With the expansion of the planting area of ​​hybrid rapeseed, the symptoms of boron deficiency in the soil have become more and more obvious in the various growth stages of rapeseed, and the area of ​​occurrence has expanded. Atrophy due to boron deficiency has risen to a major physiological disease in rapeseed production.
1 Bone deficiency caused by atrophy is not true Symptoms Types of rape atrophy are not true in all stages of life in rape, but the occurrence of different periods, the symptoms are different, can be summarized into four types.
1.1 Seedling atrophy (dead-eared seedlings) During seedling stage of rapeseed, the new leaves grow slowly, the leaves turn dark green, the leaves become smaller and become more brittle, the leaf ends are rewinded, and the edges are shrunken, and the edges of the middle and lower leaves turn purple. The organization turns yellow and gradually develops and expands to form purple blue patches. The root system was small and fine, short, and the root neck expanded to purple, and finally the whole plant withered and died, resulting in seedling failure.
1.2 Normal growth before the shrinkage of the flood season. After the beginning of the year, the symptoms begin. The leaves in the early stage of the crop shrink, the color becomes dark green or purple, the loquat grows slowly and even stagnates, the internodes are short, and the final plant height is only 1/1/ of the normal plant. 3 or so; root neck enlargement, short and fine roots, flowering inflorescence can not be elongated, buds clustered together, a small number of flowers, but can not form pods and withered, severe whole plant atrophy withered.
1.3 The flowering period shrinks until flowering, the appearance of growth is normal, but after entering the flowering period, the stem elongation stagnant, short, thin and more branches, inflorescence segment elongation is not sufficient, dense flower buds, most flowers, can form a small number of fruit , but the young fruit off, rarely able to bear fruit, late flower buds and inflorescence segments withered, draw many small branches from the base, the formation of secondary flowering.
1.4 Flowers but not real plants do not shrink, the color of stems and leaves is basically normal, and the inflorescence is elongated and soft, which is different from normal plants. Normal flowering, insemination and fertility, the performance is basically not strong or partially fruitful, but the short fruit is a strong fruit, the angle of the small is "radish" horny, some pods are purple gray, the grain shape is irregular, the size is not uniform . The inflorescence at the end of the later period did not thank the flowers, there is a "return to flower" phenomenon.
2 Causes of boron deficiency disorders
2.1 Soil Boron-boron and Nitrogen-boron ratio imbalance Generally, the available boron content in soil is lower than the critical value of 0.5 mg/kg. One of the soil samples contains boron or because of the high content of available nitrogen, the proportion of nitrogen and boron is out of balance, and the symptoms of boron deficiency are prominent.
2.2 Variety differences According to the survey, the occurrence of the local cultivars of Chinese cabbage and mustard varieties is light, and the incidence of common rapeseed rape is relatively heavy, and the occurrence of hybrid rape is the most serious. The breed with long growth period is heavy and the growth period is short. Hybrid rape is particularly sensitive to boron.
2.3 Large-scale continuous cropping of rapeseed 1 to 2 years of field disease is light, continuous disease for more than 3 years. Because of the long duration of continuous cropping, a large amount of boron is depleted from the soil and no supplementation is available, resulting in a serious lack of boron or a disproportionate ratio of nitrogen to boron. At the same time, rapeseeds growing in successive plots are weak, susceptible to disease, and their ability to absorb nutrients is also reduced.
2.4 Reduction of Organic Fertilizer Application A reduction in the number of plots with more organic fertilizer occurs, and less organic fertilizer or heavy crop weight.
3 Prevention and control strategies to prevent boron deficiency in rapeseed must be based on the comprehensive application of boron fertilizer comprehensive protection measures.
3.1 Carry out crop rotations using rapeseed-rice-wheat or rapeseed-rice-ricein or rapeseed-red-wheat-wheat rotation to prevent continuous cropping for more than 3 years.
3.2 Expand the area of ​​deep ploughing, increase the organic fertilizer application to expand the area under cultivation, change the shallow plough to deep ploughing, and increase the depth of plough layer. Increase the amount of organic fertilizer input, increase the application of soil miscellaneous fertilizer 3000 ~ 4000kg.
3.3 Application of boron fertilizer According to the available boron content in soil and the occurrence of boron deficiency disease, the cultivated land can be divided into severe boron deficient areas (below 0.25mg/kg), deficient areas (0.25~0.41mg/kg) and mild boron depletion areas. (0.41 ~ 0.5mg/kg), the implementation of boron application zone, according to local conditions, and do a good job at the end of application and topdressing. Heavy boron depletion area applies 1 to 1.5kg of boron fertilizer per acre, boron deficiency area applies 0.75~1kg per acre, mild boron depletion area applies 0.5~0.75kg per acre, and base fertilizer can also be combined with NPK fertilizer. Use, better results.
Top dressing is mainly used as foliar spray. In the seedling stage and flood season sprayed twice, spraying concentration of 0.1% to 0.2% that is 50 to 100kg of boron fertilizer 50kg of water, even spraying foliar, can also be mixed with potassium dihydrogen phosphate or urea spraying.