Nitrogen fertilizer efficiency is constrained by climate, soil, crop, nutrient balance, fertilization techniques and other cultivation management measures. Therefore, the rational application of nitrogen fertilizer should be based on the crop yield, soil properties, nitrogen fertilizer varieties and other conditions, in order to fully play the role of nitrogen fertilizer to increase production and improve its economic benefits.
(1) Reasonable distribution of nitrogen fertilizer
The commonly used nitrogen fertilizer varieties are all available nitrogen fertilizers, which have obvious yield-increasing effects on different soils and crops. However, due to the different nature of chemical fertilizers, the yield-increasing effects on different soils and crops are also different.
1. Distribution of nitrogen fertilizer due to soil
Ammonium nitrate is easily leached and denitrified, so it is rarely used in paddy fields and areas with large rainfall in southern China, especially in long-term flooded paddy fields.
In the north of China, there are many drylands, better ventilation, less rainfall, and more irrigation, which causes less loss of leaching and denitrification of ammonium nitrate. In calcareous and alkaline soils, the loss of nitrogen is mainly the volatilization of ammonia. Therefore, in the case of deep application of nitrogen fertilizer, the fertilizer effect of ammonia nitrogen fertilizer (including urea) and nitrate nitrogen fertilizer is not much different, but in dry land with bad moisture or cold climate (low urea enzyme activity, affecting urea conversion), nitric acid The effect of ammonium is better than that of urea and ammonium nitrogen. Therefore, ammonium nitrate should be mainly used on dry crops.
Ammonium sulfate, ammonium chloride and the like are physiologically acidic fertilizers, and are more suitable for use in calcareous soils. If applied in acid soil for a long time, add lime or organic fertilizer to enhance buffer capacity and neutralize soil acidity. However, ammonium sulfate is applied on rice fields for a long time. Because of the large amount of hydrogen sulfide or ferrous sulfate, it is harmful to rice roots under anoxic conditions. Long-term application on calcareous soil is easy to form a large amount of calcium sulfate, resulting in Soil compaction. Therefore, it is not appropriate to apply a single ammonium sulfate for a long time on these plots, and it should be applied in combination with other nitrogen fertilizers.
2. Distribution of nitrogen fertilizer due to crops
Crops have a certain selectivity for the form of nitrogen fertilizer and its secondary components. Ammonium chloride contains chloride ions, which can not be applied on tobacco. Otherwise, it will affect its flammability, easy to "extinguish" and have poor odor. Chlorine-sensitive crops such as tea, grape, watermelon, citrus, potato, sugar beet and sugar cane should be strictly controlled. The amount of ammonium chloride used. If the amount of ammonium chloride is too much, the starch content of tubers, roots and crops will decrease, because chloride ions can promote the hydrolysis of carbohydrates and affect the quality. In addition, potato sulphur and beet sodium have a good reaction to the application of ammonium sulfate and sodium nitrate respectively. Cereal crops such as wheat and corn are equally effective for ammonium nitrogen fertilizer and nitrate nitrogen fertilizer. Rice lacks reductase at its roots, has a poor ability to utilize nitrate nitrogen, and responds well to ammonium nitrogen. Potato-based starch-containing crops also prefer ammonium nitrogen. The application of ammonium nitrate or nitrate nitrogen and ammonium nitrogen in tobacco, hemp and sugar beet is beneficial to the improvement of product quality. For example, if ammonium nitrate is applied to tobacco, it will promote the growth of leaves due to the effect of nitrate nitrogen fertilizer. The ammonium nitrogen is adsorbed by soil colloid, and the fertilizer efficiency is stable, which is beneficial to the maturity of the later leaves. The thickness of the leaves is suitable, the color is good, and the taste is pure.
(2) Combined application of nitrogen fertilizer and phosphorus and potassium fertilizer
With the development of agricultural production, the nutrients taken by the crops from the soil are increasing, and people return less soil. The soil often has several nutrients and the supply of insufficient crops requires a balanced supply of multiple nutrients. According to the current soil nutrient status in China, most of the soil is lacking in nitrogen and phosphorus nutrition, while soil potassium deficiency is becoming more and more serious in the south. Therefore, at present, the combination of nitrogen and phosphorus is mainly considered in the north. In the south (including some high-yield and potassium-deficient plots in the north), the combined application of nitrogen and phosphorus and potassium, and the combined application of nitrogen and organic fertilizers should be considered to improve the fertilizer efficiency of nitrogen fertilizer. .
1 Nitrogen fertilizer and phosphorus fertilizer combined application of soil nitrogen and phosphorus are lacking and potassium is rich, generally single nitrogen fertilizer or phosphate fertilizer has increased yield, but the yield increase is not large. On this plot, if nitrogen is combined with phosphorus, a better yield increase effect can be obtained. The results of the experiment on the soil of nitrogen deficiency, phosphorus deficiency and potassium-rich in Feixiang County of Hebei Academy of Agricultural Sciences: 33 kg of wheat per acre, 48 kg of phosphate per plant, and the same amount of nitrogen and phosphorus increased by 109 kg. It is 81 kilograms more than the combined yield of nitrogen and phosphorus, and 28 kilograms more. This phenomenon is called the conjunction between nitrogen and phosphorus, also known as interaction. It can be seen from the above that nitrogen fertilizer is a "potentiator" for phosphate fertilizer, and phosphate fertilizer is a "potentiator" for nitrogen fertilizer. In this type of area and soil, it is reasonable to apply nitrogen and phosphorus together. One of the main measures of administration.
2 Nitrogen Fertilizer and Phosphorus and Potassium Fertilizer According to the results of the rice field experiment in the Huaiji and Nanhai areas of the Guangdong Academy of Agricultural Sciences in 1980, nitrogen and phosphorus, nitrogen and potassium, nitrogen and phosphorus and potassium were used in the NPK-deficient land. Combined application, the yield was increased compared with the single application of nitrogen fertilizer, and the combined effect of nitrogen and phosphorus and potassium fertilizers was the most significant. This kind of plot is suitable for the application of nitrogen fertilizer and phosphorus and potassium fertilizer. On the P-rich and nitrogen-deficient plots, the combined application of nitrogen and potassium, nitrogen and phosphorus and potassium increased the yield of rice by 47% and 49%, respectively. In this case, nitrogen and potassium can be used together.
