Drought Tolerance
PORTAGEVILLE, MO.
Drought stress is a major limiting factor to
crop yields, even in sub-humid regions like
the Missouri Bootheel. Due to common factors
such as soils with low available water holding
capacities, even short-term drought can
impact yield leading producers of rainfed crops
to convert to irrigated production. Irrigated
farmers are affected by drought as well. Delays
in irrigation are common due to equipment
maintenance, other demands on labor, the need
to allow time for pesticide and/or fertilizer applications,
and water supplies shared among
multiple fields and/or crops.
Seed companies have devoted much effort to
improving drought tolerance in crops. Pioneer1
introduced non-transgenic “AQUAmaxTM” corn
hybrids in 2011 and Monsanto plans to release
biotech drought-tolerant corn in 2013. Similar
efforts are ongoing with other crops, including
cotton. In some cases, conventional plant breeding
strategies are used to enhance desirable
traits such as improved nitrogen fixation in soybean
or a longer silking window for corn. In
other cases, transgenic breeding programs identify
plants with greater tolerance to drought
stress and transfer selected genes from those
plants into agronomic crops.
While the focus for improved drought tolerance
has been on production in more arid climates, it
can benefit Mid-South producers as well. It
could allow a longer time between irrigations, increasing
the chances of rain occurring before irrigation
is necessary. Improvement in drought
tolerance should lead to reduced irrigation requirements
for Mid-South crops, which would
reduce the water pumped from the region’s
aquifers as well as the energy required to pump
and apply the water. However, research is
needed to determine the similarities and differences
in optimal irrigation management between
currently grown crops and those with improved
drought tolerance. Managing irrigation on
drought-tolerant crops using the present recommendations
based on current cultivars and
hybrids will not result in water savings.
USDA-ARS scientists began research at the
Fisher Delta Research Center to study the similarities
and differences between a Pioneer
AQUAmax hybrid and another hybrid recommended
for southeast Missouri. The spatiallyreferenced
properties of temperature,
reflectance, and height of the crop canopy along
with the temperature and relative humidity of
the air above the canopy are monitored during
the growing season in both irrigated and nonirrigated
plots. The large-scale plots will be harvested
with a yield monitor so that in addition
to total yield, the spatial variability of the yield
can be related to spatial differences in soil properties
and the crop properties observed during
the growing season. Future research will include
additional hybrids and other drought-tolerant
crops. The results of this research will provide a
better understanding of drought-tolerant crops
produced in a sub-humid climate and how recommendations
for their management will need
to differ from current recommendations. Δ
1 Mention of trade names or commercial products
is solely for purpose of providing specific information
and does not imply recommendation
or endorsement by the U.S. Department of Agriculture.
DR. EARL VORIES: Agricultural Engineer,
USDA-Agricultural Research Service