Open Hydroponic Systems - an Overview Rian Briedenhann

Today’s Situation Buzz words are quality & hi-tech Plant manipulation More advanced fertigation & irrigation No textbook response

Scheduling Sunlight Biomass production Water Oxygen Nutrients

Principles of Fertigation Concentration of individual inorganic ions in the plant depend on the: –Rate of uptake –Concentration in nutrient solution –Uptake of water –Intensity of transpiration

Principles of Fertigation Consumption rates of nutrients by the tree –rootstock / clone combination –plant population –growth stage –climatic conditions –water supply –plant size

Open field hydroponics 3 Pillars of the system Maximum advantage of environmental factors Drip irrigation / Restricted rootzone Nutrient solution manipulation

Environmental factors High noon - max sunlight and energy –Will give us maximum Transpiration Stomatal conductivity CO 2 assimilation Photosynthesis

cell growth (-) wall synthesis (-) protein synthesis (-) nitrate reductase level (-) abscisic acid (+) stomatal opening (-) CO2 assimilation (-) sugar accumulation (+) proline accumulation (+) Physiological Aspects of Water Stress

Why use drippers ? High O 2 / Low H 2 O Low O 2 / High H 2 O Dripper

Photosynthesis 6 am pm Non stressed Rate Stressed 9 am

Environmental factors Water requirement Growth period Normal irri scheduling Open field hydroponics Area of water deficit

IRRIGATION SCHEDULING

Pulsing 10 Pulsing 50% of PAW

Soil moisture regimes Rooting volume 0.3* * * *0.6 3*21min 4*15min 6*9min 11*5min

Factors affecting Fertigation efficacy Correct application techniques requires paying attention to the following: –Water : quantity and quality –Nutrients : needs and demand cycle –Fertilizers : characteristics and compatibility –Installations : dissolution, storage, injection

Environmental factors Management of environmental factors Orchard layout/design –row direction –ridges –plant spacing –trellis system –cultivar / rootstock selection

Open Hydroponic Production Max. Adv. Of Environmental Factors + Drip irrigation + Nutrient Solution Maximum Transpiration Stomatal conductivity CO 2 assimilation Photosynthesis Maximum yield and fruit Quality

Complimentary Practices Tree Formation training method for light management Cultivar / Rootstock combination early production vigor control nutrient uptake fruit quality

Complimentary Practices Spacing North / South orientation Pruning practices Hormone manipulation

Complimentary Practices Stress management Growth regulation Girdling Fertigation 2 drippers per tree

Complimentary Practices Stress Control Growth regulators Flower regulators Regulated Deficit Irrigation –Pre bloom, Post bloom –Pre harvest, Post harvest Girdling Fertigation –Restricted root growth area - Drip pots

Nutrient solution Soil contribution regarding nutrient supply??Soil contribution regarding nutrient supply?? Fertilization program based on concentration and weight units per plantFertilization program based on concentration and weight units per plant Composition of irrigation water considered when preparing nutrient solutionComposition of irrigation water considered when preparing nutrient solution Buffered at pH Buffered at pH Adapted to the Phenology of plant (growth events)Adapted to the Phenology of plant (growth events)

General formula for …. More fruit and less wood production.N (=), P (+), K (++), Mg (--) More wood and less fruit production.N (=), P (-), K (--), Mg (++).“ Good Fruit Grower – Tree Fruit Nutrition, edit by A. Brooke Peterson and Robert G. Stevens”

TIME Growth Stage Development Phase Mid-May to JulyFloral induction and initiation Transition of resting buds to floral buds Aug. to mid-Sept.Pre-bloomBud break and inflorescence development Mid-Sept to Oct.FloweringFlowering and initial fruit set Nov. to Dec.Stage I Fruit growthFruit cell division and physiological fruit drop Jan. to Apr.Stage II Fruit growthFruit cell expansion May onwardsMaturationFruit maturity and harvest

Fruit World – Fertigation systems (Very complex system – but shows need for automation)

Mulching vs no-mulching OHS With OHS, the objective is to form root balls as close to the soil surface as possible to minimize soil interaction with the nutrient solution. Mulching speeds up the process of forming roots near the surface.