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Simple Plant Deficiency Tests
The minus one pot trial
One of the simplest and most reliable methods of discovering all the nutrients which are deficient in a soil is through small pot trials. In nutrient omission pot trials, one pot receives an adequate supply of all the mineral nutrients (the control, or “All” treatment). Other pots get all the mineral nutrients minus one. Plants are grown for a short period (usually 4-6 weeks), and the dry weight of tops is compared with that of the “All” treatment. Any nutrient whose absence results in a significant decrease in weight is regarded as deficient. Usually an indicator plant such as maize is used, as maize offers rapid establishment, and its responses to nutrient deficiencies are well characterized.
Note: Nutrient levels which are deficient for one species may be adequate for another.
Leaf painting
Another useful technique for confirming deficiencies of micronutrients is leaf painting. By carefully painting half of an affected leaf with a dilute solution of the suspected nutrient, the response can be seen by comparing the colour or expansion of the painted half with the unpainted half. Leaf painting has been used successfully to diagnose micronutrient deficiencies of Fe, Mn and Zn in sweetpotato.
Source: O’Sullivan, J.N., Asher, C.J. and Blamey, F.P.C. (1997) Nutrient Disorders of Sweet Potato. ACIAR Monograph No. 48, Australian Centre for International Agricultural Research, Canberra, 136 p.
One of the simplest and most reliable methods of discovering all the nutrients which are deficient in a soil is through small pot trials. In nutrient omission pot trials, one pot receives an adequate supply of all the mineral nutrients (the control, or “All” treatment). Other pots get all the mineral nutrients minus one. Plants are grown for a short period (usually 4-6 weeks), and the dry weight of tops is compared with that of the “All” treatment. Any nutrient whose absence results in a significant decrease in weight is regarded as deficient. Usually an indicator plant such as maize is used, as maize offers rapid establishment, and its responses to nutrient deficiencies are well characterized.
Note: Nutrient levels which are deficient for one species may be adequate for another.
Leaf painting
Another useful technique for confirming deficiencies of micronutrients is leaf painting. By carefully painting half of an affected leaf with a dilute solution of the suspected nutrient, the response can be seen by comparing the colour or expansion of the painted half with the unpainted half. Leaf painting has been used successfully to diagnose micronutrient deficiencies of Fe, Mn and Zn in sweetpotato.
Source: O’Sullivan, J.N., Asher, C.J. and Blamey, F.P.C. (1997) Nutrient Disorders of Sweet Potato. ACIAR Monograph No. 48, Australian Centre for International Agricultural Research, Canberra, 136 p.