Agriculture Reference
In-Depth Information
the addition of organic matter has been reported by Kochain (1995). The functional groups involved
in metal complexation by organic matter are COOH and OH (Wong and Swift, 2003). Surface appli-
cation or surface incorporation of organic matter also decreased phytotoxic subsoil Al
3+
activities
because dissolved organic matter (DOM) that leached into the subsoil formed nontoxic Al-DOM
complexes (Hue, 1992; Liu and Hue, 1996; Hue and Licudine, 1999; Willert and Stehouwer, 2003).
The combined application of CaCO
3
and organic matter in lime-stabilized biosolids decreased sub-
soil acidity and increased subsoil Ca saturation, compared with CaCO
3
alone (Tan et al., 1985;
Brown et al., 1997; Willert and Stehouwer, 2003). This effect was attributed to increases in Ca
mobility caused by Ca-DOM complexes (Willert and Stehouwer, 2003).
Additional benefits of organic matter addition to acid soils are improving nutrient cycling and
availability to plants through direct additions as well as through modification in soil physical and
biological properties. A complementary use of organic manures and chemical fertilizers has proven
to be the best soil fertility management strategy in the tropics (Makinde and Agboola, 2002; Fageria
and Baligar, 2005). Enhanced soil organic matter increases soil aggregation and the water-holding
capacity, provides the source of nutrients, and reduces P fixation, toxicities of Al and Mn, and leach-
ing of nutrients (Baligar and Fageria, 1999). Build-up of organic matter through the addition of crop
and animal residues increases the population and species diversity of microorganisms and their
associated enzyme activities and respiration rates (Kirchner et al., 1993; Weil et al., 1993). The use
of organic compost may result in a soil that has greater capacity to resist the spread of plant patho-
genic organisms. The improvement in the overall soil quality may produce more vigorous-growing
and high-yielding crops (Brosius et al., 1998). All these changes create a favorable soil environment
for N uptake and use efficiency in crop plants.
8.2.2.5 Use of Balanced Nutrient Supply
The use of balanced nutrient supply improves N use efficiency in crop plants. Duan et al. (2011)
reported that unbalanced inorganic fertilization resulted in a decreased yield of corn and nitro-
gen use efficiency. These authors reported that nitrogen use efficiency in corn was increased from
20% to 45% by the application of P in adequate amounts along with N in corn. In addition, these
authors further reported that nitrogen use efficiency in corn was further improved by up to 70% with
the continuous application of farmyard manure. The application of farmyard manure is known to
improve soil physical and chemical properties, maintain soil fertility, and supply nutrients to crops
on time that will minimize N losses (Duan et al., 2011). Improvement in nitrogen use efficiency
with the addition of P in adequate amounts along with N has been reported by Almeida et al. (2000)
and Sa and Israel (1998). Wang et al. (2010) also reported that the use of adequate amounts of N
and P improved plant growth and N use efficiency in crop plants. Wang et al. (2010) reported that
agronomic efficiency could be improved from 3.5 kg grain kg
−1
N under the N treatment to 16.3 kg
grain kg
−1
N under the NP treatment in China in corn.
8.2.2.6 Crop Residue Management
Crop residues are defined as the parts of the plants left in the field after the crops have been harvested
and thrashed or left after the pastures are grazed (Kumar and Goh, 2000). They are a tremendous
natural resource and should not be considered as a waste. Crop residues are important for erosion
control, soil water storage, filling gaps in various agroecosystems-based modeling, and a sink for
atmospheric carbon (Aguilar et al., 2012). Data on nitrogen benefits and nitrogen recoveries from
residues show that a considerable potential exists from residues, especially leguminous residues, not
only in meeting the N demands of the succeeding crops but also in increasing the long-term fertility
of the soils (Kumar and Goh, 2000). The amount of N that recycle into agricultural fields through
residues may add 25-100 Tg of N year
−1
(Mosier and Kroeze, 1998). In addition, crop residues and
their proper management affect the soil quality either directly or indirectly (Fageria, 2002).
A number of studies have shown that the management of straw residues has the potential to alter
the magnitude of N immobilization. Managing the residue particle size may significantly alter the
