The extremely dry conditions in much of Montana may affect how produces manage nutrients for crop productions next year, a Montana State University soil expert warns.
There are a few recommended differences between nutrient management during drought conditions and normal conditions.
"The nutrients available for next season's crops may be either higher or lower than normal because the amount removed by the drought-stressed crop may be different than in a normal year and soil-nutrient cycles are altered," says Clain Jones, Extension soil fertility specialist in the Department of Land Resources and Environmental Sciences at MSU.
There is an assumption that fewer nutrients are removed by the lower yielding drought stressed crops. Some crops may have been harvested as forage rather than grain, notes Jones Harvest of the whole plant may remove more nutrients from the field than a grain harvest. Alternatively, if a crop is considered a total loss and not harvested at all, no nutrients are removed from the field.
The amounts of nutrients removed are more a function of size of the harvest than of possible changes in grain or straw nutrient concentrations caused by drought.
Decreased downward nitrogen movement out of the rooting zone also contributes to potentially higher than normal fall nitrate-nitrogen levels. If there is substantial fall to mid-spring rainfall, this residual nitrogen is susceptible to over-winter leaching loss, especially in coarse soils with cracks, says Jones.
"No-till slows decomposition of the plant residue, making less residual nitrogen available for leaching, and helps retain the nitrogen on the site" Jones adds. "A volunteer grain crop or winter weeds can help capture and hold some of the residual nitrogen."
Phosphorus and potassium levels are largely influenced by residual plant uptake, the harvest timing and amount, and which part of the plant is removed.