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A comparative assessment of rain erosion hazard of five land use types and management practices in Mhong Chun Yen Village, Northern Thailand using soil surface micro-topographic features of erosion.

Introduction

With increasing human population and a decreasing agricultural land mass per capita, the need to increase productivity per unit land area has become more urgent than ever before. In Mhong Chun Yen Village, Northern Thailand, this need has reached a most challenging stage due to its hilly topography, heavy tropical precipitations and, often, coupled with wrong farm management practices, a combination which has rendered the hill farms very vulnerable to erosion by rain. At farm level, soil erosion causes crop yields to drop (Thao, 2001), and only soil conservation can improve productivity on such hill farms (Ahmad, 1991).

In order to provide adequate information for rural extension about soil conservation, the erosion hazard itself has to be fully appreciated through appropriate assessment methods. Moody and Cong (2008) have stated that erosion hazard should be based on a consideration of slope and observed erosion. Evaluating erosion hazard through the conventional method of measuring soil loss (Wischmeier, 1975) is not only time consuming and expensive, often data are rare. Also, prediction models are insufficiently calibrated in most areas (Kunwar et al., 2002). Hence, there is a need for a more rapid, cheap and efficient alternative procedure for determining erosion hazard.

Without the need to determine soil loss in it [(ha.yr).sup.-1], a method that satisfies these conditions has been developed that can be used to measure rain erosion intensity and to compare cropping systems, land use practices and conservation systems for their resistance to erosion (Bergsma, 1992, 1997; Bergsma and Kwaad, 1992). Essentially, this method recognizes and uses seven features of soil surface micro-topography for erosion hazard evaluation; namely, Resistant or recently made clods, Eroding clods, Flow surfaces, Prerills, Rills, Depressions and Vegetal matter. Compared to conventional methods of measuring soil loss in erosion studies, this procedure can conveniently be applied on whatever important types of land use, such as annual and perennial crops, grassland, forest, orchard or plantation (de Bie, 2000).

In the present research, this method will be employed to assess and compare rain erosion hazard on five sites representing five different land use types (cropping systems) and management practices. The results would provide information for conservation advice aimed at sustainable agricultural production on the hill farms.

In order to know the soil types covering the study area, modal profile pits would be located, dug and described in accordance with standard procedure (FAO, 1997). Subsequently, the soils will be classified accordingly (Soil Survey Staff, 1998).

Materials and Methods

The erosion hazard assessment was carried out during the rainy season, on five sites that represented five different land use types and management practices in the farming communities of Mhong Chun Yen Village, about 7km from Ban Mae Malai, West of Mae Ping River, in the central part of Chiang Mai Province, Northern Thailand. It is situated within latitudes 19[degrees] [05.sup.1] to 19[degrees] [10.sup.1] N and longitudes 98[degrees] [51.sup.1] to 98[degrees] [53.sup.1] E.

The climate of Northern Thailand is monsoonal, and it is characterized by three distinct seasons, namely; the rainy season, the cool dry season and the hot dry season. The climatic data from Chiang Mai Meteorological Station show that the mean annual average rainfall in the area is about 1,200 mm [yr.sup.-1]. The soil moisture regime is ustic, although at higher elevations it can be udic (as per Soil Survey Staff, 1998). The soil temperature regime is iso- hyperthemic, with the mean monthly temperature ranging from 27[degrees]C in the wet season to 37[degrees]C in the dry season. Geologically, the area is underlain by marble derived from the Ordovician era. They are metamorphic rocks with white sugary texture (an equivalent of limestone), outcropping in many places. Sometimes bedding planes with streaks and bands of other mineral impurities such as Mica schists and quartzites are observed.

The land scope of the study area is hillland, with a mean ultitude of over 500m above sea level. The relief form is convexly dissected mesa. Table 1 shows the site specific information. Standard soil survey procedure was carried out (FAO, 1977) and consequently three soil types were identified for the whole study area (Soil Survey Staff, 1998).

Characterization of The Erosion Hazard:

To characterize the erosion hazard, the accumulated effect of erosion was observed as expressed by microtopographic erosion features formed over a previous rainy period. These specific features were used instead of the 'random roughness' of the eroded soil surface (Kunwar et al., 2002). The microtopographic features used for evaluating the rain erosion hazard were seven types as described by Bergsma (2002).

