Winter Lentil Could Provide Conservation Tillage Option

Chapter 8—Crops and Varieties, No. 12, Winter 1990

Roger Veseth

Winterhardy varieties of lentils are being developed for fall seeding in the Inland Pacific Northwest. Winter lentils would provide new production and conservation farming options for producers.

The varietal development program is being conducted by Steve Spaeth, crop physiologist, and Fred Muehlbauer, research geneticist, with the USDA-Agricultural Research Service at Washington State University in Pullman. If progress continues as planned, foundation seed of winter lentil varieties in small red, small yellow and large yellow lentil market classes could be available as early as 1993.

Potential Advantages and Possibilities

Winter lentils offer some potential advantages and new management options compared to spring lentils. These include:

1. Yields equal to or higher than spring lentils.
2. Better adaptation to conservation tillage systems. Reduced soil compaction potential with fall seeding compared to spring seeding.
3. Avoiding delays in spring seeding.
4. Expanded lentil production area, providing an alternate rotation crop to more producers.

Yield Potential

Fall-seeded crop varieties tend to have a higher yield potential than spring-seeded varieties under Northwest climatic conditions. A good example is the difference in yield potential between winter and spring varieties of soft white wheat. Spring wheat yields have commonly been about 20 to 40 percent lower than winter wheat. The longer growing period available to winter wheat, and its resulting deeper, more extensive root system, are important components of this yield advantage.

Spaeth and Muehlbauer have not as yet found a consistent yield advantage in winter lentils compared to spring lentils. The researchers compared 7 of their experimental selections against “Brewer” spring lentil at Pullman in 1989 (Table 1). Yields of 5 of the 7 selections were not significantly different from the yield of Brewer. Even with similar yields compared to spring lentils, the researchers stress that winter lentils also offer the previously mentioned potential advantages and management options as an alternate crop which are not possible with spring lentils.

Spaeth and Muehlbauer point out that the breeding effort on winter lentils is relatively new compared to that for spring lentils. Consequently, prospects for higher yielding winter lentil varieties should improve in the future as the breeding effort progresses.

Table 1. Yields of experimental selections of winter lentils compared to Brewer spring lentils in 1989 at the WSU Spillman Agronomy Farm near Pullman, WA (Spaeth and Muehlbauer, USDA-ARS).

The WH80-bulk selection in Table 1 is the initial bulk population of winterhardy lentils which includes both red and yellow lentils in a range of seed sizes. Much of the genetic material in this bulk population was originally collected in Turkey. All of the experimental line selections beginning with “WA” in Table 1 have been selected from this bulk population for possible development as future varieties. Three of the experimental lines have shown acceptable lentil quality. They represent all three lentil market classes of small red, small yellow and large yellow. An example of how the growth and rate of maturity of winter lentils compare with Brewer spring lentils is shown in Fig. 1.

Winter nursery trials of the winter lentil experimental lines were established in fall 1989 at three Inland Northwest locations with contrasting annual precipitation zones: Davenport, WA – 14 inches; Pullman, WA – 20 inches; and Craigmont, ID – 24 inches.

Facilitates Conservation Tillage

In much of the Inland Northwest lentil-production region, spring lentils are typically seeded into a conventionally-tilled seedbed with little residue from the previous crop remaining on the soil surface. Although the more severe winter-erosion period has passed by the time spring lentils are seeded, spring and early summer storms can still result in extensive soil erosion under these planting conditions.

An exception to the predominant use of conventional tillage in lentil production is no-till seeding of lentils into chemically-killed bluegrass sod. This is currently a successful and increasingly common practice in some of the bluegrass production areas of northern Idaho and eastern Washington. The availability of winter lentil varieties could increase this management practice.

Having the option of seeding a winter lentil under conservation tillage could greatly reduce erosion potential following crops other than grass. In addition, soil water storage could be increased as a result of reduced runoff and evaporation where a portion of the previous crop’s residue is left on the surface overwinter and through the early growth stages of the lentil crop. This could increase lentil yield potential in areas where water is a major yield limiting factor.

