Post-harvest is a key moment in the vegetative life of deciduous fruit trees and can be used to prepare the production for the next season.
Fertigation , that is , the application of fertilizers through drip irrigation, is a very useful and powerful tool that allows you to give plants the nutrients they need, in the right amount, where and when they really need them.
However, in many cases this magnificent tool is wasted by using the same types of fertilizers and the same way of distributing them as when only flood irrigation existed.
There is a key moment in the vegetative life of deciduous fruit trees that, through fertigation, we can take advantage of to prepare for the next season's production. This is the post-harvest period, understood as the time from the end of the harvest until the leaves fall.
As explained to us by the technical team at Agrostock Group , experts in plant nutrition, some of the reasons for the importance of post-harvest management are the following:
- When nitrogen is applied post-harvest, the tree primarily transports it to its storage organs (60 to 80% of the nitrogen absorbed in autumn), making it more readily available the following season for initial leaf and flower growth. Conversely, if applied entirely in spring, it can lead to excessive vegetative growth, resulting in reduced fruit quality and depleted nitrogen reserves.
- Studies carried out on peach trees with isotopically labeled nitrogen have shown that all the tree's growth during the first 30 days after budding comes from using the reserves stored in the tree, as the roots are unable to take advantage of nutrients from the soil before this time (the roots do not begin to be really active until the temperature in the first 50 cm of soil reaches an average temperature of 15ºC).
- Available studies also show that fertilization in autumn causes an increase in nitrogen concentration in perennial organs but not in senescent leaves, indicating that the reserves are made up of nitrogen applied in the last few weeks.
- In cherry and almond trees, if we apply foliar boron in September, it moves towards the bark and in spring, through the phloem, it passes from the bark to the flowers.
- In young trees the response to post-harvest fertilization is greater, since they have a lower capacity to remobilize nutrients from the leaves to the storage organs, before autumn senescence.
Furthermore, at this time of year it is important to stimulate the root system to make the most of nutrient applications and increase the trees' reserves for next year, as explained by the Agrostock Group technical team in this video:
Closing remarks
As a general recommendation, Agrostock Group suggests that fertilization should be carried out approximately 45 days before leaf fall. Nitrogen and potassium should be applied to all species, as these elements are highly mobile throughout the plant's vascular system. Phosphorus, however, is only essential when soil levels are very low or root health problems arise. Its application in the form of phosphoric acid, included in a complex fertilizer, will acidify the soil moisture, which is always beneficial in our alkaline soils.
A good post-harvest fertilizer application , through fertigation, should contain between 10 and 25% of the crop's total needs. The amount of nutrients applied will be deducted from the applications required in the following season.
In addition, boron, zinc, and manganese, essential micronutrients for the following year's flowering, should also be applied via foliar application if leaf levels are low.
Applying iron chelate is also recommended if chlorosis appears in September. Post-harvest fertilization is most important in early varieties and young trees, as it will determine a good start to the following season.
