Effects Of Conservation Agriculture Research Articles

Long and Midterm Effect of Conservation Agriculture on Soil Properties in Dry Areas of Morocco

In Morocco, conservation agriculture, particularly no tillage systems, has become an alternative strategy to mitigate land degradation caused by conventional tillage in semiarid to arid regions. This paper is based on behaviour to tillage treatments of two Vertisols in Morocco. After 11 years of testing, soil organic matter content results showed a significant difference (P<0.05) only at soil surface (0–10 cm) in favour of no tillage and a variation of 30% at this depth. The results obtained after 32 years of testing showed a significant soil profile difference (P<0.05), up to 40 cm under no tillage compared to conventional tillage, and a variation of 54% at 5–10 cm. For total nitrogen, there was no significant effect between no tillage and conventional tillage at the soil surface after 11 years unlike the result obtained after 32 years. There are no significant differences in bulk density between tillage treatments at soil surface for both sites. The measurement of soil structural stability showed a significant effect (P<0.05) for all three tests and for both sites. This means that no tillage helped Vertisols to resist different climatic constraints, preserving environmental soil quality.

Maize yield effects of conservation agriculture based maize–legume cropping systems in contrasting agro-ecologies of Malawi and Mozambique

Sustainable intensification cropping systems involving improved maize and legume seeds and conservation agriculture (CA) are potential avenues towards improved productivity. This study evaluated CA based cropping systems effects on maize yields with respect to herbicide use, crop establishment techniques and legume rotations in four contrasting agro-ecologies of Malawi and Mozambique from 2010/11 to 2013/14. No significant (p > 0.05) yield differences, at 4100 versus 3900 kg ha−1 were observed in Malawi when CA was implemented with and without herbicides respectively, suggesting herbicides were not a precondition for CA’s success. CA basins depressed maize yields by 3 % in north-western Mozambique and also offered no advantages in Malawi’s lowland districts (Ntcheu and Salima). In contrast, significant yield gains (p < 0.05) emerged from dry Balaka (<600 mm year−1) with mean yields of 2400 from the CA basins compared to 1800 kg ha−1 from farmer practices, an effect also confirmed by the yield stability analysis showing CA basins superiority in unfavourable rainfall environments. Thus CA basins performance was site dependent with no benefits on waterlogged soils or high rainfall conditions where direct seeded dibble stick or jab planting provided a better crop establishment option. Across all agro-ecologies, soyabeans, cowpea and groundnuts rotation systems, significantly increased maize yield, amounting to 20, 38 and 54 % respectively, except for the maize–common bean rotations in north-western Mozambique, which failed to offer any yield advantages. Probabilities of achieving higher CA yield ranged from 58 to 71 %. The study suggests CA based cropping systems offer an opportunity for intensifying maize production in the region.

Conservation agriculture effects on soil organic carbon accumulation and crop productivity under a rice–wheat cropping system in the western Indo-Gangetic Plains

