Mrabet 2011

1015P. Tow et al. (eds.), Rainfed Farming Systems, DOI 10.1007/978-1-4020-9132-2_40, © Springer Science+Business Media B.V. 2011

Abstract Agriculture in West Asia and North Africa (WANA) is losing momentum. Serious problems of land degradation, desertification, declining soil quality, reduced soil fertility and low agricultural production levels may be irreversible if appropriate measures are not taken soon. Past research in agriculture focused on testing cropping systems under conventional soil management which may no longer be relevant to the WANA region. Most of WANA’s soils need skilled management practices such as no-tillage and stubble retention to ensure sustainable agricultural production. This chapter reviews research on no-till (NT) and conservation agriculture (CA) and their application in rainfed regions of WANA. In WANA countries where water scarcity is becoming endemic, NT could rehabilitate productivity of soils and farmers’ returns, although it can result in lower yields where weeds are not controlled. Institutions need to disseminate the principles and practices of no-till in order to improve productivity and profitability and benefit both the environment and society.

Keywords No-tillage systems • Conservation agriculture • Carbon sequestration • Sustainability • Economical development • WANA

40.1 Introduction

There are great challenges to agriculture and the natural resources of West Asia and North Africa (WANA) because agricultural development is needed to satisfy future food consumption requirements, to encourage job creation and to reduce poverty. Agriculture in the region is dominated by rainfed cereal cultivation in conjunction with livestock production. It employs nearly 50% of the population in, for example, Turkey and Morocco.

R. Mrabet (*) Institut National de la Recherche Agronomique (INRA), Regional Agricultural Research Center of Tangier, 78, Boulevard Sidi Mohamed Ben Abdellah, Tangier 90010, Morocco e-mail: [email protected]

Chapter 40No-Tillage Agriculture in West Asia and North Africa

Rachid Mrabet

1016 R. Mrabet

Over the past centuries, the increasing population has led to intensification of agriculture, over-tillage and over-stocking, and accelerated human-induced soil degradation (Lal 2002). Despite the priority given to rainfed cereal research by national and international institutions, only limited advances have been made in productivity; crop yields are generally low at 0.6–1.5 t/ha (Heng et al. 2007).

The WANA region encompasses a wide variety of cropping rotation systems where water is a major limitation to productivity. Even though several of the crops grown originated in the region, it is chronically food-deficient. Recently, more effort by international organisations and development institutions is encouraging adoption of no-tillage (no-till) practices in particular and conservation agriculture in general. This chapter reviews information on no-till (NT) systems in WANA region, mostly from Iran, Morocco, Syria, Sudan, Tunisia and Turkey.

The main concerns of this chapter are the reversal of degradation in soils along with increased productivity and economic returns, and removal of current con-straints on use of no-till systems within the farmers’ communities.

40.2 Agriculture in WANA Region

The region has a land area of 1.7 billion hectares with a population of 600 million—about 14% of the total area of the world and 10% of the world’s population. Desert or semi-desert covers 70% of the total area, with 22% as grazing lands. It is char-acterised by high population growth, low and erratic rainfall, limited arable land, and severely limited water resources.

Most of the region is semi-arid, with pronounced rainfall variability. The total agricultural land area is 147 million hectares, about 76% of which is rainfed. There are few possibilities for expansion of irrigated agriculture (Ryan et al. 2006), which occurs mainly in the Nile valley in Egypt and Sudan and the Tigris–Euphrates in Iraq and Syria.

Arable land represents about 8% of the total land resources, and is very limited in relation to the population, with an average of 0.25 ha of arable land per capita. Over time, all countries, except Sudan and Turkey, will face high population pres-sure on their arable lands. Permanent pastures and rangelands, which cover around 30% of the total area and provide around one-third of the diet of livestock, have been severely degraded by unrestricted grazing and desertification. The region is characterised by low-productivity ecosystems with soils of low physical, chemical and biological quality.

The average annual rainfall can be higher than 500 mm, but most of the cropping areas receive 200–500 mm and this varies widely from year to year and within seasons. Climate change is predicted to reduce rainfall by 20–25% by 2050, while temperatures rise by 2–2.75°C (Ragab and Prudhomme 2002). This may exacerbate existing water scarcity.

101740 No-Tillage Agriculture in West Asia and North Africa

The production systems are dominated by cereals, primarily wheat1 in the wetter areas and barley in the drier areas, in rotation mainly with food legumes such as chickpea and lentil, as well as some corn, sunflower and forage legumes. The most common systems are continuous, annual mono-cropping of cereals (a consequence of population pressure) and wheat–fallow (either clean or weedy) for water conser-vation. In fact, where annual precipitation is less than 450 mm, farmers using con-ventional tillage have regarded fallowing as necessary to produce sustainable wheat grain yields. However, weeds must be controlled during the fallow to store adequate soil moisture (Bouzza 1990; Pala et al. 2008).

40.3 No-Till Systems

No-till methods are a part of conservation tillage and conservation agriculture (CA).2 Conservation tillage is any tillage or planting system in which at least 30% of the soil surface is covered by plant residue after planting. This reduces erosion by water or wind. CA embraces crop production systems where there is minimal soil disturbance and retention of residues on the soil surface, in contrast to conventional tillage (CT) operations that invert the soil and bury residues. This reverses the traditional system that emphasises the need for a clean seedbed without crop residues on the surface.

Conservation agriculture was introduced by the Food and Agriculture Organization of the United Nations (FAO) as a concept combining resource-efficient crop production based on integrated management of soil, water and biological resources, with external inputs.

The no-till (NT) system consists of a one-pass planting and fertiliser operation in which the soil and the surface residues are minimally disturbed. Weed control is generally achieved with herbicides or, in some cases, with crop rotation. NT sys-tems have been adopted in countries world-wide, on more than 100 million hectares (see Chap. 39). They are based on four principles: (1) buffering of the soil sur-face, with mulch/crop residues, against direct impacts of atmospheric elements (rain, wind, solar radiation) and of traffic; (2) minimum disturbance of soil structure, while achieving high soil quality and optimum placement of seed and fertiliser; (3) varied crop sequences for productive and healthy crops; and (4) environmentally-benign weed control based on herbicide use and crop rotations. However, in practice farmers may not adopt all components because of limited access to inputs such as herbicides or use of crop residues for other purposes (Mrabet 2001a).

