In the early spring rape field management stage, improper fertilization during sowing and transplanting or the lack of certain nutrients in the soil caused poor growth of rape. If remedial measures are not taken in time, the yield will be affected.
When nitrogen-deficient rapeseed is deficient in nitrogen, its leaves are yellowish, its growth is weak, and the plants are short. Generally, nitrogen-deficient red leaves are prone to appear during drought.
Remedial measures: topdressing 7.5 kg of urea per mu, or splashing 15-20 kg of ammonium bicarbonate with 500-700 kg of water.
Phosphorus-deficient rapeseed plants lack phosphorus, grow slowly and are short, the leaves become smaller, the mesophyll becomes thicker, and the leaves are dark green or gray-green, and lack luster. The petiole is purple, and the edges of the veins are purple-red spots or patches. There are 2 to 3 fewer leaves than normal plants, slow bolting, and reddish moss.
Remedial measures: topdressing 25-30 kg of superphosphate per mu, or spraying potassium dihydrogen phosphate on leaves continuously for 2 to 3 times.
Potassium-deficient rapeseed starts with the old leaves, which are yellow spots at first, "scorched edges" and light brown withered spots gradually appear on the tip and edge of the leaves, the leaves become thicker, harder, and brittle, and the mesophyll tissue is obviously "scalded" , Followed by wilting.
Remedial measures: topdressing 7.5-10 kg of potassium chloride per acre mixed with 500-700 kg of water and sprinkling, or mixed with 100-150 kg of plant ash.
Boron-deficient rapeseed requires a large amount of boron fertilizer, but the soil contains less boron, so rapeseed is most vulnerable to boron deficiency. Roots of plants deficient in boron cease to grow, without root hairs and lateral roots. The leaves appear purple patches or blue-purple patches, the leaf margins are inverted, and the rhizomes are enlarged. Boron deficiency during flowering will cause "flowers but not fruit", that is, no pod formation after flowering.
Remedy: Use 150-200 grams of borax per acre and 150-200 kilograms of water for spraying, or 50-100 grams of borax with 50 kilograms of water for spraying on a sunny day in the afternoon.
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