Dilution procedure: Determining initial substrate pH

Prior to transplant, growers can determine initial substrate pH by utilizing the 1:2 dilution method. This monitoring procedure determines: 1) the limestone reactivity thereby adjusting substrate pH; 2) if the substrate pH is too low or high; 3) if corrective procedures are required prior to transplant and; 4) establishes the baseline pH of the substrate.

by W. Garrett Owen - wgowen@msu.edu, Andrew Moore, Brian E. Whipker - bwhipker@ncsu.edu and  Josh Henry

Over the past two years, substrates with low pH have plagued many greenhouse growers. Low pH-induced iron (Fe) and/or manganese (Mn) toxicity symptoms often occurred weeks into bedding plant production season where action was required to adjust (increase) substrate pH to the optimal pH range of 5.8 to 6.2. In these instances, plants were ‘saved’ by utilizing one of three corrective procedures outlined in e-GRO Alert 7.2 . However, in other instances, corrective procedures could not ‘save’ plants because the plant aesthetics and quality were comprised, thus plants were discarded.

Utilizing in-house nutritional monitoring procedures, specifically, the 1:2 dilution method will assist growers in determining:

  1. If the limestone has reacted to adjust substrate pH;
  2. If the substrate pH is too low or high;
  3. If correction procedures are required prior to transplant and;
  4. To establish the baseline pH of the substrate.

Each of the aforementioned steps plays an important role in nutritional monitoring throughout the season.

Read the full e-GRO Alert here.


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