Misdiagnosed Disorders
Marijuana Horticulture
by Jorge Cervantes
Many indoor garden problems, and to lesser degree outdoor problems, are misdiagnosed as a lack of fertilizer. Often, disease and insects cause such problems. other times, problems are caused by an imbalanced pH of the growing medium and water. a pH between 6.5 and 7.0 in soil and 5.8 to 6.5 in hydroponics will allow nutrients become less available.
For example, a full point movement in pH represent a tenfold increase in either alkalinity or acidity. This means that a pH of 5.5 would be ten times more acidic than a pH of 6.5. in soil, a pH below 6.5 may cause a deficiency in calcium, which causes root tips to burn and leaves to get fungal infections and dead spots on foliage. A pH over 7 could slow down the plant’s iron intake and result in chlorotic leaves causing veins to yellow.
Incorrect pH contributes to most serious nutrient disorders in organic soil gardens. Many complex biological processes occur between organic fertilizers and the soil during nutrient uptake. The pH is critical to the livelihood of these activities. When the pH fluctuates in a hydroponic garden, the nutrients are still available in the solution for uptake, and the pH is not as critical. Electrical conductivity is the most critical indicator of plant health and nutrient uptake in hydroponics.
Once a plant shows symptoms, it has already undergone severe nutritional stress. It will take time for the plant to resume vigorous growth. Correct identification of each symptom as soon as it occurs is essential to help plants retain vigor. Indoor, greenhouse, and some outdoor marijuana crops are harvested so fast that plants do not have time to recover from nutrient imbalances. One small imbalance could cost a week of growth. That could be more than 10 percent of the plant’s life!
Do not confuse nutrient deficiencies or toxicities with insect and disease damage r poor cultural practices.
The temperature within the leaves can climb to an excess f 110F. It happens easily because the leaves store the heat radiated by the lamp. At 100F, the internal chemistry of a marijuana leaf is disturbed. The manufactured proteins are broken down and become unavailable to the plant. As the internal temperature of the leaves climbs, they are forced to use and evaporate more water. About 70 percent of the plant’s energy is used in this process.
The basic elements of the environment must be checked and maintained at specific levels to avoid problems. Check each of the vital signs – air, light, soil, water, temperature, humidity, etc. – and fine-tune the environment, especially ventilation, before deciding that plants are nutrient deficient.
Nutrient deficiencies are less common when using fresh potting soil fortified with micronutrients. If the soil or water supply is acidic, add dolomite lime to buffer the soil pH and to keep it sweet. Avoid nutrient problems by using fresh planting mix, clean water, and a complete nutrient solution. Maintain the EC and pH at proper levels, and flush the system with mild nutrient solution every four weeks.