Has research data changed recommendations for providing calcium?
By Glen Harris and John Beasley,
University of Georgia, and Julie Howe,
Historically, the recommendation for providing calcium to the peanut pegging zone was to apply 1,000 pounds per acre of gypsum or the equivalent (broadcast or banded) at bloomtime. This was to be applied only if you did not have at least 500 pounds of calcium per acre and a calcium-to-potassium (Ca:K) ratio of at least three-to-one (3:1)in a soil sample taken from the pegging zone soon after the peanuts emerge.
Since calcium is critical to germination, it has always been recommended that any peanut being produced for seed should receive 1,000 pounds per acre of gypsum at early bloom regardless of pegging zone Ca and K levels.
Then about 15 years ago, research was done at UGA using lime at planting to provide calcium to the pegging zone of peanut. Important points about this recommendation include: 1) This method is only supposed to be used when lime is recommended according to soil sample results. If lime is used when it is not called for, it can raise the pH above recommended levels and cause micronutrient deficiencies such as with manganese. 2) If you use lime, it must be applied at planting and it should not be deep turned. The calcium in lime is not as soluble as the calcium in gypsum. Therefore, if lime is applied at bloomtime, it will not have enough time to “break down” and be absorbed into the developing peanuts.
A New Method
Finally, over the last three years, a new technique of using liquid calcium chloride or calcium thiosulfate through the pivot during peak pod fill has been tested at UGA and has shown promise for providing calcium to the pegging zone. If gypsum becomes in short supply, this method may be a valuable alternative for calcium application. Calcium chloride has also been tested in dryland situations by applying it in a band behind the presswheel at planting. This may also be a technique to consider.
Calcium Q and A
The following are a number of common questions concerning providing calcium to the pegging zone with up-to-date answers.
Q: Is there any difference between gypsum materials available?
A: No, not as far as the ability to supply calcium to the pegging zone. Last year, USG 500, PCS Wetbulk, AgriCal (smokestack) and even a new product called “Gypsoil” were tested and seem to perform equally. Selection can be made based on factors such as product availability and how well the material handles and is applied.
Q: Is it better to use lime or gypsum for dryland peanuts?
A: Gypsum! During the last two years, gypsum at bloomtime has outperformed lime at planting as far as providing calcium to the pegging zone. This makes sense when you think about it, since the calcium in lime is less soluble than the calcium in gypsum under limited water situations in dryland production, the calcium in lime may not become as available compared to when it is under irrigation.
Q: Have the calcium recommendations changed since the shift from small-seeded to large-seeded runners?
A: Technically, no. Research data from 2008 to 2010 showed that both the 500 pounds per acre calcium in the pegging zone requirement and the 1,000 pounds per acre gypsum application rate overall, appear to hold for large-seeded runners. However, it is clear that following this recommendation is more important for large-seeded runners, and especially for GA 06G. Also, when the pegging zone calcium is between 500 and 750 pounds per acre, you are in a “grey area” and again this is where calcium chloride or calcium thisosulfate applied through center pivots may be most beneficial.
Q: Are foliar calcium applications recommended on peanuts?
A: No. This one is abundantly clear. Foliar calcium products recommended in the one quart per acre range that are sprayed on the leaves in total spray volumes of 10 to 20 gallons per acre do not provide enough calcium. Even if it did, it does not get translocated from the leaves to the developing pods.
Q: Isn’t putting calcium chloride or calcium thisoulfate liquids through a center pivot a foliar application? I mean the water hits the leaves, right?
A: No. Putting these “liquid calciums” through a center pivot is a soil-applied application. When putting out that much water per acre, even though it hits the leaves initially, it basically runs off and is applied to the soil. Think of it this way, when you foliar feed, you apply approximately 10 gallons per acre final spray volume. When you apply one acre-inch, you are applying approximately 27,000 gallons of water – a huge difference.
Q: So, do you recommend putting calcium chloride or calcium thiosulfate through center pivots? And does it replace using gypsum?
A: Yes and No. Based on research data from the last three years, calcium chloride and calcium thiosulfate applied through a center pivot (to supply approximately 25 pounds per acre of highly soluble calcium during bloom) improved yield, calcium in the seed and germination compared to the untreated check. However, these products do not increase the soil test calcium levels after harvest near as high as gypsum. So, in that regard, it does not replace gypsum. Again, these two products applied with center pivot irrigation appear to have the best fit when the pegging zone calcium levels are in that “grey area” of 500 to 750 pounds calcium per acre. If the pegging zone calcium level is below 500 pounds per acre, then gypsum should be applied instead.
Q: Can I apply gypsum at planting?
A: This is not recommended at this point because there is always a chance that with enough rain or irrigation water early on, the calcium in gypsum could leach below the pegging zone. This is especially true on deep sandy soils.
Q: Should I split my gypsum applications and put some on at planting and some at early bloom?
A: This is also not recommended at this time. However, research studies are being conducted to see if there may be a benefit to this timing of application.
Q: How late in the season is too late to put out gypsum?
A: Gypsum should be applied at “early bloom” or approximately 30 to 45 days after planting depending on growing conditions. Once you get past 100 days after planting, the majority of pods have probably already absorbed the proper amount of calcium or not. After 100 days, tractor damage by running over lapped vines is not desirable. PG