The Relationship Between Nutrient Levels in Soil and Weed Growth

Much has been said and little studied on the relationship between nutrient levels in soil and weed growth/suppression.

A long time organic grower and agronomist (and friend) shared his experiences with calcium levels and the reduction of weed growth after planting.

  • One thing that is necessary is good functioning, highly biological soil.
  • The second necessity is highly available calcium.

2017 barley high calcium weed suppresion trial skip

The barley in these photos shows the crop 30 days after planting.

The barley was planted with equipment outfitted to apply a liquid biological (Purple Cow CX-1) right in furrow on the 24 run drill (see picture of planter: the CX-1 goes down on each row/run planted right in the double disc openers) at a rate of 5 gallons per acre.  The day after planting a highly soluble calcium product was spread at 500lbs per acre over the field and left on the open surface.

24 run drill

Purple Cow FortiCal could be an option pre-planting, but in this instance, to be more “tender footed” in application, a finer/drier product that would go through a fertilizer cart was used (vs needing a spreader truck or larger heaver equipment) because it was applied on the planted (not yet emerged) crop.

~James (Sandy) Syburg, Soilologist

As you can see even the area in the field that was skipped by the drill (where the bare soil is exposed), there is almost no weed pressure even 30 days after planting!


60 Days after planting

2017 barley high calcium weed suppresion trial skip60DAYS

The barley looks pretty good for how wet it has been. Probably still a few weeks until harvest but weed pressure is almost nonexistent. I took a picture of skip and still very little weeds even with all the rain. My guess is very little of the soluble calcium is still around but I say it did its job.

~James (Sandy) Syburg, Soilologist

Why does soil biology matter?

The take away is to insure you have biologically active soils by using a liquid biological at planting – at the genesis of plant growth and germination.  Also, balance soil minerals to make sure to have nutrients available to both soil microbiology and the plant.

Mineral form application

Nutrients in an organic form that require liberation via the soil microbial community – meaning in mineral form – are best.  But in planting situations when soils biological activity is low the soluble calcium is what is believed to suppress the weed seed germination.  In this instance I would have to say it worked.  Not all the calcium in the product that was applied is soluble, so the biology is now taking over the job of releasing it due to the soils being warmer and activity returning.

~James (Sandy) Syburg, Soilologist

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