Continuous maize cropping accelerates loss of soil organic matter in northern Thailand as revealed by natural 13C abundance

Abstract

Aims: The loss of soil organic matter (SOM) has widely been reported in the tropics after changing land use from shifting cultivation to continuous cropping. We tested whether continuous maize cultivation accelerates SOM loss compared to upland rice and forest fallow.Methods: Because litter sources include C4 plants (maize in maize fields and Imperata grass in upland rice fields) in Thailand, C3-derived and C4-derived SOM can be traced using the differences in natural 13 C abundance (δ 13 C) between C3 and C4 plants. We analyzed the effects of land use history (cultivation or forest fallow period) on C stocks in the surface soil. Soil C stocks decreased with the cultivation period in both upland rice and maize fields. Results:The rate of soil organic carbon loss was higher in maize fields than in upland rice fields.The decomposition rate constant (first order kinetics) of C3-plant-derived SOM was higher in the maize fields than in the upland rice fields and the C4-plant-derived SOM in the forest fallow.Soil surface exposure and low input of root-derived C in the maize fields are considered to accelerate SOM loss. Soil C stocks increased with the forest fallow period, consistent with the slow decomposition of C4-plant-derived SOM in the forest fallows.Conclusions: Continuous maize cultivation accelerates SOM loss, while forest fallow and upland rice cultivation could mitigate the SOM loss caused by continuous maize cultivation.

Decreasing Soil Organic Carbon in Maize Cultivated Soil in Lowland Northern Thailand: Evidenced by the Interactions between Nutrients and Dissolved Organic Carbon

“…Increased substrate availability and microbial abundance, along with temperature, contribute to high rates of organic carbon pool decomposition [80]. These results are consistent with those of other studies on how maize cultivation in Thailand accelerates soil organic carbon loss owing to differences in natural 13 C abundance between C3 and C4 plants [10]. This leads to higher decomposition rate constants and a decline in soil fertility, which ultimately leads to land degradation [4].…”

“…Maize cultivation in Northern Thailand causes a decline in soil fertility and long-term land degradation [4,8]; due to intensive monocropping patterns [9]. Continuous maize cultivation accelerates soil organic carbon loss owing to the differences in natural 13 C abundance between C3 and C4 plants [10]. Maize growers are encouraged to employ integrated land-use Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s).…”

The difference in soil organic carbon distribution between natural and planted forests: A case study on stony soils mountainous area in the Upper Min River Arid Valley, China

“…Land‐use conversion can affect SOC distribution by altering the soil structure and properties (Collier et al, 2021; Özkan & Gökbulak, 2017; Romanyà & Rovira, 2011; Trigalet et al, 2016; Zhao et al, 2019). Several studies indicated that converting forestland and grassland into cropland could result in SOC loss (Bonini et al, 2018; Fujii et al, 2022; Post & Kwon, 2010; Ramesh et al, 2019). In contrast, returning farmland to forestland and grassland might improve soil structure and SOC accumulation (Shi et al, 2019; Thibault et al, 2022).…”