Long-term effects of management systems on crop yield and soil physical properties of semi-arid tropics of Vertisols

doi:10.4236/as.2011.24056

Paper Menu >>

Journal Menu >>

Vol.2, No.4, 435-442 (2011)

doi:10.4236/as.2011.24056

Agricultural Scienc es

Long-term effect s of management systems on crop yield

and soil physical properties of semi-arid tropics of

Vertisols

Prabhakar Pathak*, Suhas P. Wani, Raghavendra Rao Sudi

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Andhra Pradesh, India;

*Corresponding Author: p.pathak@cgiar.org

Received 8 September 2011; revised 17 October 2011; accepted 26 October 2011.

ABSTRACT

Long-term experiments can be used to assess

management induced changes in soil properties

and sustainability of the management system in

terms of the productivity. Such data are scanty,

especially in the semi-arid tropics (SAT) region.

A long-term experiment established in 1976 at

ICRISAT in India on Vertisols with two manage-

ment treatments; improved management (IM),

comprising semi-permanent broadbed and fur-

row (BBF) landform with minimum tillage and

improved cropping practices; and traditional

management (TM) system comprising keeping

the land fallow during the rainy season and

sowing on flat landform during post-rainy sea-

son with traditional cropping practices, was

sampled after 24 and 34 years for soil physical

and hydrological properties. Results showed

that both in short- and long-term the manage-

ment systems had profound effect on crop

yields. Also in the long-term IM and TM man-

agement systems had significant effect on sev-

eral soil physical and hydrological properties.

Throughout the soil profile IM systems had sig-

nificantly low er bulk density, significantly higher

porosity, substantially lower penetration resis-

t ance both at 5 cm (1 and 8 MPa) and 15 cm depths

(8 and 15 MPa), significantly higher infiltration

and sorptivity and significantly larger mean

weight diameter of 4.3 mm compared to 2.8 mm

for soils under TM. However, management sys-

tems had no significant effect on moisture hold-

ing capacities both at 0.033 and 1.5 MPa. Sig-

nificant differences between the improved and

traditional systems were observed in the size and

pattern of soil surface cracks. Over the long-

term, the improved management systems has

very favorable effects on soil physical and hy-

drological properties and on the soil surface

cracking and its patterns, thereby contributing

to higher productivity.

Keywords: Broadbed and Furrow System;

Minimum Tillage; Long-Term Experime nt;

Sustainability

1. INTRODUCTION

Vertisols are one of the major soil orders found in the

semi-arid tropics (SAT). Due to unreliable and variable

rainfall, proneness to water logging, difficulty in tillage

operations due to sticky nature of wet soils and risk

aversion of farmers in many rainfall zones in Indian SAT,

Vertisols are kept fallow in the rainy season [1].

Crops are grown only in post-rainy season on the stored

moisture in the soil profile. The implications of the rainy

season fallow system are serious both in terms of the

overall productivity and with regard to the frequent oc-

currence of large quantities of runoff and soil loss [2].

The lack of vegetative cover during most of the rainy

season exposes the surface soil to the impact of high

intensity storms, causing severe soil erosion [3]. The

traditional crop production system often results in low

crop yields, high runoff and soil loss, reduced ground-

water recharge and frequent flooding of the downstream

lands [4].

To develop an improved crop production system that

enables crops to be grown in both the rainy and the post-

rainy seasons, and improves agricultural productivity

and rainwater use efficiency on a sustainable basis, a

long-term experiment was initiated on the Vertisols at

ICRISAT research station, Patancheru in 1976. It was

envisaged that substantial gains in total food production

can be attained if the present post-rainy season cropping

can be replaced by systems that permits growing of two

crops in the rainy and post-rainy seasons. However to

enable cropping during the rainy season, an appropriate

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

436

tillage and land and water management system that re-

duces the problem of water logging and allow timely till-

age operations was essential. The semi-permanent broad-

bed and furrow system with minimum tillage (BBF/MT)

was found appropriate for the in-situ soil and water con-

servation and reducing water logging problem in these

Vertisols [5]. Long-term experiments with BBF/MT along

with other improved cropping practices, have clearly

demonstrated that advantages and profitability of this

improved system [6,7]. There was also clear evidence of

increased soil organic C, total N and P, available N, P

and K, and microbial biomass C and N in the soil under

improved management system [8].