In addition, organic fertilizer contains more phosphorus and potassium. In the case of deficiency of phosphorus or potassium fertilizer or insufficient dosage, the application of organic fertilizer can also increase the yield increase effect of nitrogen fertilizer, but it is necessary to increase the application rate of nitrogen fertilizer to prevent crop nitrogen deficiency. Because soil microbes are in the process of decomposing mature organic fertilizers, in addition to the nitrogen in organic fertilizers, some nitrogen in the soil is often consumed, resulting in short-term nitrogen deficiency in the soil.
(3) Nitrogen application rate
China's nitrogen fertilizer consumption is large, accounting for more than 66% of total fertilizer use. Therefore, if the amount of nitrogen fertilizer is appropriate, it can reduce waste, which is one of the key links of rational fertilization. The application rate of nitrogen fertilizer is closely related to crop yield, crop type, soil fertility, climatic conditions, and application of phosphorus and potassium fertilizers and organic fertilizers.
1 Nitrogen application rate and crop yield Nitrogen application rate is affected by many factors, but due to the general lack of soil nitrogen in China and the small residual effect of nitrogen fertilizer in the soil, the relationship between nitrogen application rate and crop yield is very close, and the crop yield is more High, the amount of nitrogen fertilizer should be increased accordingly. This method is also called "to produce nitrogen, within the range of nitrogen fertilizer use, and then to hate according to local specific conditions, the upper or lower limit of the amount of choice.
2 The amount of nitrogen fertilizer and the variety of crops The demand for nitrogen in various crops is different. Under the same yield, oil, raisin vegetables, cotton, Spring corn, winter wheat, summer corn, rice, etc. need more nitrogen, silage corn and pasture also need more nitrogen; peanuts, soybeans and Although legume green manure and other crops require more nitrogen in their lifetime, most of them rely on rhizobium to fix nitrogen in the air. It is only necessary to apply a small amount of nitrogen fertilizer at the early stage of growth to promote nodule formation. If excessive application of nitrogen fertilizer, it will hinder nodule formation. To reduce nitrogen fixation; starch and sugar crops such as sweet potato, potato, sugar beet, sugarcane, etc. do not need to apply too much nitrogen fertilizer. Excessive nitrogen will affect the synthesis of starch and sugar, and reduce product quality; tobacco can not be applied too much. Nitrogen fertilizer, excessive nitrogen, thick leaves, poor taste of tobacco, such plants need more phosphorus and potassium fertilizer. The requirements for nutrients of different varieties of the same crop are also different. Some varieties are resistant to fertilizer and have a large potential for increasing production, and the amount of fertilizer can be appropriately increased. For varieties that are not resistant to fertilizer, they should not be applied more. The amount of nitrogen should be properly controlled to avoid the stagnation.
The reasonable amount of nitrogen fertilizer should take into account both production and net income. Within a certain range of nitrogen fertilizer application, with the increase of nitrogen application rate, the crop yield is also gradually increased, but the yield increase benefit per unit of nitrogen fertilizer is reduced. This is the phenomenon of “decreasing returns†in fertilization. According to 1981-1983 national fertilizer The test results of "the relationship between different nitrogen fertilizer dosage and fertilizer efficiency" conducted by the test network showed that in the case of medium nitrogen application rate of 6-10 kg per mu, the yield per 10 kg of nitrogen increased by 10 to 12 kg, and the nitrogen utilization rate was 35% to 45. %, although the yield increase per unit of nitrogen fertilizer decreases with the increase of the amount of nitrogen fertilizer, as long as the added fertilizer price is lower than the price of the increased product, the higher yield and the largest net income can be obtained. The reasonable application rate of nitrogen fertilizer is also called the optimal nitrogen application rate.
Nitrogen fertilizer can be used as base fertilizer, seed fertilizer and top dressing. Mastering the proper application period of nitrogen fertilizer plays an important role in improving yield and fertilizer utilization and reducing environmental pollution. Base fertilizer, also known as base fertilizer, is a fertilizer applied during land preparation and tillage. Adequate base fertilizer is the basis for obtaining high yield. When applying organic fertilizer, phosphate fertilizer or phosphorus and potassium fertilizer, nitrogen fertilizer can be used to meet the nutrient needs of crop seedlings, which is beneficial to strong seedlings and increase the rate of ear formation. The amount of nitrogen fertilizer used as base fertilizer is related to crop, soil and nitrogen fertilizer varieties. Short-growing crops, such as northern wheat, late-wheat, spring wheat, and southern double-season rice, are the key to increasing yield. Generally, the base fertilizer should be reapplied, and the amount of fertilizer applied can account for 70% to 80% of the total amount of nitrogen fertilizer applied. The medium and low-yield fields can also be applied at one time, no longer topdressing. In arid areas where there is little rain and no irrigation conditions, the effect of top dressing is often small, and it is advisable to use a single base fertilizer.
Long-growing crops, such as spring rice, spring maize, winter wheat, cotton, and southern rice crops in the north, generally have a growth period of about 150 days. Therefore, it is necessary to prevent the early growth and the late de-fertilization. The method of topdressing and weighting, the amount of base fertilizer is 4-6 kg per mu of nitrogen fertilizer, accounting for 40% to 60% of the nitrogen fertilizer amount in the whole growth period. For some economic crops such as sugar cane, Brassica napus, cabbage Chinese cabbage, etc., the yield is high, and the fertilizer is required to be applied in many times. The proportion of base fertilizer is relatively low, such as spring planting sugar cane, base fertilizer with nitrogen fertilizer (N) 2 to 3 kg per mu, cabbage-type rapeseed with nitrogen fertilizer (N) kg per mu, cabbage Chinese cabbage often do not use nitrogen fertilizer to apply sufficient organic fertilizer And phosphorus and potassium fertilizers can be used as the base fertilizer. These crops use nitrogen fertilizer as the base fertilizer, which accounts for nearly 30% of the total growth period.
