The Influence of Nutrient Applications on Post Harvest

One of the biggest factors that makes us proud is our wide network of crop advisors. This week, we had the privilege of interviewing Niels Van de Heeren, a highly experienced tropical crop advisor in Latin America. Niels shared his fascinating insights on the interaction between Boron (B) and Calcium (Ca) and how this interaction affects post-harvest quality. Primarily working with mangos, avocados and coffee crops, Niels dove into his intriguing experiences with these crops in different Latin American countries. 

Influence of Calcium in post harvest applications

Mangos

We first dove into the Dominican Republic and Niels’ experience there. He was called in due to significant post-harvest quality issues. Upon arrival, he discovered a problem with Calcium inputs on the farm. A very coarse source of lime was used, leading to inadequate Calcium uptake in the mangoes due to the texture of the material. Niels and the team addressed this by providing a liquid Calcium source and stimulating the trees' roots with different biostimulants, such as amino acids and algae based compounds. This was done with the purpose of accelerating and increasing Calcium uptake by the plants. Boron and Silicon were also included in the fertilisation strategy, with the purpose of serving as Calcium transporter. The results were remarkable, as the mangoes' dry matter (starch with the potential of becoming sugar, which influences flavour and post harvest applications) content significantly exceeded standards.

Calcium is a major enhancer of mango dry matter due to the fact that it enhances cell wall structure, while promoting the creation of new cells. In mango production, dry matter content is crucial for post-harvest quality. Weak cell walls (low dry matter content) can lead to a problem called "Internal Browning," where cells break down and release melanin, triggering a chain reaction of cell damage. This issue is invisible from the outside and renders the mango inedible. High dry matter content indicates stronger cell walls, reducing the likelihood of cell damage. Calcium also significantly improves mangoes' resilience to sunburn, reducing the incidence of spots and other damage due to the improved strength of cell walls.

Avocados

Another example that Neils had of calcium's impact on post-harvest quality came from avocados. For instance, applying a readily available and fast absorption Calcium fertiliser form can reduce internal black veining in avocados by 80-90%. In avocados internal browning is one of the most popular post harvest issues, when avocados experience this damage, flavour and appearance of the fruit reduces. This issue is caused by bacterial and fungus infestations. Avocados with low calcium contents tend to have weaker cell walls, making them more susceptible to these pathogens.

Coffee Beans

For coffee production, Niels’ experience once again had proven the importance of managing calcium inputs for higher nutrient availability, and higher plant uptake. He observed a significant influence on bean size, translating into better profits for farmers due to production of more tons per hectare, and improved roasting possibilities due to an improvement of flavour. Niels has noted that even low-altitude coffee crops can be triggered to increase quality, potentially rivalling high-altitude coffee. 

The importance of measuring quality indicators

In light of his experiences, Niels has noticed some misconceptions about quality prediction indicators. He clarified what, in his opinion, is the correct approach, and how Calcium influences the results altogether. 

Total Calcium was measured in mangoes as a predictor of quality, assuming that higher total Calcium content led to better fruit quality. However, after experiencing the aforementioned scenario, Niels realized that this was a misconception. Why? The crucial Calcium measurement for growers is the amount that is assimilated into the dry matter. Total Calcium content is misleading because it includes sap Calcium, which may not necessarily be fixed or incorporated into the fruit's structure.

Another quality prediction indicator is fruit brix levels. Niels explained that proper Calcium fertilization tends to increase these levels, but also how the measurement procedure should vary across different crops. For coffee, producers typically wait for their berries to ripen before harvesting, allowing them to target high brix content during the harvest (ripe fruits have higher sugar contents than non-ripe). Some people follow the same practice for mangoes, but the difference is that these fruits are usually not harvested ripe (especially for export). Therefore, Niels explained that focusing on the dry matter content of a mango can influence brix content when the fruit ripens in the supermarket. This is because starch converts to fructose during the ripening process, resulting in higher brix levels and a better taste.

To our pleasure, Niels is extremely enthusiastic about SoilBeat, considering it a valuable tool for agronomists in order to keep track of these interactions thoroughly. He believes that it allows experts to input their practical experiences and measurements for analysis, uncovering subtle interactions and patterns that can significantly impact growers' profits and contribute to smart farming practices. We highly appreciate him for that!