Come rain or drought, calcium and boron fertilization are critical to producing high-yielding, high-quality peanuts, says Glen Harris, University of Georgia Extension agronomist.
“We all know it takes water to get the calcium into the peanut pods,” says Harris. “If we don't get enough rain, or if we can't irrigate, we worry about getting calcium into the soil solution. During years of normal rainfall, we run the risk of leaching calcium right past the pegging zone.”
The best method for applying boron, he says, still is to mix it with early fungicide applications. And, in wet or normal rainfall years, fungicide applications are plentiful, he adds.
“So, the importance of calcium and boron are the same, regardless of whether or not we receive rainfall. Calcium arguably is the most important fertilizer nutrient needed for growing high-yield, high-quality peanuts.
“Nothing is more frustrating than turning up a crop and finding a bunch of ‘pops’, pod rot, black heart or aflatoxin due to poor calcium nutrition. This is even more frustrating when you think you've done everything right to avoid these problems,” says Harris.
Two common methods of providing calcium to the plant are with lime after deep turning but before planting or with calcium sulfate — gypsum or landplaster — at bloom time, he says. Both of these methods require water in the form of rainfall and/or irrigation to dissolve the calcium into the soil solution from where it enters directly into the developing peanut pod, he adds.
“This past year, we also looked at a liquid calcium that can be applied through irrigation pivots. Traditionally, liquid calcium materials are not thought to supply enough calcium compared to the lime method or gypsum applications. And, in years when it rains, it may prove to be a challenge to time the application through the pivot around rainfall events.
“Our trials this past year with liquid calcium didn't look too bad. This is a common method for applying calcium in Texas because those growers are so far from a gypsum source. We'll be looking at this again this year in Georgia.”
Boron uptake from the soil, says Harris, is affected by both moisture conditions and pH. The droughts of recent years, he says, have provided challenges in both of these areas.
“Lime may not have had enough water to dissolve properly and raise pH. Better soil moisture situations will help with the uptake of boron. Fortunately, we do not rely heavily on soil applications of boron. Instead, most of our boron is foliar fed. This is a cheap, easy and effective practice, and most of our growers realize this.”
As an essential micronutrient, most plants need small amounts of boron — but in a big way, says Harris.
“Boron plays a critical role in pollinating and fruiting. The lack of adequate boron fertilization can result in ‘hollow heart’, another frustrating result, especially since it is difficult to detect until after the peanuts are graded and the hidden damage is revealed.”
Many growers have been tempted during recent drought years, says Harris, to cut inputs to adjust for a lower yield potential.
“Calcium and boron, however, are not good inputs to look at cutting, even in drought years, let alone in years when we get decent rainfall. These nutrients — considered the most important fertilizer for peanuts — should be applied adequately every year, regardless of weather forecasts.”