Crop/fallow: Finding a balance

from MSU News Services

Contact: Perry Miller (406) 994-5431, Rich Barber (406) 567-2211

As dry as some parts of Montana are, a cropping system that includes fallow is important. On the other hand, the drought seems to have prompted a rush back to inflexible crop-fallow sequencing. That may be using fallow too much for peak profits, says a cropping systems researcher.

"My goal is to develop sustainable cropping sequences, and that can include two or more carefully chosen crops before fallowing," says Perry Miller, Montana State University cropping systems researcher.

The innovation of leaving land fallow one year in two started on the Northern Plains about 80 years ago as farmers and researchers experimented with new ways of low-moisture farming. The practice became an institution, one that some researchers and producers think is due for a change.

The idea was that if you kept plants from growing on the land for a year, all the moisture they would have used would be waiting for you the next season. The trouble is, the system doesn't always work that way. A lot of moisture evaporates from bare or chemically fallowed land and additional moisture drains out of shallow soils.

Miller has been experimenting to determine what cropping sequences would make use of the moisture that is otherwise lost in a crop/fallow sequence.

Just as the homesteaders and early researchers thought, Miller's studies show that recropping grain after grain is quite risky unless there's more moisture than normal on the Northern Plains. On the other hand, he's also finding that using traditionally fallowed land to produce early forage

between grain crops can be profitable, as shown at recent test sites near Denton, Havre and Amsterdam.

Miller, with co-investigator Rick Engel and others, studied dry pea, yellow mustard and spring wheat at those sites and managed them in four ways: removing the forage early, plowing the crop under while it was still green, and harvesting at traditional times with and without removing the remaining straw.

"Early forage production would have been profitable for most crops at most locations" in this study, Miller and his colleagues concluded. In this case, they defined profitability strictly as the value of the crop. They did not include the long-term additional value of improving soil organic

matter and moisture retention by turning green crops into the soil or the value of nitrogen added to the soil by "pulse" crops such as pea. Because pulse crops add nitrogen to the soil, farmers save on nitrogen fertilizer for the crop after a pulse crop. Early-terminated pea, for example, added roughly 40 pounds of nitrogen per acre to the soil compared to continuous

wheat.

There may be more good news: the nitrogen benefits occurred whether the researchers removed the dry pea early for forage or chem-fallowed and left it on the surface for its organic benefits.

"This was surprising, but it may be because the crop's contribution of nitrogen was not coming from the part of the plant that was above ground. In this case, forage was harvested early without compromising the nitrogen benefit. But we need to research this further, because it goes against

conventional wisdom and we only have three site-years of data," says Miller.

Such early harvest is the best way to make sure a recrop uses only the moisture that might otherwise be wasted. Recropping with pea was more water efficient in these studies than recropping with either mustard or wheat. The pea, whether terminated early or taken to grain, used 0.7 to 0.9 inches less water than mustard or wheat, and conserved about as much moisture as a fallow field.

"By the following spring, soil water under early-terminated pea approached that available under chemfallow," says Miller. This means that in some cases, especially with a shallow-rooted crop like pea, you can grow a crop long enough to increase soil nitrogen, and grow mainly with moisture that is typically replenished before the next crop.

Because shallow or sandy soils don't retain moisture well, if recropping works anywhere, it should work best on those soils, says Miller.

While there are a variety of soils near Denton, many are shallow. They become gravelly between two and four feet under the surface, says Richard Barber, who farms and runs Barber Seed Service there. Some of Miller's research plots are on Barber's farms.

Barber says he can prove that he maximizes net income by either recropping or permitting longer crop rotations before fallow. He has been experimenting with recropping for about 28 years and says he is now all but continuously cropping.

"What we think we prove with our worksheets is that winter wheat on summer fallow is the least profitable crop when you talk net dollars," says Barber. He figures summer fallow costs $25 per acre just to keep the weeds down, whether summer-fallowed or chem-fallowed. There's also the cost of leaving the land idle for the year. "People think winter wheat is their most profitable crop, but they forget to divide their gross in half for the idle year," he adds. "Even if you own the land outright, you should be making interest on that investment every year."

Barber says his area averages 14 inches of precipitation a year, about 8.4 inches during the growing season. However, in recent years the Denton area has gotten only 80 percent of that average. Even at that, he estimates that he has only lost one percent of his crops due to too little moisture in the past 10 years.

"We're able to crop and recrop and have acceptable yields financially," says Barber. "But we're not in the Triangle, where some folks didn't harvest anything on either summer fallow or recrop."

As he speaks to groups about the profits in recropping, Barber says he's hearing more and more that because times are so tough, producers can't afford to recrop. That, he says, is why he is convinced Montanans must farm differently.

"If we can prove to ourselves that we can farm a little differently and do better, then the whole Northern Tier can do better," says Barber.

That "differently" may include the short-cycle pea crop that Miller says adds systems benefits while being highly water efficient.The cropping sequence study was funded by the Montana Fertilizer Tax Advisory Committee. More details of Miller's study can be found on the Web at:

http://scarab.msu.montana.edu/CropSystems/DryCroppingSystems_files/frame.htm

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