As the saying goes, "A crop is like a flower, and it all depends on fertilizers." For the normal growth of rape, 17 essential nutrient elements are required. Among them, carbon, hydrogen, and oxygen can be obtained from the air and water, and generally do not need to be provided in the form of fertilizers. Nitrogen, phosphorus, and potassium have relatively high contents in crops and are also absorbed in large amounts, which are called "macronutrients" and commonly known as the "three major elements of fertilizers", among which the demand for nitrogen is the greatest. Calcium, magnesium, and sulfur are "medium elements", and rape is relatively sensitive to sulfur. Elements such as copper, zinc, iron, manganese, boron, and molybdenum are "trace elements". Rape is a boron-loving crop and is also relatively sensitive to trace elements such as zinc and molybdenum. Rape is a biennial crop with a long growth period and needs to overwinter for normal "vernalization" to bloom and set pods normally. If a certain nutrient is lacking during the growth period, it often shows some unique nutrient deficiency symptoms in the growth form. Nutrient deficiency will cause metabolic disorders and lead to abnormal reproductive phenomena. So, what are the symptoms of nutrient deficiency in rape? And at what stage do these symptoms appear? This article will briefly introduce the symptoms of nutrient deficiency in rape!
Schematic diagram of the location where symptoms of crop nutrient deficiency appear
When rape is deficient in nitrogen, the growth of new leaves is restricted, there are few leaves, and the leaf color is pale. The lower leaves first turn yellow from the leaf margin and gradually spread to the veins. There are many yellow leaves. Sometimes, the leaf color gradually fades and turns purple. The lower leaves of the stem turn red, and in severe cases, they show a scorched state, with pale red leaf veins. The plant grows thin and weak, the main stem is short, slender, and the plant shape is loose. It blooms early and the blooming period is short. The final flowering period is advanced, the pods are sparse and the quantity is small. The roots are long and thin.
Comparison of nitrogen-deficient rape and rape applied with nitrogen fertilizer during the bolting stage
When rape is deficient in phosphorus, the leaves are small and cannot naturally spread out, showing a grayish green, dark green to light purple color. The upper leaves are dark green and dull, and the middle and lower leaves are purplish red. The leaf flesh is thick, and in severe cases, the leaf margins necrotize and the old leaves wither prematurely. The stem is grayish green, blue-green, or purplish red. The plant is short, the stem is thin, there are few branches, the plant is slender and upright, and the pods are sparse and small. The flowering is delayed, and the maturity period is 1-2 days later.
Symptoms of phosphorus deficiency in rape during the bolting stage
When rape is deficient in potassium, the seedlings are in a prostrate state, the leaves are dark green, the edges of the lower leaves lose their green color, and there are scald-like spots in the leaf flesh. In severe cases, the edges and tips of the leaves show scorched edges and light brown to dark brown necrotic spots, and the leaf surface is uneven. After bolting, the symptoms are more obvious. The chlorosis between the leaf margins and veins spreads rapidly, and there are brown patches or white dry tissues. In severe cases, the leaf margins are scorched, and sometimes the leaves curl, looking like they are burned and wither. The plant is small and thin, the growth of the main stem is slow, the stem becomes brittle, and it is easy to break in case of wind and rain. The pods are scarce, the pods are poorly developed, and there are many short pods. The disease resistance, cold resistance, and lodging resistance are poor. The yield and oil content decrease.
The typical symptoms of potassium deficiency in rape are shown in the left leaf.
When rape is deficient in calcium, the plant is short. The young leaves lose their green color and become deformed, the leaf margins curl downward and form a hook shape, the edges of the lower leaves are scorched, and in severe cases, the growing point necrotizes. The leaf tips and growing points are in a mucilaginous pectin state, and the top flowers are easy to fall off. During the pod-setting period, the top of the inflorescence is bent, the growing point is damaged, and in severe cases, it necrotizes, showing a "broken neck" symptom. The roots turn black and rot due to calcium deficiency.
