Critical
content
The critical nutrient concentration is a convenient reference point for assessing the nutrient status of a crop. The safe level is when the nutrient concentration is maintained appreciably above the critical deficiency concentration for optimum potato production. Care has to be exercised to maintain the nutrient level below the toxicity range. The toxicity limit of copper is observed to be 34 ppm in plant in acidic hill soil of Shimla region.
Critical
deficiency limits of micro-nutrients for determining nutrient status of soil and
potato
|
Micro-nutrient |
DTPA-extractable
micro-nutrients (ppm) in soil |
Critical
concentrations of micro-nutrients(ppm) in 4th leaves |
|||
|
Days
After Planting |
|||||
|
30 |
40 |
50 |
60 |
||
|
Zinc
(Total) |
0.75 |
27.5 |
25 |
18 |
16 |
|
Copper
(Total) |
0.32 |
8.5 |
8.5 |
6.0 |
4.5 |
|
Iron
(Ferrous form) |
6.6 |
- |
80 |
83 |
73 |
Plant analysis for total concentration of nutrients is generally recommended. However, in the case of Iron, ferrous form has been found more useful to detect iron deficiency.
Soil analysis has the major advantage over other diagnostic techniques as it evaluates the micro-nutrient supplying capacity of a soil prior to planting of potato crop. Several chemical extractants have been used for estimating the plant available micro-nutrient contents in different soils. The critical deficiency limits of DTPA, EDTA and ammonium acetate (pH 4.6) extractable zinc, below which economic response of potato to Zn application can be expected in acidic brown hill soils of Shimla region are 0.55, 1.70 and 1.50 ppm, respectively. The critical deficiency limits of DTPA-extractable Zn, Fe and Cu in alluvial soils of Jalandhar are 0.75, 6.6 and 0.32 ppm, respectively.
Status of micro-nutrients in potato growing areas