If you are using Saturated Paste Extract ( SPE ) to assess dirt food for in - ground grown cut flowers , you may be underestimating works - available nutrient and apply fertilizers that are n’t needed .
by Chevonne Dayboll , Greenhouse Floriculture Specialist , OMAFRA , Lauren Vanderlingen , OMAFRA Summer Student and Christoph Kessel , OMAFRA Soil Fertility Specialist – Horticulture
Many greenhouse agriculturist use SPE analysis when testing originate media in the greenhouse for nutrient levels . Typically , SPE test are used in soilless or peat - based rise substrates , the kind we commonly see used in potted industrial plant yield . However , if you are growing rationalise flowers in a mineral dirt , either in the greenhouse or outdoors , SPE is not giving you a complete reputation on nutrients available to your craw .
Both nursery and outdoor soil that make cut flowers should be prove on a regular fundament .
The reason is that SPE method use water to distill food and only tells us about nutrients that are water - soluble . It does not report on plant - usable nutrient that are held on organic and inorganic substitution sites . Because SPE employ only water as the extractant , it can underestimate plant - available nutrients . This in turning increases the potential for growers to use fertilizers that are n’t needfully needed .
A adept alternative for in - ground systems is a mineral soil analysis . This test use a chemical extractant to assess plant - usable nutrients . Unlike SPE , it extracts both pee - soluble nutrient and those that are hold on organic and inorganic exchange situation .
In short :
If you are farm in - flat coat greenhouse cut flowers and are using SPE to analyze your soil , compare the results for the two different method yourself .
Take a minimum of 20 grime cores from across a menage or mountain range of plant from the same stage .
The next time you take a territory sample , collect enough soil to submit a second sample as well . bow one for SPE analysis and submit another for a mineral grunge analysis .
If the reported mineral soil analysis value are greater than 30 ppm nitrate - atomic number 7 ( N ) , 60 ppm phosphorus ( P ) , 120 ppm potassium ( K ) or 100 ppm magnesium ( Mg ) consider a trial on a small scale where you reduce fertiliser applications and liken it to your current practice session .
ground sampling tipsTaking soil sample after every harvest oscillation or on a even agenda can bring home the bacon utilitarian information about the composition of your soil and the nutrients it comprise .
To get an thought of the nutrients useable to your plants , adopt these tips for getting the best soil sample :
A list of OMAFRA accredited ground testing laboratory can be establish at : http://www.omafra.gov.on.ca / english / crops / resource / soillabs.htm
informant : onfloriculture