The objective of this study was to assess the long-term

effects of the improved management system (BBF/MT

with improved cropping practices) and traditional man-

agement system (flat cultivation with traditional tillage

and cropping practices) system on crop yields, physical

and hydrological properties of the Vertisols. The effects

of management systems on soil surface cracking and its

pattern in the Vertisols were also studied. The implica-

tions of these changes in physical and hydrological

properties and cracking pattern for tillage, soil and water

management and crop productivity are discussed.

2. MATERIALS AND METHODS

2.1. Experimental Site

The experiments were conducted in two adjacent

small Vertisol watersheds [3.5 ha Black soil Watershed 1

(BW1) and 3.2 ha Black soil Watershed 4C (BW4C)] to

evaluate the long-term effect of tillage and crop manage-

ment systems on crop productivity and soil quality at IC-

RISAT Center, near Hyderabad, Patancheru, India (17˚36'N,

78˚16'E, 545 m altitude) (Figure 1). Two management

systems (improved and traditional) were studied under

long-term experiments initiated in 1976. The average slope

of the experimental watersheds is about 2.0%.

The mean annual rainfall at the experimental area is

about 800 mm; the average minimum temperature is

17˚C and maximum temperature is 32˚C. Rainfall is

variable temporally and during the experimental period

(1976-2009) annual rainfall ranged from 518 to 1194

mm. Spells of excess moisture and drought during the

crop-growing period are common. About 80% of annual

rainfall occurs between June and September and is

known as the monsoon or kharif, in which rainfed crops

are grown. The post-rainy winter season from October to

January, also known as rabi, is dry and cool and days are

short.

2.2. Soils

The soils at the experimental site belong to the very

fine, clayey, montmorillonitic, calcareous hyper thermic

family of typic pallusterts and are classified as “Verti-

sols” Kasireddipalli series [4]. These Vertisols are high

in montmorillinitic clay (40% to 64%) and undergo

pronounced shrinkage during drying, resulting in large

cracks that close only after prolonged rewetting. These

soils become hard when dry and sticky when wet. Thus,

tillage operations must coincide with the specific range

of soil water contents at which the soil is trafficable.

Drainage during wet periods in the rainy season can be a

serious problem.

Figure 1. Experimental watersheds (BW1 and BW4C) at the ICRISAT research station, Patancheru, India.

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

437437

2.3. Treatment Details

The details of two management systems are given be-

low:

2.3.1. Improved Management System

(BW1 Waters hed)

This system includes a semi-permanent broadbed and

furrow system with minimum tillage (BBF/MT) only in

the beds along with improved cropping practices [4].

The beds are 1.0 m wide with 0.5 m furrows prepared at

0.6% gradient using a bullock drawn bed-maker mounted

on a tropicultor. Field traffic was confined to the furrows.

Excess rainfall drains along the furrows and is discharges

into grassed waterways [9]. Improved agronomic prac-

tices, viz. use of high-yielding varieties, dry sowing

ahead of the rainy season, nutrient management, inte-

grated pest management and other improved practices,

were followed [8]. In view of the difficult workability of

Vertisols both in the very dry and very wet conditions,

primary tillage was done immediately after the harvest

of post-rainy season crop. Final land preparation was

initiated immediately following initial rains so that the

system is again ready for pre-monsoon sowing of the

next year’s crop.

2.3.2. Traditional Management System

(BW4C Watershed)

In this system the land was left as cultivated bare fal-

low during the rainy season and sorghum and chickpea

were grown as sole crop in the post-rainy season [10].

