Implications of Rock Fragments for Soil Quality Evaluation: Assessing Changes in a Gravelly Irrigated Soil Following No Till Adoption

ABSTRACT

Stony soils are increasingly being converted to intensive agricultural use, including irrigation. Conservation tillage can be adopted in these soils for soil protection and quality enhancement, but its assessment can be troublesome. Crop yields and the implications of rock fragments for soil quality indicators and for calculating C and N stocks were monitored under conventional and no-tillage in an experimental field recently converted to irrigation, on a soil with 40% rock fragments. Gains of up to 10 Mg C ha⁻¹ were observed in the tilled layer (0–30 cm) only with two years of irrigation, with no differences between treatments, although the vertical distribution of carbon (C) and nitrogen (N) was affected by the correction of the rock fragment content. The labile organic fraction stood as a sensitive indicator to management changes, even after rock fragment correction. Different methodologies used for rock fragment correction led to overestimations of 20% of organic C stocks.

KEYWORDS:

• Carbon sequestration
• rock fragments
• soil organic carbon

Acknowledgments

Prof. R. Espejo (Universidad Politécnica de Madrid, Spain) is thanked for his constructive revision of this manuscript. C.González, I. Urrutia, M. Apesteguia and I. García de Soto are thanked for their help during laboratory and field tasks.

Additional information

Funding

This work was supported by the Spanish National Institute of Agricultural Research (INIA) and FEDER European founds (Project RTA2010-00006-C03-03 and N. Arias Ph.D. scholarship).