Rice-crab coculture produces higher carbon sink and eco-economic benefits

Context or problem

Rice-crab coculture is a promising approach for developing eco-agriculture. However, there is limited information on the responses of net ecosystem CO₂ exchange (NEE) and eco-economic benefits to the shift from monocultures to rice-crab coculture.

Objective or research question

This study aimed to determine the benefits of rice-crab coculture system (RC) on carbon emission and sequestration, carbon sink strength, gross primary production, crab and grain yield and comprehensive economic income.

Methods

A 2-yr field experiment was conducted to evaluate three culture systems: rice monoculture system (RM), crab monoculture system (CM), and RC.

Results

The results showed that CM acted as a carbon source (NEE: 4.76–5.09 C ha⁻¹ yr⁻¹). The shift from CM to RC significantly raised soil carbon sequestration (0.17–1.58 C ha^–1 yr⁻¹). RC and RM both had gross primary production, resulting in a significant carbon sink (NEE: −3.96 to −3.71 t C ha⁻¹ yr⁻¹, −3.73 to −3.57 t C ha⁻¹ yr⁻¹, respectively). RC significantly decreased cumulative NEE (3.92 %–6.17 %) and increased gross primary production (6.53 %–7.27 %). RC transformed from CM and RM significantly raised soil easily oxidized organic carbon (6.28 %–14.60 %), microbial biomass carbon (2.82 %–11.20 %), and soil dissolved organic carbon (3.47 %–7.83 %) in 2022 and 2023, thereby resulting in higher soil respiration (1.95–5.09 C ha^–1 yr^–1). Within RC, the crab refuge area increased soil carbon sequestration and acted as a carbon source, while rice planting area acted as a carbon sink and counteracted the CO₂ emissions from the crab refuge area. Eco-economic benefit revealed that RC did not alter rice yield relative to RM, and produced 1.43–2.58 kg ha^–1 yr^–1 higher crab yield relative to CM, the highest economic benefits (3.64–4.48 10³ USD ha^–1 yr⁻¹), and the lowest NEE-scaled income (-1.25 to −1.21 10³ USD kg^–1C^–1 yr⁻¹) among the three treatments in both years.

Conclusions

RC enhanced carbon fixation capacity and optimized carbon sink capacity, producing the highest economic benefits and the lowest NEE-scaled income.

Implications or significance

RC balanced across rice and crab yields, net income, gross primary production and soil carbon sequestration, establishing a scalable model for climate-resilient agriculture.