**3. Results**

In 1999 we managed the set up of the erosion facility during June. Facing some problems with the equipment, necessary adjustments were carried out during July. With our first trial in 1999 we wanted to measure the effects of commercial and indigenous seed mixtures as well as the effect of an additional protection of soil surface. In order to avoid interactions with application techniques, we used normal hand sowing. During the investigation period, 2 heavy raining events with a precipitation of more than 15 mm h-1 took place. Figure 2 shows the summarized surface runoff and soil losses depending on 362 mm precipitation. During our first inspection we noticed a blockage of the sampling tube of chamber three. Therefore, surface runoff from this plot did not describe the actual amount. However, between 6 % and 11 % of the precipitation did not infiltrate to the soil. In comparison, the additional cover of soil surface was able to reduce surface runoff to 1 % of corresponding precipitation. A similar relation was observed with soil losses. On the two chambers with hand sown seed mixtures soil losses from 640 kg ha-1 (commercial mixture) up to 780 kg ha-1 (indigenous seed mixture) were measured. The straw mat was able to reduce soil losses to 26 kg ha-1, an amount of 4 % compared to chamber 1.

measure possible differences in surface runoff and soil losses of the described application techniques during the second vegetation period after sowing. The corresponding vegetation cover of the three chambers was measured at the end of June 2002. During the investigation period of 2001, a precipitation of 568 mm, during 2002 a precipitation of 1,066 mm was

Photo 4. The experimental trial after the application of the different techniques

26 kg ha-1, an amount of 4 % compared to chamber 1.

In 1999 we managed the set up of the erosion facility during June. Facing some problems with the equipment, necessary adjustments were carried out during July. With our first trial in 1999 we wanted to measure the effects of commercial and indigenous seed mixtures as well as the effect of an additional protection of soil surface. In order to avoid interactions with application techniques, we used normal hand sowing. During the investigation period, 2 heavy raining events with a precipitation of more than 15 mm h-1 took place. Figure 2 shows the summarized surface runoff and soil losses depending on 362 mm precipitation. During our first inspection we noticed a blockage of the sampling tube of chamber three. Therefore, surface runoff from this plot did not describe the actual amount. However, between 6 % and 11 % of the precipitation did not infiltrate to the soil. In comparison, the additional cover of soil surface was able to reduce surface runoff to 1 % of corresponding precipitation. A similar relation was observed with soil losses. On the two chambers with hand sown seed mixtures soil losses from 640 kg ha-1 (commercial mixture) up to 780 kg ha-1 (indigenous seed mixture) were measured. The straw mat was able to reduce soil losses to

registered by our climatic station.

**3. Results** 

Fig. 2. Soil losses and surface runoff depending on precipitation (362 mm), observation period from 02-08-99 to 02-09-99

In the last week of June 2000, the second trial started. This year the investigation period lasted for 18 weeks with a precipitation of 810 mm. During the investigation period, 3 heavy raining events took place. The equipment worked without technical problems. This year we wanted to measure the effects of normal hand sowing in comparison to the very common techniques of hand sowing plus cover crop and hand sowing plus nursery grass as typical cover crop, we used rye of the old landrace "Tyrolean summer rye". As nursery grass, we chose *Lolium perenne* of the variety "Guru", a variety with very good winter hardiness. Corresponding to the extended investigation period, total surface runoff and soil losses were higher in comparison to the year before. Surface runoff of normal hand sowing reached 9.6 % of precipitation, 2 % less than the year before (Figure 3). The effect of cover crop and nursery grass was visible. However, surface runoff decreased only to a percentage of 8.9 for nursery grass and 8.6 for cover crop. Soil losses of chamber 1 reached nearby 2.8 t ha-1. Again, a bit lower values were measured for hand sowing plus cover crop (2.68 t ha-1) and the technique using nursery grass (2.37 t ha-1). In a general view, the reduction of surface runoff and soil losses with the help of fast growing but short living components of the seed mixtures was not substantial. The available water samples and the eroded soil material (particles smaller than 2 mm in diameter; g m-²) were analysed in order to get information about nutrient losses.

Differences in nutrient value of single samples were very high. Therefore, no exact interpretation of results was possible. In a general view, nutrient losses were below 0.5 kg ha-1 for P and from 1 to 1.5 kg ha-1 for K, corresponding to the poor nutrient content of the

Soil Erosion and Surface Runoff on Slopes in Mountain Environment

In comparison, only 12 kg ha-1 soil was washed out below the straw net.

as hourly sum total. From 9:00 to 24:00, a precipitation of 47 mm was measured.

