In the three-factor test conducted in the 1950s, potassium was effective. At the end of the 1950s, rubber trees showed symptoms of potassium deficiency. After entering the mid-1960s, some soils with low potassium levels in southern China, cement kiln ash and potassium fertilizers were applied to rice and other crops, showing good results. After the early 1970s, more potent soils were available for potash. Now in the southern region, potash has been deeply rooted in the hearts of the people and has been welcomed by farmers. At present, potassium fertilizer has also shown good results in some soils and crops in North China. But in general, the amount of potash applied in China is still very small. In 1985/1986, China was the country with the most nitrogen fertilizer, accounting for 19% of the world; the application of phosphate fertilizer accounted for the third place in the world, accounting for 9% of the world; and the application of potassium fertilizer was the fifteenth in the world, accounting for the world. 1.4%. Fortunately, after 1987, the amount of potassium fertilizer applied in China has increased significantly. The demand for potash will continue to grow in the future. Therefore, further increasing the source of potash and using potash are an important issue in agricultural production.
The important role of potash fertilizer in agricultural production
(1) Maintaining high soil potassium fertility is the basis for high yield and stable yield
The amount of potassium required by crops is often higher than that of nitrogen and phosphorus. The potassium absorbed by the crop comes from the soil and the applied potash. Before the 1970s, there was basically no supply of chemical potassium fertilizer in China. The balance of potassium in farmland soil was maintained by the natural supply of farmyard manure and soil potassium. Because the previous multiple cropping index and yield are not high, the crops take less potassium per year, and this low potassium balance is maintained. With the rapid development of agriculture, the expenditure in the soil is accumulated, and the imbalance is serious. For example, a large number of experiments and surveys conducted by the Nanjing Institute of Soil Science of the Chinese Academy of Sciences show that the total nutrient balance of farmland in the Taihu Lake region is that the nitrogen and phosphorus are basically balanced and have a slight surplus, while the potassium is heavily depleted, with an annual deficit of 52.5 kg/ha ( Equivalent to 3.5 kg/mu); in the suburbs of Shanghai, Zhejiang Hangzhou-Jiaxing-Huzhou Plain and Fujian low-yield areas, potassium is deficient, with an annual deficit of 30-75 kg/ha (relative to 2-5 kg/mu) . Because soil potassium has not been replenished for a long time, the contradiction of potassium deficiency has been exposed recently. It is estimated that several areas in the south estimate that the area of ​​potassium deficiency accounts for about 60%. Therefore, potassium fertilizer should be added to supplement the loss of soil potassium to establish Higher potassium balance, maintaining higher soil potassium fertility, providing a material basis for high yield and stable yield of crops.
(2) Potassium can enhance the stress resistance of crops, and potassium can make crops grow robustly.
In 1998, some areas of China continued to suffer from drought, and the effect of potash on winter rapeseed was unprecedented. This shows that potassium plays a significant role in enhancing the drought resistance of crops. When the potassium supply is sufficient, the root system is well developed, which is beneficial to absorb water from the soil; potassium can increase the osmotic pressure of the cell liquid, maintain the elasticity of the fine wall, and reduce the loss of water; potassium is also important for the regulation of stomatal opening and closing. The effect is to reduce water evaporation when potassium is sufficient.
When potassium is sufficient, the cell wall is thickened, the stem is tough, the mechanical resistance against parasite penetration is increased, and the low molecular weight compound in the crop is reduced. The pathogen lacks a food source, which prevents the development of the disease. Therefore, the role of potassium in enhancing crop disease resistance is very obvious. In some areas where severe nitrogen fertilizers cause serious diseases in China, the disease is greatly reduced after the application of potassium fertilizer, so there is a saying that “potassium fertilizer is like pesticideâ€.
In addition, potassium enhances the crop's ability to resist pests, freeze damage and resist adverse soil conditions.
