There are many causes of crop malnutrition, which are not only affected by the nutritional characteristics of the crop itself, but also affected by the environment such as soil and weather. Diagnosis of malnutrition is through the appearance, soil analysis, plant analysis or other physiological growth indicators to determine the nutritional status of plants objectively to guide the fertilization or improve other management measures. This paper focuses on the diagnosis of crop malnutrition through shape diagnosis and proposes corresponding fertilization strategies (focusing on five nutrient elements: nitrogen, phosphorus, potassium, zinc, and boron).
I. Nitrogen disorders in crops
(I) Symptoms
1, lack of disease. Slow growth of plants, individual dwarfing, branching, tillering less; chlorophyll content decreased, leaf color faded, old leaves yellow and premature aging and easy to fall off; stems and leaves often red or purple; roots are slender, the total root volume decreased; Both the fruit and the fruit are less, and the grain of the fruit is not full, and the ripening is earlier and the yield and quality are reduced. The symptoms of nitrogen deficiency in various crops are not the same. They are described as follows: Nitrogen and nitrogen deficiency in rice and wheat, slow growth of plants, individual dwarfing, and reduced tillering; chlorophyll synthesis blocked, pale leaf color fade, old leaves yellow, premature decline Fall; stems and leaves often with red or purple; roots are slender, the total root volume decreased; spikes differentiation is not complete, small ear. When the nitrogen deficiency is not very severe, the grain-to-straw ratio is improved, but the ripening is earlier, the yield and quality are reduced, and the resistance to disease and lodging are enhanced. The lack of nitrogen in maize causes slow plant growth and dwarf plantlet type; pale leaves fade from the tip of the leaf; the lower leaves show a "V" shape from the tip of the leaf; the middle and lower stems often have a red or purple color; the ear becomes smaller and lacks grain. Severe, mature earlier, yield and quality decline. Nitrogen deficiency in rape, plant growth is slow, stems are weak, and branches are few; leaves are small, leaf color fades; stems and leaves appear red or purple; pods are less and short, yield and quality decline. The potato lacks nitrogen, the stems and leaves become smaller, and the leaf color fades and yellows. Tea tree lacks nitrogen and the leaves are uniformly yellowed from the bottom up. The leaf lacks nitrogen, the leaf color fades, and the lower leaf yellows.
2, excess disease. Excessive nitrogen in the crops reduces the resistance to disease and lodging, and the late grafting of the plants is delayed and the kernels are not full, resulting in reduced yield and quality. Excessive nitrogen in rice plants, nitrogen organic compounds contained in the plant increased sharply, carbohydrates consumed too much, the cells were large and the walls were thin, the water content increased, the growth was too prosperous, and the cause was long; the leaf area was increased and the leaf color was deepened. Yu Yu; Mechanical organization is underdeveloped, easy lodging, susceptible pests and diseases; seed setting rate and 1000-grain weight decreased, the ratio of grain and straw decreased, yield decreased. Excessive corn nitrogen, plant growth is too prosperous, resulting in long spikes; leaf color deep, leaf area is too large, the field is very serious; stem mast hypertrophy is crisp, easy lodging and susceptible to diseases and insect pests; poor fruition, significantly reduced production. Excessive nitrogen in rapeseeds, overgrowth of plants, excessive branching, deeper leaf color, tender and sturdy stalks, and easy lodging; delayed ripening, uneven grain maturity, and reduced oil content.
(b) Prevention
1. Prevention and cure of crop nitrogen deficiency: (1) Fertilize the soil and improve soil nitrogen supply capacity. For newly-cultivated, low-ripening, organic-poor soils and lighter-textured soils, the input of organic fertilizers should be increased and fertility should be cultivated in order to increase the nitrogen and nitrogen supply capacity of the soil and prevent the occurrence of nitrogen deficiency. (2) When a large number of organic fertilizers with a high ratio of carbon to nitrogen are used, such as straw, attention should be paid to the use of available nitrogen fertilizers. (3) When ploughing and soil preparation, apply a certain amount of available nitrogen fertilizer as base fertilizer. (4) For nitrogen deficiency caused by uneven soil fertility, timely nitrogen fertilizer must be applied.