Fig. 5. Sum of precipitation and surface runoff in comparison of different application

The sum up of surface runoff for chamber one reached 15.8 % of precipitation, for chamber two 12.3 % and for chamber three only 1.8 %. This example showed that during periods with heavy raining events the proportion of surface runoff and therefore soil losses increases, compared to average precipitation. Figure 6 shows the same correlation between precipitation and surface runoff depending on application technique described as hourly mean values. With this figure it can be observed, that there is a delay between precipitation and surface runoff from half an hour to two hours, depending on intensity of precipitation

techniques during a raining event (Krautzer & Klug 2009).

and absorbability of the soil.

Depending on Application Technique and Seed Mixture – A Case-Study 203

The third trial was set up at the end of June 2001. It was decided to run the erosion facility up to the end of vegetation period 2002 in order to get information about erosion processes the year after restoration. The first period lasted for 15 weeks with a precipitation of 568 mm and 1 heavy raining event. The equipment worked without technical problems. With this final trial we compared the technique hand sowing plus cover crop (this year oat, also a very common cover crop for restoration) to the world wide most used technique hydroseeding. As third technique, we chose hydroseeding with an additional cover of soil surface by the straw mat in order to measure the influence of protection by organic material a second time. Surface runoff from chamber 1 (hand sowing) reached 6.5 % of corresponding precipitation (Figure 4). For application technique hydroseeding, 5.5 % were measured. Again, the additional protection of soil surface led to a clear reduction of surface runoff, this time below 0.5 %. Results obtained showed soil losses of more than 4 t ha-1 for chambers 1 and 2.

Figure 5 shows the connection between precipitation and surface runoff depending on application technique during a raining event that took place on 10th August 2001, described

soil (Table 1). A comparison of the amounts of losses of N, P, K and Mg between the single trials approximately reflected their different stability against erosion.

Fig. 3. Soil losses and surface runoff depending on precipitation (810 mm), observation period from 21-06-00 to 25-10-00

Fig. 4. Soil losses and surface runoff depending on precipitation (568 mm), observation period from 27-06-01 to 11-10-01

soil (Table 1). A comparison of the amounts of losses of N, P, K and Mg between the single

Fig. 3. Soil losses and surface runoff depending on precipitation (810 mm), observation

Fig. 4. Soil losses and surface runoff depending on precipitation (568 mm), observation

period from 21-06-00 to 25-10-00

period from 27-06-01 to 11-10-01

trials approximately reflected their different stability against erosion.

The third trial was set up at the end of June 2001. It was decided to run the erosion facility up to the end of vegetation period 2002 in order to get information about erosion processes the year after restoration. The first period lasted for 15 weeks with a precipitation of 568 mm and 1 heavy raining event. The equipment worked without technical problems. With this final trial we compared the technique hand sowing plus cover crop (this year oat, also a very common cover crop for restoration) to the world wide most used technique hydroseeding. As third technique, we chose hydroseeding with an additional cover of soil surface by the straw mat in order to measure the influence of protection by organic material a second time. Surface runoff from chamber 1 (hand sowing) reached 6.5 % of corresponding precipitation (Figure 4). For application technique hydroseeding, 5.5 % were measured. Again, the additional protection of soil surface led to a clear reduction of surface runoff, this time below 0.5 %. Results obtained showed soil losses of more than 4 t ha-1 for chambers 1 and 2. In comparison, only 12 kg ha-1 soil was washed out below the straw net.

Figure 5 shows the connection between precipitation and surface runoff depending on application technique during a raining event that took place on 10th August 2001, described as hourly sum total. From 9:00 to 24:00, a precipitation of 47 mm was measured.

Fig. 5. Sum of precipitation and surface runoff in comparison of different application techniques during a raining event (Krautzer & Klug 2009).

The sum up of surface runoff for chamber one reached 15.8 % of precipitation, for chamber two 12.3 % and for chamber three only 1.8 %. This example showed that during periods with heavy raining events the proportion of surface runoff and therefore soil losses increases, compared to average precipitation. Figure 6 shows the same correlation between precipitation and surface runoff depending on application technique described as hourly mean values. With this figure it can be observed, that there is a delay between precipitation and surface runoff from half an hour to two hours, depending on intensity of precipitation and absorbability of the soil.

