Wheat fertilization
First of all, we should master the law of fertilizer demand.
Winter wheat goes through eight stages: emergence, tillering, overwintering, turning green, jointing, booting, filling and maturity. At different growth stages, the amount and proportion of nitrogen, phosphorus and potassium absorbed are different. To achieve scientific fertilization, we must first find out the nutritional characteristics and fertilizer demand law of wheat.
Before overwintering, winter wheat does not need much nutrients, mainly nitrogen, accounting for about 10%~ 14% of the total nutrient absorption, and the ratio of phosphorus and potassium is less than 10%. But at this time, the wheat seedlings are small, the roots are weak, and they are sensitive to nutrient supply, so it is necessary to ensure nutrient supply. After overwintering, with the increase of temperature and wheat population, nutrient absorption increased rapidly until heading and flowering, especially potassium, which stopped absorbing after flowering. The peak of nutrient absorption of winter wheat is from jointing stage to flowering stage, and the total nutrient requirements of 55% nitrogen, 80% phosphorus and 90% potassium in the whole growth period are at this stage. After flowering to maturity, it still needs to absorb 28% nitrogen and a very small amount of phosphorus, and basically no longer absorbs potassium.
Generally speaking, about two-thirds of the nutrients absorbed by wheat in high-yield fields, especially nitrogen, come from soil. Therefore, improving soil fertility is the key measure to achieve sustained high yield of wheat. The purpose of fertilization is not only to provide nutrients for the high yield of crops in this season, but more importantly, to supplement the soil nutrients absorbed by the growth of crops in this season and lay the foundation for the high yield of crops in the next season.
According to the research, every 100 kg of winter wheat seeds should absorb nitrogen (N)3. 1 kg, phosphorus (P2O5) 1. 1 kg and potassium (K2O)3.2 kg, and the ratio of the three is about 2.8 ∶/kloc-0. With the increase of yield level, the total absorption of nitrogen, phosphorus and potassium also increased accordingly.
The accumulation and distribution of nutrients in winter wheat after absorption at different growth stages mainly change with the transfer of growth centers. Nitrogen absorbed at seedling stage is mainly used for the establishment of vegetative organs such as tillers and leaves, mainly used for stems and young panicles from jointing to flowering, and mainly flows to grains after flowering; The accumulation and distribution of phosphorus are basically similar to that of nitrogen, but the absorption is far less than that of nitrogen, and the transfer of potassium to grain is very small, and more than 80% is retained in straw.
Second, seven major problems must be avoided.
Summarizing the present situation of winter wheat fertilization in various places, we can find seven problems that farmers should pay attention to avoid.
First, the amount of organic fertilizer application is insufficient. With the improvement of rural conditions, farmers' enthusiasm for accumulating farmyard manure has decreased, and the aquaculture industry has gradually changed from decentralized farming to large-scale farming. The amount of livestock manure decreased by farmers, and the utilization rate of livestock manure in large-scale farming was not high, which led to insufficient application of organic fertilizer.
Second, the structure of chemical fertilizer application is unreasonable. Many farmers do not consider the soil nutrient content and wheat yield level when determining the amount of fertilization, and the phenomenon of blind fertilization is more serious. Especially with the increase of wheat total output, the amount of chemical fertilizer is also increasing, in which the amount of nitrogen and phosphorus fertilizer is generally excessive, which leads to the increase of ineffective tillers, the thinning of stems, the decline of lodging resistance, cold resistance and disease resistance, and often suffers from freezing injury in winter, cold in late spring, and the aggravation of pests and diseases in the middle and late period, which is easy to lodging, thus affecting the yield.
Third, return the straw to the field without adding nitrogen fertilizer. Returning straw to the field is an effective measure to solve the shortage of organic fertilizer, but many farmers have not mastered this technology and have not applied nitrogen fertilizer after returning straw to the field. In the process of straw decay, a certain amount of nitrogen should be absorbed and consumed. If nitrogen fertilizer is insufficient, straw rot and wheat seedling growth will compete for nitrogen, resulting in "yellow weak seedlings"
Fourth, the fertilization method is unreasonable. There is a "one shot" fertilization method in some middle and low yield fields or poor soil areas in winter wheat producing areas, that is, all chemical fertilizers are applied to the soil at one time during the soil preparation and sowing period, and no topdressing is required during the growth period. On the one hand, due to the limitation of irrigation conditions, fertilizer and water are not coordinated, and "one shot" affects fertilizer efficiency; On the other hand, the nitrogen requirement of winter wheat before turning green is less than 30%, but in many areas, nitrogen fertilizer is applied once when turning green, 40%~50%, or even as high as 70%.
