On farm innovations that increase production irrigated macadamia production – a south african perspective - gerhard mostert
CLIMATIC CONDITIONS Best results from macadamias are achieved at temperatures between 20° and 25°C. Soil temperaturesless than -1°C can severely affect young trees and frosts of -6°C will kill young trees and damage flowers andfoliage 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.
• < 20 % area under Mac production have rainfall >1200mm/yr• All the Northern areas - dry winter and spring
IMPORTANCE OF IRRIGATION 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
CRITICAL PERIODS FOR NO WATER STRESS Flowering Fruit set Exponential fruit growth
WATER REQUIREMENTS• 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
IRRIGATION TYPE• 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
SCHEDULING• 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. 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