Watering Young Corn and Soybeans

What started out as a decent chance of rain today (Thursday) is quickly turning into isolated pop-up showers for a lucky few for most of the state except east Tennessee.  The good news is our crop is young, water needs are low, and I think our corn and bean crops are in decent shape water-wise.  But, as temperatures warm up and plants begin to grow, more water will be needed to support plant growth.  Our earliest planted corn is at or near V-6 and some irrigation may be needed where rains were missed last week.  I have discouraged irrigating very young corn and beans where moisture levels are still adequate because we tend to over-irrigate young corn and beans when we start this early.  But with rain chances waning again, I do think adding supplemental water in specific situations makes sense– think of it as a kick start to the crop but don’t over do it on the water– especially on beans.   Some of these are no-brainers but consider adding some water in the following situations:

  • To get soybeans out of the ground.  Windy conditions have zapped soil moisture in the top 1 inch of soil.  Irrigation will ensure uniform emergence of the crop which will help the crop progress at a similar rate throughout the season.
  • To activate PRE herbicides.  There is no need to let these products sit on top of the ground if irrigation is an option.  Apply 0.5” of water to incorporate most corn and soybean herbicides.
  • To incorporate urea or surface applied UAN.  Data suggests that as little as 0.2” of irrigation will incorporate surface applied fertilizer into a silt loam soil.   If fields have a lot of corn residue, bump the amount up to at least 0.5” of water.
  • Corn was planted around the 20th of March and fields are at or approaching V-6.   I would suggest watering about 1” to kick start the crop and keep water deficit from starting early.  The table below lists water needs by crop stage/timing for early season corn and soybean to give some idea on water needs during the early season.

 

 Corn   Stage  Comments

Inches per Week  Used by Crop

Seedling About first 30 days out of the ground

0.70

Rapid Plant Growth 30-60 days (V6- pre tassel)

0.70 – 1.40

Higher rate on bigger corn

     
 Soybean   Stage Comments

Inches per Week

Used by Crop

Seedling Get crop out of the ground but don’t overdo it.

0.35 – 0.70

Early bloom (R1) April planted MG 3, 4— About 40 days after plantingMay planted MG3– about 30 days after planting; About 40 days   after planting MG 4 and indeterminate MG5’sMay planted determinate 5’s—about 70 to 80 days after planting

1.4

Early Pod fill (R5) 50-65 days after planting for indeterminate varieties

2.10

R1-R6 (how long to water once irrigation begins) About 60-70 days for indeterminate varieties depending on maturity   and planting date  

 

 

 

 

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