Home 4. Implementing field trials Local results and conclusions General conclusions for groups of techniques

General conclusions for groups of techniques Print

There are no best practices, only local solutions. Each site has its specific set of bio-physical, social and economic circumstances that each plays a role in the success. In general there are clear positive results, especially in terms of ecological benefits. The techniques selected in Research Theme 3 have clear effects on most sites. Where they don’t, it can be explained why.

 

Techniques that work well must directly benefit farmers or else the investment will be too big. If the benefit is not directly experienced (such as for instance for soil erosion) it is even more difficult. There are usually compelling reasons, from a farmer’s points of view, not to implement a technique that is successful from a desertification point of view. Success based on longer trials and demonstration farms and even education/extension programs could be helpful. Generally desertification addresses a problem that has a much larger scale than can be addressed by the farmers alone, and they correctly claim that help and subsidy is needed. Also the comparison confirms that desertification can only be addressed if there are direct benefits in terms of production and income. If benefits take a few years to establish (such as with minimum tillage and grazing management) subsidy is needed to overcome the first few years.

 

The efficiency of combatting desertification of the seven functional groups can be summarized as follows.

 

1. Minimum tillage

 
  

Crete: no-tillage under olive trees: (top) no-tillage and no herbicide; (middle) no-tillage and herbicide; (bottom) conventional tillage. The difference in soil cover is clearly visible.

 

This technology is meant to restore a natural stable soil structure, which is relatively rich in organic matter. A good soil structure will increase infiltration and reduce runoff and erosion, and the surface is stronger in a sense protection against rainfall impact. The increased infiltration promotes water availability. On the down side there has to be some pest control at the moment of crop emergence, which is usually achieved with a combination of herbicides and light tillage. This land use system only works for cereals, not for root crops.

 

The results from the experiments show that under the right circumstances these mitigation processes are actually achieved, except in Morocco where the soil is very stony and has to be ploughed to make any type of sowing feasible.

 

Generally water availability increases, as well as a reduction in runoff. The method works well in combination with other conservation practices such as increasing soil cover. Environmental effects from using more herbicides were not included in the study and unfortunately no conclusions van be drawn in that respect. In spite of the relatively positive bio-physical effects, this technology is not well accepted by the farmers for several reasons.

 

Crop yield is usually slightly lower, although still on comparable levels with the conventional tillage methods. Thus there is a drop in income which is only positive because the expenses are less. In these expenses however labour is also included as a cost factor (besides lower fuel costs), but labour may not always be expressible in hard cash, where it concerns family labour. With this in mind the reason for doing minimum tillage would be to control erosion. The increased water availability is generally considered moderately positive. Erosion control however does not translate directly in yield increase and the offsite effects are not the responsibility of farmers alone. Erosion is therefore not seen as an immediate problem and that benefit does not outweigh the trouble of implementing minimum tillage. Lastly minimum tillage field look different form conventional fields, often less “clean”. The social implication is that you are a “bad” or “lazy” farmer, which is a strong negative incentive.

 

 

2. Soil cover, mulch and residue management
 
 

The effects of these measures are a protection of the soil, obstruction to runoff control and protection against direct surface evaporation, conserving water. Green cover/green manure can be used between annual crops to cover the soil during a bare period in the growing season (such as with alfalfa or mustard seed). Nitrogen rich species are used that are ploughed into the soil as extra nutrient supply and structure improvement.

 

Experiment combining green manure and minimum tillage in Spain

In a different fashion green cover can also be introduced in orchards to cover bare area between the trees, as is the case for almonds (Spain) or olives (Crete). On the down side the mulch may actually also intercept rainfall, while green cover can in certain situations be in competition for water with the first crop (almonds, olives).

 

The overall results of these experiments are unclear. In the first place in semi-arid environments it is not easy to get mulch, biomass is in short supply and it may even be expensive to obtain, while (at least in Spain) the results were not at all convincing. So mulch was not accepted by the farmers at all in this one case. Green manure between almonds had some clear positive effects but this may not outweigh the extra trouble, this depends on the price you get for the harvest of this second crop. So it is market driven. Green cover in olive groves has a clear effect in runoff and erosion mitigation, but farmers generally feared too much water competition, which could not really be disproven, and erosion conservation is not their first concern.

 

 

3. Runoff control
 
 

Turkey: contour ploughing and fencing on small dykes following contour lines Cape Verde: vegetative barrier helps to make terraces Mexico: construction of check dams

 

The purpose of these measures is always twofold: reduce runoff and erosion, and increase water availability through increased infiltration. This is a mixed group of various techniques, from actual terracing subsidized by the government (China, Cape Verde) to a stakeholder approach in Turkey (Eskeshir) where farmers made fences woven from branches that capture sediment and runoff that will gradually form terraces. In general the results are good if the terraces are established with outside help and people are used to it. This experience is confirmed form many parts in the world (Nepal, Peru, South East Asia). Water availability is higher, crop yield is also higher in all cases. However from a point of view of local stakeholders, soil erosion is seen as a wider problem where it concerns offside effects, and the responsibility of the government. Also, teraccing is very expensive, needs a great deal of technical experience to avoid erosion and landslides, and generally destroys the soil structure when they are created, which takes long to restore. The project results confirm that it is almost never a local stakeholder solution that can be carried by the community.

 

The experience of Turkey however shows that good results can be obtained with a much less rigorous intervention: woven fences are easy to establish and restore and combined with contour plouging work well to increase moisture and prevent runoff. However, again there is a downside that might prevent farmers from using this technique: depending on the field shape and orientation towards the slope direction, the technique may result in very short and wavy tillage lines with many tractor turns needed. The tractor is also hampered by the fences. Thus operational costs may be higher, while the yield may be lower. In Turkey this was not the case: yield was actually higher but the reasons were not quite clear.

