Seeding is under way and cropping plans are finalized for summerfallow and stubble fields with sufficient soil moisture.
Attention is turning to stubble fields with low moisture reserves, especially in areas that missed the recent rains, said Ken Panchuk, soil specialist with Saskatchewan Agriculture.
“Before making any decisions, farmers need to probe their stubble field with a soil probe or auger, a moisture probe, or a moisture probe with an auger tip. A moisture probe with or without an auger tip is the easy and quick way to measure soil moisture. This probe can be easily made in a farm workshop,” he said.
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Several materials are needed to make a moisture probe: a five-eighths to three-quarter inch steel ballbearing; a half-inch rod three to four feet long; and, for the handle, a one-inch-diameter pipe or other material, 10 to 12 inches long.
Weld the steel ball to the end of the rod, and dip it in water to maintain hardness. Grind off rough burrs from the weld, and weld the rod to the handle.
“To make the deluxe model, weld a two-inch piece of half-inch wood auger on the end of the ball. This allows the extraction of some soil at any depth. Now you’re ready to go to the field,” said Panchuk.
The soil probe, auger or moisture probe with auger tip can be used to bring up soil. If this soil doesn’t fall apart when balled, there is plant-available moisture to that depth.
Probe several times for accuracy
If using a moisture probe only, push it into the ground and the steel ball will stop at the dry soil zone. This determines the number of feet of moist soil. When using a moisture probe, re-probe to ensure frozen ground or rocks are not stopping the ball.
“This moisture sampling procedure should be repeated throughout the field and on all landscapes before making a decision to seed or to delay seeding until more rain falls.”
But the question remains: how much moist soil is enough to grow a crop? Panchuk said the answer depends on how much risk a producer wants to take in terms of input costs and expected precipitation for the growing season.
Type of soil important
There are guidelines, based on soil texture, to help make the decision. For example, loamy sand holds about one inch of moisture per foot of soil depth; loamy fine sand to loam holds about one inch of moisture per 10 inches of soil; silt loam to clay loam holds about one inch of moisture per eight inches of soil; and silty clay loam to heavy clay holds about one inch of moisture per six inches of soil.
Knowing the depth of moist soil required to produce a satisfactory crop is also useful. In the brown, dark brown and thin black soils, sandy loam requires about 48 inches of moist soil, loam 36 inches, and clay 24 inches. In the thick black and grey-wooded soils, sandy loam requires at least 36 inches of moist soil, loam 30 inches, and clay 18 inches.
Panchuk said these guidelines allow about four inches of soil water to start the crop in brown and dark brown soils, and three inches of soil water in black and grey-wooded soils.
“So how much risk should farmers take? Only they can make that decision. But they should keep in mind that, with direct-seeding technology and soil conservation practices, evaporation from the soil surface is reduced. Therefore more moisture will be available for the crop,” he said.
Also, with the residue on the surface, rain enters the soil more easily and quickly, especially in downpours.
To conserve limited soil moisture, Panchuk suggests: seed early, use an early maturing variety, minimize soil disturbance, pack to improve seed-to-soil moisture contact; and use a balance of fertilizer aimed at a realistic target yield.
If nitrogen is deficient, adding nitrogen fertilizer improves moisture-use efficiency, he said.
