Different soils have different capacities for supplying nutrients to crops due to their different parent materials, formation processes, and past fertilization and planting crops. Fertilization recommendations should be made on a piece-by-piece basis, and it is not possible to use every piece of land as a fertilizer test. Therefore, the knowledge about the upper reaches can help the technicians and producers to put forward the fertility advice under the local conditions.
The soil is formed by the combination of geological and biological processes on the earth's surface sediments. Permeate water causes slow and diffuse chemical changes, the speed of which is determined by the temperature. The fastest in the humid tropics. The roots and above-ground parts left behind by the values ​​grown on the soil add organic matter to the soil. These organics break down into humus under the action of microorganisms, insects and small animals. The original sediments determine the texture of the soil (grain and clay particles); the biological processes of weathering and soil formation determine how much of the rock's original reserves of plant nutrients are left behind; climate and soil texture determine the soil How much nitrogen does the microorganism fix in the atmosphere? Of course, the result of these processes is the natural soil. When the natural soil is reclaimed, the chemical physics and its characteristics have undergone rapid changes.
Soil surveyors usually describe the soil profile (that is, from the surface layer to the parent layer). Soil profiles can be used to determine the occurrence and development of soils and serve as the basis for soil classification. Native beauty refers to a group of soils formed from the same parent material and the same method. In addition to the huge post-effect caused by different cultivation systems, the soil of the same soil series represents the same tomb and the amount of plant nutrition available for disasters is also roughly. similar. In order to facilitate the application of soil 1 survey data, the distribution of various soils is usually plotted directly on the soil map.
"Texture" means coarse sand (particles with a diameter of 2 - 0, 2mm), fine sand (., 2-0, 02mm), silt (0,02-0, 002mm) and clay (less than 0-0, 02mm). proportion. Texture affects the physical properties of the soil and determines whether the soil is easy to cultivate, but also affects the supply of plant nutrients. Sandy soil contains less clay particles, and all nutrient cations, especially trace elements, are much less than clay. Acid is also much faster. Sandy soils also have less organic matter and nitrogen reserves because organic matter oxidizes much faster in light soils. Clay, on the other hand, usually has a much larger cation storage in the clay. After weathering, these cations can be released for use by plants, while the clay contains more nitrogen and organic matter. Clay also naturally becomes acidic like sand, but when lime is neutralized, the lime contains much more lime reserves, so the clay does not acidify as quickly as sand after application of acidic fertilizers.
The amount of crop nutrients available in the soil depends not only on the origin of the soil, but also on the aftereffects of the previous crop and the previous season. Determination of soil nutrient storage by soil analysis can be used to modify the standard fertilization recommendations.
The most common analysis is the amount of lime needed because of the neutrality of the pH. Some laboratories have used soil analyzers to test for potentially effective nitrogen in the soil. Nitrogen fertilizers have the greatest benefit. All non-legume crops require nitrogen fertilizer in agricultural production. It is better to use field nitrogen fertilizer tests as guidance for fertilization than soil analysis results. Methods for the determination of potentially effective trace elements in soil have now been developed, but they are only applied when solving special cultivation problems. The soil analysis methods and their relationship to production are mostly about phosphorus and potassium, and the general principles are equally applicable to other nutrient elements.
The method for determining potential effective nitrogen in soil is different from the method for determining water-soluble phosphorus and other nutrient cation reserves. Because the vast majority of the nitrogen left in the soil is bound to organic matter, it must be converted to mineral nitrogen (nitrogen and nitrate nitrogen) before it can be used for plants. Therefore, laboratory analysis methods have a difficult task to predict how much organic nitrogen can be converted to mineral nitrogen due to the learning process of raw pepper. This biological process depends on temperature, humidity, and other organic and inorganic conditions that affect the life activities of microorganisms. However, light conditions cannot accurately predict weather conditions. The total amount of nitrogen in the soil layer extending from the surface to the depth of centimeters is about 1,000 to 3,000 kilograms per public item, and the amount of nitrogen released per year varies between 30 to 100 kilograms per hectare, whether it is in the laboratory or not. The amount of mineral nitrogen produced by cultivating the soil, or the amount of nitrogen actually supplied to the crop, varies with the season.
Although there is a certain correlation between the available nitrogen in the laboratory and the response to the fertilizer, these methods are too unreliable for application under a wide range of conditions. The amount of nitrogen that crops can use in soil is usually only a fraction of organic matter and plant residues that are applied in the season. Therefore, the application of nitrogen fertilizers must be applied in terms of the history of cultivated land, local fertilizer test results, rotation conditions, previous fertilization and weather conditions.
