Nitrogen fertilizer efficiency is constrained by climate, soil, crops, nutrient balance, fertilizer technology, and other cultivation and management measures. Therefore, reasonable application of nitrogen fertilizer should be based on the crop yield, soil properties, nitrogen fertilizer species and other conditions in order to give full play to the role of nitrogen fertilizer production and improve its economic efficiency.
(I) Reasonable distribution of nitrogen fertilizer
The commonly used nitrogen fertilizers are available nitrogen fertilizers and have significant yield increase effects on different soils and crops. However, because of the different nature of chemical fertilizers, the effect of increasing yield on different soils and crops is also different.
1. Because of the distribution of nitrogen fertilizer
Ammonium nitrate is vulnerable to leaching and denitrification, so it is rarely used in paddy fields and heavy rain areas in southern China, especially in long-term flooded paddy fields.
In northern China, there are more dry lands, better ventilation, less rainfall, and more irrigation, resulting in less loss of ammonium nitrate leaching and denitrification. In calcareous and alkaline soils, the loss of nitrogen is mainly ammonia volatilization. Therefore, in the case of deep nitrogen fertilizer application, the effects of ammonia nitrogen fertilizer (including urea) and nitrate nitrogen fertilizer are not significantly different, but in areas with poor dry climate or cold climate (low urinary enzyme activity, affect urea conversion), nitric acid The effect of ammonium fertilizer is better than that of urea and ammonium nitrogen fertilizer. Therefore, ammonium nitrate should be mainly used on dry crops.
Ammonium sulfate, ammonium chloride and the like are physiological acidic fertilizers and are more suitable for use in calcareous soils. If long-term application in acidic soil, lime or organic fertilizer should be added to enhance buffering capacity and neutralize soil acidity. However, ammonium sulfate is applied on paddy fields for a long time. Because under the condition of oxygen deficiency, a large amount of hydrogen sulfide or ferrous sulfate is liable to be generated, which may cause damage to rice roots; in long-term application on calcareous soil, a large amount of calcium sulfate is liable to be formed, resulting in Soil compaction. Therefore, it is not advisable to apply a single ammonium sulfate on these plots for a long period of time, and it must be applied in combination with other nitrogenous fertilizers.
2. Because of the distribution of nitrogen fertilizers
Crops have a certain degree of selectivity for the form of nitrogenous fertilizers and their sub-components. Ammonium chloride contains chloride ions and cannot be used on tobacco, otherwise it will affect its combustibility, easy to "flame off" and poor in odor. Chlorine sensitive crops such as tea, grapes, watermelon, citrus, potato, sugar beet, and sugar cane must 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 be reduced, because the chloride ions can promote the hydrolysis of carbohydrates and affect the quality. In addition, the potato like sulfur, sugar beet and hi sodium, have a good response to the application of ammonium sulfate and sodium nitrate respectively. Wheat, corn and other cereal crops are equally effective for ammonium and nitrate nitrogen fertilizers. Due to the lack of reductase in the roots, rice has a poor ability to use nitrate nitrogen and reacts well to ammonium nitrogen; potato starch-like 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, nitrate-nitrogen fertilizer can promote leaf growth, and ammonium nitrogen can be adsorbed by soil colloid. The fertilizer has stable fertilizer effect, which is beneficial to the maturation of later leaves. The thickness of leaves is suitable, the color is good, and the taste is pure.
(B) Application of Nitrogen Fertilizer in Combination with Phosphorus and Potassium Fertilizers
With the development of agricultural production, the nutrients taken from the soil by crops are increasing, and people return to the soil. There are often several nutrients in the soil and the supply is insufficient. The normal growth of crops requires the balanced supply of multiple nutrients. According to the current soil nutrient status in China, most of the soil is lack of nitrogen and phosphorus nutrients, while the shortage of potassium in the soil in the south is increasingly serious. Therefore, at present, nitrogen and phosphorus are mainly considered in the north, and in the south (including some high-yield and potassium-depleted lands in the north), the combined application of nitrogen, phosphorus and potassium, and the combined application of nitrogen and organic fertilizers should be considered in order to increase the nitrogen fertilizer efficiency. .
