No-till fields may need extra N
THe higher carbon-to-nitrogen ratios found in no-till fields are less than optimal for soil organisms in grain plantings, potentially causing immobilization of important underground microbes. But some added nitrogen just might help, according to new Montana State University research.
When managing a no-till crop for the soil and moisture benefits it delivers, the wheat stubble you leave behind may need an extra N jolt next spring beyond what conventional fields may require, MSU researcher Chengci Chen notes.
Tillage that breaks up plant residue and boosts the level of residue decomposition — not something a no-tiller would do — would increase N in the field. But the new study at MSU Central Agricultural Research Station in Moccasin shows soil nitrates were up higher in sweep-till treatments from late summer to midspring than in no-till fields.
• No-till fields were studied for nitrogen capacities.
• Some grain may need an added shot of nitrogen.
• Producers may contact Montana State University for more information.
Hungry soil microbes
As the tillage goes down, the buildup of plant residue naturally increases, helping improve soil conditions and yield. But the soil microbes that break down residue require N to do their work, and that’s where the problem of low nitrogen may occur.
It takes about a 1,000 pounds of N per acre to gain 1% soil organic matter in the top half-foot of the ground, according to Clain Jones, MSU Extension soil fertility specialist with the Department of Land Resources and Environmental Sciences.
A study by Brian McConkey, a researcher at Agriculture and Agri-Food Canada, discovered in the semi-arid Saskatchewan region that even when a grower adds 5 more pounds of N to no-till land for eight to 11 years following conversion from conventional farming practices, the property still had lower soil N than those not farmed as no-till.
The scientists say more N should be applied to no-till for up to 15 years after conversion to get grain and protein levels even with those in non no-till. But be cautioned, says Jones: There is no one-size-fits-all recommendation for how much more N a no-till or minimal-till system really needs.
It varies with soil texture, climate, tillage, previous crops and length of time the field has been in no-till.
Some findings from Chen’s study include:
• Considerable amounts of nitrate N was released from late summer to early fall to spring in the wheat fields he studied.
• Spring wheat and winter wheat rotations released less nitrate N over the fall and winter than rotations of fallow ground and winter wheat, spring wheat and winter wheat, or winter pea and winter wheat.
• The winter pea and winter wheat rotation had a similar wheat yield as the fallow and winter wheat rotation.
• No-till appears to require more N input than sweep till but can be offset by including pea in the rotation.
• Ideally, N fertilizer is placed at least 2 inches below the soil surface, but Jones says spring applications on no-till are generally broadcast. If possible, he advises incorporating fertilizer with at least a half-inch of water, or time the application before a substantial rainfall event.
The MSU Extension publication “Nutrient Management in No-till and Minimum-till Systems” provides more information about nutrient adjustments to consider when opting for no-till.
You can find the publication at, or call 406-994-3273.
This article published in the September, 2014 edition of WESTERN FARMER-STOCKMAN.
All rights reserved. Copyright Farm Progress Cos. 2014.