Effects Of Conservation Agriculture Research Articles

Conservation Agriculture Saves Irrigation Water in the Dry Monsoon Phase in the Ethiopian Highlands

Water resources in sub-Saharan Africa are more overstressed than in many other regions of the world. Experiments on commercial farms have shown that conservation agriculture (CA) can save water and improve the soil. Nevertheless, its benefits on smallholder irrigated farms have not been adequately investigated, particularly in dry monsoon phase in the Ethiopian highlands. We investigated the effect of conservation agriculture (grass mulch cover and no-tillage) on water-saving on smallholder farms in the Ethiopian highlands. Irrigated onion and garlic were grown on local farms. Two main factors were considered: the first factor was conservation agriculture versus conventional tillage, and the second factor was irrigation scheduling using reference evapotranspiration (ETo) versus irrigation scheduling managed by farmers. Results showed that for both onion and garlic, the yield and irrigation water use efficiency (IWUE) was over 40% greater for CA than conventional tillage (CT). The soil moisture after irrigation was higher in CA compared with CT treatment while CA used 49 mm less irrigation water. In addition, we found that ETo-based irrigation was superior to the farmers’ irrigation practices for both crops. IWUE was lower in farmers irrigation practices due to lower onion and garlic yield responses to overirrigation and greater water application variability.

Effects of conservation agriculture on productivity and Economics of maize-wheat based cropping systems in midwestern Nepal

The effects of two tillage methods (zero tillage and conventional tillage), two residue managements (residue kept and residue removed) and two levels of cropping system (maize + soybean and sole maize) were studied over 3 years (2015-2017) at Dailekh district of Nepal. Arun-2 and Puja were the varieties of maize and soybean used respectively, followed by winter wheat. The results revealed that the maize + soybean system had significantly higher plant population and ear population (34.83 thousands ha-1 and 34.35 thousands ha-1, respectively), grains per row (37.1), ear length (16.6 cm) and 20.5% higher grain yield as compared to sole maize. The highest maize equivalent yield (7.92 t ha-1) was recorded in maize + soybean as compared to the lower grain yield equivalent (7.06 t ha-1) in sole maize. Zero tillage accounted relatively higher benefits (high net income and B:C ratio) as compared to conventional tillage. The residue kept plot resulted significantly higher B:C ratio (2.41) than the residue removed (2.11) and the maize + soybean recorded 82.5% greater B:C ratio compared to sole maize. Net annual income was significantly higher in zero tillage, residue kept and maize + soybean system (NRs. 223072.00, 222958.00 and 269016.00 ha-1 respectively). Such combinations are recommended for Dailekh district of Nepal to have profitable crop productivity.
 SAARC J. Agri., 17(1): 49-63 (2019)

The Effect of Conservation Agriculture and Environmental Factors on CO2 Emissions in a Rainfed Crop Rotation

There are many factors involved in the release of CO2 emissions from the soil, such as the type of soil management, the soil organic matter, the soil temperature and moisture conditions, crop phenological stage, weather conditions, residue management, among others. This study aimed to analyse the influence of these factors and their interactions to determine the emissions by evaluating the environmental cost expressed as the kg of CO2 emitted per kg of production in each of the crops and seasons studied. For this purpose, a field trial was conducted on a farm in Seville (Spain). The study compared Conservation Agriculture, including its three principles (no-tillage, permanent soil cover, and crop rotations), with conventional tillage. Carbon dioxide emissions measured across the four seasons of the experiment showed an increase strongly influenced by rainfall during the vegetative period, in both soil management systems. The results of this study confirm that extreme events of precipitation away from the normal means, result in episodes of high CO2 emissions into the atmosphere. This is very important because one of the consequences for future scenarios of climate change is precisely the increase of extreme episodes of precipitation and periods extremely dry, depending on the area considered. The total of emission values of the different plots of the study show how the soils under the conventional system (tillage) have been emitting 67% more than soils under the conventional agriculture system during the 2010/11 campaign and 25% for the last campaign where the most appreciable differences are observed.

