Pink Mist, Tropicana Cookies Purple, Sour Diesel, Haze Berry

The humidity was adjusted to 70% using a humidifier (AC Infinity CLOUDFORGE T7) since the plants showed signs of wilting. After the adjustment, they recovered within one day. The seven larger plants were topped, while the other two smaller plants ramained untreated (Haze Berry, Pink Mist). These smaller plants will not be topped during this grow. The plants are still being watered with plain water once a day.

In the small box the humidity was set too high for the plants (70% relative humidity (RH)). Since the humidifier activated upon reaching this threshold and there was a lack of air exchange in the small box, the overall humidity remained too high, which hindered plant growth and caused the plants to droop, turn yellow, and become necrotic. Next time, the threshold should be set between 60–65% RH. Other than that, the plants were transferred into larger pots (20 L). BioBizz Light Mix is used as the substrate. Additionally, 3 g of dolomitic lime per liter of substrate was added. Mycorrhizal microgranules (R&R Shop) were also incorporated (Mycorrhizae (Glomus spp.); Rhizosphere bacteria: 1 × 10⁸ CFU/g, Beauveria spp.: 5 × 10⁷ CFU/g). The temperature and RH are controlled by the humidifier and two heating devices. One of them is set to keep the temperature in the room where the tent is located at 22,5°C. Together with the heat from the lamps and the humidifier, this results in conditions of around 23°C and 68% RH. The other heater (Thermoforge T3-AC Infinity) blows warm air into the tent and is set to activate when the temperature drops to 21°C—this is used to keep the plants warm when the lamps are turned off. The plants will now be given fertilizer from BioBizz (75% of the volume specified by the manufacturer is used).

After the plants were placed under stable conditions, they recovered. Since last week, the conditions in the tent have not changed. The leaves of the plant in the middle have turned yellow and developed brown spots that resemble a Cal-Mag deficiency, which might be a result of a low pH in the soil. The pH in the soil was measured after watering the plants with a pH 8.6 solution. The pH in the soil turned out to be 6.3, meaning it was likely lower before watering, which might explain the observed symptoms. The water supply will be increased by 0.1 L whenever the plants appear dry after one day. The pH of the solution will be set to 7, and the soil pH will be tested again in one week. The dolomit lime used to regulate the pH during growth is not present in the small pot that was transferred into the larger pots, so its effect cannot be observed yet.

Since the pH of the water was adjusted, the plants no longer showed any yellowing or signs of damage. The plants are still watered every two days. The pH of the watering solution was first adjusted to 8.6 (08.03), then to 7.2 (10.03), and finally to 6.8 (12.03 / 14.03). After watering with a pH of 6.8 (14.03), the substrate pH was measured, showing 6.4 at the center and 5.7 towards the edges. Due to this low reading, the plants were immediately watered again with 0.3 L of solution adjusted to a pH of 8,6. Following this, subsequent pH measurements in the substrate ranged between 6.3 and 6.5. In the following solutions, the pH should be higher again (7.6 - 7.8). The plants now receive 300 ml. Low-stress training was applied to the plants that were topped three weeks ago. Since the plants are infected with thrips, beneficial insects (lacewing larvae) were applied to control them. In the following weeks, lacewing larvae will be applied every two weeks.

The plants exhibited mild symptoms, likely caused by a pH imbalance and possibly excess nitrogen. For this reason, the plants were only watered with Cal-Mag and pH Up. Due to possible pH issues, the substrate pH was measured frequently: • 17.03: pH 6.2–6.5 • 18.03: pH 5.9. Plants were watered with a pH-corrected solution (10 mL/L Bio Up). Twelve hours later, the pH was measured again and was around 6.2–6.3. • 21.03: The same procedure was repeated. Twelve hours later, the pH was around 5.9–6.1. The pH Up does not seem to have a strong or lasting effect – even though it is used in high amounts. It increases the pH of the watering solution, but this effect seems to wear off after application. Since the current bottle is not fresh and was not stored according to the manufacturer’s recommendations, a fresh bottle will be used, and its effect will be monitored. Additionally, the water used for irrigation will now consist of 100% tap water. Previously, a 1:1 mix of tap and (RO) water was used. This change was made in the hope that the dissolved substances in tap water will provide better buffering capacity. LST was applied for the 4 biggest stems. Due to the size of the plants, they will be switched to flowering in 2–3 days.

The light cycle was changed to 12:12 on 24 March. The threshold of the humidifier was adjusted according to an online calculator (https://vpdchart.com/) using a 1.5 °C leaf temperature offset. Water consumption has doubled over the past week. Four grams of silicate powder were added to 10 L of nutrient solution. After all other fertilizers had been added the pH was subsequently adjusted to 8.6 with Bio up, as the soil still exhibits a tendency towards acidification. The soil pH was measured prior to the silicate treatment and was found to be approximately 5.8 to 6.0, which had already led to initial symptoms on the plant leaves. The aim for the following week is to maintain a stable soil pH and to observe whether new leaves develop without symptoms.