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According to its fertility characteristics, maize can be divided into three main stages: seedling stage, ear stage and flower stage. From the jointing to the heading stage, it is an important period for the growth of corn vegetative organs, the differentiation of male and female ears, and the simultaneous growth of vegetative growth and reproductive growth. The tassel is extracted to maturity and is the reproductive growth stage of corn. The amount of nitrogen, phosphorus and potassium absorbed by corn is greatly affected by soil, fertilizer, climate and planting methods. Generally speaking, for every 100 kilograms of corn kernels produced, nitrogen (N) needs to be absorbed from the soil by 2.5-4.0 kg. Phosphorus 1.1-1.4 kg, potassium 3.2-5.5 kg, the ratio is 1:0.4:1.3. Among them, each 100 kg of grain produced by spring corn absorbs nitrogen (N) 3.5-4.0 kg, phosphorus 1.2-1.4 kg, potassium 4.5-5.5 kg, the ratio is 1:0.35:1.35; summer corn produces 100 kg of grain for nitrogen absorption (N ) 2.5-2.7 kg, phosphorus 1.1-1.4 kg, potassium 3.2-3.8 kg, the ratio is 1:0.48:1.35; interplanting corn for each 100 kg of grain absorption nitrogen (N) 2.45 kg, phosphorus 1.41 kg, potassium 1.92 kg, The ratio is 1.7:1:1.4. Corn absorbs the most nitrogen in its lifetime, followed by potassium and phosphorus. The absorption of NPK is different in corn at different growth stages. The research data showed that the nitrogen uptake of spring maize seedlings was less, accounting for 2.14% of total nitrogen; the absorption at booting stage was more, accounting for 32.21% of the total; and the flowering period of heading was 18.95% of the total. During the grain formation stage, the absorption amounted to 46.7% of the total. Due to the short growth period, summer maize has a relatively long time to absorb nitrogen and absorbs faster. At the seedling stage, the absorption amounted to 9.7% of the total; the joints absorbed by the joints accounted for 76.19% of the total; the heading to the mature absorption accounted for 14.11% of the total. The absorption of phosphorus by maize is: the amount of spring maize absorbed in the seedling stage is 1.12%, the absorption at the jointing and booting stage accounts for 45.04% of the total, the stage of heading fertilization and grain formation, and the absorption amount accounts for 53.84% of the total. Summer maize also absorbed phosphorus earlier, 10.16% in seedling stage, 62.60% in jointing and booting stage, 17.37% in heading fertilization stage, and 9.51% in grain formation stage. The absorption of potassium by corn is: spring corn is basically similar to summer corn, more than 70% is absorbed before heading, and 30% is absorbed during heading and fertilization. The dry matter accumulation of maize is closely related to the nutrient level. The absorption of nitrogen, phosphorus and potassium all showed less seedling stage, significantly increased the jointing stage, and the fertilizer requirement of the highest peak from the booting stage to the heading stage. Therefore, according to this feature, corn fertilization should be fertilized as much as possible before the peak of fertilizer demand.
1. Spring corn fertilizer application technology
(1) The base fertilizer spring corn is mainly based on base fertilizer, supplemented by topdressing fertilizer; farmyard manure is mainly supplemented by chemical fertilizer; nitrogen fertilizer is the main factor, phosphate fertilizer is supplemented; panicle fertilizer is the main principle, and granular fertilizer is the basic principle of fertilization. The base fertilizer should generally account for about 70% of the total fertilization. Most of the phosphate fertilizer should also be combined with the base fertilizer. Generally, it should be combined with autumn tillage in the first year. When applying the base fertilizer, it should be evenly mixed with the soil, generally 37.5-60 tons of farmyard manure per hectare of base fertilizer. If nitrogen fertilizer is used as the base fertilizer, 375 kg of ammonium bicarbonate or 150 kg of urea can be applied per hectare. Must be applied in depth to prevent nitrogen loss. In the phosphorus-deficient soil, 450-600 kg of calcium phosphate per hectare is applied; in the potassium-deficient soil, 150 kg of potassium chloride per hectare is applied; in the zinc-deficient soil, 15 kg of zinc sulfate heptahydrate is applied per hectare.