Conventional versus agro-ecological intensification: assessing the effect of conservation agriculture in maize cropping systems with the DSSAT model in Côte d’Ivoire (West Africa)

Integrated soil fertility management options are being promoted as ways of adapting agricultural systems to sustain yields on highly degraded and poor soils encountered throughout West Africa. The efficiency of these practices may be affected by high variability and uncertainty associated with seasonal rainfall, especially for areas such as Cote d’Ivoire, where intra-seasonal rainfall has been observed to change from 1 year to another. The DSSAT crop simulation model was used in this study as a tool to evaluate the impacts of soil improvement options including inorganic fertilizer and conservation agriculture generating higher carbon sequestration and crop yield in maize agro-ecosystems. The model was calibrated using agronomic data for three cropping seasons from 2009 to 2010 in Goulikao (Center-West Cote d’Ivoire) and Aheremou 2 (Central Cote d’Ivoire), respectively and validated against independent datasets of yield of 2003–2004 seasons in the buffer zone of the Lamto Natural Reserve, Central Cote d’Ivoire. The model predicted average maize yields of 1454 kg ha−1 across the sites versus an observed average value of 1736 kg ha−1, R2 of 0.72, and RMSE of 597 kg ha−1 after the default values for stable soil organic matter fraction used in the model were substituted by the estimated one. For the validation, the predicted higher maize yield was consistently related to fallow biomass inputs and different rates of fertilizer, thus generating a RMSE of total aboveground biomass and grain yield of 606 kg ha−1 and 350 kg ha−1, respectively. The impact of fallow residues and cropping sequence on subsequent maize yield was simulated and compared with conventional fertilizer and control data using 12 years historic climate time series. We conclude that soil fertility improvements through conservation agriculture can sustain grain yield at the same level as conventional inputs of urea against larger climate variability. However, this system may be substituted by conventional agriculture when climate forecast reveals a dry cropping season year.

From plot to scale: ex-ante assessment of conservation agriculture in Zambia

This study combined bottom-up and top-down approaches to assess the ex-ante effects of conservation agriculture (CA)-based systems in Zambia considering both biophysical and economic factors and prevailing farm systems characteristics. For continuous maize cropping we compared a CA-based system of no-tillage with crop residue retention to a control system of conventional tillage with crop residue removal. First, we simulated yield effects that were calibrated and evaluated against multiple datasets, including on-farm agronomic trials from two seasons and six sites. Next, we extrapolated our simulations to all maize-growing areas in Zambia using gridded climate and soil datasets. Then simulated yields (in kg ha−1) were combined with economic data from a nationally-representative household survey to construct economic indicators including benefit-cost ratios (based on gross benefits and variable costs both in $ ha−1) that captured the implicit value of crop residues and labor demands. The field scale (per ha) indicators were scaled out using harvested areas as an expansion factor. All indicators were calculated over 3-, 10-, and 20-year simulation periods using an interpolated sequence of historical climate data. Finally, we conducted a spatial farm typology analysis to help understand the spatial variation in our field-scale indicators and provide insights into trade-offs and the suitability of CA-based systems for farmers. Average changes in yield from using CA-based systems (compared with the control) at the district scale ranged from −37% to 70% (average 33%), with a similar range of changes in benefit-cost ratios once economic factors were included, in addition to intra-district yield variability. Combining the changes in benefit-cost ratios with maize harvested area resulted in an average annual change in district-scale net benefit ranging from US $ − 3.9 to US $9.9 million (with an average of US $1.1 million). The heterogeneity in biophysical and economic factors gave a ranking of provinces different according to biophysical or economic indicators, reinforcing the importance of coupling biophysical and economic approaches. The spatial farm typology analysis highlighted the specific contexts of farmers relevant to the suitability of CA, such as their mineral fertilizer applications rates, ownership of livestock, and prevailing soil texture and rainfall.

