Conservation Agriculture Research Updates - April 2026

This paper from Southern India assesses the impact of different tillage and weed management practices on soil nutrient stratification ratio (SR), carbon sequestration rate (CSR), carbon management indices (CMI), carbon retention efficiency (CRE) and monitor the grain yield of maize after three-years in CA with a cotton-maize-Sesbania cropping system. There are 3 tillage practices; CT cotton and maize, no sesbania = farmer practice; CT cotton- NT maize-ZT Sesbania; and NT for cotton, maize, and sesbania. 4 Weed treatments were herbicide, herbicide rotation, integrated weed management, and hand-weeded control. They conclude that NT plus residue retention and herbicide use would be a viable way to imporve soil health and imptove productivity of the cotton-maize-sesbania system.

This experiment from dryland cotton areas of India looked at the impacts of tillage and weed management on soil quality index and system yield in a cotton-maize system. Treatments included various combinations of conventional tillage (CT) and no-till (NT) in cotton and maize with and without the legume Sesbania rostrata.Weed treatments (sub-plots) included use herbicide (H), herbicide rotation (HR), integrated weed management (IWM), and one hand weeding (HW). The experiment was run for 3 years. They measured 40 soil variables for soil chemical and physical properties. The soil quality index and yield increased by 23% and 52%, respectively for the NT with cotton + Sesbania rostrata residues–NT with maize + cotton residues–NT with Sesbania rostrata + maize stubbles compared to the farmer practice that used CT and no Sesbania. They conclude that NT for Cotton, Maize and Sesbania with residue retention and IWM had better soil quality and yield.

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 is another adoption paper from the Mediterranean region -- Morocco, Spain and Tunisia. The study objectives were to investigate the sociocultural aspects of CA adoption, where they examined farmers’ understandings of ‘good soil management’ and a ‘good farmer’ identity. Crop rotation was a prominent concept cognitively tied to fertilizer application, bridging conventional and reduced tillage practices. CA farmers’ mental models of soil management were also more complex than conventional farmers. The ability to have good productivity and experience and knowledge were the most prominent aspects of farmers’ understanding of a ‘good farmer’. For CA farmers, environmental responsibility and innovation were important, whereas for conventional farmers, tillage and the use of mineral fertilizers, was valued more highly.

Since glyphosate is a very useful systemic herbicide in CA for weed control and especially with herbicide tolerant biotech crops, I have included this latest European review in the newsletter. There is an ongoing contentious debate about its use, but despite this the European Commission approved the renewal of its registration and use in Europe in November 2023 for European farmers. The European Weed Research Society held a 2-day workshop to identify critical uses of this herbicide and glyphosate alternatives. The paper identifies 4 critical uses of this herbicide in the EU; control and management of perennial weeds, weed control in conservation agriculture, vegetation management in tree and vine crops and herbicide resistance management.They conclude that reduced use of glyphosate will require an even greater focus on integrated weed management to reduce weed establishment in agroecosystems, increase weed management diversity and limit the use of alternative resistance-prone herbicides.

CA requires  utilization of residues as mulch and effective weed management. But these two important elements are more complex than just focusing on weeds and residues. This paper explores these two issues to provide answers and questions to these two items. One issue is free-range grazing of livestock on the residues after harvest. Another is burning of these residues. Without the residue soil cover, weed management cannot use the benefits of mulching. Herbicides can help but are costly and need farmer training. Several recommendations are made in this paper, but depend on the socio-economic status dynamics at farmer and community level.

This is an interesting article that compares regenerative agriculture with CA in a Mediterranean climate that is characterized by poor quality soils, high climate variability, and resulting heavy agrochemical reliance. CA has helped with these issues and enhanced crop productivity and helped mitigate financial risk, but other issues including herbicide resistance, input costs rising, and increasing climate variability require attention. The aim of this review was to evaluate a set of agroecological practices that constitute a Regenerative Agriculture (RA) concept, for their potential to address these challenges from a soil quality, crop productivity and whole-farm economics perspective. Organic soil amendments from agro-wastes and multi-species cover crops subjected to adaptive multi-paddock (AMP) grazing as a phase within the crop rotation to reduce weed pressure, enhance soil multi-functionality, and resilience against environmental stresses were two interventions discussed. However, they recommend the need for more long-term and context specific research in the future to validate these technologies.

This study looks at direct seeded rice (DSR) and NT DSR and the issue of weed control. Field experiments were conducted involving conservation agriculture (CA)-based DSRs compared to puddled transplanted rice (PTR) and weed control/herbicides treatments to appraise weed interference and productivity under an eight-year old CA-based rice-wheat system (RWS). All DSRs encountered more weeds than PTR. A double ZT system without residue had the highest density and dry weight of grassy weeds, but a triple ZT system without residue had the highest density and dry weight of broad-leaved and sedge weeds. However, a triple ZT system adding three crops residues reduced weed interference significantly and led to higher rice yield. The use of various herbicides significantly reduced all weeds. They recommended that the triple ZT system with rice, wheat and mungbean residues (C5) combined with application of herbicides be used in similar agro-ecologies in the IGP.

