Articles
ANALYTICAL METHODS FOR PEAT SUBSTRATES
Reproducibility of the analytical results is of prime importance.
The Merkle laboratory, for routine K, Mg, Ca extractions of mineral soils, uses 2.5 g soil and for phosphorus 3.5 g soil to 25 ml extracting solution.
For soilless media this ratio was changed to 50 ml of moist substrate and enough extracting solution to make a total volume of 250 ml.
Results of the moist volume extraction method lacked reproducibility.
Recent experiments have shown that a volume measurement of oven-dry seived media greatly improved reproducibility but required the addition of a surfactant to aid thorough rewetting of media containing oven-dried peat or humus.
A weight measurement of oven-dry seived media produced acceptable results but required adjustments for the weight of dry matter per liter of water held at container capacity for each medium.
Standard guideline interpretation values are presented for green-house tomatoes and container-grown flower crops.
These interpretations include values for Ca, Mg, K balance as well as available Ca, Mg, K, P, NO3-N, and conductivity of total soluble salts.