Experimental Evaluation of Conservation Agriculture with Drip Irrigation for Water Productivity in Sub-Saharan Africa

A field-scale experimental study was conducted in Sub-Saharan Africa (Ethiopia and Ghana) to examine the effects of conservation agriculture (CA) with drip irrigation system on water productivity in vegetable home gardens. CA here refers to minimum soil disturbance (no-till), year-round organic mulch cover, and diverse cropping in the rotation. A total of 28 farmers (13 farmers in Ethiopia and 15 farmers in Ghana) participated in this experiment. The experimental setup was a paired ‘t’ design on a 100 m2 plot; where half of the plot was assigned to CA and the other half to conventional tillage (CT), both under drip irrigation system. Irrigation water use and crop yield were monitored for three seasons in Ethiopia and one season in Ghana for vegetable production including garlic, onion, cabbage, tomato, and sweet potato. Irrigation water use was substantially lower under CA, 18% to 45.6%, with a substantial increase in crop yields, 9% to about two-fold, when compared with CT practice for the various vegetables. Crop yields and irrigation water uses were combined into one metric, water productivity, for the statistical analysis on the effect of CA with drip irrigation system. One-tailed paired ‘t’ test statistical analysis was used to examine if the mean water productivity in CA is higher than that of CT. Water productivity was found to be significantly improved (α = 0.05) under the CA practice; 100%, 120%, 222%, 33%, and 49% for garlic, onion, tomato, cabbage, and sweet potato respectively. This could be due to the improvement of soil quality and structure due to CA practice, adding nutrients to the soil and sticking soil particles together (increase soil aggregates). Irrigation water productivity for tomato under CA (5.17 kg m−3 in CA as compared to 1.61 kg m−3 in CT) is found to be highest when compared to water productivity for the other vegetables. The mulch cover provided protection for the tomatoes from direct contact with the soil and minimized the chances of soil-borne diseases. Adapting to CA practices with drip irrigation in vegetable home gardens is, therefore, a feasible strategy to improve water use efficiency, and to intensify crop yield, which directly contributes towards the sustainability of livelihoods of smallholder farmers in the region.

Modelling soil hydrothermal regimes in pigeon pea under conservation agriculture using Hydrus-2D

Limited information is available about the effects of conservation agriculture (CA) practices on soil temperature moderation and distribution of water in the soil profile during crop growth, particularly on the changes in the components of water and energy balance. Hence, the objective of this study was to assess soil hydrothermal regimes and water and energy balance components in pigeon pea (Cajanas cajan) grown under CA in a pigeon pea-wheat (Triticum aestivum) cropping system using the Hydrus-2D model. There were seven treatments: permanent broad bed (PBB), PBB with crop residue (PBB + R), permanent narrow bed (PNB), PNB with crop residue (PNB + R), zero tillage (ZT), ZT with crop residue (ZT + R), and conventional tillage (CT). Results during the seventh year of the experiment showed that the PBB, PBB + R, PNB, PNB + R and ZT + R treatments significantly reduced surface soil bulk density (BD), increased field saturated hydraulic conductivity (Ksat) and improved soil water retention over the CT. The Ksat values obtained as the output of the Rosetta-Lite model which is implemented in Hydrus-2D) were very low. Hence, experimentally measured Ksat values were optimized along with parameters α and n that were obtained as output of the Rosetta Lite model, through inverse modelling (IM). The model predicted daily changes in profile soil water content (SWC) with reasonable accuracy (R2 = 0.77, RMSE = 0.012; n = 84). Soil water balance simulated from the model indicated higher cumulative transpiration (CTr), lower cumulative evaporation (CE) and higher soil water retention in the PNB + R and PBB + R plots than CT. Computed values of thermal conductivity (λ) obtained from the observed soil temperature (ST) data at different SWC values showed significant correlations with those optimized through IM. In general, Hydrus-2D model over-predicted the ST values during a simulation period of 10 days. However, reasonably accurate (R2 = 0.91, RMSE = 1.41 °C; n = 102) predictions were observed for the 0–20 cm soil layer using the optimized values. It was also observed that PBB + R and PNB + R treatments improved soil hydrothermal regimes, root growth, radiation interception, leaf area index and biomass production of the pigeon pea crop. Hydrus-2D used in this study could also satisfactorily simulate the temporal changes in energy balance components, such as soil heat flux (G) and evaporative heat flux (LE). Hence, this model may be adopted for evaluating arable management practices for characterizing different components of water and energy balance in pigeon pea.

