SOILS AND AGRICULTURAL POTENTIAL FOR THE PROPOSED P166 SERVITUDE, MBOMBELA, MPUMALANGA PROVINCE

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1 REPORT On contract research for Royal Haskoning DHV SOILS AND AGRICULTURAL POTENTIAL FOR THE PROPOSED P166 SERVITUDE, MBOMBELA, MPUMALANGA PROVINCE By F.T. Seabi (Pr. Nat. Sci /11) & D.G. Paterson (Pr. Nat. Sci /04) February 2014 Report No. GW/A/2014/10 ARC-Institute for Soil, Climate and Water, Private Bag X79, Pretoria 0001, South Africa Tel (012) Fax (012)

2 Declaration: I declare that the author of this study is a qualified, registered natural scientist (soil science), is independent of any of the parties involved and has no other conflicting interests. D.G. Paterson February

3 CONTENTS Page 1 Introduction and Background 4 2 Study Area Terrain Climate Geology 7 3 Methodology 8 4 Soils Agricultural Potential Erodibility 12 5 Impacts and Recommendations Fatal Flaws Agricultural Land Alternatives P166 Servitude Conclusions 15 References Appendix: Soil Maps 3

4 1 INTRODUCTION AND BACKGROUND The ARC-Institute for Soil, Climate and Water (ARC-ISCW) was requested by Royal Haskoning DHV to carry out a study regarding the proposed P166 route near Mbombela (Nelspruit). The aim of the report is to obtain supply information on the soils occurring, as well as their properties, characteristics and agricultural potential. 2 STUDY AREA The study area, comprising a servitude length/distance of approximately 32 kilometers, is located near Mbombela (Nelspruit), Mpumalanga. The route (with its alternatives) runs roughly parallel to the existing R40 road and crosses the N4 national road and on the western side of Mbombela city. The route also crosses the Crocodile River and Samora Machel Drive. Three alternative routes (namely White River Alternative, Phumlani 2 Alternative and Maggiesdal Alternative) and the main P166 route were studied for soils and agricultural potential. The main route and the alternatives are shown in Figure 1. The prevailing land use ranges from agricultural activities of local farms, residents buildings in occasions and informal settlements. The northern segments comprise intensive agriculture with irrigated macadamia orchards widespread. Localized informal settlements were found in this area. 4

5 2.1 Terrain The terrain of the entire route is comprised of undulating terrain with varying slopes of approximately 4-8%. The altitude varies from m in the northern segments, m in the middle segment and m in the southern segments. 5

6 Figure 1 Study area 6

7 2.2 Climate Climate data was obtained from the national Land Type Survey (Koch & Schoeman, 1989). The climate of the area can be described as typical of the southern Lowveld, with warm to hot, moist to wet summers and dry, mild to cool winters. The main climatic parameters are given in Table 1. On average, mm, or 83% of the annual average rainfall of mm falls in the summer growing season (October to March). Frost is extremely rare. The extreme maximum temperature is 41.7 o C and the extreme minimum 2.0 o C. Table 1 Month Climate data for Mbombela area Rainfall Min. Temp Max. (mm) ( o C) Temp ( o C) Average frost dates Jan Start date: Feb End date: Mar Days with frost: Apr May Jun Jul Heat units (hrs > 10 o C) Aug Summer Sep (Oct-Mar): 2338 Oct Nov Winter Dec (Apr-Sept): 1371 Year mm 20.0 o C (Average) 2.3 Geology The area is underlain mainly by gneiss and migmatite of the Nelspruit Granite Suite (Geological Survey, 1986). 7

8 3 METHODOLOGY The soils occurring were investigated by means of a soil auger, with an average point spacing of 200 to 300 m along the servitude path, to a maximum depth of mm (or shallower, if a restricting layer, such as rock, was encountered). The soils were described and classified according to the South African soil classification system (Soil Classification Working Group, 1991). Similar soils were grouped into map segment classes, and the distribution of these mapping segments is shown on the map in the Appendix. The mapping segments were distinguished by different colour codes for descriptive purposes, as shown in the legend (Table 2). Wetland distribution information in the study area was acquired from the Water Research Commission (Nel et. al., 2011) and is depicted in blue on the maps provided. 4 SOILS The main characteristics of each of the soil mapping segments are given in Table 2 below. Soil samples were collected for analysis at six localities. The analysis results are shown in Table 3. 8