Sowing was done with a local seed drill on a flat surface

when seedbed moisture was adequate. No chemical fer-

tilizers were applied to the crop, but 10 t·ha–1 of farm-

yard manure (FYM) was broadcasted each alternate year

before land preparation (farmers practice). The land was

ploughed every two years; harrowing was done with a

blade harrow to control weeds.

2.4. Soil and Crop Sampling

After 24 (April 1999) and 34 years (April 2009) of

experimental cycles, both watersheds (BW1 and BW4C)

were sampled for detailed physical and hydrological

properties of two profile pits were dug in each watershed

and three replicated samples were collected for texture,

bulk density, and porosity measurements from each pit

up to 1.2 m depth at increments of 15 cm [11]. The soil

samples from both the watersheds at 2 layers (0 - 15 and

15 - 30 cm) were collected for aggregate analysis by wet

sieving method for mean weight diameter of soil aggre-

gates. Infiltration measurements were done at four loca-

tions each at surface on bed and furrow of BW1 and four

locations in BW4C watershed [12]. Penetration resis-

tance readings were made in both the improved (80 ob-

servations) and traditional (20 observations) treatments

depending up on the variations in each of the watersheds.

The samples from BW1 were collected from the centre

of beds and in furrows. Table 1 gives the details of

number of samples collected for various physical prop-

erties of soil.

For estimating the crop yields, samples from 24 ran-

domly selected spots (each 12 m2 area) were collected

from the each treatment. After taking the fresh weight of

grain and biomass, the samples were kept in drier for

obtaining dry weights.

2.5. Statistical Analysis

Soil physical and hydrological data obtained from

watersheds BW1 and BW4C were analyzed using the

analysis of variance method in GENSTAT 5 with man-

agement systems as main treatments and soil depths as

sub-treatments. The significant differences between main

and sub-treatments and interaction effects were studied

by comparing the “F” test of significance and standard

error of means.

Table 1. Details of samples collected for soil physical properties determination.

Number of samples

BW1

Soil property

Bed Furrow

BW4C

Method/equipment

Texture 6 6 6 Hydrometer method

Bulk density 6 6 6 Core method

Total porosity 6 6 6 From density measurements

Air-filled porosity 6 6 6 From density measurements

Penetration resistance 80 80 20 Cone penetrometer

Mean weight diameter Wet-sieving method

Sorptivity 4 4 4 Disc permeameter

Steady-state flow rate 4 4 4 Disc permeameter

Cumulative infiltration 4 4 4 Disc permeameter

Moisture retention 6 6 6 Pressure plate apparatus

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

438

3. RESULTS AND DIS CUSSION

3.1. Crop Productivity

The crop yields were higher in the improved system

(semi-permanent broadbed and furrow with minimum

tillage along with improved cropping systems and man-

agement) than in the traditional system (monsoon fallow

with flat landform with traditional cropping practices).

In the improved system the sorghum and pigeonpea to-

gether recorded an average grain yield of 5.3 t·ha–1·yr–1

compared with the 1.2 t·ha–1·yr–1 in traditional system

(Figure 2). The annual gain in grain yield in the im-

proved system was 82 kg·ha–1·yr–1 compared with 23

kg·ha–1·yr–1 in the traditional system. The initial big dif-

ference in crop yields between the two systems was

mainly due to two crops per year in improved system vs

one crop per year in traditional system. Also the im-

proved system had improved varieties and cropping sys-

tem along with other improved management compared

to traditional variety and traditional management prac-

tices in traditional system. Significant contribution had

also come from the improved BBF landform and tillage

system, which facilitated the cropping during the rainy

season by improving surface drainage and reducing wa-

ter logging problem. The improved system of BBF

landform reduced seasonal runoff from 174 mm meas-

ured within the traditional system to 99 mm, improving

soil water content and reducing annual soil losses from

6.46 t·ha–1 to 1.51 t·ha–1 [3]. However, subsequent an-

nual gain in grain yield must have come from the grad-

ual improved soil health. The small annual gain in crop

yield observed in the traditional system can be attributed

to the organic fertilizers (FYM) incorporated into the

system. However, the large annual gain in the crop yield

in the improved system could be attributed to gradual

im- provement in soil health (soil physical, chemical and

biological properties). The improved system [8] reported

the positive changes in the soil chemical and biological

properties from the same experiment. The changes in the

soil physical and hydrological properties are discussed in

the subsequent sections of this paper.

