Too many species not recommended inter-cropping in rubber agroforestry systems----Xishuangbanna Tropical Botanical Garden,CAS

Rubber-based agroforestry systems are sustainable intercropping systems where farmers grow multiple crops or livestock alongside rubber trees to improve their income and/or subsistence while also reaping the subsequent ecological benefits. However, it remains unknown whether the addition of more intercropped species in the rubber–tea agroforestry system extends the benefits.

In a study published in Agricultural Water Management, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Yunnan Normal University investigated plant belowground competition dynamics, competition effects on plant nutrient status and plantsoil interactions at different rubber-based agroforestry systems in Xishuangbanna.

The researchers selected a rubber monocultural plantation (RM), three agroforestry systems including rubber–tea (RT) intercropping, rubber–orange–tea (ROT) intercropping and a complex jungle-like rubber–tea (J-RT) agroforestry system (a secondary forest), so as to help improve the sustainability and maximize the potential of rubber–tea agroforestry systems.

The researchers mainly applied stable hydrogen and oxygen isotope (2H and 18O) techniques to study plant hydrological niche differentiation and stable carbon isotopes (13C) to study plant water use efficiency (WUE).

To analyze how competition affected the nutrient status of plants and soil, the researchers measured carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations of different plant organs (i.e., leaf, stem, and root), litter and soil at those rubber agroforestry systems.

The researchers found that rubber trees primarily absorbed water from deeper soil layers with increases in their intercropped species number and the formation of increasingly obvious hydrologic niche differentiation between rubber trees and the intercropped plants.

In addition, soil nutrient status first improved but then declined with an increase in the number of intercropped species. However, negative competition effects offset the intercropping benefits for soil nutrients and water. Rubber trees are the most competitive species in rubber agroforestry systems. P shortage is a challenge for the growth of diverse intercropped plants.

“We suggest that the construction or improvement of rubber-based agroforestry systems should avoid interplanting too many species,” said ZHAO Fan, first author of the study.

Contact

ZHAO Fan

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China

E-mail: zhaofan@xtbg.org.cn

Available online: 8 May 2023