EFFECTS OF BIOMATERIAL AND SEMI-BIOMATERIAL ON GROWTH AND POSTHARVEST QUALITY OF BUTTERHEAD AND RED OAK LETTUCES Lactuca sativa L.

Abstract

This study aimed to increase the production of lettuce through the application of biomaterial from shrimp shell (SS) and semi-biomaterial from fermented chitinous material (FCM) both in a test plot and in a local farm. ‘Butterhead’ lettuce (Lactuca sativa L. cv. ‘Butterhead’) and ‘Red Oak’ lettuce (Lactuca sativa L. cv. ‘Red Oak’) were cultivated during three crop seasons in a test plot and two crop seasons in a local farm. In the test plot, SS and FCM were supplemented to the 10:1 soil/cow manure growing medium (T1) as following: 0.5% SS (T2), 0.5% SS with chitinase-producing Bacillus licheniformis SK-1 (T3), 0.25% SS and 0.25% FCM (T4), 2% (T5) and 10 mL of SK-1 alone (T6). The supplementations of SS and/or FCM resulted in significant increases in yield of ‘Butterhead’ and ‘Red Oak’ lettuces in all three crop seasons. When applied in a test plot during the first and third crop seasons, lettuces grown with the presence of T5 showed the highest increase in yield as evaluated in terms of fresh weight, dry weight, leaf number, and leaf width and length. Supplementation of T5 during the second crop season of ‘Butterhead’ lettuce also resulted in the highest increases in yield with the exception of leaf numbers which was second to those treated with T3. During the second crop season of ‘Red Oak’, the cultivation with the presence of T5 resulted in the highest increase in fresh weight and leaf numbers, while dry weight, leaf width was second to those treated with T2. Weight losses after storage at 8°C and 60% relative humidity (RH) for 2 weeks were significantly reduced in all treatments treated with SS or FCM in both ‘Butterhead’ and ‘Red Oak’ lettuces. During the first and third crops, T5 treatment of ‘Butterhead’ lettuce resulted in the lowest fresh weight loss except during the second crop season which was second to those treated with T3. In ‘Red Oak’, the lowest of fresh weight loss was found in the T5 treatment in all three crop seasons. The best overall appearance of ‘Butterhead’ lettuce was observed when T5 was applied during the first and third crop seasons, while during the second crop, T2 and T5 treatments showed a significantly better overall quality than those treated with other treatments. The best overall appearance of ‘Red Oak’ lettuce was observed when T5 was applied during all three crop seasons. In addition, during the first and second crop season both T4 and T2 treatments showed significantly higher overall quality as in the T5 treatment. FCM, the most outstanding treatment from the test plot experiment was used to test in a local farm. ‘Butterhead’ and ‘Red Oak’ lettuces were cultivated during two crop seasons. Twenty grams of the FCM per plant were supplemented to growing medium one week before and after transplantation compared to untreated soil (control). The supplementation of FCM resulted in significant increases in yield of ‘Butterhead’ lettuce as evaluated in terms of fresh weight in both crop seasons. During the first crop season ‘Butterhead’ lettuce showed a significant increase in leaf numbers, diameter of the lettuce head and fresh and dry weights. FCM treatment resulted in significant increases in yield of ‘Red Oak’ lettuce in terms of leaf numbers, leaf width, leaf length, and fresh and dry weights in both crop seasons. During both crop seasons, weight losses after storage at 8°C and 60% RH for 2 weeks were significantly reduced in FCM treatment in both ‘Butterhead’ and ‘Red Oak’ lettuces. ‘Butterhead’ lettuce treated with FCM showed significantly better overall visual quality than the control treatment during the first crop season. The finest overall lettuce appearance was observed in the FCM treated ‘Red Oak’ in both crop seasons. Our findings indicate that FCM with chitosan properties and high N content can promote growth and yield of ‘Butterhead’ and ‘Red Oak’ lettuces by affecting mineral allocation. Photosynthesis, transpiration rate and stomatal conductance of ‘Red oak’ lettuce in the FCM treatment were significantly higher than the control treatment during the second crop season. There was no significant difference in photosynthesis, transpiration rate and stomatal conductance of ‘Butterhead’ lettuce during both crop seasons. The results indicate that the application of 2% FCM is the best all-year-round supplement for ‘Butterhead’ and ‘Red Oak’ lettuce cultivation.