Your Site: Biome, Veld Type and Rainfall

#The number that reorganises a farming year

Sourveld supplies adequate nutrition for roughly five to seven months of the year, and the same source notes that "in some conditions, sourveld only supply enough nutrients for three months of the year" (Voermol). Sweetveld can be grazed year-round without loss of condition.

Two farms, both South African, both with grass standing in the camps in July. On one, that grass keeps a cow in condition. On the other, she eats her fill every day and still loses weight, because the feed has bulk and no protein. No paddock design, breed choice or grazing app changes which farm you are on. Only knowing which farm you are on changes what you do about it.

#Six biomes, six different animals

South Africa's biome map follows Mucina & Rutherford, The Vegetation of South Africa, Lesotho and Swaziland (SANBI Strelitzia 19, 2006) — the dataset DALRRD used as its zones when it rebuilt the grazing capacity map. Grassland is roughly 28% of the national land surface, Savanna about 32.5%, Nama-Karoo about 19.5% (Kirkman et al.).

The department publishes a mean capacity per biome: Grassland 6 ha/LSU, Savanna 12, Nama-Karoo 25 (DALRRD), inside a national polygon range of 1.5 to 140. A biome mean is a starting assumption, not your farm.

#Sour, sweet and mixed — the line sits at about 650 mm

This is the most important grazing concept in South Africa, and it is not about how much grass you grow. It is about what that grass is worth once it stops growing.

• Sweetveld stays palatable and nutritious at maturity. It goes with lower rainfall, more fertile and less-leached soils, and milder winters.
• Sourveld is palatable only while actively growing. It goes with rainfall above roughly 650 mm, acidic leached soils and cold winters. Mature Themeda triandra and Tristachya leucothrix become unpalatable and protein-poor once the growing season ends (Voermol; the peer-reviewed distribution analysis behind it is Ellery, Scholes & Mentis, AJRFS 12(1), 1995).
• Mixed veld sits in the transition, roughly 500–600 mm.

The mechanism is leaching: higher rainfall on old, acidic soils strips bases and leaves a sward that grows fast, matures quickly and locks its nitrogen into stem as it dries off. Productive summer, worthless winter standing crop.

You will see a tidier secondary split quoted — sour-mixed at six to eight usable months, sweet-mixed at nine to eleven. That split could not be traced to any source when this course's research was checked. Treat the gradient as real and those month figures as unsourced. What is sourced: sourveld's five to seven months, the "in some conditions only three", and sweetveld's year-round grazing without loss of condition.

#The rule that follows: which problem you actually have

On sourveld you plan a fodder flow. On sweetveld you plan a drought reserve. On honest mixed veld, both.

Sourveld's problem is quality within the year: the gap is coming, you know roughly when, and bridging it is an annual job. Sweetveld's problem is quantity between years: the feed keeps its value, so what hurts you is the year the rain does not arrive.

Work the sourveld version once. Take a 120 ha Highveld block on Grassland Biome veld at the departmental mean of 6 ha/LSU.

• Full-year capacity: 120 ÷ 6 = 20 LSU
• Grazing days available: 120 ÷ 6 × 365 = 7 300 LSU-grazing-days (Elsenburg's formula)

Now apply the veld type. Twenty LSU is a bulk figure: the capacity map counts the dry standing hay in your winter camps as feed, because it is feed for maintenance. What it does not count is protein. If your sourveld supplies adequate nutrition for six of the twelve months, then for roughly 180 days × 20 LSU = 3 600 LSU-days you are carrying animals on a full stomach that will not meet their requirement on its own.

That 3 600 is your fodder-flow budget, and Module 6 turns it into a plan. It is not a shortage of grass — it is a shortage of protein inside enough grass, and the two need opposite answers. A grass shortage needs more hectares or fewer animals. A protein gap needs a reserve camp, a planted block, crop residues or a bought supplement. Diagnose the wrong one and you buy the wrong solution for years.

#Finding your own polygon

Nobody can classify your farm from a lesson. Here is where the published answers live.

Your vegetation unit. The Mucina & Rutherford map divides the country into named units, not just biomes — Soweto Highveld Grassland, Rand Highveld Grassland, Vaal-Vet Sandy Grassland. Pull the unit polygon your farm coordinates fall in, from SANBI's vegetation map layer. The unit name gives you the expected dominant species list, which a veld condition assessment scores you against in Module 3.

Your grazing capacity value. The long-term capacity layer published under Regulation 10 of the Conservation of Agricultural Resources Act 43 of 1983, and described in the departmental background document. Get the polygon value for your own farm, not the provincial or biome mean.

Be careful with provincial figures you meet second-hand. A commonly repeated summary puts Gauteng's polygons at about 4 to 20 ha/LSU around a provincial mean near 6.8 — but when this course's research went back to the departmental document, it contained no provincial table at all, only the biome means and the national polygon range. Treat 4–20 as unconfirmed, and pull your own polygon rather than argue from a province.

Your soil forms come from the national land type survey; your rainfall from a Weather Service station record and, from this year, your own gauge read daily.

#Rainfall variability, not rainfall average

One number decides stocking policy, and it is not what your rainfall averages. It is how far it moves.

Two farms both average 500 mm. The first ranges from 420 to 590 mm; the second from 180 to 900 mm. They are not the same business. The first can stock close to capacity and manage the shortfall. The second must carry a permanent reserve, because in the bad year the veld is simply not there and no plan written against the average will save it.

The statistic that captures this is the coefficient of variation — the standard deviation of annual rainfall as a percentage of the mean. A low CV means a stocking rate you can hold; a high CV means your safe rate is set by the dry tail, not the middle. Broadly, CV rises as mean rainfall falls here, which is why the arid west runs conservative rates and flexible numbers.

The honest gap: this course's research located no published set of CVs for South African rainfall stations, so no national table appears here and none should be invented. Compute your own — twenty or more years from your nearest long-record Weather Service station, mean, standard deviation, divide. One spreadsheet column, and it tells you more about how to stock than any grazing system will.

Before the next lesson, do the two lookups: your vegetation unit polygon and your grazing capacity polygon value, for your own farm boundary — not your district, not your province. Write your veld type beside them in one word. Everything that follows assumes you know those three things about your own ground.