Total phosphorus in the soil (generally about 20 kilopascals per hectare (P/ha) and potassium (about 10 times more)) is mostly tightly bound to soil components and cannot be used for crops. Only a small portion of the water dissolved in soil can be used by crops, which is too little for long-term supply of crops.
The development of the analytical method is mainly aimed at simplifying the method and leaching the part of the phosphorus that can be most utilized by the crop. Most are leached with an acid solution, and these methods can be satisfactorily separated by whether they are rich in phosphorus (potassium) or phosphorus (potassium). Acid extraction methods often fail for calcareous soils.
Field trials have shown that there are sufficient amounts of soluble phosphorus (or potassium) in some soils, but crops respond strongly to phosphate fertilizers, and in some soils, soluble phosphorus is extremely low, but crops still yield high yields. There is no response to phosphate fertilizers.
These contradictory phenomena have played a role in promoting the determination of soluble phosphorus and potassium by soil workers.
Using the method of radioactive phosphorus (P 2 ), it can be found out how much phosphorus in the soil is effective (that is, it can enter the soil of the king in the form of ions and can be absorbed by the crop roots).
This method can be used as a reference method to test other measurement methods in practical applications. In most countries, the use of 0.5M sodium bicarbonate solution to extract soluble phosphorus is better than other methods, and potassium is more efficiently represented by IM nitric acid solution leaching.
The results of the above two methods of analysis have been extensively compared with the field trial results of phosphorus and potash fertilizers, which shows that these two methods are superior to other methods, although the variance rarely reaches 0.5 in many one-year tests, and most of them are much lower than 0.5. . However, the soil from many field trials in the pot experiment conducted in the greenhouse, the results of these two methods are closely related to the response of the crop to phosphorus (potassium) fertilizer, and the response of the crop to fertilizer in many pot experiments. Variance and soil analysis are all in line. This means that chemical analysis can determine phosphorus and potassium that are effective in crops dissolved in soil moisture. The lack of correlation between soil analysis and field trials is due to other causes.
Correct sampling is the fundamental factor for obtaining satisfactory analysis results. One kilogram of soil for analysis is only one or two-millionth of a hectare of cultivated soil.
Therefore, if a plot of cultivated land can be seen as a difference in texture, or if it is understood that it is different from the fertilization and planting crops in the past, this piece of cultivated land should be sampled separately. In addition, the repeated determination of the soil samples of the same arable land shows that the soluble nutrients also have great changes due to different seasons.
Humidity and temperature can change the solubility of phosphorus and potassium in the soil, and more importantly, the seasonal cycle of soluble phosphorus, especially soluble potassium. Most crops can absorb large amounts of potassium, so as the crop grows, the amount of soluble potassium will gradually decrease, and high-yielding crops can absorb half or more of the soil exchangeable potassium during a growing season. During winter recreation, more potassium (phosphorus) is never dissolved, so the results of sampling and analysis in the second spring can be approximated by the number of years ago.
From this it can be seen that the results of effective soil nutrient measurements measured at any time of the year can be used to show that the soil nutrient status is incorrect. If the results of the analysis are used to predict fertilizer effects, the correct sampling time should be chosen between the maximum and the minimum of the nutrient season variation, ie the sampling should be either after the autumn crop has just been harvested or before the spring crop is sown.
Repeated sampling and measurements over long-term test sites show that as long as the representative soil sample is carefully taken at the appropriate time of year, the amount of soluble phosphorus and potassium measured by modern reliable analytical methods is very reproducible. . In the laboratory, soluble nutrients are extracted from a certain weight of ground soil by an extractant.
However, the amount of phosphorus and potassium available in field crops also depends on the weather, other soil conditions, and the amount of grounded soil capacity. For these reasons, it cannot be expected that crop performance in field trials will only closely correlate with soil analysis results (in pot trials, crop root systems are usually confined to one pot of soil, so the correlation is very close).
Both water availability and temperature can change the solubility of nutrients in the soil, which in turn changes the amount of nutrients available to the plant. In moist, warm soil, available phosphorus is higher than dry and cool soil. In interpreting soil moisture results, the amount of nutrients in the plant rhizosphere soil is usually taken as a fixed value. In addition, the actual depth of soil used by certain crops, that is, the total amount of effective nutrients, is not only different for different cultivated lands, but also for the same spelling in different years. Because the root penetration depth is determined by soil compaction, the soil compaction is not the same in different years due to different farming practices, animal trampling and weather conditions. The amount of soil particles that come in contact with the root system also affects the absorption of nutrient ions with low mobility. Phosphorus is almost completely non-removable. Potassium mobility is small, and nitrate nitrogen is easy to move. Therefore, the soil structure condition also affects the absorption of nutrients. Large and hard soil structure causes a very thick system, which reduces the absorption of phosphorus, but has no effect on nitrate nitrogen.
Different climates, seasons, types of crops, soil management, and fertilization methods can all alter the response of crops to fertilizers. Weather and farming conditions also change the value of phosphorus and potassium in the soil to crops. Therefore, in practice, a certain amount of phosphate fertilizer and potash fertilizer, as well as a certain amount of available phosphorus and potassium in the soil, have different effects on crop yield at different years.
A certain amount of soluble phosphorus and potassium in the soil, seasonal changes in crop effects will lead to changes in fertilizer efficiency.
This point shows that in the absence of the opportunity to repeat the trials in different seasons, only a one-year test to determine the effect of fertilizer will be a great change. Therefore, 'according to the results of one-year trials of phosphorus and potassium fertilizers as a basis for specific farmland fertilization recommendations, it is not appropriate and it may often be wrong. When the amount of soluble phosphorus and potassium in the soil is very low, it may have a fertilizer effect (but not necessarily as significant as that of soils lacking phosphorus and potassium). Based on this, the real fertilizer effect and appropriate fertilizer recommendation are also available in different years. Great changes, and this change is not yet predictable. Therefore, in agricultural systems that use a large amount of fertilizers, fertilization recommendations are made based on one-year field trials. The amount of fertilization planned should be such that the phosphorus and potassium in the soil are sufficient to maintain crop growth.
If a series of large-scale field trials were conducted, the average analysis results were well correlated with the average fertilizer effect. If the soils were grouped by the analysis results with equal distance, the correlation would be better. In the trial of phosphorus and potash fertilizer effects in a series of plots with different soluble phosphorus and potassium dungeons, if the data were processed individually, the distribution of points was very fragmented and often could not express two clear tendencies. '
Summarizing the above discussion: Most of the earlier work on soil analysis results and crop response was relatively poor in many field trials. The reason was considered to be the shortcomings of soil analysis methods, and the crop responses measured in field trials were considered to be correct. When using acid to extract soluble phosphorus from calcareous soils, it should be attributed to soil analysis methods, but it would be wrong if all were attributed to soil analysis methods rather than field trials.
In fact, the amount of soil phosphorus that can be used by crops in the field can be properly regulated, but its significance for crops changes due to differences in the year and climbing season.
The soil is formed by the combination of geological and biological processes on the earth's surface sediments. Permeate water causes slow and diffuse chemical changes, the speed of which is determined by the temperature. The fastest in the humid tropics. The roots and above-ground parts left behind by the values ​​grown on the soil add organic matter to the soil. These organics break down into humus under the action of microorganisms, insects and small animals. The original sediments determine the texture of the soil (grain and clay particles); the biological processes of weathering and soil formation determine how much of the rock's original reserves of plant nutrients are left behind; climate and soil texture determine the soil How much nitrogen does the microorganism fix in the atmosphere? Of course, the result of these processes is the natural soil. When the natural soil is reclaimed, the chemical physics and its characteristics have undergone rapid changes.
Soil surveyors usually describe the soil profile (that is, from the surface layer to the parent layer). Soil profiles can be used to determine the occurrence and development of soils and serve as the basis for soil classification. Native beauty refers to a group of soils formed from the same parent material and the same method. In addition to the huge post-effect caused by different cultivation systems, the soil of the same soil series represents the same tomb and the amount of plant nutrition available for disasters is also roughly. similar. In order to facilitate the application of soil 1 survey data, the distribution of various soils is usually plotted directly on the soil map.
"Texture" means coarse sand (particles with a diameter of 2 - 0, 2mm), fine sand (., 2-0, 02mm), silt (0,02-0, 002mm) and clay (less than 0-0, 02mm). proportion. Texture affects the physical properties of the soil and determines whether the soil is easy to cultivate, but also affects the supply of plant nutrients. Sandy soil contains less clay particles, and all nutrient cations, especially trace elements, are much less than clay. Acid is also much faster. Sandy soils also have less organic matter and nitrogen reserves because organic matter oxidizes much faster in light soils. Clay, on the other hand, usually has a much larger cation storage in the clay. After weathering, these cations can be released for use by plants, while the clay contains more nitrogen and organic matter. Clay also naturally becomes acidic like sand, but when lime is neutralized, the lime contains much more lime reserves, so the clay does not acidify as quickly as sand after application of acidic fertilizers.
