Should wheat follow flax or flax follow wheat? Should you grow winter wheat after peas to conserve soil moisture? These are some of the questions that USDA’s Crop Sequence Calculator could help to answer.
Following a proper sequence and even using cover crops in some cereal and pulse crop rotations may help to increase overall productivity, says Don Tanaka, a soil and water conservation researcher at the USDA Northern Great Plains Research Laboratory at Mandan, North Dakota. Tanaka and colleagues have developed the calculator, which is available on CD.
“One of our goals was to look at what crop sequence producers can use to get the most benefit from the previous crop,” says Tanaka. “It does make a difference whether corn follows wheat, or canola follows peas in rotation. Producers need to know whether the crop sequence they are using affects disease, soil quality and water use, for example.”
Crop sequencing can have a positive or negative affect on the following crop, depending on its level of sensitivity.
“It is not just a matter of breaking the disease cycle,” says Tanaka. “We know that a crop grown on its own residue is the worse scenario. And we also know that each crop has its own group of microorganisms that work in the soil. There are synergies between some crops. The microorganisms of one can also benefit another crop. But we also found there can be an antagonistic effect between some crops.”
Tanaka and colleagues looked at 16 cool and warm season crops including barley, buckwheat, canola, chickpea, corn, crambe, dry bean, field peas, flax, grain sorghum, lentil, proso millet, safflower, soybean, spring wheat and sunflower.
In looking at crop sensitivity in various sequences, spring wheat, Proso millet and field peas where the least sensitive to any previous crop, while grain sorghum, corn and sunflower were the most sensitive. With the crop sequence calculator, you can plug in your planned rotations to determine if there will be positive or negative effects.
To get a copy of the Crop Sequence Calculator, go to the research centre website at www.mandan.ars.usda.gov,Google “Crop Sequence Calculator” or phone 701-667-3000. Tanaka notes the CD wasn’t designed to specifically work with the Vista software that comes with newer PCs, but it will work.
On the moisture conservation front, their research showed that corn and sunflower, for example, used the most soil water, while peas used the least. Soil water recharged fastest on grain sorghum and spring wheat stubble, and slowest on chickpea, lentil, field pea and sunflower stubble. One of the main factors here was how much residue was left standing to trap snow.
The Crop Sequence Calculator CD, developed at USDA in North Dakota, could help you sequence your crop rotation in to maximize yield, pest control and water-use efficiency.
COVER CROPS TO CONSERVE MOISTURE
Over the next few years, Tanaka hopes to develop another calculator or guide that can help producers decide if they can conserve soil moisture with a cover crop on mid-season stubble.
On this project he is looking at the use of mid-season cover crops to protect soil moisture reserves after some of the earlier crops have been harvested.
“Winter wheat and peas are two crops in particular that are harvested early, leaving a relatively large window for soil moisture to be lost after harvest,” says Tanaka. “In our area of North Dakota, with limited stubble from these crops and often hot temperatures and winds, a significant amount of soil moisture can be lost between early to mid-August and mid-October.” He also says there is potential for soil moisture loss after some annual cereal crops, such as barley, are harvested for hay or silage in early to mid summer.
Tanaka is testing several different crops, both as single crops and in seed mixtures, which can be used as ground cover. Cover crops include purple top turnip, proso millet, triticale, soybean, peas, winter canola, forage radish and sunflowers. A couple in particular, purple top turnip and forage radish, have long tap roots that can benefit water infiltration into the soil.
“We are looking at the potential of these crops to be seeded mid-to-late summer. They can grow and provide ground cover and maybe used as a forage crop or as fall pasture if people have cattle, or just be left and be direct seeded in to the following spring,” he says. “While these cover crops also need moisture to grow, we are hoping through transpiration, they also return moisture to the soil.”
Soil moisture losses aren’t as significant following hard red spring wheat and barley because these crops are usually harvested in September or later, when weather conditions are cooler.
As cover crops are evaluated over the next three to five years, Tanaka also hopes to produce some type of guide that farmers can use to conserve soil moisture.
Lee Hart is a field editor for Grainews in Calgary. Contact him at 403-592-1964 or by email at [email protected]