The latest optimal planting date will determine how much time growers have for lupin seedbed preparation after rice harvest.

Data from a planting date study show that lupin seed yields are highest when planting is done in later October or early November.

Planting date affected yield of the late maturing cultivar Multolupa more than it did the early maturing cultivar Ultra. However, for October 29 and November 10 planting dates, Multolupa produced an average seed yield of 5,250 pounds per acre, which was 20 percent greater than the yields from Ultra for the same planting dates.

Seed Yields Suggest Profitability

Economic feasibility of lupin production will depend primarily on  seed yield, because no nitrogen fertilizer is needed and irrigation needs are similar to those for wheat.

Yields of five cultivars planted on October 26 ranged from 4,300 to 4,635 pounds per acre. In general, yields in 1987 were lower than those from a similar experiment in 1986. Most likely, this was because of an extended heat wave in May 1987. However, the late maturing cultivar Hamburg had the highest yields in both years. Other cultivars in the studies included late maturing Multolupa and the early maturing cultivars Buttercup, Kievskij, and Ultra.

There is potential for an average field-scale yield of 5,000 pounds per acre for white lupin with a cultivar such as Hamburg. A seed selling price of $150 per ton would provide a gross return of $375 per acre. In comparison, a 7,000 pound per acre wheat crop selling for $100 per ton would provide a gross return of $350 per acre and would require at least 100 pounds of nitrogen per acre with either Anza or Yolo cultivars.

Nitrogen Fertilization Proves Unnecessary

Experiments with two high yielding, early maturing lines and two  high yielding, late maturing lines planted on October 25 show that symbiotic nitrogen fixation provides adequate plant nutrition. Nitrogen fertilization at a rate of 250 pounds per acre did not increase yields.

The 1987 data for seed protein are still being analyzed, but data from 1986 show that inoculation with Rhizobium, which costs about $4 per acre, increases seed protein to levels comparable with those produced by nitrogen fertilization. Thus, inoculated white lupin (which produces a seed protein content approximately 80 to 85 percent of that produced by soybean) could become a viable alternative to production of bread quality wheat, which requires 100 to 200 pounds of additional nitrogen per acre. Lupin also may be a profitable winter legume silage crop.

The 1986 data also suggest that lupin would provide no net input to soil nitrogen levels if the seed was harvested but would remove less soil nitrogen than a 6,500 pound per acre wheat crop fertilized with 120 pounds of nitrogen per acre.
 

Lupin Adds Rotation Alternative Rice growers who farm along the fringes of the Sacramento Valley have long had an interest in increasing the number of cropping options following fall harvest from the traditional alternatives of wheat, sugar beets and tomatoes. It appears now they may get their wish. UC Davis agronomist Ken G. Cassman (r) and UC Davis graduate student Kevin J. Larson examine white lupin. White lupin, a nitrogen-fixing legume, may become a viable option. Project leader and UC Davis agronomist Ken G. Cassman noted that the highly efficient plant can produce a high protein seed to compete with soybean protein. Cassman credits graduate student Kevin J. Larson with carrying out the details of the project's three objectives: to assess the suitability of white lupin as a rotation crop; to quantify its yield potential in relation to planting dates and maturity; and to quantify the seed protein yield, nitrogen fixation and residual crop nitrogen returned to the soil. "We wanted to identify an alternative crop that would increase the grower's options," Cassman explained, "and to assess whether there is any subsequent benefit to the rice crop." Lupin was an attractive candidate because, as a legume, it has the ability to fix atmospheric nitrogen at self-sustaining levels. Most cereal crops, on the other hand, require additional nitrogen. Cassman noted that the vast majority of the nitrogen is translocated to the seed, making it a potential feed alternative to Midwestern soybeans. "The problem is the market is so large that production hasn't yet reached critical mass," he said. "Nonetheless, based on these results, we can say that lupin has the yield potential to justify further efforts to bringing this crop into production."