At each site a measuring tape of 2.5m long was stretched along the contour, so that surface flow features were met across the tape. The tape had alternately coloured intervals of 25cm. For each interval the dominant of the seven microtopographic features along the tape was determined. The record covered 50 intervals, following the same contour line. Thus each tape interval represented 2% of the area. Two repetitions of the feature record were made, in the contour direction, at one or two meters above or below the first observation line. The recording of the microtopographic erosion features has an accuracy of 4% in a feature percentage that is obtained from observation of 50 tape intervals (Bergsma, 1992).

Next, the percentage distribution of the seven features was determined. An indicator of erosion intensity was calculated as the 'percentage flow + two times the percentage prerill areas' (Bergsma, 1997, 1999).

Erosion Hazard Ranking of The Sites:

The indicator of erosion intensity was determined for each site on the last day of the observation period. With this information a relative ranking of the erosion hazard of the sites was then carried out.

Erosion Pins Recordings:

Also, the erosion processes were observed using erosion pins. After each erosive shower, the level of change of the microtopographic features was recorded using a mm rule. An erosion pin was carefully installed on each erosion feature before the first erosive shower and left on the feature throughout the observation period. The objective was to observe the surface level changes, that is, loss (erosion) or gain (deposition) of soil on each erosion feature as a measure of erosion hazard.

Results and Discussion

The percentage coverage and change in level of the features as observed through erosion pin readings on the last day of observation is shown in Table 2.

Identification of The Erosion Problems:

From Table 2 the erosion problems on each site can be identified, and this is a necessary step to take whenever effective control measures are needed to be put in place (Meyer et al., 1991). This step is facilitated by the fact that the erosion features have been found to correlate with the dominant processes of erosion. Eroding features are dominantly formed by splash, flow areas are formed by interrill erosion, while pre-rills and rills indicate the degree of rill erosion (Bergsma, 2008).

Hence on site 1 the erosion problems were identified as rill, interill and splash erosion. Another problem of this site is the steep slope (55%) (See Table 1). The erosion problems on site 2 were rill, interrill and splash erosion. Judging from the percent coverage of features splash erosion was the dominant problem, followed by interrill erosion. The problems on site 3 were rill, interrill and splash erosion. Although splash was the dominant problem here, the observed soil detachment by splash process was almost negligible (Table 2). This was probably because the energy of impact of the raindrops had been modified by the canopy of the trees, and the basal vegetal cover also intercepted the splash impact.

On site 4, the erosion problems were rill, interrill and splash. The splash and rill erosion were very comparable in areal coverage. Splash, interrill and rill erosion were the problems in site 5.

Ranking the erosion hazard of the sites:

Erosion hazard is based on a consideration of slope and observed erosion (Moody and long, 2008). The observed erosion has been summarized in Table2, while the slope details are shown in Table 1. Based on these, the erosion hazard has been ranked in categories ranging from 1 (lowest) to 5 (highest) (Table 2).

Comparing The Erosion Hazard of The Sites:

From Table 2, the erosion hazard of the sites can be compared. In a decreasing order of erosion hazard, the sites compared as follows: Site 4 > site 1 > site 2 > site 3 > site 5. In other words, the land use and management practices on site 5 showed the highest resistance to erosion, while the land use on site 4 was most vulnerable to erosion.

The reasons for these differences in erosion resistance of the sites may be briefly discussed below so as to proffer solutions and preventive measures, based on the work of Meyer et al., (1991).

The land use on site 4 had exposed most of the soil surface to the erosive forces of the rainstorms. Moreover, the wrong tillage practice of ploughing up and down, instead of across the slope, with heavy equipment had worsened the erosion hazard. Also, the continuous cultivation of cotton on the same land for that long period (20 years) had destroyed the soil structure leading to reduced infiltration and the sealing problem which together aggravated the erosion. The erosion problems in site 1 could be attributed to the fact that the land use and management practice had exposed most of the soil surface to erosive rainstorms. The slash and burn and the continuous cultivation for so long a period (20 years) had adversely affected the organic matter content and the structure of the soil, hence reducing the soil resistance to erosion.

