What does "flowers but no seeds" mean in rapeseed cultivation?
What is rapeseed "flowers but no seeds"? What methods are there to prevent and control it? Please explain. Rapeseed "flowers but no seeds", also called stunted sterility, means that from the onset of the disease to maturity, the plant keeps flowering continuously but cannot set seed normally. The main cause is a physiological disease caused by growing rapeseed on boron-deficient soil, mainly occurring in Brassica napus varieties, but in recent years it has also been found in Brassica rapa rapeseed. After the disease occurs, yields generally drop by 20% to 30%, and in severe cases there is even almost no harvest, making it a problem worth attention in rapeseed production.
What is rapeseed "flowers but no seeds"? What methods are there to prevent and control it? Please explain.Rapeseed "flowers but no seeds", also called stunted sterility, means that from the onset of the disease to maturity, the plant keeps flowering continuously but cannot set seed normally. The main cause is a physiological disease caused by growing rapeseed on boron-deficient soil, mainly occurring in Brassica napus varieties, but in recent years it has also been found in Brassica rapa rapeseed. After the disease occurs, yields generally drop by 20% to 30%, and in severe cases there is even almost no harvest, making it a problem worth attention in rapeseed production.
The role of boron in rapeseed:Rapeseed is a crop with a relatively high boron requirement. Boron can promote pollen germination, enable the pollen tube to quickly enter the ovary, and help seed formation.
The most obvious sign of boron deficiency is "flowers but no seeds". With severe boron deficiency, rapeseed can develop the disease at the seedling and bolting stages, and affected plants wither and die. With moderate or mild boron deficiency, the disease appears after the flowering stage, and affected plants cannot set seed normally. Increasing boron fertilizer application can effectively prevent and control rapeseed "flowers but no seeds".
Tests have shown that growing double-low rapeseed in boron-deficient areas and adopting boron application measures can generally increase yield by 10% to 20%. Research shows that compared with Zhongyou 821, double-low rapeseed has a stronger boron uptake capacity and a higher boron requirement. When soil water-soluble boron is below 0.5 PPm, boron deficiency symptoms of varying degrees can appear and cause severe yield loss; when water-soluble boron reaches or slightly exceeds 0.7 PPm, yield can increase significantly.
Introduction to boron fertilizer:Boron fertilizer is a kind of trace element high-efficiency fertilizer. Compared with nitrogen, phosphorus, and potassium fertilizers, rapeseed requires relatively little of it, and the boundary between an appropriate amount and an excessive amount is very small; excessive amounts often cause toxicity. At present, the most commonly used boron fertilizer in domestic rapeseed production is borax (the sodium salt of boron), which is low in price, easy to use, contains 11% boron, and has less active ingredient than boric acid, but the application effect is the same. In addition, there are boron-containing compound fertilizers, such as phosphorus-boron fertilizer. Since these elements are all essential elements for rapeseed growth and development, they have a significant effect on increasing rapeseed yield.
Methods of applying boron fertilizer to rapeseed:To prevent and control rapeseed "flowers but no seeds" and ensure high rapeseed yields, on the basis of applying boron fertilizer as a basal application, foliar spraying of boron fertilizer at the bolting stage and when the bolt is about 3 cm high has a very good effect. The spraying concentration is 0.1% to 0.3%, that is, 0.1 to 0.3 kg of borax added to 100 kg of water to prepare a boron-containing aqueous solution, sprayed evenly on the rapeseed leaves.
Boron spraying should be done on a clear evening or morning. This is because relative humidity is high at these times, and open stomata help rapeseed absorb it into the plant. Spraying is not suitable in dry or windy conditions. If rain occurs within 36 hours after spraying, it should be sprayed again.
The most critical periods for boron spraying of winter rapeseed are the seedling stage and the bud-bolting stage. This is because boron spraying at the seedling stage can promote root growth and help flower bud differentiation proceed normally; boron spraying at the bud-bolting stage promotes stem extension, prevents leaves from turning from green to red due to boron deficiency and weakening photosynthesis, and especially ensures the normal development of flower buds and other reproductive organs and avoids the occurrence of "flowers but no seeds". Therefore, spraying boron once each at the seedling stage and the bud-bolting stage has a significant yield-increasing effect.
Although foliar boron spraying has a significant yield-increasing effect, in severely boron-deficient areas or soils, if spraying is done only a few times, boron spraying often cannot timely guarantee rapeseed's boron requirement, so the spraying effect is lower than that of basal application.
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