So far, few of the WANA countries have invested significantly in CA research and development. Evidence from overseas no-till research (mainly from USA) helped establish nodes of research and development in Morocco in the early 1980s (Mrabet 2008), Syria in mid-1980s (Ryan et al. 2008) and more recently in Tunisia (M’hedhbi et al. 2003). At present, no-till is applied to approximately 10,000 ha in

1 See glossary for botanical names of crops.2 See glossary.

1018 R. Mrabet

Sudan (Rasheed et al. 2006), 9,000 ha in Tunisia (M. Ben Hammouda 2008) and more than 2,000 ha in Morocco.

No-till research and development are still fragmentary and embryonic, but the results from studies so far generate optimism and the desire to promote the no-till systems through international cooperation and national efforts (Mrabet 2008).

Large on-farm participatory projects in the region operate as follows:

The Arab Authority for Agricultural Investment and Development (AAAID), • with the support of governments in several Arab countries (Morocco, Yemen, Tunisia, Jordan, Syria and Sudan), has been active in the demonstration and extension of no-till and reduced tillage practices since 2000 (AAAID 2007).The French Agency for Development (AFD), with scientific support from • CIRAD (Centre International de la Recherche Agronomique pour le Développement), started experimenting and promoting direct sowing, mulch-based cropping systems in Tunisia in 1999 (AFD 2006). Similar projects are underway in Algeria and Morocco.

40.4 Effect of No-Till Methods on Crop Production and Cropping Systems

40.4.1 Grain Yields of Cereal Crops

Most available results comparing cereal yields over a number of years under NT and conventional tillage systems in WANA are summarised in Table 40.1 and Fig. 40.1. No-till systems permit early seeding which has a major influence on growth, development and water use efficiency (Oweis et al. 2000) during the Mediterranean growing season, particularly in semi-arid environments (Mrabet 1997). Under NT, planting is no longer determined by the adequacy of rainfall for tillage and seedbed preparation or by excess rainfall restricting access to the field, although it is still dependent on adequate weed control.

Short-term (equal to or less than 4 years) and medium-term (5–8 years) effects of NT systems on wheat yield have been variable but short-term benefits are impor-tant because they determine the attractiveness of NT to farmers and decision makers. The variability in short-term crop responses to NT is principally the result of the interacting effects of crop nutrient requirements, seed drill performances, weed control, soil characteristics and climate. Where moisture is limiting, crop yields under NT may improve in the short term—Vadon et al. (2006) in Tunisia; Mrabet (2002) in Morocco and Hemmat and Eskandari (2004a, b, 2006) in Iran—but may be depressed by weed infestation in wet conditions if herbicides are not applied appropriately—Yalcin (1998) in Turkey.

Mrabet (2008) concluded that:

No-till is a sustainable alternative to traditional and conventional tillage systems.• Chemical fallow which leaves crop residues (straw) on the soil surface could • substitute for clean tilled and weedy fallows.


Table 40.1 Wheat yields (t/ha) under no-till and conventional tillage in the WANA region

Country Species Rotation No-tillConvent. tillagea Yearsb References

Iran Bread wheat

Wheat–fallow 1.70 1.40 3 Hemmat and Eskandari (2004a)

Continuous wheat 1.43 1.01 3 Hemmat and Eskandari (2006)

Wheat–chickpea 1.60 1.24 3 Hemmat and Eskandari (2004b)

Morocco Bread wheat

Continuous wheat 2.47 2.36 4 Mrabet (2000a)Wheat–fallow 3.70 2.60 10 Bouzza (1990)

Mrabet (2000b)Continuous wheat 1.90 1.40 10Wheat–fallow 3.10 2.40 19 Mrabet (2008)Continuous wheat 1.60 1.60 19

Tunisia Durum wheat

Continuous wheat 3.90 3.30 2 Vadon et al. (2006)2.18 1.94 5 M’hedhbi et al.

(2003)

Turkey Bread wheat

Wheat–corn 2.40 3.35 – Yalcin (1998)Turkey

(Central Anatolia)

Wheat–fallow 2.16 2.70 3 Avci (2005), Avci et al. (2007)Wheat–chick pea 2.13 2.60 3

Continuous wheat 2.00 2.23 3

Syria Bread wheat

Wheat–chickpea–watermelon

2.53 2.96 12 Pala et al. (2000)

Durum wheat

Wheat–lentil–watermelon

2.08 2.41 12 Pala et al. (2000)

Durum wheat

Wheat–lentil 3.33 3.85 5 Thomas et al. (2007)

Barley Barley–vetch 1.55 1.39 7 Jones (2000)Continuous barley 1.09 1.01 7 Jones (2000)

a Disk plough-based tillage systemb Duration of the experiment

As a conclusion, generally, no-till methods have enabled higher cereal yields to be achieved in the long- and medium-term experiments, but for WANA farmers to be convinced to attempt and achieve this, they need appropriate seed drills and weed control practices.

