Many indoor garden problems, and to a 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 in soil and 5.8 to 6.5 in hydroponics will allow nutrients to be chemically available; above or below this range, several nutrients become less available. For example, a full point movement in pH represents 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 or poor cultural practices.
The temperature within the leaves can climb to an excess of I I0°F (43°C). It happens easily because the leaves store the heat radiated by the lamp. At 110°F (43°C), the internal chemistry of a marijuana leaf is disrupted, 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 fortifed with micronutrients. If the soil or water supply is acidic, tdd dolomite lime to buffer :he soil pH and to keep it sweet. Avoid nutrient problems by using fresh planting mix, clean water, and a cnmplete nutrient solution. Maintain the EC and pH at proper levels, and flush the system with mild nutrient solution every lour weeks.
COMMON CULTURAL PROBLEMS
Here is a short list of some of the most common cultural problems. Some of them result in nutrient deficiencies.
1. Lack of ventilation: Leaves are strled and unable to function, causing slow growth and poor consumption of water and nutrients.
2. Lack of light; Nutrients are used poorly, photosynthesis is slow, stems stretch, and growth s scrawny.
3. Humidity: High humidity causes the plants to use less water and more nutrients. Growth is slow because stom-ata are not able to open and increase the transpiration. Low humidity stresses the plants because they use too much water.
4. Temperature: Both low and high temperatures slow the growth of plants. Large fluctuations in temperature-more than 15 to 20°F or 8 to 10°C-causes slow growth and slows the plant's process.
5. Spray application damage: Sprays are phytotoxic, and they can burn the foliage if the spray is too concentrated or if sprayed during the heat of the day.
6. Ozone damage: See Chapter Thirteen "Air," for more information on ozone damage.
7. Overwatering: Soggy soil causes a menagerie of problems. It cuts the air from the roots, which retards the nutrient intake. The plant's defenses weaken. Roots rot when severe.
8. Underwatering: Dry soil causes nutrient transport to slow severely. It causes nutrient deficiencies and sick foliage, and the roots die.
9. Light burn: Burned foliage is susceptible to pest and disease attack.
10. Indoor air pollution: This causes very difficult-to-solve plant problems. Always be aware of chemicals leaching or vaporizing from the pressboards and other building materials. Such pollution causes plant growth to slow to a crawl.
11. Hot soil: Soil over 90°F (32°C) will harm the roots. Often, outdoor soil that is used in the containers warms up to well over 100T (38°C).
12. Roots receiving light: Roots turn green if the light shines through the container or the hydroponic system. Roots require a dark environment. Their function slows substantially when they turn green.
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