1 The combined application of nitrogenous fertilizer and phosphate fertilizer When both nitrogen and phosphorus are absent and potassium is abundant, generally only nitrogen fertilizer or phosphate fertilizer has the effect of increasing production, but the increase rate is not large. On this plot, if nitrogen and phosphorus are applied together, better stimulation can be achieved. The results of nitrogen- and phosphorus- and potassium-enriched plots in Feixiang County, Hebei Academy of Agricultural Sciences, where fertilizers were applied alone, yielded 33 kilograms per kilogram of wheat, 48 kilograms of monofertilizer, and 109 kilograms of the same amount of nitrogen and phosphorus. Compared with a single application of nitrogen and phosphorus, the sum of the production of 81 kg, 28 kg more. This phenomenon is called the conjunction between nitrogen and phosphorus, also known as interaction. From the above, it can be seen that nitrogen fertilizer is a "synergist" for phosphate fertilizer, and phosphorus fertilizer is also a "synergist" for nitrogen fertilizer. In this type of area and soil, it is reasonable to use nitrogen and phosphorus in combination with nitrogen fertilizer. One of the main measures of application.
2Coupled application of nitrogenous fertilizers with phosphorus and potassium fertilizers According to the results of paddy fields in Huaiji, South China Sea and other places where the soil fertilizers of the Guangdong Academy of Agricultural Sciences were located in 1980, nitrogen and phosphorus, nitrogen and potassium, nitrogen and phosphorus and potassium were found on plots where nitrogen, phosphorus and potassium were all absent. With the application, the yield was higher than that of single application of nitrogen fertilizer, and the effect of combined application of nitrogen, phosphorus, and potassium fertilizers was the most significant. This type of plot is suitable for the combination of nitrogen fertilizer and phosphorus and potassium fertilizers. In the P-N and K-enriched plots, the combined application of N, K, N, P, and K increased rice yield by 47% and 49%, respectively, compared with no fertilizer, and the fertilizer effects were similar. In this case, the combination of nitrogen and potassium can be used.
In addition, organic fertilizer contains more phosphorus and potassium elements. In the absence of phosphorus or potassium fertilizer or insufficient dosage, the application of organic fertilizer can also increase the effect of increasing nitrogen fertilizer production, but it is necessary to increase the application amount of nitrogen fertilizer to prevent nitrogen deficiency in crops. Because soil microorganisms in the process of decomposing the end of mature organic fertilizer, in addition to nitrogen in organic fertilizer, it is also often consumed part of the nitrogen in the soil, resulting in short-term soil nitrogen deficiency.
(three) the amount of nitrogen fertilizer application
China has a large amount of nitrogen fertilizer, accounting for more than 66% of the total fertilizer use. Therefore, the proper amount of nitrogen fertilizer can reduce waste, which is one of the key aspects of rational fertilization. The application amount of nitrogen fertilizer is closely related to crop yield, crop types, soil fertility, climatic conditions, and the application of phosphorus, potassium, and organic fertilizers.
1 Nitrogen application rate and crop yield Nitrogen application rate is affected by many factors. However, due to the general lack of soil nitrogen in China and the residual effect of nitrogen fertilizer in the soil is small, the relationship between nitrogen fertilizer application amount and crop yield is very close. The higher the amount of nitrogen fertilizer, the corresponding increase. This method is also called "in order to produce nitrogen, in the range of nitrogen fertilizer dosage, and then according to local specific conditions, choose the upper or lower limit of the amount.