2. Prevention of excess crop nitrogen: (1) According to the nitrogen requirement characteristics of the crops at different growth stages and the characteristics of soil nitrogen supply, timely and appropriate topdressing should be strictly controlled to avoid topdressing nitrogen fertilizer too late. (2) Under the premise of rational rotation, based on the rotation system, determine the appropriate amount of nitrogen. (3) Rational application of phosphorus and potassium fertilizers to maintain the balance of nitrogen, phosphorus and potassium in the plant. For rice, when the nitrogen excess is not very serious, it can be treated by draining the field and applying potassium fertilizer.
Second, crop phosphorus disorders
The direct adverse effects of phosphorus excess on crop growth and development are relatively rare in production. Here we mainly introduce the symptoms and control measures of crop nutrient deficiency.
(I) Symptoms
Phosphorus deficiency in crops generally manifests as: delayed plant growth, short plant type, reduced branching, tillering, dark green and dull leaves, poor grain and fruit development. The rice lacks phosphorus, the plants grow slowly, the individuals are short, the stems and leaves are narrow, the leaves are straight, and the tops of the clusters are flush and clustered. This is the so-called “one column incense†plant type, with little or no tillering; the leaf color is darkened. Dark green, grayish green or grayish blue; leaf tip and leaf margin often with purple, heading, maturity delay, serious reduction in production. Phosphorus deficiency and phosphorus deficiency in maize were most obvious at the seedling stage. Plant growth was slow and thin. The stem base, leaf sheaths and even the entire plant showed purple-red color. When severe, the tips of the leaves showed a dusky color. Pulling the male silk was delayed, the fruiting was poor, and the ear was bent. Bald tip. Phosphorus and phosphorus deficiency in rape can be found in the cotyledon stage. The color of the hypocotyl of the phosphorus-deficient seedlings is dark, and the leaves become smaller and thicker; the birth of the true leaves is delayed, the shape is small upright, the dark green and dull, and the purplish red appears. The petioles and the veins are on the back Particularly obvious; plants are old and stiff; branches and nodes are elevated, the number of branches is reduced; main stems and branches are weak, and flower buds are sharply reduced; leaf speed is obviously slowed down, and the number of leaves per plant is reduced; The number of grains per pod was significantly reduced and the yield was severely reduced; the grain oil content was reduced. The tea tree lacks phosphorus, the leaves are dark green, and the new leaves are slow and small. Sunflowers lack phosphorus, fine stems, weak flowers, and small plates.
(b) Prevention
1, a reasonable application of phosphate fertilizer. (1) Early application, concentrated application of phosphate fertilizer. Most of the crops are sensitive to phosphorus deficiency in the early growth period and the absorbed phosphorus accounts for a large proportion of total phosphorus. Therefore, the phosphate fertilizer must be applied early. At the same time, due to the low mobility of phosphorus in the soil, and the limited space for the distribution of root elements in pre-harvest crops, which is not conducive to the absorption of phosphorus, phosphate fertilizers should be properly applied. Such as roots, acupuncture points, and other facilities. (2) Apply organic fertilizer and carbon. In the acidic soil, organic fertilizers and carbon should be applied to reduce the fixation of phosphorus on the soil, promote microbial activity and phosphorus conversion and release, and increase the availability of phosphorus in soil.
2, field management measures. (1) Strong seedlings transplanted. For seedling transplanted crops, adequate phosphate fertilizers and other fertilizers should be applied to seedbeds, paddies, and nutritious soils, and seedlings and strong seedlings should be planted in due course. Strong seedlings have strong resistance to stress and developed root systems, which are conducive to the absorption of phosphorus in the early growth period. (2) Water management. For places with groundwater seepage, trenches and ditches should be excavated according to local conditions, cold water intrusion should be ruled out, soil temperature and phosphorus availability should be improved, and phosphorus deficiency should be prevented.
Third, crop potassium disorders
The excessive adverse effect of excessive potassium on the growth and development of crops is quite rare in production. Therefore, this is mainly to describe the symptoms and preventive measures of potassium deficiency in common crops.
