by Wayne Flanary, regional agronomist
The wet weather has caused many of our crops to be shallow rooted and with hot temperatures, crops are stressed. The rain has been abundant and water is seeping out of the hillsides and in river bottoms, crops are yellow because of saturated soils.
The wet weather has resulted in the shallow crop roots. Roots do not grow deep into soils saturated with water. Saturated soils cause a lack of oxygen in the soil as all the voids are filled with water. Roots need oxygen to grow and take up nutrients and water.
Roots will move deeper as water percolates deeper into the soil. This allows for oxygen to move into the soil filling the voids left from downward moving water. Roots of crops that remain in saturated soils will grow very poorly and exhibit nutrient deficiencies. Plants are not able to take up adequate amounts of nutrients.
Now combine the shallow crop roots with hot weather. Hot temperature conditions increase plant respiration. The plant respiration rate doubles for every 13 degrees F. according to Dr. Thomison, Ohio State Extension. This rapid respiration requires increased nutrient and water uptake which shallow roots can adequately supply. Plants may wilt under these conditions even though there is plenty of water.
Also, hot nights cause the plants to use sugars from photosynthesis made during daylight to be used for respiration at night. This means there is less sugar available for developing kernels. This energy is used by the plant for respiration. Dr. Wiebold, University of Missouri Extension, indicates ideal night temperatures to maximize yields of both corn and soybeans are in the mid-60s.
The highest yields in Northwest Missouri are during times of adequate, timely rains and cool night-time temperatures. However, this year, we have a lot of variability of crop conditions which will impact harvest yields. In places, where we planted early this year and have good water drainage, we have outstanding crops; whereas in other fields, where water has injured crops, harvest yields will be severely reduced.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.
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