Installing artificial macropores in degraded soils to enhance vertical infiltration and increase soil carbon content

Yasushi Mori,Kazuto Yamagishi,Atsushi Fujihara

doi:10.1186/s40645-014-0030-5

Yasushi Mori, Kazuto Yamagishi + Show 1 more

Open Access

https://doi.org/10.1186/s40645-014-0030-5

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Abstract

Of all terrestrial media (including vegetation and the atmosphere), soil is the largest store of carbon. Soils also have important functions such as water storage and plant support roles. However, at present, these characteristics do not fully function, because of, for example, climate-change-induced heavy rainfall would wash away the organic-rich surface soils. In this study, artificial macropores were introduced into exposed soil plots for the purpose of enhancing infiltration, and fibrous material was inserted to reinforce the macropore structure. As expected, the capillary force caused by the fibers drew surface water deeper into the soil profile before saturation. Additionally, the same capillary force promoted vertical transport, while micropores (matrix) enhanced horizontal flow. Our results show that infiltration was more effective in the fiber-containing macropores than in empty macropores. Additionally, our column experiments showed that artificial macropores reduced surface runoff when the rainfall intensities were 2, 4, and 20 mm · h−1 but not for 80 mm · h−1. In field experiments, soil moisture sensors installed at depths of 10, 30, and 50 cm responded well to rainfall, showing that artificial macropores were able to successfully introduce surface water into the soil profile. One year after the artificial macropores were installed, a field survey carried out to assess soil organic matter and plant growth showed that plant biomass had doubled and that there was a significant increase in soil carbon. This novel technique has many advantages as it mimics natural processes, is low cost, and has a simple structure.

Highlights

Soil, the largest of all terrestrial carbon stores, contains as much as three times the amount of carbon stored in vegetation and two times that stored in the atmosphere (Eswaran et al 1993)
We attempted to improve the process of infiltration in exposed soils by creating artificial macropores that mimic the natural macropore structure
To help restore poorly drained soils and enhance their organic matter levels, vertical infiltration was improved via the introduction of an artificial macropore with fibrous fillings

Summary

Introduction

The largest of all terrestrial carbon stores, contains as much as three times the amount of carbon stored in vegetation and two times that stored in the atmosphere (Eswaran et al 1993). Soils have important functions such as water storage and plant support roles. At the present time, these soil capabilities are progressively being weakened because of climate change (IPCC 2013). Meteorological measurements have shown that, in the last 30 years, heavy rainfall events in excess of 50 mm · h−1 have increased in Japan (The Japan Meteorological Agency 2013). Such heavy rains sometimes produce a crust or hardpan at the soil surface, which degrades infiltration.

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