Small Red Lentil as a Fallow Substitute

Chapter 8 – Crops and Varieties, No. 10, Spring 1989

Roger Veseth

Small-seeded red lentils may provide growers in the 14 to 18-inch (intermediate) precipitation area of the Inland Northwest with a viable cash crop substitute for summer fallow in the rotation. This is the preliminary conclusion of Fred Muehlbauer, research geneticist with the USDA Agricultural Research Service (ARS) at Washington State University in Pullman. Muehlbauer and Rick Short, his ARS research associate, have recently documented good yields of small red lentil after winter wheat on the WSU Wilke Research Farm in a 16-inch annual precipitation zone near Davenport, WA. The small red lentil, which is about half the size and weight of the large yellow lentil commonly grown in the Palouse region, appears to be better adapted to lower precipitation areas than the yellow lentil.

Summer fallow is commonly used every other year or every third year in the crop rotation in areas with intermediate annual precipitation. Based on the preliminary results of the first 2 years of their study, Muehlbauer feels that small red lentils may merit consideration as a fallow substitute by growers, He offers five possible reasons for considering small red lentils:

1. They have shown promise as an alternate crop with good yield potential in this intermediate precipitation zone.
2. They have encouraging marketing prospects.
3. They area low water consumptive crop, thus enabling recropping with winter cereals.
4. They require no nitrogen (N) fertilizer.
5. They are adaptable to conservation tillage systems.

Traditional Production and Markets

The Palouse region of eastern Washington and northern Idaho produces more than 95 percent of the total U. S. lentil crop. 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 the small red lentil is the preferred lentil type in about 75 percent of the world lentil market, with the greatest demand in North Africa and the Middle East. In addition, Muehlbauer explains that there is reason to believe that the demand for small red lentils will increase substantially within the next 5 to 10 years when some irrigation projects are completed in a major small red lentil production area in Turkey. Once they are completed, those areas of Turkey will most likely reduce production of small red lentils and increase production of crops that are more responsive to irrigation.

Muehlbauer also explains that the expanded production of small red lentils in the semi-arid region of the Northwest would not beat the expense of the traditionally grown large yellow-type lentil. Yellow lentils generally have higher production potential than small red lentils in the higher precipitation areas where they are traditionally grown. Conversely, small red lentil production has been higher than yellow lentils in the intermediate precipitation areas. Also, since small red lentils have a different market than yellow lentils, increased production should not increase supplies and consequently lower yellow lentil market prices.

Yield Trials

Muehlbauer and Short completed 2 years of yield trials with small red lentils on the WSU Wilke Research Farm near Davenport in 1987 and 1988. A selection of small red lentil lines were included in the experiments, along with Redchief as a check. Redchief is a large-seeded red cotyledon variety currently grown on limited acreage in the Palouse. Much of the genetic material included in the trials was originally collected in Turkey. A yield trial of yellow lentil varieties and breeding lines was also grown on the Wilke Farm each year for comparative purposes.

Table 1 shows a yield comparison of selected red lentil lines and some common commercial yellow lentil varieties in these trials. In 1987, yields of the red and yellow lentils were quite similar. However, in the dryer 1988 crop year, red lentil lines outperformed the yellow lentils. Muehlbauer points out that this indicates that small red lentils are more drought tolerant and consequently better adapted to the lower precipitation fringe of the traditional lentil producing area in the Palouse and similar Inland Northwest areas.

Table 1. Selected comparison of yields of small red, large red and large yellow lentils at the Washington State University Wilke Research Farm In 1987 and 1988 near Davenport, WA (Muehlbauer and Short, USDA-ARS, Pullman).

Potential Varietal Releases

Two small red lentil lines have had the highest yields over the widest range of environments in regional trials the last 3 years. These area selection from Giza 9, tentatively named “Crimson,” and LC460007, a hybred line from Muehlbauer’s breeding program. Crimson is being proposed for release as a variety this year, and foundation seed should be available for the 1990 crop season. It had better decortication (seed coat removal) and splitting quality than LC460007, which was the final determining factor in choosing which line to propose for release as a new variety.

Water Consumption

Muehlbauer points out that the small red lentil is a relatively low water consumptive crop. He estimates that most of the water use is from the upper 2 to 3 feet of soil, although roots can grow to about 4 feet in depth, Winter wheat commonly has an effective rooting depth of 4 to 6 feet or more, and extracts substantially more water from the soil profile than lentils.

