Nutrient Deficiencies Late in the Season Peanut Notes No. 105 2018
Excessive rain can affect pH and availability of nutrients for peanut and other crops. Limited data exists on how to correct these problems. Within the past few weeks we have received questions about copper, calcium and potassium as well as questions about nitrogen-deficient peanuts and those that might be yellowing in general. I have recommended ½ the normal rate of gypsum within the past week and in 2017 growers applied additional potash after major rains. For all of these situations a response most likely will be minimal, although many peanuts were planted in late May and into June in 2018, and those peanuts have potential to benefit from a corrective action. We do not have a general understanding of how much rain it takes to move elements through the soil profile with respect to a crop response, especially when trying to tie response to growth stage. Certainly soil characteristics influence this as much as the amount and intensity of rain. Is one 3-5 inch rain enough to cause a problem? Most likely not, as much of that will run off of the field. What about two weeks where we get a cumulative amount of 10 inches or more? How about one 8-10 inch deluge? The last two scenarios are where corrective action might be beneficial but most likely only when it happens much earlier in the season than now.
My suggestion is that going into the week of August 13 there is little value in adding additional fertilizer to peanut. Most peanuts are about 4-6 weeks from digging and it will be a challenge to change fertility and plant nutrition in a positive way at this point in time.