ISHS Acta Horticulturae 238: Symposium on Substrates in Horticulture other than Soils in situ
DEVELOPMENT OF A RAPID NUTRIENT TEST KIT FOR HORTICULTURAL SUBSTRATES |
| Authors: | M. Prasad, T.M. Spiers |
| Abstract:
The 1:1.5 water extract laboratory method for horticultural substrates developed by Sonneveld et al. in Holland for horticultural substrates was adapted as a rapid nutrient test kit for grower use. Horticultural substrates used for this investigation included peat, pumice, bark and sawdust in various combinations and containing 5 levels of NH4-N, NO3-N, P and K for each substrate. These substrates were extracted either for 15 minutes using an orbital shaker or for 2 minutes by vigorous shaking by hand, and the extracts analysed for N, P and K using standard autoanalyzer (AA) methods. There was a high correlation between the machine and the hand extraction with the amounts extracted being similar. The NO3-N value determined in the extract using Merck nitrate strips was well correlated with the AA method although it tended to underestimate the value. NH4-N, P and K by visual methods gave satisfactory results in relation to AA methods. Test carried out by 5 independent operators using a commercial test kit based on this research gave very satisfactory results on 3 samples bearing in mind that for horticultural substrates frequent analysis is the norm; therefore the degree of accuracy required is less than for conventional test of field soils. This test kit can be easily adapted for rock wool and for hydroponics culture. | |
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