Conservation Agriculture Research Updates - March 2026

This is the first selected paper for 2022 that uses meta-analytic and mete-regression to assess CA long-term experiments that also have CT practices in Southern Africa. They assessed how different agro-environmental yield response moderators such as type of crop diversification and amount of rainfall affect maize yield responses, especially for smallholder farmers. Results show that long-term trends in yield performance are a result of many factors; the greatest yield gains at each location ranged between + 34% and + 117%; the greatest yields were found in direct seeded rotation systems; rotations involving legumes were more responsive than any practice without diversification; CA systems gains increase with time of practice as compared to CP and these responses are more pronounced under low to moderate rainfall, and in well drained soils. 

This paper used an integrated framework that included bioeconomic simulation, risk analysis, adoption theory and impact assessment to look at CA components and growing a new crop or variety performed over a 10-year period on farms in Central Mexico. They found significant differences in profit, net value, downside risk, and risk-aversion cost between double-component scenarios (and improved CA to a lesser extent) and all other scenarios, which suggested that disaggregating CA into smaller component packages could increase farmer adoption in risky contexts. The study highlighted the need for employing a range of research tools to understand the relative value of agricultural innovations and to identify and reduce trade-offs and uncertainty in farming systems. 

This 13-year study in India looked at soil properties and the fate of Pendimethalin herbicide in a CA and intensively tillage managed system. Two cropping systems were mungbean-wheat and sorghum-wheat. There were three tillage treatments -- ZT+residue in both seasons; CT in summer + ZT+residue in winter; and CT in both seasons. The adoption of ZT-ZT system resulted in a 24% increase in infiltration rate, 13% greater moisture retention and 69% higher organic carbon content in surface (0-0.05 m) soil over CT-CT. Under the CT-ZT treatment, only a small change in the above soil properties was observed, which indicated that the benefits associated with CA was lost with tillage in the subsequent season. ZT-ZT caused more herbicide leaching into the sub-surface soil.

This is second paper highlighted from the SSSA special section on CA. This study aimed to evaluate the effect of 17 yr of residue retention (with and without) and tillage (plowing and no-till) on soil C storage on two Danish sandy loam soils with different clay and SOC content under cool temperate humid climate conditions. Straw retention reduced bulk density at both sites. It also increased the C concentration with 0.47 mg C g–1 dry soil on average from 2002 to 2019. Tillage altered the C distribution in the soil profile, so that the C concentration in the upper layer (0–25 cm) was higher in the no-till soils, but did not significantly increase total C concentration in deeper layers (0–50 cm). 

This Ethiopian study assessed the long-term impact of different conservation management systems (CMS) on soil organic carbon (SOC) using the DAYCENT model over a 30 year period. The management systems considered were minimum tillage, crop residue (CR) retention, fertilization and their combinations.Data came from studies in the literature. The alternate systems were compared with the business as usual treatment (BAU). Results showed CMS increased SOC in the 0-20 cm layer compared to BAU. The individual effect of fertilization, CR retention or minimum tillage management practices on SOC stock were lower than the response of the combined conservation management practices. They conclude that the combined 50–75% CR retention, NT, and increased N fertilization have a potential to increase SOC sequestration in resource-limited smallholding croplands. 

This seven years study was done to study the effects of different tillage practices and residue levels on weed shift, diversity and crop yields. Results show that annual weed species were dominant in conventional tillage (CT) and reduced tillage (RT), whereas a shift towards perennials was observed in zero tillage (ZT). CT recorded lower weed densities after 7 years. A shift in dicot weed species with higher weed density and biomass and a small decrease in monocot weeds was observed in ZT. The anchored residues 10 and 30 cm, recorded lower monocots and total weed count over no residue. They conclude that integrated weed management (combination of herbicide and removal of chance weeds) are efficient strategies to minimise the weed infestation in CA and these methods not only reduce the over reliance on herbicides but also improve the productivity of pigeon pea (Cajanus cajan L.), castor (Ricinus communis).

