Epagri reveals benefits of using biochar in onion production

Waste from charcoal industries can be great allies for onion producers to improve soil quality and crop productivity. This is what two research studies with biochar in agriculture carried out by Epagri at the Ituporanga Experimental Station point out. “The use of this residue, in addition to bringing benefits to the soil and plants, contributes to reducing the environmental liabilities of charcoal activity”, highlights researcher Fábio Satoshi Higashikawa.

Biochar is a low-cost material – sold for around R$1 per kilo in industries in Santa Catarina. “In the manufacture of charcoal that we use to make barbecues, a smaller and finer residue, also known as 'coal mill' or 'coal dust', is also generated in the industries. When we use this material for agricultural or environmental purposes, we call it biochar”, explains Fábio.

Epagri's research into the use of biochar in onion production began in 2016 with an unprecedented project in the world that evaluated the effects of this material on soil fertility in a direct planting system. This research received support from the National Council for Scientific and Technological Development (CNPq).

Soil fertility

The conclusion of the study was that, from a dose of 1t/ha, the use of biochar in onion crops improves soil fertility, increasing the levels of nutrients such as phosphorus, potassium and calcium and also organic matter. “Biochar also increases soil pH, reduces aluminum activity, which is toxic to plants, and can increase onion yield in years with favorable weather conditions”, adds Fábio.

The researcher explains that this material is more resistant to decomposition and, therefore, remains in the soil for longer than other forms of organic matter. “In this way, it provides more lasting benefits to the planting system”, he points out. The effects depend on the type of biochar, the dose, the type of soil and the planting system.

By using biochar to partially replace the use of fertilizers, onion producers will be able to reduce the cost of crop production. Epagri technicians recommend its use both for crops with conventional soil preparation and in the direct planting system. “Biochar can be applied to the surface of the soil and then incorporated, or it can be applied directly to the green manure straw”, recommends researcher Fábio.

Physical properties of the soil

A second study, recently completed by Epagri and also unprecedented in Brazil, proves the benefits of biochar on the physical properties of the soil and onion yield. The research, developed with support from the SC State Research and Innovation Support Foundation (Fapesc) and in partnership with the SC State University (Udesc), evaluated areas that received doses of this material in 2016.

The researchers evaluated two onion areas: one under a direct planting system and the other without cover crops. “As physical effects on the soil take time, we considered experiments lasting six years. In the scientific literature, there are very few studies under long-term field conditions that evaluate the effect of biochar on soil physical properties. Therefore, the project generated relevant and unprecedented information for the production chain and the scientific community”, highlights the Epagri researcher.

Resistance to erosion and drought

In addition to increasing the carbon content in the soil, the application of biochar increased the stability of soil aggregates. This characteristic improves erosion resistance. Areas with biochar also improved water retention and availability in the soil, reducing the need for crop irrigation.

“These effects increase the resilience of the soil and crops in years with unfavorable weather conditions”, summarizes Fábio. The results were observed from 1t/ha of biochar incorporated into the soil and were more evident in a direct planting system.

A third research project by Epagri using biochar in onion cultivation is already in the fundraising phase. The objective, in the next stage, is to evaluate the effect of this material on the microorganisms present in the soil. “According to data from the scientific literature, biochar increases biodiversity, abundance and activity of microorganisms in the soil”, points out the researcher.

Biochar in agriculture

The origin of the use of biochar in agriculture came from research on Terra Preta de Índio (TPI) – this is the name for the darkest and most highly fertile soils in the Amazon. Studies have indicated that TPI results from the activity of ancient indigenous peoples, who used carbonized organic matter to prepare the soil in agriculture.

In Santa Catarina, the practice of using biochar is still not very common in crops. Some farmers use this material to improve the soil in the production of vegetables and grains, but still without adequate criteria or doses. Researcher Fábio explains that one of the limitations of using this material is local availability. “Like all organic waste, the transportation cost limits its use to areas close to the production site”, he considers.