Growth and yield characteristics of Lesquerella fendleri as a function of plant density

There is little information available regarding the response of Lesquerella fendleri to planting density. The effects of plant density on growth, yield, and yield components of L. fendleri were studied in central Arizona at plant populations of 250000, 500000, 750000, 1000000, and un-thinned controls of 1658000 plants/ha in 1992-1993 and 1500000 plants/ha in 1993-1994. In the 1992-1993 tests, increasing density resulted in a significant decrease in plant width and number of branches, while causing an increase in taproot length in populations up to 750000 plants/ha. There were no effects on seed size; however, density significantly reduced the number of seeds/silique for the 750000 and 1658000 plants/ha treatments. Seed yield/plant and harvest index/plant were significantly reduced with increasing density, but yield/ha increased with density up to 1000000 plants/ha. At 1658000 plants/ha, shattering was excessive and resulted in loss of seeds. The greatest seed yields/ha were obtained at 750000 plants/ha and 1000000 plants/ha densities. The oil content did not vary significantly from 500000 to 1658000 plants/ha, but treatments in this range produced seeds with significantly higher oil content than the 250000 plants/ha treatment. Differences in oil yield/ha reflected differences in seed yield/ha. The 1993-1994 harvest did not show significant differences for seed and oil yields among density treatments. Higher temperatures in 1993-1994 were believed to increase the oil content and seed yield in the higher plant densities. Plant densities of 750000 and 1000000 plants/ha are recommended for lesquerella growing areas comparable to central Arizona. At these densities, maximum seed yields should be obtained even with annual temperature fluctuations. Also, maximum plant heights were obtained at these densities, minimizing seed loses during combine harvest.