Whether rape is deficient in boron can be judged by observing roots, leaves, stems, flowers and fruits.
First look at the "root". When the soil is seriously deficient in the seedling stage, the young roots stop growing, there is no root hair or lateral roots, the root bark becomes brown, and the cortex is cracked.
Secondly, look at the "leaf". In the seedling stage, the young leaves are chlorotic and brown, spreading to the whole growth point, and it is easy to become a dead seedling. In the middle of the flood season, the middle part becomes dark green, the leaf quality is thickened, brittle, rewinding and shrinking. The leaf edge turns purple and then turns blue-violet, and the leaves fall off in advance. Brassica napus extends from the leaf margin to the whole leaf with a purplish red color. During the wintering period, the red leaves appear more in the middle and lower parts. After the flowering period, the middle and upper functional leaves also appear purple due to boron deficiency.
The third is to look at the "stem". The stem of the boron-poor rapeseed has a slow extension or longitudinal fracture, and the growth of the stem is stagnant. In severe cases, the xylem hollow is yellow-brown or swollen. Longitudinal cracking occurred in the middle and lower cortex of the stem.
The fourth look at "flowers", rapeseed "flowers and not real" is a typical symptom of boron deficiency. In the flowering stage, the flower buds at the top of the inflorescence are greenish and yellow, atrophic and dry, or detached, and the flowering is abnormal. No seeding or formation of only a few deformed horns, the yield is sharply reduced or rejected. Normal rape leaves contain more than 20 mg/kg of boron, while boron-poor leaves have boron content of less than 10 mg/kg.
There are three methods for applying boron fertilizer to rapeseed, such as base fertilizer, top dressing and seed fertilizer. Currently, boron fertilizers sold in various places mainly include borax and boric acid, but mainly borax.
The first is the application of fertilizer. That is, the boron fertilizer is applied to the soil before the live rape or the transplanted rape, and the whole growth and development of the crop is required. In the boron-deficient soil, 15 kg of fine dry soil is mixed with 0.5 kg of borax per 667 square meters or mixed with farmyard manure and chemical fertilizer, but the boron fertilizer cannot be directly contacted with seeds or roots.
The second is topdressing. In the late rapeseed stage, before and after flower bud differentiation, during the twitching period (15 to 30 cm high), 0.2% borax aqueous solution or 0.1% boric acid aqueous solution was sprayed in the flowering stage, and 50 liters of fertilizer solution was used per 667 square meters in the later stage. If it rains after spraying, it needs to be re-sprayed.
The third is to cooperate with the application. Boron fertilizer combined with farmyard manure and chemical fertilizer can better exert its potential for increasing production. 0.5 kg of borax per 667 square meters is better with other fertilizers.
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