Calcium application to lettuces : effects on leaf nutrient concentrations and quality
2000
Asiah A. M. | Ramlan M. F. | Tan, S. A. | Siti Aishah H. | Mahmud T. M. Mohamed
Water stress or osmotic stress, high atmospheric moisture and high temperatures often attribute to poor Ca absorption. In tropical climates, such conditions easily prevail especially in the protected environmental structures. However, by maintaining adequate supply of Ca in the root medium to certain levels could probably improve the absorption problems. Thus, this experiment was conducted to determine the effects of Ca rates supplied to the root on leaf nutrient concentration and quality of lettuce grown in environmental protective structures. The experiment was conducted using NFT system. Five rates of Ca were used: 70, 120, 170, 220 and 270 mgl-1 . Except for Ca, all plants received the following nutrient concentrations (mg.l-1 ): 225 N, 62 P, 309 K, 48 Mg, 64 S, 0.53 B, 1.3 Mn, 0.013 Cu, 0.05 Zn and 0.11 Mo. Treatments were arranged in RCBD with 3 replications. The incidence of leaf tipburn was first detected on plants receiving 170 mgl-1 Ca, 10.3 days after transplanting and the last was on plants grown at 270 mgl-1 Ca. However, the highest percentage of plants affected by leaf tipburn was recorded at the highest Ca level. Though the specific leaf area and leaf chlorophyll content were not significantly affected, the leaves were thicker at higher Ca. The ascorbic acid content was maximal at 170 mgl-1. The shelf life was longer with Ca rates. Plants were found to have high in nitrate and total N contents at lower Ca levels. Potassium, P and Mg accumulations were not significantly affected by Ca supply. Calcium absorption was improved with additional Ca in the root media. Results indicate that Ca at 170 mgl-1 is sufficient for quality but for leaf tipburn incidence the lower Ca is probably needed.
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