9 Table 2 Soil legend Class Dominant Subdominant Soil Form(s) Soil Form(s) Depth (mm) Soil Characteristics 1 Hutton Clovelly Reddish brown, structureless, loamy sand topsoil on reddishbrown to red, weakly structured, loamy sand to clay loam subsoil, often gravelly. Underlying material is weathered rock. Greyish to brown, structureless, loamy sand topsoil on grey*, 2 Fernwood Westleigh, 750- structureless, loamy sand to sandy loam subsoil, often gravelly. Kroonstad Underlying material is weathered rock, mottled soft plinthic or clayey material with signs of wetness Greyish to brown, structureless, loamy sand topsoil on grey*, 3 Fernwood Rock structureless, loamy sand to sandy loam subsoil, often gravelly Underlying material is weathered rock, mottled soft plinthic or clayey material with signs of wetness. Rock outcrops occur in places. Greyish to reddish brown, structureless, loamy sand topsoil 4 Mispah Glenrosa overlying hard or weathered rock. Rock outcrops occur in places throughout the mapping unit. 5 Rock - - Rock boulders are observable within the area. Rock outcrops are widespread. 6 Inaccessible Agric. Potential Moderate to high Low to moderate Low to moderate 7 Built up None 8 Wetland - - Strong waterlogging hazard, with standing water in places. Zones of prolonged waterlogging conditions. None * Subsoils often appear yellowish or reddish in the moist state, but clearly become grey after drying out Low None 9

10 Table 3 Soil analytical results Sample point S1 S2 S3 S4 Soil Form Fw Hu Hu Fw Horizon A1 E A1 B1 A1 B1 A1 E Depth (mm) Co-ordinates S E 25 o o o o o o o o Sand Silt % Clay Na K cmol Ca kg Mg CEC ph (H 2O) Organic Carbon % P (Bray 1) mg kg

11 Sample point S5 S6 Soil Form Hu Hu Horizon A1 B1 A1 B1 Depth (mm) Co-ordinates S E 25 o o o o Sand Silt % Clay Na K cmol Ca kg Mg CEC ph (H 2O) Organic Carbon % P (Bray 1) mg kg

12 The analyses show the soil textures are light to slightly moderate (sandy clay to sandy clay loam), with the grey (Fernwood) soils having a much lower clay content than the red (Hutton) soils. The soils are mostly dystrophic (highly leached) with very low CEC values (indicating the low water-holding capacity of the soils and their sandy texture). Generally the ph values are low, indicating that the soils are slightly to moderately acidic. On average, the soils have very low P levels due to the acidity of the soils, which in turn causes P to be fixed in the soil and thus render it unavailable for plant uptake. In addition, most of the soils have not been previously cultivated which will also contribute to the low P levels. Organic carbon levels are low to moderate. 4.1 Agricultural Potential The soils have a generally light texture (loamy sand to sandy loam, clay content between 12 and 20%), with little or no structure. The only clay soils occur in the deeper layers of some of the profiles (Hutton). The main factor in determining agricultural potential is therefore the available rooting depth, as well as the colour. Where the soils are deeper (>750 mm), there is no limitation to water infiltration, while the red soils indicate a higher degree of natural fertility than the greyer soils, where iron, organic matter and other chemical elements have been removed. The proposed servitude and its alternative routes cross over wetland areas in several locations, more especially on the southern portion of the servitude (Part B soil map). The high potential Hutton soils dominate the northernmost portion of the servitude (Part A soil map), whereas the middle and southern portions are dominated by shallower soils 12