(I) Symptoms
When the crop is deficient in potassium, the middle and lower leaves, especially the old leaves, tip and leaf margins, are chlorotic and yellow, causing browning or brown spots. When severe, leaf margins scorch and curl. Dwarf plants, poor fruiting, yield and quality decline. Potassium deficiency in rice, browning or scorch of old leaf tip and front leaf margin, brown spots appear at the same time; plant elongation is inhibited and dwarf; leaf color is dark, dark green and dull; roots are weak, many brown roots, aging Premature ageing; heading irregularities, increased valence rate, normal fertilized kernels are not full, yield and quality decline. There are three typical symptoms: red and dry type, flax spots, brown spots. The lack of potassium in corn and the occurrence of potassium deficiency in corn occur in the middle and later stages of reproduction. It is characterized by the yellowing and scorching of the tips and edges of the old and middle old leaves, shortening of the internodes, and the dwarfing of densely packed leaves. The stalks are weak and easy to fold, the mechanical strength is weakened, they are easy to fall down, the ripening period is delayed, the ear development is poor, the grains are less in shape, the grain is not full, and the yield is drastically reduced; the grain starch content is low, and the quality is inferior. When the tobacco lacks potassium, the tip of the leaf is yellowish, and when it is severe, it is scorched and the tobacco leaves are often yellowed and reversed. Tea tree lacks potassium leaf margin or brownish between veins.
(b) Prevention
1. Reasonably apply potassium fertilizer. (1) Determine the application amount of potash. For most crops, the amount of potassium fertilizer (in K2O) per mu is 7-10kg. (2) Choose the appropriate potassium application period. As potassium is more easily lost in soil, the application of potash fertilizer should be combined with basal fertilizer and top dressing. In soils that are severely deficient in potassium, the proportion of chemical potash fertilizer as base fertilizer should be appropriately larger. Since the balance of nitrogen and potassium in plants is closely related to the occurrence of potassium deficiency disease, potassium fertilizer should be topdressed at the peak of nitrogen absorption in crops in order to prevent the imbalance of nitrogen and potassium and promote potassium deficiency. When there are other potassium sources (such as straw returned to earth, organic fertilizers, grass ash, etc.) as base fertilizer, it is appropriate to use chemical potassium fertilizer for topdressing at the middle and late fertility stages. (3) Provide a source of potassium. Make full use of potash resources such as straw, organic fertilizer, and ash, implement straw return, increase organic fertilizer, plant ash, etc., promote potassium recycling and utilization in agricultural ecosystems, ease the contradiction between potash supply and demand, and effectively prevent the occurrence of potassium deficiency disease. .
2, field management measures. (1) Promote winter plowing. On the one hand, winter plowing can reduce or eliminate the harm of reducing substances to crop roots; on the other hand, it can promote the release of potassium in the soil and increase the soil potassium supply. (2) Control the amount of nitrogen fertilizer. The occurrence of potassium deficiency in production is caused to a considerable extent by the excessive application of nitrogen fertilizer. When determining the amount of nitrogen fertilizer in soils with low potassium capacity or potassium deficiency, it is necessary to consider the level of soil potassium, and when the potassium fertilizer is not fully guaranteed, it is necessary to strictly control the amount of nitrogen fertilizer. (3) Moisture management. For rice, it is necessary to combine exposure, storage, and drying in order to eliminate the damage of reducing substances to the root system and inhibit the absorption of potassium. For dryland crops, the combination of open-drainage and application of potash fertilizers is more effective in preventing potassium deficiency.
IV. Zinc deficiency in crops
(I) Symptoms
1, the main symptoms of zinc deficiency. Insufficient zinc will cause physiological diseases. Maize is more sensitive to zinc, and zinc deficiency appears white seedling disease. First, the green leaves of the old leaves are yellowish-white, and gradually develop in the forward section. The mesophyll tissue gradually becomes thin and translucent, and the red leaves of some varieties appear red. In purple, the male silking period of the diseased plant was postponed, and the ear was lack of grain and alopecia. Zinc deficiency occurs in 2-4 weeks after rice is planted. There is rust in the middle part of the basal leaf blade. It develops toward both ends and gradually expands into strips. The leaf extends gradually upwards from the base. The leaf speed is slow, and the tillering is slow and even late. Irrespective of tillers, the plants shrink, the roots become undeveloped, the infertility rate of the flowers increases, and the ripening delays. The young leaves of the fruit tree are hard and small and lack green spots. They gather together and form clusters of leaves, which are called "lobular leaf disease".
2, the symptoms of crop zinc poisoning. The symptoms of zinc poisoning in the crops are yellowing of the leaves and reddish brown spots. Excess zinc also hinders the absorption of iron and manganese and may induce iron deficiency or manganese deficiency.