(3) Increasing the application of potassium fertilizer can improve the quality of crops
Potassium can promote photosynthesis, improve photosynthetic efficiency, and promote the transportation of photosynthetic products. When potassium is sufficient, monosaccharides are carried out to the synthesis of sucrose and starch, so potassium has a good influence on the yield and quality of starch and sugar crops. Potassium also promotes the absorption and utilization of nitrogen by crops and promotes protein synthesis. Therefore, the supply of potassium is sufficient, which not only increases the yield, but also increases the protein content in the grain and improves the quality. The good effect of potassium in improving product quality, in addition to the improvement of basic nutrients (such as protein, carbohydrates, etc.), can also increase mineral content, improve the appearance of the fruit and increase the storage stability of the fruit.
Practice has proved that the adverse effects of single application of nitrogen fertilizer can be improved to varying degrees by applying potassium fertilizer. Potassium application sometimes does not necessarily increase yield, but it does a good job of improving quality. With the improvement of people's living standards and the rate of agricultural products, the quality of products is more important, especially in order to occupy the international market, and the higher quality requirements should play the role of potash in this respect.
(4) Applying potassium fertilizer and adjusting the proportion of nutrients can fully exert the effects of other fertilizers
The nutrients needed for crops are roughly proportional to the ratio of nitrogen, bowl and potassium absorbed by rice to 2:1:2.5 (n:p2o5:k2o). When the nutrient supply is out of balance, it will affect the normal growth and development of the crop. Therefore, the balanced supply of various nutrients is a necessary condition for high yield of crops, and the proportion of nitrogen, phosphorus and potassium fertilizers is also an indicator to measure the level of agricultural development.
In recent years, the application of nitrogen fertilizer alone in some potassium-deficient soils has been unable to increase production, or the effectiveness of nitrogen fertilizer has decreased. Potassium is poor in soil, and the imbalance of nitrogen and potassium nutrients is one of the reasons for the decline in nitrogen fertilizer utility. For example, a rice test showed that when the amount of n increased from 2.1 kg (4.2 kg) to 4.2 kg (8.4 kg) and 6.3 kg (12.6 kg), the rice yield decreased from 286 kg (572 kg) to 269 kg (538 kg). And 255 kg (510 kg), after acid application of potassium fertilizer, it rose to 340 kg (680 kg), 346 kg (692 kg) and 355 kg (710 kg). In order to give full play to the effectiveness of chemical fertilizers, balanced application of nitrogen, phosphorus and potassium should be achieved when soil nutrient supply is insufficient.
Potassium supply level and potassium requirement in different regions of China
The effect and extent of potash is mainly determined by the level of potassium supply in the soil. Understanding the status of potassium supply in different regions can provide a basis for the allocation and rational application of potassium fertilizer.
(1) Soil potassium content and influencing factors
The total potassium (k2o) content in the soil is generally about 0.3 to 2.5%. If all of the potassium is in an effective state, it can be used for one or two hundred years. It is a pity that most of the top (more than 98%) of the potassium in the soil is present in the soil minerals, and the crop is extremely difficult to use. We call it mineral potassium, which is the first form and the main body of the soil. The second form of potassium is slow-acting potassium, which usually accounts for about 2% of total potassium. It can be gradually released and is a reserve of available potassium. When assessing the long-term potassium supply potential of the soil, the potassium content and conversion rate of this form should be considered primarily. The third form of potassium is available potassium, which is mainly exchangeable potassium, and also includes a small amount of water-soluble potassium. It only accounts for 0.1~2% of the total potassium, which is mainly used in the crop season.
The content of various forms of potassium in different soils varies greatly, which is mainly due to the difference in soil parent material and weathering conditions. In northern China, the weathering effect is weak. No matter what kind of soil is formed on the parent rock, the clay part of the clay has a large amount of hydromica and a montmorillonite mineral with strong ability to maintain exchangeable potassium. In addition to low content, the general potassium supply capacity is high.
