Crop

Plant physiology

Fertilizer

Rice plant

Agronomy

Biology

Human fertilization

Nutrient

Ecology

Labelling

Botany

Biochemistry

Plant and Soil

Aim Quantification of total belowground carbon (C) input and allocation to various pools in rice–soil systems depending on plant age, chase period, and nitrogen (N) availability. Methods Rice plants with and without N fertilization were 13CO2 pulse labelled at tillering, elongation, heading, and filling stages and were destructively sampled after 6 h of labelling and at the final harvest. The allocation of C by rice was also generalized based on literature pertaining to 94 studies with respect to plant age and chase period. Results The C allocation in roots and soil strongly decreased with plant age. The literature review showed that C allocation to roots increased within the first 10 days of labelling and remained stable thereafter. Nitrogen fertilization had no effect on C allocation immediately after assimilation, but increased C remained belowground at 1.7-times that at final harvest. The total belowground net C input by one rice crop was 630–1080 kg C ha−1, including rhizodeposition of 160–330 kg C ha−1. Conclusion Multiple pulse labelling at various plant growth stages and taking multiple subsequent samples as well as nutrient availability should be considered for tracing C flows more accurately for precise C balance in rice paddy systems.

Allocation of assimilated carbon in paddies depending on rice age, chase period and N fertilization: Experiment with 13CO2 labelling and literature synthesis