MSU Extension offers pulse crop fertilization information

MSU News - Agriculture (College)




April 20, 2017 -- MSU News Service



BOZEMAN – Montana State University Extension Soil Fertility Specialist Clain Jones is sharing information on the unique soil fertility needs of pulse crops in contrast to the needs of small grains.
More in-depth information on the topic is available from MSU’s Soil Fertility Extension website in the Montana Cool-Season Pulse Production Guide and the Pulse Crop Inoculation and Fertilization presentation.
Montana is seeing a steady increase in the acres planted to peas, lentils and chickpeas, also collectively called pulse crops, according to Jones, who works in the Department of Land Resources and Environmental Sciences in the MSU College of Agriculture. These crops have unique soil fertility needs, different from small grains, he added.
"The most obvious difference is that (pulse crops) are legumes, which can produce their own nitrogen, rather than relying heavily on nitrogen fertilizer," said Jones. “But, that doesn't mean soil nitrogen can be ignored.”
Jones said that legumes rely on nitrogen fixation by rhizobia, a type of soil bacteria, which start to produce nodules on the roots around two weeks after plant emergence.
“It takes around four weeks after germination for nodules to be active, which is about the third node stage,” he said. “The nitrogen up to that point needs to come from the top 12 inches of soil.”
There are several factors that can limit nodulation and nitrogen-fixation, Jones said. These include saline soils, soil pH less than 5.5 or greater than 8, high levels of soil nitrate and waterlogged or dry soils.
"Nitrogen fixation can stop if the legume becomes drought-stressed," Jones said. In Montana's dryland production, this means that nitrogen fixation can be slowed by flowering, forcing the plant to rely on soil and plant stores of nitrogen for seed production, he explained.
"The trick is to have about 15 to 30 pounds total nitrogen per acre at seeding to get the plants ...

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