All fruit trees experience a load adjustment after flowering, but avocados continue to experience fruit abortions even a few months before harvest. The first summer fruit drop is considered normal and even necessary for fruit size development and subsequent new growth, but the subsequent fruit drop experienced by this fruit tree is completely abnormal and easily preventable. In Chile, the classic phrase "Look up, not down" is often used in autumn, normalizing autumn fruit drop and suggesting there's little that can be done. However, several management practices have successfully reduced autumn fruit drop, even eliminating it entirely. These orchards experience a summer fruit drop, where the plant gains time to determine which embryos are worthy of reaching harvest and which are best discarded quickly, starting in December and ending in late February with the last fruits falling to the ground. By March, the plant has already completed fruit set and, unlike other orchards, does not experience a second late fruit drop. The treatments that reduce or completely eliminate this second autumn fruit drop are described here.

- Foliage Management: All orchards that prune correctly once the harvest is finished subsequently have less abortion than orchards that do not prune or worse, that carry out extreme fruit storage.

- Biological Fertilization: The use of salts increases the electrical conductivity (EC) in the soil, affecting the root system. Given the avocado's high sensitivity to salinity, working with biofertilizers eliminates saline stress in the irrigation zone, rapidly reducing fruit abortion. It's worth noting that all valleys with salinity experience a significant second abortion in the fall, considerably lowering the crop's yield potential. Increasing soil carbon, developing mulch, and then inoculating the soil profile with microbial consortia are essential to mitigate the effects of salinity in cultivated soil. The microbiota feeds on the salts that bother the avocado, lowering the EC in the irrigation zone.

- Nitrogen: Our agriculture is heavily reliant on nitrogen, focusing on foliage production rather than fruit. By balancing nitrogen within the fertilization program, vegetative growth develops more evenly, exhibiting shoots with lateral branching and avoiding the proliferation of suckers that compete with fruit development. The vast majority of the industry prioritizes nutrients in the following order: NKP-Micronutrients-Ca-C, while the best results are obtained with K-Ca-PC-Micronutrients-N. By postponing nitrogen application until the end and repositioning K, Ca, and P as fundamental nutrients, plants concentrate on fruit production and then, over time, address foliage deficiencies. This new fertilization approach strengthens embryos from the outset and reduces competition during embryo formation.

- Floral Nutrition: From the cauliflower stage until fruit set, sprays with Ca + B + Zn + Gibberellic Acid + 6-BA + Biostimulants promote greater panicle growth, which ultimately thickens the future fruit peduncle, preventing abscission ring formation, reducing fruit drop, and increasing the set of double and triple fruits. This remarkable effect has necessitated two to three floral nutrition applications, even on steep hillsides, using less effective aerial applications and ground applications with a spray nozzle or cannon that achieve greater coverage.

- Pollinators: Orchards with two pollinating varieties, especially Negra de La Cruz, show higher initial fruit set, less fruit drop in autumn, and higher final fruit set, resulting in greater yield potential. The formation of an embryo with stress-tolerant genetics is crucial for reducing fruit abscission during the summer and autumn.

- Stress Physiology: By reducing stress during the summer, the plant produces fewer aging hormones such as ethylene and abscisic acid, resulting in only the weakest fruits being lost to abortion. Applications of seaweed extract and biostimulants via irrigation from fruit set until late autumn help reduce summer stress, stimulating prolonged root growth that ultimately strengthens the plants. In the last two seasons, we have evaluated two products of Mexican origin that are delivering remarkable results in fruit development. The first is AV5G, which reduces autumn fruit abortion, and the second is LPG456, which, in addition to reducing abortion, also improves post-harvest quality, minimizing losses that can occur in the marketing of exported fruit. Agroenzymas, the company behind this, developed these mixtures containing formulations of different biostimulants that, when applied foliarly or via irrigation, increase stress tolerance, balancing plant growth by directing more energy towards fruit development and preventing fruit drop. By achieving a balance in bud break, it is possible to reduce or even suspend the application of Uniconazole foliar or via irrigation, avoiding residue problems or affecting the growth of weaker plants.

Gonzalo Vargas

gvargascarranza@gmail.com