Wheat requires 16 essential nutrients for healthy growth and development, including carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, magnesium, calcium, iron, manganese, zinc, copper, chlorine, boron, and molybdenum. Carbon, hydrogen, and oxygen are primarily obtained from air and water, while the remaining 13 elements are mainly taken up from the soil. These nutrients are categorized into macronutrients and micronutrients based on their concentration in the plant. Macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, with calcium, magnesium, and sulfur sometimes referred to as "secondary nutrients." They make up tens to several thousandths of the dry weight of the crop. Micronutrients, such as iron, boron, manganese, copper, zinc, molybdenum, and chlorine, are required in much smaller quantities—usually in parts per million or even parts per billion.
All these nutrients are equally vital for plant health. A deficiency in any one of them can significantly affect wheat growth and yield. Among the macronutrients, nitrogen, phosphorus, and potassium are particularly critical and are often referred to as the "three main elements of crop nutrition" or simply the "fertilizer trio." Their availability in the soil is often limited, making fertilization necessary to achieve high yields.
In addition, some soils may lack specific micronutrients like zinc, boron, sulfur, iron, or molybdenum. Applying these nutrients to such soils can significantly improve wheat production. The nutrient requirements of wheat vary throughout its growth stages. Early in the growth cycle, nutrient uptake is low, but it increases gradually, reaching a peak during the reproductive stage before declining again. For example, research from Shandong Agricultural University shows that before the green-up period, wheat absorbs about 17% of its total nitrogen, 11% of phosphorus, and 9.75% of potassium. During the jointing to flowering phase, the absorption of nitrogen, phosphorus, and potassium reaches 72%, 92.57%, and 100%, respectively.
Wheat has a long growth cycle and high yield potential, which means it requires a large amount of fertilizer. However, applying all the fertilizer at once is not efficient, as it may not be fully utilized by the plant. Therefore, fertilization is usually done in stages: basal fertilizer, seed fertilizer, and top dressing. Basal fertilizer is applied before sowing, seed fertilizer is used to support early growth, and top dressing is applied during key growth periods like jointing and heading.
For irrigated wheat, the recommended base fertilizer includes about 3,000 kg of organic manure per acre, along with 5-7 kg of pure nitrogen (N), 6-8 kg of phosphorus pentoxide (Pâ‚‚Oâ‚…), and 4-6 kg of potassium oxide (Kâ‚‚O). Several options are available for application, such as using urea, superphosphate, and potassium chloride, or compound fertilizers like DAP and Sanyuan. The choice depends on soil conditions and previous fertilizer use.
For dryland wheat, the approach is slightly different. It typically involves applying more than 2,000 kg of organic manure and combining nitrogen, phosphorus, and potassium fertilizers to achieve high yields. The target yield is over 300 kg per mu, and the total chemical fertilizer application includes 10-12 kg of nitrogen, 8-10 kg of Pâ‚‚Oâ‚…, and 5 kg of Kâ‚‚O. Most of the fertilizer is applied as a base, with the remaining nitrogen applied later in the spring.
In both cases, it's important to tailor the fertilization plan to local soil conditions and past practices. If certain nutrients are lacking, they should be added accordingly. For example, if the soil is deficient in zinc or boron, small amounts of zinc sulfate and borax can be mixed into the base fertilizer. Similarly, if there's a calcium or sulfur deficiency, calcium superphosphate may be used.
Seed fertilizer plays a crucial role in promoting strong seedling establishment. It should be applied separately from the seeds to avoid damage. Urea and diammonium phosphate are commonly used, often in a 1:1 ratio, and the quantity is generally around 30% of the seed weight.
Top dressing should be timed carefully. In general, it is best applied during the jointing stage when the plant needs more nutrients. However, if the plants are weak or the group is sparse, an earlier application may be beneficial. Watering after top dressing helps improve fertilizer efficiency.
In dryland areas, fertilization should be combined with rainfall. If no rain occurs, urea can be dissolved in water and applied through furrows. A typical application rate is 5-7.5 kg per mu.
Overall, proper fertilization is essential for maximizing wheat yield and quality. Understanding the specific needs of the crop and the soil allows farmers to make informed decisions and apply nutrients efficiently.
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