2 The relationship between the amount of nitrogen fertilizer and the type of crops The demand for nitrogen in different crops is not the same. At the same yield, oilseeds, leafy vegetables, cotton, spring corn, winter wheat, summer corn, and rice need more nitrogen; silage corn and pasture also require more nitrogen; peanuts, soybeans, and Although leguminous green manure and other crops need more nitrogen in their lives, most of them rely on rhizobia to fix nitrogen in the air. It is only necessary to apply a small amount of nitrogen fertilizer at the beginning of growth to promote root nodule formation. If too much nitrogen fertilizer is applied, it will hinder root nodule formation. Reduce nitrogen fixation; starch and sugar crops such as sweet potatoes, potatoes, sugar beets and sugar crops do not need to use too much nitrogen fertilizer; too much nitrogen will affect the synthesis of starch and sugar and reduce product quality; tobacco cannot be used too much. Nitrogen fertilizer, excessive nitrogen, leaf hypertrophy, and poor tobacco taste, such crops require more phosphorus and potassium fertilizers. Different varieties of the same crop have different requirements for nutrients. Some varieties are resistant to fertilizer and their potential for increasing yield is large, and the amount of fertilizer can be appropriately increased. For varieties that are not resistant to fertilization, it is not possible to apply more, and the amount of nitrogen applied should be appropriately controlled to avoid greediness and lodging.
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, crop yields are also gradually increasing, but the yield-increasing benefits of unit nitrogen fertilizers are decreasing. This is the phenomenon of “decreasing returns†in fertilization. According to national fertilizers from 1981 to 1983, The test results of the “Relationship between Different Nitrogen Fertilizer Amount and Fertility Effect†conducted by the trial network showed that: Under the moderate nitrogen application rate of 6 to 10 kilograms per acre, the grain yield per kilogram of nitrogen is 10 to 12 kilograms, and the nitrogen fertilizer utilization rate is 35% to 45. In spite of the fact that, with the increase in the amount of nitrogenous fertilizer, the yield increase per unit of nitrogen fertilizer has decreased. However, as long as the price of chemical fertilizer added is less than the price of the increased production, a higher yield and the largest net yield can be obtained. As a reasonable amount of nitrogen fertilizer, also called the best amount of nitrogen.
Nitrogen fertilizer can be used as base fertilizer, seed fertilizer and topdressing fertilizer. It is very important to grasp the proper application time of nitrogen fertilizer to increase the yield, fertilizer utilization, and reduce environmental pollution. Basal fertilizer, also known as base fertilizer, is fertilizer applied during soil preparation and plowing. Sufficient basal fertilizer is the basis for obtaining high yields. Applying organic manure, phosphate fertilizer or phosphorus and potassium fertilizers while applying enough nitrogen fertilizer can meet the needs of nutrients for seedlings at the seedling stage, and it is beneficial to strong seedlings and to increase the rate of success. The amount of nitrogen fertilizer used as a base fertilizer is related to the crop, soil, and nitrogen fertilizer varieties. For crops with short growing periods, such as northern wheat, late spring wheat, southern double cropping rice, and so on, early growth of strong seedlings is the key to increasing yield. Generally, basic fertilizer should be re-used, and the amount of fertilizer can account for 70% to 80% of the total amount of nitrogen fertilizer application. The middle and low-yielding fields can also be given full time, and no fertilizer can be applied. In arid areas where rainwater is scarce and there is no irrigation condition, the effect of top dressing is often limited, and one-time application of basal fertilizer should be adopted.
For long-growing crops, such as spring rice in the north, spring corn, winter wheat, cotton, and mid-season crops in the south, the growth period is generally around 150 days. Therefore, in order to prevent prolonged growth and defermented fertilizers in the later stages, basal fertilizers are generally used. The method of top-dressing and equalizing the amount of basic fertilizer is 4 to 6 kg of nitrogen fertilizer per mu, which accounts for about 40% to 60% of the total amount of nitrogen fertilizer in the whole growth period. For some economic crops such as sugar cane, cabbage-type rapeseed, Chinese cabbage and other high-yield, requiring a large amount of fertilizer is generally divided into multiple nitrogen fertilizers. The proportion of basal fertilizer is relatively low, such as spring planting sugar cane, basal fertilizer with nitrogen fertilizer (N) 2 to 3 kg per mu, and cabbage rape with nitrogen fertilizer (N) kg per mu, cabbage cabbage is often used without nitrogen fertilizer and sufficient organic fertilizer. And phosphorus and potassium fertilizer can be used as base fertilizer, these crops use nitrogen fertilizer as the base fertilizer accounted for nearly 30% of the whole growth period.
