Nearly every crop grown in Montana requires nitrogen fertilizer at some level or another. Some crops, like wheat, need increased nitrogen fertilizer to maximize yield and protein, other crops like sugarbeets and malt barley need just the right amount – too much and the crop quality can be negatively impacted.
Nitrate is the primary plant-available form of nitrogen in the soil, explained Dr. Clain Jones, Montana State University Extension soil fertility specialist. An issue across the country, particularly in farming areas, is those nitrates have the potential to leach into groundwater sources.
“Nitrate is what a soil scientist would call mobile because it moves with water, it doesn’t really stick to the soil,” explained Jones.
Nitrate leaching is a world-wide problem, but Jones and fellow researchers, Dr. Stephanie Ewing, Adam Sigler and Dr. Perry Miller, focused in on areas of Montana where the groundwater is shallow and there is evidence of nitrate leaching. Nitrate levels in the drinking water of some central Montana towns have proven to exceed EPA’s drinking water standard, and since 2011, the MSU team has been trying to find ways to mitigate the leaching.
“A group here at MSU has studied nitrate leaching specifically in the Lewistown/Moccasin area because that area has very shallow soil and we found nitrate levels in groundwater at 2-3 times the EPA standard,” said Jones.
The research team looked at farm management practices that may help decrease nitrate leaching like slow release nitrogen fertilizers and split application of the nitrogen fertilizer. That way the nitrogen is applied in time with the plants’ growth cycles to maximize uptake.
The practice that rose to the forefront as being the most effective, however, was adding an extra crop into the farmer’s rotation instead of leaving the land fallow. Because legumes do not require any nitrogen fertilizer, Jones and the team from MSU worked with producers in the Judith Basin water drainage who split their fields into one-half fallow and one-half pulse – in this case peas – for the purpose of this study.
“Our research found a decrease in nitrate leaching and we also found a profit increase, so it kind of seems like a potential win-win for farmers,” Jones stated.
Most farmers opt to leave land in fallow because it stores water which can be beneficial for subsequent year crop yields and it requires fewer input costs than a crop like peas. Jones and his colleagues discovered, however, the revenue associated with planting peas instead were enough to offset production expenses and even make up for the potential yield decreases the following year.
Jones explained there is no magic rotation formula.
“We know from our research and from other people’s research that the more times in a rotation a crop is growing, the less chance there will be for nitrate leaching because those crops are pulling nitrogen out of the ground and they are pulling water out of the ground,” he explained.
Because it takes both excess nitrate and moving water for leaching to occur, dampening one or both variables greatly decreases the chance of nitrates leaching into drinking supplies.
From an equipment standpoint, only a few modifications may be needed in order to plant pulse crops. This is especially true if you are already set up as a cereal farmer.
“That was another nice thing, farmers didn’t have to make that many adjustments,” Jones said.
Montana remains on the leader board for pulse crop production and the research conducted by Jones and his MSU colleagues indicates that planting a pulse crop, instead of leaving land fallow offers both economic and environmental advantages.