Peanut, soybean and other legumes have no formation or a small number of nodules during the pupal period, and the nitrogen-fixing ability is weak. Therefore, the basic fertilizer should also be paid attention to. The amount of nitrogen fertilizer per mu (N) is 2 to 3 kg, accounting for about 60% of the nitrogen fertilizer in the whole growth period. %the above.
The base fertilizer and base fertilizer of perennial crops such as fruit trees and tea trees are separated. The base fertilizer refers to the fertilizer applied to the perennial crops in combination with deep tillage and soil change. The main function of the base fertilizer is to increase the soil organic matter and promote the improvement of soil physical and chemical properties, so as to lay a good soil foundation for the subsequent crop growth. Generally, delayed nutrients such as organic fertilizer are mainly applied. The base fertilizer of perennial crops often has many forms. For example, tea trees have two forms, one is applied when cuttings are planted or seeds are broadcasted live, and the other is applied to tea gardens every autumn and winter, which is called the base fertilizer of tea trees. The tea garden base fertilizer is compounded with organic fertilizer and phosphorus-potassium fertilizer. When the organic fertilizer is insufficient, nitrogen fertilizer (N) is applied for 2 to 3 kg per mu.
The principle of “fertilizer and less application, less application of thin soil, less application of sandy soil and more application of cohesive soil†should be mastered. The amount of clay base fertilizer can exceed 50% of the total fertilizer application, 50% of loam and 30% of sand. About % is appropriate. Sandy soil is easy to leak, especially in paddy fields and rainy areas. Ammonium bicarbonate and ammonia water are volatile and should be used as base fertilizer. Deep application can reduce the loss of volatilization. Nitrogen fertilizers with stable properties such as ammonium sulfate, urea and ammonium nitrate are left as top dressings or seed fertilizers, which saves labor and reduces nitrogen losses. In addition, when applying the mature organic fertilizer as a seed fertilizer, the amount of nitrogen fertilizer should also be appropriately increased.
Fertilizer refers to the fertilizer applied during sowing or transplanting. Generally, no fertilizer is needed when applying the base fertilizer. If there is no base fertilizer or insufficient base fertilizer, a small amount of nitrogen fertilizer can be used for dry crops such as wheat, corn, millet and sorghum. As a seed fertilizer, the sample can also promote the early development of the young cub, and the yield increase effect is very obvious. However, when the wheat is directly mixed with ammonium sulfate, the seed and the fertilizer should be dry, and it must be mixed with the mixture, and the ammonium sulfate per mu. Do not use more than 5 kg. Other nitrogen fertilizers should avoid direct contact with seeds and prevent the risk of seed germination due to high fertilizer concentration and high hygroscopicity. When the amount of fertilizer is large, it should be applied by ditch or acupoint.
The urea concentration is high, and after changing to ammonium nitrogen, the mobility is not as good as that of nitrate nitrogen. Therefore, the large amount and concentrated application may cause local alkalization of the soil and burn seedlings. Especially urea with a higher biuret should be used with care. Therefore, the urea ditch should also control the dosage. We found that when planting corn in the northern region, there was a burning phenomenon due to the application of urea about 20 kg in the ditch. Cotton seeds are most sensitive to urea. After soaking seeds, the cotton seeds cannot be mixed with urea, otherwise the seedlings will be affected.
Topdressing is also called composting. According to the demand for nutrients in crops, it is necessary to supplement the deficiency of base fertilizer and seed fertilizer to prevent fertilizer from being applied during the period of crop growth. The number, period and dosage of top dressing are mainly based on the fertilizer characteristics of the crop.
Crop topdressing with short growth period, such as double-season rice in the south, wheat in late rice, late-season rice in spring, spring wheat, etc. When the base fertilizer and seed fertilizer are insufficient, the topdressing should be early and late, and the rice should generally be applied about 7 days after transplanting. After the tillering, the nitrogen fertilizer (N) is 2~4 kg per mu, and the summer corn without the base fertilizer and seed fertilizer can be applied to the joint fertilizer. The nitrogen fertilizer (N) is 4-5 kg ​​per mu. Long-growing crop topdressing, such as spring maize, winter wheat, single-season rice, and southern mid-season crops in the north, have longer growth periods and higher yields. In the case of applying base fertilizer, nitrogen can be applied per acre (N). 4 to 6 kg, generally divided into two top dressings, the first time in the tillering stage or jointing stage, should be re-chased; the second time is the panicle fertilizer, if the crop is good, it can be applied less or not.
There are many types of cash crops and different fertilizer characteristics, so the topdressing is different. Such as spring planting sugar cane, although the amount of nitrogen fertilizer should not be too much, but also divided into seedling fertilizer, strong fertilizer, joint fertilizer and strong tail fertilizer and many other top dressing. Zhuangfei fertilizer and jointing fertilizer should be applied with nitrogen fertilizer (N) 3 to 4 kg per mu. The seedling fertilizer and the strong tail fertilizer are chased 2 to 3 kg respectively. Another example is the long growth period of cotton, which is generally divided into four parts: seedling fertilizer, bud fertilizer, flower bell fertilizer and topping fertilizer. The seedling fertilizer should be applied early, using about 1 kg of nitrogen fertilizer per mu (N), combined with cultivating after the seedling is fixed; the bud fertilizer should be applied stably, and the nitrogen fertilizer per mu (N) is 1-2 kg (the amount of nitrogen fertilizer in the northern cotton field should be more than that in the south). If the cotton field grows vigorously, it should be applied late or less. Flower bell fertilizer should be re-applied, using 3 to 4 kilograms of nitrogen fertilizer per acre. It is usually applied when 1 to 2 large peaches are held in the lower part of the cotton plant. If the cotton grows longer, the amount of fertilizer can be reduced. The top-top fertilizer should be applied skillfully, and the nitrogen fertilizer per acre should be 0.5~1 kg, which can prevent premature aging of cotton, multi-ringing, and increase the weight of bolls and clothes. If the bottom fertilizer is sufficient, the early topdressing or the cotton plant does not produce premature aging, there is no need to cover the top fertilizer to avoid its late maturity. Perennial crop topdressing is more complicated than top dressing per year. Need to apply fertilizer several times, such as tea garden topdressing more than 4 times a year, according to tea varieties and yields.
