Herbicides were hailed as "miracle" chemicals when they revolutionized farming in the late 1940s, but now researchers are eager to find a more sustainable, soil-friendly, non-toxic way to control weeds while promoting crop growth. Now, researchers in China believe they have achieved a major breakthrough that could lead to an eco-friendly future for wheat crops.
A research team at Huazhong Agricultural University has developed new lab-grown synthetic microbial communities (also known as SynComs) that essentially act like a microbial community that can eliminate weed targets while promoting crop health and growth. One of the bacteria SynCom isolated from weeds or wheat root nodules in particular shows great promise in helping the industry reduce herbicide use.
In a comparative greenhouse study of four SynComs (C1, C2, C3 and C4), C4 came out on top, not only killing harmful barnyardgrass that damages wheat crops, but also promoting the health and growth of the grain.
The research team noted: "All SynComs promoted wheat growth, as evidenced by increases in soil plant analysis development (SPAD) values and fresh biomass. At the same time, SynComC4, when combined with low-dose Axial herbicide, effectively reduced the SPAD values and fresh biomass of the infested weed little canarygrass."
Encouraged by these results, the researchers conducted a large-scale field trial in an area that had suffered from severe insect infestation for many years. They experimented with different doses of Axial (25%, 50%, 75% and 100%) and found a golden zone with the potential to significantly reduce the chemicals used on this staple crop.
The researchers noted: "The combination of C4 with 50% and 75% Axial significantly improved wheat growth by mitigating the side effects of herbicides on wheat. Weed infestation reduced grain yields at 50% and 75% Axial dosages by 16% and 25%, respectively. Combining Axial with C4 restored 22% of the grain yield losses under weed infestation compared to Axial alone."
"The study results show that the combination of herbicides with SynComs has a synergistic effect in controlling weeds and promoting wheat growth, therefore this combination provides a sustainable and eco-friendly weed control strategy."
Herbicides have had mixed reviews since their commercialization, and hundreds of synthetic compounds have been widely used in intensive agriculture to increase yields and reduce manual labor. However, while herbicides are widely used to control crop-destroying plants and have growth-promoting effects, herbicide toxicity to humans became apparent during the Vietnam War after the U.S. military used a mix of herbicides called Agent Orange (as well as agents violet, blue, pink, green and white) to defoliate trees and damage vegetation and crops. The herbicide was banned in the United States in 1971 (a year before the toxic pesticide DDT).
While herbicide use is strictly regulated in the United States, its use can have serious knock-on effects. Just as the human gut microbiome is important to overall health, the microbiome in the soil is vital to the life it sustains. Herbicides reduce the organic matter that cycles nutrients in the soil, degrading this unique microbiome and thus reducing crop yields. This in turn increases the chemicals used to promote growth.
However, SynComs come with their own challenges, such as competing species in the soil when released into the natural environment. Synthetic microorganisms may also change over time due to evolution and lateral gene transfer. (Herbicide use also causes plants to develop mechanisms to resist repeated chemical attack).
In this study, scientists found that C4 significantly promoted wheat growth, even in the absence of Axial. This is a promising development in areas of research including a new sugar-based herbicide, another herbicide derived from a "failed" antibiotic, and even plant-based foams.
The researchers noted: "Under field conditions, even when used with low-dose herbicides, C4 exhibits an ideal dual function of controlling wheat aphids and promoting wheat growth. Therefore, combining SynComs with low-dose herbicides is expected to become a sustainable and environmentally friendly weeding strategy."
The research was published in the journal Soil Ecology Letters.