Skip to main content

Competency Area 1: Crop Adaptation

PO 3. Understand the adaptation of major Northeast crops to extremes in precipitation on well-drained, poorly drained, and moderately well drained soils.

Adaptation of forage crops to precipitation extremes
Legumes with deep tap roots are better able to obtain water in droughty conditions.
Grasses with a shallow root system and the ability to go dormant in summer are also better adapted to precipitation extremes. Clovers and trefoil have a physiological adaptation to low O2 availability when soils are poorly drained.
Reed canarygrass can tolerate both droughty and very wet soil conditions across soil drainage classes.

Amount of summer or annual precipitation is a key component to crop adaptation
Corn-requires about 15 to 18 inches of precipitation from May through September for maximum yields, especially on droughty soils. On deep soils with high water-holding capacity, corn can produce maximum yields on 12 to 15 inches of precipitation during this time period. Corn is most sensitive to drought from 2 weeks before to 3 weeks after silking, which occurs in July and early August. Drought at this time can reduce corn grain yields by 50% and silage yields by 35-50%. Wet July conditions usually result in very high corn yields.

Wheat is a very drought tolerant crop and almost never suffers from drought stress in the Northeast. Maximum yields can be attained with only 5- 6 inches or precipitation from April through June on silt loam and clay loam soils and with 7-8 inches on very droughty soils. In fact, yields are lower when spring conditions are wet because of increased disease pressure and less N-use efficiency of fertilizer N.

Soybeans also require about 15-18 inches of precipitation from May through September on most soils. Soybeans are most sensitive to drought during the pod and seed-filling periods, which coincides with the month of August. Soybean yields can be reduced by 50% if August (the pod and seed-filling periods) is dry on droughty soils. Yields are reduced by about 25% on deep soils with high water holding capacity with dry August conditions.

Water needs of a crop follow a bell-shaped curve
In the early vegetative stages of development the plant has low water needs (0.05 in./day)
When rapid vegetative development begins, water requirements increase almost daily (0.05 to 0.20"/day) Reproductive development (silking, heading out, etc.) requires the highest amounts of water (0.20"/day). Unfortunately, corn is most sensitive to drought at this time. During grain-filling, water requirements decrease almost daily starting about 3 weeks after flowering. Water use by a crop closely follows its green leaf area.