Agriculture Reference
In-Depth Information
Average of two soil depths
3000
2000
Y = 1244.76 + 79.55X - 0.8241X 2
1000
R 2 = 0.7641**
0
10-20 cm
3000
10.20 cm
2000
Y = 1273.29 + 86.82X - 0.9915X 2
1000
R 2 = 0.7251**
0
0-10 cm
3000
2000
Y = 1244.79 + 72.29X - 0.6781X 2
1000
R 2 = 0.7888**
0
20
40
60
80
Calcium saturation (%)
FIGURE 8.4 Relationship between calcium saturation and grain yield of dry bean. (From Fageria, N. K.
2008. Commun. Soil Sci. Plant Anal. 39:845-857. With permission.)
be exceptions, such as upland rice, which is very tolerant of soil acidity and can produce good yield
at a base saturation lower than 50%. Specific optimal base saturation values for important annual
crops grown on Brazilian Oxisols are given in Table 8.4. The quantity of lime required depends on
the quality of liming material, crop species, soil pH, concentrations of Ca, Mg, and Al in the soil,
soil type, and economic considerations.
8.2.2.2 Adequate Soil Fertility
Soil fertility refers to the ability of a soil to supply the nutrient elements in the amounts, forms, and
proportions required for maximum plant growth. It is measured in terms of the amount of the avail-
able forms of the nutrient elements in the soil at any given time. The fundamental components of
soil fertility are the essential plant nutrients. There are 17 essential plant nutrients for plant growth.
The essential nutrients from the soil occur there largely as constituents of minerals and organic
matter and in smaller amounts in the so-called exchangeable (adsorbed) ionic form. The adsorbed
and ionic forms are extracted readily when contacted by plant roots and provide the active fertility
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