Conservation Agriculture Research Updates - August 2025

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.

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 study, initiated in Canada in 1992, evaluated the effect of 25 years of N and P fertilizer application and tillage (Moldboard vs No-till) on density, biomass and composition of weeds before and after herbicide application in maize (2016) and Soybean (2017). It also evaluated the same treatments 6 years later in maize (2022). comparing  weeds found in 2004 all weed variables increased and there were more grassy weeds in both tillage treatments. No fertilization effect was observed on any weed variables, including composition, except for increased biomass when left to grow all season after crop planting. No till had higher density and biomass of both annuals and perennials before herbicide application but only reduced yield in soybean.

This research from Slovenia evaluates weed competitive ability under different tillage regimes in maize. There were three tillage practices; conventional (CN), conservation (CS) and no-tillage (NT). Use of Glyphosate and weed removal timing was used in sub-plots. The beginning and the end of the critical period of weed control (CPWC), based on a 5% maize yield loss rate, were determined by fitting the four-parameter log-logistic equations to the relative maize dry grain yield. They conclude that intensive tillage operations performed in the CN treatment and the pre-sowing use of non-selective burndown herbicide in the NT one delay the critical time for weed removal by more than 2 weeks, thus reducing the need for early post-emergence herbicide application in maize.

This paper looks at the role of cover crops in weed control either through direct competition, allelopathy or providing a physical barrier for emergence. However, they suggest that cover crop adoption remains limited by poor and/or unstable establishment in dry conditions, the weediness of cover crop volunteers in subsequent cash crops, and seed costs. This review looked at seed traits of various cover crops that would be helpful in selection of CC's for specific systems. They discuss how to improve CC establishment for 3 important CC families. Seed traits related to good germination were important with discussion on dormancy issues. The proper selection of cover crop cultivars and good establishment are vital in weed suppression.

This article looks at the weed community (seedbank and above ground) comparing CT and CA and variable N in a maize-wheat-mungbean system after 8 years at IARI in India. CA included no-till, residues and bed planting - narrow and wide permanent beds. CA practices had lower weed seed density compared to CT. CT also promoted  various sedges and Dinebra grass. CA promoted Digera and Melilotus broadleaf weeds. CT weedbanks also had higher ecological dominance, an indicator of a dominance of a few specific weed species.  The broad bed + residue + 100%N had higher system productivity compared to CT.

This is another paper from the Indian Himalayas that discusses degradation of environmental quality, water systems, and soil resources by present farming practices and the use of CA as an alternative option. The aim was to evaluate the effect of CA and weed management (WM) practices on carbon dynamics and biochemical properties of soil. The CA levels varied from conventional agriculture to partial CA (pCA1, pCA2, and pCA3) and full CA, while WM had three levels consisting of chemical control, integrated weed management, and weedy check. Results showed SOC and labile fractions of C were highest under full CA, but there were no differences for organic carbon. Full CA also had higher dehydrogenase and alkaline phosphatase activity than conventional agriculture. Full CA had the highest soil quality index and conventional the lowest. WM showed herbicide the best but little difference for weedy check or IWM.

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.

Upland rainfed rice in Madagascar is usually planted on tilled soil as seed and not transplanted resulting in serious weed issues. This field experiment looked at a no-till system with the legume Stylosanthes (NT) managed as a living mulch and compared with the tilled (CT) system. In addition two fertilizer treatments were added; organic manure (F1) and organic combined with mineral fertilizer (F2). Weeds flora were documented and the affect of weeds on rice yield assessed by having weedy and weed-free plots. The effect of the cover crop on rice yield was also assessed using weed-stylosanthes-free plots. Results showed that NT suppressed the dominant grass weeds leading to a decrease in total weed biomass. Rice yield was significantly higher in NT than in CT. The living mulch reduced rice yield by 14% but it remained significantly higher in NT than in CT. The addition of mineral fertilizer to the organic manure had a positive effect on rice yield but only in weed-free conditions.

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.

This paper investigates the effects on no-till (NT) and shallow conservation tillage (RT) in combination with cover crop mixtures in rotations with at least three different crops in on-farm experiments in Germany. Experiments were done in 18 farms and 2 experiment stations over 6 years. Yields of cereals, oilseed rape, maize, soybean and peas were slightly lower under no-tillage than under conservation tillage. Cover cropping did not affect crop yields. Tillage and cover cropping had no influence on weed control in the subsequent main crop. They conclude that CA with minimum tillage had slight advantages compared to the no-till system under their farming conditions.

This paper looks at weeds as responsible for crop losses but also beneficial for ecosystem services. They look at how arbuscular mycorrhizal fungi (AMF) in weeds respond to host identity and CA practices. The study was done in two locations in Southern Africa in both the off season and in-season maize. The diversity of AMF was highest under CA. Their findings highlight that implementing use of mulch and crop rotation to CT and NT positively affected weed AMF colonisation and diversity. The similarity between the off-season and in-season AMF composition of weeds supports the fact that weeds functionally host AMF during the non-crop period. 

This paper evaluated the importance of the third principle of CA, crop rotation and diversification to control weeds, pests, and diseases that can lead to increased yields and profits in Brazil. The objectives of this study were to determine whether grain production systems that employ crop rotation with species diversification are more productive and profitable than double-cropping rotations without diversification and to analyze the revenues and production costs of these cropping systems over a five year period, all under no-tillage and maize-soybeans. They conclude that where crop rotation was used there was higher productivity and profit than maize-soybean systems with rotation.