This paper investigated how much tillage reduces weed infestation and yield loss, and which systems and weed species are the most affected by tillage suppression. Data was collected from 395 arable cropping systems mainly in France. They used the data and simulated them over 30 years with 10 weather repetitions using the FLORSYS model. Three series were simulated, (1) using the recorded systems, (2) eliminating tillage without any other changes, (3) eliminating herbicides without any other changes. Among the recorded systems, herbicide treatment frequency index (HTFI) averaged over rotation increased when tillage frequency decreased. No recorded no-till system was herbicide-free. The simulations indicated that two CA pillars (diverse crop rotations, cover cropping) were essential to manage weeds while reducing (or eliminating) both tillage and herbicide use. More no-till cropping systems must be investigated to determine whether sustainable no-till herbicide-free systems are possible.

This study looks at the issue of weed control in CA systems that has labor and costs of production problems. This study looked at a CA based rice (direct seeded)-wheat-mungbean cropping pattern over two years of study. The goals were to study the types and distribution of weeds in non-puddled rice and following strip-tilled wheat fields, and to find the most economic way to manage the weeds in both crops. The latter goal included using herbicides. The most most effective treatments involved two herbicides with one applied pre- and one post emergent in wheat and two other herbicides in direct seeded rice also applied pre- and post-emergent.

This paper looks at the issues of weeds and nutrient immobilization in CA systems in India in the maize-wheat system. For weed control they looked at using Sesbania brown manuring followed by post-emergent herbicides in maize and a herbicide tank mix in the following wheat that gave minimal weed infestation and the highest maize and wheat yields. For nitrogen the best treatment was half applied basal and the rest as guided by an Optical crop sensor, resulted in saving 56 and 59 kg N ha−1 in the maize–wheat system, respectively, over 100% N application as farmers’ fertilizer practice. There was also a significant interactive effect of weed management and N-use on economic maize and wheat yields. 

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 article looks at the understanding and decoding of site-specific complexities of CA systems using a multidisciplinary approach. It is more of a discussion rather than a research paper. They make the following comments. CA typically improves soil quality and water conservation; however, its effect on crop productivity is highly variable and dependent on local conditions/management. Crop residue retention plays a crucial role in CA and can help to improve overall soil health and ultimately crop productivity and sustainability. However, weed control, herbicide resistance, and weed shift under residue retained fields is a challenge. CA can also increase water infiltration and reduce soil loss and runoff. This reduces the surface transport of nitrate and phosphorus from agricultural fields and the eutrophication of water bodies, although leaching of nitrate to groundwater can potentially increase. In addition, CA has been proposed as one of the components in climate-smart agriculture, owing to its reduced period to seed/plant next crop, reduced soil disturbance and low consumption of fossil fuels.

This paper from Canada looks at application rates of Glyphosate (GBH) to terminate cover crops and how this influences soil microbial communities. They used 3 GBH application rates in maize, soybean and wheat fields grown with direct seeding (NT) with and without cover crops. Results showed that DS+CC did not significantly impact microbial richness compared to DS, but did alter specific abundance among prokaryotes and eukaryotes but that the three crops significantly influenced the composition of eukaryotic communities in 2018 and 2019, but not prokaryotic communities. They conclude that the study calls for sustainable agricultural practices that preserve microbial diversity, which is essential for maintaining ecosystem services and soil health.

This paper looks at Ridge Tillage (RT) in Germany that results in better root growth and reduced erosion. The study develops an auto-steered living mulch seeder using a navigation satellite system to guide making ridges. It also compares weed control for ridge-hoeing with conventional flat tillage (FT). They also looked at RT compared to FT for maize root development, yield, soil temperature, and soil moisture. Root penetration was 40 % higher in RT than in FT with RT producing more maize root biomass compared to FT.

This article evaluates the changes in microbial activity in time after applying3 herbicides to 2 different soils (S1) and (S2) under conventional tillage and no-tillage under field conditions. Various soil biological measures were determined after 1, 34, and 153 days. Without any herbicide all microbial activity was higher under NT than CT with similar or higher values for S1 compared to S2. With herbicides, decrease in microbial activity was greater in CT than NT. It is suggested that this was because the herbicides were adsorbed in the mulch in NT.

This article used the agro-hydrological Daisy model to look at degradation and leaching of pesticides under CA and conventional scenarios. Using a Daisy soil column they took measurements of topsoil, mulch and a realistic subsoil and tested against published experimental data pesticide fate in laboratory soil columns. Results showed no systematic difference in pesticide leaching from the topsoil between CA and CT, but pesticide degradation and sorption were significantly different; degradation in the mulch and uppermost soil surface layer (0–3.5 cm) was larger in CA while degradation was larger in CT when considering the whole topsoil (0–30 cm). 