Retention of carbon (C) in arable soils has been considered as a potential mechanism to mitigate soil degradation and to sustain crop productivity. Hence, we appraised the 3-year effect of different conservation agriculture (CA) practices on grain yield, biomass productivity and soil organic C (SOC) accumulation rates under a tropical rice (Oryza sativa L.)-wheat (Triticum aestivum L.) and rice–wheat–green gram (mungbean in Hindi; Vigna radiata) cropping systems. Results indicate mean (of three years) rice grain yield under mungbean residue+direct seeded rice (DSR) followed by zero tilled wheat (ZTW) with rice residue (RR) retention and zero tilled relay summer mungbean (MBR+DSR-ZTW+RR-ZTMB) plots was similar to farmers’ practice [transplanted rice (TPR)- conventionally tilled wheat (CTW)], despite TPR-CTW plots had ∼18% higher rice yield than MBR+DSR-ZTW+RR-ZTMB plots in the first year. The MBR+DSR-ZTW+RR-ZTMB treated plots had about 15 and 10% higher mean wheat grain yield and mean system productivity (sum of grain yields of all crops) than TPR-CTW plots, respectively. The plots under DSR+brown manuring (BM)-ZTW+RR plots had comparable mean rice and wheat yields to MBR+DSR- ZTW+RR-ZTMB plots. Harvestable aboveground biomass productivity of MBR+DSR-ZTW+RR-ZTMB treated plots was ∼2.89Mgha−1yr−1 higher than TPR-CTW. Total estimated C input (∼12.1MgCha−1 in three years) under MBR +DSR-ZTW+RR-ZTMB treated plots was ∼117 and 127% higher than DSR-ZTW and TPR-CTW treatments, respectively. All CA plots had significantly higher gain (over initial value) in total SOC than that in TPR-CTW and TPR-ZTW treatments in the 0–15cm layer and the gain in total SOC in the plots under MBR+DSR- ZTW+RR-ZTMB was significantly higher than all CA plots, despite having similar total SOC stocks. Again, plots under MBR+DSR-ZTW+RR-ZTMB had ∼24% larger labile C pools than that of TPR-CTW (3.1gkg−1) treated plots in the topsoil. Soil bulk density under MBR+DSR- ZTW+RR-ZTMB and DSR+BM-ZTW+RR treated plots significantly decreased in the 5–15cm layer compared to TPR-CTW plots. Thus, the MBR+DSR-ZTW+RR-ZTMB treatment (a novel CA practice), has considerable potential to retain C in surface soil, decrease soil compaction and increase system (rice–wheat–green gram) productivity and hence its adoption is recommended.

Effects of Conservation Agriculture and Fertilization on Soil Microbial Diversity and Activity

Soil microbial communities perform critical functions in ecosystem processes. These functions can be used to assess the impact of agricultural practices on sustainable crop production. In this five-year study, the effect of various agricultural practices on soil microbial diversity and activity was investigated in a summer rainfall area under South African dryland conditions. Microbial diversity and activity were measured in the 0–15 cm layer of a field trial consisting of two fertilizer levels, three cropping systems, and two tillage systems. Using the Shannon–Weaver and Evenness diversity indices, soil microbial species richness and abundance were measured. Microbial enzymatic activities: β-glucosidase, phosphatase and urease, were used to evaluate ecosystem functioning. Cluster analysis revealed a shift in soil microbial community diversity and activity over time. Microbial diversity and activity were higher under no-till than conventional tillage. Fertilizer levels seemed to play a minor role in determining microbial diversity and activity, whereas the cropping systems played a more important role in determining the activity of soil microbial communities. Conservation agriculture yielded the highest soil microbial diversity and activity in diversified cropping systems under no-till.

Conservation agriculture and performance of farms in West Africa

In West Africa, conservation agriculture can contribute to achieving ecological intensification of farming systems if research produces more references on its effects at the farm level. This study conducted in Burkina Faso assesses ex ante the effects of conservation agriculture on the performance of virtual farms representing the different types identified in the area. Two whole-farm simulation tools were used: Cikeda and Olympe. The effects of applying conservation agriculture on 50% of the cereal area were simulated for income, cereal and fodder balances and labour. Simulations show that conservation agriculture has positive effects on income and the fodder balance, but it increases the demand for labour. For producers, adopting conservation agriculture is a means of engaging their farms in an evolution pathway, for example through the development of livestock activities. The introduction of cattle fattening can therefore trigger investment in conservation agriculture for farms with a stocking rate lower than 1.5 animal per ha. There is also, however, a need to develop collective organizational innovations, particularly for the management of crop residues.

