Soil & Tillage Research 126 (2013) 246–258

Conservation agriculture in eastern and southern provinces of Zambia: Long-termeffects on soil quality and maize productivity

Christian Thierfelder a,*, Mulundu Mwila b, Leonard Rusinamhodzi a

a CIMMYT, P.O. Box MP 163, Mount Pleasant, Harare, Zimbabweb Zambia Agriculture Research Institute (ZARI), Farming Systems and Social Sciences Division, P.O. Box 510089, Chipata, Zambia

A R T I C L E I N F O

Article history:

Received 9 May 2012

Received in revised form 8 September 2012

Accepted 11 September 2012

Keywords:

Conservation agriculture

Direct seeding

Sustainable land management

Mulching

Rotations

Soil conservation

A B S T R A C T

Sustainable and resilient cropping systems are required in southern Africa to arrest declining soil fertility

and offset the future negative effects of climate change. Conservation agriculture (CA) has been proposed

as a potential system for improving soil quality and providing stable yields through minimum soil

disturbance, surface crop residue retention (mulching) and crop rotations or associations. However,

concerns have been raised about the lack of evidence of the benefits of CA for small-scale farmers in

southern Africa. This research was carried out in two communities and one on-station site in Zambia to

provide more scientific evidence about the effects of CA on soil quality, infiltration, soil moisture and

crop performance. Results from Kayowozi showed that maize yields in a direct seeded CA treatment,

using cowpea seeded with a dibble stick in full rotation, increased by up to 78% after four cropping

seasons in comparison to a conventional control using a ridge and furrow system. At Malende, maize

yields for animal traction rip-line seeded and direct seeded plots were, on average, 75% and 91% higher

than a conventionally tilled control plot after six cropping seasons. Detailed studies undertaken at the

Monze Farmer Training Centre revealed that CA treatments, especially that using cotton in rotation,

increased water infiltration and soil moisture. In some years, infiltration was five times higher on CA

fields than on those using conventional tillage. Carbon increases were only found at the on-station long-

term trial, where, over time, CA plots outperformed conventional practice leading to an overall increase

of 12% carbon in the first 30 cm, compared with decreases of 15% in the conventional control.

Comparative analyses between the on-farm and on-station trials point to a lack of adequate mulching,

which might be the reason for lower carbon at the on-farm sites. We conclude that the effects of CA can

build up on different soil types in most systems, but that scaling up and out requires the whole

community to be targeted, rather than relying on individual farmers to overcome constraints related to

the set-up in rural communities.

� 2012 Elsevier B.V. All rights reserved.

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Soil & Tillage Research

jou r nal h o mep age: w ww.els evier . co m/lo c ate /s t i l l

1. Introduction

Frequent crop failures and periodic famines are commonthreats to rural farming communities in southern Africa. Unreli-able climatic conditions characterised by frequent droughts andthe potential impacts of climate change (Lobell et al., 2008), as wellas decreasing soil fertility, are major constraints (Kumwenda et al.,1997; Mapfumo and Giller, 2001; Zingore et al., 2005). As a result,there is an increased need for more resilient, water-conserving,productive and sustainable agriculture cropping systems (Thier-felder and Wall, 2010a; Wall, 2007).

Since the 1990s, environmentally sustainable agriculturesystems that improve soil fertility and production capacity haveincreasingly gained attention in research and extension services

* Corresponding author. Tel.: +263 772815230.

E-mail address: c.thierfelder@cgiar.org (C. Thierfelder).

0167-1987/$ – see front matter � 2012 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.still.2012.09.002

in southern Africa (Mafongoya et al., 2006). In support of this,international agriculture research and donor organisations havestarted to promote new systems based on the principles andpractices of conservation agriculture (CA) (Mashingaidze et al.,2006; Mazvimavi and Twomlow, 2009; Mazvimavi et al., 2008;Steiner, 1998). CA is a cropping system originally developed inthe Americas and Australia that combines three key principles:(i) minimum soil disturbance, i.e. no soil inversion by the hoe orthe mouldboard plough; (ii) in situ crop residue retention ofavailable plant material (living or dead) on the soil surface; and(iii) crop rotations and associations to reduce and overcome pestand disease problems in the system (FAO, 2002; Kassam et al.,2009). CA is a complex but fairly flexible agricultural systemthat can be widely adapted to local site conditions (Wall, 2007).On the other hand, CA is not a fixed recipe, blanketrecommendation or panacea, and there is therefore a need totake into account the conditions and socio-economic constraintsof farmers.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 247

Farmers in southern Africa rely on maize (Zea mays L.) as themain staple food crop: it accounts for 50–90% of the caloric intake(Dowswell et al., 1996). Sorghum (Sorghum bicolor L.), grainlegumes such as common bean (Phaseolus vulgaris L.), cowpea(Vigna unguiculata L.), groundnut (Arachis hypogaea), cassava(Manihot esculenta Crantz), sweet potatoes (Ipomoea batatas (L.)Lam) and a variety of vegetables are the other important foodcrops. Traditionally, the mouldboard plough and hand hoe are usedfor land preparation and planting. Maize is sown into tilled moistsoil. Maize is often grown as a continuous monoculture, neglectingthe fact that rotations are important in the agricultural system.Legume crops are seldom grown due to poorly developed markets,land area limitation, and lack of good quality seed, and thus thereturns from rotational crops do not justify their systematicproduction (Snapp et al., 2002; Thierfelder and Wall, 2010b). Inmixed crop–livestock systems, there is competition for cropresidues between mulching and livestock for feed (Baudron et al.,2012b; Giller et al., 2009; Mueller et al., 2001; Valbuena et al.,2012). Farmers also use this valuable resource for fuel andbuilding. In some areas the residues are burned because there is noassociated value involved and termites, especially on loamy andclay soils, make it difficult to retain enough residues (Thierfelderand Wall, 2012). As a result, the soil surface in maize fields is oftenuncovered and, when exposed to heavy rainfall, build up surfaceseals and crusts which reduces rainfall infiltration leading to moresurface run-off and soil erosion (Derpsch et al., 1986; Roth et al.,1988; Thierfelder et al., 2005; Thierfelder and Wall, 2009).Insufficient return of organic matter, combined with excessivesoil tillage in many cases, increases physical, chemical andbiological soil degradation, which is regarded as one of the rootcauses for declining yields in tropical environments, despite thehigh yield potential of crop cultivars (Derpsch et al., 1986, 1991;Kassam et al., 2009; Lal, 1974; Stagnari et al., 2010).

