By: South Fruit Growing Center
The Chilean cherries, to be exported, they must withstand long travel and storage times, maintaining quality characteristics. Calcium is a very influential factor In achieving this goal, however, its transport to the fruits is usually limited and defined within a few days.
This compound is an extraordinarily important mineral for the quality of cherries, especially in firmness, since among the Main causes of softening and other associated disorders, a high concentration of nitrogen (N) is found, as well as low concentrations of calcium (Ca) in the fruit. From this it follows that the probability of occurrence of these problems increases with a high nitrogen/calcium ratio in the fruit. Consequently, management techniques should aim to keep the N concentration under control and to maximize the Ca concentration in the fruit.
The main role of calcium is to preserve the integrity of the cytoplasmic membrane and confer resistance to the cell wall, since it is a main component of pectates (pectins), which form part of the middle layer between neighboring cells and cement the union between them.
Ca from the roots is “loaded” into the xylem vessels. In the xylem, Ca is rapidly transported by the mass flow caused by the transpiration current towards those organs that transpire. Since the leaves correspond to the organs with the greatest transpiration, most of the Ca will go towards them. If water stress occurs at these times, the leaf stomata close, cutting off the exit of water via transpiration and thus stopping the ascent of calcium, as well as that of other minerals. Therefore, water stress is directly related to nutritional stress.
Factors predisposing to softening:
–Varieties: Among the most prone are, for example, Early Burlat, Pigeon Heart, Lapins, Santina, Bing, Sweet Heart, Regina and Kordia.
–pH: In soils with values below 6, subacid or acidic, calcium salts form other more soluble molecules and are susceptible to loss through leaching. This situation is more frequent in soils in the southern region of Chile.
–Fertilization: With a high presence of competing cations with Ca, such as potassium (K+), magnesium (Mg++) and ammonium (NH4+). This is very easily avoided, since the opportune moment of application of these elements does not coincide with that of Ca.
–Excess vegetative development: (Often related to an overabundance of N) This is because Ca moves through the transpiration stream, vegetative growth will promote the flow of Ca mainly towards leaves and shoots to the detriment of the fruit.
Opportunity: Time to accumulate Calcium
From fruit set until the fruits reach a size of about 5 to 8 mm, there are migrations of Ca towards them, because their maximum transpiration occurs in the initial phase of their development. Migration can be increased if the concentration of Ca in the xylem liquid is high, which is achieved through the fertilization and the accumulation of good reserves.
After cherries reach 5-8 mm, xylem functionality drops substantially and Ca concentration begins to decrease in the fruits due to a dilution effect. As can be seen, the The time available for accumulating calcium in them is short, no more than 10 to 15 days. (depending on the growing area).
The strategy to increase calcium flow to the fruit should be focused from pre-flower until the fruit reaches 5 to 8 mm in size, fertilizing the soil heavily with Ca.
Why from pre-flowering? Download the full article here!
This note was made based on the article published in RedAgrícola by the Dr. Jose Ignacio Covarrubias, a plant nutrition specialist and academic at the Department of Agricultural Production of the Faculty of Agricultural Sciences of the University of Chile (UCHILE).
For more information about the PTEC66647 Program South Fruit Growing Center Contact Claudia Jorquera [email protected] or Alejandra Vinegar [email protected]
