Microplastics in Agriculture -‘Not’ a Micro Issue

In a kilogram of soil, there can be over 40,000 microplastic particles. Imagine that!

What are microplastics? Microplastics are small pieces of plastic particles, fibersstarting from the sizes 1-5000 microns, which occur in the environment as a direct result of plastic pollution. These originate from degeneration of car tires, domestic products, industrial processes and surfaces composed of plastics. Microplastics have been identified as a global environmental threat for terrestrial as well as aquatic ecosystems, and human health. 

A Mouthful of Microplastics

The amount of plastic in the oceans is anticipated to reach 250 million metric tons by 2025 - an appalling prediction which suggests that by 2050 the oceans will contain more plastics by mass than fish! Until now, the main focus has been on microplastics in the ocean and their effects on marine life – and rightfully so. However, here's the real shocker - microplastics in agriculture soil occur at higher levels than in marine systems. Recent reports suggest microplastics in soil have an effect on soil chemistry and microorganisms. Fertilizers made from sewage sludge, rain and airborne fallout are all pathways for these particles to settle into the soil. Common agricultural practices of disposing of plastic mulching, water pipes, and plastic greenhouse covers further damage the soil.New research also suggests that soil affected by microplastics produces less crop yield because of less productive earthworms and lower pH levels. It’s clear that microplastics compromise soil health, and the long-term impact could potentially include stunted soil biodiversity.

A Reason to Worry

In addition to microplastic contamination of soil from numerous sources, ‘intentionally added’ microplastics - added purposefully to serve a useful purpose –could be a serious cause of concern. Considered a common practice in agriculture and horticulture, microplastics are mostly added to the soil in the form of nutrient prills for controlled-release of fertilizers to manage the rate at which ammonium is converted in nitrate. These prills are a coating typically composed of a polymer such as polysulfone, olyacrylonitrile, or cellulose acetate, that encapsulate nutrient combinations for fertilization particles of synthetic polymers (microplastics). Microplastics are also used in capsule suspension plant protection products, seed coatings, water-soluble polymers for soil remediation, and water absorbents.

Taking a Step Back, Moving Forward

While several regulations of the Government of India address the issue of plastics, concrete regulations on microplastics in agriculture are insufficient. Agro-environmental microplastic related policies are the need of the hour. The design of effective and efficient policies, validated by research, about the potential consequences of microplastics in agricultural landscapes from application of sewage sludge, and other sources should be considered to reduce further consequences of microplastics in agricultural systems.