Currently there are a number of technology options available toplant crops under CA (Johansen et al., 2012). The main plantingsystem promoted in Zambia and Zimbabwe since the mid 1990s isbased on manually dug planting basins, a similar system to the zaisystem in the Sahel (Haggblade and Tembo, 2003; Mazvimavi et al.,2008; Twomlow et al., 2006). Another manual CA planting systempromoted in southern Africa is the planting stick (dibble stick),based on a pointed stick used to dig two small planting holes, onefor seed and one for fertiliser. Plant spacing is easy to adjust andstrings with marks are used as guidance for planting stations. Amore mechanized option has been introduced in the form ofmanual jab planters (matracas); however, they are currentlyneither widely available nor used. Farmers with access to animaldraught power can use two distinct systems: (i) manual seedingand fertilisation in previously formed rip-lines created by a Magoye

furrow opener or other ripper tine attachments mounted on theplough beam (GART, 2006); and (ii) direct planting and fertilisationwith an animal traction direct planter from Irmaos FitarelliMaquinas Agricolas, Brazil, or locally produced Jambo directseeders from Grownet Investment, Zimbabwe (Johansen et al.,2012).

CA has potential to improve water infiltration and reduceerosion, improve soil aggregation, reduce soil compaction, increasesurface soil organic matter and soil carbon content, regulate soiltemperature, suppress weeds, reduce costs of production, savetime and reduce greenhouse gas emissions. Benefits have beenhighlighted by previous reviews (see e.g. Govaerts et al., 2009;Hobbs, 2007; Kassam et al., 2009; Wall, 2007). However, thefeasibility and applicability of CA under the specific circumstancesof farmers in southern Africa is questionable (Baudron et al.,2012a; Bolliger, 2007; Giller et al., 2009; Guto et al., 2012). There isa need for locally generated quantitative data to improveknowledge on the benefits and challenges of various CA systems

and to provide evidence that CA is feasible in the farming systemsin southern Africa (Giller et al., 2011), despite the biophysical andsocio-economic constraints (e.g. residue retention, weed control,equipment availability, physical and financial access to inputs,land tenure, knowledge gaps and mindset) highlighted by Wall(2007).

The aim of this study was to investigate the effects of differentCA systems under on-farm conditions in two target communitiesand one on-station experiment on long term maize yield inZambia. The investigated systems are common CA practicescurrently promoted in Zambia and the region and are the mostpromising systems for manual and animal traction smallholderfarmers in this area. Research results are provided for selected soilquality and water parameters (carbon, infiltration, soil moistureand yield) that are commonly accepted as good monitors for soilhealth improvements under different management practices andare easy to measure even in the remote areas of this study. Resultsfrom CA systems were compared to results from conventionallytilled control plots.

2. Materials and methods

2.1. Study area

The study was carried out at two on-farm sites and one on-station trial site where more in-depth soil studies were possible.The first on-farm site was located in Malende Agriculture Camp(Malende) in Monze District, Southern Province of Zambia (16.24S,27.42E; altitude: 1096m); the second was situated in KayowoziAgriculture Camp (Kayowozi), Chipata District, Eastern Province ofZambia (13.70S, 32.61E; altitude: 1070m). The on-farm sites wherespecifically chosen because CA was promoted there since 2005(Monze) and 2007 (Chipata).

Zambia is divided into three major agro-ecological zones, basedon total annual rainfall received in a unimodal pattern betweenOctober and April. Region I receives less than 700 mm of rainfall,regions IIa and IIb receive annual rainfall of between 800 and1200 mm, and region III receives annual rainfall of at least1200 mm. Annual monthly temperatures range between 16 8C and27 8C. Both on-farm sites are located in region IIb.

Results from the on-station long-term trial established at theMonze Farmer Training Centre (Monze FTC), (16.24S, 27.44E;altitude: 1103m) have been previously reported. A detailed sitedescription is given in Thierfelder and Wall (2009).

The trials in Malende and at the Monze FTC were established onLixisols (WRB, 1998) characterised by an argic horizon and somestagnic soil properties in the sub-surface (Table 1). The soils arederived from deposits of the Kafue river watershed and Monze islocated at its southern end. The top-soil texture at Monze containsup to 80% sand and is mainly described as sandy loam, but claycontent increases at 40–50 cm soil depth to form sandy clay loamand sandy clay. The mean long-term rainfall is 748 mm a�1 and thenatural vegetation is dry Savanna.