The causes of the erosion problems in site 2 are similar to those of site 1, but resistance to erosion is higher in site 2 than that of site 1 probably because of the contour tillage across slope and the fertilizer application which encouraged growth of the crops to provide better surface cover. However, it was observed that if the fertilizer was applied earlier than the time it was done, it would have supported earlier growth of the crops to provide more cover. Land use on site 3 presented greater resistance to erosion than sites 4, 1, and 2, probably due to better surface cover provided by the basal grass and the fact that the canopy of the trees intercepted and reduced the soil detachment energy of the raindrops to a negligible level. The land use of site 5 showed the highest resistance to erosion probably because of the dense basal grass cover and the surface roughness provided by the surface gravels. Also the canopies of the trees of the orchard had provided additional protective cover against the raindrop impact.

Summary, Conclusion And Recommendations:

Resistance to erosion varied among the different land use types and management practices. The land use types and management practices that exposed the soil more to the erosive forces of rainstorms exhibited greater erosion hazard. Also wrong tillage practices such as ploughing up and down, instead of across slope encouraged greater erodibility.

Therefore it is recommended that ground cover be improved. To achieve this purpose the recommended control practices must include adequate presence or establishment of vegetation and/or mulches to protect soil surface during seasons of major rainstorms. Where necessary, fertilizers should be applied early enough to encourage early growth of crops to provide the much needed timely cover. An additional control measure is to make the surface rough enough to encourage ponding. Also, there should be runoff routing structures to reduce overland flow velocities. Only contour cultivation should be practised on sloping lands. The effective approaches to the erosion hazard that is due to steep slopes are first, preventing soil detachment and secondly, controlling runoff, by ensuring adequate presence of vegetation or mulches to protect the soil surface.

References

Ahmad, N., 1991. Soil Management on Hillslopes in the Humid Tropoics. In: Moldenhauer, W.C. et al., (eds.). Development of Conservation Farming On Hillslopes. "In cooperation with World Association of Soil and Water Conservation, Chinese Soil and Water Conservation Society." National Chun- Hsing University (and) National Science Council, R.O.C." pp: 10, 1-111.

Bergsma, E. and F.J.P. M. Kwaad, 1992. Rain erosion hazard evaluated from soil surface features as well as from soil loss, p: 25-35 in: People Protecting Their Land. Proceedings 7th Conference, International Soil Conservation Organization (ISCO) Conference, under the auspices of the Department of Conservation and Land Management, Sydney, Australia.

Bergsma, E., 1997. Rain erosion hazard evaluation by soil surface micro-topographic features--A case of the soil loss plots at Chiang Dao experiment station, Northern Thailand, in: "Land Husbandry--the International Journal of Soil and Water Conservation", 2(1): 45-58.

Bergsma, E., 2008. Erosion by Rain: its subprocesses and diagnostic micro-topographic features. International Institute for Geo-Information Science and Earth Observation (ITC), Enschede, The Netherlands.

Bergsma. E., 1992. Features of soil surface micro-topography for erosion hazard evaluation, p:15-26.

de Bie, C.A.J.M., 2000. Comparative performance analysis of agro- ecosystems. Doctoral Thesis, Wageningen University, The Netherlands. Chapter 11: Soil erosion indicators for maize - based agro- ecosystems in Kenya.

FAO., 1997. Guidelines for Soil Profile Description. 2nd Edition. Rome: FAO.

Hurni, H. and Kebede, Tato (eds.), 1992. Erosion, conservation and small- scale farming, selection of papers presented at the 6th International Soil Conservation Organization (ISCO) conference, Ethiopia and Kenya, 1989.

Kunwar, L.B., E. Bergsma and D.P. Shrestha, 2002. Micro-topographic Erosion Features as Indicator of Erosion Hazard for Conservation advice. Proceedings of the 12th ISCO Conference, Beijing, pp: 173-178.

Meyer, et al., 1991. Use of Basic Erosion Principles to Identify Effective Erosion Control Practices. In: Mouldenhauer, W.C., et al., (eds.) Development of Conservation Farming on Hillslopes. Soil and Water Conservation Society, Ankey, Iowa, USA.

Moody, P.N. and P.T. Cong, 2008. Soil Constraints and Management Package (SCAMP): GUIDELINES FOR SUSTAINABLE MANAGEMENT OF TROPICAL UPLAND SOILS. Australian Centre for International Agricultural Research, Canberra ACT 2601, Australia.

Soil Survey Staff. 1998. Keys to Soil Taxonomy. USDA Natural Resources Conservation Service. Washington, D.C.

Tran Dinh Thao, 2001. On-site Costs and Benefits of Soil Conservation in Mountainous Regions of Northern Vietnam. Economy and Environment Program for Southeast Asia (EEPSEA).