Soil compaction is a main issue threatening soil function and quality. This paper evaluates tillage and wheeling effects on physical properties of soils. The treatments were 13 years of no-tillage (NT), NT compacted with additional wheeling (NTc), minimum tillage (chiselling) soil (MT), and MT compacted with additional wheeling (MTc). Soil bulk density (Bd), macroporosity (Mp), precompression stress (sigma p), compressibility coefficient (Cc), and relative deformation were determined in four soil layers. Surface compaction in conservation agriculture is a major issue, since soil mobilisation by soil tillage should be avoided. Adding the residue mulch component of CA would have been an interesting additional treatment since other studies have shown that NT and mulch is better than just NT.

The paper contends that CA offers climate adaptation benefits, but suggest that effects of CA on yield are elusive. They analyzed 29-years of climate data, cotton yield, and soil data under 32 management practices in Tennessee, USA. They found that long-term no-tillage enhanced agroecosystem resilience and yield stability under climate extremes and maximized yield under favorable climate tied to enhanced soil structural stability and organic carbon. No-tillage enhanced the effectiveness of a legume cover crop in stabilizing cotton yield during relatively dry or wet, and dry years, while nitrogen fertilizer rate and precipitation timing, controlled yield stability in wetter years. 

This article was chosen since it studies tillage systems and liming in a sugarcane system in Brazil. Infiltration tests and soil sampling down to 0.10 m were performed in order to determine saturated soil hydraulic conductivity, soil bulk density, soil total porosity, macroporosity, microporosity, and soil resistance to penetration. Treatments included no-tillage (NT) and conventional tillage (CT) with 0 and 4 t/ha lime and an adjacent native forest (NF) as a check. The lowest bulk density and highest soil total porosity, macroporosity and saturated hydraulic conductivity were found in the NF. The bulk density in CT4 and NT0 was higher than in other systems, indicating the need for amelioration. NT4 is suggested as the most viable system for conservation agriculture in sugarcane fields, combining the benefits of no-tillage and liming to enhance soil hydrophysical functions.

This study investigated the response of soil chemical, biological and bacterial community properties to 11 years of different mulch and tillage practices in a sandy soil in a continuous maize cropping system in China. Treatments included: no-till + residue (ZT+R), rotary tillage + residue (RT+R), and normal tillage (CT). Compared to CT, ZT+R and RT+R significantly increased total organic carbon (TOC) content, C:N ratio, available nitrogen (AN) content, and acid phosphatase (ACP) and urease activities, while decreasing soil pH in topsoil and subsoil. ZT+R increased bacterial richness and diversity; dominant phyla of Actinobacteria and Acidobacteria were found in topsoil and Gemmatimonadetes in subsoil and deep soil. However, RT+R showed negative effects on soil bacterial diversity and bacterial community because of severe soil disturbance. ZT+R was the best treatment for chemical and biological properties in these sandy soils.

This study used the DayCent biogeochemical model to identify the best management practices for SOC sequestration. They used data from two long-term field sites in Western Kenya that used two promoted management practices: integrated nutrient management and conservation agriculture. Correlations at both sites between measured and simulated SOC were low to moderate, and in most cases produced fairly accurate predictions of SOC trends. The conclude that model results suggest that response of the passive SOC pool to the different management practices is a key driver of the long-term SOC trends at the two study sites.

This study evaluated soil macrofauna communities and related soil quality metrics in response to a 16-year winter cover crop and tillage trial located in the San Joaquin Valley of California, USA. Overall macrofauna abundance increased by 93% with the addition of cover crops in rotation, and 50% with the elimination of tillage. Taxonomic richness increased by 48% with cover crops in treatments managed without tillage, though there was no effect of cover crops under conventional tillage.Macrofauna abundance was positively related to total soil carbon, water infiltration, and soil aggregate stability. Macrofauna community composition was best explained by soil carbon, water stable aggregate fraction, and cover crop usage. 

This study in Finland looked at soil physical, chemical and biological properties, erosion and carbon allocation to soil physical fractions between CT and NT at a clay soil site after 10 years. After 10 years various soil properties and earthworm total density, mass and species richness were determined. Total soil erosion was 56 % less in NT than in CT although surface water discharge was higher in NT. NT had a clear effect on the topsoil physical structure by decreasing the pore size and increasing soil aggregate size. This paper didn't mention residue management. The results showed that NT is an effective method to reduce erosion rates but other means to increase carbon input especially below the topsoil layer are likely required to achieve a significant increase in the carbon stock of boreal clay soils.