3.2. Soil Physical Properties

3.2.1. Mean Weight Diam eter

Management system had a significant effect on the

mean weight diameter of water stable aggregates (Table

2). After 34 years of experimentation, the soils in im-

proved management had significantly larger mean weight

diameter compared to soils under traditional management.

This trend was seen both at 0 - 15 and 15 - 30 cm soil

layers. This may be attributed to relatively more crop

residue, minimum tillage in the cropping zone and

higher microbial activity in the improved system.

3.2.2. Penetration Resistance

The soils under improved management had lower

penetration resistance at 5 and 15 cm depths compared

to soils under traditional management (Figure 3). For

example, at 5 cm depth the penetration resistance of soils

in the improved system was 1.1 compared to 9.8 MPa in

the traditional system. This suggests a progressive im-

provement in soil tilth occurred in the cropping zone

(bed zone) over time. So in the BBF system the tillage

operations in the bed zone (cropping zone) became pro-

gressively easier, allowing timely tillage operations

which is so crucial for SAT Vertisols in view of their

difficult workability in the dry and wet conditions. There-

fore in the long-term, the semi-permanent BBF system

facilitates land preparation during the summer season

and dry sowing of the rainy season crop, which are pre-

requisites for the double cropping in such SAT environ-

ments.

3.2.3. Soil Texture

A significant difference in texture between improved

and traditional management systems was observed only

in top 10 cm soil layer (Table 3). After 24 and 34 years

of experimentation the improved system had signify-

cantly higher clay content (51% and 50%) compared to

Figure 2. Three-year moving average of sorghum and pigeon-

pea grain yield under improved (BW1) and traditional (BW4C)

management systems in deep Vertisol catchment at ICRISAT,

Patancheru, India.

Table 2. Long-term effects of management systems on mean weight diameter (mm) of water stable aggregates.

Improved system Traditional system

Depth

(cm) 1976 2009

SEM 1976 2009 SEM

0 - 15 3.0 4.1 0.251 2.9 2.7 0.069

15 - 30 3.1 4.5 0.158 3.0 2.8 0.161

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

439439

Table 3. Long-term effects of management systems on soil texture (0 - 10 cm).

Improved system Traditional system

Texture 1976 1999 2009 SEM 1976 1999 2009 SEM

Clay (%)** 52 51 50 0.675 52 46 45

0.985

Silt (%) 22 21 21 0.792 22 22 21

0.896

Fine sand (%) 15 15 16 0.981 14 15 16

1.089

Coarse sand (%)** 12 13 13 0.725 12 17 18

0.741

Gravel (%)** 4 5 5

0.133 4 11 13

2.102

traditional management (46% and 45%). There was no

significant difference in silt and fine sand contents. The

coarse materials (coarse sand and gravel) were signifi-

cantly higher in traditional management. The texture

analyses indicates the long-term effect of the differential

soil erosion between the improved and traditional man-

agement systems, with higher soil erosion in the tradi-

tional systems (6.5 t·ha–1·yr–1) compared with the im-

proved system (1.5 t·ha–1·yr–1) resulting in greater re-

moval of finer soil particles from the cultivated topsoil

layer [3].

