Research Articles Can The World’s Largest Peppercorn Producer Save Its Soils?
Black pepper, a staple in kitchens worldwide, comes largely from Vietnam — but now poor soil health is threatening the industry’s future and researchers are racing to find ways to restore soils and harvests.
By: Andrew Wight
In Vietnam’s Central Highlands Region, smallholder farmer tend to row after row of strange living towers of Black pepper vines (Piper nigrum), one of the earliest and widespread condiments — and in recent decades Vietnam has dominated global production, producing 2.2 tonnes per hectare and over 40 percent of 2020 global production.
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 intensive agriculture techniques, including pesticides and fertilizers, have acidified the region’s soils.
“When that happens, biodiversity decreases and it's an open door to whatever organism can survive the acidic soils,” Lesueur says, “Nematodes (roundworms), fungus-like oomycetes and pathogenic fungi come in because that's the kind of environment they can survive in and they have less competition.”
Didier Lesueur
Senior Soil Microbiologist - Coordinator of the Common Microbial Biotechniology Platform (CMBP)Vietnam is also the second largest exporter of robusta coffee, which is also under pressure from acidifying soils and soil borne pests and diseases.
“Both coffee and black pepper are threatened by the same phytopathogenic nematodes and fungi: This consortium of soil-borne pest and diseases interact and damage plantations of both commodities,”
Lesueur says, adding that after decades of rampant growth, growers of black pepper and coffee are facing diminishing harvests.
Intensive monocultures have degraded soil
Van Long Nguyen, a PhD student at Deakin University in Australia and first author of a 2022 paper co-authored with Lesueur and other collaborators, explains that there are two primary factors causing soil degradation under coffee and pepper cultivation: monocultural practices that lead to soil erosion and intensive cultivation which involves the misuse and overuse of mineral fertilizers, irrigation water, and synthetic pesticides.
“Long-term excessive mineral fertilizers, especially nitrogen fertilizer application, cause soil acidification; mineral fertilizers are at levels double or triple the needs of crops,” Nguyen says, adding that like other pepper-producing countries, Vietnam is facing problems with fungi (Phytophthora, fusarium spp.) and nematodes (Meloidogyne and Pratylenchus spp.).
Diseases have caused a significant reduction in cultivated areas in recent years; from 152,000 hectares in 2017 to 120,000 hectares in 2021.
Nguyen explains that because in the central highlands of Vietnam, coffee and black pepper are the key crops for smallholders, especially ethnic minorities, so switching to other crops may not be an viable option. Although the low price of peppercorn has led many growers to reduce their investment in irrigation, agricultural and chemical inputs, the price is on the rise again and farmers want to restart peppercorn production right away.
“Smallholder growers tend to employ chemicals to protect the crop from pathogens but chemical residue in peppercorns becomes a big challenge that significantly decreases the quality; and prevents the exportation into global markets such as Europe and America markets,” he says.
Restoring soil health may put production back on track
Nguyen explains that in order to control and mitigate soil degradation, especially acidification, soil amendments such as liming materials and agricultural wastes, and intercultural practices should be promoted and applied by farmers.
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, says Nugyen: “Could not only improve soil pH and soil physicochemical and biological properties but also reduce mineral inputs and retain current yield.”
“Those practices could not only improve soil pH and soil physicochemical and biological properties but also reduce mineral inputs and retain current yield,” Nguyen says.
Lambert Brau, a soil microbiologist and full professor at Deakin University explains that a new project, beginning in 2024 and led by Laetitia Herrmann, also of Deakin University, is focusing on land use and cropping systems in the central highlands in Vietnam.
Brau explains that there is still a lack of clarity on the extent and interaction of the various factors driving productivity decline in coffee and black pepper harvests, so there’s a need to develop a clear understanding of the on-farm issues affecting these crops.
“This project aims to deliver a situational analysis of on-farm coffee and black pepper production in five target provinces in the Central Highlands of Vietnam,” he says, “The project will investigate the farming systems that rely on coffee and black pepper production and examine the distribution of soil and plant health and agronomic factors that are constraining production in the region.”
Header Photo: Peppercorn plantation in Vietnam. Credit: Didier Lesueur
