In 1923 K. Warington discovered that boron is an essential element of plants. The content of boron in the crop is generally two-tenths, three to one-hundredth of the dry weight. Among them, leguminous and cruciferous content are the highest, while gramineous crops are low. Among the various organs, boron has the highest content of flowers and leaves, followed by stems, roots and fruits, and the least amount in seeds . Boron is not a component of various organic matter in crops, but it can enhance some important physiological functions of crops. The supply of boron is sufficient, the plants are flourishing, the seeds are full, the roots are good, and the harvest is guaranteed. Conversely, the supply of boron is insufficient, the plant growth is poor, the quality and yield of the products are declining; when the boron is seriously deficient, even the particles are not collected . (This is the effect of boron on most crops written in the book)
Let me talk about the prejudice against boron.
1. Boron fertilizer only works on rapeseed
Since the promotion and application of boron fertilizer started on rapeseed, but it was used less on other crops, and for a long time, many farmers and even agricultural technicians had such a misunderstanding. Boron fertilizer only played a role in rapeseed. In fact, boron fertilizer has an effect on the yield of almost all crops, especially for the reproductive growth of crops. In recent years, according to the results of domestic soil station tests, the effect of boron fertilizer on the yield of rapeseed, cotton, peanuts, grapes, fruits, chestnuts, vegetables, legumes and other crops is very significant .
2. Boron fertilizer mainly adopts basic application method
The boron fertilizer that was introduced and promoted in agricultural production earlier was industrial borax, and borax could not be sprayed with leaves. Therefore, farmers planted rapeseed when they were planted. In fact, the application of boron fertilizer in combination with soil application and foliar application is the best. Because boron fertilizer mainly plays a role in the reproductive growth of crops, that is, it plays a role in the late growth of crops. Generally, the spraying time should be before the flowering period. On the one hand, the spraying of the leaves can make the boron fertilizer absorb quickly, and the growth of the crops The health period works. However, the application of boron fertilizer in the soil, such as: the production of boron in the Borax Group of the United States, can not only fundamentally change the boron deficiency in the soil, but also the full supply of boron from the beginning.
3. The ideal variety of boron fertilizer is borax
Borax is a poorly soluble chemical that must be slowly dissolved in warm water at 40 ° C and is difficult to absorb and utilize by crops.
4. Boron and magnesium fertilizer can replace boron fertilizer
Since 1999, some fertilizer dealers in the market have been eager to make high profits, and they have taken the unreasonable means of selling dog meat, which is to replace the borax with boron and magnesium fertilizer produced in the northeast. The main component of the boron-magnesium fertilizer is magnesium sulfate, and less than 0.6% of the boron is only a by-product of the production of magnesium sulfate, so the boron-magnesium fertilizer cannot supplement the boron deficiency of the crop.
5. Boron is not as important as N, K, P fertilizer
Boron fertilizer promotes the reproductive growth of crops with strong specificity, and the importance is the same as N, K and P fertilizers. Today, with the increase of nitrogen, phosphorus and potassium application, boron has become an indispensable important nutrient factor for crop yield increase and transformation.
6. Apply boron fertilizer to increase cost
Boron is a necessary condition for high quality and high yield of many economic, fruit and vegetable crops. On boron-deficient soils, the application of boron fertilizer can increase the income equivalent to 5-15 times of the input cost.
7. Apply once, not for many years
Crops take a large amount of boron from the soil every year; soil factors such as soil drought, soil acidity and alkalinity, soil over-sand or over-staining all determine the need to periodically add boron to plants or soil.
8. Multi-element foliar fertilizer is better than single element boron fertilizer
Crops do not have equal demand for seven trace elements. In addition to trace elements such as boron and zinc, other trace elements are generally available from the soil. Boron is the most important trace element, and most economic, fruit, and vegetable crops require a large amount of it. Therefore, the boron supplementation for boron-deficient crops is better than that of multi-element fertilizers.
Boron not only promotes flowering and fruiting
1. Cell elongation and tissue differentiation
There is a significant interaction between auxin (indole acetic acid) and boron, which inhibits indoleacetate oxidase activity in the roots. Under the stimulation of indoleacetic acid, the root elongation is normal. Indoleacetic acid is formed only in vascular plants in green plants, and it is involved in the differentiation of xylem vessels. Therefore, the general demand for boron is also limited to vascular plants. The woody part of the boron-deficient plant is weakened, and the cell division of the stem-forming layer is strengthened, forming a layer of cell proliferation.