The amount of crop nutrients available in the soil depends not only on the origin of the soil, but also on the aftereffects of the previous crop and the previous season. Determination of soil nutrient storage by soil analysis can be used to modify the standard fertilization recommendations.
The most common analysis is the amount of lime needed because of the neutrality of the pH. Some laboratories have used soil analyzers to test for potentially effective nitrogen in the soil. Nitrogen fertilizers have the greatest benefit. All non-legume crops require nitrogen fertilizer in agricultural production. It is better to use field nitrogen fertilizer tests as guidance for fertilization than soil analysis results. Methods for the determination of potentially effective trace elements in soil have now been developed, but they are only applied when solving special cultivation problems. The soil analysis methods and their relationship to production are mostly about phosphorus and potassium, and the general principles are equally applicable to other nutrient elements.
The method for determining potential effective nitrogen in soil is different from the method for determining water-soluble phosphorus and other nutrient cation reserves. Because the vast majority of the nitrogen left in the soil is bound to organic matter, it must be converted to mineral nitrogen (nitrogen and nitrate nitrogen) before it can be used for plants. Therefore, laboratory analysis methods have a difficult task to predict how much organic nitrogen can be converted to mineral nitrogen due to the learning process of raw pepper. This biological process depends on temperature, humidity, and other organic and inorganic conditions that affect the life activities of microorganisms. However, light conditions cannot accurately predict weather conditions. The total amount of nitrogen in the soil layer extending from the surface to the depth of centimeters is about 1,000 to 3,000 kilograms per public item, and the amount of nitrogen released per year varies between 30 to 100 kilograms per hectare, whether it is in the laboratory or not. The amount of mineral nitrogen produced by cultivating the soil, or the amount of nitrogen actually supplied to the crop, varies with the season.
Although there is a certain correlation between the available nitrogen in the laboratory and the response to the fertilizer, these methods are too unreliable for application under a wide range of conditions. The amount of nitrogen that crops can use in soil is usually only a fraction of organic matter and plant residues that are applied in the season. Therefore, the application of nitrogen fertilizers must be applied in terms of the history of cultivated land, local fertilizer test results, rotation conditions, previous fertilization and weather conditions.
Total phosphorus in the soil (generally about 20 kilopascals per hectare (P/ha) and potassium (about 10 times more)) is mostly tightly bound to soil components and cannot be used for crops. Only a small portion of the water dissolved in soil can be used by crops, which is too little for long-term supply of crops.
The development of the analytical method is mainly aimed at simplifying the method and leaching the part of the phosphorus that can be most utilized by the crop. Most are leached with an acid solution, and these methods can be satisfactorily separated by whether they are rich in phosphorus (potassium) or phosphorus (potassium). Acid extraction methods often fail for calcareous soils.
Field trials have shown that there are sufficient amounts of soluble phosphorus (or potassium) in some soils, but crops respond strongly to phosphate fertilizers, and in some soils, soluble phosphorus is extremely low, but crops still yield high yields. There is no response to phosphate fertilizers.
These contradictory phenomena have played a role in promoting the determination of soluble phosphorus and potassium by soil workers.
Using the method of radioactive phosphorus (P 2 ), it can be found out how much phosphorus in the soil is effective (that is, it can enter the soil of the king in the form of ions and can be absorbed by the crop roots).
This method can be used as a reference method to test other measurement methods in practical applications. In most countries, the use of 0.5M sodium bicarbonate solution to extract soluble phosphorus is better than other methods, and potassium is more efficiently represented by IM nitric acid solution leaching.
The results of the above two methods of analysis have been extensively compared with the field trial results of phosphorus and potash fertilizers, which shows that these two methods are superior to other methods, although the variance rarely reaches 0.5 in many one-year tests, and most of them are much lower than 0.5. . However, the soil from many field trials in the pot experiment conducted in the greenhouse, the results of these two methods are closely related to the response of the crop to phosphorus (potassium) fertilizer, and the response of the crop to fertilizer in many pot experiments. Variance and soil analysis are all in line. This means that chemical analysis can determine phosphorus and potassium that are effective in crops dissolved in soil moisture. The lack of correlation between soil analysis and field trials is due to other causes.
Correct sampling is the fundamental factor for obtaining satisfactory analysis results. One kilogram of soil for analysis is only one or two-millionth of a hectare of cultivated soil.
Therefore, if a plot of cultivated land can be seen as a difference in texture, or if it is understood that it is different from the fertilization and planting crops in the past, this piece of cultivated land should be sampled separately. In addition, the repeated determination of the soil samples of the same arable land shows that the soluble nutrients also have great changes due to different seasons.