40.4.2 Yields of Row Crops

These crops include lentils, chickpeas, vetch, corn, sunflower, sesame, cotton and sorghum (Table 40.2). Grain yields of row crops have been consistently higher

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Fig. 40.1 The effect of tillage system on wheat grain yield in a semi-arid Moroccan farm (Mrabet 2008) (Wheat under CT did not yield grain in 1999–2000 because of low growing-season rainfall)

Table 40.2 Row crop grain yield (t/ha) under no-till and conventional tillage in WANA region

Country Species No-tillConventional tillage Years References

North-western Iran

Chickpea 0.81 0.51 3 Hemmat and Eskandari (2004b)

Morocco Corn 1.61 1.50 4a Mrabet (1997)Sunflower 2.71 3.02 2 Aboudrare et al. (2006)

Sudan Sesame 0.77 0.18 2 Rasheed and Hamid (2003) Rasheed et al. (2006)Sunflower 1.21 0.40 2

Corn 2.63 0.59 3Cotton 1.12 0.53 2Sorghum 2.57 1.24 2

Syria Lentil 0.90 0.80 12 Pala et al. (2000)Lentil 1.10 1.10 12 Pala et al. (2000)Chickpea 0.80 0.77 12 Pala et al. (2000)Lentil 1.12 1.14 5 Thomas et al. (2007)Vetch 0.67 0.77 7 Jones (2000)

Western Turkey Corn 6.40 6.70 2 Bayhan et al. (2006)a Water regimes dry to wet depending on amount of water added as supplementary irrigation

under no-till than either mouldboard or chisel ploughing in Sudan and in north-western Iran. However, in Syria, Morocco and Western Turkey, crop yields under NT and CT were similar.


What emerges from the results shown in Tables 40.1 and 40.2 is that no-tillage systems can produce yields that are usually as high as or higher than those from crops produced by conventional tillage; but they can also create other long-term challenges, such as weed and pest infestations. Row-crop yields in semi-arid WANA regions can be profitably increased, in the short- and long-term, with a combination of an adequate no-till seed drill and careful weed management (Mrabet 2008).

40.4.3 Water Use Efficiency by Crops and Crop Diversification

Drought and intermittent water deficit have been major constraints to crop produc-tivity in the semi-arid regions of WANA; extended dry periods are common, especially in the critical grain-filling stage in late spring (Yacoubi et al. 1998). Crop rotation is a key component of a sustainable agriculture, but the rainfall (300–500 mm) and soils of dry lands often limit the options for varying cash crops. Thus efficient use of rainfall is critical for maximising the range of crops grown.

WUE can be defined as the ratio of crop grain yield to precipitation used during the growing season, and is a basic agronomic indicator of the effectiveness of agri-cultural practices (see Chap.1 for more information). Elimination of soil tillage for seedbed preparation, together with residue retention enhance WUE by reducing losses due to runoff and evaporation and decreasing soil surface temperature (Lal 2008; Mrabet 2008). Thus water use efficiency and crop yield in arid zones with an annual precipitation of less than 300 mm can be increased by implementing a no-till (residue retention) wheat–fallow rotation (Bonfil et al. 1999; Bouzza 1990).

A no-till system with residue retention helped to increase wheat WUE in three rotations in Iran (Table 40.3), but water is wasted if fields are left fallow in years with above-normal precipitation (Hemmat and Eskandari 2004a, b, 2006).

According to Bouzza (1990), in Morocco no-till and reduced tillage systems increased WUE in both continuous and wheat-fallow rotations. These results are confirmed by Mrabet (2000b) for continuous wheat (Table 40.4).

Table 40.3 Wheat rainfall use efficiency as affected by tillage systems and rotation in Iran (average of 3 years)

Wheat rotation

No-till MD CD

Referencekg/mm/ha

Continuous wheat 4.4 3.0 3.8 Hemmat and Eskandari (2006)Wheat–fallow 5.4 4.4 6.0 Hemmat and Eskandari (2004b)Wheat–chickpea 4.9 3.8 4.3 Hemmat and Eskandari (2004a)

MD mouldboard ploughing followed by disking, CD chisel ploughing followed by disking. Rainfall use efficiency is calculated by dividing dry grain yield by growing season precipitation (October–June)

1022 R. Mrabet

In Syria (Tel Hadya) over 12 years (Table 40.5), average WUE declined under no-till, compared to disk ploughing and chisel ploughing. This was due to a gradual increase in grassy weeds and inappropriate weed control in early seeding of bread and durum wheat (Pala et al. 2008). However, lentil and chickpea WUE were not affected by tillage systems, where seasonal rainfall ranged from 234 to 504 mm.

Changes in cropping patterns from continuous cropping of wheat to more diver-sified rotations are good indicators of the success of the transition from conven-tional tillage systems to conservation agriculture. No-till and straw mulch management improve soil water storage efficiency and increase the potential in dry climates to plant more intensively and with greater diversity of crops than with the traditional crop–fallow system. In semi-arid Morocco, the 3-year rotations (fallow–wheat–barley, fallow–wheat–vetch, and fallow–barley–lentil) are now recom-mended in place of common continuous wheat and wheat-fallow (Mrabet 2008) in areas receiving between 300 and 500 mm annual rainfall.

40.4.4 Weed and Disease Management

Weeds are a major problem in rainfed WANA agriculture, especially in North Africa where weedy fallows used for grazing ensure a continued supply of weed seed. The frequency of control of the weeds varies with tillage systems, rotations and herbicide

Table 40.4 Wheat water use efficiency as affected by tillage systems and rotation in Morocco (average of 4 years)

Wheat rotation

No-till MD CD

Referencekg/mm/ha

Continuous wheat 7.1 6.6 7.1 Mrabet (2000b)Continuous wheat 9.6 7.5 8.5 Bouzza (1990)Wheat–fallow 9.9 9.2 8.8 Bouzza (1990)

MD mouldboard ploughing followed by disking, CD chisel ploughing followed by disking. Rainfall use efficiency is calculated by dividing dry grain yield by growing season precipitation (October–June)

Table 40.5 Wheat water use efficiency as affected by tillage systems and rota-tion in Syria (average of 12 years)

Wheat rotation

No-till DP CD

Referencekg/mm/ha

Wheat–lentil–melon 6.4 7.3 7.2 Pala et al. (2008)Wheat–chickpea–melon 7.7 8.9 8.9 Pala et al. (2008)

DP disk ploughing followed by harrowing, CD chisel ploughing followed by diskingWater use efficiency is calculated by dividing dry grain yield by growing season (October–June) precipitation, corrected for pre- and post-season water in the soil profile


strategies (Tanji 1995a, b). Consequently, changing tillage systems will change the distribution and density of weed seeds in agricultural soils. Understanding how the different tillage systems affect evolution of weed populations could help organise more effective weed management programmes (see also Chap. 8).

