Citrus Garden Soil Fertilizer Water Management

The high quality and high yield of citrus are closely related to soil conditions. The quality of soil and fertilizer management in citrus orchards not only directly affects the yield of citrus, but also affects the quality of citrus fruits. I. Orchard soil management 1. Basic characteristics of soil (1) Basic concept of soil The soil is a loose surface layer on the earth's land that can produce plant harvests. There is a close relationship between the growth of citrus and soil types and properties. Citrus roots absorb water and nutrients in the soil. With deep soil layer, fertile soil, and good physicochemical properties, the roots are strong and widely distributed within the soil layer, and the aboveground areas grow robustly. Conversely, shallow soil layers, poor soil structure, and thin soil ridges result in shallow root distribution and poor growth. Affects the growth and development of the above ground. Citrus roots and ground parts are interdependent and mutually dependent. Without good soil conditions, there is no developed root system, and there is no quality and high yield of citrus. (2) The role of soil: The soil is composed of minerals, organic matter, moisture, air and soil microorganisms, and its composition changes with the passage of time and changes in environmental conditions. It has the following functions: 1 Support. 2 Supply nutrients and moisture. The soil continuously supplies and coordinates the necessary water, nutrients, air, heat, and other factors necessary for the growth and development of the plant, as well as other living conditions. Soil is the source of water and nutrients in plants. Citrus is a perennial evergreen tree, with a wide distribution of roots. It takes a long time to carry fruit on the tree. It takes a lot of water and nutrients from flowering to fruition. Most of these water and nutrients are taken up through the soil. 3 resistance. With deep soil layers and deep and wide distribution of citrus roots, it is possible to use deeper layers of water and nutrients in the soil to promote the growth of the shoots. The growth of the shoots, on the other hand, promotes the growth and development of the roots, thereby increasing the ability of the citrus to resist drought. At the same time, the deep soil avoids the direct solar radiation, and there is little difference between day and night and seasonal temperature, which can reduce or avoid the harm of the low temperature and high temperature to the root system. In addition, the deep soil and robust trees also enhance the plant's resistance to diseases, while poorly growing fruit trees are susceptible to infection by pathogens. 4 cushioning. The soil is composed of a variety of charged organic and inorganic colloids. It is a huge natural buffer pool and has an adsorption effect on the anions and cations. For example, if there is excessive application of fertilizers, or poisonous substances such as copper preparations and arsenic preparations that are sprayed to prevent pests and weeds, and environmental acid rain and toxic substances emitted from factories, they will cause harm to the soil, but the soil itself has a buffer effect. All the possible consequences of these hazards have a tendency to slow down. 2. Requirements of the growth and development of citrus on the soil environment The growth and development of citrus fruit requires a suitable soil environment, but not all the soil conditions for citrus cultivation can meet the optimum requirements for citrus growth. In general, citrus has a wide adaptability to soil and can grow even in soils with poor physical and chemical properties such as red, yellow and alluvial soils. However, good soil conditions are necessary to obtain high yields and stable yields. (1) Soil depth. Citrus is a perennial evergreen tree with high soil requirements. Generally, the soil depth should be more than 1 meter, and the effective soil layer should be more than 0.6 meters. (2) Soil texture. Soil texture means that the soil is divided into several categories according to the mechanical composition of the soil particles. Sand, loam and clay are commonly referred to as soil texture categories. The quality of soil texture directly affects the permeability of the soil, the effectiveness of water and nutrients, and then affects the growth and development of citrus roots. The growth of citrus roots requires good soil aeration, excessive sanding, or excessive stickiness. Over viscidity results in poor ventilation of the soil and inhibits the respiration of citrus roots; overshadouring of the soil results in poor water retention and fertilizer retention. 1 sandy soil. Sandy soil contains many sand grains, and there are few clay particles. Generally, the inter-particle pores are relatively large. The water is easy to infiltrate into the drain, and the water in the soil evaporates quickly and the water storage capacity is small. Therefore, sand fertilization should emphasize the use of organic fertilizers, supplemented by quick-acting fertilizers, and the principle of well-grounding, diligence, and thin application should be mastered. 2 loamy soil. Loamy soil is an ideal soil for planting citrus and other crops due to its proper proportion of clay and sand, both the advantages of sand and clay, good soil physical properties, strong water retention and fertility, and excellent ploughability. 