(4) Application method of nitrogen fertilizer
In order to reduce the loss of nitrogen leaching, volatilization and denitrification, the fertilization method should be considered: the nitrogen fertilizer should be applied to the soil at a certain depth; the ammonium nitrogen fertilizer cannot be mixed with the alkaline substance because the alkaline substance can accelerate The ammonium nitrogen is decomposed and volatilized; the soil should maintain a good moisture when fertilizing.
The application method of the base fertilizer, the solid nitrogen fertilizer and the ammonia water are applied differently in the dry land and the paddy field. Dryland base fertilizers, such as wheat and corn, can be combined with cultivated land. The solid fertilizer is evenly spread on the ground, and then ploughed into the soil, and it can be turned over with the stalks. The depth of most fertilizers is 10-15 cm.
Fertilization of paddy fields generally does not advocate the application of ammonium nitrate, and other solid fertilizers can be used. The method of fertilizing is to spread the fertilizer on the wet soil after the plow is turned over, and then turn the fertilizer into the soil layer, and then sown or transplanted by pouring the water and ploughing the ground. Urea is easily leached with water, so the soil to which urea is applied should be irrigated for 5 to 7 days after urea is converted to ammonium carbonate. Another method of applying the paddy field base fertilizer is to spin the ploughing and then transplant the stalk after the ploughing and ploughing of the paddy field. This method is called “full layer deep application†and can turn most of the fertilizer into about 10 cm deep. In the reducing layer, the fertilizer effect is very good.
The method of deep application of paddy field is to pour shallow water immediately after plowing or ploughing the field. It is not advisable to apply nitrogen fertilizer. Generally, it is 2 to 3 kg per mu, and then simmered for 1 to 2 times. After the flattening is flattened, it can be inserted. The fertilizer is evenly distributed in the soil layer about 7 cm deep, which not only acts as a noodle fertilizer, but also reduces the leaching loss of nitrogen. When urea is used as a noodle fertilizer, it is not possible to release water in the process of dumping.
Ammonia water is applied differently than solid nitrogen fertilizer. The commonly used method in dry land is to use the "plowing bottom ammonia method" to install the ammonia water in the ammonia water tank on the tractor frame, and to introduce the ammonia water to the back of the plough through the plastic pipe, and evenly apply the ammonia water to the furrow while cultivating the land. If you use the animal power to cultivate the land, you can use ammonia water or a back ammonia water tank, and then apply it along the furrow. Then the cultivated land is covered with soil, so that the ammonia water can be applied to the soil layer of about 15 cm. The commonly used method in paddy fields is the “bottom fertilizer application methodâ€, which is to fill a thin layer of water in the field, mix the ammonia water and the muddy water evenly, apply it to the field surface, then plow the field, and then transplant the rice. In addition, it is also possible to apply ammonia water after watering and mulching, and then use a small tractor to rot the plough, and evenly plough the ammonia into the soil layer, and then mix it and then transplant it.
Application method of top dressing When ammonium bicarbonate, ammonium sulfate, urea, ammonium chloride and ammonium nitrate are topdressed on the dry land in the north, the wheat, millet and other seed crops can be ditched, that is, the ditch is about 7 cm deep between the crop rows. Apply fertilizer along the ditch, and then cover the soil. For the medium-crop crops such as corn, sorghum, cotton, etc., the method of “point application†is adopted, that is, 7 to 10 cm beside the plant, and a small hole of 7-10 cm is dug, and the fertilizer is spread. Cover the soil. Watering should be done immediately after fertilization in the dry season, so that the fertilizer effect can be exerted.
It is not advisable to use ammonium nitrate in paddy field topdressing. Other fertilizers should be drained from the field before fertilization. After applying fertilizer, combine with cultivating and weeding to carry out the field, so that the fertilizer and soil mix and mix, evenly distributed in the soil layer of 7-10 cm. Urea should be hydrolyzed by soil. Only after being absorbed by the crop. Therefore, the top dressing should be 3 to 5 days ahead of other nitrogen fertilizers, and the irrigation should also be carried out 5 days after the urea application. Although the deep application of the ball fertilizer has a good yield increase effect, it is more costly.
Ammonia water is used as a top dressing method in the north dry field. The ditch method generally uses a traction ammonia water fertiliser, which is towed by one animal, one person is fertilized by a fertiliser, the other is then covered with soil, and the ammonia water is diluted 5 to 10 times, the depth and distance of fertilization. It is appropriate to use about centimeters of each plant. Ammonia water is used for topdressing in paddy fields. Generally, it is applied by filling method. Before the application, the water in the field is drained, and the container of ammonia water is placed on the mouth of the ditch. The siphon principle is applied to the bottom of the irrigation ditch by a small rubber tube, and the brick is used to stand. Recirculation is caused at the entrance of the furrow, so that the ammonia water is mixed with the irrigation water before entering the field, and then flows into the rice field. This method can also be used for irrigated land in dry fields.
Top dressing refers to the force method of supplying nutrients to crops by spraying fertilizer on the foliage. The concentration of urea applied is 1% to 2% for rice, wheat and grass, 1% for vegetable and rai, about 0.5% for fruit trees, 0.2% for flowers, forest seedlings, strawberries, greenhouse cucumbers and seedlings in hot seedlings. . About 1 kg of urea per acre. Spray once every 7 to 10 days, usually 2 times, and the spraying time is better in the evening or early morning. The crop growth period and adult fruit trees can increase the spraying concentration appropriately. If there is no nitrogen deficiency in the late crop, no urea is required to be sprayed by leaves. Foliar application of fertilizer is particularly effective for crops with root growth barriers and absorptive capacity, but it is an auxiliary fertilization and cannot replace root fertilization.
