Hybrid late rice varieties offer significant advantages, including large panicles, high grain numbers, and strong tillering ability. Compared to conventional rice varieties, they can yield 20% to 30% more. Their high productivity depends largely on effective tillering, which requires a substantial amount of fertilizer. However, due to the high temperatures during early growth stages, fertilizers tend to decompose quickly and are efficiently absorbed. As the temperature decreases later in the season, fertilizer breakdown slows down, leading to reduced soil fertility and an increased risk of premature aging. This can negatively impact grain and spike development. To maximize yield, it is crucial to implement proper fertilization strategies, focusing on techniques that enhance productivity while avoiding common pitfalls.
One key practice is increasing potassium fertilizer application. Potassium enhances root absorption, improves tillering at the node level, strengthens stem resistance to lodging and disease, and accelerates nutrient transport within the plant. It also increases the number of grains per panicle and the weight of 1,000 grains. According to agricultural research, during the growth cycle of hybrid late rice, 35 kg of ammonium sulfate, 22 kg of superphosphate, and 22 kg of potassium chloride per acre are typically needed to meet the nitrogen, phosphorus, and potassium requirements.
Early fertilizer application is also essential. Applying tiller fertilizer shortly after transplanting—usually 5 to 7 days post-transplanting—helps promote early growth. This initial top-dressing usually accounts for 20% to 25% of the total fertilizer. Nitrogen-based fertilizers should dominate this stage, with some phosphorus and potassium added. If base fertilizers were insufficient, additional tiller fertilizer should be applied. For example, 7–10 kg of urea or 25 kg of ammonium bicarbonate per acre can be used. When using ammonium bicarbonate, it's important to mix it with fine soil and apply it when the field has 3–5 cm of water to prevent seedling burn. After 7–10 days, any weak seedlings can receive additional fertilizer based on their growth condition.
Hybrid rice is highly sensitive to moisture. After the plants turn green, a light irrigation can help stimulate root development. Then, shallow water irrigation should be used to maintain moisture. Water management can also help regulate nutrient availability, especially during high-temperature periods when deep watering can help control temperature and encourage multiple crop cycles.
Applying panicle fertilizer is another critical step. There are two types: flower-promoting fertilizer, applied during the early stages of panicle development, and flower-preserving fertilizer, used later to support grain filling. In fields where tiller fertilizer was insufficient or plant growth is poor, applying fertilizer at the beginning of young panicle differentiation (when the penultimate leaf is just visible) can help increase the number of branches and spikelets.
Finally, the "breakage fertilizer" or grain fertilizer should be applied during the heading stage. Its purpose is to maintain plant vigor, prevent premature aging, and improve grain weight. If the leaves start to yellow during heading, 2–3 kg of urea and 2 kg of potassium chloride can be applied, or foliar sprays of 1% urea solution and 0.2% potassium dihydrogen phosphate solution can be used twice, seven to eight days apart. After full panicle development, spraying a 0.2% to 0.25% potassium dihydrogen phosphate solution on the leaves two to three times helps transfer nutrients into the grains and prevents late-stage issues.
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