O,

respectively before filling the pots. Two kg coarse sand was put at the bottom of each tube. Toget a uniform germination upper 4 cm of soil was loosened. Cultivars used were Cieso (soybean)and Skladia (field bean). The plants were harvested after 4, 5, 7 and 12 weeks in homogeneousand after 4, 8 and 12 weeks in heterogeneous soil profile experiments after sowing. Watering wasdone at 70% field capacity. The treatments were replicated 4 times.

III. Results

The results of homogeneous and heterogeneous soil compaction experiments on shootand root growth of plants are presented together.

Dry weight of above ground parts: The results in Figure 1 showed the first decrease indry matter yield due to high density at second harvest i.e., after 5 weeks. This decrease wasobserved till the last harvest; the registered decrease being 10% and 6% in field bean andsoybean, respectively. No appreciable differences between low and medium densitytreatments were found. In heterogeneous soil profile (Fig. 2) compaction combinationsalso caused a decrease in weight, which became greater with time. As for example fieldbean reduced its dry weight by 21 and 32% at level 2 and level 3, respectively, thecorresponding values for soybean are 14 and 36%.

Dry root weight: To estabhsh the zones of the root concentration soil profile wasdivided into three parts i.e., 0 to 20 cm (layer a), 20 to 40 cm (layer b) and 40 to 50 cm(layer c). At first two harvests only field bean showed a decrease in root weight due to highcompaction (Fig. 3). The effect of compaction at third harvest was not very clear m both

Effect of Homogeneous and Heterogeneous Soil Compaction 107

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Fig. 3. Effect of homogeneous soil compaction on the dry root weight in upper (a), middle (b)and lower (c) layer and the total root dry weight of field bean and soybean at four different

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crops. At the final harvest clear cut decrease in total root weight due to compaction wasregistered for both crops. A change in soil bulk density from 1.25 to 1.65 g/cm^ brought adecrease of 21 and 25 % for field bean and soybean, respectively. A major part of this totalweight reduction came from lower layer. Differences among upper layers and amongmiddle layers were not significant except soybean which produced higher root weight inthe middle layer at medium bulk density.

The adverse effect of compaction showed itself in heterogeneous soil profile too (Fig^ 4).In the first harvest the effect was only seen at third level, but it became noticeable at all

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Fig. 5. Effect of homogeneous soil compaction on the root volume in upper (a), middle (b) andlower (c) layer and the total root volume of field bean and soybean at four different harvests

levels from second harvest onwards. At second harvest a decrease of 16 % and 25 % in fieldbean and soybean, respectively was registered in total root dry matter at level 2. Drop intotal root weight almost in all cases came mostly from middle and lower layers showingthat the effect of compaction increased with increase in plant age.

Root volume: The effect of compaction on root volume started becoming clear at secondharvest (Fig. 5). An increase in bulk density from medium to high caused a decrease of 30and 47 % in field bean and soybean, respectively. At third harvest in the upper layer anincreasing trend was found with the increase in bulk density. No differences were observedin the middle layer. In the lower layer increase in bulk density from 1.25 to 1.65 g/cm^decreased the root volume from 4.6 to 0.59 cmVpot in field bean and from 5.95 to2.05 cmVpot in soybean. At final harvest higher bulk density increased the root volume ofboth crops in the upper layer. In the middle layer increasing the density from low tomedium increased the root volume, but a further increase caused a decrease. Similarlyevery increase in density caused a decrease in root volume in the lower layer; the decreasebeing up to 91 and 68 % in field bean and soybean, respectively.

In heterogeneous soil profile (Fig. 6) both crops reacted differently to soil compaction.At all harvests field bean showed a decrease in root volume due to compaction, whereas insoybean it was produced only at level 3. At first harvest field bean produced up to 95%more root volume than soybean in control, but this increase rapidly decreased with timeproducing only 28.6% more at final harvest.

Root length: At first harvest an increase in bulk density from 1.25 to 1.65 g/cm^ causedfield bean to reduce its total root length from 38.5 to 19.7 m/pot and soybean from 33.8 to16.2 m/pot (Fig. 7). This effect went through second harvest. At third harvest no effect ofcompaction was found in the upper layer. In the middle and lower layer root length wasgreatly decreased. At final harvest the influence of bulk density could not be seen on fieldbean root length in the upper layer, whereas a reduction of 27% was found in soybean by achange in density from low to high. In the middle layer root length was increased with anincrease in density from low to medium; the increase was 5.1 m/pot in field bean and 5.6 m/pot in soybean, but a further increase in the density rapidly decreased the root length by 27


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Fig. 6. Effect of heterogeneous soil compaction on the root volume in upper (a), middle (b) andlower (c) layer and total root volume of field bean and soybean at three different harvests

and 47 % in field bean and soybean, respectively. In the lower layer each increase in bulkdensity reduced the root length in both crops.

