As an example, Dart points out that a crop developing leaves needs the right nutrient in the right form as the leaves are expanding. That’s the time to be applying zinc (Zn), phosphate, and nitrogen (N), because they drive leaf size. At the same time, you should be applying the micronutrients (magnesium (Mg), manganese (Mn), iron (Fe), copper (Cu). These are building blocks for the chlorophyll that is developing as the leaves grow and expand. If you apply these nutrients after the leaves have fully formed, or if you apply them in a form that doesn’t go into the leaf until after it fully forms, you don’t get the full value of the application.
Timing and formulation matter, which is why they are on the Five R list. Dart encourages growers to ask tough, science-based questions of anyone making nutrition recommendations to ensure they get a program that addresses all of the Five Rs. Questions he recommends include:
- You’re recommending that I use this product — why? “Does this product have specifically and completely what I need at this stage of my crop?” asks Dart. “For example, growers need to pay particular attention to the micronutrients in their program because they drive the chlorophyll development, which is critical for photosynthesis, which in turn is critical for higher marketable yields and producing the sugars and flavor in melons and other fruit that leads to the customer coming back for more.”
- When does my crop really need this particular nutrient and why? “The plant’s need for a particular nutrient is not a flat line through the plant’s life,” notes Dart. “Some nutrients have early peak demand, some mid or late season based on how the nutrient is used in the plant and the specific quality parameters required for that crop. Growers want to make the applications in the front end of the demand curve, not the top or
the back end of the curve. That is when the nutrient is being used by the plant for maximum effectiveness and value.”
- Am I over-applying anything? “This question often doesn’t get asked, so many growers end up applying too much of a specific nutrient, most commonly nitrogen. The quality of the end product can be heavily impacted by applying too much of some nutrients,” says Dart, noting that this issue doesn’t get enough attention, especially with high-value crops like melons, cucumbers, tomatoes, peppers, potatoes, or leafy vegetables.“For example, too high of a nitrogen-to-calcium ratio can hurt a crop’s texture, color, sugar, flavor, shelf life, and shipping quality, so you don’t want to push too much nitrogen and underuse calcium.” This is especially true on mid/late season nitrogen applications.
- What is the best timing and formulation for making this application to ensure the plant will benefit from the nutrient? “This is a critical issue that can get easily overlooked, which results in wasted time and money,” says Dart. “Calcium (Ca) is a good example, because the fruiting parts of these vegetable crops can only take in Ca via foliar application during the cell division window of the fruit. At any other time, the Ca won’t go into the cell wall and be there for better texture, shipping quality, and shelf life. If you miss that window, it becomes a mis-timed application that won’t deliver the desired results and will waste money and packable yield.”“If you want to be a hero to the produce buyer and produce manager, do a better job on calcium and the Five Rs and you will reduce shrinkage — the second biggest expense in the produce department after labor costs.”
- Why is the formulation that you’re recommending the right formulation to get this nutrient into the plant? “Delivering a nutrient the plant can use is all about the product’s formulation, and it is often overlooked in a nutrition program,” says Dart. “But the formulation matters because a foliar nutrient is only effective and has value if it gets into the plant completely and at the right time.”
- Manufacturers are continually improving the fertilizers and nutrient products they bring to the market. Growers who understand the Five Rs and Science-Based Nutrition will be positioned to make the best choices for the best results, less waste, and increased economic returns.
Source: Growing Produce. August 2019