Gerhard Mostert

Best results from macadamias are achieved at

temperatures between 20° and 25°C. Soil temperatures

less than -1°C can severely affect young trees and frosts

of -6°C will kill young trees and damage flowers and

foliage of older trees. Prolonged exposure to over 35°C

will also cause stress.

Average annual rainfall should be at least 1200mm,

otherwise irrigation is required. Between 1500mm

and 2500mm is ideal for most soils.

CLIMATIC CONDITIONS

• < 20 % area under Mac production

have rainfall >1200mm/yr

• All the Northern areas - dry winter

and spring

Yield !!! = profit

In a season of below average rainfall (Clunes, Northern New South Wales,

Australia), irrigation increased yield of Macadamia var. 246 from 10.54 kilograms

per tree of nut in shell (10 % moisture nis) for non irrigated trees to 20.79

kilograms (10% moisture nis) for irrigated trees, an increase of 97 %.

- Col Peak and Ned Sutherland

South Africa Average Dry land yield = 2t/ha

Irrigation = 3 to 5 t/ha

IMPORTANCE OF IRRIGATION

Flowering

Fruit set

Exponential fruit growth

CRITICAL PERIODS FOR NO WATER STRESS

• Total water requirement (effective)

• 950mm to 1100 mm/ha/year

• 32 000 liter/tree/year (313 trees/ha)

• Max daily water use (January)(mature trees)

• 6 mm/ha/day

• 190 liter/tree/day (313 trees/ha)

• Rainfall

• 750 mm to 1400 mm

• 30 to 50% effective

• Irrigation supplement

• Varied from 400mm to 1000 mm/year

WATER REQUIREMENTS

• Dry land ? around 50 %

• 10% increase from 2 ton/ha(DIS) = 200 kg

• 200 kg (DIS) @ $2,5/kg = $500/ha

• This is enough to finance the capital cost plus pay for the running cost of irrigation

• Micro

• 90% of irrigated area

• Drip

• Very promising but still small area

IRRIGATION TYPE

• High frequency

• Very shallow root system

• Proteoid roots, also known as cluster roots, are plant roots that form clusters of closely spaced

short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf

litter. They enhance nutrient uptake, possibly by chemically modifying the soil environment to

improve nutrient solubilisation.[1] As a result, plants with proteoid roots can grow in soil that is

very low in nutrients, such as the phosphorus-deficient native soils of Australia.

• Thick mulch layer

• Less the 20 % depletion of easily available water

• Keep top soil moist and subsoil moist to dry

SCHEDULING

Irrometers

Probes

SHEDULING EQUIPMENT

This can happen in a short

time

More problematic than under

irrigation

OVER IRRIGATION

THANK YOU