Does Organic Residue Quality Influence Carbon Retention in a Tropical Sandy Soil?

Abstract

The influence of residue quality on soil organic C (SOC) retention has been called into question. A field experiment in Northeast Thailand, in which contrasting quality organic residues were applied yearly for 13 yr, was used to determine quantities, locations, and stability of SOC in the soil matrix and identify residue quality parameters affecting SOC stabilization in a tropical sandy‐textured soil. Total organic C (TOC) content was highest in intermediate‐quality tamarind (Tamarindus indica L.) at 3.58 g kg−1 (intermediate N, lignin, and polyphenol contents), followed by groundnut (Arachis hypogaea L.) stover at 2.63 g kg−1 (high N), dipterocarp (Dipterocarpus tuberculatus Roxb.) at 2.63 g kg−1 (low N, high lignin and polyphenols), and rice (Oryza sativa L.) straw at 1.77 g kg−1 (high cellulose). Microaggregates (Mi) (0.053–0.25 mm) stored the highest C content (34–49% of TOC), with tamarind having the highest C content. Carbon in large macroaggregates (>2 mm), small macroaggregates (0.25–2 mm), and free organic matter (>0.053 mm) was significantly positively correlated with C, lignin, and polyphenols. Carbon in microaggregates and fine particles (<0.053 mm) was significantly negatively correlated with C/N ratio. Soil fraction C was negatively correlated with residue cellulose contents. Protected C lost through mineralization in Mi was lower in tamarind (7% Mi‐C) followed by groundnut (9.5%), dipterocarp (17.7%), and rice straw (18.6%). It was significantly positively correlated with cellulose and C/N ratios but negatively correlated with N contents. Possible mechanisms of aggregate formation are based on microbial synthesis of both persistent (humic substances) and transient (polysaccharides) binding agents as influenced by residue quality. The results showed clearly that residue quality plays an important role in SOC accumulation in tropical sandy soils.

Substrate quality influences organic matter accumulation in the soil silt and clay fraction

“…The initial C-522 deficiency of our soil clay fraction likely explains why C accumulates following substrate 523 addition; where as other soils near their C-saturation do not (Castellano et al, 2015, 524 citations therin). Consistent with our results, Puttaso et al (2013) found sandy soils 525 (which presumably also had C-deficient clay fractions) accumulated C in the fine mineral 526 fraction and that the quality of litter inputs influenced the magnitude of C accumulation. 527…”

Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept

“…Thus, changes in aggregate turnover may increase or decrease the pool of microaggregate‐occluded SOM, thereby altering the C saturation deficit (Plante & Mcgill, ). Recent evidence suggests high‐quality litters hasten short‐term aggregate turnover (Chivenge et al ., ,b; Puttaso et al ., ). However, longer duration studies find that litter quality has little effect on microaggregate‐occluded SOM pools (Chivenge et al ., ,b; Puttaso et al ., ).…”

“…Recent evidence suggests high-quality litters hasten short-term aggregate turnover (Chivenge et al, 2011a,b;Puttaso et al, 2013). However, longer duration studies find that litter quality has little effect on microaggregate-occluded SOM pools (Chivenge et al, 2011a,b;Puttaso et al, 2013). In the future, it will be important to separate short-term litter quality effects on aggregate turnover from relatively long-term effects of litter quality on pools of microaggregate-occluded SOM.…”

Response of ammonia-oxidizing bacteria and archaea to biochemical quality of organic inputs combined with mineral nitrogen fertilizer in an arable soil

“…However, this speculative assumption clearly raises the need for prospective research if distinct soil types with their individual soil textures and aggregation processes and hence SOC stabilization are more responsible for the determination of the composition of microbial communities including ammonia-oxidizers over other factors such as the use of contrasting organic soil amendments . Additionally, it will be necessary to enhance the currently limited understanding on the potential of biochemically contrasting organic inputs and accompanied microbial decomposition processes to shape the physical properties (e.g., aggregation) of soils (Kunlanit et al, 2014;Puttaso et al, 2013).…”