It is understood that the harvest marks the completion of an important stage in the cherry season, no less important than the one that follows. While it is the culmination of all the effort made throughout the past year, where we reap the rewards of all our work, the subsequent stage is equally, if not more, important, as it largely defines the behavior of the next harvest.
To highlight this stage and its importance, we must begin preparing for post-harvest as a key process in building for the next season. This extended summer period is crucial for accumulating carbon and nitrogen reserves, along with the induction (IF) and floral differentiation (DF) periods (Fig. 1).
Figure 1. Dynamics of root, fruit, and annual shoot development in adult cherry trees in Chile. Source: adapted from Bonomelli et al. 2013.
Floral induction (FI) begins at the end of spring, around mid-December in the Southern Hemisphere, and continues until the start of floral differentiation (FD) during the summer, sometimes even into the first days of March. This process involves the development of morphological and reproductive structures, primarily visible to the naked eye in the spurs, the most important morphological structure for the following season’s production.
For the optimal development of these structures, root formation, and reserve accumulation, special care must be taken to ensure the plant can spend the summer as comfortably as possible. During this time, climatic conditions can cause abiotic stress if proper management practices, such as irrigation, nutrition, and pest and disease control, are not followed.
Abiotic stress occurs primarily because plants, generally those with less vegetative development and/or insufficient irrigation, lack the capacity for continuous gas exchange with the atmosphere. This results in stomatal closure, preventing CO2 uptake for sugar production and resulting in malformed flower primordia in the fruiting centers. Consequently, fertility is reduced, and fruit malformations occur. The floral induction (FI) period begins approximately 70 days after full bloom (DDPF), and the floral differentiation (FD) period begins approximately 100 DDPF. Both processes are highly dependent on stable water, light, and temperature conditions in the plant during these periods of peak atmospheric demand.
Any stress-related anomaly during this period directly impairs the accumulation of reserves and, conversely, the formation and development of flower primordia in the fruiting centers, which will contribute to the following season’s production.
Therefore, it is at this stage that the application of sunscreens alongside algae-based products, such as Ascophyllum nodosum and Ecklonia maxima, becomes important.
The use of sunscreens combined with algae and their beneficial effect on plants has been investigated for years, leading to the conclusion that the application of kaolinite at a concentration of 3% reduces leaf temperature compared to an untreated control, aiding the continuity of photosynthesis. This results in greater accumulation of starch reserves in the shoots, improved nutrient absorption and translocation, and increased resistance to stress. It also indirectly reduces malformations of flower buds when the ambient temperature rises above 30°C.
Undoubtedly, proper irrigation control using management tools such as evaporation trays, probes, and/or weather stations allows us to perform the necessary calculations. However, this must be complemented by the use of soil pits, as these not only allow us to check or adjust irrigation times and frequencies but also enable us to observe root growth and soil health in the face of potential pests like weevils, commonly found post-harvest, allowing us to take the necessary corrective measures.
Along with irrigation, we cannot overlook nutrition. Throughout the season, post-harvest fertilization should be adjusted to replenish the nutrients lost during harvest, restoring them to known standards for the species. This is based on the yield obtained, January foliar and/or soil analyses, variety, rootstock, and vigor index.
When dealing with orchards in full production, and especially those with high yield potential, it is essential to support root recovery by incorporating rooting agents, commonly known as rooting hormones. These products contain auxins, which promote root development. Roots are responsible for accumulating a large portion of the carbon and nitrogen reserves that will provide initial nutritional support for the season, as there are no leaves to fuel the plant’s metabolism. This is because initial root development in spring is not observed before 25-30 days after planting (DDPF) (Fig. 1), generally occurring when the soil temperature exceeds 15°C, commonly observed around mid-October in central Chile.
Understanding the objective and its various mitigation strategies after the harvest, we cannot neglect to continue with a pest and disease management program. These issues must be addressed immediately after harvest through the use of acquired resistance inducers such as potassium phosphites, acaricides, and broad-spectrum fungicides, as well as sunscreens and algae-based products like Ascophyllum nodosum. This is crucial considering the stress the plant endured during harvest and the challenges it faces in the coming summer, which is characterized by increasingly higher temperatures and lower relative humidity each year, resulting in a greater accumulation of stress indices.
References:
– Bonomelli, C., Bonilla, C., Acuña, E., and Artacho, P. 2012. Seasonal pattern of root growth in relation to shoot phenology and soil temperature in sweet cherry trees (Prunus avium): A preliminary study in central Chile. Cien. Inv. Agr. 39(1).
– Quero-García, J., Iezzony, A., Pulawska, J., Lang, G. 2017. Cherries: botany, production and uses. Boston, MA: CABI, 2017.
– Salazar, C., Hernández, C., Pino, M. 2015. Plant water stress: Association between ethylene and abscisic acid response. Chilean J. Agric. Res. Vol. 75, Suppl. 1. August 2015. Chillán, Chile.
– Taiz, L. & Zeiger, E. 3rd Edition, 2006. Plant Physiology: Water Balance of Plants. Sinauer Associates. Sunderland, MA, USA.
– Tapia, C. 2017. Utilization, mode of action, and experiences of different growth regulators that influence cherry production. Revista Red Agrícola, August 2017 edition, pp. 30–31. Santiago, Chile.
– Villar, L., Lienqueo, I., Llanes., A., Rojas, P., Péez, J., Correa, F., Sagredo, B., Masciarelli, O., Luna, V., Almada, R. 2020. Comparative transcriptomic analysis reveals novel roles of transcription factors and hormones during the flowering induction and floral bud differentiation in sweet cherry tres (Prunus avium L. cv. Bing). PLoS One. 2020 Mar 12;15(3).