Effect of conservation agriculture on stratification of soil organic matter under cereal-based cropping systems

ABSTRACTDegradation of soil quality caused by conventional tillage practices is a major concern for the sustainability of rice-wheat cropping systems in South Asian region. Therefore, suitable conservation agriculture (CA) practices are required. This study investigates the stratification and storage of soil organic carbon (SOC) and total nitrogen (TN) as affected by eight years of different CA practices in the North-West Indo-Gangetic Plains of India. There were four treatments: (1) conventionally tilled rice-wheat cropping system, (2) reduced-till CA-based rice-wheat-mungbean system, (3) no-till CA-based rice-wheat-mungbean system, and (4) no-till CA-based maize-wheat-mungbean system. The mean stratification ratio (SR) (i.e. a ratio of the concentrations of SOC and TN in the soil surface to those in a deeper layer) of SOC and TN for 0–5:5–10, 10–15, 15–20, 20–25 and 25–30 cm were found higher (> 2) under CA practices compared to intensive tillage-based conventional agricultural practice (< 2). No-till CA-based rice-wheat-mungbean system stored the highest amount of SOC (25.32 Mg ha−1) whereas reduced till CA-based rice-wheat-mungbean system stored highest amount of TN (3.21 Mg ha−1) at 0–30 cm soil depth. This study shows that CA stratifies SOC and TN and helps to enhance SOC sequestration and soil quality.

Conservation agriculture based sustainable intensification of basmati rice-wheat system in North-West India

ABSTRACTContinuous mono-cropping of rice-wheat (RW) system with conventional tillage (CT) based management practices have led to decline in soil health, groundwater table and farmers profit in north-west India. A medium-term (4 years) farmer’s participatory strategic research trial of basmati RW system was conducted to evaluate the effects of conservation agriculture (CA) based management practices on crop yields, water productivity, profitability and soil quality. Six treatments were compared varied in the cropping system, tillage, crop establishment and residue management. CA-based management under zero-till direct seeded rice-wheat-mungbean recorded 36% higher system yield than conventional till rice-wheat system (14.91 Mg ha−1). CA-based rice-wheat system and rice-wheat-mungbean system saved ~35% irrigation water compared to conventional RW system (2168 mm ha−1). Total water productivity (WPI+R) was improved by 67% with CA-based rice-wheat-mungbean system (0.90 kg grain m−3) over the conventional system. On system basis, 42% higher net return was recorded with CA-based rice-wheat-mungbean system compared to conventional system (USD 2570 ha−1). Mungbean integration in basmati RW system contributed 29% share in system net returns across the treatments. Soil chemical and biological properties were improved by ~40% and 150%, respectively, with CA-based management system.

Effect of conservation agriculture on soil hydro-physical properties, total and particulate organic carbon and root morphology in wheat (Triticum aestivum) under rice (Oryza sativa)-wheat system

Short-term (5 years) effect of conservation agriculture (CA) practice on soil hydro-physical characteristics, soil organic carbon status and root morphology in wheat (triticum aestivum L.) was monitored under rice (Orgza sativa L.)-wheat rotation in a clay loam soil at the Indian Agricultural Research Institute, New Delhi. A small improvement in soil water content and a marginal decrease in bulk density by CA contributed in significant reduction (30-37%)in sub-surface compaction. The CA improved soil structure in the plough layer (0-15 cm) with significant increase in soil organic carbon status (27-38%). A marginal change in pore size distribution was recorded in favour of larger volume of retention pores (11-12%), in expense of macro- or drainable pore space. Steady-state infiltration, which was essentially profile-controlled, was therefore lower in the CA plots. Decrease in sub-surface soil strength and better soil water retention facilitated root growth in wheat in the sub-surface layer under CA. Results implied thatthe CA practice in rice-wheat system, although with a shorter period, led to an overall physical improvement of the most active root zone. This had positive impact on root morphology, which contributed to increase in the crop yield.