Castor [Ricinus communis (L.)]-Sorghum [Sorghum bicolor (L.)] Cropping System Productivity, Soil Chemical and Biological Fertility in Response to Conservation Agriculture and Nutrient Management Practices in Alfisols

A fixed plot experiment was conducted in Alfisols for three years from 2010 to 2012 at Narkhoda farm of Directorate of Oilseeds Research, Hyderabad. The main objective of the study was to know the effect of conservation agriculture (minimum tillage, crop residue and cover crop) and nutrient management practices (recommended dose of fertilizers, integrated nutrient management, organic nutrient management, fertilizers based on soil test crop response and customized fertilizers) on the productivity, nutrient uptake and soil chemical and biological fertility in castor-sorghum cropping system under rainfed conditions. Conservation agriculture was found to be on par with conventional agriculture with reference to system productivity, system nutrient uptake and soil chemical and biological fertility. Among nutrient management practices, fertilizer application based on soil test crop response (STCR) significantly improved the system productivity (2717 kg/ha), system nutrient uptake (188-62-198 N: P2O5: K2O kg/ha) and soil nutrient availability (224-30-430 N: P2O5: K2O kg/ha) which was on par with customized fertilizer. The productivity improvement with these set of treatments was 15% higher compared to that of recommended dose of fertilizer (RDF). Soil respiration (290 mg kg/d), microbial biomass C (320 mg/kg) and N (48.5 mg/kg) were significantly increased with organic nutrient management followed by integrated nutrient management.

Whole-farm economic and risk effects of conservation agriculture in a crop-livestock system in western China

Researchers advocate using conservation agriculture as a tool to improve farmer livelihoods, with crop residue retention being an integral component of conservation agriculture. Crop residues are used for mulch, livestock feed, and fuel material in crop-livestock farming systems. In this article, we conducted long-term simulation modelling to compare the economic effects of different crop residue retention practices for a crop-livestock agricultural household in semi-arid China. We calculated the average profit and net present value (and associated variability) of different crop residue retention practices using planning horizons of 3, 6, 10, and 20 years. Crop residue retention increased grain production, reduced forage production leading to smaller livestock flock sizes, and increased family heating and cooking costs. The net effect was that retaining minimal crop residues gave the highest profits using the three year planning horizon.Full crop residue retention provided the highest profit when the planning horizon exceeded 10 years. Relatively flat economic payoffs associated with changing crop residue usage around the maximum economic payoff existed. Calls for comprehensive crop residue retention are unlikely to be attractive when farmers discount future profits, and when crop residues have significant value as a fuel and feed source. The economic benefits of crop residue retention can take numerous years to eventuate and retaining crop residues also increased simulated ground cover and this positive environmental impact extends beyond individual farm boundaries. Because of these time lags and external environmental benefits, providing financial incentives to retain crop residues during the initial transition years could be a policy option.

Soil properties after change to conservation agriculture from ridge tillage in sandy clay loams of mid‐altitude Central Malawi

AbstractA comparative study was carried out of annual ridge tillage (RT) and short‐term effects of conservation agriculture (CA) on soil properties in fields of small‐scale farmers. Soil samples were collected at depths of 0–10 and 10–20 cm from a total of 12 fields which had been under CA for two and four seasons, respectively, and from adjacent RT fields for direct comparisons. CA fields were converted from fields previously under continuous RT. Soil organic carbon, total nitrogen and available phosphorus were greater in CA fields while extractable potassium, pH and salt content were moderated under CA. Conversion of long‐term RT to CA did not significantly influence bulk density and aggregate stability (geometric mean diameter) although structural stability was greater under CA practices. Total porosity, macroporosity and matrix porosity, and volumetric water content at saturation, field capacity and permanent wilting point did not substantively respond to tillage effects. Relative water capacity and air–water storage parameter, θfc/PORt, were significantly greater after 4 yr of CA. Soils under CA showed greater values for field‐saturated hydraulic conductivity compared with RT fields. With the highest loadings in a principal component analysis, this work suggests that variables related to volumetric water content and aeration of the soil matrix, organic carbon, available phosphorus and soil texture were the most useful indices for future field comparison of RT and CA practices.

