Agriculture Reference
In-Depth Information
TABLE 8.1
Optimum Soil Temperature for the Growth and Development
of Important Crop Species
Crop Species
Temperature (°C)
Alfalfa
21-27
Barley
18-20
Dry bean
28-30
Cassava
25-29
Corn
25-30
Coffee
20-26
Cotton
28-30
Cowpea
20-35
Mung bean
20-30
Oats
15-20
Peas
18-22
Potato
20-23
Peanut
24-33
Pigeon pea
18-29
Rice
25-30
Soybean
22-27
Sesame
25-27
Sorghum
27-30
Sugarbeet
18-24
Sugarcane
25-30
Sunflower
23-25
Sweet potato
24-26
Tobacco
22-26
Tomatoes
25-30
Wheat
20-30
Source:
Adapted from Voorhees, W. B., R. R. Allmares, and C. E. Johnson. 1981.
Modifying the Root Environment to Reduce Crop Stress
, pp. 217-266.
St. Joseph, Michigan: Am. Soc. Agric. Eng.; Fageria, N. K. 1989.
Tropical
Soils and Physiology of Field Crops
. Brasilia: EMBRAPA-CNPAF; Fageria,
N. K. 1992.
Maximizing Crop Yields
. New York: Marcel Dekker.
gram per cubic cm (g cm
−3
). If 1 cm
3
of the soil weighs 1.3 g, the soil has a bulk density equal to
1.3 g cm
−3
. Dry weight refers to the weight of the soil dried at 105-110°C and the volume of the soil
refers to the combined volume of the soil solids and pore space.
The bulk density of most surface soils usually ranges from 1.0 to 1.6 g cm
−3
or from 1.0 to
1.6 Mg m
−3
. Compacted subsoils have bulk density values reaching 1.8 g cm
−3
or 1.8 Mg m
−3
or
more. High bulk density values (greater than 1.6 Mg m
−3
) indicate limited soil aeration, very
slow water movement, poor drainage, and impedance to root growth. High bulk density for
surface soils indicates the presence of soil crust that critically retards seed germination. Bulk
density can be improved with the addition of organic manures and incorporation of crop residues
into the soil. In addition, the use of appropriate crop rotation can also improve soil bulk density.
The adequate value of bulk density in the soils permits better root growth and distribution in the
soil profile. Plant roots in a noncompacted soil have a more extensive feeding zone than those in
a similar soil with a compacted layer. In the presence of a hard pan, the development of the root