Conservation agriculture effects on soil properties and crop productivity in a semiarid region of India

Conservation agriculture (CA) including reduced or no-tillage and crop residue retention, is known to be a self–sustainable system as well as an alternative to residue burning. The present study evaluated the effect of reduced tillage coupled with residue retention under different cropping systems on soil properties and crop yields in a Vertisol of a semiarid region of central India. Two tillage systems – conventional tillage (CT) with residue removed, and reduced tillage (RT) with residue retained – and six major cropping systems of this region were examined after 3 years of experimentation. Results demonstrated that soil moisture content, mean weight diameter, percent water stable aggregates (&amp;gt;0.25mm) for the 0–15cm soil layer were significantly (P&amp;lt;0.05) affected by tillage practices. Soil penetration resistance was significantly higher for RT than CT. Irrespective of soil depth, there was higher soil organic carbon (SOC) for RT than CT. The SOC fractions followed in the order: non-labile&amp;gt;moderately labile&amp;gt;less labile. At the 0–15cm depth, the contributions of moderately labile, less labile and non-labile C fractions to total organic C were 39.3%, 10.3% and 50.4% respectively in RT and corresponding values for CT were 38.9%, 11.7% and 49.4%. Significant differences in different C fractions were observed between RT and CT. Soil microbial biomass C concentration was significantly higher in RT than CT at 0–15cm depth. The maize–chickpea cropping system had significantly (P&amp;lt;0.05) higher soybean grain equivalent yield of 4.65 t ha–1 followed by soybean+pigeon pea (2:1) intercropping (3.50 t ha–1) and soybean–wheat cropping systems (2.97 t ha–1). Thus, CA practices could be sustainable management practices for improving soil health and crop yields of rainfed Vertisols in these semiarid regions.

Corrigendum to: Conservation agriculture effects on soil properties and crop productivity in a semiarid region of India

Conservation agriculture (CA) including reduced or no-tillage and crop residue retention, is known to be a self–sustainable system as well as an alternative to residue burning. The present study evaluated the effect of reduced tillage coupled with residue retention under different cropping systems on soil properties and crop yields in a Vertisol of a semiarid region of central India. Two tillage systems – conventional tillage (CT) with residue removed, and reduced tillage (RT) with residue retained – and six major cropping systems of this region were examined after 3 years of experimentation. Results demonstrated that soil moisture content, mean weight diameter, percent water stable aggregates (&amp;gt;0.25mm) for the 0–15cm soil layer were significantly (Pmoderately labile&amp;gt;less labile. At the 0–15cm depth, the contributions of moderately labile, less labile and non-labile C fractions to total organic C were 39.3%, 10.3% and 50.4% respectively in RT and corresponding values for CT were 38.9%, 11.7% and 49.4%. Significant differences in different C fractions were observed between RT and CT. Soil microbial biomass C concentration was significantly higher in RT than CT at 0–15cm depth. The maize–chickpea cropping system had significantly (P–1 followed by soybean+pigeon pea (2:1) intercropping (3.50 t ha–1) and soybean–wheat cropping systems (2.97 t ha–1). Thus, CA practices could be sustainable management practices for improving soil health and crop yields of rainfed Vertisols in these semiarid regions.