(1) Reasonable distribution of nitrogen fertilizer
The commonly used nitrogen fertilizer varieties are all available nitrogen fertilizers, which have obvious yield-increasing effects on different soils and crops. However, due to the different nature of chemical fertilizers, the yield-increasing effects on different soils and crops are also different.
1. Distribution of nitrogen fertilizer due to soil
Ammonium nitrate is easily leached and denitrified, so it is rarely used in paddy fields and areas with large rainfall in southern China, especially in long-term flooded paddy fields.
In the north of China, there are many drylands, better ventilation, less rainfall, and more irrigation, which causes less loss of leaching and denitrification of ammonium nitrate. In calcareous and alkaline soils, the loss of nitrogen is mainly the volatilization of ammonia. Therefore, in the case of deep application of nitrogen fertilizer, the fertilizer effect of ammonia nitrogen fertilizer (including urea) and nitrate nitrogen fertilizer is not much different, but in dry land with bad moisture or cold climate (low urea enzyme activity, affecting urea conversion), nitric acid The effect of ammonium is better than that of urea and ammonium nitrogen. Therefore, ammonium nitrate should be mainly used on dry crops.
Ammonium sulfate, ammonium chloride and the like are physiologically acidic fertilizers, and are more suitable for use in calcareous soils. If applied in acid soil for a long time, add lime or organic fertilizer to enhance buffer capacity and neutralize soil acidity. However, ammonium sulfate is applied on rice fields for a long time. Because of the large amount of hydrogen sulfide or ferrous sulfate, it is harmful to rice roots under anoxic conditions. Long-term application on calcareous soil is easy to form a large amount of calcium sulfate, resulting in Soil compaction. Therefore, it is not appropriate to apply a single ammonium sulfate for a long time on these plots, and it should be applied in combination with other nitrogen fertilizers.
2. Distribution of nitrogen fertilizer due to crops
Crops have a certain selectivity for the form of nitrogen fertilizer and its secondary components. Ammonium chloride contains chloride ions, which can not be applied on tobacco. Otherwise, it will affect its flammability, easy to "extinguish" and have poor odor. Chlorine-sensitive crops such as tea, grape, watermelon, citrus, potato, sugar beet and sugar cane should be strictly controlled. The amount of ammonium chloride used. If the amount of ammonium chloride is too much, the starch content of tubers, roots and crops will decrease, because chloride ions can promote the hydrolysis of carbohydrates and affect the quality. In addition, potato sulphur and beet sodium have a good reaction to the application of ammonium sulfate and sodium nitrate respectively. Cereal crops such as wheat and corn are equally effective for ammonium nitrogen fertilizer and nitrate nitrogen fertilizer. Rice lacks reductase at its roots, has a poor ability to utilize nitrate nitrogen, and responds well to ammonium nitrogen. Potato-based starch-containing crops also prefer ammonium nitrogen. The application of ammonium nitrate or nitrate nitrogen and ammonium nitrogen in tobacco, hemp and sugar beet is beneficial to the improvement of product quality. For example, if ammonium nitrate is applied to tobacco, it will promote the growth of leaves due to the effect of nitrate nitrogen fertilizer. The ammonium nitrogen is adsorbed by soil colloid, and the fertilizer efficiency is stable, which is beneficial to the maturity of the later leaves. The thickness of the leaves is suitable, the color is good, and the taste is pure.
(2) Combined application of nitrogen fertilizer and phosphorus and potassium fertilizer
With the development of agricultural production, the nutrients taken by the crops from the soil are increasing, and people return less soil. The soil often has several nutrients and the supply of insufficient crops requires a balanced supply of multiple nutrients. According to the current soil nutrient status in China, most of the soil is lacking in nitrogen and phosphorus nutrition, while soil potassium deficiency is becoming more and more serious in the south. Therefore, at present, the combination of nitrogen and phosphorus is mainly considered in the north. In the south (including some high-yield and potassium-deficient plots in the north), the combined application of nitrogen and phosphorus and potassium, and the combined application of nitrogen and organic fertilizers should be considered to improve the fertilizer efficiency of nitrogen fertilizer. .
1 Nitrogen fertilizer and phosphorus fertilizer combined application of soil nitrogen and phosphorus are lacking and potassium is rich, generally single nitrogen fertilizer or phosphate fertilizer has increased yield, but the yield increase is not large. On this plot, if nitrogen is combined with phosphorus, a better yield increase effect can be obtained. The results of the experiment on the soil of nitrogen deficiency, phosphorus deficiency and potassium-rich in Feixiang County of Hebei Academy of Agricultural Sciences: 33 kg of wheat per acre, 48 kg of phosphate per plant, and the same amount of nitrogen and phosphorus increased by 109 kg. It is 81 kilograms more than the combined yield of nitrogen and phosphorus, and 28 kilograms more. This phenomenon is called the conjunction between nitrogen and phosphorus, also known as interaction. It can be seen from the above that nitrogen fertilizer is a "potentiator" for phosphate fertilizer, and phosphate fertilizer is a "potentiator" for nitrogen fertilizer. In this type of area and soil, it is reasonable to apply nitrogen and phosphorus together. One of the main measures of administration.
2 Nitrogen Fertilizer and Phosphorus and Potassium Fertilizer According to the results of the rice field experiment in the Huaiji and Nanhai areas of the Guangdong Academy of Agricultural Sciences in 1980, nitrogen and phosphorus, nitrogen and potassium, nitrogen and phosphorus and potassium were used in the NPK-deficient land. Combined application, the yield was increased compared with the single application of nitrogen fertilizer, and the combined effect of nitrogen and phosphorus and potassium fertilizers was the most significant. This kind of plot is suitable for the application of nitrogen fertilizer and phosphorus and potassium fertilizer. On the P-rich and nitrogen-deficient plots, the combined application of nitrogen and potassium, nitrogen and phosphorus and potassium increased the yield of rice by 47% and 49%, respectively. In this case, nitrogen and potassium can be used together.
