Agriculture Reference
In-Depth Information
Adoption of
appropriate
farming
system
Adequate plant
spacing and
density
Adequate soil
preparation
Soil and
plant tissue
analysis
Adequate use of
organic manures
and inorganic
fertilizers
Exploring plant
genetic variability
Integrated
plant nutrient
management
system
(IPMS)
Maintain adequate
level of soil O.M.
Favorable social-economical
factors for farmer
Control of
soil erosion
Avoid or minimize
water deficiency
Control of diseases,
insects, and weeds
Management of soil
acidity, salinity,
and sodicity
Use of
crop rotation
Control of
allelopathy
Sustainable crop productivity
FIGURE 8.8
Integrated plant nutrient management for sustainable crop production. (From Fageria, N. K.,
and V. C. Baligar. 1997b.
Int. J. Trop. Agric
. 15:1-18. With permission.)
environmentally sound practice to improve crop growth, including rice on saline soils (Fageria,
2014). Salt-tolerant crop species are barley, cotton, oats, rye, triticale, sugar beet, guar, and canola
or rapeseed (Fageria, 2014)
8.2.2.4 Use of Organic Manures
Organic manures are products from the processing of animals or vegetable substances that contain
a reasonable amount of plant nutrients to be of value as fertilizers. Brosius et al. (1998) reported
that plant- and animal-based organic by-products may substitute for commercial fertilizers and
enhance the chemical and biological attributes of soil quality in agricultural production systems.
Organic matter increases the soil's abilities to hold and make available essential plant nutrients
and to resist the natural tendency of the soil to become acidic (Cole et al., 1987). Furthermore,
the addition of organic manures to acid soils has been shown to increase soil pH, decreases Al
saturation, and thereby improves conditions for plant growth (Alter and Mitchell, 1992; Reis and
Rodella, 2002; Wong and Swift, 2003). All these processes improve N use efficiency. Miyazawa
et al. (1993) reported that crop residues of wheat and corn and 20 plant species utilized as green
manure increased soil pH and decreased the Al content of the soil. Several mechanisms have been
proposed for reducing acidity by organic manures. These mechanisms include specific adsorption of
organic anions on hydrous Fe and Al surfaces and the corresponding release of hydroxyl ions, which
increase soil pH (Hue, 1992; Wong and Swift, 2003). Adsorption of Al by organic matter sites and
the subsequent isolation of the inorganic phase to maintain the equilibrium Al activity in soil solu-
tion have been proposed to increase soil pH (Wong et al., 1998; Wong and Swift, 2003). Chelating
agents released by decomposing organic matter may detoxify Al ions.
Plant roots decay in the soil and form soil organic matter. Active roots also release organic acids
such as citrate, malate, and tartrate. These organic acids react strongly with Al and convert it into
less toxic organically bound forms (Yang et al., 2000). The organic Al affinities or stability con-
stants are in the order of citrate > tartrate > malate (Hue et al., 1986). The decrease in Al activity by
