7.3.4 Discussion and Conclusion
A major observation to be made of these case studies is that the impact of SCT
changed over time, allowing the implementation of adaptation measures which
enhanced the attractiveness of such technologies. In the case of Ban Bo Muang Noi
in Thailand, contour hedgerows were important at reducing run-off and soil loss, in
particular when the fields were first established. When contour hedgerows were
combined with the use of additional SCT, such as minimum tillage and mulching,
hedgerows had a less important role to play in the reduction of soil losses in the later
phases. In contrast, minimum tillage treatments combined with cover crops proved
to be a potential alternative in terms of soil conservation measures in cropping
systems, as well as for stabilizing or even improving yields without the major
disadvantage of using hedgerow systems. The use of SCT positively influenced
maize grain yields, and also showed that even under unfavorable growth conditions,
as in the case of the intermediate drought period during the wet season of 2010 in
Chieng Khoi, relay cropping was a viable option in terms of sustaining crop yields –
outperforming all other treatments. Herein lays an opportunity for the successful
and sustainable establishment of SCT as an integrated rather than individual
adoption concept. Combining temporal barriers; for example, a natural vegetation
strip, together with minimum tillage and relay cropping (legume) could be a viable
alternative to the well-known and commonly used contour hedgerow systems. In
combination with hedgerows, these systems may be used during the initial vegetation phase of a cropping system, to be removed thereafter once the system is well
established. This would also avoid further competition between barrier hedges and
crops (Pansak et al. 2007), which is probably one of the reasons for low adoption
rates among farmers. When using conservation agriculture (without hedgerows),
run-off still exists but is “cleaner” (at least during small to moderate rainfall events)
due to a reduced soil detachment and hence lower transportation of sediment loads
down slope. Therefore, in situations where reducing run-off is not the major goal, a
combination of minimum tillage and mulching, together with relay cropping, may
provide a sustainable agricultural practice in sloping environments. Findings from
the relay cropping field trial in Chieng Khoi also show that even with initial low soil
fertility levels and a resulting slower build-up of a protective cover and mulch layer,
crop growth performance was sustained, even under the unfavorable cropping
conditions that occurred in 2010. However, the results also demonstrate the importance of the careful selection of an appropriate cover crop partner and system to
avoid detrimental effects. Further aspects such as observed improvements of the
soil’s physical structure, as associated with an increase in soil infiltration rates
(G. Clemens; personal communication), have not been further elaborated upon in
this chapter, however, they are further signs of the positive aspects of SCT.
7 Soil Conservation on Sloping Land: Technical Options and Adoption Constraints
247
A major observation to be made of these case studies is that the impact of SCT
changed over time, allowing the implementation of adaptation measures which
enhanced the attractiveness of such technologies. In the case of Ban Bo Muang Noi
in Thailand, contour hedgerows were important at reducing run-off and soil loss, in
particular when the fields were first established. When contour hedgerows were
combined with the use of additional SCT, such as minimum tillage and mulching,
hedgerows had a less important role to play in the reduction of soil losses in the later
phases. In contrast, minimum tillage treatments combined with cover crops proved
to be a potential alternative in terms of soil conservation measures in cropping
systems, as well as for stabilizing or even improving yields without the major
disadvantage of using hedgerow systems. The use of SCT positively influenced
maize grain yields, and also showed that even under unfavorable growth conditions,
as in the case of the intermediate drought period during the wet season of 2010 in
Chieng Khoi, relay cropping was a viable option in terms of sustaining crop yields –
outperforming all other treatments. Herein lays an opportunity for the successful
and sustainable establishment of SCT as an integrated rather than individual
adoption concept. Combining temporal barriers; for example, a natural vegetation
strip, together with minimum tillage and relay cropping (legume) could be a viable
alternative to the well-known and commonly used contour hedgerow systems. In
combination with hedgerows, these systems may be used during the initial vegetation phase of a cropping system, to be removed thereafter once the system is well
established. This would also avoid further competition between barrier hedges and
crops (Pansak et al. 2007), which is probably one of the reasons for low adoption
rates among farmers. When using conservation agriculture (without hedgerows),
run-off still exists but is “cleaner” (at least during small to moderate rainfall events)
due to a reduced soil detachment and hence lower transportation of sediment loads
down slope. Therefore, in situations where reducing run-off is not the major goal, a
combination of minimum tillage and mulching, together with relay cropping, may
provide a sustainable agricultural practice in sloping environments. Findings from
the relay cropping field trial in Chieng Khoi also show that even with initial low soil
fertility levels and a resulting slower build-up of a protective cover and mulch layer,
crop growth performance was sustained, even under the unfavorable cropping
conditions that occurred in 2010. However, the results also demonstrate the importance of the careful selection of an appropriate cover crop partner and system to
avoid detrimental effects. Further aspects such as observed improvements of the
soil’s physical structure, as associated with an increase in soil infiltration rates
(G. Clemens; personal communication), have not been further elaborated upon in
this chapter, however, they are further signs of the positive aspects of SCT.
7 Soil Conservation on Sloping Land: Technical Options and Adoption Constraints
247