Fourteen years of evidence for positive effects of conservation agriculture and organic farming on soil life

Conventional agriculture strongly alters soil quality due to industrial practices that often have negative effects on soil life. Alternative systems such as conservation agriculture and organic farming could restore better conditions for soil organisms. Improving soil life should in turn improve soil quality and farming sustainability. Here, we have compared for the first time the long-term effects of conservation agriculture, organic farming, and conventional agriculture on major soil organisms such as microbes, nematofauna, and macrofauna. We have also analyzed functional groups. Soils were sampled at the 14-year-old experimental site of La Cage, near Versailles, France. The microbial community was analyzed using molecular biology techniques. Nematofauna and macrofauna were analyzed and classified into functional groups. Our results show that both conservation and organic systems increased the abundance and biomass of all soil organisms, except predaceous nematodes. For example, macrofauna increased from 100 to 2,500 %, nematodes from 100 to 700 %, and microorganisms from 30 to 70 %. Conservation agriculture showed a higher overall improvement than organic farming. Conservation agriculture increased the number of many organisms such as bacteria, fungi, anecic earthworms, and phytophagous and rhizophagous arthropods. Organic farming improved mainly the bacterial pathway of the soil food web and endogeic and anecic earthworms. Overall, our study shows that long-term, no-tillage, and cover crops are better for soil biota than periodic legume green manures, pesticides, and mineral fertilizers.

Effect of Conservation Agriculture on Maize-based Farming System in the Mid-hills of Nepal

Conservation agriculture (CA) systems composed of intercropping and strip tillage practices were evaluated on marginalized maize-based farming system in hill region of Nepal. On-farm experimental trials were conducted on the field of 25 smallholder farmers in three villages of central mid-hill region. Results indicated that although CA systems did not increase crop yields; higher return and revenue were generated due to increased number of crop harvests and higher price of the cash crops used in intercropping. Therefore, it was concluded that smallholder farmers should adopt CA system for increasing return and improving sustainability of the farming system.

Assessing the Effects of Conservation Agriculture on Maize Yield in Nyakatsapa, Mutasa District, Manicaland Province: Implications on Extension Advice to Farmers in Promoting the Agriculture

Assessing the Effects of Conservation Agriculture on Maize Yield in Nyakatsapa, Mutasa District, Manicaland Province: Implications on Extension Advice to Farmers in Promoting the Agriculture

Conservation agriculture effects on plant nutrients and maize grain yield after four years of maize–winter cover crop rotations

The effects of maize rotation with oat (Avena sativa cv. Sederberg) and grazing vetch (Vicia dasycarpa cv. Max) winter cover crops on nutrient availability, maize grain yield and maize grain nutrient concentration were investigated. Soil samples were collected from the 0–5 and 5–20 cm depths of experimental plots after four years of continuous maize–winter cover crop rotations. Winter cover crops caused small increases of extractable soil Cu, Mn, P and Zn, but not Ca and K, concentrations. A small dose of fertiliser applied to maize (60, 30, 40 and 1.5 kg ha−1 of N, P, K and Zn, respectively) also caused a significant increase in P and Zn, as well as mineral N, concentrations but only in the vetch–maize rotations. Stratification of Mn, K and Zn in the 0–5 cm soil depth occurred in all treatments. Vetch additionally increased maize grain yield, grain N concentration and soil acidity more than either oat or fallow. Non-fertilisation of maize reduced maize grain yield on oat and fallow–maize rotations more than it did on vetch–maize rotations. A combined application of vetch winter cover crops and small doses of fertiliser could significantly improve sustainability of low input maize-based conservation agriculture systems.

Reversing Agro-Based Land Degradation through Conservation Agriculture: Emerging Experiences from Zambia’s Smallholder Farming Sector

