Agriculture Reference
In-Depth Information
Microbial-induced drought resistance is a potentially important technology for devel-
oping countries that are semiarid and that have crops that are regularly prone to drought
stress. However, research on the interactions of microorganisms with plants and drought
resistance is in its infancy.
2.2.5 Companion woody rhizospheres
Parkland agroforestry to some degree is practiced by farmers in tropical regions by allow-
ing trees that can improve soil quality to grow in their fields. However, trees growing in
farmers' fields may compete with crops, and there has been limited success in adoption of
such systems (Buresh and Tian, 1998; Rhoades, 1997). However, Dick and coworkers dis-
covered the importance of another prominent woody component in West Africa—native
shrubs—that has largely been unrecognized for its potential to improve agroecosystems.
The two species found throughout the Sahel are
Piliostigma reticulatum
(PR) and
Guiera
senegalensis
(GS), which regrow after the rainy, summer cropping period and are unfortu-
nately cut and burned just prior to the next cropping (rainy) season. Research findings so
far have shown shrubs
• Are the single most important source of C inputs (Lufafa, Diédhiou, et al., 2008;
Lufafa, Wright, et al., 2008) in farmers' fields;
• Increase soil quality and nutrient availability and could regenerate landscapes (Dossa,
2007; Dossa, Baham, et al., 2009; Dossa, Khouma, et al., 2009; Dossa et al., 2010);
• Are doing “hydraulic lift” (Kizito et al., 2012) (passive movement of water through
roots from moist subsoil to dry surface layers [Caldwell et al., 1998]);
• Increase groundwater recharge during high-rainfall periods (Kizito et al., 2007);
• Maintain greater microbial diversity in the rhizosphere year around (presumably
due to hydraulic lift) than soil outside the influence of the rhizosphere (Diedhiou et
al., 2009);
• Are noncompetitive with crops for water (Kizito et al., 2007);
• Can be managed nonthermally, with unburned residue having positive effects on
soils;
• Increased yields of peanut and millet by more than 50% over plots without shrubs
(3 years of field testing) (Dossa, 2007).
Developing woody species companion plants has great potential throughout semiarid
developing countries to restore degraded landscapes, buffer desert encroachment, and
increase crop productivity.
agroecosystems context
It will be important as research proceeds that it is put within a regional and farm-level/
cropping systems context. To emphasize this, one example is provided here with regard to
manipulation of biocontrol microorganisms.
Larkin (2008) compared various biostimulants and known microbial control agents on
potato diseases. Although all of them had measurable effects on soil microbial properties
in the field, in no case did any of these reduce disease in continuous potato plots: Rather
effective controls only occurred in certain crop rotations. These results indicated that
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