Soil Organic Carbon Dynamics in Two Rice Cultivation Systems Compared to an Agroforestry Cultivation System

Ibonne Geaneth Valenzuela-Balcázar,José A Acosta,Ángel Faz,Efraín Francisco Visconti-Moreno

doi:10.3390/agronomy12010017

Abstract

After changes in tillage on croplands, it is necessary to assess the effects on soil organic carbon (SOC) dynamics in order to identify if soil is a sink or emitter of carbon to the atmosphere. This study was conducted in two plots of rice cultivation, where tillage and water management changes occurred. A third plot of native forest with Cacao trees was used as reference soil (agroforestry). For SOC balance estimation, measurement of organic carbon (OC) inputs was determined from necromass, roots, microbial biomass, and urea applications. CO2 and CH4 emissions were also measured. Results showed that the change in the use of irrigation and tillage in rice cultivation did not cause significant differences in OC inputs to soil or in outputs due to carbon emissions. Further-more, it was found that both irrigation and tillage management systems in rice cultivation com-pared with agroforestry were management systems with a negative difference between OC inputs and outputs due to CO2 emissions associated with intense stimulation of crop root respiration and microbial activity. The comparison of SOC dynamics between the agroforestry system and rice cultivation systems showed that an agroforestry system is a carbon sink with a positive OC dynamic.

Highlights

Soil constituents such as clay, humus, and microorganisms are the most important components for terrestrial ecosystems due to its multiple ecosystem services
After changes in tillage on croplands, it is necessary to assess the effects on soil organic carbon (SOC) dynamics in order to identify if soil is a sink or emitter of carbon to the atmosphere
As other studies [7,8], our results revealed that rice cultivation systems present the highest amounts of OC outputs and a negative budget (Table 5), which indicated that the rice crop had the highest carbon loss due to high CO2 emissions from soil microbial activity and mainly associated with greater respiration of the crop’s roots, as pointed out by Zornoza and collaborators in 2018 who observed a relationship in greenhouse gas emissions with crop stimulation through fertilization and irrigation water [51]

Summary

Introduction

Soil constituents such as clay, humus, and microorganisms are the most important components for terrestrial ecosystems due to its multiple ecosystem services. According to Smith and collaborators in 2018, agricultural soils changes in SOC are determined by the cumulative contributions of organic carbon (OC) from the crop, and when there are high returns driven by nitrogenous fertilizers and the fallow frequency is low, it can favor an increase in SOC [11]. This is a complex and dynamic process. The balance between inputs and outputs of organic carbon in the soil constitutes an assessment methodology to identify its functioning as a sink or as a carbon emitter in the ecosystem, allowing the evaluation and comparison of the dynamics of organic carbon in soils under different use and management systems [12,13]

Methods

Results

Discussion

Conclusion