The Kayowozi area in Chipata district forms part of the centralplateau of the Eastern Province. The soils are characterised by clayloam textured soils described as Acrisols and Allisols (WRB, 1998).The soils are mildly acidic and were found to be low inphosphorous. Chipata is documented to receive between850 mm to 1050 mm a�1 of annual rainfall. Major crops in theEastern Province are maize, cotton and some grain legumes(cowpeas, common beans and groundnuts).

2.2. Experimental design

At both on-farm sites the study was conducted on farmers’fields with a total of six farmers hosting replicates of a validation

Table 1Some soil properties of reference profile D, ferric Lixisol, Monze Farmer Training Centre (FTC), and two farmers’ fields in Malende (K. Mwemba) and Kayowozi (B. Phiri),

Zambia.

Horizons Depth [cm] Bulk density [g cm3] Mottling [vol%] pH [CaCl] CEC [cmol kg�1] C [%] Particle size [%]

Sand Silt Clay

Monze FTCAp 0–21 1.56 – 4.8 2.8 0.60 82 6 12

AB �52 1.55 2 4.8 5.2 0.52 55 8 37

Btg �100 1.33 15 5.2 5.1 0.40 53 8 39

BCcg >105 1.45 >40 5.8 5.5 0.17 71 6 23

Malende0–10 1.25 – 5.0 8.0 0.97 90 8 2

�20 1.33 – 5.0 8.3 0.90 78 2 20

�30 1.36 – 5.0 9.2 0.87 70 10 20

�60 1.36 N/A 5.1 9.1 0.86 78 7 15

Kayowozi0–10 1.32 – 6.1 9.7 0.94 77 13 10

�20 1.34 – 6.2 10.3 0.86 84 6 10

�30 1.39 – 6.0 10.1 0.81 78 10 12

�60 1.52 N/A 5.9 7.4 0.51 76 7 17

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258248

trial at each site. The main crop studied in Malende was maizeplanted in rotation with legumes (soyabean in 2005/06 and 2006/07 and cowpea from 2007 onwards). We report only maize resultsfrom 2006 to 2011 in this paper. Each replicate was 3000 m2 insize, which was sub-divided into three main treatments (1000 m2),and each of those into two sub-treatments (500 m2) containing thetwo phases of a maize-legume rotation:

1. Conventional control plot consisting of mouldboard ploughingand maize planted with a maize-legume rotation (CPML).Ploughing was done at shallow depth (10–15 cm) common incommunal areas of Zambia. Residues of the previous crop wereremoved at each site and used for animal grazing. Remainingstubble was incorporated into the soil using the plough.

2. Conservation agriculture with no-tillage and sown with ananimal traction furrow opener (Magoye ripper) (RIML). Rip-lineswere created at 10 cm depth and 10 cm width. Crop residuesfrom previous years’ harvests were retained in situ as surfacemulch and, as plots alternated, maize was seeded into legumeresidues and legumes into maize residues. The amount ofresidues per treatment varied according to rainfall season andcrop production (Table 2).

3. Conservation agriculture with no-tillage and sown with an animaltraction direct seeder (Fitarelli machinas, Brazil) (DSML). Rip-lines created by the direct seeder were 5–7 cm deep and 5 cmwide. Crop residues were retained as surface mulch, as in RIML.

Table 2Amount of biomass retained on the soil surface (in kg ha�1) on each treatment after harv

retained on each field are either maize, cotton or legumes and, as plots alternate in

corresponding rotation crop (e.g. maize is planted into cotton residues in the maize co

Treatment Biomass yield (kg ha�1)

2005/06 2006/07

Monze FTCDirect seeded, maize 4049 4774

Direct seeded rotation, maize 4312 5386

Direct seeded rotation, cotton 3826 6123

MalendeRip-line seeded rotation, maize 2959 3797

Rip-line seeded rotation, legume 5666 N/A

Direct seeded rotation, maize 3188 4901

Direct seeded rotation, legume 5853 N/A

KayowoziDirect seeded, maize

Direct seeded intercropping, maize/cowpea

Direct seeded rotation, maize

Direct seeded rotation, cowpea

At Kayowozi, maize was planted as a sole crop, as well asrotated and intercropped with cowpea throughout the whole studyperiod. We report results from 2008 to 2011 for maize. Eachtreatment area had a similar size of 1000 m2, and we investigatedfour treatments in this study replicated across six farmers fields inthe community:

1. Conventional control plot consisting of traditional ridge andfurrow land preparations planted with continuous maize(CRFM). Residues were removed after harvest and stubbleincorporated into the ridges.

2. Conservation agriculture plot with no-tillage and continuoussole maize (DISM) planted into previous years’ ridges (wherethey still existed) or direct into the plot without previous ridgeformation. Crop residues from previous years’ harvests wereretained as surface mulch. Maize seeds were planted as solecrops in no-tillage methods using a pointed stick (dibble stick).The holes of the dibble stick were approximately 2–3 cm indiameter and 5 cm deep.

3. Conservation agriculture with no-tillage and plot with maizeintercropped with cowpea (DISM/C). Both crops were plantedwith the dibble stick as DISM into previous years’ ridges (wherethey still existed) or directly into the plot without further ridging.Crop residues were retained as surface mulch, as in DISM.

4. Conservation agriculture with no-tillage and crop residueretention and planted as in DISM and DISM/C, but maize was

est, Monze Farmer Training Centre (FTC), Malende and Kayowozi, Zambia. Residues

the rotations, maize will be always planted in the previous year’s residue of the

tton rotation).

2007/08 2008/09 2009/10 2010/11

4416 5175 3613 4667

5409 6577 4301 4485

3175 2785 3473 2875

6307 5488 4513 5593

6056 2471 2729 1268

6850 4643 5339 7811

3461 2904 2768 1450

1746 4265 3852 7468

1168 858 2036 6236

1363 4579 3409 7034

965 778

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 249

planted in full rotation with cowpea (DISM-C). Maize wasseeded into legume residues and legumes into maize residues.

