Effect of Urea Application as a Top Dressing on Development of Black Heart Disorder of Mauritius Pineapple (Ananas comosus L.) During Cold Storage

Pineapple variety “Mauritius” has a high export demand due to its characteristic flavor. However, the demand cannot be fulfilled due to internal browning that occurs during sea freight especially when the storage period under refrigerated condition at 10-120C is extended more than two weeks. The inherent nature of poor distribution of calcium around core area causes this disorder. Some evidences are available on prevalence of this disorder even before 2 weeks in refrigerated storage, if urea fertilizer is applied as a top dressing exceeding the recommended level. This study was conducted to find out the effect of urea application as a top dressing on Black Heart Disorder of pineapple during simulated sea freight conditions. urea was applied as top dressing to leaf base of plant when fruits were at one month after flowering. The level of urea applied was 10 and 20 g per plant and control plots were arranged in completely randomized block design with three blocks in farmer field at Attanagalla, Gampaha district. Except the top dressing all other requirements were provided based on the recommendations of Department of Agriculture. Fruits were harvested at green mature stage and were stored in a pre- cooled refrigerator maintained at 12 oC for 15 days. Subsequently, fruits were transferred to ambient temperature and shell colour development, intensity of black heart disorder and physico-chemical parameters were recorded after 2, 4 and 6 days. Results showed that application of urea 20 g / plant enhanced black heart disorder compared to other treatments. It was also observed that nitrogen level of fruit tissues of these fruits were significantly higher than the control and the urea applied at 10 g/ plant. In addition, significant reduction of ascorbic acid and pH was also observed with 20g/plant urea application.