Phalaris minor has been a major problem in wheat production in South Asia having developed resistance to many herbicides. This article evaluated the effectiveness of pyroxasulfone to control resistant P. minor in a maize-wheat cropping system. There were 3 crop establishment systems; Bed planting, NT and CT with all three having residue retention. There were 5 weed management strategies including 3 herbicide combinations, a weedy check and a weed free treatment. The best main treatment was bed planting plus residue with the lowest P. minor density and total weed population. Among the various weed management options, the combination of pyroxasulfone fb metsulfuron + carfentrazone recorded significantly lower P. minor density and higher weed control efficiency, similar to the weed-free check.

This review discusses the economic implications banning glyphosate herbicide in Europe, but this would also be relevant where used in farming. Its renewal is presently under discussion in Europe because of recent claims on human health. They used 19 studies published in 2022 where annual and perennial tree crops use this herbicide and any ban would be have large negative economic impacts. Economic losses arising from a glyphosate ban estimated in peer reviewed studies range from 3 Euro/hectare in silage maize up to 553 Euro/hectare in grapevine production.

This review presents some of the most important terms and definitions used in CA and no-till technology. It also describes the concepts and foundation principles of CA. It cites sources and detailed notes about the development of the concept of CA, machinery, devices, and techniques that that no-till technology uses. It also briefly other topics like economic benefit, weed control, cover crop and rotation, and use of herbicides. They conclude that in cases of no significant reduction in crop yield, the application of CA technology seems worthy due to the ecological benefits which it provides. But they end by saying with NT adoption - any expectations for quick revenue should not be considered feasible because ecological sustainability could only be achieved in a long-term application of CA and NT.

Weeds are a major constraint in Maize in Mexico but best management methods are lacking.  This study evaluated weed dynamics and rainfed maize yield under five weed management treatments (pre-emergence herbicide, post-emergence herbicide, pre-emergence + post-emergence herbicide, manual weed control, and no control) and three tillage methods (conventional, minimum and zero tillage) in 3 agro-ecologies in Mexico. The most effective weed management treatments tended to be similar for the three tillage systems at each site, although weed pressure and the potential yield reduction by weeds tended to be higher under zero tillage than minimum or conventional tillage. No single best option for weed management was found across sites or tillage systems.

This paper addresses issues of transplanted rice, by incorporating conservation agriculture (CA) based crop establishment practices in combination with suitable weed management options to sustain rice productivity. Their experiment had four planting techniques; farmer’s practice (Conventional Transplanting), zero-till direct seeded rice (ZT-DSR), reduced-till direct seeded rice (RT-DSR) (Rotavator single pass) and conventional-till direct seeded rice (CT-DSR) plus five weed management practices using various herbicides, plus hand weeding 20 and 40 DAS and a weedy check. Among various crop establishment methods CT-DSR recorded significantly higher N, P and K uptake by both grain and straw over the rest of the treatments except ZT-DSR during both the years. Based on the results application of pendimethalin pre-emergent followed by chlorimuron + metsulfuron at 20 DAS to the CT-DSR treatment gave the maximum N, P and K uptake by both grain and straw of rice.

This article advocates for integrated weed management rather than relying on herbicides. This study assessed the effects of four IWM systems with contrasting objectives and practices (S2: transition from superficial tillage to conservation agriculture; S3: no-mechanical weeding; S4: mixed mechanical and chemical weeding; S5: herbicide-free; all with 6 year rotations) compared to a conventional reference (S1: herbicide-based with systematic plowing and a 3 year rotation) on taxonomic and functional weed community composition and structure after 17 years of continuous implementation in a winter wheat crop. They found that resulting weed communities in IWM systems were more species rich (species richness from 1.1 to 2.6 times greater) and more abundant (total density from 3.3 to 25 times greater) than those observed in the reference system, and differed in term of taxonomic and functional composition. 

This paper looks at the gender implications of a change in weed management from tillage to herbicide with CA in South Asia. This was done by surveys with both spouses during crop establishment using 24 households who have adopted NT systems in the Eastern Gangetic Plains of South Asia. Comparisons were made pre- and post-tillage uptake. The found that the switch to NT provided substantial time-savings and did not increase the burden on women. ZT use did not reinforce or deepen existing inequalities within households. 

This is a chapter in a book with 30 chapters and over 600 pages on CA. The author describes how NT is becoming a recognized way to grow crops and and practice farming. The chapter goes on to describe the role of herbicides in controlling weeds in NT farming. The use of herbicides has been increasing in India due to shortages of farm labor and concerns about the affordability of labor costs and are the primary drivers for the growing popularity of agrochemicals and herbicides, which is expected to emerge as a key growth segment. But herbicides are not the only way to control weeds and an integrated approach should be used. Proper equipment and training in proper use is also needed.