Conservation Agriculture Research Updates - April 2026

This paper from North America synthesized data from 30 meta-analyses to comprehensively assess the impacts of the no-till (NT), reduced till (RT,) and mixed NT+RT on crop yields and GHG emissions. Results showed that the yields of wheat, maize, rice, fibers, cotton, and cereals were not significantly affected by NT, while the yields of soybean, oilseeds, and legumes were enhanced by NT. NT did not influence soil CO2 emissions, and none of the tillage treatments influenced soil CH4 emissions. However, NT increased soil N2O emissions whereas RT and NT+RT had no significant effect on soil N2O emissions. They suggested that the varied impacts of tillage can be attributed to soil properties and practices like crop residue management, irrigation type, and nitrogen rates. 

This paper suggests that CA adoption is crucial for enhancing SOC and mitigating climate change for future food security. The research assesses the effectiveness of various factors controlling SOC sequestration derived from literature reviews and 469 data points spanning 42 years.Results showed that CA significantly increased  SOC by almost 30% compared to CT. The highest SOC result was no-till, plus chemical fertilizer (CF), and straw return (S). Interestingly, CF + S or CF + manure led to greater SOC sequestration compared to the application of CF alone. Also, the annual SOC change rate (ASCR) of CA is closely linked to the experimental duration of its application, demonstrating an overall exponential decline followed by stabilization after several years. Overall. this paper contributes to the understanding of how CA sequesters carbon in soil.

This interesting article looked at 650 scientific papers to provide an analysis of global scientific production on Conservation Agriculture (CA) and its relationship with climate change mitigation. There has been a significant increase in publications in the last 30 years on sustainable. agricultural practices including key themes on no-tillage, SOC, and GHG emissions. Results indicate that CA research is increasingly focused on its potential to mitigate climate change, particularly through practices like no-tillage, vegetative cover, and crop rotation. This analysis underscores the importance of CA in addressing climate challenges and offers insights into emerging research areas, such as regional adaptations and the long-term effects of no-till systems. The findings aim to guide future research and policy development in sustainable agriculture and climate mitigation. 

This paper did an extensive literature review to look at the biodiversity of pulse systems and ecosystem services using different management systems in terms of food/feed provision and soil health.  Most studies examined soil quality, especially chemical quality, followed by grain yield. Very few studies surveyed biodiversity, most of which used arable flora as an indicator. Their results and conclusions showed significant positive impacts with organic farming on biodiversity, no tillage on soil health and yield, and rotations on yield.

This meta-analysis compares the yield and nitrogen use efficiency (NUE) between conservation tillage (CA?) and conventional (CT) for different cropping systems , mulching methods, N levels and addition of manure in US and China. The results show that CA at high-N enhanced the yield and NUE, and reduced the yield and NUE at low-N, compared to CT. NT with leguminous cover crops (LCC) significantly increased wheat yield NUE under low-N compared to CT. They conclude that based on the results, moderate N with LCC and manure application is recommended for growing winter wheat in dryland regions of the USA and China.

I added this paper on cover crops since there is a surge in the use of this management system in countries where CC's can be introduced into the agricultural system. This paper used 43 meta-analysis and review studies that compare cover crops to mono-cropping to identify benefits, challenges, and trade-offs among ecosystem services when cover crops are introduced. The paper summarizes the knowledge of CC effectiveness across 11 ecosystem services in 3 categories -- regulating, provisioning, and supporting. Factors chosen include farm practices, planting and termination season, species of cover and main crop, climatic zone and soil properties, cover crop biomass, and residue management. One main highlight was that cover cropping enhances soil biodiversity and nutrient cycling. Others can be found in the paper. Their overall conclusion is that  that a multifunctional cover crop implementation provides substantially more regulating and supporting than other ecosystem services.

This research looks at soil extracellular enzyme activities (EEA) on soil nutrient cycling using a meta-analysis with 3238 observations on the effects of NT and legume incorporation into a rotation system. Results show that NT significantly increased the activities of C, N and P acquiring, and oxidative enzymes. Combining NT with legumes did not affect on EEA's, but crop diversity did. They also identified climate, soil properties and agronomic practices as important factors affecting NT-induced changes in EEA's.