In addition, organic fertilizer contains more phosphorus and potassium. In the case of deficiency of phosphorus or potassium fertilizer or insufficient dosage, the application of organic fertilizer can also increase the yield increase effect of nitrogen fertilizer, but it is necessary to increase the application rate of nitrogen fertilizer to prevent crop nitrogen deficiency. Because soil microbes are in the process of decomposing mature organic fertilizers, in addition to the nitrogen in organic fertilizers, some nitrogen in the soil is often consumed, resulting in short-term nitrogen deficiency in the soil.
(3) Nitrogen application rate
China's nitrogen fertilizer consumption is large, accounting for more than 66% of total fertilizer use. Therefore, if the amount of nitrogen fertilizer is appropriate, it can reduce waste, which is one of the key links of rational fertilization. The application rate of nitrogen fertilizer is closely related to crop yield, crop type, soil fertility, climatic conditions, and application of phosphorus and potassium fertilizers and organic fertilizers.
1 Nitrogen application rate and crop yield Nitrogen application rate is affected by many factors, but due to the general lack of soil nitrogen in China and the small residual effect of nitrogen fertilizer in the soil, the relationship between nitrogen application rate and crop yield is very close, and the crop yield is more High, the amount of nitrogen fertilizer should be increased accordingly. This method is also called "to produce nitrogen, within the range of nitrogen fertilizer use, and then to hate according to local specific conditions, the upper or lower limit of the amount of choice.
2 The amount of nitrogen fertilizer and the variety of crops The demand for nitrogen in various crops is different. Under the same yield, oil, raisin vegetables, cotton, Spring corn, winter wheat, summer corn, rice, etc. need more nitrogen, silage corn and pasture also need more nitrogen; peanuts, soybeans and Although legume green manure and other crops require more nitrogen in their lifetime, most of them rely on rhizobium to fix nitrogen in the air. It is only necessary to apply a small amount of nitrogen fertilizer at the early stage of growth to promote nodule formation. If excessive application of nitrogen fertilizer, it will hinder nodule formation. To reduce nitrogen fixation; starch and sugar crops such as sweet potato, potato, sugar beet, sugarcane, etc. do not need to apply too much nitrogen fertilizer. Excessive nitrogen will affect the synthesis of starch and sugar, and reduce product quality; tobacco can not be applied too much. Nitrogen fertilizer, excessive nitrogen, thick leaves, poor taste of tobacco, such plants need more phosphorus and potassium fertilizer. The requirements for nutrients of different varieties of the same crop are also different. Some varieties are resistant to fertilizer and have a large potential for increasing production, and the amount of fertilizer can be appropriately increased. For varieties that are not resistant to fertilizer, they should not be applied more. The amount of nitrogen should be properly controlled to avoid the stagnation.
The reasonable amount of nitrogen fertilizer should take into account both production and net income. Within a certain range of nitrogen fertilizer application, with the increase of nitrogen application rate, the crop yield is also gradually increased, but the yield increase benefit per unit of nitrogen fertilizer is reduced. This is the phenomenon of “decreasing returns†in fertilization. According to 1981-1983 national fertilizer The test results of "the relationship between different nitrogen fertilizer dosage and fertilizer efficiency" conducted by the test network showed that in the case of medium nitrogen application rate of 6-10 kg per mu, the yield per 10 kg of nitrogen increased by 10 to 12 kg, and the nitrogen utilization rate was 35% to 45. %, although the yield increase per unit of nitrogen fertilizer decreases with the increase of the amount of nitrogen fertilizer, as long as the added fertilizer price is lower than the price of the increased product, the higher yield and the largest net income can be obtained. The reasonable application rate of nitrogen fertilizer is also called the optimal nitrogen application rate.
Nitrogen fertilizer can be used as base fertilizer, seed fertilizer and top dressing. Mastering the proper application period of nitrogen fertilizer plays an important role in improving yield and fertilizer utilization and reducing environmental pollution. Base fertilizer, also known as base fertilizer, is a fertilizer applied during land preparation and tillage. Adequate base fertilizer is the basis for obtaining high yield. When applying organic fertilizer, phosphate fertilizer or phosphorus and potassium fertilizer, nitrogen fertilizer can be used to meet the nutrient needs of crop seedlings, which is beneficial to strong seedlings and increase the rate of ear formation. The amount of nitrogen fertilizer used as base fertilizer is related to crop, soil and nitrogen fertilizer varieties. Short-growing crops, such as northern wheat, late-wheat, spring wheat, and southern double-season rice, are the key to increasing yield. Generally, the base fertilizer should be reapplied, and the amount of fertilizer applied can account for 70% to 80% of the total amount of nitrogen fertilizer applied. The medium and low-yield fields can also be applied at one time, no longer topdressing. In arid areas where there is little rain and no irrigation conditions, the effect of top dressing is often small, and it is advisable to use a single base fertilizer.
Long-growing crops, such as spring rice, spring maize, winter wheat, cotton, and southern rice crops in the north, generally have a growth period of about 150 days. Therefore, it is necessary to prevent the early growth and the late de-fertilization. The method of topdressing and weighting, the amount of base fertilizer is 4-6 kg per mu of nitrogen fertilizer, accounting for 40% to 60% of the nitrogen fertilizer amount in the whole growth period. For some economic crops such as sugar cane, Brassica napus, cabbage Chinese cabbage, etc., the yield is high, and the fertilizer is required to be applied in many times. The proportion of base fertilizer is relatively low, such as spring planting sugar cane, base fertilizer with nitrogen fertilizer (N) 2 to 3 kg per mu, cabbage-type rapeseed with nitrogen fertilizer (N) kg per mu, cabbage Chinese cabbage often do not use nitrogen fertilizer to apply sufficient organic fertilizer And phosphorus and potassium fertilizers can be used as the base fertilizer. These crops use nitrogen fertilizer as the base fertilizer, which accounts for nearly 30% of the total growth period.
