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With the price of fertilizer skyrocketing and climate change affecting growers around the world in a variety of ways, a true understanding of crop nutrition and the 4Rs is essential. In a recent webinar., “Keeping Agriculture Sustainable from a Global Perspective,” Doug Snyder, National Marketing Agronomist for SQM Specialty Plant Nutrition, discussed why efficiencies in crop nutrition, even if not mandated by regulatory groups, are still mandatory. “We obviously need to improve our plant nutrition efficiency by using different types of chemistries and different methods of applying those chemistries,” Snyder says. Of course, the 4Rs of nutrient stewardship are the right source, the right rate, the right time, and the right place. As we have learned more about soil types, soil fertility and how and when specific crops need nutrients, our ability to be efficient and sustainable has improved.”

Avoid New Problems by Using the Right Source

Snyder says the right source, or the right type of fertilizer is important for more reasons than giving the plant what it needs. For example, many soils, particularly in California, already have high salinity. Drought exacerbates the problem, since the salts are not leached from the soil as frequently. Ground water also has high salinity in these areas and is being used more frequently for irrigation, since surface water is in short supply. So, the last thing a grower would want to do is add a fertilizer source that will increase the salinity of the soil. To illustrate the point, Snyder says four common sources of potassium are potassium sulphate, potassium nitrate, potassium thiosulfate and potassium chloride. All contain potassium, but some of those sources can make soil salinity worse. “Chlorides and excess sulfur can increase soil salinity,” Snyder says. “Sulfur can also tie up calcium in the soil, because it binds to the calcium ion and becomes calcium sulfate, making it relatively immobile in the soil and unavailable to the plant. So, it’s important to know the salt content of your soil measured by the electrical conductivity method and make sure you’re using the right source of potassium that doesn’t increase salinity.”

Know the Right Rate and Timing

The right rate is important, too, for cost reasons – because why spend money on inputs that will be unused – and for environmental issues. Fertilizer runoff can cause multiple environmental problems – especially in waterways. Closely tied to the right rate is the right timing. If nutrients are applied at a time the crop isn’t ready to absorb and use them, it’s a waste of money and time, and those excess nutrients are either going to bind up other elements in the soil or run off. Knowing the crop and its specific requirements and when it needs them is key to efficiency, Snyder says. In some cases, split applications are the answer. University studies on crops ranging from almonds to potatoes have shown greater efficiency and higher yield when applications are divided and applied just when the crop needs it. “One study at Colorado State University by Dr. Samuel Essah compared a number of potassium protocols in potato production,” Snyder says. “What they found was when the grower standard protocol of sulfate of potash pre-plant was sidedressed with split applications of potassium nitrate, yield increased by 28 to 34 pounds per acre depending on the formulation used. It produced not only greater yield, but also better efficiency of pounds per acre of potassium.” The right place – while it might seem obvious – is the final piece of the nutrient efficiency puzzle. Fertilizers need to be placed within the root zone at a time when roots are ready to absorb them. Nutrients applied when soil temperatures are cold and new seedlings are struggling to develop roots will be wasted, for example. “The point to take away from this is nutrient efficiencies are mandatory, and I don’t mean in the regulatory sense,” Snyder says. “They are mandatory on the economic level for the farmer, and on the global level to ensure that food, fuel, and fiber production can be conducted in a sustainable way.”