Conservation agriculture (CA) can sustainably address soil degradation and improve crop yields. However, the success of CA amongst South African smallholder farmers is not known. The aims of the study were to find out: (1) the extent of CA practice by the Eastern Cape smallholder farmers; (2) perceptions towards CA amongst smallholder farmers with some history of practising the technology; and (3) the impact of practised CA components on soil quality indicators. Diagnostic survey techniques and soil sampling in farmers' fields were employed to gather data from five districts of the Eastern Cape, South Africa. The most common CA principle adopted by surveyed farmers was no-till (34.81%), whilst crop rotation and residue retention were practised by only 25.93% and 22.22% of the farmers, respectively. Education level and CA training influenced the likelihood of a farmer to practise no-till farming, whilst the likelihood of farmers to retain residues was influenced by education level and access to grazing lands. Lack of appropriate equipment and costly herbicides were the major constraining factors to practising CA. Crop residue retention conflicted with the common practice of free-range livestock grazing. Cabbage, maize and beans were the most common crops of choice for the few farmers that practised crop rotations. No significant (p > 0.05) improvement on soil quality indicators was observed with CA compared to the conventional farming method. The noted high dependency on government grants by the smallholder farmers could be a disincentive towards the adoption of agricultural innovations such as CA. Identification of practical key CA entry points is recommended, bearing in mind the noted impediments to CA adoption.
The effects of tillage and crop rotation on the soil carbon, the soil bulk density, the porosity and the soil water content were evaluated during the 6<sup>th</sup> season of an on-going field trial at the University of Fort Hare Farm (UFH), South Africa. Two tillage systems; conventional tillage (CT) and no-till and crop rotations; maize (Zea mays L.)-fallow-maize (MFM), maize-fallow-soybean (Glycine max L.) (MFS); maize-wheat (Triticum aestivum L.)-maize (MWM) and maize-wheat-soybean (MWS) were evaluated. The field experiment was a 2 × 4 factorial, laid out in a randomised complete design. The crop residues were retained for the no-till plots and incorporated for the CT plots, after each cropping season. No significant effects (P > 0.05) of the tillage and crop rotation on the bulk density were observed. However, the values ranged from 1.32 to1.37 g/cm<sup>3</sup>. Significant interaction effects of the tillage and crop rotation were observed on the soil porosity (P < 0.01) and the soil water content (P < 0.05). The porosity for the MFM and the MWS, was higher under the CT whereas for the MWM and the MWS, it was higher under the no-till. However, the greatest porosity was under the MWS. Whilst the no-till significantly increased (P < 0.05) the soil water content compared to the CT; the greatest soil water content was observed when the no-till was combined with the MWM rotations. The soil organic carbon (SOC) was increased more (P < 0.05) by the no-till than the CT, and the MFM consistently had the least SOC compared with the rest of the crop rotations, at all the sampling depths (0–5, 5–10 and 10–20 cm). The soil bulk density negatively correlated with the soil porosity and the soil water content, whereas the porosity positively correlated with the soil water content. The study concluded that the crop rotations, the MWM and the MWS under the no-till coupled with the residue retention improved the soil porosity and the soil water content levels the most.
Plant and Soil 2012, 29(3&4): 135-141 Printed in South Africa -All rights reserved The Eastern Cape (EC) is one of South Africa's provinces worst affected by soil degradation (Fox and Rowntree 2001, Fatunbi andDube 2008). Poor agricultural practices leave the soil without cover, promoting erosion and loss of nutrient-rich soil particles leading to reduced soil productivity (Laker 2004). In order to increase and stabilise soil productivity, control of soil erosion is essential. One key principle of conservation agriculture (CA) is permanent soil cover, a potential solution to the problem of soil degradation observed in the EC. The proponents of CA suggest the use of cover crops, grown in rotation or intercropped with the main crop, as a way of providing permanent soil cover, increasing aggregate stability and eventually reducing erosion.Cover crops provide several other advantages besides reduction of soil erosion. Some that are cited in the literature include weed suppression, mining of leached nutrients, improved soil organic matter, nitrogen (N) fixation and general improvement in soil fertility (Derpsch 2008). However, no single cover crop species can achieve all these benefits on its own. Production of two cover crop species together, usually a legume and a grass, known as biculturing, offers an option that can deliver diverse benefits Differences have been noted among cover-crop species regarding their growth rate, amount of biomass accumulation, weed suppression and nutrient uptake. Grasses germinate earlier and develop root systems at a faster rate than legumes (Ranells and Wagger 1996), hence may have more effective early season weed control. They also potentially contribute to increases in soil organic matter by supplying higher levels of carbon (C) (Odhiambo and Bomke 2001, Lithourgidis et al. 2006). However, grasses have been observed to provide little N for growth of the follow-on crop and are less economical as they require large amounts of N fertiliser to attain acceptable biomass compared to legumes (Murungu et al. 2010).Conversely, legume species biologically fix N, increasing soil N levels and resulting in yield increases for subsequent crops when N is the limiting factor (Kuo et al. 1996, Crandall et al. 2005. In temperate and tropical environments, vetch (Vicia sativa L.) can accumulate 150-250 kg N ha −1 , replacing about two-thirds of N required for maize (Zea mays L.) production (Crandall et al. 2005). Although both grazing vetch and white oat (Avena sativa L.) can symbiotically interact with arbuscular mycorrhizal fungi, increasing phosphorus (P) uptake, legumes decompose Biomass production, weed suppression, nitrogen and phosphorus uptake in white oat (Avena sativa L.) and grazing vetch (Vicia dasycarpa L.) cover crop bicultures under an irrigated no-till system L Muzangwa 1 , C Chiduza 2 * and P Muchaonyerwa 3 Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa * Corresponding author, Cultivation of a multipurpose cover crop is of interest to Eastern Cape farmers ex...
Earthworms play a pivotal role in the regulation of soil health. Studies that explore the effects of conservation agriculture (CA) principles on earthworms under the semi-arid climate of the central Eastern Cape (EC) of South Africa (SA) are limited. Therefore, this study investigated the effects of tillage, crop rotations, and residue management on earthworms’ abundance and species richness. The study design followed a split-split plot with three replicates. The main plot was allocated to tillage treatment, which had conventional tillage (CT) and no-tillage (no-till) as factors. Crop rotation treatment was allocated to a subplot, and had maize (Zea mays)–fallow–maize (MFM), maize–fallow–soybean (Glycine max) (MFS), maize–wheat (Triticum aestivum)–maize (MWM), and maize–wheat–soybean (MWS). Residue management was in the sub-subplot with residue retention and residue removal. The study was carried out over four cropping seasons: summer 2015–2016, winter 2016, spring 2016, and summer 2016–2017. The results showed that the genera Amynthas and Lumbricus, both belonging to the anecic group, and Dendrobaena, belonging to the epigeic group, were present. Earthworm species diversity and density were highest under no-till than under CT. Residue retention improved earthworm density regardless of tillage management. Rotations that had fallow periods recorded lower earthworm numbers as compared to continuous cropping systems where wheat was grown in winter. The study concluded that maize–wheat–soybean (MWS) rotation with residue retention results in the highest earthworm abundance and species richness.
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