We selected three treatments from the on-station long-termtrial at the Monze Farmer Training Centre for this study:

1. Conventional control plot consisting of mouldboard ploughingand planted with continuous maize (CPM). Residues wereremoved at each site and used for animal grazing. Remainingstubble was incorporated using a plough.

2. Conservation agriculture with no-tillage and continuous maizesown with an animal traction direct seeder (Fitarelli Machinas,Brazil) (DSM). Crop residues were retained as surface residuesafter each cropping season.

3. Conservation agriculture with no-tillage and sown with ananimal traction direct seeder (Fitarelli Machinas, Brazil) butmaize was rotated in full rotation with cotton (DSM-CT). Cropresidues were retained as surface mulch as in DSM. Maize wasseeded into cotton residues and cotton into maize residues.

Crop management at the sites was slightly different due to site-specific fertiliser recommendations, plant populations and weedcontrol techniques. At Malende and Monze FTC crops were plantedwith the first rains in mid-November in each year at a density of44,000 plant ha�1, fertilised with 109N:33P2O5:17K2O supplied inthe form of a basal dressing at planting, and as top dressing withurea at four and seven weeks after crop emergence. Maize wasplanted spaced 90 cm apart with a 50 cm in-row spacing except forthe direct seeded treatments which were spaced at approximately25 cm in-row intervals. Weeds were controlled with 2.5 l ha�1

glyphosate [N-(phosphonomethyl) glycine] at time of planting inthe CA treatments, only followed by manual weeding with the hoewhen necessary. In the conventional treatment the weed controlwas performed using the plough and mechanical cultivators orhand hoes.

At Kayowozi, the plant population was higher (53,000plants ha�1) due to a higher area-specific recommendation forplant density. Maize was planted in lines 75 cm apart with a 25 cmin-row spacing. Planting was always undertaken at around thebeginning to middle of December. The crops were fertilised with58N:20P2O5:12K2O according to rates recommended in the area, arate which is lower than in Monze. Weed control was achievedthrough 2.5 l ha�1 glyphosate in all CA treatments and 6 l ha�1 of alocal residual herbicide bullet1 (which contains 25.4% Alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide) and14.5% atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine)) in DISM and DISM-C in the maize phase only. Weedcontrol after the use of herbicides was achieved using manualweeding by hand and occasionally using a hand hoe.

2.3. Infiltration and ‘‘time-to-pond’’ measurements

Two different methods of measuring infiltration were used in thisstudy. At the on-station trial at Monze FTC a small rainfall simulator(Amezquita et al., 1999; Thierfelder and Wall, 2009) was used toapply approximately 100 mm h�1 on an area of 32.5 cm � 40 cm(0.13 m�2) for 60 min. Infiltration was calculated as the differencebetween precipitation and run-off from the simulated area. In thefield, infiltration measurements were performed using 12 replica-tions per treatment in the inter-row space between two maize linesin January 2006–2011 when the maize crop was at, or just before, thetasseling stage. The final infiltration rate, as derived from Horton’sinfiltration model, was used to compare treatments (Kutilek andNielsen, 1994). The second method, mainly used on-farm, was the‘‘time-to-pond’’ measurement (Govaerts et al., 2006), where a metal

wire ring of 50 cm diameter was placed on the soil surface betweentwo maize lines and water was added to the middle of the ring with awatering bucket. Time-to-pond was determined by measuring thetime taken for the water to flow out of the metal ring. As a control, theamount of water left in the watering can was recorded at each eventto eliminate outliers. The method had been earlier calibrated withsimulator measurements, and time-to-pond highly correlated withinfiltration (Thierfelder and Wall, 2012). Six measurements weretaken in each replicate for each treatment at each on-farm site.

2.4. Soil moisture measurements

Capacitance probes from DELTA-T Devives Ltd., UK, were usedto determine soil moisture at Monze FTC over time. The equipmentconsisted of access tubes permanently installed in the field in thethree treatments (three access tubes per plot in three replicates)and a soil moisture probe to measure the soil moisture at all accesstubes at regular intervals (weekly measurements during the dryperiod, and two times per week during the cropping season). Thevolumetric moisture content was measured in layers (0–10 cm,10–20 cm, 20–30 cm, 30–40 cm, and aggregated from 0 to 40 cm)and plotted against each other in each layer. Data were collectedfrom October 2008 until October 2010.

2.5. Carbon measurements

The soil was sampled for total carbon analysis at four depths inMalende (0–10 cm, 10–20 cm and 20–30 cm, 30–60 cm) in 2010. AtKayowozi, soil samples were only collected from the first two depthlayers (0–10 cm and 10–20 cm) and at Monze FTC from the firstthree depth layers (0–10 cm, 10–20 cm and 20–30 cm). At MonzeFTC, we also combined data from the top 30 cm collected in 2005,2008 and 2010 to determine the changes in the three treatmentsover time. Total carbon was determined through a CE Elantech FlashEA1112 dry combustion analyser. Carbon stocks (Mg ha�1) werecalculated from the carbon concentration, thicknesses and bulkdensities of the available horizons (Ellert and Bettany, 1995):

CðMg ha�1Þ ¼ conc � pb � T � 10; 000 m2 ha�1

� 0:001 Mg ha�1 (1)

where:

C = amount of C per hectare (Mg ha�1)conc = element concentration (mg kg�l)

pb = field bulk density (Mg m�3)T = thickness of soil layer (m)