This meta-analysis used 78 globally published papers that included 2005 comparisons with the goal to quantify the effects conservation tillage (CA?) on soil organic carbon (SOC) and extracellular enzyme activity (EEA). Results showed CA increased SOC and C, N, P and S related enzymes. Climatic, latitude and mean annual temperature, agronomic practices (fertilization and tillage), and soil depth, were identified as having direct effects on the EEA of the respective enzymes. They conclude from a global perspective, CA enhanced the activity of C-related enzymes, while the y of N-, P-, and S-related enzymes needs more research.

This article looks at the role of crop rotation on soil aggregation and associated organic carbon (OC). The used 2199 paired observations from 53 studies to elucidate the rotations role in soil aggregation and associated OC and to identify optimal climatic, edaphic and agronomic factors. Overall, rotation improved aggregate and OC contents in all aggregate classes compared to monoculture. Greater increases in soil aggregation and associated OC induced by crop rotation were associated with sub-soiling, no-till, straw retention, combined manure-inorganic fertilizers, and a lower nitrogen fertilization input rate with more rotation cycles and longer rotation length. Climate and initial soil OC were important for the benefits of rotation. They conclude rotation is important for the sustainability of agroecosystems.

This study from Europe suggests that farmers are reluctant to adopt conservation tillage because of lower yields compared with conventional tillage (CT). But like a couple of other papers in this January newsletter, they look at no-tllage (NT) by itself rather than with residue retention and rotation. Instead they look at ridge-till (RT) and strip-till (ST) as possible alternatives to CT and NT. They looked at 128 studies based on 624 crop yield observations from 21 European countries. They analysed the influence of crop rotation, crop type, texture, climate, tillage depth, residue retention, and duration of experimentation on the relative yield i.e., yield under NT/RT/ST over yield under CT. Their analysis show that NT resulted in 5.1% reduction while RT and ST each led to a 5% increase in crop yield over CT. But the abstract didn't mention the role of residue retention on yield of NT. Although in the paper a whole section was devoted to residue retention.

This paper reviewed the impact of cover crops on weeds in SE US. Since cover crop use is gaining momentum in the US along ,with no-till, this paper has relevance to CA systems. This is a meta-analysis of 28 journal articles that examines paired comparisons of weed biomass and/or weed density, plus cash crop yields under CC and bare ground conditions in SE USA. Results showed that CCs had a negative effect on weed density (-44%) but no effect on either weed biomass or cash crop yield. Further analysis showed that weed suppression was linearly related to CC biomass and highlights the importance of generating adequate CC biomass if weed suppression is the primary objective.

This Global Meta-analysis used 5230 paired observations from 446 studies to evaluate NT on upland crop yield and SOC. Overall NT decreased upland crop yields by 5% and increased SOC sequestration by 9.9%. Specifically, wheat and maize yields decreased by 7.7% and 2.3%, respectively. However, NT combined with crop residue return and crop rotation reduced the negative effect of NT on crop yield from 5% to 2.4% and increased SOC up to 12.8%. No-till increased yields in relatively arid areas, but reduced yields in more humid areas, whereas SOC was more likely to increase in humid regions. The paper suggests that more research is needed for NT with residue retained since their results show that CT was better than NT. But many papers show that NT is better then CT when residues are retained.

This article was selected because it covers crop rotation (CR), one of the pillars of CA, affects on soil organic carbon (SOC). The study used 513 pairwise data from 167 global studies and did a meta-analysis to look at the role of CR on SOC content. Their results showed that CR overall enhanced SOC content by 6.6%. SOC content increased more in regions with intermediate mean annual temperature and precipitation. CR had greater impact on SOC in neutral soil pH, loamy texture and medium levels of initial SOC and total N. CR also performed better for SOC in soybean -based cropping systems with more rotation cycles, longer rotation length, medium N use, and where NT, residue retention, and organic fertilizer was used. They concluded that their study helps establish and manage site-specific CR systems that could enhance SOC in agroecosystems, ultimately facilitating carbon neutrality.

