The role of phosphorus in crops

Lack of soil phosphorus second only to nitrogen deficiency area, accounting for about 3/4 of the total area of arable land. The amount of phosphate fertilizer is also second only to nitrogen fertilizer, and the fertilizer effect is remarkable. It plays an important role in transforming low-yield fields and building high-yield and stable fields.

Phosphorus is one of the three major nutrients necessary for crops. It has a significant impact on the growth of crops, the level of yield, and the quality of the crop.

First, the physiological role of phosphorus

Phosphorus (P ₂ O ₅ ) is present in the crop body in an amount of about 0.2% to 1.1% by weight of the dry matter. Phosphorus content is second only to nitrogen in crop seeds, but varies greatly from crop to crop. For example, the seeds of cereal crops contain 0.6%-0.8% of phosphorus, soybeans and peanuts in oil crops contain about 1%, and the roots of sugar beet only account for about 0.16%.

(1) Physiological action of phosphorus It is one of the important elements that make up organisms, and other elements cannot be substituted. Phosphorus is a component of nucleic acids, nuclear proteins, phospholipids, phytochemicals, adenosine phosphates, and enzymes, and is involved in many metabolic processes in crops. Nucleoproteins are synthesized by nucleic acids and proteins. They are the main components of the nucleus and protoplasm. They are distributed in the vigorous growth of young leaves, sprouts, and root tips. They are responsible for cell proliferation and genetic variation. Phospholipids form a membranous structure with proteins, which are both hydrophilic and hydrophobic, and can enhance the permeability of cells. Phospholipids are amphoteric compounds containing acidic and basic groups, which can increase the regulation of pH and improve the resistance of crops to saline and alkali. ability. Phytochemical is a storage form of phosphorus in seeds. When the content of phytochemicals is high, the quality of seeds is good, and it is beneficial to the accumulation of starch in the late growth stage. Adenosine phosphate is a transfer station for energy storage and supply in crops. Enzymes and phosphates are involved in the synthesis, functioning and various biological metabolism of substances in crops.

(II) Effect of phosphorus on crop quality Phosphorus is sufficient to promote the synthesis and metabolism of substances in crops, and the yield and quality of crops are also improved and improved. The Soil and Fertilizer Institute of the Chinese Academy of Agricultural Sciences increased the application of phosphate fertilizer in the phosphorus-deficient plots in Hebei, and the phosphorus content of wheat seeds and straw increased by 16% and 51%, respectively. The improvement of nitrogen and phosphorus content in crops can increase the content of protein and amino acids in products.

The addition of phosphate fertilizer can prevent the plant from being blocked due to insufficient phosphorus, and the accumulation of sugar in the leaves increases, forming more anthocyanins, affecting the appearance of the products, such as corn, tomato and rapeseed. Fuchsia stripes or spots appear prominently. Phosphorus is sufficient, the seed content in the seed is high, the quality is good, and the rooting speed of sprouting is fast. Phosphorus is insufficient, the product is poor in storage stability, and the potato chips of the potato crop are also small.

Second, the effect of increasing the yield of phosphate fertilizer

In 1994, China's phosphate fertilizer (P ₂ O ₅ ) application rate was 9.69 million tons (including phosphorus contained in compound fertilizer), accounting for 29.2% of total fertilizer application. The ratio of nitrogen (N) to phosphorus (P ₂ O ₅ ) is 1 to 0.47. In the case of applying farmyard manure or nitrogen and potassium fertilizers, the application of phosphate fertilizer to various crops has obvious yield increasing effects. According to a large number of test results conducted by the National Fertilizer Testing Network in the 1980s, under the current fertilization level, the average yield per kg of phosphate fertilizer (P ₂ O ₅ ) increased by 4.3-9.7 kg, lint 0.7 kg, and soybean 2.7 kg. Rapeseed 6.3 kg, peanut 2.5 kg, sugar beet 47.7 kg, sugar cane stem 80 kg, potato 33.2 kg, flax 1.9 kg (Table 1).

Table 1 Phosphate fertilizer (P ₂ O ₅ ) fertilizer efficiency of different crops (unit: kg)

The above test is to apply phosphate fertilizer on the basis of the same amount of nitrogen fertilizer or nitrogen and potassium fertilizer, and the phosphate fertilizer variety is mainly calcium. It is seen from the test results that the fertilizer efficiency of most crops such as grain is only 40% to 50% of that of nitrogen fertilizer. However, the residual amount of phosphate fertilizer in the soil is large, and the aftereffect is generally maintained for 5 to 10 years, while the nitrogen fertilizer is only 1 to 2 years. The cumulative fertilizer efficiency of phosphate fertilizer is often greater than that of nitrogen fertilizer.

Third, the symptoms of crop phosphorus deficiency

The potential phosphorus deficiency stage of crops is difficult to diagnose from the appearance, but when the phosphorus deficiency is serious, it can be seen in the field: rice has “stiffness” and “sit”, wheat forms “small old seedlings”, corn has increased baldness, rapeseed De-pod, fruit trees and flowers fall off. When the cereal crops are deficient in phosphorus, the tillers, heading, flowering and maturity of the plants are delayed; the leaves of the rice are erect, the leaves are dark green, and the lower leaves are withered and yellowish brown. Excessive application of phosphate fertilizer is not as sensitive as nitrogen fertilizer, but it is easy to cause premature aging of crops, affecting yield and benefit.

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