2.6. Harvest procedures and analysis

Crops were harvested at physiological maturity. Cobs andabove-ground biomass were collected from 10 samples of 7.5 m2

and 9 m2 (2 rows � 5 m) selected at random from each treatmentat Kayowozi and Malende and from eight samples at Monze FTC.Samples were weighed in the field and sub-samples taken todetermine grain moisture content. A sample of 20 (16 at MonzeFTC) cobs per replicate was shelled to calculate the shellingpercentage (ratio of grain to total cob weight), and grain yield wascalculated on a per hectare basis at 12.5% moisture content. Thedata was then summarised for the seasons 2005/06–2010/11 inMalende and Monze FTC, and 2007/08–2010/11 in Kayowozi.Treatments were compared in scatter plots to evaluate the relativebenefits against the conventional practice, or against each otherthrough time at each site.

Table 3Final infiltration rate in one conventionally ploughed and two direct seeded CA treatments, Monze Farmer Training Centre, Zambia, 2006–2011.

Final infiltration rate (mm h�1)

2006 2007 2008 2009 2010 2011

Conventional ploughing, maize 33.6 b 25.3 b 9.6 b 9.6 b 15.4 b 7.8 b

Direct seeding, maize 52.8 a 47.4 a 33.5 a 46.5 a 47.7 a 41.4 a

Direct seeding, maize-cotton rotation 53.1 a 47.6 a 31.1 a 48.7 a 46.6 a 46.3 a

LSD 16.8 18.8 16.4 21.1 15.7 20.3

P-level 0.05 0.01 0.01 0.01 0.01 0.01

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258250

2.7. Statistical analysis

Statistical analyses were carried out using STATISTIX forpersonal computers (Statistix, 2008). Infiltration, time-to-pond,total carbon and yield data were tested for normality and subjectedto an analysis of variance (ANOVA) using a completely randomizedblock design. Where the F-test was significant, a least significantdifference (LSD) test was used at P � 0.05, if not stated otherwise,to separate the means.

3. Results

3.1. Infiltration

There was a significant treatment effect on infiltration at theMonze Farmer Training Centre from the first year onwards (Table3). Infiltration in the direct seeded CA treatments exceeded theconventionally ploughed control treatment, in all years. The largestdifferences were found in 2010/11 when DSM-CT had a 494% andDSM had a 430% higher final infiltration rate than the convention-ally ploughed control.

3.2. Time-to-pond

The difference in time-to-pond measured on farmers’ fieldswas not as clear as when measured with the rainfall simulator atMonze FTC. Nevertheless in 2011, when time-to-pond wasmeasured during the dry season, we found significant differencesbetween CA treatments and the conventional control plots (Table4). In Malende both direct seeded treatments were the same,whereas the result for CPM was reduced. In Kayowozi, time-to-pond was highest in the dibble stick treatments with maize-cowpea rotation, followed by the intercropped treatment. Thelowest time-to-pond was recorded in the conventional ridge andfurrow system.

Table 4Time-to-pond measurements in conventional and conservation agriculture

treatments at Malende and Kayowozi, Zambia, 2011.

Treatment Time to pond (s)

MalendeConventional ploughing 10.2 b

Ripline seeding 11.6 a

Direct seeding 11.6 a

LSD 1.1

P level 0.01

KayowoziConventional ridge and furrow 12.3 c

Dibble stick, sole maize 13.3 bc

Dibble stick, intercropping 14.4 ab

Dibble stick, maize rotation 14.9 a

LSD 1.6

P level 0.05

Means followed by the same letter in column are not significantly different at the

respective P-level.

3.3. Soil moisture

Soil moisture was higher in all four of the depth layers in thedirect seeded CA plots at Monze (Fig. 1) throughout the croppingseason. The highest moisture content (in vol%) was recorded inmaize in rotation with cotton (DSM-CT) treatment; only in thecircumstances of a few rainfall events was the direct seeded solemaize (DSM) treatment higher than DSM-CT. During the drying outphases after the cropping season, DSM-CT maintained more soilmoisture than the other treatments. The layer at 20–30 cm wasparticularly interesting in this comparison, with a greaterdistinction between treatments (Fig. 1). When all four layers werecombined into one moisture profile of 0–40 cm (Fig. 2), weobserved that both CA treatments had more moisture (in mm) thanthe conventional control plot.

3.4. Total carbon

Total carbon measured in October 2010 on farmers’ fields didnot reveal any significant treatment-induced differences at anylevel, but the on-station trial showed significant differences in thefirst 10 cm (Table 5). It was highest in DSM-CT followed by DSM, incomparison with the conventionally ploughed control. The trend inthe top 30 cm over several cropping seasons (Fig. 3) showed thatthe conventionally ploughed control had a steadily decreasingcarbon content (with an overall loss of 15%) while the DSMmaintained its carbon level (overall decrease 2% from 2005 to2010) and carbon increased in DSM-CT (increase of 12%). In 2008,only DSM was higher than CPM, but in 2010 both CA treatmentsshowed significantly higher carbon than the conventional control.

