Available at: https://digitalcommons.calpoly.edu/theses/68
Date of Award
MS in Agriculture - Soil Science
Terry Smith, PhD
The importance of trace elements nutrients to vegetable crops has received more attention in recent years. Accordingly this experiment investigated the benefit of foliar applied copper fertilizer on romaine lettuce (Lactuca Sativa Longifolia) grown in low soil Copper (Cu) concentration in the coastal Santa Maria, California. The various rates of Cu fertilizer applied include untreated (control), 100, 200, 400 and 800 grams per acre of CuSO4.5H 2O, using a one time and a split application methods. Three consecutive individual experimental fields were established starting in late spring through the fall of 2008. The soil texture was a loam in all three of the experimental fields. Positive responses in weight increase were found due to these treatments, however was not statistically significant. The maximum responds in weight increase was identified with the one-time application of 200 and 400 grams/acre of CuSO4 but weight decline was observed at the higher rates of 800 grams/acre. The optimum weight increases were between 4.4 and 6 percent higher than the untreated plots. The treatments significantly increased the uptake of Cu by plants (pvalue <0.001). When analyzed collectively, significant difference was found in plant weights between the three experimental fields. Crops harvested one week earlier than scheduled produced 21% lower mean weight than those harvested on time. No apparent physical damage was identified in plants having leaf cu concentrations exceeding the suggested toxic level of 150 ppm but weight decline was observed thereafter. In 2009 an additional experimental field was established in a sandy loam, 8% clay and was completed in March. Rate of applications was modified to include untreated control, 200, 400 and 500 grams/acre, at one time application only. Again Positive responses in weight increase were found due to these treatments, however was not statistically significant. The optimum result in weight increase was found with the application of 200 grams/acre of CuSO4. The overall mean weights of the plants were comparatively higher than that of the three previous experimental fields. The weight increase was 7.5% higher than the untreated plots. Key Words: Foliar; CuSO4.5H 2O (Cu Sulfate Pentahydrate); Trace elements nutrients.