How to achieve rational fertilization in sorghum cultivation
What kinds of smut diseases affect sorghum? In North China, three are common: loose smut, covered smut, and head smut. (1) Sorghum loose smut: the entire panicle or part of the grains are affected. Before the diseased grains rupture, there is a layer of grayish-white membrane; after the membrane ruptures, black powder (the pathogen) is released, exposing a long, curved central axis. This is sorghum loose smut...
Sorghum has wide adaptability to soil and strong nutrient uptake capacity. When planted on sandy loam rich in organic matter and with relatively high fertility, it is relatively easy to obtain high yields. In lean and dry land with phosphorus deficiency and low potassium, fertilizer must be increased to obtain a good harvest. During the seedling stage, sorghum plants are small and do not need much fertilizer, but the requirement is relatively strict. From jointing to flowering, the plants grow vigorously, and the distribution center of nutrients shifts accordingly from stems and leaves to the young panicle starting at jointing, and finally is stored in the panicle to form grains. Therefore, ensuring sufficient nutrient supply at this time is the foundation for high yield. From flowering to maturity, the supply of nitrogen, phosphorus, and potassium directly affects grain filling and maturity in sorghum. An appropriate nitrogen supply can accelerate grain filling and increase the protein content in the grains, but too much or too late application can also cause excessive vegetative growth and delayed maturity, reducing yield and quality. Generally, it is required to apply 2000 to 3000 kg of organic fertilizer, 15 to 25 kg of superphosphate, and 10 to 20 kg of potassium fertilizer per mu as base fertilizer. There are two methods of base fertilizer application: broadcasting and banding. Broadcasting is mostly done before sowing in combination with plowing and harrowing the field to broadcast the base fertilizer. Banding is done by forming ridges and opening furrows before or after sowing. In addition, at sowing, applying 1000 kg of decomposed dilute manure water per mu or a small amount of nitrogen chemical fertilizer as seed fertilizer is beneficial for full stand and strong seedlings. Topdressing is mainly based on quick-acting nitrogen fertilizer, mainly jointing fertilizer and booting fertilizer. The best topdressing periods for sorghum are the jointing stage and the large trumpet stage, to promote panicle differentiation and reduce floret degeneration, achieving large panicles and many grains. When topdressing urea exceeds 15 kg per mu, it should be applied in stages. For sorghum topdressing, it is better to apply more early and less later: heavy application of jointing fertilizer (at the jointing stage) and light application of booting fertilizer (at the booting stage). Generally, when two-thirds of the leaves are fully expanded, apply 5 to 8 kg of potassium fertilizer and 40 kg of ammonium bicarbonate per mu. Apply in furrows, holes, or by broadcasting; when broadcasting, it must be combined with deep intertillage or watering to facilitate fertilizer efficiency. In the later growth stage, appropriate foliar topdressing can be done. At the heading and early grain-filling stages, spray potassium dihydrogen phosphate (at a concentration of 0.1 percent) or urea (at a concentration of 2 percent) to promote early maturity and increase yield. In sorghum production, attention must be paid to balanced fertilization, especially the combined application of nitrogen and phosphorus, which can avoid imbalance in nutrient supply and significantly improve fertilizer efficiency. On low-yield plots, the soil is inherently deficient in nitrogen and phosphorus. Applying a single fertilizer often cannot function well due to an imbalance in the nitrogen-to-phosphorus ratio, resulting in fertilizer waste and little yield increase. According to experimental research, combined application of nitrogen and phosphorus as seed fertilizer can promote growth, with faster seedling growth, more leaves, and stronger growth vigor, enhancing the plant's metabolic function, improving the plant's absorption capacity, significantly improving fertilizer efficiency, increasing panicle weight, and greatly increasing yield, potentially doubling production. Therefore, rational matching and balanced fertilization on low-yield soil is an effective measure for economical fertilization.