In the south of the Yangtze River, due to the gradual enhancement of weathering and leaching, the water mica in the clay is gradually reduced, while the kaolin minerals and the trihydrate aluminum mine, which do not contain potassium and have poor potassium retention capacity, gradually increase, so the soil is dehydrated. Gradually obvious. The degree of potassium deficiency in the same climatic conditions is closely related to the parent rock. In addition, soils developed from alluvial deposits and sediments often have different potassium supply capacities due to differences in soil material sources and textures.
(II) Overview of potassium supply and potassium demand in different regions
1. Brick red soil area: brick red soil and red soil (except those developed by granite and metamorphic rocks) and paddy soil formed during the period, which is the most prominent soil in the zonal soil in China. In particular, soils developed from shallow sea sediments and basalts contain low levels of potassium. The large-scale application of potash in China begins with this area. Currently, various tropical economic forests and crops need to be applied with potash. This is also a region where high potency can be achieved by applying potassium fertilizer.
2. Yellow soil area: From the national point of view, the potential for potassium supply in this area is also low. For example, the soil developed by limestone in Guangxi, the soil developed by red sandstone in Jiangxi and Hunan is the lowest level of potassium in the region, so the potash The effect is also the most significant. The soil developed by the Quaternary red clay in the hilly area is also very demanding for potash. The soil developed by river alluvials has higher potassium levels than red soil, and lake sediments are generally higher than alluvial deposits.
3. Saline area: Neutral and calcareous purple soil developed by purple shale in parts of southwest and central China. It is a soil with higher potassium supply in the south, but acid purple soil has lower potassium content and potassium has been applied. Report on the effect.
4. The middle and lower reaches of the Yangtze River: This area is paddy soil developed by alluvial and lake sediments and yellow brown soil. Its potassium potential is lower than that of North China and Northwest China, but higher than that of Central China. At present, the high-yield Taihu paddy soil area has begun to show the effect of potash fertilizer, especially for dry crop wheat and rapeseed.
5. North China Plain: The potassium supply level of calcareous soil in this area varies by texture. Viscous fluvo-aquic soil has a high potassium content and does not require potassium fertilizer at present. Sandy soils have moderate levels of potassium, and some crops are effective in applying potassium. The slightly acidic brown soil is the soil with lower potassium supply in the region. In general, the potash fertilizer efficiency of some soils in North China has increased.
6. Northwest Loess Area: The bauxite and black soil in this area are affected by the loess parent material, and the potential for potassium supply is high. At present, there is little obvious response to the application of potash.
7. Black soil region in Northeast China: Black soil and chernozem are rich in potassium, and the multiple cropping index in this region is not high. Except for special crops, potassium fertilizer is generally not needed, but grass carbon soil is an exception.
8. Desert areas: The soil in this area is the soil with the highest potassium supply in China.
Ways to improve the effectiveness of potassium fertilizer
(1) Soil potassium content and influencing factors
The total potassium (k2o) content in the soil is generally about 0.3 to 2.5%. If all of the potassium is in an effective state, it can be used for one or two hundred years. It is a pity that most of the top (more than 98%) of the potassium in the soil is present in the soil minerals, and the crop is extremely difficult to use. We call it mineral potassium, which is the first form and the main body of the soil. The second form of potassium is slow-acting potassium, which usually accounts for about 2% of total potassium. It can be gradually released and is a reserve of available potassium. When assessing the long-term potassium supply potential of the soil, the potassium content and conversion rate of this form should be considered primarily. The third form of potassium is available potassium, which is mainly exchangeable potassium, and also includes a small amount of water-soluble potassium. It only accounts for 0.1~2% of the total potassium, which is mainly used in the crop season.
The content of various forms of potassium in different soils varies greatly, which is mainly due to the difference in soil parent material and weathering conditions. In northern China, the weathering effect is weak. No matter what kind of soil is formed on the parent rock, the clay part of the clay has a large amount of hydromica and a montmorillonite mineral with strong ability to maintain exchangeable potassium. In addition to low content, the general potassium supply capacity is high.
