DOI: 10.5061/dryad.stqjq2cd9
title: Data from: Impacts of long-term tillage and fertilization on soil carbon stock and aggregate stability in tropical agriculture

description: This study investigates the effects of tillage and fertilization on
 changes of soil organic carbon (SOC) stock in a 46-year long-term field
 experiment in Thailand. The economic cropping system was maize-mung bean
 rotation. The experiment treatments included plots with tillage, no
 tillage, chemical fertilizer, organic amendment, and combination of
 chemical and organic fertilizer. No-tillage significantly increased soil
 aggregate stability [water-stable aggregates (WSA), mean weight diameter,
 and geometric mean diameter]. However, only rice straw applications
 enhanced WSA. SOC stocks of the same soil mass ranged from 21.7 to 40.1 Mg
 C ha-1. The highest SOC stock (40.1 Mg C ha-1) and sequestration rate
 (0.40 Mg C ha-1 year-1) were observed in no-tillage plots with cow dung
 and chemical fertilizer. These findings underscore the significant
 potential of integrated practices involving no-tillage and organic
 amendments to improve soil structure and carbon sequestration in tropical
 agricultural systems.
description: # Impacts of long-term tillage and fertilization on soil carbon stock and
 aggregate stability in tropical agriculture
 [https://doi.org/10.5061/dryad.stqjq2cd9](https://doi.org/10.5061/dryad.stqjq2cd9) ## Description of the data and file structure This data showed the average of **soil organic carbon** (SOC) **stock**, **water-stable aggregate** (WSA), **mean weight diameter** (MWD), and **geometric diameter** (GMD). **Study site and experimental design** The 46-year long-term experiment plots in Lopburi province were used in the current study. These plots were established by the Department of Agriculture in 1976. The soil type was classified as Typic Paleustults (USDA) and the climate was categorized as tropical savanna (Aw). The soil texture was classified as loam (sand: 477 g/kg, silt: 386 g/kg, clay: 137 g/kg). The dominant minerals in the whole soil and clay fraction were quartz and kaolinite. Maize (*Zea mays*, variety: Nakhon Sawan 3) and mung beans (*Vigna radiada*, variety: Chainat 84-1) were cultivated under 12 treatment conditions, with each crop grown once per year. Three treatments were randomly assigned in a factorial design: **tillage practice** (tillage or no-tillage); **chemical fertilizer** (none chemical fertilizer or chemical fertilizer applied at rates of 93.75 kg N, 31.25 kg P, and 31.25 kg K/ha); **organic amendment** [none organic amendment, rice straw applied (3.125 Mg/ha), or cow dung  (6.25 Mg/ha)]. Each plot measured 5.25 m x 6 m. In all treatments, crop residues after harvest from each plot were left on the soil surface annually as a common practice. **Soil sampling and soil analysis** Triplicate soil sampling was taken from at a depth of 0–20 cm in December 2022. Soil bulk density was determined using the clod method. A separate disturbed soil samples intended for OC content was collected and thoroughly dried and sieved through a 2.0 mm mesh. The OC was analyzed using the combustion method at 950 °C with a CHN elemental analyzer (LECO 628).  This study assessed aggregate stability using soil WSA (%), MWD (mm), and GMD (mm). Six wet sieves (&gt;2.00 mm to &lt;0.053 mm) were used. A 100 g soil sample (&lt;8 mm) was carefully placed in the sieving apparatus, immersed in water for 10 minutes, and sieved for another 10 minutes (38 mm stroke, 30 strokes/min). Aggregates were then washed, oven-dried at 40°C. WSA was the percentage of aggregates &gt;250 µm, MWD was the weighted mean size, and GMD was the exponential mean based on size distribution.  SOC stock was calculated by using equivalent soil mass (ESM) in Eq. 1: SOC stock (Mg C/ha) = SOC (g C/kg) x bulk density (Mg/m3) x depth with adjusted soil surface depth (m) x 10 (Eq. 1.)