Peanut, soybean and other legumes have no formation or a small number of nodules during the pupal period, and the nitrogen-fixing ability is weak. Therefore, the basic fertilizer should also be paid attention to. The amount of nitrogen fertilizer per mu (N) is 2 to 3 kg, accounting for about 60% of the nitrogen fertilizer in the whole growth period. %the above.
The base fertilizer and base fertilizer of perennial crops such as fruit trees and tea trees are separated. The base fertilizer refers to the fertilizer applied to the perennial crops in combination with deep tillage and soil change. The main function of the base fertilizer is to increase the soil organic matter and promote the improvement of soil physical and chemical properties, so as to lay a good soil foundation for the subsequent crop growth. Generally, delayed nutrients such as organic fertilizer are mainly applied. The base fertilizer of perennial crops often has many forms. For example, tea trees have two forms, one is applied when cuttings are planted or seeds are broadcasted live, and the other is applied to tea gardens every autumn and winter, which is called the base fertilizer of tea trees. The tea garden base fertilizer is compounded with organic fertilizer and phosphorus-potassium fertilizer. When the organic fertilizer is insufficient, nitrogen fertilizer (N) is applied for 2 to 3 kg per mu.
The principle of “fertilizer and less application, less application of thin soil, less application of sandy soil and more application of cohesive soil†should be mastered. The amount of clay base fertilizer can exceed 50% of the total fertilizer application, 50% of loam and 30% of sand. About % is appropriate. Sandy soil is easy to leak, especially in paddy fields and rainy areas. Ammonium bicarbonate and ammonia water are volatile and should be used as base fertilizer. Deep application can reduce the loss of volatilization. Nitrogen fertilizers with stable properties such as ammonium sulfate, urea and ammonium nitrate are left as top dressings or seed fertilizers, which saves labor and reduces nitrogen losses. In addition, when applying the mature organic fertilizer as a seed fertilizer, the amount of nitrogen fertilizer should also be appropriately increased.
Fertilizer refers to the fertilizer applied during sowing or transplanting. Generally, no fertilizer is needed when applying the base fertilizer. If there is no base fertilizer or insufficient base fertilizer, a small amount of nitrogen fertilizer can be used for dry crops such as wheat, corn, millet and sorghum. As a seed fertilizer, the sample can also promote the early development of the young cub, and the yield increase effect is very obvious. However, when the wheat is directly mixed with ammonium sulfate, the seed and the fertilizer should be dry, and it must be mixed with the mixture, and the ammonium sulfate per mu. Do not use more than 5 kg. Other nitrogen fertilizers should avoid direct contact with seeds and prevent the risk of seed germination due to high fertilizer concentration and high hygroscopicity. When the amount of fertilizer is large, it should be applied by ditch or acupoint.
The urea concentration is high, and after changing to ammonium nitrogen, the mobility is not as good as that of nitrate nitrogen. Therefore, the large amount and concentrated application may cause local alkalization of the soil and burn seedlings. Especially urea with a higher biuret should be used with care. Therefore, the urea ditch should also control the dosage. We found that when planting corn in the northern region, there was a burning phenomenon due to the application of urea about 20 kg in the ditch. Cotton seeds are most sensitive to urea. After soaking seeds, the cotton seeds cannot be mixed with urea, otherwise the seedlings will be affected.
Topdressing is also called composting. According to the demand for nutrients in crops, it is necessary to supplement the deficiency of base fertilizer and seed fertilizer to prevent fertilizer from being applied during the period of crop growth. The number, period and dosage of top dressing are mainly based on the fertilizer characteristics of the crop.
Crop topdressing with short growth period, such as double-season rice in the south, wheat in late rice, late-season rice in spring, spring wheat, etc. When the base fertilizer and seed fertilizer are insufficient, the topdressing should be early and late, and the rice should generally be applied about 7 days after transplanting. After the tillering, the nitrogen fertilizer (N) is 2~4 kg per mu, and the summer corn without the base fertilizer and seed fertilizer can be applied to the joint fertilizer. The nitrogen fertilizer (N) is 4-5 kg ​​per mu. Long-growing crop topdressing, such as spring maize, winter wheat, single-season rice, and southern mid-season crops in the north, have longer growth periods and higher yields. In the case of applying base fertilizer, nitrogen can be applied per acre (N). 4 to 6 kg, generally divided into two top dressings, the first time in the tillering stage or jointing stage, should be re-chased; the second time is the panicle fertilizer, if the crop is good, it can be applied less or not.
There are many types of cash crops and different fertilizer characteristics, so the topdressing is different. Such as spring planting sugar cane, although the amount of nitrogen fertilizer should not be too much, but also divided into seedling fertilizer, strong fertilizer, joint fertilizer and strong tail fertilizer and many other top dressing. Zhuangfei fertilizer and jointing fertilizer should be applied with nitrogen fertilizer (N) 3 to 4 kg per mu. The seedling fertilizer and the strong tail fertilizer are chased 2 to 3 kg respectively. Another example is the long growth period of cotton, which is generally divided into four parts: seedling fertilizer, bud fertilizer, flower bell fertilizer and topping fertilizer. The seedling fertilizer should be applied early, using about 1 kg of nitrogen fertilizer per mu (N), combined with cultivating after the seedling is fixed; the bud fertilizer should be applied stably, and the nitrogen fertilizer per mu (N) is 1-2 kg (the amount of nitrogen fertilizer in the northern cotton field should be more than that in the south). If the cotton field grows vigorously, it should be applied late or less. Flower bell fertilizer should be re-applied, using 3 to 4 kilograms of nitrogen fertilizer per acre. It is usually applied when 1 to 2 large peaches are held in the lower part of the cotton plant. If the cotton grows longer, the amount of fertilizer can be reduced. The top-top fertilizer should be applied skillfully, and the nitrogen fertilizer per acre should be 0.5~1 kg, which can prevent premature aging of cotton, multi-ringing, and increase the weight of bolls and clothes. If the bottom fertilizer is sufficient, the early topdressing or the cotton plant does not produce premature aging, there is no need to cover the top fertilizer to avoid its late maturity. Perennial crop topdressing is more complicated than top dressing per year. Need to apply fertilizer several times, such as tea garden topdressing more than 4 times a year, according to tea varieties and yields.
