Weedicides And Its Impact on Soil Micro Flora

Indian Coffee is associated with the Agroforestry method of cultivating coffee along with multiple crops. Mechanization is to a bare minimum and when one visits the plantation one can see trees haphazardly arranged. The soil is virgin and no serious effort is made to mechanize the plantation for the sole purpose of retaining the sustainable eco-friendly systems. The bulk of the cost of running the plantation goes to labor, approximately 80 percent of the cost of cultivation is attributed to labor management. In recent years, the coffee landscape has undergone a sea change in terms of various packages of practices associated with coffee and allied crops. Due to the acute shortage of skilled workforce, coffee planters have made weedicide applications as part of their package of practice.

Globally, nearly 2000 herbicide molecules have been discovered and are used worldwide for the management of weeds. Economic viability combined with easy application makes it one of the most widely preferred methods for weed management. Herbicide contributes to 16% of the global pesticide industry, and in recent years, consumption of herbicide has increased many folds due to the increased cost of agricultural labor. Presently, in India, 68 herbicides are registered for broad-spectrum weed management in various arable crops. In India, the more common herbicide application is in wheat crop (44%), followed by rice (31%), plantation crops (10%), soybean (4%), and other crops (11%). Furthermore, the major herbicide products imported to India are glyphosate and atrazine. Pesticides Action Network (PAN) released a detailed study report on glyphosate use in India in 2020, outlining the dangers posed to human health and the environment.

Glyphosate

The herbicide N-(phosphonomethyl) glycine, commonly known as glyphosate, is a broad-spectrum, nonselective, systemic herbicide. It is an organophosphorus compound, specifically a phosphonate. It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops. It was discovered to be an herbicide by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market in 1974 under the trade name Roundup. Glyphosate is the most widely used herbicide in the world and its demand continues to grow

The adverse impact of glyphosate can be traced in food chains and its destructive behavior is through biomagnification. Scientific research has found evidence of its deleterious effects on the environment and its harmful effect on aquatic, semi-aquatic, and land-based organisms, as well as beneficial bacteria like nitrogen fixers, phosphate solubilizers, and with microorganisms involved in mineral transformations. Soil fertility is compromised. The ubiquitous presence of glyphosate can be found not only in plantation crops worldwide, but researchers have detected traces of this chemical in soil and water bodies, polluting precious groundwater resources. Though the International Agency for Research on Cancer has classified it as a probable human carcinogen, the companies that are engaged in manufacturing it claim that it is safe.

Glyphosate and Bees

The Coffee Planters are also unaware that the weeds are the primary sources of nectar for honey bees throughout the year. Eliminating weeds will only result in loss of bees, which in turn will have a downturn effect on cross-pollination and fruit set. In addition, glyphosate acts as a doubling of toxic effect on invertebrates, like pollinators.

Glyphosate and Superweeds

Repeated use of glyphosate, will kill native weeds and help develop super weeds which might be difficult to control.

How does glyphosate affect soil microbes?

There is a number of research papers that throw light on the harmful effects, both direct and indirect on beneficial soil microflora. Repeated use of the herbicide affects the soil microbiota by decreasing and altering microbial biomass and soil microbiome composition (diversity).

Among the biological effects of these chemicals, it can be cited genetic damage, diverse physiological alterations, and even death of the organisms exposed. Glyphosate kills plants by interfering with the synthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan in the shikimate pathway. A similar pathway exists in bacteria and fungi. Hence, glyphosate has significant negative effects on the beneficial microbial community growth and survivability especially nitrogen-fixing bacteria. Given the large number and diversity of soil microorganisms (bacteria, fungi, actinomycetes, microalgae) that are present in agricultural soils, it is inevitable that any chemical or substrate applied to the soil will perturb the functional dynamics of some components of this microbial community. The bacteria outcompete beneficial fungi, which improves soil productivity and increases carbon sequestration capacity. The resulting soil ecosystem is unhealthy and imbalanced, with a reduction in the natural cycling of nutrients and resilience. Thus, plants grown in such conditions are more susceptible to pests and diseases.

Glyphosate and Uptake of Macro and Micronutrients

Glyphosate is a chelating agent and its presence in the soil beyond acceptable limits leads to undersupply of macro- and micronutrients which are essential for many plant processes including plant-microorganism interactions of which nitrogen fixation is one of them.

One big side effect of using glyphosate is that it alters the soil texture. This in turn significantly reduces the microbial diversity of indigenous microbes. The consequence of this results in the acceleration of the population of phytopathogenic microbes which kill beneficial microorganisms.

Conclusion

The use of the herbicide glyphosate, negatively affects microbial communities, indirectly influencing plant, animal, and human health. The advantage of the use of herbicide is that it reduces the cost of cultivation but at the expense of ecosystem functions. Many times the impacts are so severe that it causes irreparable damage to the entire coffee ecosystem. Herbicides are washed with rain and can mix into groundwater. The risk of herbicides is not only limited through infiltration into other environments but also because of their slow decomposition they can maintain their biological activity in the soil for many years. In addition, compounds resulting from herbicide degradation may have greater toxicity than the pesticide itself.

The pesticide sector contributes $ 5 billion annually, and it is ever-growing, spreading its tentacles into every village and farm household. The disadvantage is that major multinational seed and pesticide companies have a strong presence in India and have their network in the remotest of villages. With such vested interests and a profit motive, it is too naive to believe that the government will enact any policies that will ban the use of glyphosate in India.

Any compromise will lead to irreversible damage to the coffee ecosystem.