Lentils are a low residue-producing crop. Consequently, even a small portion of the previous crop’s residue maintained on the surface through the lentil crop will also aid in reducing erosion and increasing soil water storage during the following winter when the next winter wheat crop is seeded after the lentils. Conservation tillage seeding of winter cereals after lentils has generally been a successful practice in the Inland Northwest region.

Preliminary field research indicated that winter lentils perform well under conservation tillage systems, as well as under intensive tillage systems with low levels of surface residue. Spaeth and Muehlbauer found no significant differences in winter survival or yield of the WH80-bulk population of winterhardy lentils under no-till and intensive tillage treatments following spring barley in 1985 and 1986. The study was conducted at the WSU Spillman Agronomy Farm near Pullman. Intensive tillage treatments were plowed and disked before seeding. A Vogel double disk research drill was used to seed both the no-till and intensive tillage plots. Fig. 2 shows the similar stand, growth and maturity of WH80-bulk winter lentils seeded under both tillage systems in 1986.

Because winter lentil plants are small at the onset of winter, overwinter soil erosion potential would be high with winter lentils seeded into a finely-tilled seedbed without surface residue for protection. Consequently, the researchers recommend that winter lentils only be planted under a conservation tillage system.

The WH80-bulk lentil population was also included in a 1988-89 winter legume-tillage study near Troy, ID, in a 26-inch annual precipitation zone. Dave Huggins, soils research associate at Washington State University, and Bill Pan, WSU research soil scientist, conducted the experiment. The lentils were seeded directly into winter wheat stubble with a Lilliston double-disk no-till drill. Conventional tillage treatments, beginning with moldboard plowing, were seeded with the same drill.

Significantly more fall growth occurred in the no-till lentils than the conventionally-seeded lentils. Huggins and Pan attributed the increased fall growth under no-till primarily to a higher soil water content due to less evaporative water loss with no-till seeding. Despite this early growth advantage, the researchers found no significant differences in winter survival or yield between the two tillage systems. They also found that, under low soil water conditions in the fall, winter lentils had better stand establishment than did Austrian winter peas. In addition, winter lentils were found to be more winterhardy than the peas.

All four of the researchers speculate that planting winter lentils with conservation tillage, for soil water conservation and surface residue protection overwinter, would probably be more important in areas with less annual precipitation and harsher winter conditions than at Pullman and Troy. Under drier, more severe conditions, the presence of crop stubble could be more important for thermal insulation and snow cover to protect the winter lentil. Increased snow trapping and reduced evaporation overwinter would also increase soil water storage compared to winter lentil seedings after more intensive tillage. This could potentially expand winter lentils into areas drier than the traditional lentil production region.

The adaptation and management of winter lentils under conservation tillage in lower precipitation regions of the Inland Northwest is still largely speculation at this point. Prospects appear quite promising, although continued research and evaluation is needed.

Reduced Soil Compaction in Spring

Soil compaction can be a significant production limitation in the Northwest and is also believed to be an important contributor to soil erosion. Since potential for soil compaction sharply increases with increasing soil water content, spring field operations can significantly increase soil compaction problems. Growing more winter crops such as winter lentils, winter peas and winter rapeseed reduces potential for soil compaction. These crops are usually seeded when soils have a lower water content than in the spring and, consequently, reduce the potential for soil compaction.

Avoiding Delays in Spring Seeding

Another crop production limitation which may be overcome with winter lentils is wet spring soil conditions which delay spring seeding and consequently reduce yield potential. Production areas in higher annual precipitation zones (25 inches or more) in the Inland Northwest, such as the Nez Perce and Camas Prairie regions north of Grangeville in northern Idaho, commonly have prolonged periods of wet soil in the spring. This limits timely spring field work and planting of spring crops. Having the option of planting a winter lentil could increase cropping options for producers under these conditions.

