Currently, the lack of trace elements in crops is becoming increasingly common, and the supplementation of trace elements in soil is receiving more and more attention from farmers. So what are the functions of trace element fertilizers? What is the application amount of trace element fertilizers? Let's take a look below.
Why do crops need to be supplemented with trace element fertilizers
There are 16 essential nutrients for crop growth, among which carbon (C) comes from carbon dioxide (CO2) in the air; Hydrogen (H) and oxygen (O) come from atmospheric precipitation; Nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), iron (Fe), and chlorine (Cl) all have certain storage capacity in soil, which can provide for the growth and development needs of crops. Among them, nitrogen (N), phosphorus (P), and potassium (K) are commonly referred to as the "three elements" of crop nutrition, or macroelements; Boron (B), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), iron (Fe), and chlorine (Cl) are elements that crops require in small quantities and are called trace elements; Calcium (Ca), magnesium (Mg), and sulfur (S) elements require intermediate amounts, known as moderate elements.
The role of trace elements
（1） Improve crop yields
Medium and low yield fields account for more than 70% of the total cultivated land area, while some high-yield fields have limited yield due to long-term excessive use of constant element fertilizers such as N, P, and K, resulting in soil deterioration. Targeted application of micro fertilizers is an effective technical measure to improve the yield of medium and low yield fields, and is also an important means to maintain continuous yield increase in high-yield fields.
Applying micro fertilizers to different crops in different regions has a very significant yield increasing effect. Generally, it can reach 5% to 50%, especially in medium and low yield fields where the effect is most significant. In areas where trace elements are severely lacking, targeted use of trace elements on fruit trees and vegetables can increase yields by up to 100%.
（2） Improve crop quality
The application of a large amount of whole element compound fertilizers has improved the inorganic nutrient balance of crops, not only significantly increasing crop yields, but also greatly improving the quality of agricultural products. Some diseases caused by local nutrient deficiencies can be effectively prevented and treated. Agricultural products, especially grains, vegetables, and fruits, have higher levels of protein, sugar, vitamins, trace elements, etc., resulting in better flavor. They can also enhance fiber strength for economic crops such as cotton and kenaf.
（3） Reduce crop pests and diseases
Due to the application of trace element fertilizers, various elements required by crops are supplied in a balanced and reasonable manner, which enhances the ability of crops to resist diseases, cold, high temperatures, and drought. After applying boron to crops, it can promote the normal operation of sugar in the body and enhance resistance. B-sugar complexes are highly acidic complexes, which make the cell fluid more acidic and not conducive to bacterial growth.
The effectiveness of trace elements
（1） Absorption forms of trace elements
Plants can only absorb elements in the form of soluble ions or chelates in water. Iron (Fe) is in the form of Fe2+or metal chelates, manganese (Mn) is in the form of Mn2+or metal chelates, zinc (Zn) is in the form of Zn2+or metal chelates, copper (Cu) is in the form of Cu2+or metal chelates, boron (B) is in the form of H2BO3-, molybdenum (Mo) is in the form of MoO42-, chlorine (Cl) is in the form of Cl -, and sodium (Na) is in the form of Na+.
（2） The influence of trace element availability in soil
Many trace elements are not lacking in soil, but they generally exist as stable compounds that cannot be absorbed by plants. The availability of trace elements in soil is influenced by many factors.
PH: The availability of trace elements in soil generally increases under acidic conditions and decreases under alkaline conditions. Generally speaking, adjusting the pH value to 6.5 is more appropriate and will be beneficial for increasing the availability of trace elements in the soil.
Redox potential: Redox potential has a significant impact on various valence elements. For example, plants absorb Mn2+, and when the soil is in a reduced state, there is more Mn2+available for plants to absorb. This is the case in rice fields and poorly drained soils; In dry land soils with light texture and alkaline reaction, manganese is in a high price state and cannot be absorbed and utilized by plants.
Organic matter: Soil with high organic matter content contains more trace elements, and the decomposition products of organic matter, such as humic acid, have a certain chelating ability for trace elements, which directly affects their availability.
（3） The antagonistic effect between essential nutrients
The nutritional elements required for crops are located in the complex system of soil, where each element has both mutually reinforcing and antagonistic effects. For example, soil rich in phosphorus or excessive application of phosphorus fertilizer often leads to or exacerbates zinc deficiency in crops, and there is a mutual promotion effect between phosphorus and molybdenum. The effect of applying two elements simultaneously is greater than that of applying them separately. When phosphorus fertilizer does not meet the needs, the effect of molybdenum fertilizer often cannot be demonstrated.
The dosage of trace element fertilizers
The soil application rate of trace element fertilizers is roughly equivalent to or even higher than that of nitrogen, phosphorus, and potassium fertilizers, while the soil application rate of trace element fertilizers is relatively low. For example, for most field crops, the application rate per mu is only 1-2 kilograms of zinc sulfate and 0.5-1 kilograms of borax. Economic crops such as fruit trees and vegetables are higher, generally not exceeding 3-5 kilograms per mu. So, before sowing or transplanting, mix the micro fertilizer evenly with damp dry soil or decomposed organic fertilizer, and then apply it together with the base fertilizer in trenches or holes. In addition, most micro fertilizers mixed with phosphate fertilizers will form insoluble substances, which will reduce the fertilizer efficiency of each other, so the two should not be mixed together for application.