Irrigation of Controlled Environment Crops for Increased Quality and Yield—Part 2: Nutrients and Osmotic Stress
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The document discusses the importance of monitoring nutrients and stress in the irrigation of controlled environment crops. It highlights how electrical conductivity (EC) measurements relate to nutrient concentration and outlines processes affecting nutrient dynamics in substrates. Additionally, it emphasizes crop steering practices that manipulate environmental conditions to optimize plant growth and yield, underscoring the need for careful monitoring of water and nutrients.
Irrigation of Controlled Environment Crops for Increased Quality and Yield—Part 2: Nutrients and Osmotic Stress
- 2. IRRIGATION OF CONTROLLED ENVIRONMENT CROPS MONITORING NUTRIENTS AND STRESS Gaylon S. Campbell, PhD METER Group, Inc. USA
- 3. RESOURCE CAPTURE BY PLANTS 3 Assimilation • CO2 + H2O + light → carbohydrate Growth • Assimilate + Nutrients + Water → Plants Development • Temperature, daylength, water stress
- 4. CONCENTRATION AND EC • Electrical conductivity (EC) of water increases with nutrient concentration • Slope depends on makeup of solution (roughly 1 dS/m per g/l)
- 5. TWO MEASURES OF EC • ECb – Bulk EC – EC measured by in situ sensors • ECw – Pore water or substrate solution EC – What the plant “sees” TEROS 12 • Water Content • EC • Temperature EC Dielectric
- 6. WHY IS ECB LOWER THAN ECW? Water Saturated Soil Field Capacity 1. Cross section for flow is smaller in soil 2. Flow path is longer in soil ECb = ECw ECb = ECw/3 ECb = ECw/10
- 7. RELATING ECW TO ECB • Pore water EC will always be greater than ECb • At low water content, the multiplier is very large • Water content must be known to determine ECw from ECb
- 8. PROCESSES THAT AFFECT NUTRIENTS IN SUBSTRATES • Infiltration–Redistribution: water moving to deeper soil depths – water and salt content change together • Evapotranspiration: water evaporating from the soil or plant – water content changes but nutrient content stays constant • Uptake: plant removes nutrients from solution
- 11. EC WITH NUTRIENT UPTAKE Water content EC
- 12. 𝑘𝑔!"#$ 𝑚%"$&' ( × 𝑚%"$&' ( 𝑚!)*# ( = 𝑘𝑔!"#$ 𝑚!)*# ( ECw Water content Salt content × = CALCULATING SALT CONTENT The salt content of substrate is the product of water content and ECw
- 13. SHOWING SUBSTRATE NUTRIENTS Water content EC Substrate nutrient content
- 14. CROP STEERING FROM “THE AROYA GUIDE TO CROP STEERING” Crop steering is a plant growth management practice that manipulates the environment (light, climate, irrigation) to encourage plants to grow a certain way. Next to light intensity, it’s the most important tactic you can use to manipulate yield. Irrigation for optimum vegetative growth – no water stress Irrigation for optimum generative growth – simulated water stress
- 15. WATER AVAILABILITY IMPORTANT POINTS FROM LAST LECTURE • Matric Forces: Water in the capillaries and interstices of soil and growth media has lower energy than free water • Osmotic Forces: Water containing dissolved salts has lower energy than pure water when a semipermeable membrane is present (plant membranes, air gap) • Substrates used in controlled environments never have matric forces large enough to stress plants so osmotic forces must be used to simulate water stress
- 16. OSMOTIC POTENTIAL VS. EC -40 kPa per dS/m
- 17. CONTROLLED WATER STRESS DURING DRYBACK
- 18. MEASUREMENT HARDWARE AROYA Nose • Wireless mesh node • Sensor logger • Light measurement • Solar charger TEROS 12 • Dielectric permittivity • Bulk EC • Temperature
- 19. RECORD FROM A SINGLE SENSOR
- 20. CONCLUSIONS • EC directly measures the concentration of nutrients in the irrigation water • Sensors measure ECb, which, in substrates, must be converted to ECw to be useful • Water and nutrients vary over time; both need to be monitored • Osmotic potential varies directly with EC • We can manipulate osmotic potential to stress plants for crop steering • Careful monitoring and control of water and nutrients is essential for optimum production
- 21. QUESTIONS? Gaylon S. Campbell, PhD Senior Scientist METER Group, Inc. 2365 NE Hopkins Ct, Pullman, WA 99163 T 509.332.2756 E support.environment@metergroup.com W www.metergroup.com