Detailed Explanation of the Three Fertilizations for Rice and Their Application Techniques

Scientific fertilization is one of the important measures for achieving high quality and high yield in rice. However, rice fertilization is a highly technical task, and in practice it must be flexibly managed according to variety characteristics, soil fertility, climatic factors, and cultivation conditions. As is well known, the fertilizer requirements of rice are expressed in the nutritional period, the critical nutritional period, and the period of maximum nutritional efficiency. For example, early rice has a short growth period and relatively low fertilizer demand, so fertilization should be early and concentrated. Middle rice and late rice have longer growth periods, high fertilizer demand, and strong absorption intensity, so the number of topdressings should be increased and the proportion of topdressing raised. The critical nutritional period for nitrogen, phosphorus, and potassium in rice generally appears at the three-leaf stage, and sometimes the critical nutritional period for nitrogen and potassium also appears at the young panicle differentiation and young panicle formation stages. The period of maximum nutritional efficiency in rice appears at the long panicle stage, which is the most vigorous stage of vegetative growth and reproductive growth, and is also the key period for fertilizer demand. According to research, for every 100 kg of rice grain produced, about 1.6-2.5 kg of nitrogen, 0.8-1.2 kg of phosphorus, and 2.1-3.0 kg of potassium need to be absorbed from the soil. Based on the above fertilizer requirement characteristics of rice, in production it is necessary to apply sufficient base fertilizer and then pay close attention to applying the "three fertilizations" well, namely tillering fertilizer, panicle fertilizer, and grain fertilizer.

I. Apply tillering fertilizer early and at the right time. The topdressing applied to rice from transplanting until the beginning of young panicle differentiation is called "tillering fertilizer." Tillering fertilizer requires early application and sufficient quantity; generally, the amount of tillering fertilizer accounts for 50-60% of the total topdressing. This is because the tillering stage is the first peak period of nitrogen nutrient absorption in the entire life of rice, and because in the early growth stage of rice the air temperature, water temperature, and soil temperature are all relatively low, nutrient release is slow, and too little topdressing makes it difficult to meet the rice's nutrient needs. Only timely early application is conducive to early tillering and more tillering in rice, lowering the tillering node position, and creating conditions for striving for longer panicles and grain weight. Tillering fertilizer is applied 7-10 days after rice transplanting, with 5-7 kg of urea applied per mu. If the base fertilizer is insufficient, it may be appropriately increased, but excessive topdressing must be avoided to prevent excessive growth in the middle and late stages and delayed maturity due to greedy green growth.

II. Skillfully apply panicle fertilizer. The topdressing applied to rice from the beginning of young panicle differentiation to before heading is called "panicle fertilizer." This period is the second peak period of nitrogen absorption. Scientifically applying panicle fertilizer well can not only protect flowers and increase grains, promoting large panicles and many grains, but also prevent greedy green growth and lodging. Technically, several points should be achieved: first, do not apply it to fields with good soil fertility, sufficient base fertilizer, and many tillers; second, apply it when there is no dew on the leaves in the morning, the leaves are upright at noon, and the leaf color is pale yellow; third, do not apply it on rainy days, and apply it promptly on sunny days. The application time is at the rice stem elongation stage, with 3-4 kg of urea applied per mu, and 50 kg per mu of a 0.2-0.3% potassium dihydrogen phosphate solution evenly sprayed on the leaf surface.

III. Apply grain fertilizer as appropriate. The topdressing applied after rice heading is called "grain fertilizer," also known as "seed-strengthening fertilizer." Applying grain fertilizer as appropriate can effectively extend the functional period of the leaves, prevent premature aging, and increase grain weight. However, it should be noted that it should not be applied when the seedlings are not yellow, not applied on rainy days, and not applied to fields with disease. Choose a sunny afternoon to spray a 1% urea solution, or 1:500 dilution of Huimanfeng active liquid fertilizer, with 50 kg per mu for spraying. For rice fields that have already developed sheath blight and rice blast, pesticides such as juncaijing, isoprothiolane, wenkujing, nongkang 120, and xiaojunling should be selected for alternating spraying to promptly prevent and control them.