This paper looked at SOC recovery from long term CA on-farm fields in Brazil. The study evaluated two systems -  (a) a comparison of SOC stocks to a 1-m depth in long-term CA at the farm scale (>20 years) with paired native vegetation and nearest available long-term research experiments (>30 years) in Southern Brazil; (b) explore the role of oilseed radish (Raphanus sativus L.) as a cover crop to enhance SOC accumulation. For the farm level CA systems, average SOC recovery was 92% (0–0.30 m) and 97% (0–1.0 m) in the soil profile relative to native vegetation. The main characteristics for SOC recovery (0–1.0 m) were high inputs of plant biomass, lack of soil disturbance, and diversification with oilseed radish cover crop.

This paper looks at the issue of Glyphosate resistant weeds in the soybean crop grown with CA in North America. The rise of Glyphosate resistant weeds in this crop has led to reductions in use of CA in soybeans.They estimate reduced-form and structural probit models of tillage choice, using a large panel of field-level soybean management decisions from across the United States spanning 1998–2016. The first emergence of glyphosate-resistant weed species did not effect tillage practices, though by the time that eight glyphosate-resistant weed species were identified, conservation tillage and no-till use fell by 3.9% and 7.6%, respectively. They estimate an economic value of the proliferation of Glyphosate resistant weeds in soybeans in USA.

This is another paper from the SSSA special section on CA. This study aimed to assess the effects of land use, tillage management, and crop diversification on soil physical quality of two long-term experiments in the Cerrado of Brazil through on-farm visual evaluation of soil structure (VESS) and soil physical parameters. Soil sampling was performed in 0-to-10- and 10-to-20-cm layers of four agricultural systems: soybean [Glycine max (L.) Merr.]–fallow under conventional tillage (SF); soybean–fallow under no-till (SN); soybean–maize (Zea mays L.) succession under no-till (SM); and crop rotation under no-till including soybean, maize, grasses, and legumes (CR). Native vegetation was kept as a check (NV). The study highlights that intensified agricultural systems need to be coupled with strategies to reduce and/or control intensive machinery traffic.

This paper presents the results of a global meta-analysis of studies assessing SOC and total N (TN) storage and dynamics in NT and tilled soils from the most important agricultural regions of the world. Overall, their results show that NT soils stored 6.7 ± 1.9 Mg C ha–1 and 1.1 ± 0.4 Mg N ha–1 more than tilled soils (0-to-100-cm depth) with an average of 16 yr of NT, in contrast with previous findings that found little or no soil organic C (SOC) accrual in NT soils as compared with full inversion tillage when soils are sampled deeper than 30 cm. However, C sequestration (+4.7 ± 1.9 Mg C ha–1 in the 0-to-60-cm depth with an average of 11 yr of NT) depended on the association of NT with increased crop frequency and the inclusion of legumes cover crops. Briefly, their findings indicate that NT can avoid SOC losses from tilled soils, partially offsetting CO2 emissions from agriculture. 

This 6-year study examined the residual effect of tillage and nutrient management applied to summer rice on root growth-attributes and impact on morpho-physiology of succeeding winter pea  grown uniformly under NT. Increased root exudation was observed under NT and MT (minimum till) along with organic residue addition. Also, enhanced chlorophyll pigmentation and favourable leaf characteristics were observed in the pea crop grown under NT with 50% NPK+weed biomass (WB)/green leaf manure (GLM) applications. They conclude that adoption of MT/NT along with 50% NPK+WB/GLM in summer rice is recommended for inducing favourable root environment and optimised pea production in succeeding winter season in study region of the Eastern Himalayas,

This paper uses a long-term farming system experiment to evaluate and compare the agronomic, economic and ecological performance of the most common arable cropping systems in Europe: organic, conservation, and conventional farming. It contains data for 43 agroecosystem properties and determines overall multifunctionality. Organic production resulted in higher economic performance, thanks to higher product prices and additional support payments. Our results demonstrate that different cropping systems provide opposing services, enforcing the productivity-environmental protection dilemma for agroecosystem functioning.