3 clay soil. Because clay soil contains more clay particles and less sand, there are few gaps between soils, and pores communicate with each other to form a very thin pore network of pores, which has strong water storage and fertility, but it rains or water after irrigation. The vertical penetration is slow, internal drainage is difficult, and susceptible to damage. Muddy soil has poor ventilation, aerobic microbial activity is inhibited, soil organic matter is decomposed slowly, humus is easy to accumulate, and fertilizer effect response is sluggish. Heavy clays are subject to drought and cracking, which can cause the citrus roots to be broken or exposed to the air. Soil improvement should be performed when growing citrus. Sand mixing or applying manure is the main measure to improve the clay. (3) Soil pH. Soil pH refers to the acid-base nature of the soil solution in which the proportion of H+ and OH is different. It is also called the soil reaction. Usually, it is expressed in terms of pH. Citrus has a wide range of soil acidity, and it is in the pH range of 4.5 to 8.5. It can grow, but it is slightly acidic, most suitable for pH 5.5-6.5. In general, the soil is too acidic and the citrus grows poorly. Acidic soils have high concentrations of hydrogen ions and high concentrations of aluminum ions that are harmful to plant growth and development, often resulting in the lack of plant-exchanging salt-based nutrients. Therefore, soil must be modified before planting citrus. The effect of soil pH on plant growth and development is mainly due to the effect of soil fertility properties, such as affecting the effectiveness of nutrient elements. (4) Soil organic matter. Soil organic matter includes: moving and plant residues that enter the soil, microbiological organisms, and applied organic fertilizers (such as human waste, manure, compost, and grass pond mud). The level of soil organic matter is one of the important indicators of soil fertility. Soil sand can improve its ability to retain water and fertility and prevent the loss of nutrients. For heavy clay, it can increase its porosity and reduce the physiological obstacles caused by roots in an over-wet state. The application of organic fertilizer and green manure in citrus is the most fundamental measure to increase soil organic matter content. The granule structure formed by the combination of organic matter and soil particles can improve the physicochemical properties of the soil and improve the water, fertilizer, gas and heat conditions required for the growth of citrus roots. The organic matter has the characteristics of buffering and adsorption, and can absorb part of inorganic salt nutrients. Preventing the loss of nutrients and increasing the utilization of nutrients can also reduce the toxic effects of excessive fertilizers and toxic substances on citrus. The content of soil organic matter in the citrus orchards of China is generally low, below 2%, while the high-yielding citrus orchard requires at least 2% of soil organic matter, preferably 3% to 5%, total nitrogen (N) 0.1% to 0.2%, total phosphorus ( P2O5) 0.15% -0.2% and total potassium (K2O) 2% or more are beneficial to citrus growth and results. (5) Groundwater level. The groundwater level in the citrus orchard should be less than 1.0 m above the ground surface in the range of citrus root activity. If the groundwater level is too high, the deep trenches should be used for drainage. If the groundwater level is too low, the drought resistance of citrus is not good. It is best to do drought irrigation, heavy rain does not accumulate water, and maintain relative soil moisture content at about 80%. (6) Soil aeration. The process of root absorption of nutrients is an energy-consuming process, and the energy comes from the root's respiration. Therefore, the obstruction of the root's respiration will inevitably affect the absorption of nutrients by the root system. Poor soil ventilation has obvious adverse effects on the growth, development, quality and quality of citrus. (7) Soil nutrients. Soil is the storage of plant nutrients, and the content of soil nutrients has great influence on the growth and development of citrus. The source of soil nutrients, in addition to the inorganic nutrients released by its weathering and decomposition, mainly comes from the organic and inorganic fertilizers applied to the soil. Trace elements are more dependent on the content of the soil itself. 3. Soil Management Most of the citrus production areas in China are located in the red, yellow and yellow soils (including purple soil) in the low hilly areas. The soil layers are shallow, with low organic matter content and low fertility. Some of them have poor physical properties and are far from satisfying the normal growth and development of citrus. Nutrient needs. The management of citrus orchard soil is to carry out the ripening and improvement of the soil according to the characteristics of the orangery, increase soil fertility, and create water, fertilizer, gas and heat conditions that are conducive to the growth and development of citrus. The most effective way to ripen and improve the soil is to increase soil organic matter content and reasonable farming. (1) Deep-turning and improving soil. The deep-turning of soil and mature soil is the main content of orchard soil management, and is the central link of the measures for increasing production. It is the most fundamental measure for citrus fruit trees to form strong roots and obtain high yields and stable yields. Deeply change the role of soil. The main role of deep turning and soil improvement is to loosen the soil and improve soil structure, performance and soil water, fertilizer, gas and heat conditions. Combining deep-buried organic fertilizer with embedding will not only increase soil organic matter content and soil porosity, but also increase soil moisture and nutrient content. The period and method of deep-turning the soil. The period of deep turning and soil reform is closely related to the effect. The period of deep turning around should be based on local specific conditions such as soil quality, period of root growth activity, and topography. In