Wischmeier, W.H., 1975. Estimating the soil loss equation's cover and management factor for undisturbed areas. In: Present and prospective technology for predicting sediment yields and sources. ARS- S-40. USDA- Agricultural Research Service, pp: 118-124.

(1) M.A. Nwachokor and (2) E. Bergsma

(1) Department of Agriculture, Faculty of Basic and Applied Sciences, Benson Idahosa University, P. M.B. 1100, Benin City, Edo State, Nigeria.

(2) Formerly of The Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. BOX 6, Enschede, The Netherlands.

Corresponding Author: M.A. Nwachokor, P.O. Box 5911, Airport Road, Benin City, Edo State, Nigeria. Tel: No. +2348077116640, +2348039282112

E-mail: andrewnwachokor@yahoo.com
Table 1: Site Specific Information

Site    Slope     Land use and        Soil Name            Remark
 No.     (%)       management      (Soil Taxonomy)
                    practice

(1)     55      Arable:            Petrocalcic        Land has
                Maize, melon;      Calciustoll,       been
                slash and burn,    fine loamy,        cultivated
                tillage with       carbonatic.        for twenty
                hand hoes,                            Years now.
                weeding first
                with hand hoes
                and later with
                herbicide;
                stubble
                mulching.

(2)     19      Like site 1,       -do-               -do-
                but Ploughing
                is by 4-wheel                         Surface
                tractor up and                        sealing.
                down slope;
                Plus fertilizer
                use.

(2)     21      Agroforestry:      Pachic             Old terrace,
                teak, banana,      Argustoll fine     Grass cover
                lemon grass;       loamy, mixed,      (65%),
                Grazing            nonacid.           earthworm
                                                      caste.

(4)     20      Orchad:            Typic              Land
                longan (1 yr       Kandiustalf,       cultivated to
                old), inter-       clayey, mixed,     cotton
                planted with       nonacid            for 13 yr.
                ginger;                               until 2007.
                mulching,                             &
                fertilizer use,                       Surface
                ploughing with                        sealing.
                4-wheel tractor
                up and down
                slope.

(5)     20      Orchard:           -do-               Grass
                longan (5 yr                          cover (70%),
                old), litchi,                         Earthworm
                mango;                                caste,
                herbicide use,                        Surface
                pesticide use.                        gravel (5%),
                                                      Green
                                                      algae

Table 2: Summary of pin reading showing change in level and percent
coverage of features on the last observation day.

                                                         Features
Site   Res       Ero       Flo       Pre       Ril       Dep

1.     (a)       2         36        34        8         20
       (b)       -5        -170      +6        -32       -131
       (c)       -2.5      -4.7      +0.8      -4.9      -6.6

2.     (a)       6         52        26        6         10
       (b)       -32       -83       +52       -16       -53
       (c)       -5.3      -1.6      +2.0      -2.7      -5.3

3.     (a)       /         58        22        2         6
       (b)       /         -25       +23       0         +25
       (c)       /         -0.4      +1.1      0         +4.2

4.     (a)       /         36        26        12        26
       (b)       /         -40       -30       -22       -88
       (c)       /         -1.1      -1.2      -1.8      -3.4

5.     (a)       /         64        28        4         /
       (b)       /         +8        -20       -8        /
       (c)       /         +0.1      -0.7      -2.0      /

                 Veg Net change in level of
Site   Res       all the feature types (mm)

1.     (a)       /        /        -332
       (b)       /        /
       (c)       /        /

2.     (a)       /        /        -132
       (b)       /        /
       (c)       /        /

3.     (a)       /        12       +23
       (b)       /        0
       (c)       /        0

4.     (a)       /        /        -180
       (b)       /        /
       (c)       /        /

5.     (a)       /        4        -20
       (b)       /        0
       (c)       /        0

Legend:

(a) = percent coverage of a feature (%)

(b) = total change in level of a feature (mm)

(c) = average change in level of a feature (mm)

+ = deposition (soil gain)

- = erosion (soil loss)

/ = feature not present.
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Title Annotation:Original Articles
Author:Nwachokor, M.A.; Bergsma, E.
Publication:American-Eurasian Journal of Sustainable Agriculture
Article Type:Report
Geographic Code:9THAI
Date:Jul 1, 2011
Words:2851
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