Contents of nutritional diagnosis of fruit trees
Including the content and balance of inorganic nutrients in various organs of different fruit trees and their effects on growth and development. Select organs and periods that are sensitive to the reaction and analyze them to determine the indicators of excess, suitability, deficiency or potential deficiency. Soil diagnosis is to study the content, availability, complementarity or antagonism of elements in soil. In practical application, it is to carry out chemical analysis on representative plant organs and soil samples, compare profit and loss indicators and analyze plant growth conditions, and then point out the demand of plants for various elements, formulate reasonable fertilization measures, and understand the fertilization reaction and the role of different inorganic elements.
Characteristics of nutritional diagnosis of fruit trees
Fruit trees are perennial crops, and their nutritional characteristics are as follows: ① Storage nutrition. Therefore, its nutritional status is not only related to the nutrients absorbed from the soil in that year, but also depends to a great extent on the storage nutritional level of trees. ② Fruit trees are more sensitive to the profit and loss of various nutrient elements, as well as the interaction and antagonism between nutrient elements than ordinary crops. After fruit trees are planted, they can only selectively absorb some nutrients from the limited soil for many years, which is easy to cause the lack of some elements. Therefore, fruit trees are prone to element deficiency disease. (3) Fruit trees are individual crops with deep roots, and their roots are widely distributed in the soil, but unevenly, so it is difficult to obtain representative rhizosphere soil samples. Moreover, different types or layers of soil have different properties, different soil colloids have different absorption abilities for various ions, and the ion antagonism, ion diffusion and root absorption abilities in soil are also different, which all affect the absorption of nutrients by trees. Based on the above reasons, fruit tree nutrition diagnosis should be given priority to, supplemented by soil diagnosis.
Tree nutrition diagnosis
According to the following steps:
Diagnostic organ selection
Selection principle ① is sensitive to nutritional status; ② It can effectively reflect the differences in yield, quality and growth status; ③ Its nutrients are relatively stable in a certain season; ④ The sample only involves a very small part of the whole plant, and the normal vegetative growth of the whole plant will not be affected after sampling. Most fruit trees, with mature leaves on the spring shoots, are ideal analytical organs. Leaf is not only an organ of photosynthesis, but also the concentration of elements in leaf is closely related to growth potential and yield. But grapes should use petioles; The fine roots of persimmon and xylem of lemon are the most sensitive to phosphorus reaction, and the pulp should be used for boron determination of plum. When analyzing trace elements in sweet orange, it is more accurate to use fine roots than leaves.
The basic principle of leaf analysis is the "minimum nutrition law" of Justus J.yon Libig. That is, when the concentration of an element is too low, it becomes a limiting factor for the growth of fruit trees. Only by supplying this element can we have a certain effect. The more serious the deficit, the greater the correction effect after supply. 1936, Mocy put forward the "critical percentage of nutrient elements" based on the dry matter of leaves, that is, every nutrient element of a certain crop has a fixed "critical percentage", which indicates that the plant is in luxury absorption; Below this figure, it means lack of nutrition. Actually this is a range value. When it approaches or falls below this value, the plant has been damaged, but its appearance is not displayed. This "potential deficit" is most easily overlooked. From the "potential deficit" to the luxurious absorption room, it is the best nutritional range of this tree species. If fertilization is excessive, the content of this nutrient element in the tree is too high, which is called "luxury absorption". On the contrary, it will cause poison and affect growth and yield. In the nutritional diagnosis of fruit trees, we should not only pay attention to the absolute concentration of each element, but also pay attention to the appropriate proportion of various nutrient elements in the tree (see nutrient element balance).
sampling method
See table for sampling period, position and method of leaves of main tree species. Attention should be paid to sampling: ① trees that are compared with each other must be sampled from trees with relatively similar varieties, age, tree potential, growth and site conditions; (2) Don't bring leaves damaged by pests and diseases; ③ Taking leaf samples under normal ecological conditions and abnormal ecological conditions; (4) immediately fill in the field number, sample number, sample name, sampling date, place, location and the health status of the tree; ⑤ Put fresh leaves into nylon sandbags and immediately send them back to the laboratory for cleaning. If they can't be treated immediately, put them in plastic bags, seal them, put them in the refrigerator and temporarily store them at -5℃.