Peanuts, soybeans, and other leguminous crops have no or very few root nodules in the young, and their nitrogen fixation capacity is weak. Therefore, they should also pay attention to basal fertilizers. The amount of nitrogen fertilizer (N) per acre is 2 to 3 kg, accounting for about 60 percent of the total nitrogen fertilizer use. %the above.
Base and base fertilizers for perennial crops such as fruit trees and tea trees are separate. Bottom fertilizer refers to the combination of deep ploughing and soil-applied fertilizers for perennial crops that are combined with deep ploughing and soil amendments. The basic role of base fertilizers is to increase soil organic matter and improve the physical and chemical properties of soil so as to lay a good soil foundation for subsequent crop growth. In general, the use of organic fertilizer and other late-effects are divided. Base fertilizers for perennial crops tend to take many forms. For example, tea plants come in two forms. One is for cuttings and planting or when the seed is seeded. The other is for autumn and winter that is applied to tea gardens. Both are called base fertilizers for tea trees. Tea garden basal organic fertilizer and phosphorus and potassium fertilizers are combined. When organic fertilizer is insufficient, nitrogen fertilizer (N) is 2 to 3 kg per mu.
It is necessary to grasp the principle of “fewer fertilizers, less application of lean land, less application of sandy soil, and multiple application of clay soilâ€. The amount of clay basal fertilizer may exceed 50% of the total amount of nitrogen fertilizer in the whole growing period, about 50% of loam, and 30 of sandy soil. % is appropriate. Sandy soils are prone to leakage, especially in paddy fields and rainy areas. Ammonium bicarbonate and ammonia water are volatile and should be used as base fertilizers. Deep application can reduce volatile losses. Ammonium sulfate, urea, ammonium nitrate and other more stable nitrogen fertilizers are used as top-dressing or seed fertilizers to save labor and reduce nitrogen losses. In addition, when applying mature organic fertilizers as seed fertilizers, the amount of nitrogen fertilizers should also be appropriately increased.
Fertilizer refers to the fertilizer applied during sowing or transplanting. Generally, it is not necessary to apply seed fertilizer when applying base fertilizer. If there is no basal fertilizer or insufficient base fertilizer, dry crops such as wheat, corn, millet and sorghum can use a small amount of nitrogen fertilizer. For seed fertilizer, sample delivery can also promote the early occurrence of young larvae, and the yield increase effect is very obvious. However, when wheat is directly seeded with ammonium sulfate, it should be ensured that the seed and the fertilizer are dry, and be sure to be accompanied by sowing and ammonium sulfate per acre. The dosage should not exceed 5 kg. Other nitrogen fertilizers as seed fertilizers should avoid direct contact with the seeds and prevent the risk of seed germination due to high concentration of fertilizers and strong hygroscopicity. When the amount of seed fertilizers is large, they should be applied or applied.
The urea concentration is high, and after it is changed to ammonium nitrogen, the mobility is not as good as that of nitrate nitrogen. Therefore, a large amount of concentrated application can easily result in local alkalization of the soil and burning of seedlings. Especially with high biuret urea, use caution. Therefore, the amount of urea should be controlled. When we found that corn was planted in northern areas, about 20 kg of urea was used to burn seed. Cotton seeds are the most sensitive to urea, and cotton seeds cannot be mixed with urea after soaking the teeth, otherwise the seedlings will be affected.
Topdressing, also known as compensatory fertilizer, is based on the demand of nutrients from crops to supplement the deficiency of base fertilizers and seed fertilizers and to prevent fertilizers applied during deferment of fertilizers during crop growth. The frequency, time, and amount of topdressing are mainly based on the characteristics of the crop's fertilizer requirements.
