Conservation Agriculture Research Updates - April 2026

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.

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.

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 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 study compared three types of fallow management (ploughing (CT), reduced tillage (RT), and no-till with glyphosate (NT)) on four fields after 17 years of no-plough, which ended with 7 years of CA. Weed density and species richness before weeding was greatest in RT, intermediate in CT and lowest in NT. They conclude that potential benefits of occasional ploughing will depend on the density and composition of the newly upwelled weed seedbank, which will need to be assessed before implementing tillage. From a multicriteria perspective, the long-term benefits associated with CA could largely exceed short-term yield increases associated with occasional tillage. 

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 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 impact of no-till and cover crops on soil health with sunflower following durum wheat in an on-farm trial in Italy. Direct sowing of sunflower following the dead mulch of a roller-crimped hairy vetch was compared with the use of glyphosate to terminate the vetch and control weeds. In this 3-year experiment, they compared three vetch termination stages (early: pre-flowering; Intermediate: beginning of flowering; late: 70% flowering) and three glyphosate rates (Nil, half and full). Vetch biomass increased from early to late termination and the extra biomass resulted in lower weed biomass. Treatments had inconsistent effects on weed diversity and composition, largely determined by the interactions between treatments and seasonal (different years) or local factors. They conclude that targeted timing of roller-crimped hairy vetch in no-till sunflower can result in equal agronomic and economic performances as addition of glyphosate.

The investigation was carried out on a farmer's field at two locations in Ethiopia.. The objective was to evaluate the impacts of conservation tillage on the productivity of durum wheat.Treatments were CT and reduced tillage (RT) with and without residue and one plowing at seeding plus roundup. Wheat yield increased by 44% at one site with RT+residue compared to RT-residue. CT yield was 23% higher compared to one plowing at seeding plus roundup. The highest net return was the RT+residue in the dryland area.

Weed control is a vital issue in CA systems. Glyphosate use has helped farmers control weeds, especially when using herbicide tolerant (HT) genotypes. The recent debate about the safety of Glyphosate  and excessive use of chemical herbicides in food production  has caused concern for farmers should this broad spectrum, easily degradable and environmentally friendly herbicide be banned. This paper estimates the costs associated with this prohibition in Spain. They conclude that a ban on Glyphosate would have a negative impact on the economic profitability of farms and also on the non-economic advantages derived from adopting CA.