Effect of conservation agriculture on grain yield and income of maize under maize based cropping system in far western Nepal

Effect of conservation agriculture on grain yield and income of maize under maize based cropping system in far western Nepal

Conservation agriculture in western China increases productivity and profits without decreasing resilience

This study examined the economic and risk effects of conservation agriculture (CA) in western China using nine years of data from an agronomic field experiment and a case study for a typical crop-livestock farm. A CA system of a wheat-pea rotation with no-tillage and stubble retention was compared with the current practice of the same rotation but with conventional tillage and stubble removal. Risk was examined by computing the resistance and resilience of grain yields to climate shocks at the field scale, along with calculating the stability of yields and profits at the field and farm scale. Climate shocks were defined using the standardized precipitation evapotranspiration index. Resistance indicated the proximity of grain yields during a climate shock to average yields. Resilience indicated the rate of return towards average grain yields after a climate shock. At the field scale, CA increased grain yields by an average of 19.6% and increased profits without negatively affecting resistance or resilience. At the farm scale, CA increased profits by an average of 5%, increased the stability of profits by 33%, and reduced labor demands. Despite these gains, the adoption of CA in western China remains low. Results suggest that at present the private gains to farmers are not large enough to encourage the more widespread adoption of CA. Therefore, because CA also produces public benefits for conservation of the environment such as reduced erosion, financial incentives may be considered to assist CA adoption in specific farming systems.

Conservation Agriculture Effects on Crop Productivity and Soil Properties in Ethiopia

Core Ideas Conservation agriculture (CA) was evaluated in Ethiopia.Short and medium‐term effects of CA depends on initial soil properties.Improved water infiltration and crop yield can occur in the short‐term.Yield increase in the short‐term is less likely with moderate soil in humid areas.Canopy reflectance can be used to study in‐season effects of no‐till and residue. Conservation agriculture (CA) is common globally but not in tropical Africa, including Ethiopia. Conservation agriculture was evaluated at Bako (short‐term CA study) and Melkassa (medium‐term CA study) in Ethiopia for effects on crop yield and soil properties. Results showed the rate of water infiltration was 16% more at Bako and 15% less at Melkassa for conventional practice (CP) (tillage plus crop residue removal) compared with CA (no tillage plus residue retention). Time‐to‐pond was doubled and soil penetration resistance was 7 kP less for the 0–0.1 m depth with CA maize (Zea mays L.)–dry bean (Phaseolus vulgaris L.) rotation compared to CP maize monoculture at Melkassa. Soil organic C for the 0–0.05 m soil profile was 16 g kg−1 with CA compared with 12 g kg−1 for CP and early maize growth was slower with CA compared with CP at Melkassa. Maize stover yield was 10.14 Mg ha−1 for CP compared with 9.01 Mg ha−1 for CA in 2015 at Bako, but maize yields were greater with CA at Melkassa in 2016. Monoculture and intercrop dry bean, respectively, had 40 and 32% more grain yield with CA compared to CP in 2016 at Melkassa. It was concluded that medium‐term beneficial effects of CA on soil properties and crop productivity can be expected at Melkassa, but any short‐term benefits of CA at Bako were uncertain.

Effect of conservation agriculture on grain yield and income of maize under maize based cropping system in far western Nepal

Abstract. The adoption of Conservation agriculture (CA) contributes to sustainable production and its advantages include lower inputs and stable yields. This study was conducted in the research field of Regional Agricultural Research Station, Bhagetada, Dipayal, Doti during 2014 and 2015 to identify the effect of CA on grain yield and income of maize in Maize based cropping system. Both conservation and conventional agricultural (ConvA) practices were evaluated on two maize based cropping systems namely maize-wheat-mungbean (M-W-MB) and maize-lentil-mungbean (M-L-MB). For this purpose two maize varieties namely Raj Kumar and Arun-2 were used. The average productivity of maize under M-L-MB cropping system was 1.6% higher (5.75 t/ha) than M-W-MB cropping system (5.66 t/ha). The average grain yield of maize under CA was 16.7% higher (6.15 t/ha) than ConvA (5.27 t/ha). Rajkumar produced 43% higher average grain yield (6.73 t/ha) than Arun-2 variety (4.69 t/ha). The average net benefit was slightly higher (US$ 597.33/ha) under M-L-MB cropping system than M-W-MB cropping system (US$ 573.89/ha). Similarly, the average net benefit from CA was 102% higher (US$ 783.67/ha) than ConvA (US$ 386.79/ha). Rajkumar variety gave 127% higher average net benefit (US$ 813.49/ha) than Arun-2 (US$ 357.81/ha). The average benefit - cost (B:C) ratio of M-L-MB cropping system was slightly higher (1.72) than the average B:C ratio of M-W-MB cropping system (1.70). The average B:C ratio of CA was 42% higher (2.01) than ConvA (1.41). The average B:C ratio of Rajkumar variety was found 33% higher (1.95) than Arun-2 (1.46). The higher grain yield, net profit and B:C ratio were found in CA practices under M-L-MB cropping system and Rajkumar variety. This study suggests that hybrid maize planting and the adoption of M-L-MB cropping system should be used to increase grain yield and economic performance under CA practices.