Soil Erosion and Surface Runoff on Slopes in Mountain Environment

(Figure 7).

kg ha-1.

from 2-5 l m-².

Depending on Application Technique and Seed Mixture – A Case-Study 205

We extended the trial for one more vegetation period in order to get information about erosion processes the year after restoration. The second period of this trial lasted for 13 weeks with a precipitation of 1,066 mm, a wet summer with 14 heavy raining events. In June 2002, a vegetation cover of 70 % on chamber 1, 75 % on chamber 2 and 80 % on chamber 3 (plus 16 % additional cover from the residual material of the straw mat) was observed. The results show a clear reduction of surface runoff in comparison to 2001

Photo 5. Vegetation cover on the plot with the technique hand sowing plus cover crop a year

Again, for the techniques hand sowing and hydroseeding the highest water flow was measured, but in relation to total precipitation only 0.5 % respectively 0.4 % of total precipitation. The soil losses for both techniques were between 29 and 44 kg ha-1, an amount that is neglectable. However, again the technique with straw mat performed much better in comparison, with surface runoff of less than 0.2 % of total precipitation and soil losses of 4

Water flow and soil losses are not only a result from total precipitation. Both the intensity of the raining event and the kinetic energy from the raindrops reaching the soil surface are responsible for erosion. Therefore, a direct comparison of all assessed application techniques between years is not possible. However, Figure 8 gives a general view of surface runoff caused by all compared application techniques from 1999 to 2001, referring to 500 mm precipitation. Using cheap application techniques like hand sowing, cover crop or nursery

additional protection of soil surface was able to cause a clear reduction to a surface runoff

² was measured. Only the

after setup (2002), the fine-grained material was washed out

grass as well as hydroseeding, surface runoff from 28-58 l m-

Fig. 6. Hourly values of precipitation and surface runoff in comparison of different application techniques during a raining event

Fig. 7. Soil losses and surface runoff depending on precipitation (1,066 mm), observation period from 23-05-02 to 28-08-02

Fig. 6. Hourly values of precipitation and surface runoff in comparison of different

Fig. 7. Soil losses and surface runoff depending on precipitation (1,066 mm), observation

application techniques during a raining event

period from 23-05-02 to 28-08-02

We extended the trial for one more vegetation period in order to get information about erosion processes the year after restoration. The second period of this trial lasted for 13 weeks with a precipitation of 1,066 mm, a wet summer with 14 heavy raining events. In June 2002, a vegetation cover of 70 % on chamber 1, 75 % on chamber 2 and 80 % on chamber 3 (plus 16 % additional cover from the residual material of the straw mat) was observed. The results show a clear reduction of surface runoff in comparison to 2001 (Figure 7).

Photo 5. Vegetation cover on the plot with the technique hand sowing plus cover crop a year after setup (2002), the fine-grained material was washed out

Again, for the techniques hand sowing and hydroseeding the highest water flow was measured, but in relation to total precipitation only 0.5 % respectively 0.4 % of total precipitation. The soil losses for both techniques were between 29 and 44 kg ha-1, an amount that is neglectable. However, again the technique with straw mat performed much better in comparison, with surface runoff of less than 0.2 % of total precipitation and soil losses of 4 kg ha-1.

Water flow and soil losses are not only a result from total precipitation. Both the intensity of the raining event and the kinetic energy from the raindrops reaching the soil surface are responsible for erosion. Therefore, a direct comparison of all assessed application techniques between years is not possible. However, Figure 8 gives a general view of surface runoff caused by all compared application techniques from 1999 to 2001, referring to 500 mm precipitation. Using cheap application techniques like hand sowing, cover crop or nursery grass as well as hydroseeding, surface runoff from 28-58 l m- ² was measured. Only the additional protection of soil surface was able to cause a clear reduction to a surface runoff from 2-5 l m-².

Soil Erosion and Surface Runoff on Slopes in Mountain Environment

Depending on Application Technique and Seed Mixture – A Case-Study 207

Fig. 8. Surface runoff referring to 500 mm precipitation, comparison of all sites (1999-2001) A comparable proportion between soil losses and application techniques referring to 500 mm precipitation is visible in Figure 9. Corresponding to the climatic conditions during the investigation periods, the use of cheap and simple application techniques caused soil losses between 890 and 4,230 kg ha-1. The expensive additional cover with the straw mat was able

to reduce soil losses to an irrelevant amount of 11 to 46 kg ha-1.

