The 2012 ASHS Annual Conference

One of the biggest challenges that Midwest vegetable growers face is the unpredictable weather and narrow seasonal window for crop production. The risk of frost damage and low soil and air temperatures during the growing season are major constraints for vegetable production. Strategies that help extend growing seasons are imperative for successful production of fresh and quality produce. This study investigated the effect of row cover and calcium application on fall lettuce (Lactuca sativa L. ‘Ermosa’) production at the Horticulture Research Station, Iowa State University, Ames, IA. The study comprised of a randomized complete-block design with following treatments: 1) 50 mM calcium; 2) 100 mM calcium; 3) row cover; 4) no cover; 5) 50mM calcium+row cover; and 6) 100mM calcium+row cover. Calcium was applied in weekly intervals, twice during transplant production phase and three times in the field to add up to 50mM and 100mM concentrations. Three week old lettuce transplants were transplanted on 3 Oct. 2011 on raised beds covered with black plastic mulch. A medium weight row cover was installed over the row cover treatment one week after transplanting. Row cover increased the air temperature by 4 °C to 5 °C than the ambient air temperature. Row cover and row cover-calcium treatments significantly increased marketable weight. Marketable weight ranged from 0–2.3 kg. Row cover, 50mM calcium+row cover, and 100 mM calcium+row cover treatments produced higher yields than all other treatments; however there were no statistically significant differences between them. Plants in the 5mM calcium+row cover and 100 mM calcium+row cover treatment produced the highest dry weight. Row cover treatments significantly increased plant leaf area when compared to treatments that did not have row covers. Our idea to include treatments with calcium applications but without row covers was to test the hypothesis that calcium would provide some degree of cold tolerance since it is an integral component of cell wall. This hypothesis did not stand true as no marketable heads were produced in 50mM or 100mM calcium treatments. Plants under row covers performed the best, and the effect of row cover was enhanced when used in combination with foliar calcium application. This study shows that by utilizing tools such as row covers and a combination of row cover and calcium foliar applications, growers can extend their growing season and grow an additional lettuce crop that could be harvested well into November.