What happened to the 4Rs?

Right rate
Right time
Right place
Right source

Seems logical and easy, right?

Fertilizer applications may be made with intentions of following the 4Rs in mind, but interpretation of these guidelines is critical. The 4 Rs are meant to serve as a framework for management practices that help keep nutrients on and in the crop. Growers may believe they are following the 4Rs with their nutrient applications, but do not realize the complexity involved in precision applications. There can also be various reasons why the 4Rs are not embraced. Those can include lack of fertigation system, or a system that can’t handle precision applications. Maybe nutrition programs are just being done the way they always have and it’s worked – sort of.

Goal of the 4 Rs framework is to match nutrient supply with crop requirements over the growing season and also to minimize nutrient loss from leaching. There can be site specific factors influencing how the 4Rs are implemented. These can include soil types, season and climate.

Now is the right time to put some serious thought into your nutrition program and understand not only how to take the right approach to fertilization, but to integrate the science of plant uptake and precision application. This move can improve yields and crop quality- along with saving fertilizer costs. Less product is leached below the root zone, volatilized or wasted due to faulty timing or placement. Both soil and plant health are improved when making precision fertilizer applications following the 4Rs. The cost of a precision application system can be repaid with increased fertilizer efficiency and better production.

The 4 Rs, promoted by the American Society of Agronomy (CCA)to reduce waste of nutrients and ensure plant health, can be misunderstood. The concept of fertilization management has never been more important, but lacking the technology for precise application, the 4 Rs can be misinterpreted.

“The 4 Rs have not evolved where the industry needs them to be,” Deborah Miller, President of Deerpoint Group states.

Growers can’t claim regenerative practices when they apply too much of a nutrient that the plant can’t use.”

How does following the 4Rs in crop nutrition match the definition of the current agriculture buzz word “Regenerative.” There are many definitions of ‘regenerative’ found on Google, but while most are aimed at marketing, it is simply said to be a farming method that improves soil and soil biodiversity while creating an environment that helps plants thrive. Productivity and profitability are also goals in regenerative farming. However, the word is also being used to attack fertilizer companies, implying that their products are not conducive to regenerative agriculture. Reducing fertilizer inputs by precision feed and matching crop demand, while improving soil health, is the best regenerative practice.

Growers may think that they are following the 4Rs and still apply 40 units of nitrogen in two irrigations in the spring- that is the ‘right’ rate to them, but it can be wasteful. Applying more fertilizer than the plant needs or can take up is more expensive over time than the precision approach to fertilization. Applying 40 units of N in the spring over one or two irrigation sets is common in almond production, but does not fit the industry’s best management practices for fertilization. Use of synthetic fertilizers and their effect on soil health has also been questioned, but the reality is that to be sustainable, it is important to use the right product and use it efficiently and economically.

The 4Rs are basically best management practices that can also evolve over time to improve understanding of crop needs. Those can look different depending on crop, soils and climate.

The 4 Rs do not specify sources, rates or times, leaving that to the grower or crop consultant.

The Right Source- This might be the most complex part. Choosing the right nutrient source means considering plant nutrition requirements, soil conditions, nutrient delivery method and environmental issues. There are also economic considerations that need to be addressed. The first step in determining the right source would be a soil diagnostic test to determine plant specific requirements for crop yield and productivity. Those tests can show which fertilizer type and nutrient source are best. Liquid sources are recommended if micronutrient incorporation is desired. The right source can also minimize environmental losses of a nutrient, depending on rate, place and time of application.

The Right Rate- this is site specific. Soil type, climate, labor supply, logistics and yield potential are all considerations in determining the right fertilizer rate. The goal here is to match the specific crops’s nutrient needs with the nutrients supplied – and not always all at once. Soil and tissue testing will help determine the rate of application and also allow the nutrient plan to be adjusted during the growing season.

The Right Place- Nutrients applied where the roots cannot take them up are wasted. They need to be in the zone that is most accessible. Again the source properties, stage of growth and orchard or field management are considerations. University of California research shows that highly concentrated zones of nutrients near the crop’s root system will supply nutrients more quickly and for a longer period of time. Recognize that there is a limit to the absorption rate by the root system. Over application of fertlilizer will not achieve faster nutrient uptake. Crop type and stage of production determine uptake- leading to the final R: The Right Time.

The Right Time- This takes planning as timing can be an effective route to minimize losses and advance uptake. Soil structure and its ability to retain nutrients, crop needs and environmental conditions all play a part in correct timing of fertilizer applications. Careful timing of applications to hit the crop uptake patterns will increase efficiency.

A key part of the timing, source and rate planning involves analysis of water, soil and plants. In the Deerpoint Group’s state of the art laboratory, soil and plant samples are regularly analyzed to determine nutrient status to deliver the precise amount needed by the crop. John Miller, CEO of Deerpoint Group noted that quick turn around time for sample analysis means that changes in nutrient delivery can be made quickly.