This 10-year CA experiment in China investigated the effects on soil respiration and net carbon (C) flux in the wheat-maize cropping system, and to identify the physicochemical controls of soil respiration C emission under different tillage and residue managements. Compared with continuous tillage, the reduced/no-tillage without residue significantly reduced soil respiration rate. C emission was ascribed to the accumulation of organic C, especially for the labile fraction, under residue returning than under residue removing. The increased organic C stock in topsoil accounted for the accelerated respiration C emission under reduced/no-tillage with residues.

This paper looks at the impact of CA and changes in crop rotation in the last 15 years that led to less disturbance of mouse burrows and increased ground cover and food supply on rodent pests. This study was justified since irregular outbreaks of mice in grain cropping regions in Australia and the damage they cause, makes it important to understand when and where mouse populations increase so that management strategies can be improved. They utilised a 20-year long-term mouse population data set collected prior to the introduction of CA farming practices and a more recent 8-year data set after CA to compare changes in mouse population abundance in a typical dryland grain cropping system in Australia. Mice are now resident year-round within crops and stubble and appear to only spill over into margin habitats. Previously developed recommendations for mouse management that include their control while in margin habitats may no longer be valid.

This 8-year study in India looked at the shift in weed species and diversity with different CA scenarios. The scenarios were Sc1, conventional tillage (CT)-based rice–wheat system with flood irrigation (farmers’ practice); Sc2, CT-rice, zero tillage (ZT)-wheat–mungbean with flood irrigation (partial CA-based); Sc3, ZT rice–wheat–mungbean with flood irrigation (partial CSA-based rice); Sc4, ZT maize–wheat–mungbean with flood irrigation (partial CSA-based maize); Sc5, ZT rice–wheat–mungbean with subsurface drip irrigation (full CSA-based rice); and Sc6, ZT maize–wheat–mungbean with subsurface drip irrigation (full CSA-based maize). Weed density, biomass and diversity remained almost the same across years. Observed shifts in weed species were therefore attributed to different CA scenarios that are discussed in this paper.

This is a study of the parasitic weed, Striga, a frequent problem for smallholder farmers in South Africa. They used system dynamic modeling to assess the efficacy of various striga treatments (SCPs) across different seasons and agroecosystems in maize based cropping systems. Model simulations indicate that while a combination of SCPs are necessary to manage the weed, future research should focus on developing smallholder-adapted SCPs that address the attachment stage of the weed's lifecycle (e.g., timely manure application) rather than its germination, emergence or flowering stages. They conclude that it is imperative to develop decision support tools like systems models to evaluate SCPs for smallholders that help extension agents to provide correct information to farmers.

This paper evaluated the chemical and physical processes in two different agricultural soils under no-tillage and conventional management practices to determine their impact on water related soil functions at field scale in the United Kingdom.Two farms were monitored; one had used NT in 2013 and the other conventional tillage with MB plow. Two soils were evaluated under each farming practice over two years. The conversion to no-tillage changed the soil structure, leading to a higher bulk density and soil organic matter content and thereby increasing the soil moisture levels. These changes impacted the denitrification rates, reducing the soil nitrate (NO3) levels. The increased plant material cover under no-tillage increased the levels of soil phosphate (PO43-) and PO43- leaching. 

This paper reports on the residue dynamics in a 12-year experiment (2007–2018) in the Wheatbelt of Western Australia, comparing rotations that included: cereal (cereal/cereal/cereal); diverse (wheat/legume/canola); farmer (wheat/barley/break – legume or fallow); and wheat monoculture. Crop residue was either spread behind the harvester (retain) or windrowed at harvest and burnt before seeding (windrow burn). Within rotations, residue quantity was highest with retained residue in the cereal rotation and wheat monoculture, averaging 5.0 t ha−1 prior to seeding, which could present management problems at seeding time in some years. Residue quantity was reduced to optimal levels by including legume crops or canola in the rotation, as these residues were more rapidly broken down than cereal residues, whilst maintaining residue retention practices.