MSU Extension: Pulse grains in wheat rotations can increase profits for farmers

From the MSU News Service

An analysis by Montana State University researchers has shown that replacing summer fallow with a pulse grain crop, even in dry regions, can increase profits for farmers.

Farmers in regions with low precipitation, such as Montana’s Golden Triangle, know there is an economic risk to continuous small grains cropping, according to Perry Miller, professor of sustainable cropping systems in MSU’s Department of Land Resources and Environmental Sciences.

However, leaving fields fallow in summer is not ideal for soil health and generates no revenue, he said. So, alternatives to fallow are being tried and have demonstrated economic success.

In a 2015 study, Miller found that, in relatively wet southwest Montana conditions, pulses harvested for grain, in rotation with wheat, provided higher net returns compared to wheat in rotation with wheat, fallow or legume cover. Further research continued to test the results in dry regions.

Meanwhile, Miller and his colleagues conducted an eight-year study in Big Sandy, a dry region where the annual precipitation is close to 14 inches. The study focused on no-till winter wheat managed in rotation with fallow, spring wheat, pea cover crop and a pulse crop harvested for grain. The researchers managed the wheat with four different nitrogen rates: zero, 75%, 100% and 150% of the MSU guideline of nearly 3 pounds of nitrogen per bushel.

Pulse-wheat rotations had equal or greater net returns than fallow-wheat rotations during this eight-year study, Miller said. Cover-wheat and continuous wheat rotations had the lowest net returns.

Continuous wheat had no net loss if no nitrogen was added during years with a low price penalty for low protein wheat. It also had no net loss when less than 100% recommended nitrogen was supplied during years with a high price penalty.

In all rotations, net returns were greatest at 100% of recommended nitrogen under a low protein discount. Under a high protein discount, net returns were greatest at 150% of recommended nitrogen.

However, Clain Jones, MSU Extension soil fertility specialist, cautioned against using more than 3 pounds of nitrogen per bushel, especially on winter wheat.

“The small profit gains between 100% and 150% nitrogen might not offset the negative effects of soil acidification caused by higher nitrogen fertilization,” he said.

Jones and others have found that soil acidification due to applying more ammonium-based fertilizer than plants need can lead to yield losses.

“The yield of legumes, such as pea, decline below soil pH 5.7,” Jones said. In the Big Sandy study, soil pH was 5.8 in the continuous wheat and fallow-wheat plots. Soil pH in the pulse-wheat rotation was around 6.1.

According to Jones, soil acidification is a growing issue occurring in wet and dry regions of Montana. Due to yield loss and the high costs of mitigating low pH with lime, the short-term benefits of greater nitrogen rates might be partly or fully negated.

“Alternating pulse crops with wheat not only provides an income in what would be the fallow year but also reduces the amount of nitrogen fertilizer required for the wheat rotation,” Miller said. Nitrogen fertilizer rates were reduced by 22 pounds per acre after the first pulse rotations in the site’s sandy loam soils.

More information about including pulse crops in wheat rotations can be found in Montana State University Fertilizer Facts No. 76 and 82 at https://landresources.montana.edu/fertilizerfacts/index.html.