Friday, June 18, 2010

Circles for Rice | Weekly Update

United States

Missouri, USA

Missouri, USA
This week, I will focus on some irrigation management issues that have been observed in the rice fields under center pivots.  The following situations have developed in the fields:

1. Case #1 - The rice team advises the grower to irrigate, but the grower "wants to wait for rain."  We all want to utilize the rain, but if the grower delays irrigation for two or more days, particularly on some of the lighter soils, we will see damage to the tillers and, in some cases, some significant drying.  We need complete canopy development to both minimize late season weed pressure and achieve good yields.

2. Case #2 - The farmer applies very light, frequent irrigation applications of .09" per pass.  As shown in the graph below, the trend for soil moisture at the 4" depth has increased.  Note the small "dips" after each application, but not complete refill of the soil profile.  Fortunately, on June 17, the rice field received significant rain that recharged the soil profile.

3. Case #3 - The grower applies too much irrigation per pass.  There are two problems with this approach:
  • There is a potential for runoff (which is what happened).  More water was applied than the soil could infiltrate or store on the surface and it began to run off.
  • There is significant time to get back to the start of the irrigation cycle.  Rice is a shallow-rooted crop and does not have much soil volume from which to draw moisture; it may reach critical depletion before the center pivot gets back to the beginning of the cycle.

Overall, though, the rice is looking excellent and has good weed control.