Abstract
Fertilization practices change soil organic carbon content and distribution, which is relevant to crop rotation and soil aggregates. However, how fertilization management under corn–soybean rotation affects soil organic carbon and aggregate stability at different soil depths in Mollisols is unclear. The effects of 6–yr fertilization under corn–soybean rotation on aggregate stability, soil organic carbon content and storage, and size distribution in soil aggregates were investigated. Five different fertilization practices were carried out in 2013: corn and soybean without fertilizer; corn with chemical fertilizer, soybean without fertilizer; corn with chemical fertilizer, soybean without fertilizer, returning the corn and soybean residues; corn and soybean with chemical fertilizer; and corn with chemical fertilizer, soybean with farmyard manure. Compared with corn and soybean without fertilizer, returning the corn and soybean residues increased bulk SOC content, and enhanced mean weight diameter and geometric mean diameter values at 0–10 cm because of increased water–stable aggregates (WSA) larger than 2 mm proportion and decreased WSA<0.053mm proportion. Simultaneously, corn with chemical fertilizer and soybean with farmyard manure increased bulk soil organic carbon content but reduced mean weight diameter and geometric mean diameter values at 0–20 cm due to increased WSA<0.053mm proportion and decreased WSA>2mm proportion. Altogether, the application of consecutive returning crop residues and chemical fertilizer in alternate years is the most favorable approach for soil organic carbon accumulation and aggregate stability at 0–10 cm under corn–soybean rotation in Mollisols.
Highlights
Crop growth and development are heavily dependent on soil structure
Soil aggregates and their stability are regarded as indicators of soil structure, which is identified by mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D) [1]
Among the five fertilization practices, the highest and lowest proportion of water–stable aggregates (WSA) sizes did show a different tendency in the three soil depths
Summary
Crop growth and development are heavily dependent on soil structure. Soil aggregates and their stability are regarded as indicators of soil structure, which is identified by mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D) [1]. Especially macroaggregates (>0.25 mm) protect soil organic carbon (SOC) from decomposing and degrading [3]. Filho et al confirmed that soil is less aggregated in the lower organic carbon regions [6]. The amount of crop residue returned to the soil and the chemical substances released from plants influence the stability, rate of formation, and turnover of aggregates [7,8]
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