Abstract
Soil tillage can affect the stability and formation of soil aggregates by disrupting soil structure. Frequent tillage deteriorates soil structure and weakens soil aggregates, causing them to be susceptible to decay. Different types of tillage systems affect soil physical properties and organic matter content, in turn influencing the formation of aggregates. The objective of this study was to evaluate the effect of long-term tillage on soil aggregates and aggregate-associated carbon in a black soil of Northeast China and to identify the optimal conservation tillage in this system. This research was conducted on a long-term tillage experimental field established in 1983 at the Jilin Academy of Agricultural Sciences, Gongzhuling, China. Plots were treated with four tillage systems including no tillage (NT), spacing tillage (ST), moldboard plowing (MP), and conventional tillage (CT). We took samples every 10cm from 0-60cm depth and demonstrated that water-stable soil aggregates >0.25mm in diameter accounted for over 66.0% of total aggregates for all tillage treatments, and the percentage for the ST treatment was 34.5% higher than in the other treatments. The NT treatment had the highest effect at 0–10cm depth, while the effect for the ST treatment was highest at 0–30cm. SOC storage decreased with soil depth, with a significant accumulation at 0-20cm depth. Across treatments, aggregate-associated C at a depth of 0–10cm was higher in the NT and ST treatments than in the MP and CT treatments. The advantage of the NT treatment weakened with soil depth, while the amount of aggregate-associated C remained higher for the ST treatment. There were more macro-aggregates in the ST and NT treatments than in the MP and CT treatments, while the MP and CT treatments had more micro-aggregates. The sum of macro-aggregate contributing rates for soil organic C (SOC) was significantly superior to that of the micro-aggregates. Water-stable aggregates increased by 34.5% in the ST treatment, effectively improving the soil structure. Furthermore, 0.25–1.00 and 1–2mm aggregates had the highest SOC storage and responded rapidly to the various tillage treatments. Hence, they can serve as indicators for the long-term influence of different tillage treatments on the distribution of aggregates and SOC.
Highlights
Soil is considered the ‘skin’ of the earth [1], with soil organic carbon (SOC) as the protein that protects the ‘skin’ [2]
Our study concluded that conservation tillage can significantly increase the SOC content in soil, and that this effect is significantly stronger in spacing tillage (ST) and no tillage (NT) than in moldboard plowing (MP) and conventional tillage (CT) at 0-60cm depths
Our study suggests that different tillage treatments affected the water-stable soil aggregate distribution in the black soil in Northeast China
Summary
Soil is considered the ‘skin’ of the earth [1], with soil organic carbon (SOC) as the protein that protects the ‘skin’ [2]. SOC is a key indicator of soil quality [3], is the basis of soil fertility and function [4,5], and is important for cementing substances as part of the formation of soil aggregates. SOC affects the number and distribution of differently sized soil aggregates [6]. Soil aggregates are the basic ‘cells’ of the soil structure and play an important role in improving soil carbon sequestration and fertility [7]. Previous studies have demonstrated that the interaction between soil structure and aggregates determines the quality of the SOC pool. The combined application of chemical fertilizer and straw greatly improves SOC accumulation in water-stable aggregates of this size [12,13]
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