general, shallow ploughing can be carried out every year, deep ploughing is done once every few years; time is better from September to October each year and after fruit picking. The principle of deep-turning and soil reform is: It can neither affect the normal growth of citrus, but also can promote the healing of wounds that cut roots and wounds. (2) Weeding and weeding. Most of the citrus producing areas in China are located in the warm, humid and rainy regions of the tropical and subtropical regions. Orchards are prone to weeds and consume nutrients and moisture in the soil. At the same time, weeds are a potential breeding ground for diseases and insect pests. As a result, there is no cover or intercropping in the citrus orchards. Every year, three to four times of cultivating and weeding are generally performed. Cultivated weeding is a soil management method that maintains the soil surface of the Orangery. Timely cultivating and weeding can both prevent weeds and citrus from competing for nutrients and water, promote soil aeration, accelerate the decomposition of organic matter, and eliminate places where pests and diseases can breed. Through cultivating and weeding, loosening the soil, destroying the capillary action of the soil, cutting off the channels for rising water, reducing the evaporation of water, increasing the ability of the soil to retain fertilizer and water, improving the ventilation conditions of the soil, promoting the activity of soil microorganisms, and accelerating the organic and inorganic nutrition of the soil. The decomposition, transformation, improve the effectiveness of soil nutrients. However, due to the exposed surface of the soil, the loss of topsoil, loss of soil nutrients, and the granule structure are vulnerable to destruction. Over time, it will cause various kinds of deficiency diseases, resulting in decline of tree vigor and physiological obstacles. (3) grass cultivation. The cultivation of the grass in the citrus groves can not only cover the surface of the Orangery, but also solve Caotan, reduce the use of labor, keep the topsoil from the scour of heavy rain, and prevent the loss of soil. After the grass withered, turning it into the soil can increase soil organic matter content, improve the soil's nutritional status and physical properties, and promote citrus growth. (4) Coverage. The use of castrated green manure stems, leaves, straw, hay, manure, and other materials to cover around fruit trees has been widely used by many countries in the world. Citrus gardens in the south of China are mostly located in hilly areas. The soil layer is shallow and the capacity of keeping fertilizers is poor. Especially in summer and autumn, the temperatures are high and the evaporation is large, which often leads to water shortage in citrus. If it does not rain for consecutive days or dozens of days. However, the situation is even more severe. In summer and autumn, it is precisely the period during which the citrus fruit is inflated. The demand for water is very urgent. If it is not timely covered and drought-resistant, it will affect the yield and quality of citrus. Coverage has a significant effect on the daily and seasonal changes in soil temperature due to the isolation of the sun from the ground and its conservation. Coverage can reduce the maximum surface temperature at noon under dry heat conditions, but it has little effect on the minimum temperature; in winter, coverage increases the effect, which can reduce the damage of frost on fruit trees. According to the research, covering in the summer can reduce the surface temperature 6-15 °C, winter increase in ground temperature 1-3 °C, thus reducing the soil season and temperature difference between day and night, the upper and lower soil temperature. The overturning of the cover into human soil can fertilize the soil, improve soil strength, and improve soil structure, which has a similar effect to the embedding of green manure. Usually, in the case of overturning fabrics with more fibers (such as crop straw, grass, etc.), nitrogen fertilizer must be applied to reduce the carbon-nitrogen ratio. 4. Soil Improvement The central problem of soil improvement is the problem of ripening the soil and maintaining and improving soil fertility. (1) Acid Soil The main measures for soil improvement in acidic orange orchard are as follows: First, lime is used. Application of lime can increase soil pH and reduce acidity. It also eliminates the adverse effects of aluminum ions on the growth of citrus. The application of lime can be combined with improved soil fertility. The second is to strengthen the soil and water conservation work. Acidic soils are mostly distributed in southern China. Due to the low latitude, high rainfall, hot and humid climate, strong weathering of soil, rapid release and transformation of nutrients, strong leaching, lack of organic matter in soil, poor colloidal performance, nutrients. Loss is serious. Therefore, in order to improve the acidic soil, we must fundamentally solve the problem and combine the governance of mountains, water, and afforestation, and pay close attention to soil and water conservation. The third is to bury organic fertilizer. Decomposition of organic matter under the influence of soil microorganisms plays a major role in soil fertility. The main component of organic matter is humus, which includes high molecular compounds such as humic acid. Under the influence of low temperature and dryness, humic acid is converted into insoluble matter and soil particles are bound together, or a rubber film is coated with soil particles, cement particles dispersed, forming a good structure of the group. The fourth is the cultivation of green manure. Improve physical and chemical properties of soil and increase soil organic matter content. The fifth is the application of alkaline fertilizers. The long-term application of alkaline fertilizers, such as calcium, magnesium and phosphate fertilizers, in acidic soils can not only regulate the pH of the soil, but also increase the phosphorus nutrition in the soil. Second, the citrus garden fertilization 1, the nutritional characteristics of citrus 1 citrus annual number of shoots, results, long fruiting period, the demand for fertilizer. Citrus are plucked, flowered, and fruited almost throughout the year and require a certain amount of nutrients from the soil. In general, citrus should be pumped 3-4 times a year, resulting in many fruits, fruit drop, long fruiting period, usually about 5 months, it consumes a lot of nutrients. If these nutritive substances are consumed without timely supplementation, the soil fertility will be degraded. 