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Cultivating Subtropical Crops: Coffee
| By goGreen | June 26, 2012 |  |
Temperature
The optimum temperature range for coffee in South Africa is 26 °C (mean maximum), 32 °C (absolute maximum) and 12 °C (mean minimum) 4 °C (absolute minimum). Although this crop can tolerate temperatures well outside this range, excessive temperature variation usually affects the crop and the coffee bush detrimentally. Coffee cannot tolerate frost and should be planted well above the frost line. The effect of frost can be minimised by planting on broad ridges and by mulching.
Altitude
The optimum range is between 900 to 1 200 m.
Humidity
A minumum humidity (14:00) of 40 % must be maintained during the warmest months.
Rainfall
Coffee is sensitive to water shortages and adequate well distributed precipitation of about 1 500 mm/year should occur. Rainfall also influences flowering and coffee should therefore be produced in areas with adequate spring rains. A dry period during winter (June–August) is important for flowering.
Wind
High winds have a negative effect on growth because it increases evapotranspiration and causes tree breakage.
Nurseries
Arabica coffee is essentially grown as seedlings. No or very few plants are clonally produced, i.e. either via tissue culture laboratories or cuttings.
- Seed must be obtained from registered growers.
- Old seed germinates very poorly and care should be taken that seed of 3 months or younger is used.
- Between 1,5 and 2 kg of seed should be sufficient to establish 1 hectare.
- Minimum bag or sleeve size should be 150 x 250 mm.
- The nursery site must be well away from frosty areas.
- Use only well-sterilised potting mixtures. Well-drained sandy loam mixes are preferred.
- If not commercially available, potting mixtures can be made as follows:
- wheelbarrow of topsoil
- 2 shovels of well-composted manure
- 1 tin (440 g) of single superphosphate
- 1 tin compound fertiliser
- apply lime if pH is too low—pH should be 5,5 to 6.
- Broadspectrum granular insecticides could be incorporated into the mixture to protect seedlings against certain root pests.
- Seed should be planted not deeper than 6 mm with the centre cut facing downwards.
- Cover lightly with mulch and monitor frequently.
- Fresh seed takes 8 weeks to germinate.
Clearing and land preparation
Choice of site
- Soil depth not less than 1,5 m.
- Good drainage.
- Soil texture—sandy loam soils are ideal.
- Frost free.
- Proximity to irrigation.
- Aspect: north and west-facing slopes are warmer and drier—more stress. South-facing slopes are generally cooler—less stress and higher-quality coffee.
Layout of orchard
Within-row spacing and arrangement
- Conventional varieties can be planted at 2,4 m spacing provided that 2 plants are planted in the same planting hole (cova).
- Dwarf varieties can be planted at 2,0 m spacing depending on the number of plants per cova.
Between-row spacing
- If a small orchard tractor is used: 3 m (conventional varieties), 2,57 m (dwarf varieties).
- Hand spraying: 2,57 m (conventional varieties), 2,25 m (dwarf varieties).
- Dwarf varieties can be planted 0,4 m closer than conventional varieties.
Cova system
Benefits from planting more than one plant per cova:
- Smaller yields/tree, therefore stress is reduced.
- Mutual protection of trees results in favourable conditions for growth during early stages.
- Leaves function and photosynthesise more effectively under conditions of dim light.
- Less higher order shoots are produced. Such trees are also more open which facilitates management.
Planting and early care
Planting hole
- Young plants require loose soil for optimal development. The size of the hole should be 0,45 x 0,45 x 0,45 m.
- The top 200 mm of soil should be kept separate—only topsoil should be used for refilling holes.
- Best results are obtained by planting out early in the season.
- Planting should preferably take place during cool, wet conditions.
- Planting out can be done during the mornings and/or afternoons.
Irrigation
Dry land planting: 10 l of water per station before planting and 5 l immediately afterwards. Apply 3 to 5 l every 4 to 10 days until rain sets in. During very hot periods the irrigation interval should not exceed 4 days. Irrigation: 50 mm should be applied before planting followed by 25 mm afterwards. Irrigation interval: 25 mm every 10 days.
Other important husbandry practices
- Mix recommended fertiliser and lime well with topsoil in the planting hole. This should be done long before planting to allow the soil to settle.
- Recommended fertilizer: 30 to 60 g single supers and 30 to 60 g compound fertilizer which is high in phosphates.
- The taproot should be examined and if bent, it should be cut just above the bend.
- The upper surface of the soil in the bag should be 25 mm above soil surface.
- Make a large basin around the plant, but keep frost protection in mind.
- Apply contact insecticides to the soil on a regular basis if white grubs or dusty surface beetles are prevalent.
- The soil around the plant should be firmed by hand.
Inter-row cropping
Although the principle of inter-row cropping is controversial it is advisable in the following circumstances, namely to:
- assist financially before coffee comes into bearing
- bind soils and protect against erosion
- supply on-farm crop residue for mulch.
Types of cover crops: burley tobacco, groundnuts, soya-beans, field beans, maize and bananas.
Leaf and soil analyses
Combining information from both soil and foliar analyses is probably the most effective approach in understanding soil:plant nutrient relationships.
- Leaves should be sampled during full bloom in October/November by collecting the fourth pair, counting from the first fully-opened leaf at the tip of a primary branch from the midcanopy of the cropping region of the tree.
- Do not count the first pair if they are less than 20 mm long and take only leaves that are free from insect and/or pathogen damage.
- Take four pairs of leaves from each tree and sample at least 10 trees, i.e. 80 leaves.
- Soil samples should ideally be a composite sample which comprises many subsamples taken from the area which will be planted.
- Each composite sample must consist of at least 10 subsamples—increase this number if the field has recently been ploughed or if it is relatively large.
- Do not sample near termite mounds, antbear holes, contour ridges, drains, gravelly patches and sites previously used for stacking of fertiliser, compost or crop residue.
- Samples should be taken after the rains and when the soil has dried out.
- Every sample must be marked clearly, preferably with a label on the outside of the bag. Clean, new bags should be used—do not use a fertiliser bag.
Both leaf and soil analyses should be done well before planting.
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