Unused soil water remaining after the lentils would be available for the following winter wheat crop. In addition, overwinter water storage with conservation tillage practices which help reduce runoff and evaporation should adequately recharge the stored soil water level for the following winter cereal, About 65 to 75 percent of the annual precipitation in this Inland Northwest region occurs during the fall and winter months. Consequently, Muehlbauer feels that the red lentil production in place of summer fallow should not adversely affect the production potential of the following wheat crop in the intermediate precipitation zones.

Fertility and Fertilizers

No fertilizer was applied with the research plantings of small red lentils. Muehlbauer explains that, as a legume, small red lentils can fix about enough atmospheric N to supply their own needs. He estimates that small red lentils can fix up to about 50 pounds N per acre depending 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. An average amount of N fixed for the following crop in the 14-to 18-inch precipitation area would probably be about 20 pounds N per acre. He also points out that 1,000 pounds of harvested seed contains about 40 pounds of N.

The lentil crop can help maintain soil N availability by capturing mineralized (released) N from decomposing organic matter in the soil. This N is then released rapidly during residue decomposition, much of which is available by the following spring, Decomposition and nutrient release from lentil residue is only slightly slower than for the more succulent pea crop.

A seed treatment with molybdenum may be needed in some areas with low soil levels of molybdenum. Inoculation of the seed with the proper rhizobium for nitrogen fixation is also important, particularly in areas which have not grown peas or lentils in the past.

Planting Considerations

Muehlbauer suggests that growers plant small red lentils as soon as spring field conditions permit in the 14to 18-inch precipitation areas. Plant stress from heat and dry soil prematurely induces the reproductive phase and seed set more in small red lentils than in most other crops. The small red lentil is susceptible to frost damage with early seeding. However, the plants will usually have adequate regrowth after the frost to out produce plantings made after the danger of frost has past. He stresses that the heat and drought stress on later plantings would usually limit yield more than any frost damage because of early planting.

A 12-inch row spacing was used in the small red lentil trial to allow individual row harvesting. Row spacing for lentils in the traditional production area in the Palouse region is typically 6 to 7 inches. Muehlbauer recommends these narrower row spacings in order to avoid excessive soil water evaporation and intra-crop competition in intermediate precipitation areas. More research is needed to help determine optimum row spacings for the crop in these dryer areas.

Herbicide application and other weed management practices for small red lentils would be the same as for the large yellow lentils. Muehlbauer points out that an additional advantage of lentils and other non-cereal crop in rotation is that they help provide additional options for control of grassy weeds.

Conservation Tillage Practices

A crop of small red lentils can be an effective option for conservation farming systems with proper management of the residue of the preceding wheat or barley crop and the lentil crop. The reduced tillage system used in the small red lentil research trials, after winter wheat, at the WSU Wilke Farm included the following operations: fall chiseling, spring field cultivating, harrowing, seeding with a double disk drill and rolling. Muehlbauer estimates that approximately 1,000 pounds per acre wheat residue (about 25% of the original 4,000 punds/acre) or 50 percent cover remained on the surface after the lentils were seeded and rolled. He points out that by leaving most of the wheat residue on the surface overwinter and maintaining a significant portion of the surface residue through seeding of the lentils, runoff and evaporation can be reduced. This improves soil water storage, and thus increases the lentil yield potential.

Muehlbauer also points out that since lentils area low residue producing crop, the cereal residue maintained on the surface through the lentil crop will aid in reducing runoff and erosion 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 very successful practice in the Inland Northwest region.

Reduced Disease Incidence

Including non-cereal crops, such as lentils, in the crop rotation can help reduce the incidence of some cereal diseases. Planting winter wheat after lentils can help reduce the impact of Pythium root rot and Rhizoctonia root rot, compared to planting after another cereal crop. A 3-year crop rotation, such as winter wheat-spring cereal-lentil, would effectively control Cephalosporium stripe in winter wheat. Including 1 year of non-cereal crop in the rotation will control take-all disease of wheat, which can occasionally be a problem in the intermediate precipitation areas. In general, a longer crop rotation will improve plant health and yield potential for most all crops in the rotation.

Marketing

Muehlbauer stresses that currently there is no open market demand for small red lentils from this region. He encourages interested growers to pursue contracts directly with seed processors before planting.

Preliminary Conclusions

Although these results represent only 2 years of research, Muehlbauer encourages growers to follow the development of new small red lentil varieties and begin considering how they may incorporate the crop in their rotation. He feels that small red lentils may offer growers a low input cash crop alternative to summer fallow under conservation farming systems in the intermediate precipitation areas. His research efforts with small red lentils at the WSU Wilke Research Farm will continue in 1989.