Each year when I make up this very general map, I keep hoping for a young generation to come along with better technology and smarts to make a better map. I now see a very bright light at the end of the tunnel. My December 12, 2018, article talked about the soil moisture sensor probes that are now being used by some.
When we started making this map eons ago, the idea never was that it was accurate for individual farm fields. The idea was to provide a framework so farmers could use rules of thumb to get a good handle on the situation at their farm.
With the rapid advance of private sector agronomists, it is logical that a farm map of soil moisture reserves should be part of the information package. I now see where that is happening and hope it expands fast.
Thanks for helpers
Thanks to Kim Stonehouse and Cory Jacob of Saskatchewan Agriculture. They provided me with soil moisture probing they did in the Watrous and Tisdale areas. Bonnie Mandziak of South Country Equipment kindly supplied a map they prepared for southeast Saskatchewan based on capacitance soil moisture probes.
Growing crops on paper
Readers that have Henry’s Handbook of Soils and Water will be familiar with the yield tables on pages 115-118. The wheat and canola tables here are based on the equations found in the book.
The tables show yields all the way from three to 83 bu./acre. When we first prepared the tables the yields with high soil water and rain seemed to be too high. But, yields obtained at farm levels in the past several years have reached those yields and beyond.
The “zero inches” soil water would be in the red on the map. If your soil has little or no subsoil moisture then it is clear you need timely and generous rains to reach a profitable yield. The “six inches” soil water would be a medium texture soil full of water.
Yields of recent years have often exceeded what would be expected based on soil water and rain. We now know that in many of those situations the real factor was sub-irrigation courtesy of a high water table.
Current farming methods are also responsible for better yields. Current zero-till seeders can provide a crop stand with little rain if surface moisture is OK. Old seeding techniques required timely rains just to get the crop out of the ground. Fertilizer rates have also increased to make use of the extra water Mother Nature provided.
But do not get the idea that we can grow crops without water. No water in soil means that above average rain is needed in a timely manner.
Word of caution
Please be aware that this map is very general. Individual rain events in local areas can put you in a different situation. A small area north of Rosetown, Sask., and another northeast of Swift Current, Sask., had extra rain but the areas were too small to map. The only way to be sure is to have data for your own farm fields. Finally, it looks like that will soon be happening.