Most things seem to be in a hurry-up mode these days, but many things in crop production just cannot be pushed ahead: point in fact, peanuts.
Proper soil temperature is essential for success of spring planting, and for fragile crops such as peanuts, cool soil can be disastrous and can force replanting.
“Peanut planting should not begin until the soil temperature is 65 degrees at a 4-inch depth, measured at 7 a.m. for three consecutive days,” said Chad Godsey, Oklahoma State University assistant professor of plant and soil sciences.
In Oklahoma, that may not happen until approximately May 1. In addition, spring weather conditions can change dramatically.
“A cold front can change soil temperatures to drop below acceptable levels for peanuts,” Godsey said. “The situation can become especially critical when cold air is accompanied by cold rain.”
Godsey recommends peanut growers take extra care to follow weather reports in the spring, and to delay planting peanuts before a predicted cold front.
“Knowledge of soil texture of different fields also can be valuable in deciding which peanut field should be planted first,” he said.
Sandy soils tend to warm more quickly than finer-textured soils that contain higher amounts of clay or loam. The difference is related to water-holding capacity.
Because of its course texture, sand holds less moisture, and finer-textured clay or loam has higher water-holding capacity. Moisture is slow to react to temperature change, so finer-textured soils with high moisture content will remain cooler longer.
“Water uptake is the first step in germination of peanut seed,” Godsey said. “Seeds must acquire a moisture level higher than 35 percent for germination. However, seeds that take up cold water during germination may perform poorly.”
The most reliable planting periods for peanuts in Oklahoma are May 1-15 for runner varieties and May 1-30 for Spanish varieties.
Optimum soil temperature for rapid germination and seedling development is 86 degrees to 91 degrees Fahrenheit. Peanut seed will germinate quickly within a range of 77 degrees to 86 degrees, and seed actually can germinate over the wide range of 41 degrees to 104 degrees.
“Tight profit margins for most producers justify extra care at planting time to avoid replanting,” Godsey said.
Desirable stands for runner varieties have about four plants per row foot. For Spanish varieties, it is desirable to have five or six plants per row foot. An emerging stand should have minimal skips longer than six inches.
Rotary hoeing may be needed to assist peanut seedlings struggling to emerge through a soil crust.
“Exposure to high temperature and humidity can cause substantial damage to seed quality and, therefore, germination,” Godsey said. “Peanut seed should not be left sitting in direct sunlight for long periods of time. Only seed that can be planted in about half a day should be hauled to the field.”
Peanut seed coats are very fragile. Seed sacks should never be thrown or purposely dropped. Godsey advises that stirring seed in the hopper boxes also be kept to a minimum, since the stirring action may damage sensitive seed coats.