How can grapes be scientifically supplemented with calcium to improve fruit quality?

Calcium deficiency in grapes causes leaves to curl backward, new leaves to turn dark green, significantly increases the rate of fruit cracking, aggravates physiological disorders such as grape fruit shrinkage disease, reduces fruit firmness, and leads to poor storability. Therefore, calcium must be supplemented in a timely manner during grape growth. The peak calcium uptake period for grapes is at 1-3 weeks, and given the recent rainy and sunless weather in the Chongqing area, grape calcium supplementation should combine spraying and soil application.

Calcium fertilizer spraying should be carried out during the young fruit enlargement stage, that is, from 1 week after petal fall to the hard pit stage, applied 2-3 times consecutively at 7-10 day intervals. The calcium fertilizer should be water-soluble, highly concentrated, and easily absorbed, such as chelated calcium types. When spraying, choose windless or low-wind weather, spray finely onto the undersides of leaves, and focus on spraying the young tender parts of inflorescences and fruit clusters. To improve fruit firmness and marketability, calcium fertilizer should be sprayed once 10-15 days before grape harvest.

Soil application of lime not only supplements calcium but also disinfects. It is generally applied during winter orchard cleanup, and can be applied once more after grape flowering. Broadcast lime over the rows of grapes, then plow it in, using 50 kg per mu.