(2) Before the spring planting of the seed fertilizer, use a small amount of farmyard manure with a suitable amount of nitrogen or phosphate fertilizer to apply or apply as a corn seed fertilizer.
(3) Topdressing corn fertilization is an important measure for high-yield cultivation of corn. Due to the long growth period of spring maize, the growth of seedlings is slow, and the nutrient absorption is less. Therefore, the spring corn topdressing adopts the "pre-light and heavy" fertilization method, that is, 1/3 of the top dressing is applied before the jointing of the corn. Apply urea 75-150 kg, apply 2/3 of topdressing at the big bell mouth, and apply 150-300 kg of urea per hectare to meet the needs of nutrients in the spikelets, floret differentiation and grain formation stage of maize ears. It was confirmed that the spring corn adopts the "pre-light and heavy" fertilization method, which is 13.3% higher than the "pre-weight and light" fertilization method.
2. Summer corn fertilizer application technology
(1) The base fertilizers in Hebei, Henan, Shandong and other provinces after the wheat harvest, combined with shallow tillage and cockroach, 30-45 tons of high-quality manure per hectare, 600-750 kg of phosphate fertilizer as the base fertilizer. In some places, the straw is directly returned to the field. After the wheat is harvested, the wheat straw is directly applied or harvested, and the sorghum is left as the summer corn base fertilizer. Generally, it is suitable to apply 3000-4500 kg of wheat straw per hectare. In soils with lower fertility, a small amount of nitrogen fertilizer should be used in the application of wheat straw to adjust the carbon to nitrogen ratio and accelerate the decomposition of straw, so that the season can play its due effect.
(2) Topdressing summer corn, due to tight farming time when planting, there are many places where it is impossible to plant corn and apply base fertilizer. However, summer maize seedlings need to absorb a large amount of nutrients from the soil, and the top dressing should adopt the "pre-weight and light" method. 2/3 of the total amount of forced fertilizer is applied in the early stage of jointing, and 1/3 of the large bell mouth is applied, which focuses on the nutrients needed for the differentiation of the ears of maize. According to the results of the national fertilizer net experiment, summer corn yields 5250-6750 kg per hectare, and the urea dosage per hectare is 450-600 kg. According to the "pre-weight and light" topdressing method, 300-375 kg is applied during the jointing stage of the corn. It is better to apply 150-225 kg in the bell mouth period. According to the results of the Crop Research Institute of the Chinese Academy of Agricultural Sciences, the "pre-weight and light-weight" method increased yield by 12.8% compared with the "lighter and lighter" method.
Summer maize topdressing should also consider the distribution of period and topdressing amount in different periods. Therefore, to choose the best application period and dosage, the best yield increase effect will be obtained. According to the experimental results of different topdressing periods of Shandong Agricultural University, 750 kg of ammonium bicarbonate per hectare is applied once in the small trumpet period, producing 7039.5 kg of corn per hectare; 2 times of fertilization, that is, 300 kg of seedlings are applied. In the big bell period, 450 kg is applied, and 7620 kg of corn is produced per hectare; 3 times of topdressing, that is, 225 kg of seedlings, 375 kg of large bells, 150 kg of early flowering, 8085 per hectare kilogram. The application of 2 times increased the yield by 580.5 kg, and the application of 3 times increased the yield by 1045.5 kg, and increased the yield by 14%. It indicates that summer corn has better effect on topdressing.
3. Fertilization of interplanting corn
Interplanting corn is the main planting method for corn in the Huang-Huai-Hai Plain. Since corn is interplanted 25-30 days before wheat harvest, the symbiosis period of the two crops is longer, and the amount of base fertilizer applied is small. The competition for water and fertilizer is more severe in wheat and corn, and it is necessary to apply fertilizer early. According to experiments in Beijing, Hebei, Henan, Shandong and other places, regardless of the variety and location of the intercropped corn, the topdressing is higher than the "pre-weight and light", with an average yield increase of 9.6% to 14.5%.
Corn is one of the main food crops in China. China's North China, Northeast China, and Northwest China are the main areas for planting corn. Due to different natural conditions, the corn planting system is different. How to apply scientific fertilization according to the characteristics of corn growth and fertilizer requirements is very important to increase corn yield.
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