Expansion of Lentil Production Area

In addition to providing producers in the current lentil production region with a fall vs. spring seeding option, winter lentils could expand the lentil production area in the intermediate precipitation zone (14 to 18 inches annually), where summer fallow is commonly used 1 out of 2 or 3 years or more. With no-till or minimum tillage seeding of winter lentils, Muehlbauer feels there may be a potential to substitute lentils for summer fallow, particularly with small red lentils.

This prediction is based partially on a recent research effort by Muehlbauer with small red spring lentils. In the last 3 years, Muehlbauer has documented good yields of small red spring lentils after winter wheat on the WSU Wilke Research Farm in a 16-inch annual precipitation zone near Davenport, WA. Small red lentils, which are about half the size and weight of the large yellow lentil commonly grown in the Palouse region, appear to be better adapted to lower precipitation areas than the yellow lentils. A new variety of spring small red lentils called “Crimson” was developed by Muehlbauer and should be available as foundation seed by spring 1991.

Muehlbauer points out that lentils area low water consumptive crop, thus potentially enabling recropping with winter cereals. Additional research is needed to explore the feasibility of substituting spring or winter lentils for summer fallow in the intermediate precipitation zone. Maintaining adequate seedzone water for winter wheat establishment is one important concern that needs to be addressed.

Muehlbauer adds that, as a legume, small red lentils can usually only fix about enough atmospheric nitrogen (N) to meet or slightly exceed their own N requirements. He estimates that small red spring and winter lentils would fix an average of 20 pounds N/acre for the following crop in the 14- to 18-inch precipitation area, The actual amount would depend on the initial level of soil N available and growing conditions. The higher the soil N level, the smaller the amount of N fixed by the lentil crop, since it readily utilizes available soil N. He also points out that about 40 pounds of N are removed from the field with every 1,000 pounds of harvested lentils.

The lentil crop can help maintain soil N availability in the cereal root zone by capturing mineralized N released from decomposing organic matter in the soil before it can be leached below the root zone or lost in other ways, This N in the lentil residue is then rapidly released during microbial decomposition, largely becoming available by or during the following spring. Decomposition and nutrient release from lentil residue is only slightly slower than for the more-succulent pea crop.

Small red lentils also have encouraging marketing prospects. The Palouse region of eastern Washington and northern Idaho produces more than 95 percent of the total U.S. lentil production. The predominant type grown is the large-seeded yellow lentil, which is preferred in western Europe and Central and South America. Muehlbauer points out, however, that small red lentils are the preferred lentil type in about 75 percent of the world lentil market, with the greatest demand in North Africa and the Middle East. He stresses that currently there is no open market demand for small red lentils from this region and encourages interested growers to pursue contracts directly with seed processors before planting.

Reduced Disease Incidence

Including non-cereal crops, such as winter or spring lentils, in the crop rotation helps reduce the incidence of some cereal diseases. For example, planting winter wheat after lentils can help reduce the impact of Pythium root rot and Rhizoctonia root rot, compared to planting after wheat or barley, A 3-year crop rotation, such as winter wheat-spring cereal-lentil, would effectively control Cephalosporium stripe in winter wheat. Including 1 year of a non-cereal crop in the rotation will control take-all disease of wheat. In general, a longer crop rotation will typically improve plant health and yield potential for all crops in the rotation.

Preliminary Conclusions

Although the research results are preliminary, the researchers encourage growers to follow the development of winter lentil varieties and to begin considering how they might incorporate the crop into their rotation. Yields of winter lentils should be at least equivalent to spring lentil yields. Availability of winter lentils would have additional advantages of facilitating the adoption of conservation tillage systems, and avoiding soil compaction problems and seeding delays due to wet soil conditions in the spring. In addition, small red winter (and spring) lentils may offer growers a cash crop alternative to summer fallow under conservation farming systems in the intermediate precipitation areas. Research efforts on winter lentil varietal development and production management, such as weed control strategies, disease and insect control, and cultural practices, will be expanded in the future.