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Flexcropping: A Potential Risk Management Strategy
Spring crops in low and intermediate precipitation areas can be risky. Drier years like 1977 and 1985 would have been good years for summer fallow rather than spring recropping in some areas. Hindsight is always better than foresight. But, how can producers improve their decision-making on whether to spring recrop or fallow?
Principles of Flexcropping
A cropping strategy called ''flexcropping" may offer producers a useful guide for making the decision to spring recrop or to fallow. Flexcropping was developed in the crop-fallow region of the Northern Great Plains, specifically Montana and North Dakota. The strategy is based on a relatively simple concept that the success of spring recropping depends on the amount of water that will be available to the crop. This includes both the amount of plant-available water stored in the soil at planting time in the spring plus the probability of additional growing season precipitation.
For example, in the Northern Great Plains about 8 to 10 inches of available water is considered necessary to produce a "successful" spring cereal crop. If there are 3 inches of plant-available soil water at planting time and an 80 percent probability of receiving 6 inches of precipitation during the growing season, then the chances of having adequate water (9 inches) for a successful spring crop are good. However, if the plant-available soil water at planting is only 1 inch, then the potential available water for the spring crop is only 7 inches. Fallowing might be a better option in this case. As a general rule of thumb, the decision to spring recrop in the Northern Great Plains is based on 3 inches of plant-available soil water at planting time. This figure varies depending on the probabilities of growing season precipitation.
Adaption to PNW Conditions
The flexcropping decision rules of the Northern Great Plains cannot be directly applied to the Pacific Northwest. One of the main reasons is the difference in precipitation distribution. In the Northern Great Plains, about 60 percent of the annual precipitation occurs during the spring from April through June. In contrast, 65 to 75 percent of the Northwest annual precipitation occurs during the winter from November through March and only 15 to 20 percent occurs from April through June.
Considerable research must be done to develop a flexcropping guide for the Northwest. Several STEEP researchers are involved in adapting this cropping strategy for Northwest conditions. One researcher is Bob Ramig, USDA-ARS soil scientist at the Columbia Plateau Conservation Research Center near Pendleton, OR.
Based on preliminary research in northeastern Oregon, Rarnig suggests a general guide of 6 inches of plant-available soil water at planting time (March 1) for considering spring recropping in the 12-to 15-inch precipitation areas. However, additional research is needed in determining the optimum spring soil water level and the probability of growing season precipitation for the recropping decision across the region. In the traditional crop-fallow areas with less than 12 inches of annual precipitation, spring recropping is generally more risky. Above 15 inches annual precipitation, annual cropping should be possible with occasional summer fallow when plant-available soil water is low at planting time in the spring.
Ramig points out that there are several important soil related factors affecting plant-available soil water for the flexcropping decision. These include soil depth, texture and restrictive soil layers, all of which may limit soil water storage potential, For example, the Condon series, a shallow soil (less than 30 inches deep to bedrock) in north-central Oregon, can store 4.5 inches of plant-available soil water. Of the 11-inch average annual precipitation, 7 inches, or approximately 65 percent, occurs during the winter season. With at least a portion of the previous crop stubble remaining on the soil surface over winter, a storage efficiency of 70 percent or more can be achieved. Consequently, about 5 inches (70 percent of 7 inches) could be available for storage and the soil can only store 4.5 inches of plant-available soil water. Precipitation in excess of 4.5 inches will be lost to leaching or runoff and evaporation. From a soil water storage standpoint, there would be no point in summer fallowing, Where winter precipitation is sufficient, recropping of shallow soils should be considered in most years, fallowing only occasionally for control of weed, insect or disease problems.
Soil texture greatly influences the amount of plant-available water that a soil can store. A silt loam soil can store 2 or more inches of plant-available soil water per foot of soil. Coarser textured soils, such as sandy loam soils, can store about 1.5 inches per foot and loamy sand soils about 0.8 inch per foot. Once producers know the plant-available water holding capacity of their soils, they can estimate the total plant-available soil water by determining the depth of moist soil. This can be simply estimated with a metal probe or soil auger early in the spring after the soils have thawed.
