The impact of sustained high temperatures on crops is far more than just "uncomfortable heat." At the molecular level, high temperatures damage chloroplast structure, reduce photosynthetic enzyme activity, and impair the leaves' ability to produce crops. Simultaneously, abnormally increased respiration consumes large amounts of organic nutrients. Under high-temperature stress of 38℃-39℃, corn photosynthesis is significantly weakened, and reproductive development is hindered. It is estimated that for every 1℃ increase in global average temperature, rice yields decrease by approximately 3.2%, corn yields by approximately 7.4%, and soybean yields by 3.1%.
To combat heat damage, the following four scientific measures can be taken:
First, scientific water management. High temperatures accompanied by drought are most damaging to crops; timely irrigation is the core means of "regulating temperature with water." Drip irrigation, sprinkler irrigation, or micro-sprinkler irrigation should be prioritized to avoid flooding that leads to soil compaction and nutrient loss. The optimal irrigation time is early morning or evening; irrigation during the midday heat is strictly prohibited to prevent excessive temperature differences that could damage crop roots. Experiments show that after one application of sprinkler irrigation, field air temperature can rapidly decrease by 2-5℃, and relative humidity increases by 10%-20%.
Secondly, shading and covering can lower temperatures. In greenhouse cultivation, adding shade netting to the greenhouse film, with a shading rate of 30%-70%, can effectively reduce rhizosphere temperature. White shade netting can block strong ultraviolet rays without excessively hindering photosynthesis. For open-field vegetables and fruit trees, straw can be used to cover the bed surface to reduce water evaporation.
Thirdly, nutritional regulation can enhance stress resistance. Before or at the beginning of high temperatures, foliar spraying with 0.2% potassium dihydrogen phosphate solution and plant growth regulators such as brassinolide can effectively enhance crop stress resistance. Potassium dihydrogen phosphate can supplement nutrients and alleviate high-temperature stress, while brassinolide can regulate the balance of hormones in plants and protect cell membrane structure.
Fourthly, heat-resistant varieties should be selected from the source. The key gene QT12 discovered by Huazhong Agricultural University is like equipping rice with an intelligent "air conditioning system," allowing the crop to maintain stable yields even under high temperatures. Selecting heat-resistant varieties suitable for the local climate is the most fundamental defense strategy.
Furthermore, spraying pesticides in hot weather can easily cause phytotoxicity. It's best to avoid applying pesticides during the early morning dew and midday heat, and instead apply them in the evening when temperatures have dropped. During hot weather, it's also important to take precautions against heatstroke and avoid prolonged work under the scorching sun.
While high temperatures are uncontrollable, scientific measures can effectively mitigate losses. From using water to regulate temperature and providing shade, from nutrient regulation to heat-resistant breeding, each measure acts as a "cool umbrella" for crops and a crucial line of defense for ensuring food security.
