Ag 101 Week 10

Fertilizers Feed

And 3 out of the 4 R's: The expanded version


It's week 10 of the Ag 101 52 Weeks of Agronomy Series. I'm not sure why it feels like a milestone it just does. So, let me know what you think or if there are topics you want to discuss. I have the 52 weeks planned. But after being married 21 years, raising two kids, dogs, cats, and horses, I'm comfortable with changing my schedule. Unless there is a chance I might miss a meal, then we'll have to talk.

Let's talk fertilizer. It is coming up to that time of year if growers haven't done so already, they are looking at their soil tests and trying to figure out where what, and when. First, lets review the definition-

Fertilizers are intended to feed the soil biology and individual plants.  The right source, rate, time, and placement are critical to ensuring optimal plant use, nutrition, and yields.

Fertilizers and amendments differ in their purpose and their application in your system. However, many can be used to change the physical and chemical properties of the soil and act as a fertilizer feeding your system as well. Having a soil test, knowing the soil type, and understanding the needs of your crops helps to determine what are the best options. 

The definition is straightforward, they feed the soil biology or plant but why go over 3 out of the 4 Rs again. These practices are where farmers have an opportunity to save money, be good stewards of the environment, and grow a higher yielding more nutrient dense crop.

So, here are the three we're going to talk about again-

Right rate -

Rates are based on soil test results, tissue test results, and plant demand. 

A lot of times you'll see this on a soil test depending on the lab and if you have requested a recommendation from the lab that accompanies your soil test results. Be aware at one point in time some labs included this with your soil test results. I am finding as I work with more growers across the country this might not be the case and you will be billed extra for them. Or be charged per crop listed. Read the forms that are specific to the lab you are working with to see if that is the case and fill them out accordingly. 

If in question about application rates or crop nutrient removal rates, several resources can at least get you started. One of them is an agronomy guide published by your states land-grant university. In Pennsylvania, we are fortunate enough to have one that publishes a conventional and organic version. Here is a link to both.

For convention systems

For organic system

This is one of the most critical factors for a grower to consider to maximize not only your environmental impact but also a financial one as well. Using more fertilizer than what is required by the crop or soil conditions can lead to potentially increases levels of nutrients that are left to leave your farm by other means such as runoff or luxury consumption by the crop. Using too little of a required nutrient can be the cause of a lower than desired yield or poor crop quality.

I have seen soil tests that recommend you ask your local fertilizer dealer. I'm not sure if that's the fox watching the hen house or not, however, I do know some reputable sales agronomists make honest recommendations. I also know they can be hard to find.  I can be quoted as having said I made a lousy salesperson because I think like an agronomist. You always have the option of going by the labeled rate on the product too.

I'm often asked where to go to get sound advice. If it were my farm, I would seek out vetted recommendations based on science that can be applied practically to your system whether it be your fertilizer dealer, extension agent, or an agronomist. If the person is not willing to invest in getting to know and understand what will work for you it doesn't matter how good the advice is, you're not going to be able or willing to apply it anyway. 

Right time -

Timing is determined by plant demands a certain stage of growth, soil supply, nutrient loss risks, and management strategies.

We have all heard the saying "Timing is everything." It's true for fertilizer as well. If applied at the wrong time it will not only be a waste of money but a waste of time in labor costs. I was brought up hearing money is time and time is money. I have once again ticked Grammarly off for wordiness, but I hope you get my point.

You can see the most significant impact on yield loss due to the plant not being able to uptake the fertilizer at the appropriate stage of growth it needs it. 

Let's go back to what we talked about regarding the physical and chemical properties of soil. If you recall we said that...

The cation exchange capacity measures the capacity of the soil to hold and store positively-charged elements, such as calcium, magnesium, and potassium. Soils with a higher CEC requires fewer fertilizer applications, resulting in using a potentially higher rate with only one application.  In soils with a lower CEC, splitting the fertilizer application into multiple ones could be necessary to avoid loss of nutrients due to leaching before the plant has adequate time to take it up. 

The soil texture is related to CEC. Sandy soils usually have a low CEC, while clay soils have a higher CEC. But while CEC indicates the capacity of the soil to hold nutrients, soil texture refers to the ratio of the soil separates -sand, silt, and clay- of the soil. Sandy soils contain less water than soils with a higher amount of clay and silt. Irrigation frequency is usually higher in sandy soils and results in more leaching of nutrients. Therefore, splitting fertilizer application in sandier soils helps to mitigate higher nutrient loss. 

It all comes back to timing when your going to apply fertilizers according to your soil and system to get the most efficient use of it.

Right placement -

Consider root-soil dynamics, nutrient movement, and nutrient loss potential. 

Above is what I have on the slide in my presentation and it pretty much sums everything up. Location, location, location comes to mind as well. Not placing fertilizer where the plant can utilize it is one way how growers far too often get everything else right only to miss the mark on one thing. But not going all the way by proper placement can be one of the deciding factors in whether your crop is successful that season.  

A general rule of thumb for application is-

        Amendments are broadcast, meaning spread over a large area. They are used to achieve an overall                                                                                                                         goal.             

       Fertilizers are applied strategically, where they are accessible to the roots of the plant without                                                                                                                          causing damage. 

When I give recommendations I use terminology like- in row at the time of planting, or in the whole at the time of planting. I'm also clear with the grower that it should be worked in first, meaning mixed with soil then the plant or seed placed. Is it always easy and can it be more time-consuming?   Yes, but leaving money in the field isn't a good thing either.

With so many other variables out of a growers control, investing a few extra minutes to consider rate, timing, and placement will take you from being good at farming to being successful and profitablable at it as well.