3.5. Crop yield

The comparison of maize yields among treatments in Malendedid not show any significant difference in the first three croppingseasons but variability was also high between plots (Fig. 4). In thefourth cropping season (2008/09), differences started to emergewith both CA treatments being higher than the conventionalcontrol. In 2009/10 only DSML yielded higher than the control plot,whereas in 2010/11 both CA treatments were again higher. In2010/11, the sixth cropping season in the experiment, yield inDSML exceeded yield in the conventional control by 91% and inRIML by 75%. In Kayowozi, the rotational CA treatment (DISM-C)was different from the other treatments from the second croppingseasons onwards (Fig. 5). In 2008/09, yield in DISM-C was higherthan in the conventional ridge and furrow system (CRFM) and inthe intercropped treatment (DISM/C). In 2009/10, significantlyhigher yields were only recorded in the DISM-C treatment and washighest in 2010/11. It was remarkable that DISM/C did not performwell in the first seasons but yields increased gradually throughoutthe duration of the experiment, leading to similar high yields thanDISM and CRFM after the fourth cropping season.

At the Monze FTC, the maize-cotton treatment under CA (DSM-CT) yielded significantly higher in all the cropping seasons

Fig. 1. Development of seasonal soil moisture (in vol%) in two conservation agriculture and one conventionally ploughed treatment in four depth layers at Monze Farmer

Training Centre, November 2008–October 2010.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 251

compared to the conventional control, while yield in the directseeded sole maize treatment (DSM), with the exception of the firstcropping season, became only significant in the last two croppingseasons (Fig. 6). Highest increases in yield over the conventionalcontrol plot (CPM) were observed in 2005/06, 2007/08 and 2009/10 when yield in DSM-CT exceeded the control by 42%, 47% and56%, respectively. The highest increase of yield in DSM over CPMwas achieved in the sixth cropping season (+46%).

3.6. Comparative yield analysis

Treatment comparisons in all years (Fig. 7a and b) showed thatmost yields in Malende from both RIML and DSML were above the1:1 line, with a few cases over the 1:2 line. This means that, in mostcases, both CA treatments were better than the conventionalcontrol and in some cases yielded twice as much as CPML.Assessments of the comparative advantage over the years (Fig. 7c)show an increasing yield benefit from CA treatments over time.

After six cropping seasons, all CA treatments on all farms hadhigher yields than the conventional control treatment.

In Chipata, the yield comparison between the direct seededtreatments with sole maize (DISM) and the conventional systems(CRFM) were not as positive and were centred around the 1:1 line(Fig. 8a), with a few cases being higher. There were many cases ofunderperformance of the maize intercropped treatment (DISM/C)in comparison with the conventional control plot (Fig. 8b),suggesting a yield penalty from intercropping. As previously seenin the yield comparison, there were marked benefits of the fullrotation of up to more than double the yields in DISM-C comparedto CRFM (Fig. 8c). Yield advantages of DSM and DSM-C over theconventional control were obvious in all four seasons with theexception of a few cases where CA treatments had lower yieldsthan the conventional control.

At the Monze FTC, both DSM and DSM-CT generally performedbetter than the conventional control, and in some cases DSM-CTreached the 1:2 line (Fig. 9a and b) showing double the yield

Date

02/06

/08

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Agg

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ted

soil

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stur

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m)

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50

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110

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130

140

150

160

Aggregated soil moisture 0-40cmConventional ploughing, maize

Direct seeding, maizeDirect seeding, maize-cotton

Rainfall

Fig. 2. Aggregated soil moisture (0–40 cm soil depth) in two conservation agriculture and one conventionally ploughed treatment at Monze Farmer Training Centre,

November 2008–October 2010.

otal

car

bon

(Mg

ha-1

)

15

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25

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a

aa

b

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aa

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258252

achieved on the conventional control plot. There was no instancewhen the DSM-CT treatment at Monze was worse than CPM. Theanalysis also showed that there is an advantage to rotate maizecrops with cotton (Fig. 9c), as yield in most of the seasons washigher in this rotation system except for 2010/2011. Overall yieldgains over the control plot (in kg ha�1) showed strong yieldincreases in CA plots in all the seasons (Fig. 9d), apart from a fewinstances in 2006/07, 2007/08 and 2008/09 where slight yieldlosses occurred.

4. Discussion

Analyses of the performance of different CA systems showedthat infiltration and soil moisture was higher in CA plots comparedto conventionally ploughed plots. Roth et al. (1988) as well asThierfelder and Wall (2009) attributed this to the combined effectsof no-tillage and mulch retention which lead to high organicmatter in the soil. Mulch also impedes the evaporation of waterfrom the soil surface by protecting it from solar radiation and air

Table 5Total carbon measured at Monze Farmer Training Centre in conventional and

conservation agriculture cropping systems in October 2010.

Soil carbon (Mg ha�1)

0–10 cm 10–20 cm 20–30 cm

Conventional mouldboard

ploughing, maize

8.1 b 7.0 a 8.3 a

Direct seeding, maize 10.6 a 9.5 a 10.6 a

Direct seeding, maize-

cotton rotation

11.4 a 9.6 a 11.3 a

LSD 2.3 3.4 3.0

Note: means followed by the same letter in column are not significantly different at

P < 0.05 probability level, LSD test.

flow, which leads to an overall higher water content on mulchcovered fields (Adams, 1966; Dardanelli et al., 1994). Interestingly,differences in time-to-pond were observed in the on-farm sites,suggesting that although smaller amounts of residues wereretained on farmers’ CA fields, the combination of no-tillage andretention of part of the residues was sufficient to have an effect oninfiltration. Soil disturbance caused by tillage has a direct impact

Year

2004 2005 2006 2007 2008 2009 2010 2011

T

0

5

10

Conventional ploughing, maize (CPM )Direct seeding, maize (DSM)Direct seeding, cotton-maize (DSMC)

Fig. 3. Total carbon result in one conventionally ploughed and two conservation

agriculture treatments in 2005, 2008 and 2010, at Monze Farmer Training Centre,

Zambia. Error bars represent SEDs, means displaying different letters in column are

significantly different at P � 0.05 probability level.

