419(pea (Pisum sativum L.), lentil, chickpea), and sunflower have been introduced in
this zone (Schillinger and Papendick 2008 ). In the high precipitation zone (>
450 mm annual precipitation), annual cropping is practiced and wheat is rotated
with grain-legume and oilseed crops.
Much has been written about dryland agriculture in North America (Baumhardt
and Salines-Garcia 2006 ; Cochran et al. 2006 ; Hansen et al. 2012 ; Schillinger et al.
2006 ). This chapter seeks to add to the established literature by highlighting some
new understanding, issues, and innovations that have not been widely reviewed. In
this chapter, we have discussed (1) the role of integrated pest management for her-
bicide resistant weeds, (2) diversification of crop rotations, including oilseed crops
produced for biofuels, (3) understanding effects of residue management on soil car-
bon dynamics, and (4) the application of models to aid decision making.
2 Integrated Weed Management as an Approach to Deal
with Herbicide Resistant Weeds
Retaining crop residues at the soil surface with no-till production systems has
proven to be critical to the success of modern dryland agriculture in North America.
The adoption of no-till production systems by many dryland farmers has greatly
reduced soil erosion by wind and water, preventing a repeat of the infamous decade
of severe wind erosion in the 1930s, despite subsequent drought conditions that
were more severe and longer in duration than in the 1930s. Additionally, no-till
production systems have increased soil water storage and retention compared to
tilled production systems. This increase in stored soil water has allowed dryland
farmers to increase cropping intensity and diversity, which has accrued many ben-
efits including increases in grain and biomass yields on an annual basis (Peterson
et al. 1996 ; Norwood 1994 ; Jones and Popham 1997 ), net returns to producers
(Peterson and Westfall 2004 ), and potentially active surface soil organic C and N
(Peterson et al. 1998 ). Diverse cropping systems also effectively controlled winter
annual grass weeds in winter wheat (Daugovish et al. 1999 ) and reduced yield loss
in wheat resulting from soil borne disease (Krupinsky et al. 2002 ). No-till dryland
cropping systems are heavily reliant on herbicides for weed control. This reliance
on herbicides makes no-till production systems particularly vulnerable to the rap-
idly increasing problem of herbicide resistance in weeds.
2.1 Extent and Occurrences of Herbicide Resistant Weeds
We have been selecting for weed biotypes with resistance to herbicides ever since
the commercial introduction of the synthetic organic herbicides in the late 1940s.
The first documented cases of herbicide resistant weeds in North American dryland
wheat production were reported in 1987. Kochia [Kochia scoparia (L.) Schrad.],
Dryland Agriculture in North America