LA Soybean Crop Progress & Condition Week Of June 15th

By David Mosely, Ph.D.

LSU Ag Center Soybean Specialist

The 2020 soybean planting season in Louisiana nears completion as the planting progress reached 98% by the week ending on June 14.. A total of 46% of the soybean crop is blooming and 7% is setting pods. The parish agents report the crop continues to look good. Statewide, the USDA data agrees with this report with a rating of 98% fair to excellent. However, 66% of the crop was rated as good to excellent, 8% less than last week. On the soybean remind text system, it was reported that the LSU Agcenter has been getting calls on fungicide options in soybean. Included in the text were fungicide efficacy ratings for the control of foliar fungicide diseases. The efficacy ratings can found at 2020 Soybean Foliar Fungicide Efficacy Table_LA.pdf.

The 2020 soybean planting season is 98% complete as of June 14, 2020.

The soybean crop was rated 98% fair to excellent on June 14, 2020. However, 66% of the crop was rated as good-excellent, 8% less than the previous week.

Irrigation Scheduling

I have heard reports of some producers recently irrigating soybean fields; however, timely rains last week have postponed the first irrigation application for other producers. I visited with Dr. Stacia Conger, Assistant Professor from the LSU Agcenter, to determine the most efficient time to initiate and terminate irrigation in soybean. The following paragraph and pictures are from Dr. Conger. In her recommendation, she describes initiating irrigation in determinate soybean fields which can be sensitive to drought stress beginning early in the flowering stages. Indeterminate soybean are more sensitive to drought stress in the mid to late reproductive stages (late flowering to pod fill). Dr. Conger mentions the need to use one of the scientific methods to determine available soil moisture and describes the look-and-feel method. In addition to the look-and-feel method, soil moisture sensors are available and can be a valuable tool in accurately measuring the available soil moisture. Please reach out to Dr. Conger for additional information.

Determining when to irrigate (i.e. irrigation timing) is important to maintain both yield quantity and quality.  Irrigation initiation is suggested for V10 growth stage but can wait until V12-R1 if there is good soil moisture. Alleviation of water stress during the reproductive period is critical and should utilize one of the available scientific methods.  The most straightforward method is the look-and-feel method. This process begins by taking a small soil sample from the representative portion of the root zone, at least 4 inches below the soil surface.  After forming a small ball by squeezing firmly, a field is immediately ready for irrigation when a slightly moist, weak ball forms with rough surfaces, no water staining on fingers, and just a few soil grains fall away from the ball. When managing multiple fields under one water source, this point may be too late for the fields at the end of the rotation. In this case, the ball should cause light staining on fingers and act pliable when handled.  Irrigation termination should occur around R6.5 or until there is enough soil moisture to finish pod filling.