Under NT, weed control is often laborious and costly in the first years. Farmers will need good knowledge of herbicides, weeds and application technology to man-age no-till crops successfully (Derpsch 1998). An integrated weed management programme—combining crop management, allelopathy and herbicides—has been proposed for successful implementation of no-till systems in farmers’ fields (Mrabet 2008).

During the past few decades, the development of effective herbicides and appli-cation methods has made it possible for farmers to control weeds in rainfed no-till systems (El-Brahli et al. 1997; El-Brahli and Mrabet 2000). In these systems, crop and herbicide rotation have been cited extensively as an effective method of weed management.

Reduced tillage increases the risk of foliar disease epidemics because increased levels of primary inoculum are present on crop residues at the soil surface; so plant disease control has been critical to the acceptance of no-till systems (Sturz et al. 1997). So far, grain and straw have not promoted any important disease outbreaks in NT crops in Morocco (Mrabet 2008).

40.4.5 Integrating Livestock and Crop Residue Management

In the low-rainfall areas of much of Africa and Asia, sheep and goat husbandry and cereal cropping are the two most important agricultural activities (Belaid and Morris 1991), with livestock considered as the key to security for smallholder farmers. Crops and livestock are ethnically, functionally and operationally linked enterprises (Schiere et al. 2002). However, these low-rainfall areas are characterised by a rapidly growing livestock population with inadequate sources of feed (Mrabet et al. 2007; Ben Salem and Smith 2008).

Crop residues are important for livestock feed in semi-arid WANA, so mulching with crop residues for CA profoundly alters the flow of resources on the farm. Wheat straw, mostly for feeding animals, represents an important commodity; its average sale price per unit weight being not less than 40% of that of grain (Annicchiarico and Pecetti 2003; Table 40.6). In recent years, however, an increase

Table 40.6 Ratio of prices of durum wheat straw to grain (on a dry weight basis) in three Mediterranean regions (Annicchiarico and Pecetti 2003)

Country Ratio

Palestine 0.55Syria 0.43Morocco 0.41

1024 R. Mrabet

in stubble burning has been observed in several countries, particularly in Syria (Tutwiler et al. 1990), and this is a contentious crop management issue.

No-till agriculture requires a critical level of crop residues (a minimum of 30% cover) to maintain or enhance soil quality and prevent land degradation. No-till crops and livestock compete for the same resources and require proper integrated management to meet objectives of sustainable production of both animal products and grains.

Means to strengthen the co-evolution of agriculture and livestock under no-till may depend on the local conditions of farmers (Mrabet et al. 2007). Strategies for resolving the problems of the integration of crops and livestock while developing no-till systems include:

Introduction of annual forage legumes (i.e. vetch and Sulla (• Hedysarum coro-narium)) in the cropping systems. These are an important source of high-quality feed for animals (Abd El Moneim and Ryan 2004), for nitrogen inputs and as a weed and disease break from cereal monocultureIntroduction of cash crops for generating higher returns to guarantee feed pur-• chase, especially if supplementary irrigation is possibleAllocation of adequate crop residues for soil protection and enrichment, as well • as for livestock feed. It has been estimated that some 30% of the residues can be used for livestock feed without reducing wheat grain yields in semi-arid Morocco (Mrabet 2002)Flexible, seasonal, controlled grazing on stubble with appropriate stocking rates • to avoid overgrazingEstablishment of forages for direct grazing and for cut-and-carry (use of fodder • trees, shrubs and cactus)Conservation through ensiling and the use of supplemental feed blocks to give • more efficient use of a wide range of agro-industrial by-productsTemporary transfer of animals to pasture to allow degraded soil to recover• Strategic application of inorganic fertilisers and manure to enhance crop bio-• mass yields and soil qualityProduction of better-quality straw through genetic improvements.•

40.5 Effect of No-Till on Soil Quality

Soil quality and productivity are interlinked (Cassman 1999) and both must be maintained as population pressure increases. The environmental benefits of adopt-ing no-till with residue retention are wide-ranging both on- and off-farm. No-till can deliver a range of benefits that are increasingly desirable in a world facing population growth, environmental degradation, rising energy costs and climate change, among other daunting challenges (Uri et al. 1998). However, the immediate problems of poverty, food insecurity and poor agricultural productivity relegate soil degradation prevention to a lower level of the farmer’s list of priorities.


40.5.1 Soils of WANA

The soils of the region are diverse, reflecting the influence of geology, topography, vegetation and climate. The major soil orders are: Lithosol, Inceptisol, Entisols, Aridosols and Vertisols3 (Kassam 1981). The soils have high levels of free calcium carbonate and low contents of organic matter and major nutrients (N and P).

Conventional tillage has adverse impacts on the soil physical properties impor-tant for crop growth, whereas conservation agriculture has been shown to increase soil physical, chemical and biological fertility under a wide range of conditions. No-till systems with retention of surface residue create a biologically-intensive and ecologically-protective interface between the soil profile and the atmosphere. The impact of any soil and crop management practice on soil quality attributes in any ecosystem can only be assessed objectively under long-term agronomic trials (Kapur et al. 2007). However, there are few such trials that include effects of tillage systems.

40.5.2 Water Conservation and Control of Evaporation

Control of soil evaporation by reducing or eliminating tillage and retaining surface residues conserves water in the root zone and improves biomass productivity (Mrabet 1997). Increased water conservation results from increased infiltration and reduced evaporation from the soil surface. Figure 40.2 shows that, after watering,

3 This chapter uses the FAO system of soil classification.

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Fig. 40.2 Cumulative soil surface (0–100 mm) evaporation under no-till with various levels of residue cover (Mrabet 1997) (data taken over 57 days following irrigation of plots during summer)

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Fig. 40.3 Cumulative soil surface evaporation (0–100 mm) under various tillage systems (Mrabet 1997) (over 57 days following irrigation of plots during summer). No-till with 80% residue cover, chisel with 45% residue cover, disk harrow with 12% residue cover, rotary tiller and disk plough were bare (no residue cover)

evaporation decreased as the amount of residue was increased, and the surface soil remained moist for longer. Most evaporation occurred from a bare, no-till surface.