&lt;p&gt;This study reports on the land degradation minimizing effects of Conservation Agriculture (CA) as promoted among smallholder Zambian farmers. It found no evidence of CA associated improvements in soil fertility after five years of CA practice, most probably because crop residues were removed from the fields. The study reports high phosphorus (15.53 mg kg&lt;sup&gt;-1&lt;/sup&gt;) and potassium (0.75 cmol kg&lt;sup&gt;-1&lt;/sup&gt;) levels, low nitrogen (0.12 %) and organic carbon (1.19 %) levels, and no plough/hoe pans in soils from both CA and conventionally (CV) managed fields. This is in part contrary to the dominant land degradation narratives which have been the basis for promoting CA in the study areas. &lt;em&gt;Faidherbia albida&lt;/em&gt;, a leguminous tree promoted as part of the CA package in Zambia, is associated with significantly higher levels of nitrogen, organic carbon and potassium under its canopy. Its planting by CA farmers is linked to the incentives provided by CA promoters. Average maize yields of 3.8 t ha&lt;sup&gt;-1&lt;/sup&gt; and 2.8 t ha&lt;sup&gt;-1 &lt;/sup&gt;were reported under CA and CV systems respectively. Government subsidies for mineral fertilizer and hybrid seed promote maize mono-cropping and remain unsupportive of CA. It is concluded that the dominant land degradation narrative, which posits population induced land degradation, may not hold in this case. Instead, the removal of crop residues and low levels of mineral fertilizer and manure amendments may better explain the soil fertility status of the study areas. More nutrient replacement strategies are required if the benefits of CA on soil fertility are to be actualized in the immediate future.&lt;/p&gt;

Effects of conservation agriculture on soil quality and productivity in contrasting agro‐ecological environments of Zimbabwe

AbstractExperimentation by farmers with conservation agriculture (CA) is increasing in southern Africa, but local longer term data on these new production systems are scarce. This study focuses on CA research at two contrasting on‐farm sites and one on‐station long‐term trial in Zimbabwe. The on‐farm trials were conducted at Chikato village on a sandy soil at Zimuto Communal Area with low rainfall and at Hereford farm near Bindura on a clay‐rich soil in a high rainfall area. The on‐station trial was at Henderson Research Station near Mazowe where more in‐depth soil studies were possible. Results of CA systems from the on‐station site show on average 38 and 65% greater water infiltration on ripline‐seeded (RS) and direct‐seeded CA treatments compared with conventionally ploughed control treatments. Results from on‐farm sites show a 123 and 168% greater aggregate stability at Hereford and 11 and 24% lower dispersion ratio at Chikato on the two CA compared with the conventionally ploughed control treatments. Soil carbon increased by 46% in the first 20 cm on the sandy soils at Chikato in RS and by 104% in direct‐seeded CA treatments in four cropping seasons from 2004 to 2008, while it stayed at low levels on the conventionally tilled control treatment. Yields on CA plots were higher on the sandy soils in dry seasons, but lower in very wet seasons because of waterlogging. Yields on clay soils were less affected by the rainfall season. Crop productivity from CA systems increased at all sites over time owing to better management although significant differences between CA and conventional treatments on the three sites were apparent only after several cropping seasons. Conservation agriculture offers practical solutions to small‐scale farmers threatened by future soil degradation and fertility loss, but its successful use will depend on weed control and adequate application of fertilizers. The results indicate that there is no immediate increase in maize (Zea mays L.) yield when changing from a tilled to a CA system, but there is gradual improvement in some soil quality indicators over time.

Conservation agriculture effects on soil organic matter on a Haplic Cambisol after four years of maize–oat and maize–grazing vetch rotations in South Africa