In the south of the Yangtze River, due to the gradual enhancement of weathering and leaching, the water mica in the clay is gradually reduced, while the kaolin minerals and the trihydrate aluminum mine, which do not contain potassium and have poor potassium retention capacity, gradually increase, so the soil is dehydrated. Gradually obvious. The degree of potassium deficiency in the same climatic conditions is closely related to the parent rock. In addition, by alluvial
(II) Overview of potassium supply and potassium demand in different regions
1. Brick red soil area: brick red soil and red soil (except those developed by granite and metamorphic rocks) and paddy soil formed during the period, which is the most prominent soil in the zonal soil in China. In particular, soils developed from shallow sea sediments and basalts contain low levels of potassium. The large-scale application of potash in China begins with this area. Currently, various tropical economic forests and crops need to be applied with potash. This is also a region where high potency can be achieved by applying potassium fertilizer.
2. Yellow soil area: From the national point of view, the potential for potassium supply in this area is also low. For example, the soil developed by limestone in Guangxi, the soil developed by red sandstone in Jiangxi and Hunan is the lowest level of potassium in the region, so the potash The effect is also the most significant. The soil developed by the Quaternary red clay in the hilly area is also very demanding for potash. The soil developed by river alluvials has higher potassium levels than red soil, and lake sediments are generally higher than alluvial deposits.
3. Saline area: Neutral and calcareous purple soil developed by purple shale in parts of southwest and central China. It is a soil with higher potassium supply in the south, but acid purple soil has lower potassium content and potassium has been applied. Report on the effect.
4. The middle and lower reaches of the Yangtze River: This area is paddy soil developed by alluvial and lake sediments and yellow brown soil. Its potassium potential is lower than that of North China and Northwest China, but higher than that of Central China. At present, the high-yield Taihu paddy soil area has begun to show the effect of potash fertilizer, especially for dry crop wheat and rapeseed.
5. North China Plain: The potassium supply level of calcareous soil in this area varies by texture. Viscous fluvo-aquic soil has a high potassium content and does not require potassium fertilizer at present. Sandy soils have moderate levels of potassium, and some crops are effective in applying potassium. The slightly acidic brown soil is the soil with lower potassium supply in the region. In general, the potash fertilizer efficiency of some soils in North China has increased.
6. Northwest Loess Area: The bauxite and black soil in this area are affected by the loess parent material, and the potential for potassium supply is high. At present, there is little obvious response to the application of potash.
7. Black soil region in Northeast China: Black soil and chernozem are rich in potassium, and the multiple cropping index in this region is not high. Except for special crops, potassium fertilizer is generally not needed, but grass carbon soil is an exception.
8. Desert areas: The soil in this area is the soil with the highest potassium supply in China.
Ways to improve the effectiveness of potassium fertilizer
About one-third of China's cultivated land is currently deficient in potassium, which requires a large amount of potash. Now, the source of potash is limited, and how to apply it reasonably to obtain greater benefits is an important issue in current rational fertilization. The existing experience is briefly described below.
(1) Coadministration with nitrogen and phosphate fertilizers
In the same soil, when the nitrogen and phosphorus nutrients are low, or the nitrogen and phosphorus fertilizers are used in a small amount, and the production level is not high, the problem of potassium will not be prominent. With the increase in the amount of nitrogen and phosphorus fertilizers and the increase in production, the need for potash fertilizer will become increasingly apparent. For 40 years, the development of agriculture has fully confirmed this point. A large number of experiments have shown that rice can generally increase yield by about 15% when potassium fertilizer is applied on the basis of nitrogen and phosphorus fertilizers. At present, in some areas, the effect of nitrogen fertilizer has a downward trend. One of the reasons is that there is no attention to the application of potassium fertilizer, and the proportion of nitrogen and potassium is imbalanced. Therefore, in production practice, attention must be paid to balanced fertilization.
