Research Articles Can Agroecology Lead To A Greener Future For Tea?
In northern Vietnam intensive cultivation of green tea has led to poor soil health — now, researchers are testing out ways to reduce soil acidity and restore soils.
By: Andrew Wight
Green tea, whose leaves come from the same tree as black tea, but undergo a different process after harvest, plays a vital role in Vietnam’s heritage and economic present: Vietnam’s Import-Export Department estimated 2023 tea exports at 121,000 metric tons, with a current cultivation area of about 130,000 hectares.
Didier Lesueur, a senior soil microbiologist, at the French Agricultural Research Centre for International Development (CIRAD) and the Alliance of Bioversity International and CIAT, explains that decades of productivity gains from conventional farming practices have led to soil degradation, erosion, low tea quality and environmental pollution concerns.
“We started the project with a farmer who leads a cooperative trying to promote organic tea, in the north of Vietnam, a key province for green tea production,” he says, adding that the aim was to increase the quality and sustainability of the tea, while improving soils.
Didier Lesueur
Senior Soil Microbiologist - Coordinator of the Common Microbial Biotechniology Platform (CMBP)A 2023 study based on the project was the first comprehensive review showing how agroecological tea management practices can improve soil physical, chemical and biological properties; eliminate the concerns of chemical hazards on human health and the environment; as well as improve tea quality indicators, including amino acid, catechin and reduce the chemical residues in tea products.
Lesueur explains that the researchers compared the conventional systems with what is called an agroecological system, where organic farming techniques replace heavy pesticide and fertilizer uses.
“We demonstrated that soil health was increased by organic management,” he says, “The farmers were making a lot more money, the quality was increased and the business is doing well.”
Agroecological Tea Management
Over the past 20 years, tea and other cash crop farmers have used widely available agrochemicals and other inputs, including imported high-yield plant varieties. To offset this damage, farmers and researchers became interested in agroecological techniques: reducing tillage, elimination of synthetic fertilizers and pesticides, and use of biodiversity-based solutions to pests.
San Le, an agronomist, PhD student at Australia’s Deakin University and first author of the study, explains that he’s been working towards promoting conservation and sustainable agriculture in northern Vietnam (where soil health degradation is a major issue) since 2011.
Le explains that mineral nitrogen fertilizer is applied, plants directly take up the nutrient and their roots increase soil acidity, but tea plants also secrete malic acid, citric acid and oxalic acid.
“In 2019, I won a PhD scholarship, which was under the partnership between Deakin University, CIRAD and CIAT, which helped me to focus on investigating soil health status of tea plantation soils in relation to different management practices and solutions to improve the situation,” he says.
Le explains that agroecology recovers and enhance soil health by practices such as application of organic fertilizers and biopesticides, organic mulching and intercropping, which benefit soil hydrothermal environment, soil structure and water holding capacity (soil physical properties); improve soil organic matter, soil macronutrients and micronutrients, and reduces aluminum and manganese toxicity risks and nutrient leaching. Organic fertilizers and mulches generally provide more organic matter to soils compared to chemical compounds, which could attract soil fauna and facilitate the activities of soil microbial communities in converting soil nutrients, which ultimately increase soil nutrients.
Agroecological management regimes also reduces the risk of acidifying soil compared to conventional methods, as it doesn’t employ mineral fertilizers.
Lesueur explains that the application of tonnes of lime (calcium carbonate) reduces soil acidity by lowering (neutralizing) acid reactions in the soil, while composting and other agroecological practices.
“We try to see by liming to see if we could improve soil diversity, to sustain the tea yields and we got some positive effects, up to 2.5 tonnes per hectare,” Lesueur says.
Graphic: Comparing agroecological and conventional tea crop management. Credit: Le, V.S. et al. https://doi.org/10.1007/s42398-021-00182-w
Environmental and economic benefits
In recent years, there has been a rapid conversion from conventional tea farming to agroecological tea management practices such as using organic fertilizers and biofertilizers, mulching and intercropping, but Lesueur says that additional research is needed.
The researchers say the study shows an increasing global demand for high-quality tea products, which will allow agroecological tea producers to expand their production areas and export volume.
“The premium prices of organic/agro ecological tea products compared with conventional ones are mainly driven from the increasing awareness of consumers of unsafe products, particularly concerns with chemical residues in the agricultural goods which are conventionally produced,” Le says.
Lambert Brau, a soil microbiologist, full professor at Deakin University and another study coauthor, explains that aside from the environmental advantage, economic benefit has been considered as one of the most important drivers for moving from conventional to agroecological and organic farming.
“Our study shows that the agroecological tea farming provides a significantly greater net income for tea farmers compared with conventional tea management,” he says, “Organic tea adopters earned a higher net income compared with the nonadopters, which mainly resulted from the premium price of organic tea products to offset the increased labor costs and yield reduction.”
Header Photo: Green tea plantation in Vietnam. Credit: Didier Lesueur