For crops with short growing period, such as the double cropping rice in the south, late wheat in the north, spring wheat, and other crops, the top dressing should not be late as soon as possible. The rice should generally be applied after 7 days of transplanting. The spring wheat is Before and after delivery, use nitrogen fertilizer (N) 2 to 4 kilograms per acre. If no summer fertilizer is used for basal fertilizer and seed fertilizer, follow-up joint fertilizer may be applied. Nitrogen fertilizer (N) is 4 to 5 kg per mu. Crops with long growth periods, such as northern spring maize, winter wheat, single-season rice, and southern mid-season crops, have a long growing period, and their yields are often higher. Under the condition that basic fertilizers are applied, nitrogen can be applied to each acre (N). 4 to 6 kilograms, usually divided into two top dressings, the first time in the tillering or jointing period, should be chasing; the second is panicle fat, if the crop is growing well can also be less or not Shi.
There are many types of cash crops and the characteristics of fertilizers are different, so top dressing is not the same. Such as spring planting sugar cane, although the amount of nitrogen fertilizer should not be too much, but also points Miaofei, Zhuangfeifei, jointing fertilizer and Zhuang tail fertilizer and other fertilizers. Strong fertilizer and jointing fertilizer topdressing nitrogen fertilizer (N) 3 ~ 4 kg per acre. Miao Fei and Zhuang Tail fertilizer chase 2 to 3 kilograms respectively. Another example is the long growth period of cotton, generally divided into Miao Fei, Lei Fei, flower bell fertilizer, cover fertilizer 4 times topdressing. Miaofei should be applied early, with about 1 kilogram of nitrogen (N) per acre, combined with cultivator after the fixed seedlings; bud fertilizer should be applied steadily, with nitrogen fertilizer (N) 1~2kg per mu (northern cotton fertilizer should be used more than in the south ) If the cotton field is growing strong, it is necessary to apply it lately or sparingly. The flower and boll fertilizer should be reused, and nitrogen fertilizer should be 3 to 4 kilograms per acre. Normally, it should be planted in the lower part of the cotton plant to house 1 to 2 large peaches. If the cotton grows longer, the amount of fertilizer can be reduced. The cover top fertilizer should be applied skillfully. The application of 0.5 to 1 kg of nitrogen fertilizer per mu can prevent premature aging of cotton, increase the number of bells, and increase the boll weight and clothing weight. If the base fertilizer is sufficient, if there is more fertilizer in the early stage or the premature aging of the cotton plant is not produced, there will be no need to cover the top fertilizer and avoid late-maturing. Perennial crops are more complex than perennial crops. Need to top-dress many times, such as tea garden top dressing more than 4 times a year, according to tea varieties and yield.
(D) Application methods of nitrogen fertilizer
In order to reduce the loss of nitrogen leaching, volatilization, and denitrification, consideration should be given to the method of fertilization: nitrogen fertilizer should be applied to a certain depth of soil; ammonium nitrogen fertilizer must not be mixed with alkaline substances because alkaline substances can accelerate Ammonium nitrogen decomposes and volatilizes; when fertilizing, the soil must maintain good sensation.
The application method of basal fertilizer is different in the application methods of solid nitrogen fertilizer and ammonia water in dry land and paddy field. Dryland basal fertilizers, such as wheat and corn, can be used in combination with arable land. Solid fertilizers are evenly spread on the ground, then ploughed into the soil, and then turned to be soiled with mulching. The depth of most fertilizers is 10 to 15 cm.
Fertilization in paddy fields is generally not recommended for the application of ammonium nitrate, and other solid fertilizers may be used. The method of fertilizing is to spread the fertilizer on the surface of the moist soil after the plow is turned over, and then turn the fertilizer into the soil layer, sow and plow till the soil is flattened and then transplanted. Urea is easy to leach with water, so the soil to which urea is applied should be used for 5 to 7 days until the urea is converted to ammonium carbonate and then flooded. Another way to apply base fertilizer to paddy fields is to paddle the paddy fields and turn them into flat water. After spreading the soil with fertilizer and turning the soil, the method is called “full depth application†and can turn most fertilizers into about 10 cm depth. In the reducing layer, the fertilizer retention effect is very good.
