Agriculture Reference
In-Depth Information
100
80
60
40
20
Nutrient concentration
in plant
FIGURE 3.26 Relationship between nutrient concentration in plant tissue and relative growth or yield.
(From Fageria, N. K., V. C. Baligar, and C. A. Jones. 2011a. Growth and Mineral Nutrition of Field Crops , 3rd
edition. Boca Raton, Florida: CRC Press. With permission.)
and yield are significantly reduced and foliar deficiency symptoms appear. In this range, application
of the nutrient results in a sharp increase in growth with very little change in nutrient concentration
in the plant. In the marginal range, the growth or yield is reduced but plants do not show deficiency
symptoms, and both nutrient concentrations and growth increase as more nutrients are absorbed.
Sometimes the marginal range is also called the transition zone (Ulrich and Hills, 1973). Within the
marginal or transition zone lies the critical level or concentration.
The third range or zone is the adequate zone, in which there is no increase in growth but the
nutrient concentration increases. This classification is also known as satisfactory, normal, or suffi-
cient concentration. The high classification range represents the range of concentrations between the
adequate and toxic ranges. Fertilizer use on crops with values in this range should be reduced until
the nutritional status of plants lies in the adequate range (Reuter and Robinson, 1986). The toxic
range is the range of nutrients in which there is a reduction in growth and yield but the concentration
of nutrients continues to increase. In this range, plants start showing toxicity symptoms. The critical
toxicity value lies in this range (Figure 3.26).
TABLE 3.3
Average Total N Concentration in Different Plant Parts
Plant Part Analyzed
N Concentration Range (g kg 1 )
Optimum N Concentration (g kg 1 )
Leaves (blades)
10-60
>30
Stems
10-40
>20
Roots
10-30
>10
Fruits
10-60
>30
Seeds
29-70
>20
Source: Adapted from Barker, A. V. and G. M. Bryson. 2007. Nitrogen. In: Handbook of Plant Nutrition , eds., A. V. Barker,
and D. J. Pilbeam, pp. 21-50. Boca Raton, Florida: CRC Press.
 
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