435(Machado 2011 ; Brown and Huggins 2012 ), decreased soil health and crop produc-
tivity. The same trend has been observed in other agricultural systems worldwide
(Lal 2004 , 2006 ). Restoring SOM that has been lost due to years of fallow and
intensive tillage is among the greatest sustainability challenges for dryland cropping
in North America and is especially challenging because of the low biomass produc-
tion in dryland areas (Aase and Pikul 1995 ; Brown and Huggins 2012 ; Liebig et al.
2004 ; Lloyd et al. 2013 ). Application of current research and new research must
address soil health as affected by management systems such reduced tillage, no-
tillage, increased cropping intensity, cover cropping, and soil amendments.
Application of manures, biosolids, and biochar have tremendous potential to
increase SOM and ecosystems services to improve soil health in dryland crop land.
In addition to field research, use of cropping systems models can provide direction
and guidance on how to improve management practices.
Increasing cropping system diversity is a high priority for dryland cropping sys-
tems in North America. While dryland cropping systems in the Northern Great
Plains have been diversified in recent decades, much of the rest of the dryland crop-
ping region in North America is very limited in cropping system diversity. The tra-
ditional wheat-summer fallow rotation is widely practiced, resulting in declining
soil health, wind and water erosion, low precipitation use efficiency, and low eco-
nomic diversity. Work is needed for genetic improvement and variety development
of alternative crops and how to fit alternative crops into dryland crop rotations for
various dryland cropping regions of North America. Among the improvements to be
develop are crops that produce quality residues that reduce soil loss and increase
potential for sequestration of soil carbon. Both experimental and modelling research
can be used to advance cropping system diversification. There is especially a need
for viable pulse crops adapted to the conditions of the Central and Southern Great
Plains. This effort must include development of markets for alternative crops and
overcoming barriers limiting producers from diversifying crop rotations.
Gains in the diversification and intensification of the traditional wheat-summer
fallow rotations have been made largely by improving precipitation storage and use
through adoption of reduced tillage or zero-till systems (Aase and Siddoway 1980 ;
Aase and Reitz 1989 ; Cochran et al. 2006 ). Maintaining the benefits of these reduced
and no-till systems is being threatened by weeds, insect pests, and diseases that are
harbored in the crop residues. For example, crop damage from the wheat stem saw-
fly, Cephus cinctus Norton (Hymenoptera: Cephidae), to wheat has increased with
increasing adoption of no-till (Weaver et al. 2009 ). Similar observations have been
made for crop diseases and weeds that have a competitive advantage in no-till envi-
ronments. Understanding and adoption of integrated pest management practices to
manage pests and diseases as a result of increasing no-till production is of high
priority.
Dryland Agriculture in North America