3.2.4. Bulk Density

At beginning of the experiment, the soil bulk density

of different layers in two experimental watersheds was

similar (Figure 4). After 24 and 34 years of experiments,

the bulk density throughout the soil profile (up to 105 cm)

was significantly lower with improved management than

in traditional management. However, the differences in

bulk densities were relatively greater in the top 20 cm

soil layer and the maximum difference in bulk density

between the two treatments was recorded in the top 0 -

10 cm soil layer. These data clearly show the advantage

of improved management system over the traditional

management system in keeping the soil loose which has

major implications for tillage (time, and energy require-

ment), water movement, aeration and root growth. It

appears that the large changes in bulk density in the top

0 - 20 cm soil layer have occurred mainly because of the

different tillage systems, which had been followed in the

improved and traditional systems.

3.2.5. Porosity and Air-Filled Porosity

The long-term effect of improved and traditional

management on total porosity and air-filled porosity are

shown in (Figure 5). Both air-filled porosity and total

porosity recorded from the improved system were sig-

nificantly higher compared to values recorded from tra-

ditional system. In the improved system the air-filled

porosity in top 30 cm soil layer had improved by 46%

during the first 24 years of experiments (1976-1999). In

the traditional management system no significant changes

in porosity and air-filled porosity was recorded even

after 24 and 34 years of experimentations. These data

indicate the effectiveness of the improved management

system in improving soil porosity and air-filled porosity,

thereby improving the internal profile drainage in the

seed and root environment of Vertisols. This has major

implications for Vertisols where during rainy season the

waterlogging is often a serious problem mainly due to

very low saturated hydraulic conductivity and poor in-

ternal profile drainage needed.

Figure 3. Long-term effects of improved vs. traditional man-

agement systems on soil penetration resistance.

Figure 4. Long-term effects of improved vs. traditional man-

agement systems on bulk density of soils.

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

440

3.3. Hydrological Properties

(Moisture Retention, Infiltration

and Sorptivity)

Even after the 24 and 34 years of experimentations, no

significant difference in soil moisture retention properties

both at 0.033 and 1.5 MPa were recorded in the soil

samples from improved and traditional management sys-

tems (Table 4).

After 24 years of experimentations, significantly

higher initial infiltration rate (347 mm·h–1) was recorded

in improved management system compared to traditional

management system (265 mm·h–1). Similar trend in in-

filtration rate was recorded after 34 years of experiments.

The sorptivity value was also significantly higher in im-

proved management system (121 mm·h–1/2) than in tradi-

tional management system (88 mm·h–1/2). These values

indicate the long-term effects of improved and tradi-

tional tillage and crop management systems on hydro-

logical properties of soils. These changes in soil proper-

ties may have contributed in reduced runoff recorded

from the improved management system. On an average

(from 1974 to 1993) the improved tillage and crop man-

agement system reduced annual runoff from 220 mm

measured from the traditional tillage and crop manage-

ment system only to 91 mm [13].

Figure 5. Long-term effects of improved vs. traditional management systems on total and air-filled porosity of soils.

Table 4. Change in the hydrological properties of soils in improved and traditional management system.

Improved management system Traditional management system

Soil properties

1976 1999 2009 1976 1999 2009

Moisture retention (g·g−1) of

0 - 10 cm depth at 0.033 MPa 1.5 MPa

0.33

0.20

0.35

0.22

0.36

0.22

0.33

0.21

0.33

0.20

0.32

0.20

Cum. Infiltration in first 1 h (mm)** 289 347 356 292 265 273

Sorptivity (mm·h−1/2)* - 121 - - 88 -

*Significant at 0.05 and **highly significant at <0.001 probabilities; -not measured

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

441441

Figure 6. Long-term effects of improved vs. traditional management systems on cracking pattern.

3.4. Surface Cracks and Its Pattern

The development of cracks owing to shrinkage is a

major structural feature of Vertisols. Big cracks, ex-

tending deep into the profile, define major structural

features and play an important role in several soil and

water processes [14].

Significant differences between the two treatments

were observed in the pattern, area and density of cracks.