Soil layers which restrict root growth or water movement also limit the amount of plant-available soil water. Tillage or traffic compacted layers, lime/silica cemented layers (caliche or hardpan) or bedrock can be present in many soils of the Northwest. These materials greatly influence rooting depth and water storage potentials.
Research by Ramig and others reveals the low water storage-use efficiency of the conventional tillage crop fallow system. To illustrate this, Ramig divides the soil water storage time of the 2-year crop-fallow rotation into three main periods. "Winter 1'' is from August 1 after harvest to March 1 7 months. "Summer 1," or the summer fallow season, is from March 1 to winter wheat seeding about October 1 also 7 months. "Winter 2" is from October 1 to March 1 5 months. The majority of soil water storage occurs during these first 19 months.
The most effective soil water storage period is "Winter 1'' where about 70 percent or more of the precipitation during that period can be stored in the soil. Standing stubble or fall chiseling are both effective practices for enhancing storage of winter precipitation. There is typically no increase in stored soil water during" Summer 1," in fact some of the water stored before this period is frequently lost through evaporation, resulting in a net decrease.
Under a conventional tillage system, usually less than 50 percent of the "Winter 2" precipitation is stored. The low surface residue levels and fine, smooth surface after winter wheat is seeded result in more water loss through runoff and evaporation than during "Winter 1." Storage efficiency during the 19-month storage period is often only less than 40 percent. Where winter wheat is seeded under conservation tillage systems, "Winter 2" storage efficiency can be increased to 70 percent or more.
Ramig is continuing his research on soil water guidelines, as well as on crop management practices which improve water storage efficiency and production potential in flexcropping systems. Keith Saxton, USDA-ARS hydrologist at Pullman, WA, and other STEEP researchers are also working to determine crop water requirements, soil water levels for spring recropping, and probabilities of growing season precipitation amounts for various areas of the Northwest.
Plant-available soil water at planting time and growing season precipitation are two important factors in the decision whether to spring recrop or fallow. However, there are many other considerations. These include crop options and yield potentials, production costs, crop price, weed control, soil fertility, disease control and the farm program.
Doug Young, Washington State University agricultural economist, is involved in the economic evaluation of the flexcropping strategy. Young points out there are several reasons why a fixed crop-fallow rotation is still commonly used in the Northwest despite its low water use-efficiency and high rates of soil erosion under conventional tillage.
One factor, the structure of the historical federal farm programs, has provided a strong incentive for continued use of summer fallow. Program provisions have favored continuing the crop-fallow rotation in at least three ways: (1) fallow has generally qualified as program set aside acres; (2) higher yields on fallow increased the "proven yield" which leads to higher deficiency payments under the target price programs; and (3) since the producers base acreage for farm program participation has generally been determined on historical crop acreage, it has been difficult for growers to use spring recropping with wheat or barley as this would push crop acreage over base levels.
Some producers feel that the crop-fallow rotation helps smooth the workload over the year, reducing labor and machinery costs. The desire of many growers to receive a stable year-to-year income to pay bills and make loan payments favors crop-fallow rotations, even though income may be higher where fallow is less frequent in the rotation. Spring recropping can also be risky in the lower precipitation areas.
The desire to minimize risk in spring recropping is the underlying reason for flexcropping. In the economic evaluation of flexcropping, Young and other researchers used a computer crop simulation model with data for four locations. Two were in a 14- to 17-inch precipitation area of western Whitman County, WA, and two from 10.5to 11.5-inch precipitation areas in Sherman County, OR. They compared two crop rotation options: flexcropping continuous spring barley (fallow in dry years) and winter wheat-fallow. The research revealed that continuous spring -barley in a flexcropping system could increase expected profits relative to those for winter wheat-fallow in Whitman County but not for the drier Sherman County locations.
Young stresses that additional research information on plant-available soil water requirements at planting time and probabilities of growing season precipitation amounts are needed to improve the accuracy of the flexcropping strategy in the Northwest. Other crop options also need to be considered in the rotation. Refinement of the complex and time consuming computer model is in progress to facilitate use by producers.
us: Hans Kok, (208)885-5971
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