Photo 6. Vegetation cover on the plot with the technique Hydroseed a year after setup (2002), the fine-grained material was washed out

Photo 7. Vegetation cover on the plot with the technique Hydroseed with straw mat a year after setup (2002), no soil losses was visible

Photo 6. Vegetation cover on the plot with the technique Hydroseed a year after setup

Photo 7. Vegetation cover on the plot with the technique Hydroseed with straw mat a year

(2002), the fine-grained material was washed out

after setup (2002), no soil losses was visible

Fig. 8. Surface runoff referring to 500 mm precipitation, comparison of all sites (1999-2001)

A comparable proportion between soil losses and application techniques referring to 500 mm precipitation is visible in Figure 9. Corresponding to the climatic conditions during the investigation periods, the use of cheap and simple application techniques caused soil losses between 890 and 4,230 kg ha-1. The expensive additional cover with the straw mat was able to reduce soil losses to an irrelevant amount of 11 to 46 kg ha-1.

Soil Erosion and Surface Runoff on Slopes in Mountain Environment

discussed.

restoration.

restoration.

Depending on Application Technique and Seed Mixture – A Case-Study 209

(Urbanska & Schütz 1986). Our assessment on vegetation cover of the plots showed, that under average conditions of high altitudes this minimum cover can be reached the second vegetation period at the earliest. This requires application techniques with additional protection of soil surface for the first vegetation period. From an economic point of view, restoration companies will always try to reach minimum requirements with a minimum of costs. Therefore it is important to give clear answers and stipulations for successful application techniques under average conditions. It is evident that a direct comparison between trials and years is not possible. Hence only clear differences or correlations are

With our first trial 1999, we also wanted to measure the influence of different seed mixtures on erosion. Due to the faster germination and early growth of commercial varieties, an increase of surface runoff and soil losses the weeks after sowing was expected for indigenous seed mixtures. However, the harsh conditions in high altitudes (low soil and air temperature, short vegetation period, frequent frost) are causing environmental stress to the vegetation, reducing the competitiveness of commercial forage grasses and herbs and neutralizing their greater productivity (Jones et al. 1989) Therefore, results obtained during the investigation period did not show substantial differences between seed mixtures on erosion processes during the first weeks after

The use of cover crops and in recent time also nursery grasses as additional protection against erosion is often used for restoration activities. Due to positive, longstanding experiences of restoration companies, those techniques were compared to normal hand sowing. Again we noticed that the admixture of fast growing components did not have positive influence on surface runoff and soil erosion. Compared to normal hand seeding, the reduction was poor. Once again, the environmental stress compensated the capability of fast early growth, reducing the positive effects towards zero. Results obtained clearly showed that the use of cover crops and nursery grasses did not have positive influence in view of a necessary reduction of surface runoff and soil losses during the first weeks after

Hydroseeding is described as one of the best application techniques for steep slopes with good properties in order to prevent erosion. To our surprise, the comparison of hydroseeding to hand sowing plus cover crop showed comparable results. The hydroseeding was carried out by a professional restoration company. Therefore, conditions close to practice can be assumed. One hour after application, we were faced with a raining event of two hours with a precipitation of app. 15 mm. This could have caused some wash out of not yet stabilized gluten, reducing the effect of building a protective layer on soil surface. Even if we take this possible problem into account, results obtained at least indicate a big risk in using this application technique without additional protection of soil surface. Depending on soil physical properties, climate and altitude, varying characteristics of runoff, infiltration and erosion can be expected (Markart & Kohl 1995). Especially in high altitudes, the main goal behind the choice of a certain application method has to be a reduction of surface runoff and soil erosion to an acceptable degree. A comparison of all used application techniques during our assessments shows clear results. Only an additional cover of soil surface is able to reduce surface runoff and soil losses to an acceptable degree. For our trials in 1999 and 2001-2002 we used a straw mat. But there are a lot of different techniques available that guarantee a sufficient protection of soil surface. Straw mulching,

Fig. 9. Soil losses referring to 500 mm precipitation, comparison of all sites (1999-2001)
