Irrigation & Watering Guide: Crop-Specific Protocols for Coco Coir Systems

Start irrigation 1–2 hours after sunrise — never irrigate into a cold, dark slab. In summer, increase shot frequency before reducing shot size; frequency is more effective at preventing moisture deficit. Target 5–8% overnight drydown for optimal fruit set and sugar concentration. Raise EC by 0.3–0.5 mS/cm during fruit ripening to improve Brix.

Cucumbers are among the most salt-sensitive crops. Runoff EC exceeding 5.0 mS/cm causes bitter fruit — monitor daily. First shot within 30–60 minutes of sunrise as they resume transpiration faster than tomatoes. If the canopy develops rapidly, add 1–2 extra mid-morning shots to prevent moisture deficit.

Blossom End Rot (BER) is the primary quality issue — caused by calcium deficiency driven by high EC or moisture fluctuations. Maintain consistent substrate moisture; pronounced wet/dry cycles increase BER risk significantly. pH 6.0–6.5 optimises calcium availability in coir. Open bags weekly to check substrate moisture and root health.

Botrytis cinerea is the primary disease threat. The substrate surface must lighten visibly between the last shot and next morning — overnight drydown discipline is non-negotiable. Elevation of feed EC to 2.8–3.2 mS/cm in the final 2–3 weeks before harvest concentrates sugars. Inspect crown tissue weekly for early water-soaked lesions at the base of leaf stems.

Raspberries are particularly sensitive to waterlogging — maintain 15–20% overnight moisture drydown. Avoid evening irrigation; cool wet root conditions overnight significantly increase Pythium risk. During primocane establishment, reduce EC and irrigation volume. Inspect root tip colour every two weeks — healthy roots are white to pale cream.

Blueberries require pH 4.5–5.5 — significantly lower than every other crop in this guide. pH drift above 5.5 causes iron and manganese deficiency, chlorosis, and crop failure. Acidify every irrigation batch before application. Monitor substrate pH monthly. Use sulphate-based fertilisers where possible to maintain an acidic root environment. EC must remain very low (0.8–1.5 mS/cm) — blueberries evolved in low-nutrient, acidic soils.

Basil is the most temperature-sensitive — do not irrigate with cold water below 15°C. Mint is the most vigorous; reduce irrigation frequency once established as overwatering causes root rot quickly. Coriander bolts in high temperatures — consistent moisture delays bolting. Short crop cycles mean EC can build up fast; flush promptly if runoff exceeds 4.0 mS/cm.

Brix (sugar content) is directly linked to EC management. Elevate feed EC to 3.5–4.5 mS/cm in the final 2–3 weeks before harvest. Reduce irrigation frequency (not shot size) at ripening — gradual EC elevation over 7–10 days prevents fruit cracking. Keep fruit off the substrate surface; direct contact causes rot. Use netting or foam supports.

Eggplant is the most temperature-sensitive solanum crop — root zone temperature below 18°C causes transplant shock and poor establishment. Monitor substrate temperature at planting; in early spring, substrate can be 8–12°C colder than ambient air. Build EC gradually over 2 weeks post-transplant. Reduce EC to 2.0–2.5 mS/cm for the first 7–10 days after transplanting for best establishment outcomes.

Stem length is the primary quality metric — root zone temperature (target 16–22°C) has a stronger effect than EC on stem elongation. Do not exceed 4.0 mS/cm substrate EC; high EC reduces stem length and petal count. After cut-back, reduce irrigation frequency for 5–7 days to allow regrowth shoots to establish root zone priority. Watch for Tipburn on outer petals — it indicates calcium supply problems at high transpiration rates.