The total length of cracks (1.17 vs 2.1 m per m2 of land

area) and its area (0.07 vs 0.16 m2 per m2 of land area)

was found significantly lower in the improved mana-

gement system compared traditional management sys-

tem (Figure 6). In watershed with improved manage-

ment (semi-permanent BBF land treatment) most of the

cracks were found in the furrows, which serve as traffic

zone. The presence of cracks in bed or cropping zone

were relatively fewer. Soil compaction due to farm ma-

chinery wheel traffic and human trampling induced

deeper and wider surface cracks in the furrows, which

got developed with further drying into big cracks. Since

compaction was restricted to particular traffic zone, most

large cracks were located in the furrows only. Within the

traditional management system (flat land treatment)

cracks were found all over including in the cropping

zone (Figure 6).

Cracking patterns could affect germination, seedling

establishment, vegetative growth, root development and

crop yields [6,15]. Although the wider and deeper cracks

were found in furrows of semi-permanent BBF in im-

proved management compared to flat land configuration

in traditional management, it may not affect the crop

growth on BBF as the cracks were at a distance from the

crop zone. Where as, in traditional management the crop

growth was affected due to formation of cracks in the

crop zone, which were at a closer distance to the crops

resulting in an uneven moisture distribution and rela-

tively lower available soil moisture in the root zone.

In the improved system however the presence of large

cracks in the furrows could greatly increase the initial

infiltration by intercepting the runoff particularly during

the early parts of the rainy season. The runoff recorded

during the early parts of the rainy season supports this

hypothesis [3]. During high rainfall years the Vertisols

have severe waterlogging problem mainly due to poor

profile internal drainage. Wider and deeper cracks cre-

ated by compacted zone in improved system could pro-

long the useful life of cracks as large drainage voids for

the soil in the neighboring zone. This mechanism may

significantly help in reducing the waterlogging problem

in the improved management system.

4. CONCLUSIONS

The results indicate that in the long-term, the improved

management system (BBF landform along with mini-

mum tillage and appropriate crop management practices)

substantially increased the crop yields as well as im-

proved the physical and hydrological properties of SAT

Vertisols. The results also indicate that with this im-

proved management system it is possible to achieve the

substantially higher crop productivity along with im-

proved soil quality. In the long-term the improved man-

agement system resulted in lower bulk density and pene-

tration resistance and higher porosity compared with

traditional management system (flat cultivation, mon-

soon fallow with traditional practices). Similarly, soil

hydrological properties (infiltration and sorptivity) were

more favorable in improved management system than

traditional management system. The improved manage-

ment system resulted in larger mean weight diameter of

soil particles and better soil aggregation and more fa-

vorable soil surface cracking and its pattern.

The favorable soil physical and hydrological proper-

ties recorded under the improved management system

have positive implications for the cultivation and timely

P. Pathak et al. / Agricultural Sciences 2 (2011) 435-442

442

tillage operations on SAT Vertisols under both dry and

wet soil conditions. The timely tillage is one of the ma-

jor constraints for improved management of Vertisols

particularly during the rainy season. The implications of

traditional with no crops during rainy season (or mon-

soon fallow) are serious both in terms of the overall crop

productivity and with regard to soil degradation through

high runoff and soil loss.

Significantly higher porosity and air-filled porosity

recorded under the improved management system indi-

cate the effectiveness of this system in improving the

waterlogging problem in SAT Vertisols. The favorable

changes in soil physical, hydrological properties and

cracking pattern under improved management system

must have contributed in increasing and sustaining the

crop productivity, which recorded about 5 times higher

compared to traditional management system.

5. ACKNOWLEDGEMENTS

This paper is based on the long-term experiments at Heritage water-

sheds ICRISAT Center, Patancheru, India, financial support provided

by S. M. Sehgal Foundation for Heritage watersheds is gratefully ac-

knowledged. We acknowledge the help and contribution of all the

scientists and staff who have been associated with these experiments.

The authors are highly thankful to Dr. Peter Craufurd for his comments

and suggestions in improving the manuscript.

REFERENCES

[1] Michaels, G.H. (1982) The determinants of kharif fal-

lowing on the Vertisol in semi-arid tropical India. Ph.D.

