According to the USDA, the Louisiana soybean producers planted 100% of the 2020 crop by the week ending on June 21, which is ahead of 2019 and the five-year average (Figure 1). A total of 55% of the crop is blooming and 15% is setting pods. The rating of fair-excellent dropped to 96%, 2% lower than the previous week. However, 73% of the crop was rated good-excellent which is the third highest rating of the current season. The two previous weeks with higher ratings of good-excellent were May 10 (75%) and June 7 (74%). According to the USDA report, precipitation was sparse during the week, and the top-soil moisture rating of short was 39%, at least 13% higher than any previous week in 2020. Hopefully with over half of the crop in reproductive stages, this current rain pattern will bring efficient moisture to soybean fields.
Figure 1. The Louisiana soybean producers have
planted 100% of the 2020 crop.
Figure 2. The rating of fair-excellent dropped to
96%, 2% lower than the previous week. However, 73% of the crop was rated
good-excellent which is the third highest rating of the crop season.
A deficiency in potassium can limit yield potential by more than 50% in soybean plants if not corrected. A total of 2.9 pounds of K2O is estimated to be required for every bushel of soybean harvested. For a 55-bushel crop, approximately 160 pounds of K2O per acre would be required. If soybean plants are deficient in potassium, the symptoms will begin as irregular yellowing on edges of leaves (Figures 3 and 4). The leaves may eventually turn brown and die. Unfortunately, not all potassium deficient soybean plants will show symptoms, except for possible yield loss. Fortunately, in-season tissue sampling can diagnose a hidden deficiency, and research has suggested a timely potassium application can reduce yield loss. Ongoing research, led by LSU AgCenter Assistant Professor Dr. Rasel Parvej, will help refine potassium application recommendations. More information on potassium deficiency and corrective measures has been published in the Volume 10, Issue 5 – June 2020 edition of the Louisiana Crops Newsletter and can be found at https://www.lsuagcenter.com/profiles/lblack/articles/page1592601650709.
Figure 3. Symptoms of potassium deficiency begin as irregular yellowing on the edges of leaves. The symptoms will be located mainly on older leaves in the lower canopy during early vegetative stages. Photo by Dr. Rasel Parvej.
Figure 4. During the reproductive stages, potassium deficiency symptoms often appear on younger leaves in the upper canopy. Photo by Dr. Rasel Parvej.
Figure 5. John Upton, LSU AgCenter Research Associate
for the soybean agronomy program, applying potassium for a fertilizer trial at
the Dean Lee Research Center.
The LSU AgCenter and the LSU College of Agriculture