Agriculture Reference
In-Depth Information
TABLE 4.5
Fundamental Prerequisite of an Appropriate Crop Rotation
Prerequisite
Advantage
Including legume crops in rotation
Supply N to succeeding crops.
Including crops of different root
architecture
Improve soil physical and chemical properties, such as
nutrient uptake from deeper soil layers, soil porosity,
aeration and drainage, and improve SOM content.
Including appropriate cover/green
manure crops in the rotation
Protect soil from erosion, control weeds, supply OM,
conserve moisture, improve soil hydraulic conductivity, and
control diseases and insects.
Include crops with different
resistance to diseases and insects
Break the cycle of diseases and insects, and reduce the host
plant presence in rotation.
Include crops suited to a given
agroecological region
Better economic return and ecologically viable.
organic amendments in crop rotations provided a measurable increase in SOM quality and other soil
quality attributes compared with continuous cereal systems.
Crop rotations have positive effects on soil properties related to the higher C inputs and diversity
of plant residues to soils in comparison with continuous systems (Miller and Dick, 1995; Entry
et al., 1996; Moore et al., 2000; Acosta-Martinez et al., 2004). Conservation tillage increases soil
organic C (Franzluebbers et al., 1995; Deng and Tabatabai, 1997; Acosta-Martinez et al., 2003) and
microbial biomass (Angers et al., 1993; Franzluebbers et al., 1994, 1995) to modify the soil micro-
bial community (Acosta-Martinez et al., 2004).
4.8.3 u
se
of
a
dequate
r
ate
of
f
ertIlIzers
The use of an adequate rate of fertilizers for annual crops is an important factor in increasing crop
productivity and SOM content. Bremer et al. (2011) reported that the application of synthetic fer-
tilizers consistently increased the crop yield and SOC. Hsieh (1992, 1996) reported that yields of
plots with no fertilizer and continuous corn were consistently the lowest and corn yields of plots
with fertilizer and rotation were consistently the highest. A higher grain yield generally produced
higher straw yields as well as higher roots biomass (Baligar et al., 1998; Fageria and Baligar, 2005).
A higher straw yield and root biomass may improve the OM content of the soil.
Modern agriculture is characterized by an exponential increase in the use of N fertilizers
(Vitousek et al., 1997). Increased rates of N
2
O evolution by N-fertilized soils are well documented
in field and laboratory studies (Sarawat and Keeney, 1986). Thus, the accelerated application of N
fertilizers in crop production is regarded as the major reason for enhanced N
2
O release from soils,
and agriculture is currently estimated to contribute 90% of the total anthropogenic N
2
O emissions
(Duxbury, 1994). Under these situations, the use of an adequate rate of N is an important component
of precise agriculture and one of the most critical environmental challenges related to soil quality.
The use of an adequate N rate in cropping systems can improve soil carbon (Potter et al., 1997;
Salinas-Garcia et al., 1997; Halvorson et al., 2002). Rasmussen and Rohde (1988) and Robinson
et al. (1996) reported linear increases in SOC with applied N fertilizer, and they also noted that crop
residue has a positive impact on SOC.
Ladha et al. (2012) evaluated the impact of commercial fertilizer N on SOM from long-term
experiments and concluded that the application of N fertilizer leads to a slower decrease in SOM
contents, or may cause a small increase, after a new equilibrium is reached following N applica-
tion. Like N, the use of an adequate rate of P is also important for improving the OM content
of soils and consequently crop yields and soil quality. The lack of an adequate level of P in the