This article looks at results from 147 peer reviewed studies from India's major agro-ecological and climatic regions to estimate soil organic carbon (SOC) changes due to Regenerative Agriculture (RA) practices.  RA practices included organic amendments (farmyard manure, green manure, compost, and biochar), no tillage, crop residue retention, and fertilizer management. Results show biochar provided the highest SOC gain. No-till and residue retention had moderate but consistent benefits over time. The most significant SOC gains occurred after 5 years. There was variation across agro-ecological regions, with semi-arid and sub-humid regions showing particularly strong responses. They conclude that RA practices effectively sequester carbon, particularly when applied over longer durations and in regionally adapted combinations.

This paper from Europe used a Meta-analysis to to evaluate the impact of management practices related to carbon and nutrient, vegetation, pest and disease and soil management, as well as grazing management on soil biota and soil biology. They screened 698 articles and came up with 90 that were eligible with a total of 790 pairwise combinations and 74,526 observations. Their study showed what agricultural practices improve or reduce soil biology that is useful for selection of sustainable farming systems. They found that reduced tillage, organic fertilization, cover cropping and intercropping resulted in positive improvements in soil health factors. They also developed a “Utility-Robustness” scoring system for soil actors, using a systematic framework to inform biological indicator selection tailored to specific management contexts.

This paper used a meta-analysis of CA and/or biochar use on soil-nitrate-N, N20 emissions, biological N-fixation, N derived from the atmosphere, grain Y, and Nitrogen use efficiency (NUE). They used 87 papers from 15 countries in SSA with 1643 paired observations. Their results showed that on average over all studies CA and/or biochar significantly increased grain yield and NUE compared to conventional systems. In addition, Residue retention resulted in a significant increase in soil NO3-N and N2O emission, compared to conventional practices. Biochar also increased biological N-fixation, grain yield and NUE. N2O emission increased significantly in soils with < 0.05 % total N, while biological N2-fixation increased significantly in soils with > 0.2 % Total N.

Since plant residues are important for CA no-till management, I chose this paper that looks at the Global impact of cover crops in farming systems. CA plus cover crops is gaining popularity among farmers in the USA. This study assessed the global impact of cover crops on yield. They reviewed 104 articles to collect field based yield data (1027 records) to quantify the impact of CC's on main crop yields. Their data showed that CC's led to an overall increase in major crop yield of 2.6%. The utilization of leguminous cover crops, cultivation in coarse soil texture and dryland areas, and the implementation of longer cover cropping duration were found to be conducive scenarios to enhance crop yields. Conversely, the use of non-legume cover crops, introducing them to fields under a short-term no-till system, especially in fine-textured soils, lowered main crop yields. More data is available in the paper but they conclude that understanding and comprehensive information advances the appropriate and targeted adoption of cover crops for policymakers, extension services, and farmers.

Since Glyphosate herbicide is important for weed control in CA and is receiving a lot of negative press, I have included this research paper. It discusses both urban and agriculture sources for this herbicide. They investigated long-term concentrations of glyphosate and main transformation product aminomethylphosphonic acid (AMPA) in a large meta-analysis of about 100 sites in the USA and Europe. The U.S. data reveal pulses of glyphosate and AMPA when the discharge of the river is high, likely indicating mobilization by rain after herbicide application. In contrast, European concentration patterns of glyphosate and AMPA show a typical cyclic-seasonal component in their concentration patterns, correlating with patterns of wastewater markers such as pharmaceuticals, which is consistent with the frequent detection of these compounds in wastewater treatment plants. They suggest as in the title of this paper that in Europe glyphosate  contamination in rivers is not from application in agriculture.

This paper conducted a meta-analysis on published research from India of CA effects on yield, SOC, soil health, and C-sequestration in different soils of the country. 544 paired observations comparing CA with CT from 35 Indian publications was used. There were differences in different locations and soil types listed in this paper. They conclude that promotion of CA in India will have to be location specific because of differences in crops, soil properties and climate.

