Page 97 - Soil Degradation, Conservation and Remediation

84 3 Soil Erosion by Water

• Integrating erosion control measures: Usually, no one method alone is suffi cient
for the control of soil erosion. For example, integrating mulching with no-tillage
can effectively reduce erosion.
• Regular maintenance of erosion control measures. Practices for erosion control

need to be maintained regularly. Terraces may need mending and barriers may
need reconstruction.

3.4.1 Amendments

Addition of manures and composts favors structure formation; increases aggregate
stability, porosity, and infiltration; and thus reduces runoff. Manuring can reduce

water runoff by 70–90 % and sediment loss by 80–95 % as a result of increased
organic matter content (Grande et al. 2005 ). Using manure in combination with
other conservation practices, such as no-till may be an effective strategy for reduc-
ing soil erosion. However, indiscriminate use of manure may have detrimental
impacts on water quality as well.
Farmers in some parts of the USA and other areas are increasingly using poly-
acrylamide (PAM) in irrigated soils. The PAM molecules stabilize the aggregates
−1
and reduce soil particle detachment. Application of 2–4 kg ha of PAM can
reduce soil erosion by 70–90 % in some soils but only by 20 % or less in others
(Bjorneberg et al. 2000 ). Some steeply sloping heavily irrigated soils may need as
−1
6
high as 20 2–4 kg ha . It reduces soil erosion by about 1 × 10 Mg annually in
Western and Northern USA (Sirjacobs et al. 2000 ). Its use doubled between 1995
and 2005 in irrigated fi elds ( > 200,000 ha) for reducing furrow and sprinkler irri-
gation-induced soil erosion (Sojka 2006 ). PAM can mitigate the erosion rates by
as much as 95 % and increase the infiltration rates by 15 and 50 % in furrow-

irrigated croplands.

3.4.2 Cover Crops

According to the Soil Science Society of America, cover crops are close-growing
crops that provide soil protection, seeding protection, and soil improvement between
periods of normal crop production or between trees in orchards and vines in vine-
yards (SSSA 2008 ). Cover crops can be used as green manure crops. Cover crops
are used for soil conservation from ancient times in Greece, Rome, China, and other
regions (Magdoff 1992 ). Cover crops are presently used as an important companion
practice to no-till, reduced tillage, alley cropping, agroforestry, and other conserva-
tion practices designed to reduce soil erosion and improve quality of soil and water

resources. Cover crops offer the following benefits: (i) protecting soil against ero-
sion, (ii) improving soil properties, (iii) enhancing soil fertility, (iv) suppressing
weeds, (v) fixing N, (vi) increasing soil organic matter content, (vii) increasing crop