2 Citrus roots absorb nutrients and require certain ground temperature conditions. Citrus grows under subtropical conditions and has a relatively dormant period. Roots need nutrients to absorb certain nutrients. 3 Citrus is more sensitive to nutrient deficient and nutritional disorders. Citrus is a deep-rooted crop, which grows in the same soil for several decades. The root system selectively absorbs certain nutrient elements from the soil for a long period of time, which can easily cause the deficiency of these elements. 4 tree storage a lot of nutrition. Citrus is a perennial woody plant, and there is a lot of nutrients in the tree. According to the observation of the isotope 15N tracer on Satsuma mandarin, it was found that about 28% of the total nitrogen contained in the new leaves of spring shoots was from the remaining nutrients in the previous year's autumn fertilizer; 30% come from the nutrient stored in the leaves of the previous year. Therefore, the actual nutrient status of the tree, in addition to the nutrient absorbed from the soil in the year, is related to the level of nutrients stored in the tree to a large extent. Five roots rely on symbiotic seedling root fungi to absorb nutrients. Citrus roots generally have no root hairs, and rely on symbiotic mycorrhizal fungi to absorb water and inorganic nutrients, while also absorbing auxin and vitamins secreted by mycorrhizal fungi. 6 Unbalanced nutrition prone to size years. Citrus nutrient requirements are balanced, nutritional imbalances, easy to produce size years. 7 The nutritional requirements of citrus vary with variety, growth period, age, and rootstock. Taking varieties as an example, in general, oranges need fertilizers for navel oranges> oranges> banana oranges> oranges> Wenzhou oranges. 2, the principle of fertilization The general principles of citrus fertilization are: the combination of organic fertilizer and inorganic fertilizer; delayed fertilizer combined with the application of quick-acting fertilizer; nitrogen fertilizer combined with phosphorus, potassium fertilizer and trace element fertilizer application; exploration and shallow application and Root spray combined. Among them, organic fertilizer and slow-acting fertilizer are the main applications, supplemented by inorganic fertilizers and quick-acting fertilizers; organic fertilizers and delayed-effect fertilizers are mainly deep-seated fertilizers, and inorganic fertilizers and quick-acting fertilizers are mainly applied shallowly and externally. 1 See tree fertilization. According to different varieties of citrus characteristics, rootstock characteristics, different phenological period, age, tree vigor and the results of the state to take appropriate fertilizer measures. 2 see soil fertilization. According to soil traits, such as soil structure, texture, the level of groundwater level, organic matter content, pH, soil maturity, nutrient levels and terrain, topography, etc. determine the correct fertilizer application. For example, sandy soils have poor water retention and fertility, and fertilization can be performed by using methods such as diligence, thin application, shallow application, and extra-root dressing; clay can be appropriately re-applied, deep application, and deep-light combination. 3 see climate fertilization. Temperature, humidity, and rain directly affect the respiration of citrus roots and their ability to absorb nutrients, as well as the decomposition, transformation, and microbial activity of soil nutrients. Therefore, it is necessary to look at climate fertilization, early rain and sunny fertilization, dry season in the rainy season, liquid application in the dry season, drought and flood relief after the use of quick-acting fertilizers or outside the roots of forced fertilization.” 4 economical fertilization.. Economic fertilization is to obtain the lowest fertilizer input One of the most economical methods of fertilization The economical fertilization of orchards must first identify the main barriers to increased fertilization and take necessary measures, such as severe iron deficiency symptoms in iron orchards, other fertilization measures on the fruit When the improvement of yield and quality is not of great benefit, the symptoms of iron deficiency must be corrected, and the effect of other fertilizers can be revealed.Ferric is the main obstacle factor at this time. Find out the obstacles of fertilization and reasonably match other fertilizer varieties. In addition, timely supplementation of deficiencies may often yield a multiplier effect.5 In conjunction with other measures for increasing production, the high quality and high yield of citrus is based on comprehensive agricultural technological measures, and therefore, reasonable fertilization must be combined with other measures. The combination of comprehensive measures such as farming, irrigation, pruning, pest control, etc. can achieve better results. Effect 