(4) Application method of nitrogen fertilizer
In order to reduce the loss of nitrogen leaching, volatilization and denitrification, the fertilization method should be considered: the nitrogen fertilizer should be applied to the soil at a certain depth; the ammonium nitrogen fertilizer cannot be mixed with the alkaline substance because the alkaline substance can accelerate The ammonium nitrogen is decomposed and volatilized; the soil should maintain a good moisture when fertilizing.
The application method of the base fertilizer, the solid nitrogen fertilizer and the ammonia water are applied differently in the dry land and the paddy field. Dryland base fertilizers, such as wheat and corn, can be combined with cultivated land. The solid fertilizer is evenly spread on the ground, and then ploughed into the soil, and it can be turned over with the stalks. The depth of most fertilizers is 10-15 cm.
Fertilization of paddy fields generally does not advocate the application of ammonium nitrate, and other solid fertilizers can be used. The method of fertilizing is to spread the fertilizer on the wet soil after the plow is turned over, and then turn the fertilizer into the soil layer, and then sown or transplanted by pouring the water and ploughing the ground. Urea is easily leached with water, so the soil to which urea is applied should be irrigated for 5 to 7 days after urea is converted to ammonium carbonate. Another method of applying the paddy field base fertilizer is to spin the ploughing and then transplant the stalk after the ploughing and ploughing of the paddy field. This method is called “full layer deep application†and can turn most of the fertilizer into about 10 cm deep. In the reducing layer, the fertilizer effect is very good.
The method of deep application of paddy field is to pour shallow water immediately after plowing or ploughing the field. It is not advisable to apply nitrogen fertilizer. Generally, it is 2 to 3 kg per mu, and then simmered for 1 to 2 times. After the flattening is flattened, it can be inserted. The fertilizer is evenly distributed in the soil layer about 7 cm deep, which not only acts as a noodle fertilizer, but also reduces the leaching loss of nitrogen. When urea is used as a noodle fertilizer, it is not possible to release water in the process of dumping.
Ammonia water is applied differently than solid nitrogen fertilizer. The commonly used method in dry land is to use the "plowing bottom ammonia method" to install the ammonia water in the ammonia water tank on the tractor frame, and to introduce the ammonia water to the back of the plough through the plastic pipe, and evenly apply the ammonia water to the furrow while cultivating the land. If you use the animal power to cultivate the land, you can use ammonia water or a back ammonia water tank, and then apply it along the furrow. Then the cultivated land is covered with soil, so that the ammonia water can be applied to the soil layer of about 15 cm. The commonly used method in paddy fields is the “bottom fertilizer application methodâ€, which is to fill a thin layer of water in the field, mix the ammonia water and the muddy water evenly, apply it to the field surface, then plow the field, and then transplant the rice. In addition, it is also possible to apply ammonia water after watering and mulching, and then use a small tractor to rot the plough, and evenly plough the ammonia into the soil layer, and then mix it and then transplant it.
Application method of top dressing When ammonium bicarbonate, ammonium sulfate, urea, ammonium chloride and ammonium nitrate are topdressed on the dry land in the north, the wheat, millet and other seed crops can be ditched, that is, the ditch is about 7 cm deep between the crop rows. Apply fertilizer along the ditch, and then cover the soil. For the medium-crop crops such as corn, sorghum, cotton, etc., the method of “point application†is adopted, that is, 7 to 10 cm beside the plant, and a small hole of 7-10 cm is dug, and the fertilizer is spread. Cover the soil. Watering should be done immediately after fertilization in the dry season, so that the fertilizer effect can be exerted.
It is not advisable to use ammonium nitrate in paddy field topdressing. Other fertilizers should be drained from the field before fertilization. After applying fertilizer, combine with cultivating and weeding to carry out the field, so that the fertilizer and soil mix and mix, evenly distributed in the soil layer of 7-10 cm. Urea should be hydrolyzed by soil. Only after being absorbed by the crop. Therefore, the top dressing should be 3 to 5 days ahead of other nitrogen fertilizers, and the irrigation should also be carried out 5 days after the urea application. Although the deep application of the ball fertilizer has a good yield increase effect, it is more costly.
Ammonia water is used as a top dressing method in the north dry field. The ditch method generally uses a traction ammonia water fertiliser, which is towed by one animal, one person is fertilized by a fertiliser, the other is then covered with soil, and the ammonia water is diluted 5 to 10 times, the depth and distance of fertilization. It is appropriate to use about centimeters of each plant. Ammonia water is used for topdressing in paddy fields. Generally, it is applied by filling method. Before the application, the water in the field is drained, and the container of ammonia water is placed on the mouth of the ditch. The siphon principle is applied to the bottom of the irrigation ditch by a small rubber tube, and the brick is used to stand. Recirculation is caused at the entrance of the furrow, so that the ammonia water is mixed with the irrigation water before entering the field, and then flows into the rice field. This method can also be used for irrigated land in dry fields.
Top dressing refers to the force method of supplying nutrients to crops by spraying fertilizer on the foliage. The concentration of urea applied is 1% to 2% for rice, wheat and grass, 1% for vegetable and rai, about 0.5% for fruit trees, 0.2% for flowers, forest seedlings, strawberries, greenhouse cucumbers and seedlings in hot seedlings. . About 1 kg of urea per acre. Spray once every 7 to 10 days, usually 2 times, and the spraying time is better in the evening or early morning. The crop growth period and adult fruit trees can increase the spraying concentration appropriately. If there is no nitrogen deficiency in the late crop, no urea is required to be sprayed by leaves. Foliar application of fertilizer is particularly effective for crops with root growth barriers and absorptive capacity, but it is an auxiliary fertilization and cannot replace root fertilization.
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