(b) Prevention
1, the prevention and treatment of crop zinc deficiency. (1) Reasonable leveling of cultivated land. Firstly, the topsoil shall be piled up and the bottom of the earth shall be leveled and then covered with topsoil so as to maintain the effective zinc level of the topsoil and prevent zinc deficiency in dry land crops. (2) Rational fertilization. In the low-zinc soil, the amount of phosphate fertilizer and nitrogen fertilizer should be strictly controlled to avoid the large-scale application of chemical phosphate fertilizers, especially superphosphate; in the phosphorus-deficient soil, phosphorus fertilizer and zinc fertilizer should be used in combination; at the same time, phosphorus fertilizer should also be avoided. Over-concentration to prevent the imbalance of the proportion of local phosphorus and zinc induced zinc deficiency. (3) Add zinc fertilizer. In view of the fact that the main crops will suffer from zinc deficiency during the early period of fertility, it is advisable to use zinc fertilizer as base fertilizer. When zinc sulphate is used as a basal fertilizer, the dosage is usually 1-2 kg/mu; when foliar spraying, 0.15%-0.30% of zinc sulphate is generally used, and the amount of zinc fertilizer is 0.15-0.2kg/mu. - 3 times, interval 5-7 days.
2. Prevention and cure of crop zinc poisoning. (1) Control industrial "three wastes" pollution. (2) Reasonably apply zinc fertilizer to prevent zinc poisoning caused by excessive application of zinc fertilizer. (3) Use zinc organic waste with caution.
V. Crop Boron Insufficiency
(I) Symptoms
This article only describes the symptoms of boron deficiency in crops. The typical symptoms of boron deficiency in crops are the inhibition of root growth, which is stubby and stubborn; the stem tip is dead and the branches are clustered; the leaves are shriveled, the petioles and stems are cracked, and they are brittle, brittle, and hard to break. Symptoms of boron deficiency in different crops vary, and are now described as follows: When boron deficiency occurs in potatoes, growth points are inhibited, internodes are shorter, and plants are dwarfed. Severe growth points stagnate, wither, or even die, resulting in a dry top. After the death of the apical buds, the axillary buds are promoted to germinate and new branches are formed. The apical buds of these new branches also shrink and die due to lack of boron, and the axillary buds on the branches can germinate and grow into new branches. Such growth points Death and the formation of new branches make the plants short. The leaves are not even, thickened, brittle, and easily broken; the leaves darken and the new leaves shrink, curl, and wrinkle. Rapeseed "flowering but not real" is a prominent symptom of boron deficiency in rapeseed. The occurrence of "flowering but not real" rapeseeds showed no abnormal performance in the early period of growth, and even the growth was quite good. The plant leaves were thick and stalks were higher than the people, but the yield per hectare was less than 750 kg, and even the harvest was not achieved. Due to falsehood, prosperous secondary branching and prolonged flowering; when nutrient adequacy is sufficient, it is more prosperous and prosperous. Therefore, it is also called “insanityâ€. The occurrence of a large number of delicate secondary branches causes the plants to be broom-like, and the mature stage presents a dense and disorderly field landscape, which is completely different from the regular and orderly landscape of normal fields. According to the type of the secondary branches and the dwarfing of the main stem, the symptoms of boron deficiency in rapeseed can be divided into three types: leggy, dwarf, and intermediate.
(b) Prevention
1. The prevention and treatment of boron deficiency in crops starts from the following aspects: (1) Application of boron fertilizer. Different crops have different requirements for boron and endurance to high boron. Therefore, the most important thing to pay attention to when applying boron fertilizer is the amount of use, which is less effective and more likely to cause poisoning. (2) Add organic fertilizer. On the one hand, organic fertilizers contain boron, and the total boron content is usually 20-30 mg/kg. After being applied to the soil, it can be released with the decomposition of organic fertilizers to increase the level of boron in the soil; on the other hand, it can also increase soil organic matter and increase the The effective boron storage of the soil reduces the fixation and leaching of boron and coordinates the strength and capacity of boron in the soil. (3) Appropriate application of nitrogen, phosphorus and potassium fertilizers. Controlling the amount of nitrogen fertilizer to prevent the excessive application of nitrogen can cause the deficiency of boron. Appropriate application of phosphorus and potassium fertilizer can promote the growth of crop roots and enhance the absorption of boron by the root system. (4) Other measures. According to the causes of the deficiency of boron, comprehensive prevention and control measures can be adopted by planting suitable crops, reasonably leveling cultivated land, and water management.
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