3. Citrus fertilization period and amount of fertilizer Citrus have different growth and development characteristics at different biological ages, and the demand for nutrients varies. As the age of trees increases, the yield of fruits increases, and the demand of citrus for fertilizers increases. Year by year, the period of application is also different from that of infancy, therefore, according to different citrus varieties and ages, a reasonable period of application and application amount should be determined.Usually, the demand and absorption of nutrients by citrus during a year is in accordance with the growing season. In the case of changes, the nutrient absorption during the spring sprouting period is less and the absorption intensity is weaker; with the growth of the root system, the shoot extraction and flowering of the shoot, the absorption of nutrients by the citrus gradually increases and reaches the peak; Absorption gradually decreased (1) Fertilizer application period: From late February to early March, the amount of fertilizers accounts for 40% of the whole year, combined with the application of organic fertilizers, and 2 maintenance of fruit fertilizers: from mid-April to late May, The amount of fertilizer used accounts for 15% of the annual total, and the multi-flowering trees and the debilitating trees are applied when the buds are white or when the first physiological fruit is dropped;3 The fixed fruit fertilizer: in early July, the amount of fertilizer accounts for 15% of the whole year; Strong fruit fertilizer: From early August to late September, fertilization accounts for 10% of the whole year;5Fetching fruit fertilizer: Fertilizer amount accounts for 20% of the whole year within 7-10 days before harvest. The total amount of fertilizer per acre (active ingredient) is 70-80 kilograms, of which the amount of organic fertilizer accounts for more than 40% N:P:K=1:0.6:0.8 4. The method and method of fertilizing in citrus grove The fertilization in citrus grove The methods and methods are closely related to the fertilizer effect, and improper fertilization methods and methods not only waste the fertilizer, but also injure the fruit trees in severe cases, causing the quality of the fruit to deteriorate and the yield to decrease. Therefore, attention must be paid to it. (1) Fertilization methods a. To avoid excessive damage to the citrus roots, dig around the canopy drip line about 4-6 meters in diameter, about 0.5 meters deep in the fertilization point 4-6, the fertilizer applied in the hole, each year to open the hole position should be staggered to facilitate the growth of citrus. After planting soil, it should be mixed with the soil evenly b. Rectangle furrows, Qi Shuguan drip line, open four symmetrical rectangular ditches 1.0-1.5 meters long, 0.6 meters wide and 0.5 meters deep, and put the fertilizer into the ditch. This method has a large contact surface between the fertilizer and the soil due to the flat bottom, and is easily absorbed by the root system. The position of the ditch should be rotated every year. C. Application. In the rainy season, according to the specific circumstances, such as citrus need to supplement nitrogen and potassium fertilizer, the fertilizer can be spread under the canopy. Fertilizer should be spread as evenly as possible and used to dig into the soil. d. Root dressing. When it is found that a certain nutrient element is insufficient and must be corrected, extra-root fertilizer is an effective remedy. Outside the roots of forced fat quick effect, the amount of province, is commonly used in adult citrus orchards. (2) Fertilization methods Citrus orchard fertilization methods can be divided into two categories: one is soil fertilization, where plant roots directly absorb the applied fertilizer from the soil, and the other is extra-root fertilizer, with foliar spray and branch injection. And so on. The most commonly used in production are soil application and foliar spray. 1 Soil fertilization. The extraction of manure from soil solutions by citrus is mainly carried out in the form of ion exchange by powerful fine roots and fibrous root groups. Therefore, soil fertigation should be adapted to the distribution characteristics of the root system. Citrus's root mass distribution is generally wider than the crown, but the denser distribution is in the inner and outer bands of the crown projection, which is generally symmetrical to the crown, and forms a broad conical root system with the downwardly growing root system. Therefore, the depth of fertilization should be determined according to the depth of the distribution of the root-dense layer, and the fertilization position should be in the vertical soil layer around the crown. With the deepening of the soil, the depth of fertilization should be gradually deepened; as the crown expands year by year, the fertilizing position should be gradually shifted outwards. Fertilizing points should not be played in the same direction and position each time, and rotation and position should be repeated one by one. Because the roots are fertile, the depth and breadth of fertilization can induce root growth. Usually, the location of citrus fertilization should be slightly deeper or a little bit farther than the location where the root system is concentrated, in order to induce deep and broad root development, expand the absorption range of nutrients, and enhance the stress resistance of the tree. 2 top dressing. Extra-root fertilizer, also known as foliar spray fertilizer, is a kind of liquid top-dressing method that uses the features of stomata, cuticle, new shoot skin, and young fruit to directly absorb nutrients. The top-dressing fertilizer has the advantages of quick effect, strong pertinence, saving of fertilizer, and in some cases