Crops Bulletin

August 22, 2013  
 Issue 12    


Prepared by

Paul Kassel

Extension Field Agronomist



Serving Clay, Buena Vista, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Sac and Winnebago Counties



The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Many materials can be made available in alternative formats for ADA clients. To file a complaint of discrimination, write USDA, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call 202-720-5964.




Late Season Moisture Stress Effects on Corn: The corn crop takes about 60 days from pollination to maturity. Moisture stress during this time period can reduce yields.


Research has shown that moisture stress during the first 30 days of this 60 day time frame can reduce yields by up to 4% per day. This was not the case this year, as the relative cool weather from late July to mid-August minimized moisture stress effects on yield.


The recent change in the weather to hot and dry conditions and the general lack of rainfall has created concern. Fortunately moisture stress during the last 30 days of the grain fill time frame has less effect on yield. Moisture stress during day 30 to 45 of the grain fill time frame is 2-3% per day and that stress drops to 1-2% during the last 15 days of grain fill.


Late April and mid-May planted corn is currently in the dough stage. This crop would be expected to be mature in late September and would be affected less by this late season moisture stress. However, the late May planted corn/replant corn is in the blister stage and will be affected more by this moisture stress.


Yellow Beans: There have some areas of soybean fields that have declined in August. The affected soybeans are stunted with yellowed leaves. Leaf drop, reduced pod set and plant death may also occur. Some or all of the following factors that may be involved:

  • Poor root growth/dry soils/reduced nutrient update.
  • Potassium (K) deficiency - the edges of the lower leaves turn yellow.
  • Iron deficiency chlorosis - newest leaves turn yellow, veins are green.
  • Root rot - side and lateral roots are rotted.
  • Soybean cyst nematode (SCN) - look for cysts on the roots.
  • The SCN resistance and the general root vigor of the soybean variety.
  • Foliar symptoms of Sudden Death Syndrome or Brown Stem Rot may be evident - including leaf drop, & browning of leaf tissue between the veins.
  • Soil types with poor internal drainage including Harps and Canisteo

Consider soil testing these areas now or this fall for K levels, and SCN levels.

Prepared by Paul Kassel, Extension Field Agronomist

Phone: (712) 262-2264, Email: