The element was originally contained in the soil, but for various reasons the plant could not absorb it.

The details are as follows.

I. Drought: When there is no water, the element cannot become soluble or ionic state, and the roots cannot absorb it, so the deficiency is mostly found in dry years or dry seasons.

Second, soil reaction (ph) discomfort: soil reaction strongly affects the solubility of nutrients, that is, the effectiveness. Some elements are easily soluble under acidic conditions, with high effectiveness and validity, and the solubility - effectiveness decreases when the reaction tends to be neutral or alkaline. Other elements are the opposite, with high effectiveness under alkaline conditions and low effectiveness under acidic conditions. Particularly closely related to the reaction are trace elements. For example, iron, boron, zinc and copper increase significantly in solubility and rapidly in effectiveness as pH decreases (before pH 4.5), and decrease in effectiveness as pH approaches neutral or tends to be alkaline, while molybdenum, in contrast, increases in effectiveness as pH increases. Bulk elements are generally slow to respond to pH, but phosphorus is the exception, the appropriate pH range of phosphorus is extremely narrow, strictly speaking, only at pH 6.5 or so, <6.5 and soil iron, aluminum, etc. combined and fixed, the lower the pH, the greater the solubility of iron, aluminum, the greater the amount of fixed, >6.5 is combined with calcium in the soil fixed, effectiveness is also reduced. However, the solubility of calcium phosphate is greater than that of iron and aluminum phosphate, so the effectiveness of phosphorus in alkaline soils is usually higher than that of acidic soils.

The optimum pH for nitrogen is 6 to 8.

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

The optimum pH for potassium is 6 to 7.5.

The optimum pH of sulfur is to be above 6 toward 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 below 6.5 in the direction of acid.

The optimum pH of boron is 5 to 7.

The optimum pH of manganese is 5 to 6.5

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

The optimum pH of molybdenum should be above 6 in the direction of alkali.

Third, adsorption and fixation: that is, nutrient elements are fixed by inorganic or organic matter adsorption, and can not be absorbed by the root system. The adsorption and fixation of each element is closely related to the soil or soil-forming matrix.

Table 16 Soil-forming matrix and soil sorption and fixation of elements

Parent material, soil Element fixed

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

Alkaline soils, sodic soils Ca Mg Fe B Zn Cu

Lime soils P Mn B Cu

Soils with much organic matter Mn Zn Cu

Granite, gneiss-developed soils Zn Mo

Soils developed from loess parent material (clay particles of montmorillonite) B Ca Cu

Rice soils Zn

Vermiculite, Chilean stone K B

Acidic soils with iron nodules Mo

IV. Incompatibility between elements

1. Nitrogen; it is more difficult to absorb nitrate nitrogen than ammonia nitrogen; the application of excessive potassium and phosphorus both affect the absorption of nitrogen; boron deficiency is not conducive to the absorption of nitrogen.

2. phosphorus: increase zinc can reduce the absorption of phosphorus; more nitrogen is not conducive to the absorption of phosphorus; iron also has an antagonistic effect on the absorption of phosphorus; increased application of lime can make phosphorus become unavailable; magnesium can promote the absorption of phosphorus.

3. potassium: increase boron to promote the absorption of potassium, zinc can reduce the absorption of potassium; more nitrogen is not conducive to the absorption of potassium; calcium, magnesium has an antagonistic effect on the absorption of potassium.

4. calcium: potassium affects the absorption of calcium, reduce the level of calcium nutrition; magnesium affects the transport of calcium, magnesium and boron and calcium have antagonistic effects; ammonium salts can reduce the absorption of calcium, reduce the transfer of calcium to the fruit; application of sodium, sulfur can also reduce the absorption of calcium; increase the soil aluminum, manganese, nitrogen, will also reduce the absorption of calcium.

5. magnesium; more potassium affects the absorption of magnesium, more sodium and phosphorus is not conducive to the absorption of magnesium, more nitrogen can cause magnesium deficiency. Magnesium and calcium, potassium, ammonium, hydrogen have antagonistic effect, increase the application of sulfate class can cause magnesium deficiency. Magnesium can eliminate the toxic effects of calcium. Magnesium deficiency can induce zinc deficiency and manganese deficiency. Magnesium and zinc have a mutually reinforcing effect.

6. Iron: more boron affects the absorption of iron and reduce the content of iron in the plant body, nitrate nitrogen affects the absorption of iron, vanadium and iron have antagonistic effects, causing iron deficiency of more elements, their order is Ni>Cu>Co>Gr>Zn>Mo>Mn

Potassium deficiency can cause iron deficiency; a large amount of nitrogen, phosphorus and calcium can cause iron deficiency.