can solve problems that cannot be solved by soil fertilization, and enables the leaves to rapidly absorb various nutrients, preserve fruits, and regulate the tree vigor. It plays a significant role in improving the quality of fruit, correcting the symptoms of deficiency, and improving the cold resistance of winter trees. The nutrients for top dressing are mainly through the stomata and stratum corneum of the leaves and then transported to the various organs in the tree body. Generally, they are absorbed by the leaves after 15 minutes to 2 hours after spraying. However, the intensity and speed of absorption are related to leaf age, nutrient composition, and solution concentration. The young leaves have a strong physiological function, and the area occupied by stomata is larger than that of the old leaves, so the absorption is faster and the absorption rate is higher. There are more stomata in the leaf surface than in the leaf surface, and there are loose sponge tissues under the epidermis of the leaf blade. The cell space is large and numerous, which is conducive to the penetration and absorption of nutrients. Therefore, the back of leaves is absorbed faster than the leaf surface, and the absorption rate is also high. When spraying the leaf surface fertilizer, the back of the leaves must be sprayed uniformly to facilitate the absorption of the leaves. 3 irrigation fertilization. Fertigation is a method of fertilizing fertilizer in irrigation water and then fertilizing it through an irrigation system. In recent years, extensive research has been conducted at home and abroad, and there are also reports of practical applications. Its main advantage is that it saves water, fertilizer and labor; the utilization rate of fertilizer is high; the distribution of nutrients for irrigation and fertilization is uniform, and the roots and leaves are not damaged, which is beneficial to the maintenance of soil structure. This method is widely used in water-deficient areas and is suitable for adult orchards and dense planting gardens where the canopy is handed over. According to research, compared with surface irrigation, drip fertigation can save 44% to 57% of nitrogen fertilizer, and spray irrigation can save 11% to 29%. Although there are many advantages in irrigation and fertilization, the problems of pipelines and dripping plugs are prone to occur in practical applications. To reach the practical application stage, further research is needed. III. Water Management in Citrus Orchards 1. Effect of Water on the Growth and Development of Citrus 1. Effect on the growth of citrus. The ability of citrus to pump a certain number of robust shoots is extremely relevant to the adequacy of water supply. When the water is lacking, the time for drawing the shoots is greatly delayed, the branches are thin, the leaves are small, the number of leaves is small, and the shoots are uneven; the excess water can lead to excessive shoot growth and affect reproductive growth. . 2 Effects on flowering and fruit growth. When the citrus lacks water during the flowering period, the flowering branch quality is poor, the flowering is irregular, the flowering period is prolonged, and even a large number of flowering buds are caused. In case of abnormal high temperature, more serious losses are caused. The relationship between fruit and water is more closely related. When water is severely deficient, it causes fruit and fruit to compete for water, which causes the water in the fruit to flow backward to the leaf with stronger growth, hindering the growth and development of the fruit, increasing the number of small fruits and decreasing the yield. Poor quality. If you encounter too much autumn rain after a long time, you will have cracks, and it will also produce floating fruit. In many places in summer and early autumn, due to high temperatures and strong sunshine, water shortages often lead to fruit “sunburn” and “hard umbilical” phenomena, with saplings being the most serious. Excessive moisture in the flowering period of citrus affects the pollination and insemination, and it is easy to drop flowers and fruit. 3 Effects on root growth. Citrus roots should not be stained by wetness. Keeping the soil moist is an important condition to cultivate a strong root system. The main external factors affecting water uptake in citrus roots are: soil moisture content, soil temperature, soil permeability, and the concentration of ten soil solutions. The water content in the soil is low, and the water absorbed by the citrus roots naturally decreases. However, the citrus branches and leaves still transpire the water at this time. If the time is longer, the plants will suffer from lack of water and temporary wilting. If no water is added in time, It may cause permanent wilting of the plant, causing death of the plant in severe conditions; adequate soil moisture content, high temperature, low air humidity, and strong evaporation. The rate of water absorption by the roots cannot keep up with the speed of the evapotranspiration of the leaves, resulting in wilting of plants. However, by the evening, the temperature dropped, the air humidity increased, and the transpiration of the plants weakened. The citrus could be restored without irrigation. Soil temperature affects the absorption of water by roots. Generally, in the range of 10 to 30°C, the root water absorption capacity gradually increases with the increase of soil temperature. The soil temperature is higher than 30°C or lower than 10°C, and the root water absorption capacity is obvious. reduce. The quality of soil permeability depends on the content of oxygen and carbon dioxide, high carbon dioxide content, lack of oxygen, and impeded root respiration, affecting citrus water absorption. If the concentration of the soil solution is too high and exceeds the concentration of the root cell fluid, the water absorption in the root system will be seriously affected, and even the reverse osmosis of root cell water will occur, resulting in physiological water shortage of the plant. 