The reason why the elements in the soil cannot be absorbed

The soil originally contains this element, and the plant cannot be absorbed for various reasons.

 

details as follows:

 

1. Drought: When water is absent, the element cannot be dissolved or oxidized, and the root cannot be absorbed. Therefore, the deficiency syndrome often occurs in dry years or dry seasons.

 

Second, the soil reaction (ph) discomfort: soil reaction strongly affects the solubility of nutrients, that is, effectiveness. Some elements are easily soluble under acidic conditions, have high effectiveness, are highly effective, and have a solubility-effectiveness when the reaction tends to be neutral or alkaline. Other elements, on the other hand, are highly effective under alkaline conditions and less effective under acidic conditions. Particularly closely related to the reaction are trace elements. For example, iron, boron, zinc, and copper decrease in solubility (before pH 4.5), and the effectiveness increases rapidly. When the pH is near neutral or alkaline, the effectiveness decreases. Molybdenum is the opposite. Increase with increasing pH. A large number of elements are generally slow to react with pH, ​​but phosphorus is the exception. The suitable pH range of phosphorus is extremely narrow. Strictly speaking, it is only fixed at pH 6.5, <6.5 and iron and aluminum in soil, and the lower the pH. The greater the solubility of iron and aluminum, the more the fixed amount, > 6.5 is combined with the calcium in the soil, and the effectiveness is also reduced. However, the solubility of calcium phosphate is greater than that of iron phosphate and aluminum, so the effectiveness of phosphorus in alkaline soils is usually higher than that of acid soil.

 

The optimum pH of nitrogen is 6-8.

 

The optimum pH of phosphorus is 6.5 to 7.5 or 8.5 or more.

 

The optimum pH of potassium is 6 to 7.5.

 

The optimum pH of sulfur is in the direction of 6 or more to the alkali.

 

The optimum pH of calcium is 6.5 to 8.5.

 

The optimum pH of magnesium is 6.5 to 8.5.

 

The optimum pH of iron should be in the direction of acid below 6.5.

 

The optimum pH of boron is 5-7.

 

The optimum pH of manganese is 5~6.5

 

The optimum pH of zinc and copper is 5-7.

 

The optimum pH of molybdenum should be in the direction of 6 or more to the alkali.

 

Third, adsorption fixation: that is, nutrients are adsorbed and fixed by inorganic or organic matter, but not for root absorption. The adsorption fixation of each element is closely related to soil or soil parent material.

 

Table 16 Adsorption and fixation of elements in parent soil and soil

 

Parent material, soil, fixed element

 

Peat soil, humus soil P K Ca B Mn Mo Zn Cu

 

Alkaline soil, soda clay Ca Mg Fe B Zn Cu

 

Calcareous soil P Mn B Cu

 

Soil with more organic matter Mn Zn Cu

 

Soil developed by granite and gneiss Zn Mo

 

Soil developed by loess parent material (cosm of montmorillonite) B Ca Cu

 

Paddy soil Zn

 

Meteorite, Chilean stone K B

 

Acidic soil of iron nodules Mo

 

Fourth, the inconsistency between elements

 

1. Nitrogen; absorption of nitrate nitrogen is more difficult than absorption of ammonia nitrogen; application of excess potassium and phosphorus affects nitrogen absorption; boron deficiency is not conducive to nitrogen absorption.

 

2. Phosphorus: increasing zinc can reduce the absorption of phosphorus; polynitrogen is not conducive to the absorption of phosphorus; iron also has an antagonistic effect on the absorption of phosphorus; the addition of lime can make phosphorus into an unacceptable state; magnesium can promote the absorption of phosphorus.

 

3. Potassium: increasing boron promotes the absorption of potassium, zinc can reduce the absorption of potassium; polynitrogen is not conducive to the absorption of potassium; calcium and magnesium have an antagonistic effect on the absorption of potassium.

 

4. Calcium: Potassium affects the absorption of calcium and reduces the level of calcium nutrition; magnesium affects the transport of calcium, magnesium and boron have an antagonistic effect on calcium; ammonium salt can reduce the absorption of calcium, reduce the transfer of calcium to fruits; Sulfur can also reduce the absorption of calcium; increasing the aluminum, manganese and nitrogen in the soil will also reduce the absorption of calcium.

 

5. Magnesium; potassium affects the absorption of magnesium. A large amount of sodium and phosphorus is not conducive to the absorption of magnesium, and polynitrogen can cause magnesium deficiency. Magnesium and calcium, potassium, ammonium, hydrogen have antagonistic effects, and the addition of sulfates can cause magnesium deficiency. Magnesium can eliminate the toxicity of calcium. Magnesium deficiency is easy to induce zinc deficiency and manganese deficiency. Magnesium and zinc have mutually reinforcing effects.

