Effects of bag-controlled slow release of calcium fertilizer on Ca absorption in grapes

Abstract:【Objective】In recent years, the softening berry phenomenon is frequently observed in some vineyards of Henan province when the berries approach to the maturity stage. The softening berries displayed soft flesh with poor flavor and for some hard-flesh varieties, they could not even be eaten, which brought great economic losses to the grape production. Compared with normal berries, the calcium content of soften ones decreased significantly. Therefore, calcium supplement to grape berries is the key to solving this problem. In grapes, the bud break happened late but the current shoots grow quickly with berries and shoots growing simultaneously, resulting in an intensive competition for calcium. After berry enlargement, the transpiration ability of grape berries decreased, so that calcium competitive ability was significantly lower than that of leaves. Fertilizer containing calcium was applied to soil by spread application to increase soil calcium concentration. To reduce labor costs, fertilizer was spread-applied at once. In this way, calcium is easily fixed in soil, resulting in an insufficient calcium supply during thelater stage of grape berry development. The bag-controlled slow release of fertilizer could control the velocity of nutrition release and provide nutrition steadily, which has been well applied in fruit production. In order to solve the symptom of softening fruit caused by calcium deficiency, the present experiment was carried out.【Methods】Six-years old self-rooted Summer Black grapevines were used as material, on which the softening berries were seen for two consecutive years. The experiment included the following 4 treatments: (1) spread application of calcium fertilizer once, (2) spread application of calcium fertilizer twice, (3) bag-controlled slow release of calcium fertilizer, and (4) no calcium fertilizer application (CK) . Soil samples were collected regularly after fertilization to measure total calcium and exchangeable calcium concentrations in soil. The destructive sampling of grape plants was carried out in young berry period, berry swell period, berry color setting period and berry maturation period. The calcium concentrations and contents of different organs of the plant were measured.【Results】Application of calcium fertilizer increased the concentrations of total calcium and exchangeable calcium in the soil where plants with softening berries grew. The spread application of calcium fertilizer once decreased the concentrations of total calcium and exchangeable calcium in the soil with time. The change of total calcium and exchangeable calcium concentrations in bag-controlled slow release of calcium fertilizer was insignificant, and the total calcium and exchangeable calcium concentrations in soil showed a stable range. The berry biomass of with the bag-controlled slow release treatment was significantly higher than that with the control (CK) . The difference in the biomass of perennial organs was not significant among 4 different fertilizer treatments. The highest concentration of calcium was found in roots, followed by leaves and the lowest berries. The calcium concentration of fruit decreased gradually with plant growth and development proceeding, while the calcium concentrations of the additional organs changed little with plant growth and development. The calcium concentration in leaves with bag-controlled slow release treatment was significantly higher than that with the rest treatments during berry swell period, fruit color setting period and berry maturation period, and there was no difference among4 treatments during young berry period. The calcium concentration in berries with the bag-controlled slow release treatment was significantly higher than that with the rest treatments. Root was the most important calcium-retaining organ, followed by leaves. The calcium content in the root system changed little, but the calcium contents in the leaves increased gradually with plant growth and development proceeding. From the young berry period to the berry swell period the calcium content in the leaves increased mostly, and the increase amount was 50% more than that during berry maturation period. The calcium content in the berries increased gradually with the growth and development proceeding, and from the young berry period to the berry swell period the calcium content in the leaves increased mostly. The increasing amount was 50% more than that during berry maturation period. The calcium contents of leaves and berries with bag-controlled slow release treatment were significantly higher than those with the rest treatments. The firmness and soluble solids concentrations with bag-controlled sloe release treatment were 506.84 mg · cm-2 and 20.2%, respectively, which were significantly higher than that with the control (CK) .【Conclusion】The bag-controlled slow release of calcium fertilizer treatment showed a good efficacy of controlling calcium release slowly. The calcium supply in the soil was steadier and more sustained throughout the grape growing season. The results suggested that the bag-controlled slow release of calcium fertilizer was beneficial to the grape bearing, which increased the calcium concentrations in various organs of grape plants, the amount of calcium absorption in late berry growth stage, as well as berry firmness and soluble solid contents.