13 (Glenrosa and Mispah) and the low potential Fernwood soils (Part B soil map). Rock outcrops also occur in these areas. 4.2 Erodibility The soils in the area, due largely to their kaolinitic mineralogy, are inherently stable soils not prone to erosion. However, the slopes in the study area (typical of the wider surrounding landscape) mean that if the soil surface is exposed by means of removal of vegetation, water erosion can occur. The soils need to be protected by means of culverts, terraces etc and should be kept un-vegetated for as short a time as possible. 5 IMPACTS AND RECOMMENDATIONS 5.1 Fatal Flaws The P166 main route has no fatal flaws (based on soils occurring). It is only in places where the route crosses wetland areas (as depicted by the blue zones on the various soil maps) that pose a potential fatal flaw. The wetlands occurring are sensitive environmental areas that need to remain undisturbed and, if necessary, be protected. Where the road crosses or infringes on any wetland, care should be taken to avoid any disturbance or excess contribution to the sediment load in the stream. This should be planned in conjunction with the road engineers. 5.2 Agricultural Land The northern portion of the servitude (Part A soil map: White River alternative and P166_line) is comprised of high potential soils of the Hutton soil form. These soils are highly valued in the agricultural sector and their loss is unfavorable to the production capacity of the country. Intensive agricultural production in this area is widespread. A 13

14 portion of Maggiesdal Alternative is also comprised of these high potential soils, but less dominant. It is therefore expected that the development of the P166 route will have a permanent impact on these soils with regard to loss of production area and possible soil erosion inducement. 5.3 Alternatives Maggiesdal Alternative This route has a larger proportion of moderate to high potential soils than the existing servitude, so is not recommended. Phumlani 2 Alternative This route has slightly less moderate to high potential soils than the existing servitude, so would be recommended. White River Alternative This route has significantly more moderate to high potential soils, coupled with intensive agriculture, than the existing servitude, so would definitely not be recommended. 5.4 P166 Servitude The P166 route on the south of the N4 route is comprised mainly of low agricultural potential soils and therefore has less impact on the loss of production land. On the northern side of the N4, the P166 route immediately passes through cultivated farm lands (which are a concern on the bases of loss of agricultural land). The rest of the path up to the starting point of the White River alternative is comprised of shallow soil 14

15 depth to rocky areas of very low agricultural potential and therefore low impact on production land. 5.5 Conclusions Due to the sloping topography across most of the area, great care must be taken to ensure that soil erosion does not take place and this applies to all the alternative routes (White River, Phumlani and Maggiesdal alternatives) and the main route (P166 route). Soil conservation measures must be put in place in conjunction with engineering specialists in order to ensure that associated problems do not occur. Where the routes cross the wetlands, mitigation procedures (such as building of bridges) must be put in place in order to make sure that the natural state of the wetlands is preserved. Consultation with construction engineers is necessary in this regard. Based on an extensive occurrence of wetlands in the study area, it is recommended that further study/research be undertaken to fully comprehend their distribution and characteristics. Should the project receive approval, consultation with engineers with regard to the protection of these wetlands is imperative. 15

16 REFERENCES Geological Survey, : scale geological map 2530 Barberton. Council for Geoscience, Pretoria. Koch, F.G.L. & Schoeman, J.L., Climate data. In: Land types of the map 2530 Barberton. Mem. Agric. Nat. Res. S. Afr. No 13. Dept. Agric & Water Supply, Pretoria. MacVicar, C.N., de Villiers, J.M., Loxton, R.F, Verster, E., Lambrechts, J.J.N., Merryweather, F.R., le Roux, J., van Rooyen, T.H. & Harmse, H.J. von M., Soil classification. A binomial system for South Africa. ARC-Institute for Soil, Climate & Water, Pretoria. Nel, J.L., Driver, A., Strydom, W.F., Maherry, A., Petersen, C., Hill, L., Roux, D.J. Nienaber, S., Van Deventer, H., Swartz, E. and Smith-Adao, L.B. (2011) Atlas of freshwater ecosystem priority areas in South Africa. WRC Report No. TT 500/11. Water Research Commission, Pretoria, South Africa. 16

17 APPENDIX: Soil Maps 17

18 Prairie Hendrina 18

19 19

20 20

SOIL SURVEY FOR PROPOSED WET ASH DISPOSAL FACILITY, HENDRINA POWER STATION, MPUMALANGA PROVINCE

REPORT for Lidwala Environmental and Planning Servives by the INSTITUTE FOR SOIL CLIMATE AND WATER AGRICULTURAL RESEARCH COUNCIL SOIL SURVEY FOR PROPOSED WET ASH DISPOSAL FACILITY, HENDRINA POWER STATION,