2. Reasonable irrigation The rational irrigation of citrus groves is based on the characteristics of citrus water requirements for scientific water use, not only to meet the different requirements of citrus palates on moisture, but also to use the least water to obtain the highest economic benefits. (1) Irrigation period and the determination of irrigation volume 1 Irrigation period. Whether oranges need to be irrigated cannot be judged merely by surface phenomena. It is often too late to determine irrigation only from the wilting phenomenon such as leaf curling and yellowing. Because when the plant has wilting surface symptoms, the soil has been excessively dry, which has caused serious damage to the growth and development of citrus, and this effect is often irreversible. At present, there are mainly the following methods to determine the citrus irrigation period: a. To determine the transpiration of the leaves: A certain amount of citrus leaves are wrapped with plastic sheets and the transpiration of the leaves is determined. Measured once every 1-2 days, when the leaf transpiration is reduced to 2/3 of the full water supply, it indicates that irrigation is needed. When using this method, there must be multiple observations in the same orchard due to the differences between plant individuals. b. Determination of Soil Moisture: The determination of soil moisture generally uses oven drying. That is, select representative soils from the citrus orchards to take samples, and the soil can be taken in layers (0-20, 21-40, 41-60 cm), and then the soil samples can be quickly packed into the aluminum covered in layers. In the box, mark it well, put it in the oven together with the weight of the aluminum box, dry it for 4-8 hours at 105C, take it out after cooling and weigh it, then put it in the oven and bake it for 2-3 hours, and bake it twice before and after Constant weight can be. Then calculate the soil moisture content according to the formula. Soil Moisture Content; Wet Soil Weighing - After Weighing x100% After Drying To measure the soil moisture content, determine whether irrigation is required according to Table 7-15. Table 7-15 Water standard for irrigation and drainage of soil (%) Soil texture requires irrigation. Drainage sandy soil soil and clay soil 40 >42 >45 2 Irrigation volume. The appropriate amount of irrigation should make the soil moisture in the citrus root distribution layer most conducive to the growth and development of citrus in one irrigation, which is equivalent to 60% to 80% of the maximum water holding capacity of the soil in the field. If we only infiltrate the soil distributed in the surface layer or the upper root system, it will not only fail to achieve irrigation purposes, and due to multiple supplemental irrigation, it will easily cause soil compaction and destroy the soil structure. Therefore, it must be thoroughly penetrated. However, in drought-fighting irrigation, especially after long drought, water should not be irrigated once, otherwise it will cause a lot of cracks, or a lot of late autumn shoots, causing undue losses. Determining the amount of citrus irrigation is a good method is to measure the soil moisture content, then the amount of irrigation can be calculated according to the following formula: The soil moisture content must be measured before each irrigation, soil bulk density, field water holding capacity, roots Depth is usually measured once a year. The irrigation volume measured according to the above formula is theoretically the lowest quantity. In practical application, it should also be properly modified according to the age, soil, species, phenological period, etc. to meet the actual situation. (2) Irrigation methods Irrigation methods and irrigation time, irrigation volume are three inseparable factors, such as improper methods, can not get good irrigation effect, and even produce harm. Therefore, the irrigation method is an important part of improving irrigation efficiency. With the advancement of science and technology, irrigation methods have been continuously improved, and modern irrigation techniques with water saving, efficiency enhancement, and labor saving as the main contents have become an important symbol of orchard irrigation. 1 furrow irrigation. Also called dip irrigation, that is to say, the digging wells in the Citrus Garden are connected with the water conveyance channels. The irrigation ditches are slightly lower and the irrigation water is penetrated by the ditches and the ditches. This method is relatively uniform in infiltration and is suitable for orchards with adequate water sources in Pingba or Hill Terraces. There are two types of furrow irrigation, one of which is to open a ring ditch under the canopy waterline, and to open a large ditch between the rows of fruit trees. The water flows from the major furrow into the ring ditch and dives into the ditch. The table ditch can also use the back ditch. water. Another method is to open the ditch between the rows and open the ditch to transfer water around the orchard. Divert water into the ditch and gradually submerge the subsoil. Fill soil and loose soil immediately after filling. 2 watering. In areas where there are insufficient water sources or young orange groves and sporadic planting areas, man-made water or powered diversion canals can be used. In general, the town opens a ring-shaped groove, a pit, or a trench in the ground below the crown. This method is labor- and time-consuming, in order to improve the anti-early effect, the best combination of fertilization, add 4-5 tablespoons of human waste in each of the water, after the irrigation line cover. This method is simple and easy to use and is currently widely used in production. 