Definition and Composition: Water-soluble fertilizer is a soluble fertilizer with nitrogen, phosphorus, and potassium as its core (N+P₂O₅+K₂O≥50%). It can also contain added micronutrients such as calcium, magnesium, zinc, and boron. Its complete water solubility allows it to be directly delivered to the roots through drip irrigation, saving over 60% more water than traditional spraying. Actual measurements of navel oranges in southern Jiangxi show that the sugar content of fruit trees treated with water-soluble fertilizer increased by 2.3 degrees Brix. It is important to check the solubility when purchasing fertilizer, as inferior fertilizers can easily clog drip irrigation pipes (for example, farmers may spend two days clearing pipes due to excessive insoluble matter).
National Standards: The current standard NY1107-2010 stipulates that solid fertilizers must contain ≥50% total nutrients and liquid fertilizers ≥400g/L. The new regulations for humic acid in 2025 are even stricter, reducing arsenic content to 5mg/kg and cadmium to 1mg/kg, adding thallium and vanadium testing, and requiring small molecule (<1000Da) active components to be ≥30%. Experiments in the Poyang Lake Plain showed that humic acid fertilizer conforming to the new regulations advanced the tillering stage of rice by 3 days and increased rice yield by 46 jin per mu. A test report is required when selecting fertilizer.
Application Methods
1. Drip Irrigation: 2-5 kg/mu/time, every 7-15 days. Before application, drip the fertilizer solution for 30 minutes to lubricate the pipes with clean water, then drip the fertilizer solution, and finally flush the pipes with clean water for 20 minutes (otherwise, scale will form on the drippers, reducing water output by 40%).
2. Fertigation: 5-10 kg/mu, diluted 1000-2000 times with water and applied evenly (avoid direct application of powder, which can burn roots).
3. Foliar Spray: When nutrient deficiency occurs, mix 100g of fertilizer with 50-100kg of water and spray, avoiding the high-temperature period from 10:00-15:00 (effective in correcting yellow leaf disease in Fuzhou tangerine orchards every 7 days).
Advantages:
1. High absorption rate: Utilization rate reaches 80%-90% (traditional compound fertilizers only 30%-40%), increasing nitrogen utilization rate of early rice in Ji'an by 2.3 times, saving 20 catties of fertilizer per mu.
2. Labor and water saving: When used with drip irrigation, it saves 3 cubic meters of water per mu per application, reducing labor costs by 70% (reducing the number of workers in Yongxiu vineyards from 10 to 3).
3. Flexible formula: Adjustable according to growth stage (e.g., high nitrogen 30-10-10 for seedling stage, high phosphorus 10-50-10 for flowering stage, and high potassium 10-10-40 for fruit expansion stage), increasing camellia oleifera yield in southern Jiangxi by 27%.
4. Environmentally friendly: Chlorine-free and heavy metal-free, monitoring around Poyang Lake shows that soil organic matter increases by an average of 0.12% annually, and the acidification rate slows down by 60%.