Effects of conservation agriculture on crop and system productivity and profitability under maize based system in far western Nepal

Effects of conservation agriculture on crop and system productivity and profitability under maize based system in far western Nepal

Conservation agriculture effects on crop and water productivity, profitability and soil organic carbon accumulation under a maize-wheat cropping system in the North-western Indo-Gangetic Plains

The Indo-Gangetic Plains (IGP) of India is dominated with rice − wheat cropping system that occupies almost 10.5 million ha area. The sustainability of rice-wheat system is under threat due to numerous water-, nutrients-, weeds- and environment-related problems, mainly, due to the cultivation of rice. Suitable crop and soil management practices with a bias to conservation agriculture (CA) that can sustain soil and environmental health as well as improve crop and water productivity, are required for the Indian IGP. Maize can be a viable alternative to rice and a potential driver for diversification of rice-wheat system. The acreage of maize is on the increase in conventional and conservation agriculture-based cereal systems of India in recent years. Therefore, a field experiment, involving a maize (Zea mays L.)-wheat cropping system was undertaken on a sandy clay loam soil for three years (2010–11 to 2012-13) in New Delhi to evaluate the impacts of CA on crop and water productivity, profitability and soil organic carbon (SOC) accumulation. There were five CA-based treatments in first year, and two treatments were introduced in second year (2011-12) onwards. The experiment was laid out in a randomized complete block design with three replications. In all the residue retention plots, wheat residue was retained in maize crop and maize residue was retained in wheat crop under zero till conditions. Results showed that the plots under permanent broad bed with residue (PBB+R) and without residue (PBB) resulted in ∼29 and ∼26% higher maize grain yield, respectively than conventional tillage (CT) (2.6tha−1), but wheat grain yields were comparable in all the treatments in first year. Maize grain yield in second year under PBB+R and zero tillage with residue (ZT+R) were 55 and 43% higher than CT plots (2.8tha−1). Three-year mean maize yields due to PBB+R and permanent narrow bed with residue (PNB+R) were 28 and 15% higher than that in CT plots (3.3tha−1). The PBB+R resulted in 11% higher two-year mean water productivity in maize than PBB (∼without residue), but both these treatments were comparable in this regard in wheat. The ZT+R plots resulted in 14% and 22% higher two-year mean water productivity, respectively in maize and wheat than ZT plots. Overall, the plots under PBB+R had 57% and 19% higher mean water productivities in maize and wheat, respectively compared with CT plots. Again, the PBB+R plots gave 12% higher two-year mean net returns compared with CT plots. With regard to net returns, the plots under permanent narrow bed with and without residue (PNB+R; PNB) were inferior to PBB, PBB+R, ZT and ZT+R plots. Retention of both-season crop residues could significantly improve SOC concentration in surface (0–5cm) soil. The PBB+R resulted in highest SOC pool at 0–30cm soil layer, which was significantly higher than that in CT. This system showed maximum carbon sequestration potential. Thus, this CA practice, which involves PBB+R is superior to other practice. This would save water through higher water-use efficiency, and lead to accumulation of more carbon in soil with higher sequestration potential, besides giving sustainable production through maize-wheat system over the years. This can be adopted across the IGP regions of India, where irrigated rice-wheat system is in practice, and in similar agro-ecologies of the tropics and sub-tropics under irrigated conditions.