This paper used a comprehensive database on the three main conservation agriculture practices (cover crops, diversified crop rotations, and no-till and/or reduced tillage (NT/RT)) to elucidate the effect of CA on N2O emissions and also identify the most important predictors of soil N20 emissions. Their analysis showed that NT/RT decreased soil N20 emissions compared to CT. The N20 reductions were w more common in humid climates and where the C level was less than 20g kg(-1). N20 emissions were variable using cover crops and different rotations. Cover crops were more likely to reduce soil N20 emissions in neutral soil pH and the lower C content listed above for tillage and N levels around 3g kg(-1). Diversified rotations tended in increase N20 emissions in temperate regions and neutral pH. They are able to describe the conditions where CA can contribute to mitigation of climate change.

This study used 764 comparisons to evaluate the impact of SOC in the topsoil and sub-soil layers while considering climate, management and initial soil properties. They show that straw return with different tillage practices improved SOC stock in both layers compared to residue removal. NT was more effective for increasing topsoil SOC in regions with medium temperature and low rainfall. Deep tillage was better in both top and sub-soil in regions with higher temperature and precipitation. The effects of straw return on SOC stock were also found to be associated with soil texture, with NTS having a greater impact on sandy to loam soils, and DTS having a greater impact on clay soils. 

This article looks at the sustainability of the rice-wheat systems of the Indo-Gangetic Plains of South Asia essential for food security in this region that is being affected by climate change and water and soil degradation. They used a meta-analysis framework to assess the impacts of CA economically and environmentally. They show wheat with CA has a higher yield, but slight reduction in rice yield compared to CT, although in Eastern India rice yields were higher. Carbon sequestration was 23% higher and water use saved 20% in CA compared to CT practices. CA practices were also more cost effective and provided higher net returns than CT. They conclude CA is a win-win strategy for mitigating climate change without affecting food and livelihood security.

This global meta-analysis paper of 91 studies in cropland ecosystems, evaluated the effects of no-tillage on soil aggregates and their associated SOC and TN concentrations. On average, no-tillage significantly decreased the proportions of microaggregates (MA) and silt+clay size particles (SIC) and increased the proportions of large macroaggregate (LA) and small macroaggregate compared to those in conventional tillage. The SOC concentrations and total N for all three aggregate sizes increased significantly with no tillage. They conclude that no-tillage enhances the formation of soil aggregates and the associated SOC and TN concentrations in global cropland ecosystems.

This paper summarized the results of 47 global studies with humid subtropical climates investigating the sources of variation in SOC responses to CA. Overall the effect of CA on SOC accumulation in the plough layer was 12% greater in comparison to conventional agriculture. However, the effect was variable depending on the SOC content under conventional agriculture. For soils with less than 40 Mg C ha(-1), increasing the proportion of crops with bigger residue biomasses in a CA rotation was a solution to increase SOC. The effect of CA on SOC also depended on clay content and became null with a SOC/clay index of 3.2. They conclude that SOC increments due to CA application can be achieved especially in agricultural soils with less than 40 Mg C ha(-1) and located in the middle latitudes or in the dry conditions of Mediterranean and humid subtropical climates.

This paper reviewed 132 peer-reviewed papers to investigate the effects of No-Till (NT) and Residue retention (RR) on absolute mineralizable carbon (AMC) and specific mineralizable carbon (AMC per unit SOC, SMC) in laboratory incubation studies. The results showed that NT significantly increased AMC in surface (0–5 cm) and subsoil (> 20 cm) when it had been practiced over the long-term (>15 years), without crop rotation, and in alkaline soils (pH >7.8) compared to conventional tillage. RR generally increased AMC, and its negative effect on SMC was significant in soils with a high input of N fertilizer (> 300 kg N/ha) and sandy soils compared to residue removal. NT significantly reduced SMC in neutral and acidic soils (pH < 7.8), or compared to chisel plow or rotary tillage. Furthermore, RR and NT generally improved soil indicators except ammonium nitrogen and bulk density, and RR improved most of them significantly. They conclude that when combined with other measures, e.g. N application with RR, and applied in combination, NT and RR can increase SOC while decreasing its mineralization, thus improving the sequestration of C.