Strategies for Water Management and Drought Relief
Current conditions in Zhenping County show summer corn transitioning from the bell-mouth stage to tasseling and silking, marking the critical jointing-booting period. This phase is crucial for both vegetative and reproductive growth, with water and nutrient demands peaking, and it directly influences ear and tassel differentiation, which determines yield. Meteorological data indicates 20 consecutive days of high temperatures and minimal rainfall, leading to significant drought stress in sloping fields and areas with poor irrigation, raising the risk of "neck-drought." The July-August flood season brings alternating high heat, drought, and heavy rainfall, heightening the potential for rapid shifts from drought to waterlogging. The Zhenping County Agricultural Technology Center has developed these guidelines based on corn growth characteristics and weather patterns.
1. Strengthen Water Regulation to Protect Ears
Given the persistent high temperatures and drought, urgent irrigation is needed, while remaining vigilant against sudden waterlogging. For fields with curled and wilted leaves due to rapid soil moisture loss, immediate irrigation using wells, rivers, reservoirs, or ponds is essential. Schedule irrigation during cool periods like early morning, evening, or night to avoid midday heat and prevent root shock from cold water. Promote efficient methods like drip, sprinkler, or furrow irrigation, avoiding flood irrigation. Maintain soil relative water content at 70% to 80% to support ear and tassel development and pollen mother cell differentiation, preventing issues like delayed tasseling, silk emergence, and barren tips from water stress.
Simultaneously, clear field drainage ditches, especially in low-lying and clay soils, to prepare for sudden rain. After rainfall, promptly unblock ditches to drain water within 24 hours, preventing root oxygen deprivation, early senescence, disease, and lodging. For fields with adequate moisture, avoid unnecessary irrigation. Maintain soil moisture around 70% to reduce plant temperature, prevent canopy closure and high humidity, which can suppress diseases like southern rust and leaf blight while preserving root vigor.
2. Precision Fertilization for Quality and Yield
This is a critical period for corn's nutrient demands, requiring topdressing combined with irrigation. For fields not yet fertilized, apply 20-25 kg per mu of high-nitrogen compound fertilizer, or 12-15 kg urea plus 8-10 kg potassium chloride, to avoid excessive single nitrogen use that weakens stems and risks lodging. Potassium enhances stress resistance and root activity. For drip irrigation systems, adopt a "small amount, multiple times" strategy, applying 15-20 kg per mu of high-nitrogen, high-potassium water-soluble fertilizer (e.g., N-P₂O₅-K₂O ratio 20-10-20) or 15-18 kg water-soluble urea plus 2-3 kg potassium sulfate every 7-8 days, for 2-3 sessions. This delivers nutrients directly to root zones, improving efficiency and reducing soil concentration, especially during high heat.
For weak, yellow seedlings due to late planting or poor soil, apply 5-8 kg per mu of quick-acting urea 10 cm from plants, promoting uniform growth. Combine foliar sprays with integrated pest management, applying 0.2% potassium dihydrogen phosphate plus chelated zinc (10g), boron (15g), and amino acid foliar fertilizer or brassinolide in 30 kg water, every 7 days for 2 applications, preferably after 4 PM. This mitigates heat stress, enhances pollen viability, and reduces barren tips and grain loss. After the bell-mouth stage (10 leaves), avoid chemical growth regulators to prevent tassel deformities and pollination issues.
3. Integrated Pest Monitoring and Control
High temperatures and drought can trigger pest outbreaks, while later thunderstorms may increase disease risks. Focus on pests like corn borer, cotton bollworm, aphids, and spider mites, which thrive in dry heat. Use sprays such as abamectin, pyridaben, imidacloprid, or thiamethoxam for aphids and spider mites. For borers, apply chlorantraniliprole or emamectin benzoate to leaf whorls or as granules. Avoid midday application for safety, opting for early morning or evening.
Though dry now, August rains may bring diseases like southern rust, leaf blight, and brown spot. Prepare fungicides like tebuconazole, difenoconazole, or propiconazole. Treat immediately upon spotting disease centers, especially for southern rust, to prevent outbreaks. Implement unified pest control by mixing insecticides, fungicides, and foliar fertilizers (e.g., potassium dihydrogen phosphate with zinc and boron) for a "one-spray, multiple-promotion" effect, supporting strong seedlings, grain filling, early maturity, and pest resistance.
4. Implementing Resilience Measures to Reduce Losses
For lodging caused by storms, manage by category. Slight tilting during the bell-mouth stage allows natural recovery. Moderate lodging after tasseling requires gentle straightening within 48 hours, bundling 3-4 plants together to protect ear leaves, avoiding root damage. Severe lodging areas need quick clearing to prevent mold. Apply foliar nutrients like potassium dihydrogen phosphate and brassinolide to enhance photosynthesis and recovery, reducing ear rot risk.
When temperatures exceed 35°C or during cloudy, rainy weather, pollen viability drops, leading to poor pollination. Conduct assisted pollination during peak pollen activity from 8 AM to 11 AM. For large fields, use two people pulling a rope to shake plants, or employ drones for low-altitude air disturbance to disperse pollen. Repeat every 2-3 days for 2 sessions to ensure even pollen distribution, reducing empty stalks, grain gaps, and barren tips, thereby improving ear set.