The method of deep application of paddy field fertilizer is to irrigate shallow water immediately after plowing or paddy fields. It is not appropriate to apply nitrogen fertilizer, generally 2 to 3 kilograms per acre, and then plow 1 to 2 times to spread the paddles. Fertilizers are evenly distributed in soil layers about 7 cm deep, which not only plays the role of surface fertilizer but also reduces the leaching loss of nitrogen. When urea is used as a surface fertilizer, it is not allowed to freely discharge water during the process of paddy fields.
Ammonia based application differs from solid nitrogen fertilizers. The commonly used method in dry fields is the "plow-bottomed ammonia method" in which ammonia is placed in an ammonia tank on a tractor's frame, and the ammonia water is led through the plastic pipe to the rear of the ploughshare. The ammonia is evenly applied to the furrow in the arable land. If farmland is used for animal power, ammonia water can be used to dip ammonia water tanks or backwater canals along the furrows, and then the farmland can be covered with soil so that the ammonia can be applied to a soil layer of about 15 cm. The commonly used method of paddy field is "bottom fertilization method" that is, first filling a thin layer of water in the field, mixing ammonia water and mud water uniformly, applying it to the field surface, and then plowing the ridge, and then transplanting hoe. In addition, it is also possible to apply ammonia after irrigation and soil preparation, then use a small tractor to turn the plough, evenly plough the ammonia into the soil, and spread it evenly.
Application methods of topdressing When ammonium bicarbonate, ammonium sulfate, urea, ammonium chloride, and ammonium nitrate are used as top dressings on northern dry land, they can be applied to canopy crops such as wheat and millet, that is, about 7 cm deep in the rows of crops. , Fertilizer along the ditch, then cover the soil, the commonly used on the cultivating crops such as corn, sorghum, cotton and other "point application" method, that is 7 to 10 cm in the line, dig 7 to 10 cm deep hole, spread fertilizer Cover soil. Water should be watered immediately after fertilization in the dry season so that fertilizer effects can be exerted.
Paddy fertilizer should not use ammonium nitrate. Before fertilizing, other fertilizers shall be used to remove the water from the field, spread the fertilization materials, combine the cultivators and weeds for the paddy field, stir and mix the fertilizer and the soil, and evenly distribute it in the soil layer of 7 to 10 cm. Urea must be transported through soil urease. After being absorbed by crops. Therefore, top dressing is 3 to 5 days ahead of other nitrogen fertilizers. Irrigation also requires 5 days after topdressing urea. Although the deep ball fertilizer has a good effect of increasing production, it is more costly.
Aqueous ammonia is used as topdressing in trenches in the northern dry land, and traction type ammonia fertilisers are commonly used in furrows. One animal pulls traction, one fertilizes fertilizer, and the other then covers soil. Ammonia water is diluted 5 to 10 times in water, and the depth and distance of fertilization are applied. About centimeters from the plant is appropriate. Ammonia is used as topdressing in paddy fields. Generally, irrigation method is used. Before the application, the water in the fields is drained. The container of ammonia is placed on the furrow and the ammonia is introduced into the bottom of the irrigation ditch using a small hose and the bricks are used. At the entrance of the ditch, it causes backflow, mixing the ammonia with the irrigation water before entering the field, and then flowing into the rice fields. Dry land irrigated land can also use this method.
Extra-root fertilizer refers to the method of supplying nutrients to crops through foliar spray fertilizers. The concentration of urea sprayed was 1%～2% for rice, wheat and grass, about 1% for fruit and vegetable, 0.5% for fruit trees, and 0.2% for flowers, forest seedlings, strawberries, greenhouse cucumbers, seedling nursery seedlings. . About 1 kilogram of urea per acre. Spray once every 7 to 10 days, usually 2 times, spray time is better in the evening or early morning. Crop growth and adult fruit trees can be properly increased spraying concentration, if there is no lack of nitrogen in the late crop symptoms, no need to spray urea. Foliar spray fertilizers are particularly effective for crops with poor root growth and resistance to absorption, but it is an auxiliary fertilization and cannot substitute for root fertilization.
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