No-till with residue cover tended to be better than all other tillage systems (Fig. 40.3) until the end of the 57 day measurement period. No-till crops become more tolerant to drought because of the better storage of water, either in the fallow or during the growing season.

Compared with a clean, cultivated fallow, water storage efficiencies in fallow improve with stubble mulching (but not stubble incorporation) and improve fur-ther with deletion of cultivation in a no-till (chemical) fallow (Table 40.7). NT with sufficient residue cover can increase water storage efficiency by 40% by reducing evaporation early in the fallow (Peterson et al. 1996), and this can be

Table 40.7 Storage effi-ciency and amount of stored water for different types of fallow in semi-arid Morocco (Bouzza 1990)

Type of fallowFallow storage efficiency (%)a

Amount of stored water (mm)b

Chemical 28 84Clean 18 54Stubble mulch 21 63Weedy 10 30a Calculated as the ratio of stored water and the rainfall received during fallow periodb Amount of water stored in 1.2 m profile


used either to increase crop yields, or if sufficient water is available, to increase cropping frequency (Bouzza 1990; Avci 2005).

40.5.3 Soil Erosion Management Using No-Till

Erosion and other related soil degradation effects are the most important threats to food production and security in the Mediterranean Basin (Bou Keir et al. 2001), yet many WANA farmers seem unconcerned about the problem. Soil losses due to ero-sion in the region (Table 40.8) are the highest in the world with annual levels reach-ing as high as 2,000 t/km2 (20 t/ha/year) in Algeria (Demmak 1982) and 4,000 t/km2 (40 t/ha/year) in Morocco (Belkheri 1988).

In the Mediterranean basin, erosion induced by tillage can cause irreversible soil degradation (Roose and Barthès 2006). Mechanical tillage may cause a form of desertification with a denuded soil, decrease of its effective rooting volume, deple-tion in its nutrient capital and a reduction of its water-holding capacity (Lahmar and Ruellan 2007). The traditional tillage system based upon off-set disking caused runoff and soil loss under rainfall simulation and surface sealing in response to soil pulverisation in semi-arid Morocco (Dimanche and Hoogmoed 2002).

Soil cover is the most important factor that influences water infiltration rate into the soil, thus reducing runoff and erosion. Dimanche (1997) found that a no-till treatment reduced the runoff volume by 30–50% and sediment loss by 50–70% compared with disk ploughing on a sandy clay loam soil at Ras Jerri (Meknes, Morocco). In comparison, with chisel ploughing, no-till reduced runoff volume by 24–53% and sediment loss by 43–65%.

In Tunisia, despite low residue cover, NT and direct seeding reduced average annual soil losses by 30–40% compared to conventional tillage (2–4 t/ha/year vs 3–7 t/ha/year). Water infiltration rates were 65 mm/h versus 45 mm/h for no-till and conventional tillage, respectively (Raunet et al. 2004).

Table 40.8 Extent and erosion rates in selected countries of WANA

Country% of country’s area subject to erosion Soil lossa References

Algeria 45 Chebbani et al. (1999)Lebanon 50–70 t/ha/year FAO (1986)Morocco 40 FAO (1990)Syria 50–200 t/ha/year FAO-UNEP-UNESCO (1980)Tunisia 45 Chevalier et al. (1995), Boussema (1996)Iran 38 Lal (2001)Turkey 50 Celik et al. (1996)a Soil loss tolerance under Mediterranean climate varies between 2.5 and 12.5 t/ha/year. It is defined as the maximum amount of erosion at which the quality of a soil as a medium for plant growth can be maintained

1028 R. Mrabet

40.5.4 Water Dynamics in Soils

No-till facilitates water infiltration. In Iran, the ease of early water entry in soil by capillarity was slightly higher in no-tilled loamy soil (0.425 cm/s0.5) than in conven-tionally-tilled soil (0.3 cm/s0.5) (Sepaskhah et al. 2005). Soil disturbance through tillage reduces soil organic matter (SOM) and the number and stability of soil aggregates; it consequently induces a decline in physical and hydrodynamic proper-ties of the soil (Mrabet et al. 2001a, 2004; Lahlou and Mrabet 2001).

As recorded in Fig. 40.4, infiltration rates under well-managed NT are higher over extended periods than under conventional tillage systems—mainly because of better soil porosity. Essentially, NT takes advantage of biological processes in the soil to accomplish biological tillage; this improves networks of interconnected pores, nutrient recycling, and soil physical and biological health.

40.5.5 Carbon Sequestration Under No-Till

Conventional agriculture is said to contribute 15% of greenhouse gas emissions, most of it from soils (40%), enteric fermentation4 (27%) and rice cultivation (10%) (Baumert et al. 2005). Soil organic matter is recognised as an indicator for soil

4 Enteric fermentation is fermentation that takes place in the digestive systems of animals (methane production in ruminant animals).

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/hr)

0,32 0,74 1.25

Fig. 40.4 Impact of tillage system on infiltration process in Sidi El Aydi clay soil. Conventional tillage = off-set disking (Mrabet 2008)


quality and agro-ecosystem fertility (Manlay et al. 2007). In rainfed farming, reaching and maintaining an adequate level of SOM is crucial to sustaining soil fertility, increasing soil moisture storage and mitigating drought (Rosenzweig and Hillel 2000). Under high temperatures and low precipitation, organic matter is oxidised quickly, and development of sustainable farming systems becomes difficult.

NT systems increase the maintenance of carbon inputs (e.g. residue retention) and reduce soil organic carbon decomposition (e.g. through reduced tillage) (Ibno-Namr and Mrabet 2004). Soil organic C was higher under NT than CT in a number of experiments (Table 40.9). The effectiveness of conservation tillage in carbon sequestration is enhanced when used in conjunction with appropriate crop rota-tions, especially with incorporation of leguminous crops in the rotation cycle (Jenkinson et al. 1999).

