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Chapter 2
Climate and agro-ecological zones


Figure 1 shows the location of the nine provinces of South Africa, the main cities and towns, national roads and rivers and Table 1 shows the area.

Rainfall

The average annual rainfall, illustrated in Figure 2, shows a rapid decline from east (> 800 mm) to west (< 200 mm). More than 60 percent of the country receives less than 600 mm per annum, and approximately one fifth of the country receives less than 200 mm per annum. The southern coastal region of the Western Cape Province receives rainfall throughout the year, while the rest of the province gets its rainfall in winter. The remainder of the country is classified as summer rainfall area.

FIGURE 1
Orientation

TABLE 1
Areas of the provinces of South Africa

Province

Area (‘000 ha)

Percent

Eastern Cape

16 987

13.9

Free State

12 980

10.6

Gauteng

1 699

1.4

Kwazulu-Natal

9 231

7.6

Limpopo

12 282

10.1

Mpumalanga

7 937

6.5

North West

11 616

9.5

Northern Cape

36 274

29.7

Western Cape

12 951

10.6

Total

121 957

100

Source: ARC-ISCW, 2004.

FIGURE 2
Average annual rainfall


FIGURE 3
Aridity zones

Aridity Zones

According to the UNCCD index for defining dry lands, 80 percent of South Africa is semi-arid to arid, and only 18 percent is dry sub-humid to humid (Figure 3).

Soils

Soil surveys have a long history in South Africa. Natural land type surveys, conducted by the land survey staff of the Agricultural Research Institute for Soil, Climate and Water (ARC-ISCW) since the early seventies, are the source of information of generalized soil maps of the country. Figure 4 represents a simplified baseline of soils of South Africa and the legend is explained in Table 2.

More than a third of the country’s soils are shallow with minimal development. South African cultivated soils are generally very low in organic matter and are susceptible to wind erosion. They are also susceptible to acidification through cultivation and nitrogen fertilization and a liming strategy is indicated under normal cultivation practices. This is particularly true for leached soils in higher rainfall areas.

FIGURE 4
Generalized soil patterns

Natural soils across the whole country are low in bio-available phosphorus (60 percent less than 10 mg/kg), zinc (< 3 mg/kg) and copper (< 2 mg/kg) (ARC-ISCW, 2004).

The agricultural regions

The main farming systems are shown in Figures 6 to 10 (Agricultural Survey 1993, as reported in Agricultural Statistics, 2004). They correspond closely to the aridity zones in Figure 3.

The Free State, North West and Mpumalanga highveld can be considered collectively as South Africa’s "bread basket". Maize is the dominant field crop in all three provinces, followed by wheat (Free State), sunflowers, dry beans, grain sorghum and groundnuts (Free State and North West). In Mpumalanga province intensive crop farming under irrigation is practiced along lower river basins in the Lowveld, notably along the Komati and Crocodile rivers.

TABLE 2
Soil characteristics

Red-yellow well drained soils generally lacking a strong texture contrast

Ferralsols (FR)

Red and yellow soils with a humic horizon

Acrisols (AC)

Red and yellow, massive or weakly structured soils with low to medium base status

Cambisols (CM)

Red, massive or weakly structured soils with high base status

Soils with a plinthic catena

Plinthosols1 (PT1)

Red, yellow and greyish soils with low to medium base status

Plinthosols2 (PT2)

Red, yellow and greyish soils with high base status

Soils with a strong texture contrast

Luvisols1 (LV1)

Soils with a marked clay accumulation, strongly structured and a reddish colour

Luvisols2 (LV2)

Soils with a marked clay accumulation, strongly structured and a non-reddish colour.


In addition one or more of vertic, melanic and plinthic soils may be present

Well structured soils generally with a high clay content

Vertisols (VR)

Dark coloured, strongly structured soils dominated by cracking and swelling clays (vertic soils). In addition, one or more of melanic and red structured soils may be present

Phaezems/Kastanozems (PH/KS)

Soils with dark coloured, well structured topsoil with high base status (melanic soils).