The fifth is improper topdressing period. Topdressing in most winter wheat areas is carried out in the turning green period, and early spring is the key period for spring tillering and basal internode elongation of wheat. Premature topdressing often leads to too many ineffective tillers, too large wheat field population, too thin stems and too long basal internodes. It will also cause diseases such as field closure, poor ventilation and light transmission, powdery mildew and so on in the middle and late stage of wheat growth, which will lead to lodging easily in the later stage and affect the yield and quality of wheat.
The sixth is to ignore the application of trace element fertilizers. Trace elements are also essential nutrients for the growth and development of winter wheat. Lack of some trace elements in winter wheat will lead to poor growth and yield reduction. In recent years, with the increase of wheat yield, the consumption of trace elements in soil has increased, and many plots have been short of trace elements, especially those without organic fertilizer or with insufficient organic fertilizer.
Seventh, blindly apply new fertilizers. At present, the quality of various new fertilizers on the market is uneven. Some of them are not high in scientific and technological content and over-hyped, which leads to farmers' unclear understanding and blind application under the condition of unclear fertilization direction and application method, resulting in reduced production and economic losses.
Three to five measures to deal with it.
Farmers can actively respond to existing problems from five aspects:
First, increase the application of organic fertilizer and advocate the coordinated application of organic fertilizer and chemical fertilizer. In winter wheat-summer corn double cropping areas, vigorously promote corn straw returning to the field and wheat high stubble, and study and formulate practical and effective operating rules for returning corn straw to the field.
The second is to reduce the amount of nitrogen and phosphorus fertilizer and implement balanced fertilization. According to the characteristics of soil nutrient resources and wheat yield level, the reasonable application amount of nitrogen and phosphorus fertilizer is determined. According to the supply of soil potassium, potassium fertilizer should be applied in a targeted manner.
Third, the nitrogen fertilizer should be applied by stages, and the nitrogen fertilizer should be moved back appropriately. Winter wheat moved to jointing stage after topdressing in spring, and the proportion of topdressing was appropriately increased in middle and high yield fields.
Fourth, rational application of trace element fertilizers. In areas with high yield plots and insufficient application of organic fertilizer, trace elements such as zinc, boron and manganese should be supplemented in a timely and reasonable manner according to the results of soil investigation and fertilizer effect reaction.
Fifth, pay attention to the application of foliar fertilizer. In some winter wheat areas, there is a phenomenon that the late dry-hot wind climate affects the yield. Combined with the prevention of dry hot wind, attention should be paid to spraying foliar fertilizer in the later stage.
Fourth, there are standards for scientific fertilization.
Fertilization amount, fertilization method and fertilization period of winter wheat should be determined according to the yield level of wheat fields with different fertility. On the basis of rational application of organic fertilizer, the dosage of chemical fertilizer (mainly nitrogen, phosphorus and potassium) can refer to the following standards:
(1) For super-high-yield fields with a yield of more than 500 kg per mu, nitrogen (N) 14~ 16 kg, phosphorus (P2O5)7~8 kg and potassium (K2O)6~8 kg should be applied per mu;
(2) High-yield fields with 400-500 kg per mu should be applied with nitrogen (N) 12- 14 kg, phosphorus (p2o 5)6-7 kg and potassium (K2O)5-6 kg/mu;
(3) Nitrogen10-12kg, phosphorus 4-6kg, and potassium (K2O) 4-6kg/mu should be applied to low and medium yield fields with 300-400kg/mu;
(4) For low-yield fields with an yield of less than 300kg/mu, apply 8 8- 10/0kg of nitrogen, 3-5kg of phosphorus (P2O5) and 2-4kg of potassium (K2O) per mu.
Organic fertilizer, phosphorus and potassium fertilizer and 40%~50% nitrogen fertilizer are used as base fertilizers, which are evenly spread on the surface of wheat field before soil preparation, and then rotated or ploughed to make the fertilizer and topsoil fully mixed; The remaining 50%~60% nitrogen fertilizer should be topdressing with water at the jointing stage of winter wheat in the following spring (mid-March to late March), and applied deep between wheat rows, and then covered with soil and watered to improve fertilizer utilization rate and reduce nitrogen volatilization loss. Topdressing nitrogen fertilizer in high-yield wheat fields can be divided into two stages, topdressing at jointing stage is 30%~40%, topdressing at heading and flowering stage is 10%~20%, which has a good effect on strengthening wheat filling intensity and further improving wheat yield.
In addition, attention should also be paid to "one spraying and three prevention", and the mixed solution of bactericide, insecticide, plant growth regulator and foliar fertilizer should be sprayed on wheat leaves during the filling period to prevent diseases, insects and premature aging and improve the filling effect.