The results from heterogeneous soil profile in Figure 8 show no clear cut effect ofcompaction at first harvest, but at second harvest total root length of field bean was

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decreased from 43.1 m/pot at level 1 to 27.3 m/pot at level 3, the corresponding decrease insoybean was from 49.8 to 33.8 m/pot. In the upper and middle layer differences amongcompaction levels were not clear, whereas in lower layer root length was reduced by about66 % with the change in level from 1 to 3 in both crops. Soybean produced more total rootlength than field bean but differences were not significant. At third harvest similar trendwas found too.

IV. Discussion

Adverse effects of compaction on plant growth are well known, equally known is thevarying ability of different plants to coup up with this menace. This ability of plants isrelated to their root systems. Our studies revealed important differences in root as well asin top development associated with the differences in soil bulk densities. Root growth canbe influenced by many factors such as nature of the soil, fertihty, water supply, andaeration etc. Since the same soil, fertilizer rate and water supply were used for all the pots,these factors may not have hampered the root growth. Several investigators (FLOCKER et al.1959, VEiHMEYERand HENDRICKSON 1948, and others) stated that for a number of importantcrops the aeration level appears to be about 10—15 %. As the air filled porosity of the usedprofiles was much higher than this range it might not have affected the root growth either.It IS then presumed that mechanical impedance may be mainly responsible for theobstruction of root growth. It is known from the experiments of WIERSUM (1957) that rootscan only pass through pores of a size exceeding the diameter of the root tip. This impliesthat the root must exert a certain force upon the soil particles in order to penetrate intodeeper layers. From Figures 2 to 4 the influence of bulk density of homogeneous soilprofile on root growth in first and second harvest shows no clear differences in rootvolumes even though total root length in high density soil was considerably less than in


other densities. This tendency continued till the final harvest. The roots grown incompacted media, as many researchers stated (WIERSUM 1957, BALiGARet al. 1975, CAMP andLUND 1968, PRiHARet al. 1971), fail to elongate but expand radially causing the roots tothicken. This might have prevented the reduction of root volume in high density profile. In1967, GEISLER reported morphological changes in root systems as a reaction of alterations inroot growing environment. Intensive studies carried out by PRIGGE (1983) showed that agrowth retardation in main root due to soil compaction was accompanied by a greatlyincreased root surface area in upper noncompacted soil zone due to a super compensatorydevelopment of root system in this part. At third and final harvest root volume of highdensity pots in lower layer (40—50 cm) was lower and in upper layer (0—20 cm) washigher than in corresponding root volumes of low and medium density pots. This isbecause a greater part of the roots was accumulated in the upper layer as they could notpenetrate deeper. Root dry matter also suffered due to high bulk density owing to effectsalready discussed. Similar effects on root dry matter have also been reported by PRIGGE

(1983). This adverse effect of compaction on root development proportionally reflected inabove ground plant parts (Fig. 1) might be due to decreased root absorption activities.

In an attempt to imitate natural soil profiles pots were filled with layers of differentdensities. The results have been presented in Figures 6 to 10. It can be seen that the negativeeffect of increased top and/or subsoil density on shoot and root growth was very clear afterfour weeks of plant age. Total root volume was not changed much but total root length wasgreatly influenced when both top and subsoil densities were increased rather than changingonly subsoil density. By increasing top-soil density the root dry matter was significantlydecreased in all layers, while changing subsoil density the reduction was only in middle andlower layers. Root volume in any layer was not much affected, may be due to similarreasons explained earlier. Total root length was substantially decreased in the lower layerdue to limited penetrating abiHty of roots in high density profile.

Zusammenfassung

Einflufi homogener und heterogener Bodendichteauf das Sprofi- und Wurzelwachstum von Acker- und Sojabohnen

Die vorhegende Arbeit beschaftigt sich mit den Ergebnissen von Versuchen, die zurFeststellung des Einflusses der Bodendichte auf das Acker- und Sojabohnenwachstum imGewachshaus durchgefiihrt wurden. Plastikrohren mit 58 cm Hohe und 12 cm Durchmes-ser wurden mit tonigem Lehmboden mit 3 homogenen Bodendichten — niedrig (1,25 g/cm-*), mittel (1,45 g/cm^) und hoch (1,65 g/cm^) — und 3 Kombinationen von Ober- undUnterbodendichten — niedrig/mittel (Niveau 1), niedrig/hoch (Niveau 2) und mittel/hoch(Niveau 3) — gefuUt.