Thesis, University of Minnesota, Minneapolis.

[2] Pathak, P., Singh, S. and Sudi, R. (1986) Soil and water

management alternatives for increased productivity on

SAT Alfisols. Proceedings of the IV International Con-

ference on Soil Conservation, Maracay, 3-9 November

1986, 533-550.

[3] Pathak, P., Sudi, R. and Wani, S.P. (2011) Hydrological

behaviour of Alfisols and Vertisols in the semi-arid zone:

Implications for soil and water management. Agricultural

Water Management Journal (submitted).

[4] El-Swaify, S.A., Pathak, P., Rego, T.J. and Singh, S.

(1985) Soil management for optimized productivity un-

der rainfed conditions in the semi-arid tropics. Advances

in Soil Science, 1, 1-64.

doi:10.1007/978-1-4612-5046-3_1

[5] Pathak, P., Mishra, P.K., Rao, K.V., Wani, S.P. and Sudi,

R. (2009) Best options on soil and water conservation. In:

Wani, S.P., Venkateswarlu, B. Sahrawat, K.L., Rao, K.V.

and Ramakrishna, Y.S., Eds., Best Bet Options for Inte-

grated Watershed Management, Proceedings of the Com-

prehensive Assessment of Watershed Programs in India,

ICRISAT, Pantancheru 502 324, Andhra Pradesh, 75-94.

[6] Srivastava, K.L., Smith, G.D. and Jangawad, L.S. (1990)

Zonal surface management for rainfed Vertisols. In:

Challenges in Dryland Agriculture—A Global Perspec-

tive. Proceedings of the International Conference on

Dryland Farming, Amarillo/Bushland, 15-19 August

1988, 584-585.

[7] Virmani, S.M., Pathak, P. and Singh, R. (1991) Soil re-

lated constraints in dry land crop production in Vertisols,

Alfisols and Entisols of India. Bulletin of Indian Society

of Soil Science, 15, 80-95.

[8] Wani, S.P., Pathak, P., Jangawad, L.S., Eshwaran, H. and

Singh, P. (2003) Improved management of Vertisols in

the semi-arid tropics for increased productivity and soil

carbon sequestration. Soil Use and Management, 19,

217-222. doi:10.1111/j.1475-2743.2003.tb00307.x

[9] Kampen, J. (1982) An approach to improved productivity

on deep Vertisols. ICRISAT, Andhra Pradesh, ICRISAT

Information Bulletin, 11 .

[10] Laryea, K.B., Pathak, P. and Klaij, M.C. (1991) Tillage

systems and soils in the semi-arid tropics. Soil and Till-

age Research, 20, 201-218.

doi:10.1016/0167-1987(91)90040-5

[11] Klute, A. (1986) Methods of soil analysis. Part 1: Physi-

cal and mineralogical methods. 2nd Edition, American

Society of Agronomy and Soil Science Society of America,

Madison, USA.

[12] White, I. and Sully, M.J. (1987) CSIRO disc-permeameter:

Instruction manual. CSIRO Division of Environmental

Mechanics, Canberra.

[13] Pathak, P. and Laryea, K.B. (1995) Soil and water con-

servation in the Indian SAT: Principles and improved

practices. In: Singh, R.P., Ed., Sustainable Development

of Dryland Agriculture in India, Scientific Publishers,

Jodhpur, 83-94.

[14] Bouma, J. (1984) Using soil morphology to develop

measurement methods and simulation technique for wa-

ter movement in heavy clay soils. In: Bouma, J. and

Raats, P.A.C., Eds., Proceedings of ISSS Symposium on

Water and Solute Movement in Heavy Clay Soils, ILRI,

Wageningen, 27-31 August 1984, 298-310.

[15] Younger, D.R. and Gilmore, J.M. (1978) Studies with

pasture grasses on the black cracking clays of the Central

Highlands. I. Species evaluation. Tropical Grassland, 12,

152-162.