Effects of Zero Tillage and Residue Retention on Soil Quality in the Mediterranean Region of Northern Syria

Jihad Abdalla,Pierre Hayek,Ali Hajdibo,Osama Douba,Rousheen Haj-Abdo,Rolf Sommer,Atef Haddad,Yaseen Khalil,Lona Van Delden,Ahmed Khoder,Kayoko Shimonaka,John Ryan,George Estefan,Colin Piggin,Muhammad Ansar,David Feindel

doi:10.4236/ojss.2014.43015

Abstract

Zero-tillage (ZT) and crop residue retention on thesoil surface—two components ofConservation Agriculture (CA)—have been identified as promising management practices for sustainableagri- cultural intensification forsome time. However, CA technology uptake by farmers in the dry areas of WestAsia and North Africa (WANA) has yet to happen large-scale, even though thepositive im- pact on yield has beendemonstrated repeatedly. To explain the observed consistent increases in cropyield under ZT, a range of soil quality indicators were regularly monitoredduring 2008 to 2012 in the long-term ZT/CA trials at the headquarters of theInternational Center for Agricultural Research in the Dry Areas (ICARDA) innorthern Syria. Results showed that CA had a positive im- pact on soil fertility. This was measurable by higher soil organicmatter (SOM) and microbial bio- mass contents, increasedlevels of extractable phosphate, sometimes (but not always) higher amounts oflarger water-stable soil aggregates, increased soil infiltration capacity andsoil water retention. The buildup of SOM and associated carbon (C)sequestration was in the range of 0.29 Mg C/ha/yr, i.e. rather modest. High amounts of surface residues delayed thedesiccation of the topsoil during the fallow period, but could not diminish theoverall longer-term drying of the topsoil. The observed positive changes insoil quality were little, but nevertheless, in combination with the economicsavings that ZT offers, this type of agricultural intensification provides anattractive op- tion for farmers in WANA,from the standpoints of economy and ecological efficiency.

Highlights

The Mediterranean region has been cultivated for millennia and is the site of the evolution of settled agriculture and the center of origin of a range of important crops [1]
Agricultural production has intensified in the Mediterranean region, especially the increase with continuous cropping instead of fallow and application of mineral fertilizer
In addition to soil conservation, conservation agriculture (CA) systems in the majority of cases have been shown to increase the amount of soil organic matter (SOM), which improves soil quality and the environmental sustainability of agro-ecosystems

Summary

Introduction

The Mediterranean region has been cultivated for millennia and is the site of the evolution of settled agriculture and the center of origin of a range of important crops [1]. In a major shift from conventional production systems, conservation agriculture (CA) systems, embracing ZT for minimal soil disturbance, surface residue retention and crop rotation, have been adopted extensively in Australia, Canada, the USA and Latin America [8] [9]. This development has been driven by labor and energy savings, control of soil erosion, better soil moisture conservation [10] [11] [12] and the opportunity for earlier sowing and better yields. The build-up of SOM involves sequestration of carbon (C), which may contribute to mitigation of increasing atmospheric CO2 levels [13], even though the potential contribution may be limited [14] [15]

Methods

Results

Discussion

Conclusion