In addition, one or more of vertic and red structured soils may be present

Nitisols (NT)

Deep, well drained, dark reddish soils having a pronounced shiny, strong blocky structure (nutty), usually fine (red structured soils). In addition, one or more of vertic and melanic soils may be present

Soils with limited pedological development

Leptosols1 (LP1)

Soils with minimal development, usually shallow on hard or weathering rock, with or without intermittent diverse soils. Lime rare or absent in the landscape

Leptosols2 (LP2)

Soils with minimal development, usually shallow on hard or weathering rock, with or without intermittent diverse soils. Lime generally present in part or most of the landscape

Fluvisols (FL)

Soils with negligible to weak profile development, usually occurring on deep deposits

Sandy soils

Arenosols1 (AR1)

Red, excessively drained sandy soils with high base status - dunes are present

Arenosols2 (AR2)

Red and yellow, sandy well drained soils with high base status

Arenosols3 (AR3)

Greyish, sandy excessively drained soils

Strongly saline soils

Solonchaks (SC)

Strongly saline soils generally occurring in deep deposits on flat lands

Podzolic soils

Podzols (PZ)

Soils with a sandy texture, leached and with sub-surface accumulation of organic matter and aluminium with or without iron oxides, either deep or on hard or weathering rock

Rocky areas

Regosols (R)

Rock with limited soils


FIGURE 5
Agricultural regions


FIGURE 6
Field crops, land area


FIGURE 7
Number of farming units and average farm size

Irrigation farming is practiced in the Northern Cape, mostly along the lower Orange River basin. Low-yielding rainfed maize, sorghum and sunflowers are produced in the northeastern part of the province where average rainfall is slightly higher than in other parts.

In the Western Cape, cereals (mostly rainfed wheat in rotation with lupin, canola and/or sub-terranean clover) are grown mainly in the Rûens and Swartland sub regions.

Sugar cane (mostly rainfed) is the major crop in Kwazulu-Natal. It is cultivated along the Indian Ocean seaboard and the Midlands region. Soils vary from grey and red sands on the coastal dunes, to weakly weathered soils in the coastal hinterland (South African Sugar Experiment Station, 1999). Summer grain crops are grown at higher altitudes predominantly in the Winterton/Bergville area of northern Kwazulu-Natal. Soil acidity and aluminium toxicity are a problem. This requires specialized amelioration strategies to ensure optimum utilization of the soil potential.

The Western Cape is well known for its vineyards, wines and deciduous fruits. Vines and deciduous fruits are cultivated in protected valleys where soil, terrain and irrigation possibilities permit. In the Northern Cape vines, table grapes (for export and domestic consumption), fresh and dried fruits, wheat, maize and cotton to a lesser extent are cultivated under irrigation. In Limpopo, intensively irrigated subtropical fruit and vegetable production are practiced in the eastern Lowveld. In Mpumalanga province, citrus, subtropical fruits and nuts and sugar cane are the dominant crops under irrigation.

FIGURE 8
Mixed farming, land area

Mixed farming is particularly important in the Northern Cape Province (Figure 9). Gauteng province falls within the summer grain area but is classified as "diverse" because of its geographical location around the large metropolitan complexes of Pretoria, Johannesburg, the Vaal Triangle and East Rand. The emphasis in this province is on mixed and vegetable farming.

The Northern Cape is by far the largest province in South Africa and accounts for 36 percent of its total land area. Almost the entire province falls within the arid zone classification. Very extensive cattle and sheep farming predominate (Figure 10). Range farming predominates also in the Eastern Cape; the greater part of this subsistence region (previously Transkei/Ciskei Homelands) has a high agricultural potential but is underdeveloped. The typically dry savanna of Limpopo Province is devoted to cattle farming. Only about three percent of the animal production area is fertilized. Extensive range land receives little or no fertilizer.

FIGURE 9
Animal production, land area

Mpumalanga east of the Drakensberg escarpment favours forestry along the escarpment (Figure 11). There is an important area of forest also in Kwazulu-Natal. Forests receive little or no fertilizer.

FIGURE 10
Forestry, land area


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