Causes of Stunted Growth, Few Branches and Few Siliques in Rape (Rapeseed) Seedlings and Control Methods
When stunted seedlings occur at the rape seedling stage, growth is slow; after the Beginning of Spring, there are not many branches and few siliques, resulting in reduced yield. There are many causes of stunted rape seedlings, and the control methods are:
Stunted rape seedlings
1. Stunted seedlings caused by insect pests:Symptoms: Rape leaves shrink and curl downward, the leaf color darkens, then turns red or yellow, the heart leaves do not unfold, but the root system is normal. Control method: Spray the appropriate pesticide promptly.
2. Stunted seedlings caused by wet planting:The soil is wet and muddy, or transplanting is done during rain, the soil is compacted and not breathable, the development of the rape root system is hindered, the leaves are thin and turn red or yellow, and the heart leaves curl up weakly. Remedial measures: Immediately carry out deep intertillage, apply an additional 750 kg of farmyard manure per mu, mix with 250 kg of plant ash, mix well and earth up around the roots to promote rooting and root development; after 3 to 5 days, apply 1000 kg of pig urine and manure per mu as a seedling-promoting fertilizer, and results will be seen in half a month.
3. Stunted seedlings caused by poor-quality seedlings:Sowing density is high, thinning is not done in time, or the seedling age is too long; at transplanting, most become tall-legged seedlings or seedlings that have already bolted, with few green leaves, and they do not grow after planting. Remedial measures: Intertill and earth up, apply 1000 kg of farmyard manure per mu around the roots to avoid exposure of the root crown, and at the same time apply 0.5 kg of urea and 150 g of potassium dihydrogen phosphate per mu, diluted in 50 kg of water, and spray on the leaves to promote seedling growth.
4. Stunted seedlings caused by waterlogging:The terrain is low-lying and very wet, or drainage is poor, or the beds are wide and the ditches shallow; the soil remains moist for a long time, the field is compacted and not breathable, and after the seedlings are planted, the root hairs rot, the leaves wither and yellow, and the heart leaves do not spread flat. Remedial measures: Open deep ditches and make narrow beds so that all ditches are connected and there is no hidden waterlogging in the soil. On the basis of reducing soil moisture, apply 200 to 250 kg of plant ash per mu around the roots or spread it evenly to absorb moisture.
5. Stunted seedlings caused by fertilizer deficiency:(1) In the early stage, purple-red spots appear on rape leaves, then expand into red leaves; in severe cases, the leaves wither and yellow from bottom to top and fall off, indicating nitrogen deficiency. Apply 1250 kg of pig urine and manure per mu, plus 2 to 3 kg of urea, applied in holes. (2) The leaf color is dark green and lusterless, then turns dark purple, and the veins and leaf blades are purple-red, indicating phosphorus deficiency. Apply an additional 20 to 25 kg of superphosphate per mu, applied in holes beside the roots, and cover with soil after application. (3) The root system develops poorly, the epidermis is brown, the root crown swells and cracks, and the leaves are small and thick, uneven and shrunken. The leaf margins curl outward and are purple-red, and finally wither, yellow and fall off, while the heart leaves are yellow-brown, indicating boron deficiency. Use 150 g of borax (or boric acid) per mu, diluted in 40 to 50 kg of water, and spray evenly on the leaves.
6. Stunted seedlings caused by drought:The root system of this kind of stunted seedling is normal, and the symptoms on the upper branches and leaves are similar to those of stunted seedlings caused by waterlogging. Remedial measures: During drought, apply 3 to 4 times of thin manure water as a topdressing, and normal growth can be restored.
7. Stunted seedlings caused by low temperature:This mostly occurs in rape that is transplanted too late. Because the average daily temperature is below 10°C, the root system has weak recovery ability, fewer new roots are produced, and the absorption of fertilizer and water is insufficient, thus forming red leaves or yellow leaves. Control methods: If the transplanting period is delayed, carefully prepare the land, select large seedlings and transplant them with soil, and apply topdressing early to prevent cold and preserve heat.
8. Stunted seedlings caused by boron deficiency:When rape is deficient in boron at the seedling stage, growth stagnates, roots rot and the heart withers; the rhizome swells. Control method: Spray 6 kg of 0.2% borax solution evenly per mu, for 2 to 3 consecutive times, to control it.