3. Water-saving irrigation Surface irrigation, which has been widely used in citrus production areas in China, can only change the soil moisture, has little impact on the microclimate in the field, and has a large irrigation quota, which is inconvenient for the implementation of suitable irrigation, and waste of water is also great. Surface irrigation in mountain orchards results in low uniformity of irrigation and large loss of fertilizers and water; adverse effects such as salt reversion will also be brought about by tidal flats. With the development of citrus production and improvement of irrigation technology, China's citrus production areas are experimenting and gradually promoting sprinkler irrigation, drip irrigation, and irrigation technology. This is an important measure to realize the modernization of orchard management. (1) Sprinkler irrigation. Sprinkler irrigation is water spray irrigation. It uses mechanical equipment such as pumps, piping systems, and sprinklers to spray water into small droplets under certain pressure to irrigate orchards like rain. As early as the twentieth century, Germany and Italy had begun to use sprinkler irrigation in large quantities, and the United States began to apply sprinkler irrigation in hillside orchards in California. With the development and improvement of high-efficiency nozzles, thin-walled aluminum tubes, lightweight plastic tubes and quick connector technology, sprinkler irrigation has been widely used in orchards and field crops. In recent years, citrus groves in China have gradually tried out and promoted sprinkler irrigation technology, and wells have achieved very good results. The advantages and disadvantages of sprinkler irrigation: The reason why sprinkler irrigation can be widely applied at home and abroad is that the main reason is that compared with surface irrigation methods, sprinkler irrigation has many outstanding advantages, which can be roughly summarized as the following five aspects: 1 Increase production. Sprinkler irrigation can use less irrigation quota for shallow pouring ground irrigation, which is convenient to strictly control soil moisture, maintain fertility, and do not damage the soil aggregate structure. It can also promote the development of shallow root systems and is conducive to the full use of soil surface fertilizer. Moreover, the sprinkler irrigation can regulate the microclimate of the Orangery, increase the surface air humidity in the near-surface, and cool down in the hot summer. It can also wash away the dust on the branches and leaves, which is beneficial to the respiration and photosynthesis of the plants and increase the yield. In general, spray irrigation increases production by 10% to 30% compared with surface irrigation. Wells can improve fruit quality. Reports have shown that the yield of sprayed irrigation in sweet oranges in California is 60% higher than that in furrow irrigation. Spraying in the early dry season in Guinea can make lemons, sweet oranges and grapefruit mature in advance. 2 Save water. Due to population growth, environmental pollution and the need for modernization, the demand for fresh water is increasing day by day.而我国柑橘园多建立在丘陵山地，交通不便，不少果园缺少水源，因此，节约灌溉用水，提高灌水利用率已成为柑橘生产中必须重视的问题。由于喷灌便于控制灌水量，基本上可以不产生深层渗漏和地面径流，灌水均匀度可以达到80％--90％。因此，灌水的有效利用系数高，一般为60％～85％，节水30％-50％，在透水性强、保水能力差的沙质土壤节水甚至可达70％以上。在干早缺水和海拔高的灌区，这一点显得特别重要。 ③节省劳力。由于喷灌的机械化程度高，可大大减轻劳动强度，节约大量劳动力。即使使用小型移动式喷灌机组也可以提高工效20一30倍：如大面积采用固定式喷灌系统，尤其159 是采用门动化操作的固定式喷灌系统则工效会更高。此外，由于减少了修造田间工程(水渠、畦沟、田埂等)，以及利用喷灌设施施肥和喷洒农药，还可节省更多的劳动力。 ①节约用地，由于节约厂灌溉渠道用地.可以更充分地利用耕地，一般可增加耕地面积7％-10％。此外.喷灌对土地平整度要求不高，尤其适用于山地果园以及不适宜采用地面灌溉的沙地果园采用。 ①保持水土、防止返盐。喷灌能根据土壤质地的轻重和透水性大小，合理确定灌溉强度和水滴大小这样就可以不破坏；土壤的团粒结构，避免土壤冲刷，使水分都渗入到土层内，防止水土的流失。在有可能产生次生盐碱化的海涂柑橘园，采用喷灌控制湿润深度，可消除深层渗漏，防止地下水位上升和土壤返盐。但是喷灌也有它的缺点和局限性。首先是受风的影响较大。一般在3—4级以上的大风时水滴在空中就被吹散，灌溉均匀度大大降低。其次是空气的相对湿度过低时，水滴在空中的蒸发损失大，可达10％。因此，常采用夜间喷灌的方法来减少空中蒸发。第三是一般情况下土壤表面湿润程度较重，深层湿润不足。可采用“低强度喷灌”使喷头的喷灌强度低于土壤的入渗速度，并延长喷灌时间，使水分能充分渗入下层而又不会产生积水和表面径流，第四是投资较高，由于喷灌需要动力设备，故初期投资较高。据埃及统计，喷灌的费用较地面灌溉高25％；美国的试验认为，喷灌的运转费用较高，包括燃料、电费和机器折旧费等。 (2)滴灌。滴灌又称滴水灌溉.是近年发展起来的一种比较先进的灌溉技术，是将有一定压力的水，通过—系列管道和特制毛管滴头，把水一滴一滴地渗入果树根系范围的土层，使土壤保持柑橘生长最适的湿润状态。滴灌缺点： ①节约用水、在滴灌条件下，直接由蒸发损失的水量是最小的。 .因为水滴不在空气中运动，不打湿叶面，也没有湿润面积以外的土壤表面蒸发。另外，由于滴灌可以防止杂草的生长，也就防止了杂草对水的无益消耗。设计和管理得当的滴灌系统不产生地面径流，并且能够灌溉整个地块直到地边，但却不湿润种植面积以外的地方。由于易于掌握精确的施水深度，用水很省。柑橘园采用滴灌时，水的利用率可高达80％--95％，而喷灌、漫灌对水分的利用率分别只有65％ --85％，40％～60％。 ②增加产量。以色列在—般灌水方法不能有效使用的粗质土壤及盐碱灌溉水条件下进行滴灌和沟灌、喷灌的对比试验，结果显示，滴灌可使作物产量大为提高；即使在一般灌水方法有效而成功的地区，应用滴灌也比一般灌水方法有较高的产量，增产幅度在10％--20％。由于滴灌是缓慢、匀速、低流量进行的。不破坏土壤结构，可以保持土壤有良好的通透条件；通过滴灌施肥，可以为植物提供充足的养分，并且使土壤水分始终稳定处于低张力状态.便于肥水的吸收利用；滴灌避免浸湿枝叶，土壤表面的湿润也最小，可以减少许多病虫害的发生，同时通过滴灌系统，还可以提高施洒农药的效果。在于早地区的果园采用滴灌.可以减少杂草的滋牛；海涂柑橘园采用滴灌，町以防止上壤返盐等。 ③适用地域广。滴灌适于山区、沙荒、碱地采用。这些地区采用一般灌溉方法往往效果很不理想。滴灌适用地域很广，不需要平整土地和渠道，水和绝大部分肥料以及农药可以通过完全封闭的条件从水源直接输送到作物根部。滴灌时水分不向深层渗漏(可以控制)，因此，土壤底层的盐分或含盐的地下水不会卜升并累积到地表，所以不会产生次生盐碱地： 即使水中含盐分高些，因盐分处于稀释状态，不影响植物的正常生长发育。滴灌对水源缺乏，而且容易渗漏、蒸发作用强烈的沙地果园意义重大。对地形起伏不平的山区果园，也能正常灌溉。滴灌较之喷灌具有几个明显的优点：一是不受风速的限制，可以一天24小时供水；二是大多数滴灌系统具备持久性；三是果园灌溉间距宽，滴灌系统的成本较具同样自动化装置的固定装置或常设喷灌系统的成本低；四是滴灌系统的工作压力比喷灌低得多，运行成本也较低：五是滴灌系统不妨碍任何其他的农事活动，灌水的同时，可以进行喷药除虫、收获、剪枝等项活动；六是滴灌施肥用量少，效率高。 ④滴灌系统存在的主要问题。 —是管道和滴头的堵塞问题。二是滴灌限制根系的发育；因为淌灌一般仅湿润根部区域，作物根部的发展常限制在滴头附近湿润区，根系发育浅，一旦供水出现故障，缺水造成的损失更大，因此在设计滴灌系统时，必须认真考虑水分的分布区域。滴灌造成土壤盐分的累积。因为所有灌溉水都含有一定的溶解盐，当作物吸收水分时，大部分的盐分没有被吸收，这些盐分在整个灌溉季节内通常被推向湿润上体的边缘。施水量比作物耗水量较多时，大多数的盐分可以被推向或淋洗到根区以下。沿着湿润表层的边缘盐的积聚最多，雨水把这部分盐冲向根区，容易损伤作物。为了尽量减少这一危害，滴灌系统应在多雨期运行，使盐分向下移动，雨水淋洗不足的地方，有时需要补充喷灌或地面灌溉，以防止盐分积累到危险程度。滴灌系统的安装费用较移动式喷灌和地面灌溉系统要高，这是限制滴灌大量应用的最主要的原因。 (3)渗灌：渗灌是近年来发展起来的一种新型旱地灌溉工程技术，是把多孔管道埋于柑橘根系，在管道内通过低压水流，通过小孔向土壤渗入水分进行灌溉。渗灌比喷灌节约用水15％，比沟灌节约用水35％。

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