The Effect of Conservation Agriculture On Soil Fertility in Northern Syria.

The economic and environmental benefits of conservation agriculture (CA) are widely documented in many different parts of the world. However, in the Central and West Asia and North Africa adoption of zero-tillage (ZT), crop residue retention and diversified rotations have been slow. Three long term field experiments have been running at Tel Hadya, Syria (one since 1998 and two since 2006) investigating various tillage, time of sowing, crop rotation, crop residue retention and fertilizer N treatments. The soil is a very fine, montmorillonitic, thermic, chromic calcixerert. In general grain yields of wheat, barley, lentil and chickpea under zero-tillage were comparable or greater than those of conventional tillage treatments, and in most years there was a significant increase in yield with early sowing, especially in cereals. Various soil fertility measurements were conducted within these experiments between 2008 and 2012 and results showed that the increase in yields associated CA systems can be partly attributed to improved soil fertility. Moderate increases in organic matter, extractable phosphate, water-stable soil aggregates (0.5-2.0mm), and water infiltration capacity were measured in some of the ZT and crop residue retention treatments. The carbon sequestration rate associated with increased soil organic matter was in the range of 0.27 to 0.30 Mg C/ha/yr, and this rather modest increase was probably due to low to moderate crop productivity and a reasonable starting soil organic matter content of about 1.3 percent. No effects of tillage or residue retention were measured on soil mineral N, microbial biomass, bulk density or moisture retention.