Introduction

Soil degradation by accelerated water and wind-induced erosion is a serious problem and will remain so during the 21st century, especially in developing countries of tropics and subtropics. Erosion is a natural geomorphic process occurring continually over the earth's surface. However, the acceleration of this process through anthropogenic perturbations can have severe impacts on soil and environmental quality.

Accelerated soil erosion has adverse economic and environmental impacts (Lal, 1998). Economic effects are due to loss of farm income due to on-site and off-site reduction in income and other losses with adverse impact on crop/ animal production. The on-site and off-site effects of soil erosion on productivity are depicted in Figure 1 and Figure 2, respectively. Off-site economic impact of soil erosion is presented in Figure 3. Table 1 shows regional food production statistics for 1995 with and without soil erosion in the world. The data in Table 1 indicate total loss of food production at 31 M Mg for Africa, 190 M Mg for Asia and 18 M Mg for tropical America.

Satellite Remote Sensing and GIS Applications in Agricultural Meteorology pp. 315-330

Short term productivity effects

• loss of water •additional tillage

• loss in time due to delayed sowing

On-site Productivity

Loss

Long term productivity effects

• decline in soil structure

• reduction in AWC

• decrease in soil organic matter content

• tillage erosion

Reduction in land/soil quality

• temporary decline in land/soil quality

• transient pollution of surface water by sediment-borne chemicals

Figure 1: On-site effects of soil erosion on productivity are due to short-term and long-term effects, and on decline in soil quality (Lal, 2001)

Short term effects

• Seedling burial

• inundation of low laying area

• chemical effects on seedling due to chemical run-off

• delayed sowing

^ Off- site Productivity l effects

Long term effects •burial of topsoil by infertile subsoil • change in drainage conditions •alteration of slope by tillage

Reduction in land/soil quality

• permanent decline in land/soil quality/ due to gullying

• alterations in soil-water regime and/ water table

• additional water management „e-g- irrigation, drainage

Figure 2: Off-site effects of soil erosion on productivity may be due to short-term or long-term and due to decline in land/soil quality (Lal, 2001)

Table 1. Regional food production statistics for 1995 with (a) and without (b) soil erosion (Lal, 2001)

X lOOOOOO

Roots and tubers

X 1000000

A

B

A

B

A

B

A

B

North Central America

358

376(5)

61

64(5)

6

65(b)

28

29(5)

Europe

268

281(5)

1

1(5)

6

6(5)

80

84(5)

Oceania

27

28(10)

-

-

2

2(15)

3

3(10)

Africa

100

110(10)

0.5

0.6(20)

7

8(20)

135

155(15)

Asia

929

lO68(l5)

2l

23(lO)

27

3l(l5)

248

293(l8)

South America

90

99(10)

41

45(10)

4

4(10)

46

51(12)

Others

124

130(5)

3

3(5)

4

4(5)

69

72(5)

Total

l896

2O92

l26

l36

5O

6l

6O9

687

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