Lesquerella press cake as an organic fertilizer for greenhouse tomatoes

Lesquerella press cake is a co-product generated during the processing of the new oilseed crop lesquerella [Lesquerella fendleri (A. Gray) S. Wats.]. Developing commercial uses for the press cake would increase the profitability of growing lesquerella. The press cake contains levels of nutrients which should make it an excellent organic fertilizer for container-grown plants. Tomato (Solanum lycopersicum L. ‘Red Robin’) plants were grown in potting mix supplemented with a standard chemical fertilizer mix or either lesquerella press cake or cottonseed meal at rates of 2.5, 5.0 and 10.0% (w/w). Both of the organic fertilizers had only minor effects on the physical properties (bulk density, total porosity percentage, total solids percentage, pH, EC) of the potting mixes with increasing rates, although there was substantially less shrinkage of media amended with 5 and 10% press cake than with the same rates of cottonseed meal. At rates of 10.0% for press cake and 5.0% for cottonseed meal (which supplied similar substrate nitrogen levels), plant heights, total tomato yield per plant and number of fruit per plant were equal to that of the chemically fertilized control. There were no differences among treatments for average fruit weight. Chlorophyll content was generally similar among the treatments during the course of the experiments, with a trend towards lower values for the 2.5% rates of press cake and cottonseed meal near the conclusion of the experiments. From these results it appears that lesquerella press cake may be a useful organic fertilizer for container-grown tomatoes.