40.5.6 Aggregation Process

Soil aggregation involves the binding together of soil particles into secondary units. Soil aggregate stability is the main factor controlling soil permeability and erod-ibility at the soil surface and the transfer of energy and fluids through the profile. It is a function of chemical and biochemical properties of the soil, mainly its organic matter, and is affected by land management e.g. tillage, stubble retention and compaction.

Shifting to no-till generally increases soil aggregate stability (Table 40.10) through increased organic matter at the surface. The process is accelerated with increased crop residue input (Lahlou and Mrabet 2001).

Table 40.9 Effect of tillage systems on soil organic matter (%) in different WANA countries

NT CT

Country Soil order Horizon (cm) Years SOM (%) References

Northern Syria

Inceptisol 0–10 10 1.75a 1.10b Ryan (1998)

Morocco Vertic Calcixeroll 0–5 5 1.73a 1.66b Ibno-Namr (2005)Vertic Calcixeroll 0–20 11 2.89a 2.35b Saber and Mrabet

(2002)Central Iran Calcic Cambisol 0–20 4 1.84a 1.44b Hajabbasi and

Hemmat (2000)Norwest Iran Calsixerollic

Xerocherepts0–15 3 0.95a 0.90a Hajabbasi (2003)

Values followed by the same letters are not significantly different at 5% level

1030 R. Mrabet

40.5.7 Effect of Tillage System on Soil Compaction and Consolidation

Soil compaction decreases porosity and increases bulk density (BD). Crop growth can be reduced by bulk density higher than a critical level (Andrews et al. 2002). Compaction in agricultural soils can be a serious problem because it restricts root growth and the uptake of nutrients and water by crops (Oussible et al. 1992). Surface soil density is generally higher in unploughed soils, and NT methods maintain this greater bulk density. However, as shown in Table 40.11, values do not exceed critical bulk density levels for optimal plant growth (1.3–1.5 t/m3) (Dimanche 1997).

Most agriculturalists in WANA have been advising mouldboard and disk ploughing to facilitate water entry, infiltration and conservation (Karaca et al. (1988) in Turkey; Mansouri (1995) and Mansouri and Chaabouni (1996) in Tunisia and Kribaa et al. (2001) in Algeria). However in Central Iran, reduced tillage systems (chiselling) appear to be the accepted alternative management compared to conven-tional practice (mouldboard plough) and no-till (Hajabbasi and Hemmat 2000).

Ploughing may loosen a clay soil more than chiselling and no-till, but natural processes and tillage for seedbed preparation cause the soil after planting to be re-compacted to about the same density as before.

In Central Anatolia (Turkey), a medium-textured clay loam soil (Cambisol) exhibited greater soil strength and bulk density under no-till, regardless of depth,

Table 40.10 Tillage effect on soil aggregate stability in different WANA countries

Country SoilHorizon (cm) Unit NT CT References

Morocco Mollisol 0–2.5 PSAa 65 48 Lahlou and Mrabet (2001)

MWDb 3.78 3.21 Saber and Mrabet (2002)

Vertisol 0–5 MWD 3.40 2.90 Kacemi et al. (1992)Central Iran Calcic Cambisol 0–15 MWD 0.62 0.41 Hajabbasi and Hemmat

(2000)a Percent of water aggregate stability (1–2 mm aggregates)b Mean weight diameter (mm). An index of soil aggregate stability which is equal to the sum of products of the mean diameter of each size fraction and the proportion of the total sample weight occurring in the corresponding size fraction

Table 40.11 Dry bulk density (t/m3) of soil surface (0–5 cm) as affected by tillage systems

Country Soil type NT MT/RT CT References

Central Anatolia (Turkey) Clay loam 0.98 0.80 0.82 Yavuzcan (2000)Sandy 1.34 1.28 1.34 Cakir et al. (2003)

Morocco Clay 1.26 1.23 Mrabet (2006)Clay 1.08 1.01 Kacemi et al. (1992)

NT no till, MT minimum tillage, RT reduced tillage, CT conventional tillage


compared with conventional tillage systems (Yavuzcan 2000). However, all tillage systems allowed optimum root growth (Raper et al. 1993).

The high levels of soil organic matter under no-till reduce soil surface compac-tion in the long term, and biological activity is more intense in undisturbed than in cultivated soils.

No-till farmers should not worry about short-term increases in surface consoli-dation when changing to no-till systems, but may find it beneficial to break any plough pan first.

40.5.8 Soil Chemical and Biochemical Properties Under No-Till

In the WANA region, nutrient deficiencies are widespread, and fertilisers are needed for economic yields.

The introduction of no-till requires an understanding of the change in N dynamics and fertiliser use efficiency. In a no-till system, stratification of crop residues, soil organic matter and soil biota slows cycling of N and other nutrients. The conse-quent imbalance between crop demand and N supply from the soil may increase the requirement for N input into the system, especially in early years.

Residue retention in no-till is often associated with more stable year-to-year soil moisture, but large amounts of cereal residues with a high C:N ratio (>30:1) that are left on the soil surface temporarily result in a net immobilisation of mineral N in the soil. However, residues with a lower C:N ratio (<10:1) such as green legume mate-rial, increase soil concentrations of plant-available nutrients as soon as environmen-tal conditions allow enough microbial activity. Release of P and S from crop residue can follow temporal patterns similar to N. Soil organic matter, nitrogen and phos-phorus content of the soil surface (0–5 cm) increased linearly with increased crop residue maintained on the surface (Ibno-Namr and Mrabet 2004; Ibno-Namr 2005). Total nitrogen (Table 40.12) at the seeding zone (0–7 cm) was much higher under NT than CT (Mrabet et al. 2001b) but differences were smaller below this depth.