Conservation agriculture improves yield and reduces weeding activity in sandy soils of Cambodia

The years of intensive tillage in Cambodia have caused significant decline in agriculture’s natural resources that could threaten its future of agricultural production and sustainability. Conventional tillage could cause rapid loss of soil organic matter, leading to a high potential for soil degradation and decline of environmental quality. Hence, a better and comprehensive process-based understanding of differential effects of tillage systems and crop management on crop yield is critically needed. A study was conducted in 10 farmer’s fields to evaluate the effect of conservation agriculture and conventional tillage on yield of selected crops and weeding activity in two villages of Siem Reap, Cambodia. The experiment was laid out following a 2 × 2 factorial treatment combination in randomized complete block design. Each treatment was replicated five times. Each farmer’s field was divided into four plots and was randomly assigned with production management and irrigation treatments, respectively. We demonstrated that our results supported the overall premises of conservation agriculture. Average yields of selected crops were significantly (≤ 0.001) improved in plots with conservation agriculture (17.1 ± 6.3 to 89.3 ± 40.2 Mg ha−1) compared with conventional tillage (18.8 ± 6.4 to 63.8 ± 27.7 Mg ha−1). Our results showed that manual weeding in all cropping seasons was significantly reduced by about 35% in conservation agriculture (169 ± 23 to 125 ± 18 man-day ha−1), which can be attributed to existing cover crops and surface mulch. Overall, our results suggest that in smallholder commercial household farms, adoption of conservation agriculture had a profitable production management system, which could save natural resources, improve yield, and reduce labor. We proved for the first time that in Cambodian smallholder commercial household farms, adoption of conservation agriculture saves natural resources, improves yield, and reduces labor. Additional studies are encouraged to further test the conservation agriculture system for a longer period of time, with repeated cropping sequences.

Agro-ecological functions of crop residues under conservation agriculture. A review

Conservation agriculture, which is based on minimum tillage, permanent soil cover and crop rotations, has widely been promoted as a practice to maintain or improve soil quality and enhance crop productivity. To a large extent, the beneficial effects of conservation agriculture are expected to be provided by permanent soil cover with crop residues. Surface crop residues play an important role for crop growth through their benefits on soil-related structural components and processes in the agro-ecosystem, referred to in this study as agro-ecological functions. Through a meta-analysis of the literature, we have studied the relative effects of surface crop residue levels on the performance of a set of agro-ecological functions compared with a no-till bare soil, i.e., without surface residues. The selected agro-ecological functions were soil water evaporation control, soil water infiltration, soil water runoff control, soil loss control, soil nutrient availability, soil organic carbon (SOC) stocks and gains, weed control and soil meso- and macrofauna abundance. The potential effects of crop residue cover were quantified using boundary line models. Our main findings were (1) 8 t ha−1 of residues were needed to decrease soil water evaporation by about 30% compared to no-till bare soil. (2) To achieve the maximum effect on soil water infiltration, water runoff and soil loss control, residue amounts of at least 2 t ha−1 were required. (3) The effect of increasing the amounts of surface crop residues on soil nutrient supply (N, P and K) was relatively low; the boundary line models were not significant. (4) The average annual SOC gain increased with increasing amounts of residues, with a mean of 0.38 t C ha−1 year−1 with 4 to 5 t ha−1 of residues. (5) Weed emergence and biomass can be reduced by 50% compared to a no-till bare soil with residue amounts of 1 t ha−1 or more. (6) There was a weak response in soil meso- and macrofauna abundance to increasing amounts of surface crop residues. The maximum effect corresponded to an increase of 45% compared to a no-till bare soil and was reached from 10 t ha−1 of residues. Our findings suggest that optimal amounts of surface residues in the practice of conservation agriculture will largely depend on the type of constraints to crop production which can be addressed with mulching.