2. Enzyme metabolism and wood formation
The accumulation of phenolic compounds inhibits the activity of indoleacetate oxidase. Boron can complex with phenolic compounds to overcome the inhibitory effect of phenolic compounds on indoleacetate oxidase. Boron inhibits the activity of hydroxylase phenolic enzymes during lignin formation and xylem duct differentiation.
3. Carbohydrate transport and protein metabolism
Boron plays a two-fold role in carbohydrate metabolism: the formation of cell wall material and sugar transport. Boron promotes the circulation of glucose-1-phosphate and the conversion of sugar. Boron and calcium work together as an "intercellular gel". Boron affects the synthesis of RNA, especially uracil. The new leaf protein content of boron-deficient plants is low, which is limited to the cytoplasm, while the chloroplast protein content is not affected, so it is not common for boron-deficient plants to lose green. Boron enhances photosynthesis of crops and promotes the formation of carbohydrates. When the crop is insufficient in boron, it will cause a large accumulation of carbohydrates such as sugar and starch in the leaves, which cannot be transported to seeds and other parts, thereby affecting crop yield.
4. Root growth and development
Boron promotes the normal development of vascular bundles in the roots of legumes, and promotes the sufficient supply of carbohydrates by rhizobium, thereby enhancing the nitrogen fixation capacity of legumes, increasing the protein content, increasing the fiber content of the hemp crops, and improving it. Quality.
Boron can form a complex with 6-phosphogluconate in crops, making 4-phosphatidic acid unable to form (an important raw material for the formation of acid compounds). When the crop is deficient in boron, organic acids accumulate in the roots. Cell differentiation and elongation of the sharp meristem are inhibited, and cork is formed, causing root necrosis. Boron can make the apical and stem growth points of the crop grow normally. Boron forms alcohol with alcohols, sugars and other compounds to improve the supply of oxygen to crop roots. Especially in the absence of oxygen, the application of boron fertilizer can promote the development of crop roots. Therefore, the application of boron fertilizer is better in roots and tuber crops such as beets, potatoes and radishes.
5. Crop stress resistance
Boron can enhance the drought resistance and disease resistance of crops. Boron has the function of controlling water in crops, which can improve the viscosity of the protoplasts of sunflowers, buckwheat and other crops, and enhance the ability of colloids to bind water. The application of boron can promote the formation of vitamin C, and the increase of vitamin C can increase the stress resistance of the crop. Insufficient boron supply to crops, weakened resistance to disease and disease resistance, will cause certain physiological diseases in crops, such as "heart rot" of sugar beet, "brown rot" of broccoli, radish, "scarring disease" of potatoes, Celery's "cracking", "stalk disease", radish hollow, cabbage, spinach growth, sweet potato "brown spot", flax "blight disease", sunflower "white rot" and "grey" Mildew, "charcoal spot disease" of kidney beans. The application of boron can greatly reduce the incidence of these diseases in these crops.
6. Crop early maturing
Boron can promote early maturity of crops. According to relevant domestic data, under the influence of boron, winter wheat will be shortened by eight days by spring time. Boron is applied to cotton, the flower is increased before frost, and the seed cotton yield and fiber quality are improved. The application of boron in corn and rice advances the main growth stages, and the seeds mature about five days earlier. This kind of boron promotes early maturity, which is particularly eye-catching, and it is cold in the mountains and both ripe. The development of agricultural production in the three-cooked areas has certain positive significance. Boron in rape can reduce protein and increase fat content. Boron and cucumber can increase the vitamin C content. Boron application of apples and citrus can increase the sugar content and reduce the acid content. The application of boron fertilizer in hybrid seed production can make the maturity of the reproductive organs of the parent and female plants tend to be consistent, which will promote the substantial increase of seed production, and at the same time increase the seed setting rate of distant hybridization.
7. Pollen germination and pollen tube growth
The indirect action of boron may be related to an increase in the sugar content of the nectar and a change in its composition, making the flowers of the insect vector plant more attractive to insects. The direct action of boron is closely related to the pollen production ability of anthers and the viability of pollen grains. Boron can stimulate pollen germination, especially pollen tube elongation. Boron can promote the normal development of crop reproductive organs, which is conducive to flowering and fruiting. Applying boron fertilizer properly can accelerate the development of flower organs, increase the amount of pollen, promote the germination of pollen grains and the growth of pollen tubes.
Chen Jiaxuan et al. studied the cause of 'flowers and impure' caused by boron deficiency in rapeseed. The results showed that the male and female gametophytes with boron deficiency and normal flowering, but could not be normal, were well developed and the ovary structure was complete, but due to lack of The boron column head loses the ability to attach pollen, the anther wall is destroyed and loses the ability to disperse, the pollen is bonded into a block and the development rate is low, so that the rape can only bloom and not be strong. This result strongly supports the importance of boron for reproductive organ growth. In agricultural production, rapeseed has the symptoms of “flowers and not realâ€, the “innocent disease†of wheat, the “bud without flower†of cotton, the “fruit and not the kernel†of peanuts, and the falling and falling of fruit trees. It is due to the lack of boron.
Summarize the role of boron: it can complex with phenolic compounds, overcome the inhibition of phenolic compounds on indoleacetate oxidase, promote the normal growth of roots and xylem vascular bundles, which is conducive to nutrient transport and promote the accumulation of photosynthesis products in fruits. , to achieve the role of sugar. As the organic nutrients in the plants increase, the concentration of cell fluid increases, which is beneficial to the buds entering the flower bud differentiation. Applying boron fertilizer before flowering can also improve the quality of the flower and stigma, which is beneficial to pollination and increase the fruit set rate of citrus.
Boron-deficient tomatoes
What causes boron deficiency?
Boron is present in the earth's crust, most igneous rocks and soil, and its content is low. In general sedimentary rocks, shale contains the most boron and is mainly found in clay minerals. The boron absorbed by plants mainly comes from the soil, and the boron content of the soil is very important for plants. The amount of boron in the soil is closely related to the parent material, soil type and climatic conditions.
Boron in soil can be simply divided into full boron and effective boron. The total amount of boron in the soil refers to the total amount of boron present in the soil, including boron that can be utilized by plants and boron that cannot be utilized. The amount of total boron in the soil is determined by the amount of boron in the boron-containing minerals. Soil available boron refers to boron that plants can absorb from the soil. Soil-effective boron is present in the soil solution in addition to water-soluble boron. It also includes boron adsorbed by organic and inorganic colloids, because these adsorbed boron is generally leached by water. , but the time of leaching is longer and B. Therefore, soil-effective boron mainly refers to water-soluble boron. The insoluble mineral boron in the soil can release effective boron after slow differentiation, and the effective boron can also be converted into boron which is difficult to use by plants under certain conditions.
Four forms of insoluble boron 4 in the soil exist:
(1) present in clay minerals;
(2) adsorbed on the surface of clay minerals and hydrated iron aluminum oxide;
(3) combined with organic matter;
(4) The free boric acid (H3BO3) and the hydrated borate ion [B(OH)4-] are present in the soil solution.
There are many factors affecting the availability of boron in soil. The main points are summarized as follows:
Soil pH (pH)
The pH value of soil is between 4.7 and 6.7, boron is the most effective, and water-soluble boron is positively correlated with PH value. However, between pH 7.1 and 8.1, the effectiveness of boron is reduced, and water-soluble boron is negatively correlated with pH. It has been proved that the effectiveness of boron in soil is mainly affected by adsorption fixation, and adsorption fixation is closely related to the pH value of soil. Boron is the most effective in acidic soil, but it is easy to elute, and a large amount of lime and boron are applied. Increased adsorption fixation will induce boron deficiency. High-demand boron crops The optimum soil growth environment is pH 6.5. Therefore, lime treatment of soil may be required. However, in general, lime treatment of soil reduces the availability of boron, especially when the pH is greater than 7. The reason is that Ca2+ ions deactivate boron ions.
2. Soil organic matter
Most of the soil can be used in the soil organic matter complex (boron and humic acid), and the soil with more organic matter has more boron. Because of the boron combined with the mechanism or fixed by the organic matter, the organic matter is decomposed and released into the soil solution. Environmental conditions are cold and humid; heat and drying reduce the degradation rate of organic matter and reduce the amount of available boron in the soil. In addition, the soil contains less organic matter and the soil itself is less likely to supply boron. Therefore, it is necessary to frequently apply boron to the soil at a lower concentration.
3. Climatic conditions
The fixed effect in arid areas is enhanced, and the higher the temperature, the lower the water-soluble boron content, which reduces the effectiveness of the soil. In humid and rainy areas, boron is often lost due to strong leaching, reducing the effective boron content, especially in light soils.
4. Soil texture
Boron is easily leached in light soil, which reduces water-soluble boron. In clay soil, due to the adsorption of clay, more effective boron is maintained. Therefore, under other conditions, light soil The effective boron content is less than that of clay soil, and boron deficiency often occurs in light soil. However, although the amount of total boron contained in the clay is relatively high, boron may be used because the surface of the clay is fixed with boron. Sandy soils with good water seepage and large rainfall or often irrigated have strong leakage potential, making them most prone to boron deficiency, so they need to be supplemented with boron frequently.
5. Soil cultivation
Generally speaking, when the soil surface is cultivated, there will be more boron in the soil for plant roots. Soil tillage will mix soil, improve soil aeration and drainage. These are the best conditions for the decomposition of soil organic matter to release boron. As the crop production habits change to less or no tillage management, the organic matter accumulated on or near the soil does not decompose rapidly, so the available boron in the soil depends more on the soil surface moisture conditions. Therefore, boron fertilizer application is very important for crop production.
Summary: The amount of boron in the soil is second, the key is how much boron can be used to determine whether or not to apply boron fertilizer.
The first major cause of boron deficiency in the soil is the low boron content, which leads to the lack of available boron in the soil, and the crops exhibit boron deficiency symptoms, such as the development of granites in southern China and other acidic igneous rocks.
Another reason is that the soil formation process changes the content and distribution of trace elements. For example, the soil boron content of loess development is not low, but the effective boron content is low, which also shows that the soil can not meet the crop needs, and the symptoms of deficiency appear.
The third reason is that the soil acidity is not suitable, and the daughter's fixation causes the soil to be deficient in boron.
The fourth reason is that the climate is dry and humid, resulting in boron deficiency in the soil.
The fifth reason is that excessive application of nitrogen fertilizer and potassium fertilizer will aggravate sudden boron deficiency, because nitrogen and potassium fertilizers have antagonistic effects on boron.
In addition, the soil texture is too thick or lacks organic matter resulting in boron deficiency. In summary, there are two reasons for the lack of internal and external factors in soil boron deficiency. Suddenly, the excessive boron content is the internal cause of boron deficiency, and the soil and climatic conditions are external factors.
Those soils are prone to boron deficiency?
(1) Soils with low total boron content. For example, soils developed by acidic igneous rocks.
(2) Calcareous soils, especially those containing much free calcium carbonate.
(3) Leaching strong acidic soil.
(4) Soil with a lighter texture. Such as sand, wind and sand.
(5) Soils with low organic matter or little application of organic fertilizers.
(6) The use of lime in acidic soils can lead to boron deficiency over time.
(7) Acidic saprolite, mudstone soil and other organic soils, marsh soil.
(8) Excessive soil application of nitrogen and potassium fertilizers.
Boron deficiency in soil in China
China's boron-deficient soil can be divided into the following types:
The first type of boron-deficient soil is low in total boron or water-soluble boron. It is often a serious boron-deficient soil distributed in the south and southeast of China, namely Guangdong, Fujian, southwestern Jiangxi, western Zhejiang and southern China. Including granite and other acidic igneous rocks, gneiss, sandstone and other soil-forming parent materials, such as brick red soil, red soil, yellow soil and so on.
The second type of boron-deficient soil is various soils developed by the alluvial deposits of the loess and the Yellow River, such as loess, bauxite, and yellow fluvo-aquic soil. The total boron content of the loess parent material is medium, and the boron contained in it is mainly found in tourmaline, which is not easy to be weathered and released. The water-soluble boron content in the soil developed from loess is therefore low. A similar situation exists in various soils developed by the Yellow River alluvial deposits. The Yellow River passes through the Loess Plateau and carries a large amount of alluvial deposits to the downstream. The North China Plain is formed by siltation of the Yellow River alluvial deposits. Therefore, this type of boron-deficient soil is mainly distributed in the Loess Plateau and the North China Plain.
The third type is meadow soil and slurry soil with a large amount of organic matter and poor drainage. It is also a boron-deficient soil distributed in the eastern and central parts of Heilongjiang and eastern Inner Mongolia. In addition, gneiss is widely distributed in the north and south of the Dabai Mountains, such as the northeastern part of Hubei and the southeastern part of Henan. The soil formed is often boron.
Internationally divided soil boron deficiency standard
<0.250ppm is very low for boron deficiency symptoms that are visible in severe boron-deficient crops
0.25~0.50ppm low for boron deficiency, boron-sensitive crops may respond to boron
0.50~1.00ppm medium application of boron can increase production between 5-10%
1.00~2.00ppm high general boron fertilizer can be used
>2.00ppm Very high boron fertilizer does not have to be applied
(Public welfare plant protection)
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