Crop residue releases nutrients more slowly than artificial fertiliser applied in a single dose at the start of the growing season. When converting to no-till systems, more nitrogen fertiliser is normally applied to compensate for slow release from organic matter—especially under sub-optimal physical and biological conditions. NT wheat farmers not using adequate mineral fertiliser will suffer N deficiency and yield reductions in early years of adoption. Maintenance of optimal nutrient require-ments under NT will lead to higher yields, repeated additions of relatively large amounts of crop residues and consequently a greater soil C content. This may lead to greater net N mineralisation after a new equilibrium is achieved (Erenstein 2002). Thus, optimum fertilisation is more critical with NT, and soil analysis is necessary before applying fertiliser. Split N application may increase efficiency, and precise banding to separate fertiliser from residues can reduce N immobilisation.

No-till management causes surface enrichment of low mobility nutrients such as P and K (Mrabet et al. 2001b; Ibno-Namr and Mrabet 2004), from both crop residues

1032 R. Mrabet

and P fertilisers. There is also a slight lowering of pH of the surface soil which can increase availability of other nutrients to crops (Table 40.12).

Like mineralisation of organic N, mineralisation of organic P is mediated by soil micro-organisms. Net P mineralisation is usually positively correlated with residue P concentration and negatively correlated with C/P ratio and lignin concentration or lignin/ P ratio.

The likely advantage of direct drilling is the formation of a thin surface layer rich in accumulated plant available P, which can thus meet plant P requirements at the early growth stages. However, there is a decline in P and K content with depth below the seed zone under NT, and this may require deep P and K banding to avoid any risk of deficiency in the crops (Table 40.12).

Tillage affects the soil physical and chemical environment in which soil organ-isms live. By affecting soil water, temperature, structure, aeration and the location of crop residue, no-till methods influence the environment and food supply to soil flora and fauna. By avoiding soil disturbance, mulch from leftover residues pro-motes increased microbial activity, protection of the soil surface, and accumulation of particulate organic C in the soil (Bessam and Mrabet 2001, 2003).

40.6 Economic Benefits: Putting Principles into Practice

No-till research and development programs have been implemented in more than 40 countries, but NT crop production has been adopted extensively in only a few regions. No-till has revolutionised agricultural systems because it allows individual

Table 40.12 Soil total nitrogen, extractable-P, exchangeable K and pH under no- and conventional tillage applied for 11 years (Mrabet et al. 2001b)

Depths (mm) No-till Conventional tillage Difference

Total nitrogen (g/kg)0–25 1.84A 1.33B 0.5125–70 1.49A 1.34B 0.1570–200 1.20A 1.20A 0

Extractable P (mg/kg)0–25 29.9A 18.0B 11.925–70 19.3A 16.5B 2.870–200 8.7B 10.9A −2.2

Exchangeable K (mg/kg)0–25 476.4A 284.1B 192.325–70 291.7A 256.9B 34.870–200 148.6B 177.9A −29.3

pH( water)0–25 7.8B 8.0A −0.225–70 8.1A 8.0A 0.170–200 8.2A 8.2A 0

Means followed by the same letters in the row do not differ by LSD test at p = 0.05


producers to manage greater amounts of land with reduced energy, labour, and machinery inputs. In addition, NT controls erosion, and improves water and fertil-iser use efficiency resulting in higher crop yields. Increases in crop yields and sav-ings in production cost contribute to the overall profitability of no-till systems for wheat in the WANA region (Mrabet 2001a; Pala 2000).

40.6.1 Production Costs and Returns Under No-Till

To be economically attractive for WANA farmers, no-till must be perceived by them to provide a net economic benefit in terms of lower production costs, higher crop yields, higher net returns, lower business risks or some combination of these. While the elimination of tillage operations is a significant advantage of NT, the costs of agricultural inputs—herbicides, pesticides, fertilisers and certified seeds—promoted as part of the NT packages, have been deemed sig-nificant barriers to NT adoption by smallholders throughout the region (Mrabet 2001a).

WANA farmers face rising input prices, particularly for fuel, chemicals, fertilisers and machinery, and constant, or even declining, prices for the com-modities they produce. Their long-term economic viability relies on long-term productivity; NT permits greater stability in yields and consequently higher ratios of outputs to inputs. In Lebanon, average cost of production was about $250/ha less in no-till than conventional tillage system (Bashour and Bachour 2008). Production costs for no-till become higher in the presence of difficult-to-control weeds as these can substantially raise herbicide costs (Mrabet 2008).

40.6.2 Energy Consumption and Efficiency

Tillage requires the highest power in the agricultural production process. The need for sustainable farming and the increasing cost of fuel in tillage operations will certainly encourage farmers to change to no-till.

Energy for primary and secondary tillage operations varies according to factors such as soil type and condition, the amount and type of residues, the plough depth employed and differences in machinery and tillage implements. Differences in terms of energy and time savings between no-tillage systems and an array of con-ventional tillage systems (El Gharras et al. 2004; Dale and Polasky 2007) are shown in Table 40.13. No-till is about eight times more efficient in fuel consumption than conventional tillage and eliminating tillage can be more energy efficient than elimi-nating herbicide use (El Gharras et al. 2004).

In the light soils of Odemis in western Turkey, conventional tillage and planting required seven times more fuel than direct-planting, while a no-till system had five

1034 R. Mrabet

times more field efficiency5 than conventional tillage (Yalcin and Cakir 2006). Direct drilling may require more power than sowing in tilled fields. However, with time, no-till planting is done in better structured soils, with lower machinery and fuel costs (Fig. 40.5, Bourarach 1989; Chekli 1991).

