Abstract
Understanding carbon mineralization dynamics of organic amendments is essential to restore degraded lands. This study focused on the restoration potentials of tea-growing soils using organic materials available in tea ecosystems. The Selangor-Briah soil series association (Typic Endoaquepts) consisted of a high- (soil A) and a low-carbon (soil B) soils were incubated with different organic materials and released carbon dioxide (CO2) measured. Two kinetic models were applied to depict the mineralization process. Soil health parameters including microbial biomass carbon and nitrogen, dehydrogenase and catalase activities were determined to assess the restoration potentials. The parallel first-order kinetic model fitted well for all amendments. Gliricidia markedly enhanced the net cumulative CO2 flux in both soils. Charged biochar, tea waste and Gliricidia improved the microbial biomass carbon by 79–84% in soil A and 82–93% in soil B, respectively. Microbial quotients and biomass nitrogen were increased over 50 and 70% in amended soils, respectively. Dehydrogenase activity was significantly accelerated over 80% by compost, charged biochar and tea waste. Charged biochar remarkably increased the soil catalase activity by 141%. Microbial biomass, dehydrogenase and catalase activities, and cumulative CO2 flux were positively correlated (r > 0.452) with one another. The studied amendments showed greater potential in improving the soil quality, while charged biochar, raw biochar and compost enrich the soil recalcitrant C pool ensuring the soil health in long term. Even though biochar sequesters carbon, it has to be charged with nutrients to achieve the soil restoration goals.
Highlights
The depletion in soil organic matter (SOM) has become an inevitable consequence in many tropical regions, where intensive farming is practiced under present climate-changing scenarios [1]
Even though Cs is greater than Cf in general [54], we found Gliricidia showing a higher amount of faster decomposing materials than its resistant pool in soil A in line with Zaharah and Bah [56]
The addition of organic materials used in this study increased Microbial biomass C (MBC), microbial biomass N (MBN), soil respiration and soil enzyme activities in varying degrees
Summary
The depletion in soil organic matter (SOM) has become an inevitable consequence in many tropical regions, where intensive farming is practiced under present climate-changing scenarios [1]. Tea is an upland crop grown as a rainfed perennial mostly in tropical and subtropical regions where the soil has been continuously subjected to degradation. Most soils in most of the tropical tea-producing countries are highly weathered and continuously declining in SOM leading to poorer soil quality [3]. As a result of the continuous exploitation of tea cultivating lands over 150 years, soil degradation has become inescapable in the South and East Asian regions questioning the sustainability of tea cultivation in the future [4,5]. The degradation process has been further aggravated by unfavorable environmental factors including high rainfall and temperature arisen due to climate change and the continuous loading of agrochemicals [6]
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