Humidity and temperature can change the solubility of phosphorus and potassium in the soil, and more importantly, the seasonal cycle of soluble phosphorus, especially soluble potassium. Most crops can absorb large amounts of potassium, so as the crop grows, the amount of soluble potassium will gradually decrease, and high-yielding crops can absorb half or more of the soil exchangeable potassium during a growing season. During winter recreation, more potassium (phosphorus) is never dissolved, so the results of sampling and analysis in the second spring can be approximated by the number of years ago.
From this it can be seen that the results of effective soil nutrient measurements measured at any time of the year can be used to show that the soil nutrient status is incorrect. If the results of the analysis are used to predict fertilizer effects, the correct sampling time should be chosen between the maximum and the minimum of the nutrient season variation, ie the sampling should be either after the autumn crop has just been harvested or before the spring crop is sown.
Repeated sampling and measurements over long-term test sites show that as long as the representative soil sample is carefully taken at the appropriate time of year, the amount of soluble phosphorus and potassium measured by modern reliable analytical methods is very reproducible. . In the laboratory, soluble nutrients are extracted from a certain weight of ground soil by an extractant.
However, the amount of phosphorus and potassium available in field crops also depends on the weather, other soil conditions, and the amount of grounded soil capacity. For these reasons, it cannot be expected that crop performance in field trials will only closely correlate with soil analysis results (in pot trials, crop root systems are usually confined to one pot of soil, so the correlation is very close).
Both water availability and temperature can change the solubility of nutrients in the soil, which in turn changes the amount of nutrients available to the plant. In moist, warm soil, available phosphorus is higher than dry and cool soil. In interpreting soil moisture results, the amount of nutrients in the plant rhizosphere soil is usually taken as a fixed value. In addition, the actual depth of soil used by certain crops, that is, the total amount of effective nutrients, is not only different for different cultivated lands, but also for the same spelling in different years. Because the root penetration depth is determined by soil compaction, the soil compaction is not the same in different years due to different farming practices, animal trampling and weather conditions. The amount of soil particles that come in contact with the root system also affects the absorption of nutrient ions with low mobility. Phosphorus is almost completely non-removable. Potassium mobility is small, and nitrate nitrogen is easy to move. Therefore, the soil structure condition also affects the absorption of nutrients. Large and hard soil structure causes a very thick system, which reduces the absorption of phosphorus, but has no effect on nitrate nitrogen.
Different climates, seasons, types of crops, soil management, and fertilization methods can all alter the response of crops to fertilizers. Weather and farming conditions also change the value of phosphorus and potassium in the soil to crops. Therefore, in practice, a certain amount of phosphate fertilizer and potash fertilizer, as well as a certain amount of available phosphorus and potassium in the soil, have different effects on crop yield at different years.
A certain amount of soluble phosphorus and potassium in the soil, seasonal changes in crop effects will lead to changes in fertilizer efficiency.
This point shows that in the absence of the opportunity to repeat the trials in different seasons, only a one-year test to determine the effect of fertilizer will be a great change. Therefore, 'according to the results of one-year trials of phosphorus and potassium fertilizers as a basis for specific farmland fertilization recommendations, it is not appropriate and it may often be wrong. When the amount of soluble phosphorus and potassium in the soil is very low, it may have a fertilizer effect (but not necessarily as significant as that of soils lacking phosphorus and potassium). Based on this, the real fertilizer effect and appropriate fertilizer recommendation are also available in different years. Great changes, and this change is not yet predictable. Therefore, in agricultural systems that use a large amount of fertilizers, fertilization recommendations are made based on one-year field trials. The amount of fertilization planned should be such that the phosphorus and potassium in the soil are sufficient to maintain crop growth.
If a series of large-scale field trials were conducted, the average analysis results were well correlated with the average fertilizer effect. If the soils were grouped by the analysis results with equal distance, the correlation would be better. In the trial of phosphorus and potash fertilizer effects in a series of plots with different soluble phosphorus and potassium dungeons, if the data were processed individually, the distribution of points was very fragmented and often could not express two clear tendencies. '
Summarizing the above discussion: Most of the earlier work on soil analysis results and crop response was relatively poor in many field trials. The reason was considered to be the shortcomings of soil analysis methods, and the crop responses measured in field trials were considered to be correct. When using acid to extract soluble phosphorus from calcareous soils, it should be attributed to soil analysis methods, but it would be wrong if all were attributed to soil analysis methods rather than field trials.
In fact, the amount of soil phosphorus that can be used by crops in the field can be properly regulated, but its significance for crops changes due to differences in the year and climbing season.
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