This two year field study from India looked at various organic weed management practices  for different tillage and residue management strategies on weed dynamics and yields in a rice-maize cropping system. There were 4 main treatments of tillage and residue management and 5 sub-plot weed treatments in a rice-maize cropping system. Total weed density and biomass in rice and maize at 30 days after sowing (DAS) were minimum for Bed planted NT rice and NT maize plus residue. Apart from the weed free treatment, the best weed control was with residue retention treatments. They conclude CA practices (NT + residues) in R-M systems has less weed issues and improves yields. 

This article is a three field study that looks at CA as a cost-effective alternative  to conventional tillage (CT) in rice-wheat systems in Karnal, Haryana, India using a flooded (FL) and sub-surface drip (SDI) irrigation. Results show that in rice, in ZT direct seeded rice with residue (+R) and SDI recorded 73% less weeds than the CT-puddled transplanted rice after 3 years. However, the ZTDSR without residue (R-) with flooding had the highest weed density and weed dry matter 37% less rice yield after 3 years. The paper lists the various weeds present. The same was found in wheat with the lowest WD and WDM in the ZT + SDI in year 3. The CA system improved yields over CTRW systems in weed free (WF) conditions, regardless of residue and irrigation management and should be recommended for RW systems.

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.

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 review of articles from 2000-2020 looks at the importance and current research status of crop rotation in agriculture. Note this is an important third pillar in CA. Five knowledge domains were identified as important for rotations (a) synergism and comparison of conservation agriculture measures or other management measures; (b) soil microecology, pest control, weed control, and plant disease control; (c) soil carbon sequestration and greenhouse gases (GHGs) emissions; (d) organic crop rotation and double cropping patterns; and (e) soil properties and crop productivity. In addition six important research areas were identified -  (a) plant–soil microbial interactions; (b) integrated effect with minimum soil disturbance and crop retention; (c) carbon sequestration and GHG emission reduction; (d) impact on weed control; (e) heterogeneity of rotation effects under different weather and soil conditions; and (f) comparison between long-term and short-term rotation.

This paper starts by saying "Burning of agricultural residues, cultivation of single crop varieties such as rice and wheat, and traditional soil tillage practices collectively contribute to the degradation of environmental quality, water systems, and soil resources. They describe CA as a viable alternative including weed management (WM). CA treatments varied from CT, three partial CA and a full CA. WM varied from Herbicide, Integrated WM and weedy check. They measured SOC, labile carbon fractions, total organic carbon, and several biochemical indicators of soil health. Results showed that CA had higher SOC and labile carbon fractions, and biochemical indicators resulting in a higher soil quality index value.

This article studied weed dynamics, productivity, profitability, and resource -use efficiencies in wheat under a long-term (12 year) CA-PP (pigeonpea) system as an alternative diversification for a rice-wheat system that is showing declining yields and lower resource efficiency. Treatments included flat and raised beds; CT and NT; narrow and wide beds; with and without residue; and N rates 75% and 100% of recommended. Only 89% and 62% of weed species were common to both CT and CA systems, indicating a shift in weed species in the long-term CA system in 2021-2022. Residue retention and N dose decreased weed density at 30 days after sowing. All the CA-based treatments reduced the weed density and dry weight compared to CT at 30 DAS. Wheat grain yield and net returns increased over CT in CA treatments. The wide bed treatments had the highest water productivity. Residue retention in NT permanent beds reduced energy productivity in CA than CT and no residue treatments.

This field experiment looked at a CA-based pigeon pea-wheat system impact on weeds and resource use after 12 years. Surface retention of residue irrespective of NT-permanent beds or N dose reduced weeds after 60 days. However,  CA-based systems reduced weed density and weed dry weight and had higher wheat yields compared to CT systems. CA systems also had lower water use and higher water use efficiency and wheat yield and water productivity were comparable between 75% N and 100% N in CA, indicating a saving of 25% N under CA.

This study looks at the potential impact of drought predictions on a faba bean crop, and evaluates the adoption of conservation tillage practices to reduce this effect in dryland areas of Spain. It sampled a long-term trial that was started in 2008 and looked at soil water storage (SWS), crop productivity and mineral nutrition, plant ecophysiology and biomass quality, as well as the colonization of roots by arbuscular mycorrhizal fungi (AMF) and symbiotic Rhizobium bacteria. It sampled the non-tillage (NT), reduced tillage (RT) and traditional tillage (TT)- and rainfall reduction treatments. The percentage of biomass yield reduction by rainfall exclusion was 30% for NT, 50% for RT and 20% for TT. They conclude that, despite no effect on soil water storage, in the conservation tillage systems the increase in the mycorrhizal colonization in roots, particularly under NT, could be beneficial for plants to face drought stress. However, in a scenario of reduced rainfall it will be necessary to invest more resources in weed control under RT.

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 study used an integrated network to show how the reduction of tillage (RT) intensity influenced invertebrates (such as rice pests and their predators), pathogens and weeds, that led to an impact on rice yield.This two year study showed that major rice pests, common diseases, and the density of weeds declined or were controlled by RT. The diversity and richness of pest predators increased in rice fields where RT or NT was used and yields increased gradually. The authors conclude that RT is beneficial for the protection of rice from various pests, and improves the sustainability of the agroecosystem and rice yield in southern China.

This paper looks at how weed density, community diversity, and structure are impacted by different combinations of CA principles (NT, Mulch (M) and Rotation (R) carried out in three seasons and two soil types (clayish and sandy) for maize in Zimbabwe. At the sandy location precipitation did not affect grain yield, but positively affected weed density, diversity, evenness, and richness. By contrast, at the clay location, precipitation positively affected grain yield, but did not modify weed density and evenness, and reduced weed community diversity and richness and also weed density affected grain yield. .