Sampling method for leaf analysis of main tree species
The cleaning and drying of leaves are carried out according to the following procedures: ① Immediately put fresh leaves into water containing 0. 1% detergent for cleaning (about 30 seconds); ② Wash off the detergent with tap water; ③ Rinse with deionized water for 3 times; (4) put it on filter paper to absorb excess water; ⑤ Put it into a paper box and dry it in a blast oven at 70℃; ⑥ Fine grinding with agate mortar and sieving with 20 ~ 40 mesh sieve. If pesticide (such as Bordeaux mixture) is sprayed on the leaves, it should be washed with 0. 1N hydrochloric acid before washing, but it should not exceed half a minute, otherwise other elements will be dissolved and washed away. However, if the leaves are sprayed with Bordeaux solution, that is, washed with 0. 1N hydrochloric acid, it is difficult to clean copper, and other elements such as zinc and iron are sometimes polluted.
Analysis
Kjeldahl method for determination of total nitrogen; Total phosphorus is treated by wet ash method and then reduced by vanadium molybdenum yellow or ascorbic acid; Boron is colored by dry ash method, and then by curcumin colorimetry. Magnesium, zinc, iron, manganese and copper are all prepared by wet ash method and determined by atomic absorption spectrophotometry. Potassium and calcium can be determined by flame photometer or atomic absorption spectrometry. In the determination, the standard solution should be prepared with pure metal or other kinds of elements. For the testing of common instruments, it is best to use advanced automatic instruments, such as atomic absorption spectrophotometer, inductively coupled plasma spectrophotometer (ICP), X-ray diffractometer, emission spectrometer and plasma generator.
Tree diagnosis index
Because of the inconsistent fertilization system, the standards adopted by various countries are not completely consistent. China has always attached importance to nitrogen fertilizer in production, but the application amount of phosphorus fertilizer is low. Therefore, compared with other countries, the adaptation range of apples and pears in China is slightly higher in nitrogen and slightly lower in phosphorus.
Soil nutrition diagnosis
The role of soil nutrition diagnosis
To understand the soil nutrition status of newly planted orchards or nurseries, and provide basis for formulating soil management and fertilization measures in orchards. For mature orchards, it can reflect the supply status of various nutrient elements, thus confirming the results of tree nutrition diagnosis. It can also predict the limiting factors that may reappear after adjusting the imbalance of tree nutrition. According to these, it can be judged whether a certain element deficiency is due to the lack of this nutrient element in the soil, or whether the absorption, transportation and distribution of this element by trees are not harmonious.
Diagnostic method of soil nutrition
The content of available nutrients in soil is taken as the diagnostic standard. Includes the following steps: oxidizing soil organic matter with potassium dichromate; Hydrolyze nitrogen by alkaline potassium permanganate method (acid soil can be hydrolyzed by acid); Nitrate nitrogen is treated by phenol disulfonic acid method; Ammonia nitrogen is distilled by magnesium oxide; Olsen method was used for available phosphorus; Treatment of exchangeable calcium and magnesium in soil (suitable for neutral and acidic soil) by neutral ammonium ester method; Determination of available potassium by neutral ammonium acetate method; Extraction of available boron from soil by stagnant water and curcumin colorimetry. Effective iron, manganese, zinc and copper were extracted by DTPA and determined by atomic absorption spectrophotometry. Extracting the total salt content with water, evaporating and weighing; Extract the pH value with water, or directly use the suspension, the ratio of soil to water is 1: 1 ~ 1: 5, and measure the potential with a pH meter after equilibrium.
In 1980s, the research on fruit tree nutrition found that the same element was unevenly distributed in different organs of the same plant. For example, the calcium content in apple leaves is moderate, but it is obviously insufficient in fruit. Fruit tree cultivation aims at obtaining high-quality commercial fruits, with lush foliage, which may lead to insufficient fruits. Therefore, the nutritional diagnosis of leaves should be supplemented by the nutritional diagnosis of fruits. In order to more accurately judge whether the fruit has element deficiency, which affects the quality and storability.