Agriculture Reference
In-Depth Information
Average of two soil depths
3000
2000
Y = 1698.81 + 157.2508X - 4.1147X
2
1000
R
2
= 0.8060**
0
10-20 cm
3000
2000
Y = 1717.44 + 180.1304X - 5.4826X
2
1000
R
2
= 0.7800**
0
0-10 cm
3000
2000
Y = 1682.91 + 141.6395X - 3.3163X
2
1000
R
2
= 0.8138**
0
5
10
15
20
Magnesium saturation (%)
FIGURE 8.5
Relationship between magnesium saturation and grain yield of dry bean. (From Fageria, N. K.
2008.
Commun. Soil Sci. Plant Anal.
39:845-857. With permission.)
of the soil. Nutrient elements that are not immediately available to plants, such as those in primary
and secondary minerals and in semiresistant organic combinations, comprise the potential fertility
of the soil. Often, crop production is highly dependent upon the rate of transfer from the potential
to the active form.
Maintaining soil fertility at an adequate level is very important not only to improve crop yields
but also maintain the sustainability of the cropping systems. Soils of low fertility used for crop
production provide low yield as well as degrade more rapidly compared with soils of high fertility.
Crops produced on high-fertility soils produced a higher yield of straw and root biomass, which is
responsible for maintaining soil organic matter content at an adequate level (Fageria, 2013). The
export of grain or other produce from the land takes with it large quantities of N, P, K, and S
(Campbell et al., 1995). If these nutrients are not replaced (e.g., by addition of fertilizers), soil
organic matter and the fertility of the soil will gradually decline. Because fertilizers and the use
of legumes in the rotation increase the N supplying power of the soils, their regular use, year after
year, can lead to a significant improvement in the fertility of the soil (Campbell et al., 1995). Fageria
and Baligar (1997b) reported that an integrated nutrient management system should be adopted in
improving the nutrient use efficiency of annual crops. A model of integrated nutrient management
is presented by these authors (Figure 8.8).
