Assessment of the responses of soil pore properties to combined soil structure amendments using X-ray computed tomography

Yonghui Yang,Qingyuan Han,Jicheng Wu,Shiwei Zhao,Fang He,Chun Chen,Xiaoying Pan

doi:10.1038/s41598-017-18997-1

Abstract

Soil amendments, such as straw mulch, organic fertilizers and superabsorbent polymer (SAP), are extensively applied to improve soil structure and porosity, and we reported the functional consequences of the individual application of these amendments in our previous study. However, whether combined amendments are more effective than their individual applications for improving soil pore structure is unknown. Here, we conducted X-ray computed tomography (CT) scanning on undisturbed soil columns to investigate the efficiency of two-amendment application, including straw mulch and organic manure, SAP and organic manure, or SAP and straw mulch, for improving soil pore properties and pore distribution. The X-ray CT technique allows us to accurately determine the number, morphology, and location of macropores (>1 mm in diameter) and smaller pores (0.13–1.0 mm). Compared to the control treatment, which showed the lowest increase in soil porosity, all the combined treatments led to an increase in the numbers of both macropores and smaller soil pores, causing a significant improvement in soil structure and porosity. Among these treatments, the application of both straw mulch and organic manure was the most effective for improving soil porosity and soil physical structure.

Highlights

Soil structure amendments, such as straw mulch, organic manure, and superabsorbent polymer (SAP), have been widely applied to improve soil organic matter, fertility[1] and soil structure[2]
The results clearly reveal that the application of two soil amendments was more effective than a single amendment in the improvement of soil pore parameters, represented as pore number, porosity and circularity
Our results obtained from cutting ring approaches suggest that the application of a combination of two soil amendments is a good strategy to synergize the effects of organic matter to improve the field capacity, total porosity, capillary porosity and non-active porosity and reduce the bulk density and aeration porosity

Summary

Introduction

Soil structure amendments, such as straw mulch, organic manure, and superabsorbent polymer (SAP), have been widely applied to improve soil organic matter, fertility[1] and soil structure[2]. CT scanning has been applied to the study of soil pore properties[16,17] and pore distribution[18,19,20] This technique has been introduced to accurately measure the number, size, and location of macropores (>1 mm in diameter)[21]. Our previous study indicated that when soil amendments are used alone, such as straw mulch, SAPs and organic manure, they can significantly improve the characteristics of soil pores and pore distribution in soils[30]. The objectives of this study were to (1) evaluate differences in the CT-measured characteristics (number of pores, porosity, and circularity) of >1.0 mm pores, 0.13–1.0 mm pores and ≥0.13 mm pores (total pores) among treatments and (2) determine whether an observed correlation exists between CT-measured pore parameters and conventional cutting ring approach-derived characteristics (e.g., soil bulk density, field capacity, water-stable aggregate content, and porosity)

Objectives

Methods

Results

Discussion

Conclusion