By Garth Donald, CCA, Western Canadian Manager of Agronomy, DynagraVRT
With this being a very trying year with a lot of challenges along the way, a large question emerges. What is left in my soil for nutrients? This is a very good question because some areas were very dry and produced below average yields. Others were very wet and produced an above average yield. But definitely the worst cases are the hailed fields. The reason the hailed fields are so tough to figure out is because the crops were at 70 to 75% moisture in the kernel or early dough stage. This means that a good portion of our fertilizer that was placed in the ground at seeding time was already used. Then we started to see some intense regrowth from the hailed crop which started to pull large amounts of nutrient again. So one of the best tools you can you to determine what is left in the soil is a soil test.
There are a few things you need to make sure when you are ordering your soil test. The first thing you need to make sure is that your agronomist is GPS referencing your soil points. With the lack of GPS referencing this is the biggest factor why in western Canada only 30% of our agricultural land gets soil tested and the growers feel this step is a waste of time. With GPS points you take away the large peaks and valleys that you will see on your tests and will see a consistency with your nutrients. Without referencing your points you are basically wasting your time and money doing any soil testing.
Second, do a complete analysis in your topsoil depths. You are trying to make a decision based on the information you have in front of you. The more information the better and easier your decision will become. There are a lot of relationships in your soil test results. For example, phosphate-calcium, potassium-magnesium and sodium-sulphur. With a basic N-P-K-S test it is like wearing a blindfold and having two pin holes to look out. Yes you may be able to see out but you can€™t see the whole picture of what is around you and things are not very clear. If your agronomist is only doing an N-P-K-S test then ask him why he doesn€™t want to give you a complete picture to look at.
The third thing would be to do at least a double depth test. A single depth test of a 0-12€ will give you your nitrogen and sulphur levels but will not give you a clear indication of your phosphorus, potassium and micro nutrients. At a minimum look at doing a 0-6€ complete analysis then a 6-12€ sub soil test for your nitrogen and sulphur. I find a 0-6€ complete and a 6-24€ sub soil give a very good window of what is happening in your field.
Lastly, your nutrient recommendation should be made by your agronomist. That is their job not the labs. The labs recommendation is a computer generated recommendation based on averages. Your agronomist should be able to make sound agronomic recommendations based on your yield goals and knowledge of the soil.
Don€™t be afraid to ask your agronomist questions about their soil testing protocol and if you don€™t like the answer you are given don€™t be afraid to look elsewhere for those answers. It is a big decision going into the next growing season so line yourself with people who can help you with those decisions.
Those are my thoughts,