Im allgemeinen war der Einfluf? der Bodendichte bei beiden Leguminosen eine Vermin-derung des SproiS- und Wurzelwachstums sowie des Ertrages; die Ursache hierfiir scheintam Eindringwiderstand fiir die Wurzeln zu liegen. Im homogen dichtgelagerten Bodenerniedrigte die hohe Bodendichte die Wurzeltrockenmasse um 6—32% und die Gesamt-wurzellange um 30—57%, wogegen das Gesamtwurzelvolumen infolge verdickter Wur-zeln nicht beeinfluCt wurde. Bei der Sprofitrockenmasse wurden ebenfalls Verringeningenvon 4—31 % festgestellt. Bei den heterogenen Bodendichten ergab lediglich die Erhohungder Unterbodendichte von mittel auf hoch (Niveau 2) eine Verminderung der Sprofi- undWurzeltrockenmasse (8—36% sowie 16—39%), aber keine Veranderung der Gesamtwur-zellange. Das Pflanzenwachstum wurde beeintrachtigt, wenn sowohl Ober- als auchUnterbodendichte erhoht wurde (Niveau 3). Die Gesamtwurzellange in der oberen(0—20 cm) und mittleren (20—40 cm) Bodendichte wurde jedoch kaum verandert.


Acknowledgement

It is wished to acknowledge the assistance of Miss ULRIKE NEUMANN.

References

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BALIGAR, V. C , V. E. NASH, M . L . HARE, and J. A. PRICE, 1975: Soybean root anatomy asinfluenced by soil bulk density. Agronomy J. 67, 842—844.

BERTRAND, A. R., and H. KOHNKE, 1957: Sub-soil conditions and their effects on oxygensupply and the growth of corn roots. Soil Sci. Soc. Amer. Proc. 21, 135—140.

CAMP, C . R . , and J. F. LUND, 1968: Effect of mechanical impedance on cotton root growthTrans. ASAE 11, 188—190.

DREW, M . C , and M. J. Coss, 1973: Effect of soil physical factors on root growth. Chemistryand Industry, No. 14, 679—684.

FLOCKER, W . J., J. A. VOMOCIL, and F. D. HOWARD, 1959: Some growth responses of tomatoesto soil compaction. Soil Sci. Soc. Amer. Proc. 23, 181—191.

GEISLER, G. , 1967: Bodenluft und Wurzelwachstum unter besonderer Beriicksichtigung derWurzel. Arb. Landw. Hochschule Hohenheim 40. Verlag Eugen Ulmer, Stuttgart.

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KEMPER, W . D . , B . A . STEWART, and L. K. PORTER, 1971: Effects of compaction on soil nutrientstatus. In: BARNES et al., eds. Compaction of Agricultural Soils. ASAE Monograph,pp. 78—190.

PHILLIPS, R. E. , and D. KIRKHAM, 1962: Soil compaction in the field and corn growth.Agronomy J. 54, 29—34.

PRIGGE, G. , 1983: Wachstum von Mais und Gerste in Boden mit homogenem und heterogenemGefuge sowie bei variierter Stickstoffdiingung (Gefafiversuche) unter besondererBeriicksichtigung des Adaptionsvermogens des Wurzelsystems. Ph. D. Thesis, Univer-sitat Kiel.

PRIHAR, S. S., M . M . CHOWDHARY, and I. M. VARGHESE, 1971: Effect of post-planting looseningof unstable soil on the anatomy of corn root. Plant and Soil 35, 57—63.

SCOTT, T . W . , and A. E. ERICKSON, 1964: Effect of aeration and mechanical impedance on theroot development of alfalfa, sugar beets and tomatoes. Agronomy J. 56, 575—576.

SiLBERBUSH, M., W. B. HALLMARK, and S. A. BARBER, 1983: Simulation effects of soil bulkdensity and P addition on K uptake by soybeans. Commun. Soil Sci. and Plant analysis14, 287—296.

VEIHMEYER, F . J . , and A. H. HENDRICKSON, 1948: Soil density and root penetration. Soil Sci.65, 487—493.

WARKENTIN, B . P., 1971: Effects of compaction on content and transmission of water in soils.In: BARJMESet al., eds.. Compaction of Agrl. Soils. ASAE Monograph, pp. 126—154.

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effect of homogeneous and heterogeneous soil compaction on shoot and root growth of field bean and...

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