A study was conducted to determine the effects of oat (Avena sativa) and grazing vetch (Vicia dasycapa) winter cover crops and fertilization regimes on soil organic matter (SOM) in an irrigated maize-based (Zea mays L.) conservation agriculture (CA) system following four years of continuous practice. Separate plots of oat and grazing vetch cover crops were grown in winter and then maize was planted in all plots in the following summer season. The four fertilization regimes used were: (i) fertilizer applied to the cover crops and the maize crop (F1), (ii) fertilizer applied to cover crops only (F2), (iii) fertilizer applied to the maize crop only (F3) and (iv) no fertilizer applied (F4). Control plots (weedy fallows) were included and the treatments were laid out in a randomized complete block design with three replications. Soil samples from 0–5, 5–20 and 20–50cm depths were analyzed for total SOM, particulate organic matter (POM) fractions, hot water soluble C (HWC) and C-associated with water stable macro- and micro-aggregates (WSAC). While total SOM was more concentrated in the 0–5cm soil depth across treatments, a lack of maize fertilization (F2 and F4 regimes) significantly (P<0.05) reduced the stratification ratio. Oat and grazing vetch rotations produced significantly higher (P<0.05) fine POM, coarse POM and HWC than weedy fallow rotations at 0–5 and 5–20cm. When fertilized, oat was better able to support SOM sequestration in water stable aggregates at 0–20cm while grazing vetch was more effective at 20–50cm. The F3 regime had similar SOM levels as the F2. When no fertilizer was applied (F4-regime), there were significant (P<0.01) reductions in biomass input and total SOM on the oat–maize and weedy fallow–maize rotations whereas the grazing vetch–maize rotation did not respond, both at 0–5 and 5–20cm. The findings suggested that in the low fertilizer input CA system, targeting fertilizer to the winter cover crop as opposed to the maize crop could give similar SOM response, with less fertilizer invested and that grazing vetch cover crops may be better suited to low N input CA systems for SOM improvement.

Use of the swat model for hydro-sedimentologic simulation in a small rural watershed

Mathematical models have great potential to support land use planning, with the goal of improving water and land quality. Before using a model, however, the model must demonstrate that it can correctly simulate the hydrological and erosive processes of a given site. The SWAT model (Soil and Water Assessment Tool) was developed in the United States to evaluate the effects of conservation agriculture on hydrological processes and water quality at the watershed scale. This model was initially proposed for use without calibration, which would eliminate the need for measured hydro-sedimentologic data. In this study, the SWAT model was evaluated in a small rural watershed (1.19 km²) located on the basalt slopes of the state of Rio Grande do Sul in southern Brazil, where farmers have been using cover crops associated with minimum tillage to control soil erosion. Values simulated by the model were compared with measured hydro-sedimentological data. Results for surface and total runoff on a daily basis were considered unsatisfactory (Nash-Sutcliffe efficiency coefficient - NSE &lt; 0.5). However simulation results on monthly and annual scales were significantly better. With regard to the erosion process, the simulated sediment yields for all years of the study were unsatisfactory in comparison with the observed values on a daily and monthly basis (NSE values &lt; -6), and overestimated the annual sediment yield by more than 100 %.

On-farm evaluation of yield and economic benefit of short term maize legume intercropping systems under conservation agriculture in Malawi

Low crop yields due to continuous monocropping and deteriorating soil health in smallholder farmers’ fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. The aim of the study was to elucidate the short term effects of conservation agriculture (CA) systems on soil quality, crop productivity and profitability. In Balaka market and Ntonda sections of Manjawira Extension Planning Area (EPA), in Ntcheu district, central Malawi, we compared continuous monocropped maize (Zea mays) under conventional tillage practice (CP) with different CA systems in continuous monocropped maize (CAM) and intercropping with pigeonpea (Cajanus cajan) (CAMP), Mucuna pruriens (CAMM), and Lablab purpureus (L.) (Sweet) (CAML). The study was conducted from 2008 to 2011 in 72 plots in 24 farmers’ fields. In Balaka market section CA plots with maize+legumes produced up to 4.3Mgha−1 of vegetative biomass against 3.5Mgha−1 for maize alone in CP. In Ntonda section CA plots with maize+legumes produced up to 4.6Mgha−1 of vegetative biomass against 2.4Mgha−1 for maize alone in CP. In both sections, during the entire study period, CA did not have a negative effect on crop yields. During the drier seasons of 2009/10 and 2010/11, CA had a positive effect on maize grain yield at both sites (average yield of 4.4 and 3.3Mgha−1 in CA and CP respectively). However, associating maize with legumes reduced maize yields compared to CAM particularly in drier years of 2009–10 and 2010–11. Farmers spent at most 47daysha−1 producing maize under CA systems compared to 65daysha−1 spent under conventional tillage practices. However, total variable costs were higher in CA systems compared to conventional practice (at most US$416 versus US$344ha−1). CAMP resulted in more than double gross margin compared to CPM (US$705 versus US$344ha−1). Infiltration estimated as time to pond was highest in CA maize legume intercrops (8.1s) than CP (6.8s). Although it was not feasible to directly estimate effects on water balances of these farmer-managed experiments, it can be assumed that the yield differences between CA and CP could be attributed to tillage and crop residue cover since other farm operations were generally the same. Intercropping maize and pigeonpea under CA presents a win-win scenario due to crop yield improvement and attractive economic returns provided future prices of maize and pigeonpea grain remain favourable.