 

6. Iron: Polyboron affects the absorption of iron and reduces the iron content in plants. Nitrate nitrogen affects the absorption of iron. Vanadium and iron have antagonistic effects, causing more iron-deficient elements. Their order is Ni>Cu> Co>Gr>Zn>Mo>Mn

 

Insufficient potassium can cause iron deficiency; large amounts of nitrogen, phosphorus and calcium can cause iron deficiency.

 

7. Boron: Iron and aluminum oxides can cause boron deficiency; aluminum, magnesium, calcium, potassium, sodium hydroxides can cause boron deficiency; long-term lack of nitrogen, phosphorus, potassium and iron can lead to boron deficiency; It can aggravate the lack of boron. The lack of potassium will lead to the poisoning of a small amount of boron. The increase of nitrogen content will increase the amount of boron, which will lead to the lack of boron. Manganese is not good for boron absorption, and plants need appropriate Ca/B and K/B ratios (eg, Ca/B for grape plants is 1234 milliequivalents, K/B is 1142 milliequivalents). And the appropriate Ca/Mg ratio.

 

Boron has a controlling effect on the Ca/Mg and Ca/K ratios.

 

Several elements that form complexes, such as antimony, aluminum, and antimony, temporarily improve boron deficiency.

 

8. Manganese: Calcium, zinc, and iron impede the absorption of manganese, and iron hydroxide can cause manganese to precipitate. Manganese is fixed by applying a physiological alkaline fertilizer. Vanadium can slow the toxicity of manganese.

 

Sulfur and chlorine can increase the release and effective manganese, which is beneficial to the absorption of manganese, which is not conducive to the absorption of manganese.

 

9. Molybdenum: Nitrate nitrogen is beneficial to the absorption of molybdenum, ammonia nitrogen is not conducive to the absorption of molybdenum; sulfate is not conducive to the absorption of molybdenum. A large amount of calcium, aluminum, lead, and iron, copper, and manganese all hinder the absorption of molybdenum. In the state of phosphorus deficiency and sulfur deficiency, molybdenum is inevitably deficient, increasing phosphorus is beneficial to the absorption of molybdenum, and increasing sulfur is unfavorable; when phosphorus is abundant, more molybdenum is required. Therefore, excessive phosphorus sometimes leads to the lack of molybdenum.

 

10. Zinc: The formation of hydroxide, carbonate and phosphate in zinc is unacceptable. Plants require an appropriate P/Zn ratio (typically 100-120, greater than 250 zinc deficiency). Excessive phosphorus can lead to zinc deficiency. When nitrogen is used, it needs more zinc. Sometimes it will lead to zinc deficiency. Nitrate is beneficial to zinc absorption. Chlorine nitrogen is not conducive to zinc absorption. Increased potassium and calcium are not conducive to zinc absorption. The absorption of manganese, copper and zinc is unfavorable. There is mutual absorption between magnesium and zinc. Zinc deficiency leads to less potassium in the roots. The clay with a low Si/Mg ratio in the soil will be deficient in Zn, which antagonizes the absorption of iron.

 

11. Copper: The application of physiological acid chlorine or potassium fertilizer can increase the activity of copper and facilitate absorption. The formation of copper phosphates, carbonates and hydroxides hinders absorption, so it is rich in CO2, carbonic acid and calcium-rich soils, which is not conducive to copper absorption. Phosphorus can cause copper deficiency. The generation of H2S in the anaerobic state of the soil also hinders the absorption of copper. Copper is also antagonized with aluminum, iron, zinc and manganese. Nitrogen is also not conducive to the absorption of copper.

 

V. Poor physical and chemical properties of the soil The physical and chemical properties mentioned here mainly refer to the factors related to nutrient absorption. The growth of normal and vigorous shoots depends on the good development of the root system. The deeper and wider the root distribution, the more nutrients are absorbed and the more nutrients that may be absorbed. The soil is stiff and firm, and the hard disk, bleaching layer and high groundwater level on the bottom layer will limit the extension of the root system, reduce the absorption of nutrients by crops, and aggravate or cause deficiency. High groundwater levels, such as some lowlands, occur more frequently during the rainy season when the groundwater level rises. In calcareous soils, the high groundwater level also increases the amount of bicarbonate ions (H2CO3) in the soil solution and affects iron. Effectiveness, which causes or exacerbates iron deficiency and the like. Unreasonable land leveling

 

The rise of poor soil and poor soil is often the cause of deficiency.

 

The soil cation exchange capacity (CEC) is also related to the deficiency. The sand with small substitution capacity has small nutrient capacity for adsorption, and the nutrient elements with large demand often cannot meet the crop needs. Studies have shown that most soils with CEC <5m·e/100g dry soil cannot maintain sufficient K+ to maintain a "high" potassium supply level, that is, a soil that is prone to potassium deficiency.