Transition between postharvest and entry into dormancy

Transition between postharvest and entry into dormancy

Once the harvest is over, attention is normally focused on the shipping of the fruit, how it arrived at its destination, prices, quality and commercial matters. However, post-harvest is the beginning of the next season and does not refer only to the completion of the harvest, but also to the post-harvest of the trees, a physiological change in the plants. The physiological postharvest responds to some ecological stimulus and is more or less between 80 to 150 days after full flower.

Paying special attention to the garden during the post-harvest is essential, since during this period many technical, physiological, and metabolic processes occur, such as the development of roots that will provide reserves for the next season; the formation of flowers in the new fruit centers and the recovery of these in the permanent fruit centers; the uptake that plants have of CO₂ and build reserve sugars through photosynthesis, releasing water into the atmosphere, among others.

This cycle generates all the reserve levels that will support the following season, the first 40 days from full flower onwards, and that is directly related to productive and technical factors that cannot be ignored.

Among these factors is the monitoring of spider mites, so that they are not a cause of early defoliation in the orchards and have a negative point in the interruption of all the physiological metabolisms of plant cooling and CO₂ uptake to obtaining sugars; Everything related to the topic of root biostimulation, foliar and soil nutrition and irrigation is also relevant, considered one of the most relevant factors during the post-harvest, since with a poor strategy and programming of this, everything that can be carried out carried out in parallel will be misused.

It should also be kept in mind that postharvest is the prelude to a new stage within the phenological development cycle of the cherry tree: dormancy, which will depend directly on what happens in the orchard during postharvest, agronomic management and the signals that are given to the plants, so that they understand that they are going to sleep.

Now, during the transition stage between post-harvest and dormancy, is the moment that marks the end of orchard recovery programs, both from a nutritional, soil and root point of view. On the other hand, foliar corrections must be finalized, based on the analysis carried out at the beginning of the post-harvest.

Dormancy, specifically, is the winter lethargy of plants, in which the accumulation of cold hours occurs, which are related to the use of the reserves that the trees have to start the next season, in pursuit of the objective productive of achieving its potential in terms of quantity, quality and condition of fruit.

It is essential to think in this period from both a physiological and theoretical point of view, since this stage can be defined in several ways. Physiologically, a plant begins dormancy when it has 50% fallen leaves (yellow leaf = fallen leaf) and it should be ensured that this coincides with November 1st, the date when the cold hour count officially begins.

Important signs for orchards

Irrigation is undoubtedly one of the main signals that must be given to cherry orchards for a correct entry into dormancy; The distribution of water must always be considered, and with more attention in this phase, beyond the amount to be replaced, in terms of evapotranspirative demand; take into account its decrease from the volumetric point of view of the soil, of the roots of the different rootstocks.

Below are a series of aspects to consider:

  • The plant’s atmospheric demand and water consumption are decreasing towards the end of August.
  • The demand is expressed in evapotranspiration and not in environmental temperature, which is why high temperatures in September or October are not comparable to those of the summer period, as they only last a couple of hours.
  • Starting in September, the nights and mornings are colder and wetter, which should be considered for reducing the frequency of irrigation towards this month.

It is necessary to keep in mind that the first important signal that declares dormancy is the summer solstice when the lignification and pre-dormancy processes begin, which in physiology is defined as “cold tolerance.”

The change in photoperiod influences various aspects; Annual materials that grow from the end of March already present lignified basal sections; The above also affects the beginning of flower induction; The plant enters a process of accumulating reserves, changing sap flow and begins to prepare for sleep.

On the other hand, the first autumn frost, which in physiology is known as “freeze resistance”, enhances and ensures dormancy; This occurs when there is already development of wood, secondary growth, and is the trigger for the plant to shed its leaves and voluntarily go to sleep.

It is always necessary to keep in mind what the plants should show prior to winter dormancy. In this context, orchards must show fruit centers with well-formed darts, very smooth bracts, even with the presence of leaves (the buds are always axillary to leaves), and as a general rule, present at least 50% of fallen leaves by November 1st, considering that yellow leaf is equal to fallen leaf.

That the plant begins its dormancy on this date will allow it to make the most of the winter lethargy and the accumulation of cold hours. Now, it must be considered that good dormancy is not only determined by the accumulation of cold, but also by how short the photoperiod is, that is, how much light there is.

But every season the same question arises: What to do if the aforementioned strategies do not provide an answer? If by October 20, the orchards do not have 10-20% yellow leaves, decisions must be made on how to accelerate this process, which will be decisive for the flowering of the cherries.

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