Fig. 4. Maize grain yield in one conventional ridge and furrow system and two CA systems in Malende, Monze District, Zambia, 2006–2011. Error bars are SEDs in each

particular year.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 253

on infiltration. Although in the short term soil pores, especiallymacro-pores, temporarily increase through tillage, they willcollapse as soon as the soil settles. Tillage also replaces theexisting earthworm burrow network with less connected soilpores, which further limits infiltration. Once the soil is pulverizedand mixed in the top 10–15 cm, any exposure to the impact ofraindrops may lead to soil crusting and surface sealing, furtherimpeding rainfall infiltration. Mulch retention on the other handincrease biological activity (e.g. more earthworms) leading tobetter soil structure and macro-pores which facilitates higherinfiltration rates (Kladviko et al., 1986). CA systems show greatpotential to mitigate the effects of seasonal dry-spells, as moreinfiltration may lead to higher soil moisture availability for crops(Kassam et al., 2012; Thierfelder and Wall, 2010a).

Fig. 5. Maize grain yield in one conventional ridge and furrow system and three CA syst

particular year.

Clear trends in soil carbon improvements were established onlyat the on-station site; where residues were retained withoutinterference from fires or grazing animals. However Thierfelderand Wall (2012), found increases in carbon on sandy soils incommunal areas of Zimbabwe even where crop residue retentionwas challenging. Some of the crop residues retained at Monze FTCcontained more lignin (e.g. cotton residues) leading to a slowerdecomposition in comparison with leguminous crop residues on-farm (Rusinamhodzi et al., 2009).

Farmers in the on-farm sites mentioned crop residue retentionas well as weed control as their major challenge, confirmingprevious concerns highlighted by Giller et al. (2009), Gutoet al. (2012) and Baudron et al. (2012b). The loss of cropresidues through human interference, termites and possibly fast

ems in Kayowozi, Chipata District, Zambia, 2008–2011. Error bars are SEDs in each

Fig. 6. Maize grain yield in one conventionally ploughed and two CA systems at the Monze Farmer Training Centre, Zambia, 2005–2011. Error bars are SEDs in each particular

year.

Fig. 7. Yield comparison between the conventionally ploughed control and rip-line seeding (A) and animal traction direct seeding (B) and the comparative advantage (in

kg ha�1) of both CA treatments over the conventional control (C) from 2006 to 2011 at Malende, Monze District, Zambia.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258254

Fig. 8. Yield comparison between the conventional ridge and furrow system and direct seeding with a dibble stick with continuous maize (A), maize-cowpea intercropping (B)

and maize-cowpea rotation (C), as well as the yield advantage (in kg ha�1) of the CA treatment in maize-cotton rotation over the conventional control (D) from 2008 to 2011 at

Kayowozi, Chipata District, Zambia.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 255

decomposing leguminous residues, are all possible (Thierfelderand Wall, 2012) reasons for lack of significant carbon increase.Functional CA systems require the input of organic material tomaintain or increase carbon stocks (Corbeels et al., 2006) ratherthan an absence of tillage (Chivenge et al., 2007). Once residues aregrazed or burned, practising no-tillage will not contribute greatlyto soil fertility improvement and crop productivity (Albrecht et al.,1995). Soil carbon resulting from the metabolic activity ofmicrobes is stabilised in zero- or minimum-tillage systems dueto increased fungal-mediated improvement in soil structure andthe deposition of fungal-derived C macro-aggregates (Simpsonet al., 2004). Other studies suggest that for the first decades afterdegraded soils are converted to CA systems, soil C will at firstslowly increase over the first few years and finally averageapproximately 0.1% increase in C after ten years of CA in the soilprofile (Alvarez, 2005; West and Post, 2002).

On-station results at Monze FTC showed a gradual increase insoil carbon from 2005 to 2010 on the CA plots, whereas itdecreased in the conventional control plots. This is in agreementwith a modelling prediction which suggested that adopting zerotillage can lead to increases in carbon at a rate of0.04 Mg ha�1 year�1 (Farage et al., 2007).

It has often been highlighted that the organic matteraccumulation in CA systems only occurs within the first surfacecm of the soil (Giller et al., 2009) and should not significantly add tothe overall increase in carbon, in the soil profile. In contrast, in theploughed system soil is mixed, leading to smaller amounts of

carbon in the top layers in ploughed treatments (Baker et al., 2007;Giller et al., 2009; Luo et al., 2010). Ploughed treatments arecultivated up to a maximum soil depth of 10–25 cm only, and themixing effect of the plough should therefore only be considered upto a soil depth of 20–30 cm. Results at Monze FTC showed signs ofcarbon stratification between depth layers in 2010. However,comparing carbon in the top 30 cm as a whole showed that CAmaintained or increased higher amounts of carbon, whereascarbon decreased on the conventional treatment with tillage andno organic matter input. Excessive tillage in conventional plotsimproves aeration in the soil systems leading to higher oxidation oforganic matter (Alvear et al., 2005; Janzen, 2006). The highoxidation rate is beneficial in the short-term as they lead to morecrop nutrients being released. However, when all the abovegroundbiomass are exported (burned, grazed or removed) in theconventional system, then there is little organic matter availablefor any significant increases in carbon. In such scenarios, soildegradation characterised by soil nutrient mining and fertilitydecline are the consequences if no other organic sources, such aslarge amounts of manure, are available (Zingore et al., 2008).

