In spring, greenhouse vegetables are particularly susceptible to harmful gases, which can significantly reduce their quality and market value. It is essential to monitor and manage the occurrence of these gases to ensure healthy plant growth.
Common types of harmful gases in greenhouses include:
1. **Ammonia Poisoning**: This occurs when improperly decomposed organic fertilizers or excessive inorganic fertilizers like urea and ammonium bicarbonate are used. Ammonia can damage plant cells, leading to water-soaked spots on leaf tips, yellowing and browning of leaf edges, and eventually, dry and wilted leaves.
2. **Nitrous Acid Poisoning**: Excessive use of ammonium nitrate can hinder soil nitrification, causing a buildup of nitrous acid gas. This leads to irregular green-white spots on affected leaves.
3. **Sulfur Dioxide Poisoning**: Generated during heating, sulfur dioxide enters through leaf stomata, damaging chloroplasts and causing dehydration, white spots, and leaf drying. In severe cases, entire leaves may turn pale with brown veins.
4. **Carbon Monoxide Poisoning**: Resulting from incomplete coal combustion or poor ventilation, carbon monoxide causes leaf discoloration, water-stained veins, and yellowing or necrotic spots.
5. **Sulfite Poisoning**: Excess ammonium sulfate or unrefined organic fertilizers can release sulfur dioxide, which turns into sulfite in water. This damages chlorophyll, acidifies soil, and causes white spots on leaves.
6. **Carbon Dioxide Poisoning**: High COâ‚‚ levels cause leaf curling, starch accumulation, and chloroplast deformation. Severe cases lead to wilting and reduced photosynthesis, as well as impaired respiration and premature aging.
7. **Film Gas Poisoning**: Plastic films containing phthalates or other volatile chemicals can emit harmful gases under high temperatures, resulting in chlorosis, yellowing, and leaf drying.
**Gas Diagnosis**: In spring, harmful gas detection can be done by analyzing dew pH. Acidic dew (pH < 4.6) suggests the presence of ammonia, sulfur dioxide, or carbon dioxide. Using pH test strips before morning ventilation helps identify the type and severity of gas exposure.
**Prevention and Control Measures**:
1. **Fertilizer Management**: Use well-decomposed organic fertilizers and minimize nitrogen application. Apply phosphorus and potassium fertilizers carefully, avoiding chlorine- or sulfur-based products. Foliar feeding between 11 am and 2 pm on sunny days is recommended.
2. **Ventilation**: Ensure proper air circulation by opening vents in the morning and extending ventilation time as temperatures rise. Even on cloudy or snowy days, short periods of ventilation at noon help reduce humidity and harmful gases.
3. **Heating Practices**: Avoid using coal for heating without proper combustion and install chimneys to vent harmful gases. Maintain good ventilation to prevent carbon monoxide and carbon dioxide buildup.
4. **Film Selection**: Choose non-toxic plastic films without harmful additives. Opt for vinyl-based films to reduce the risk of chemical emissions.
By implementing these strategies, greenhouse growers can effectively manage harmful gases and maintain the health and productivity of their crops.
Puffed corn flour is a type of flour made from corn that has been puffed or expanded through a process of heat and pressure. The process involves heating the corn kernels until they become soft and moist, and then rapidly releasing the pressure, causing the kernels to puff up. The puffed corn is then ground into a fine flour that can be used in a variety of recipes. Puffed corn flour is often used as a gluten-free alternative to wheat flour in baking and cooking, and is also used in snack foods such as popcorn and corn chips. It is high in fiber and protein, and has a light, airy texture that makes it ideal for use in baked goods.
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