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

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<ul><li><p>ot</p><p> R</p><p>isio</p><p>Soil &amp; Tillage Research 126 (2013) 246258</p><p>Contents lists available at SciVerse ScienceDirect</p><p>Soil &amp; Tillag</p><p>.e1. Introduction</p><p>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).</p><p>Since the 1990s, environmentally sustainable agriculturesystems that improve soil fertility and production capacity haveincreasingly gained attention in research and extension services</p><p>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 exible agricultural systemthat can be widely adapted to local site conditions (Wall, 2007).On the other hand, CA is not a xed recipe, blanketrecommendation or panacea, and there is therefore a need totake into account the conditions and socio-economic constraintsof farmers.</p><p>A R T I C L E I N F O</p><p>Article history:</p><p>Received 9 May 2012</p><p>Received in revised form 8 September 2012</p><p>Accepted 11 September 2012</p><p>Keywords:</p><p>Conservation agriculture</p><p>Direct seeding</p><p>Sustainable land management</p><p>Mulching</p><p>Rotations</p><p>Soil conservation</p><p>A B S T R A C T</p><p>Sustainable and resilient cropping systems are required in southern Africa to arrest declining soil fertility</p><p>and offset the future negative effects of climate change. Conservation agriculture (CA) has been proposed</p><p>as a potential system for improving soil quality and providing stable yields through minimum soil</p><p>disturbance, surface crop residue retention (mulching) and crop rotations or associations. However,</p><p>concerns have been raised about the lack of evidence of the benets of CA for small-scale farmers in</p><p>southern Africa. This research was carried out in two communities and one on-station site in Zambia to</p><p>provide more scientic evidence about the effects of CA on soil quality, inltration, soil moisture and</p><p>crop performance. Results from Kayowozi showed that maize yields in a direct seeded CA treatment,</p><p>using cowpea seeded with a dibble stick in full rotation, increased by up to 78% after four cropping</p><p>seasons in comparison to a conventional control using a ridge and furrow system. At Malende, maize</p><p>yields for animal traction rip-line seeded and direct seeded plots were, on average, 75% and 91% higher</p><p>than a conventionally tilled control plot after six cropping seasons. Detailed studies undertaken at the</p><p>Monze Farmer Training Centre revealed that CA treatments, especially that using cotton in rotation,</p><p>increased water inltration and soil moisture. In some years, inltration was ve times higher on CA</p><p>elds than on those using conventional tillage. Carbon increases were only found at the on-station long-</p><p>term trial, where, over time, CA plots outperformed conventional practice leading to an overall increase</p><p>of 12% carbon in the rst 30 cm, compared with decreases of 15% in the conventional control.</p><p>Comparative analyses between the on-farm and on-station trials point to a lack of adequate mulching,</p><p>which might be the reason for lower carbon at the on-farm sites. We conclude that the effects of CA can</p><p>build up on different soil types in most systems, but that scaling up and out requires the whole</p><p>community to be targeted, rather than relying on individual farmers to overcome constraints related to</p><p>the set-up in rural communities.</p><p> 2012 Elsevier B.V. All rights reserved.</p><p>* Corresponding author. Tel.: +263 772815230.</p><p>E-mail address: c.thierfelder@cgiar.org (C. Thierfelder).</p><p>0167-1987/$ see front matter 2012 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.still.2012.09.002Conservation agriculture in eastern and seffects on soil quality and maize produc</p><p>Christian Thierfelder a,*, Mulundu Mwila b, Leonarda CIMMYT, P.O. Box MP 163, Mount Pleasant, Harare, Zimbabweb Zambia Agriculture Research Institute (ZARI), Farming Systems and Social Sciences Div</p><p>jou r nal h o mep age: w wwuthern provinces of Zambia: Long-termivity</p><p>usinamhodzi a</p><p>n, P.O. Box 510089, Chipata, Zambia</p><p>e Research</p><p>l s evier . co m/lo c ate /s t i l l</p></li><li><p>C. Thierfelder et al. / Soil &amp; Tillage Research 126 (2013) 246258 247Farmers in southern Africa rely on maize (Zea mays L.) as themain staple food crop: it accounts for 5090% 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 croplivestock 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 difcult to retain enough residues (Thierfelderand Wall, 2012). As a result, the soil surface in maize elds is oftenuncovered and, when exposed to heavy rainfall, build up surfaceseals and crusts which reduces rainfall inltration leading to moresurface run-off and soil erosion (Derpsch et al., 1986; Roth et al.,1988; Thierfelder et al., 2005; Thierfelder and Wall, 2009).Insufcient 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).</p><p>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 Magoyefurrow 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).</p><p>CA has potential to improve water inltration 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. Benets 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 specic 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 benets and challenges of various CA systemsand 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 nancial access to inputs,land tenure, knowledge gaps and mindset) highlighted by Wall(2007).</p><p>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, inltration, 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.</p><p>2. Materials and methods</p><p>2.1. Study area</p><p>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 rst 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 wherespecically chosen because CA was promoted there since 2005(Monze) and 2007 (Chipata).</p><p>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.</p><p>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).</p><p>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 4050 cm soil depth to form sandy clay loamand sandy clay. The mean long-term rainfall is 748 mm a1 and thenatural vegetation is dry Savanna.</p><p>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 a1 of annual rainfall. Major crops in theEastern Province are maize, cotton and some grain legumes(cowpeas, common beans and groundnuts).</p><p>2.2. Experimental design</p><p>At both on-farm sites the study was conducted on farmerselds with a total of six farmers hosting replicates of a validation</p></li><li><p>Table 1Some soil properties of reference prole D, ferric Lixisol, Monze Farmer Training Centre (FTC), and two farmers elds in Malende (K. Mwemba) and Kayowozi (B. Phiri),</p><p>Zambia.</p><p>Horizons Depth [cm] Bulk density [g cm3] Mottling [vol%] pH [CaCl] CEC [cmol kg1] C [%] Particle size [%]</p><p>Sand Silt Clay</p><p>Monze FTCAp 021 1.56 4.8 2.8 0.60 82 6 12</p><p>AB 52 1.55 2 4.8 5.2 0.52 55 8 37Btg 100 1.33 15 5.2 5.1 0.40 53 8 39BCcg &gt;105 1.45 &gt;40 5.8 5.5 0.17 71 6 23</p><p>Malende010 1.25 5.0 8.0 0.97 90 8 2</p><p>20 1.33 5.0 8.3 0.90 78 2 2030 1.36 5.0 9.2 0.87 70 10 2060 1.36 N/A 5.1 9.1 0.86 78 7 15</p><p>Kayowozi010 1.32 6.1 9.7 0.94 77 13 10</p><p>20 1.34 6.2 10.3 0.86 84 6 1030 1.39 6.0 10.1 0.81 78 10 1260 1.52 N/A 5.9 7.4 0.51 76 7 17</p><p>C. Thierfelder et al. / Soil &amp; Tillage Research 126 (2013) 246258248trial 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:</p><p>1. Conventional control plot consisting of mouldboard ploughingand maize planted with a maize-legume rotation (CPML).Ploughing was done at shallow depth (1015 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.</p><p>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).</p><p>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 57 cm deep and 5 cmwide. Crop residues were retained as surface mulch, as in RIML.Table 2Amount of biomass retained on...</p></li></ul>

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