7. boron: iron and aluminum oxides can cause boron deficiency; aluminum, magnesium, calcium, potassium, sodium hydroxide can cause boron deficiency; long-term lack of nitrogen, phosphorus, potassium and iron can lead to boron deficiency; increased potassium can aggravate the lack of boron, potassium deficiency can lead to a small amount of boron poisoning; the increase in the amount of nitrogen, the amount of boron required also increased, can lead to boron deficiency. Manganese is detrimental to boron uptake and plants require appropriate Ca/B and K/B ratios (e.g., 1234 mg equivalent Ca/B and 1142 mg equivalent K/B for healthy grape plants). and appropriate Ca/Mg ratios.

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

Several elements that can form complexes, such as strontium, aluminum and germanium have a temporary improvement of boron deficiency.

8. Manganese: Calcium, zinc and iron hinder the absorption of manganese, and the hydroxide of iron can make manganese precipitate. The application of physiological alkaline fertilizer makes manganese fixed. Vanadium can slow down the poisoning of manganese.

Sulfur and chlorine can increase the release state and effective state of manganese, which is beneficial to the absorption of manganese, and copper is unfavorable to the absorption of manganese.

9. Molybdenum: nitrate nitrogen is good for molybdenum absorption, ammonia nitrogen is not good for molybdenum absorption; sulfate is not good for molybdenum absorption. Calcium, aluminum, lead, iron, copper, and manganese all hinder the absorption of molybdenum. In a state of phosphorus and sulfur deficiency, there is bound to be a lack of molybdenum. Increasing phosphorus is beneficial to the absorption of molybdenum, while increasing sulfur is unfavorable; more phosphorus requires more molybdenum, therefore, too much phosphorus sometimes leads to a lack of molybdenum.

10. Zn: make Zn form hydroxide, carbonate and phosphate then into the ungivable state. Plants require an appropriate P/Zn ratio (generally 100 to 120, greater than 250 is zinc deficiency). Excessive phosphorus can lead to zinc deficiency, while more nitrogen requires more zinc, which sometimes also leads to zinc deficiency, and nitrate nitrogen is good for zinc absorption, while chloride nitrogen is not good for zinc absorption. Increased potassium and calcium are detrimental to zinc absorption. Manganese, copper and relative zinc absorption are unfavorable. There is mutual assistance between magnesium and zinc absorption. Zinc deficiency leads to less potassium in the root system. Soil with low Si/Mg ratio of clay grains will be deficient in Zn, and zinc antagonizes the absorption of iron.

11. Copper: Application of physiological acidic chlorine or potassium fertilizer etc. can improve the activity of copper and facilitate uptake. The phosphates, carbonates and hydroxides that generate copper hinder absorption, so soils rich in CO2, carbonic acid and calcium are not conducive to copper absorption. More phosphorus can lead to copper deficiency. Soil suspicious gas state to produce H2S also hinders the absorption of copper. Copper is also antagonistic to aluminum, iron, zinc and manganese elements. Nitrogen is also detrimental to the absorption of copper.

Fifth, the poor physical and chemical properties of the soil physical and chemical properties referred to here mainly refers to factors related to nutrient absorption. Normal and vigorous above-ground growth depends on the good development of the root system, the deeper and wider the distribution of the root system, the greater the number of nutrients absorbed, and the more types of nutrients may be absorbed. Stiff and solid soils, bottom layers with hardpan, bleaching layer, high water table, etc. will limit the extension of the root system, reduce the crop's nutrient uptake, and aggravate or trigger deficiency disease. High water table such as some lowlands, during the rainy season when the water table rises crop potassium deficiency occurs more often, while in calcareous soils, high water table also makes the bicarbonate ion (H2CO3) in the soil solution increase and affect the effectiveness of iron, thus triggering or exacerbating iron deficiency, etc. Unreasonable land formation makes the soil

The rise of poor nutrient-poor subsoil is also often a cause of deficiency.

Soil cation substitution (CEC) is also related to deficiency, and sandy soils with small substitution are often unable to meet the needs of crops because of the small capacity of nutrient adsorption and storage. It has been noted that most soils with CEC <5m-e/100g dry soil do not maintain sufficient K+ to maintain a "high" level of potassium supply, i.e. they are soils prone to potassium deficiency.