8,310,3

8,5 7,8

19,2

6

0

5

10

15

20

25

Disk p

low

Chisel

Mold

boar

d plo

w

off-s

et d

isk

Rotot

iller

No-till

age

Tillage systems

Fu

el c

on

sum

pti

on

(lit

er h

ou

r-1 )

Fig. 40.5 Fuel consumption by tillage operations (Bourarach 1989). Fuel consumption refers to the quantity used for each operation for seedbed preparation and planting of wheat

5 See glossary.

Table 40.13 Energy, time and power use by different tillage systems in Morocco (El Gharras et al. 2004)

Tillage systems Power (hp/m) Time (h/ha) Fuel use (L/h)Number of passes

Conventional tillage system 100–140 6.5–8.5 31–45 4Deep disking 50–70 3–4 10–15Stubble plough 20–30 2–2.5 10–12Seedbed preparation 15–25 1–1.5 6–8Seeding 15 0.5 5

Simplified Tillage system 50–70 3.5–5 21–25 3Stubble plough 20–30 2–3 10–12Seedbed preparation 15–25 1–1.5 6–8Seeding 15 0.5 5

Traditional tillage system 30–40 2–2.5 11–13 2Off-set disking 15–25 1–1.5 5–8Seeding 15 0.5 5

No-till: Seeding (no-till drill) 25–35 0.6–1 5–7 1


40.6.3 Machinery Development

No-till requires the integration of several components: machinery, pesticides, seeds, rotations, crop residues, knowledge and skills. Limitations can usually be overcome by modifying technology, as in no-till seed drills. Specialised drills are able to place the seed accurately, in intimate contact with an undisturbed soil, while operating on a thick crop residue layer.

Across the world, more than 100 manufacturers offer no-till machines and accessories capable of specific requirements in direct planting and nutrient manage-ment (Murray et al. 2006), but their high price, and restricted availability are a drawback for low-income farmers (Mrabet 2001b; Vadon et al. 2006).

Obstacles to NT adoption by smallholders are manifold and diverse (Mrabet 2008). However, advances in design and manufacture of seed drills by local manu-facturers have allowed farmers to experiment and accept this technology, as in Morocco (Mrabet 2008) and in the Indo-Gangetic Plains (Baker et al. 2007). The no-till drill designed in Morocco to plant rainfed cereals (Bahri et al. 1993; Bourarach et al. 1998) is a hoe type that moves the dry surface soil to the side, 5–10 cm deep, to allow the seed to be placed near the P and N fertilisers. However, most imported no-till drills are disk types and are available through international companies.

40.7 No-Till Sociology: Bridging Farmer and Scientific Knowledge

Despite the wealth of research showing the benefits of the no-till system, it is not yet practiced extensively in WANA. There is often a delay in the benefits of CA as the farmer switches from exploiting his soils to improving them. In Brazil, NT was first introduced to farmers in the mid-1970s but it took almost 15 years before the NT area reached 1 million hectares (Derpsch 2005).

The no-till system is a knowledge-intensive system more than an input-intensive system. It is not only a production technology but also a social construct, being a complete departure from conventional tillage. For Hobbs (2007), probably the first challenge faced in spreading the use of no-till systems was overcoming the mind-sets of farmers in retaining the traditional way of farming, where tillage is consid-ered essential. This needs a common language between farmers, extension workers and scientists. In developing countries, including WANA, the limited adoption of conservation cropping systems is related to the failure to take into account the local experience and needs of farmers. Relevant scientific knowledge must be integrated with local knowledge.

The participation of farmers in this technology transfer can add value to deci-sion making. It can ensure that all relevant environmental and social concerns are addressed and contribute to an honest accounting of the social, economic, and

1036 R. Mrabet

environmental costs and benefits of a decision. These participative approaches have been used in various projects related to conservation agriculture in Morocco (El-Brahli et al. 2004) and in the other countries of the Maghreb region (Vadon et al. 2006).

Institutional constraints that may prevent the adoption of NT include the lack of efficient organisations of farmers and lack of access to markets for suitable direct drills. Poor land tenure security in the rainfed, mixed-farming systems of the devel-oping world and poor access to credit are additional disincentives for investment in no-till systems which must be addressed.

40.8 Conclusions on Implementing No-Till in WANA

The feasibility of no-till for rainfed, small-grain cereals, legumes, sunflower, and other major crops in the major arable areas of WANA has been systematically assessed since the 1980s. In spite of much research and assessment, no-till is still a new experience in agricultural development of most countries of WANA. This is not surprising since conventional tillage was, for centuries, the foundation of both traditional and modern agriculture. Hence, it is of importance to adapt extension services to promote no-till systems.

Our review of the literature illustrates the consistent value of applying no-till systems to rehabilitate degraded agricultural lands, enhance crop productivity and promote social capital in farmers’ holdings of WANA. From individual research projects, it is generally accepted that the less the tillage, the higher the soil moisture in the upper soil horizons due to better infiltration, less runoff and reduced soil water evaporation. Retention and management of crop residues in no-till systems can help reduce water-loss.

Wind and water erosion are the main forms of soil degradation in WANA, and conservation agriculture systems (including no-till) represent effective methods for controlling these problems.

For a durable agriculture in WANA, the main technical components of no-till systems are permanent residue cover, minimal soil disturbance, controlled or zero grazing, diverse cropping rotations and integrated weed and disease management.

WANA farmers are skilled in surviving the severe and diverse environmental and socio-economic challenges associated with conventional agriculture, and they should be capable of adapting to no-till systems. However, their abilities need strengthening and the constraints need to be reduced. Incentive and motivation mechanisms (including subsidies, micro-finance, and access to markets) should be constructed to achieve satisfying results from NT agriculture. Analysis and adapta-tion of research and development results from around the world, as well as from WANA, are needed to provide the most appropriate technology for adoption. Wide adoption of No-till technology will not be based solely on its own technical or agronomic merits; it has to fit with existing local cropping and farming systems.


Decision makers in WANA will need to show dynamism and imagination to bring about this transformation, satisfy the requirements of the transition and hence succeed in establishing a no-till revolution as has occurred in Brazil, USA and Australia.

In conclusion, there is no single strategy for disseminating no-till systems in WANA. NT introduction has to be fitted to local farming conditions and farmers’ experience. Hence, there is a need for partnering among all stakeholders. The start-up or transition phase is critical to the eventual success of any NT adoption process and should be skilfully organised, managed and guided.

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Mrabet 2011