Rotations played a significant role at Kayowozi and Monze FTC;at Malende the rotation effect could not be separated from theeffect of tillage. At both sites, yield from the CA treatment withrotation was largest in the long-term comparison. The combinationof a leguminous rotational crop (cowpea) with maize adds morenitrogen to the cropping systems (Giller, 2001), as seen atKayowozi, reduces pests and diseases such as striga (Striga asiatica

Fig. 9. Yield comparison between the conventionally ploughed control of two direct seeded CA treatments with continuous maize (A), a maize-cotton rotation (B), a

comparison between both CA treatments (C) and the yield advantage (in kg ha�1) of both CA treatments over the conventional control (C) from 2006 to 2011 at the Monze

Farmer Training Centre, Monze District, Zambia.

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258256

L.), a parasitic maize weed that is common in Chipata district, andpossibly improves soil structure. The maize-cotton rotation atMonze FTC, on the other hand, does not add any additionalnitrogen to the system, but the deep rooting cotton creates afavourable soil structure for the subsequent maize crop andcontributes to nutrient cycling in the rotation (Thierfelder andWall, 2010b). Our results suggest that all the principles of CAsystems should be practised if the best returns are to be obtainedfrom the cropping system. However, the profitability of the fullrotation has to be taken into account (Snapp et al., 2002).

Farmers in southern Africa, especially Malawi, have previouslyrejected the widespread adoption of rotational practices due to theperceived loss in land area dedicated to maize and theunavailability of suitable markets for the rotational crops (Snappet al., 2010). They resorted to intercropping maize with pigeonpeaand cowpea in order to benefit from both crops. The effectivenessof this strategy in controlling pests and diseases is uncertain. Ourresults from Kayowozi showed very strong competition betweenthe main crop and the intercropped cowpea. Other managementpractices, such as the application of residual herbicide to controlbroadleaved weeds, were not possible leading to increased weedpressure in this treatment, especially in the absence of completeyear-round weed control. As a result, maize yields in DISM/C weredepressed until the fourth cropping season, when they reached asimilar high amount to the direct seeded sole maize treatment.

The results at Malende point to a gradual yield increase in CAtreatments compared to the conventional cropping system over

time. There are various reasons for such improvements: (a)adjustment of the agricultural system to the new managementpractice (soil structure, fauna, carbon), which needs some time tomanifest; (b) nitrogen immobilisation in the earlier years due toresidue retention could lead to initial depression in yields; (c)accumulation of nutrients through carry-over of residues; (d) forbetter understanding and improved management, farmers requiretime to learn new practices such as direct seeding, residuemanagement and herbicide application for weed control, and oftenneed three to five years before they master the new technology; (e)the problem caused by a lack of the knowledge and capacitynecessary for extension workers to guide farmers in the rightdirection and the right methods in the early years of conversionfrom conventional to conservation agriculture (Bunderson et al.,2011; Wall, 2007; ZCATF, 2009). Farmers at our study sites mostlyappreciated the saving of labour time, especially when directseeding equipment and herbicides were used. However, the directseeder is only be an option for wealthier farmers until the cost ofdirect seeders, currently priced at approximately 600–650 US$, arereduced. Nevertheless, the less wealthy farmers will be able to usethe far cheaper ripper tines or dibble sticks to practice CA with littlepenalty in yield, as our results from Malende and Kayowozi clearlyshowed. Farmers can use the extra time saved for additionalincome generation e.g. for adding value to their own products (e.g.drying cowpea for making relish), for off-farm labour, producingadditional higher value crops in vegetable gardens or increasingthe cropped area; the extra time gained will therefore be beneficial

C. Thierfelder et al. / Soil & Tillage Research 126 (2013) 246–258 257

for the whole farm. In the long-term, the combination of the threecomponents of CA will lead to higher yields, as shown by ourresults from Kayowozi, Malende and Monze FTC.

5. Conclusion

Conservation agriculture systems as practised in Zambiagenerally lead to higher rainfall infiltration, soil moisture, agradual increase of soil carbon and improvements in crop yields incomparison with conventional systems over time. The effects of CAare expected to be significant where moisture and the productioncapacity of the soil are limiting factors. Our results point not only tothe importance of residues on CA fields but also to the contributionof crop rotation for the successful performance of CA systems.Economically sustainable agricultural systems also need to havedeveloped markets for produce to ensure CA systems can becomeprofitable. The results showed that increases in crop yields willtake between three to five seasons before they become significant.Labour savings will therefore be an entry point for farmers in theshort-term if direct seeding and herbicide technologies are used.The biggest challenge for farmers in the study sites, other than thecontrol of weeds, is the retention of sufficient crop residues. Manystrategies are still to be explored in overcoming this challenge inorder to adapt CA at the field, farm and community level. Weconclude that the benefits of CA can accrue on different soil typesand across different systems, but that scaling up and out requirestime and the whole community to be targeted, rather thanindividual farmers. Site-specific research is needed to address,understand and overcome these biophysical and socio-economicconstraints at all levels.

Acknowledgements

We wish to acknowledge the financial and logistical supportfrom the German Technical Cooperation (GIZ) and InternationalFund for Agriculture Development (IFAD) for funding projectactivities. Special thanks go to Kai Sonder who helped with the GISwork and Mwangala Sitali who led the research at the MonzeFarmer Training Centre. The authors also thank the farmers,extension officers, and field staff from the Ministry of Agricultureand Livestock, Department of Agriculture (DoA), and the ZambianAgriculture Research Institute (ZARI) for their enthusiasm,collaboration and support during the project implementationphase. The opinions expressed in this paper are those of theauthors.

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