 

 

4. Water harvesting
 
   

The water harvesting techniques tested are all related to capturing natural runoff and leading this to terrace like, flat pieces of land. In Tunisia this system has been used for many decades and people are used to it and know exactly what they can expect. Water of the surrounding area is captured to have a (sometimes subsistence) olive harvest. Since this is in a true arid area with very low rainfall, there would be no agricultural activity without this system. Thus here is not really a unmitigated system to test. It can be said however that the groundwater is sometimes also for additional watering and this causes overexploitation. The system functions if it is combined with groundwater infiltration zones. There is complete acceptance of this technique as it is the only low-cost solution available. However, it may not give a secure future for younger generations.

In Spain, a similar traditional water harvesting system exists, using natural runoff water (traditional boqueras system), combined with almond orchards. It is being revived after having been neglected for a period of time, due to economic fluctuations. It works well in terms of increased water availability, increasing yield. It will not be available to everybody because your fields need to be downstream of a water delivering system. An added benefit might be that the natural surrounding area increases in value.

 

Spain: boquera system inlet gate on almond terrace

In China bench terraces and check dams are being built by the government that also serve as water harvesting systems, simply because the steep slope and fast runoff is now being captured on the flat terrace surfaces. The construction is expensive and can only be done by the government, who is interested in decreasing downstream sediment problems (because of hydroelectric power installations and domestic and industrial use of river water). Once established, the terraces work well and show increased yields and decrease of soil loss. Currently farmers in the area find work outside agriculture and the interest is less.

 

China: (top) check dam land; (bottom) bench terraces

 

 

5. Irrigation management
 
 

Salinised soil Sprinkler system in the Novy study site Installing drip irrigation lines in tomato plots, Dzhanybek

Irrigation is of course done in areas with water shortage to be able to grow crops. In all areas however there was a risk of salinization, because of brackish groundwater and high evaporation. Salts concentrate in the top soil over time and decrease yields. Salinisation is very difficult to combat. Flushing with fresh water (as is done in Nestos) is usually expensive and the water has to be available. Drip irrigation is very successful: the water use declines improving the overall water availability and reducing the dependence on brackish groundwater. The detrimental effect on the soil surface of excessive furrow irrigation is absent. Yields are high although they were tested for tomatoes grown at vegetable garden scale, and not for large scale cereals. Drip irrigation also promotes much better water management; furrow irrigation system can be very uneconomical with excess water use (as in the Novy site in Russia) and Sprinkler irrigation can also waste water because of direct evaporation and wind action. Drip irrigation might actually also be a solution for the Greek site of Nestos, but this was not tested. The downside is that drip irrigation systems cost some initial investment, so it depends on the local situation of taxes on water use, fuel expenses for pumping large amounts of water in furrow systems etc.

 

 

6. Rangeland management
 
    

This technique promotes to set aside a part of a communal grazing area so that there can be a natural reseeding of species and a higher boidiversity. Often overgrazed lands still have vegetation but generally unpalatable for cattle and sheep, even for goats. Bushes are thorny or have chemicals that prevent eating. Set aside of grazing areas gave very positive and immediately visible results in an increase in biomass, cover and species composition. The returning species (possibly dormant in the soils) were of a high quality for grazing.



Morocco: gully stabilisation with Atriplex
This technique was used directly to increase the rangeland quality (Tunisia, Crete) or it was used in combination with various erosion mitigation measures such as gully control (Morocco). Stakeholders see and recognize the benefits and are generally positive because the implications for their lifestock are immediate. However there are important initial constraints and considerations:

 

  • Setting aside a part of the land there must be some fencing to keep cattle out, that is often free roaming. Fencing and maintenance are very expensive. Possibly in a larger integrated approach, areas that have natural barriers (valleys) could be assigned as set aside.
  • In the first few years when restoration is established, there is potentially too much cattle in an area because part is set aside. Thus calls for a decrease in livestock (very sensitive issue) or extra feeding with fodder brought in, and therefore a subsidy would be needed.
  • When cattle is kept out of restricted areas, care must be taken that not other areas become overgrazed. For instance in Morocco the Mamora forest is already under pressure from overgrazing, and large scale protection of gullies would be detrimental for this forest. An integrated approach is needed.
  • Land rights are often a sensitive issue so delineating lands means also defining rights of grazing. This on the one hand might promote a democratic and discussion process, but is a very sensitive issue that cannot be done by outside “scientific” teams.
     

 

7. Forest fire management
 
 

In Portugal two techniques for forest fire mitigation have been tested: strip networks where vegetation is cut along major roads, and prescribed burning. The latter is a technique to do controlled burning in spring to reduce the fuel load in summer and thus prevent heavy fires. Both have as an added problem that the bare areas might result in increased soil erosion. The soil surface may become water repellent after burning due to the heat of the fire that affects the organic matter in the soil. Soil erosion was not really a problem in case of the strip network. It might become a problem when he network is extended to secondary roads.

 

Prescribed burning, during the wet period seems to have less impacts on the soil and vegetation than the summer wildfires, therefore it is suitable as a land management technique. It has a reduced cost/effect rate, especially when compared with other techniques. It can be used to promote higher landscape diversity and therefore promote biodiversity. The landscape diversity can induce a higher diversity of economic activities, therefore increasing the appeal of mountain areas, by improving the local community’s livelihoods.

 

 

More details ... download the full report

Comparison of conservation technologies and identification of best practices (Report 99 D4.5.1 May12) [3.51Mb]

 
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