Medium-term effects of conservation agriculture based cropping systems for sustainable soil and water management and crop productivity in the Ethiopian highlands

In the northern Ethiopian highlands, croplands yield extremely high volumes of storm runoff and are the major contributor to sediment load in the rivers. A medium-term tillage experiment was carried out (2005–2010) on a Vertisol to quantify changes in runoff, soil loss and crop yield due to Conservation agriculture (CA) in the sub-humid May Zegzeg catchment. A randomized complete block design with 3 replications on permanent plots of 5m by 14m was used for three tillage treatments, (i) derdero+ (DER+), permanent raised beds with 30% standing crop residue retention and no-tillage on the top of the bed, (ii) terwah+ (TER+), ploughed once at sowing with 30% standing crop residue retention and furrows made at 1.5m interval, and (iii) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues. Tillage operations in the three treatments were done using the local ard plough mahresha. Local crop rotation practices followed during the six years sequentially from the first to the sixth year included wheat-grass pea-wheat-hanfets (wheat and barley sown together)-grass pea-wheat. Glyphosate was sprayed starting from the third year (2007) at 2L/ha before planting to control pre-emergent weed in DER+ and TER+. Runoff and soil loss were measured in collector trenches at the lower end of each plot. Soil organic matter was determined at two depths (0–15cm) and (15–30cm). Local farmers evaluated crop stands. Significantly different (p<0.05) 4-yr mean soil losses of 14, 17 and 26t/ha, 5-yr mean runoff depth of 76, 95 and 118mm, and 5-yr runoff coefficient of 19, 24 and 30% were recorded for DER+, TER+ and CT, respectively. Soil organic matter was significantly higher in DER+ and TER+ compared to CT. The mean farmers’ evaluation of crop performance in the last three years (2008–2010) showed a significant higher score for DER+ (6/8) followed by TER+ (5.6) and least for CT (4.8/8), and improvements in crop yield were observed; however, a period of at least five years of cropping was required before the difference became significant. In addition to the positive effects on runoff, soil loss and crop yield, we argue that avoiding repeated tillage which is 10–11 oxen-span days per ha and the faster ploughing pace at sowing in DER+ will enable a reduction in oxen density with further natural resource benefits. DER + and TER+ are improvements to good local practices that qualify them as CA: we recommend large scale dissemination and implementation on Vertisols.

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.

Benefits of Conservation Agriculture on Soil and Water Conservation and Its Progress in China

Conservation agriculture has been practised for three decades and has been spread widely. There are many nomenclatures surrounding conservation agriculture and differ to each other lightly. Conservation agriculture (CA) is a system approach to soil and water conservation, high crop productivity and profitability, in one word, it is a system approach to sustainable agriculture. Yet, because conservation agriculture is a knowledge-intensive and a complex system to learn and implement, and also because of traditions of intensive cultivation, adoption rates have been low, since to date, only about seven percent of the world's arable and permanent cropland area is farmed under conservation agriculture. The practice and wider extention of conservation agriculture thus requires a deeper understanding of its ecological underpinnings in order to manage its various elements for sustainable intensification, where the aim is to conserve soil and water and improve sustainability over the long term. This paper described terms related to conservation agriculture, presented the effects of conservation agriculture on soil and water conservation, crop productivity, progress and adoption of CA worldwide, emphasized obstacles and possible ways to increase CA adoption to accelerate sustainable development of China agriculture.