(2) Applying potassium fertilizer to cold soaked fields
Potassium fertilizer is applied to the poor cold-soaked field under soil environmental conditions. The rice roots have increased the oxidative power of the roots due to the improvement of potassium nutrients, thus reducing the content of reducing substances in the soil and increasing the redox potential. Or reduce the damage of sulfides, organic acids and ferrous iron, which is conducive to the growth of rice. Therefore, the application of potash fertilizer in cold soaked fields often results in good results.
(3) Reasonable distribution of potash in the rotation
In the double-season rice and wheat one-season rice rotation system, the application of potassium fertilizer has a great effect on the post-season rice and wheat. The effect of potassium fertilizer on late rice is more than that of upland rice, which is mainly related to the difference of soil potassium supply during the growth period of dry and late rice. For example, a test showed that the soil available potassium content was 9.9 mg when transplanted in early rice, and decreased to 4.3 mg at the time of ripening. Soil potassium could not be restored and then ploughed and planted late rice, while late rice generally used less organic fertilizer. Late rice has a greater effect on potassium application. When potassium fertilizer is limited, it should first be ensured in late rice application.
(4) Pay attention to the application of potassium in Putian
As the saying goes: "Half of the rice is good," which indicates that the quality of the seedlings will affect the growth and development of rice. After the robust seedlings are transplanted into the field, they will return to the green quickly, branching early, and having many leaves, which have obvious effects on increasing yield. Potassium fertilizer has a good effect on cultivating Zhuang. In the case of the same amount of potassium fertilizer, the application of Putian and Datian separately, compared with all of them applied to the field, often has a significant yield increase effect. The experiment in Jiangxi showed that in the case of the total amount of potassium chloride being 7.5 kg (15 kg)/mu, Putian and Datian were applied 2.5 kg (5 kg) and 5 kg (10 kg) respectively than 7.5 kg (15 kg). Compared with Datian, the output was 357.3 kg (714.6 kg) and 318.7 kg (637.4 kg), respectively, which increased production by 11%.
(5) The effect of applying potash fertilizer on cash crops
Cash crops are generally sensitive to potassium fertilizers and require large amounts. For example, high yield of sugar cane absorbs about k2o40~53kg (80~106kg) per mu, banana about 95kg (190kg), and 500kg (1000kg) of rice absorbs only 10kg (20kg). Potassium fertilizer can not only increase production, but also improve product quality. In the soil where cash crops are cultivated, the level of potassium supply is often low, so the development of cash crops requires a large amount of potash.
(6) Applying different varieties of potash according to crop characteristics
Potassium chloride and potassium sulfate are commonly used potassium fertilizer varieties, and in recent years, NEW sulfur and potassium fertilizers have been imported. The price of potassium sulphate and sulphur potassium magnesium fertilizer is higher than that of potassium chloride, and the amount is small, and it does not contain chlorine. It should be mainly used for avoiding chlorine crops, such as tobacco, and potassium chloride can be widely used for a few crops other than tobacco. On the crop.
(7) pay attention to application technology
The application rate of potassium fertilizer and the application period are also important for improving the potash fertilizer effect. Each crop has its best suitable potassium fertilizer dosage. If it is applied more, the crop will be extravagantly absorbed. Generally, it will not be harmful, but it is not economical. For most crops, potash is preferred as base fertilizer, and some crops are better combined with base fertilizer and previous top dressing. When the plant has obvious potassium deficiency, the application is also effective, but the yield and quality of the crop have been significantly damaged. Because the clay minerals of the southern soil are mainly kaolin, its adsorption capacity for potassium is weak, while the rain in the south is more, the applied potassium fertilizer is easily leached, and the fertility of sandy soil is also weak, so on these soils. Partial application should be emphasized to reduce the loss of potassium.
(8) Try to use organic fertilizers, especially masts and ash
China's potash resources are lacking, and a large amount of potash fertilizer is imported. In addition to the proper application of potash fertilizer, it is necessary to take local materials and increase the source of potash. In areas where conditions permit, grass ash should be strongly promoted, and in areas where conditions are available, the return of the stalks is also an important measure to supplement potash.
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