Typical symptoms of calcium deficiency in rape during the early flowering stage
When rape is deficient in magnesium, obvious purplish red patches appear on the lower old leaves. In the middle and later stages, the interveinal areas of the old and middle leaves lose their green color, showing yellowish purple and greenish purple mottled leaves, and the color of the upper leaves fades. In severe cases, the leaves wither and fall off prematurely. The flowering is often inhibited, the petals are pale, and there is no obvious change in the size of the plant.
Typical symptoms of magnesium deficiency in the lower leaves of rape
When rape is deficient in sulfur, the seedlings are narrow and yellowish. The initial symptom is that the plants are light green, the color of the young leaves is lighter than that of the old leaves, the veins lack green color, and later it gradually spreads to the whole leaf. The back and tips of the leaves turn red, the leaves are upright, and the leaf margins curl upward. The flowering and pod-setting are delayed, the flowers and pods are pale, the flowers are small and few. The tips of the pods are shriveled, and the seeds are poorly developed. The plant is short, and the stem is lignified and easy to break.
Typical symptoms of iron deficiency in rape during the seedling stage
When rape is deficient in manganese, the young leaves lose their green color and turn yellowish white, the veins are still green, and the areas between the veins are grayish yellow or grayish red, showing a reticulate vein pattern. There are light brown spots on the leaves, and the symptoms then spread to the old leaves. The plant generally has weak growth potential, is yellowish green, has few flowers, and the number of pods is also correspondingly reduced.
Symptoms of manganese deficiency in rape leaves
When rape is deficient in zinc, the plant is short and the internodes are shortened. The leaves are small and slightly thickened, and purplish red anthocyanins appear on the back of the leaves. In severe cases, the color fades from the leaf margins first and turns grayish white. The middle and lower leaves with serious albino symptoms are wrinkled and turned outward, and the leaf tips droop downward. The growth period is delayed, and in severe cases, the flowering is inhibited, and it may even fail to set seeds completely.
Typical symptoms of zinc deficiency in rape during the seedling stage
Among field crops, rape is the most sensitive to boron deficiency. When lacking boron, the leaves are dark green and wrinkled during the seedling stage, showing purplish red patches or the leaves are purplish red, and sometimes the petioles crack. The root collar swells and the cortex cracks. Prostrate seedlings appear, and in severe cases, it causes the death of seedlings. During the bud and bolting stage, rose red appears from the leaf margins to the inside of the middle leaves, the leaf texture thickens, becomes brittle, and curls backward. The bolting stem extends slowly, and even the top of the main stem shrinks, and sometimes the phenomenon of "stem cracking" occurs. The top flower buds develop abnormally, fade and turn yellow, and even shrink, wither, and fall off. During the flowering stage, the main inflorescence and branch inflorescences are obviously dwarfed, and the top shrinks. Some petals are wrinkled, the color becomes darker, the pollen grains, stigmas, and ovaries are not well developed, the flowering process is slow or the flowering is abnormal, and young fruits cannot be formed normally. During the pod stage, the regenerated branches or clusters of branches emerge from the leaf axils and continue to bloom until the maturity stage, that is, the phenomenon of "reblooming". The whole plant obviously has the phenomenon of "flowering without setting fruits", there are very few pods, they are deformed, the maturity period is significantly delayed, the number of grains is very small, and the seeds are of uneven size.
Comparison of pods of boron-deficient rape and rape applied with boron fertilizer during the maturity stage
When rape is deficient in molybdenum, the seedlings are short, thin, and the development is slow, and the true leaves are drawn out slowly. The leaves wither or are scorched, the leaf margins turn yellow, and the leaves are twisted in a spiral shape. After suffering from low-temperature stress, water-soaked spots appear on the leaves, and then the spots gradually spread until the whole leaf withers. The growth period is delayed, and the flowering and seed setting are postponed.
Symptoms of molybdenum deficiency in rape in the field
Warm reminder: Yishizhuang special fertilizer for rape contains macronutrients (nitrogen, phosphorus, potassium), medium elements (calcium, magnesium, sulfur), and trace elements (boron, zinc, etc.) required for the growth of rape. The nutrients are comprehensive and balanced, and the ratio is scientific and reasonable, which can meet the nutrient needs of the whole growth period of rape. There is no need to apply calcium, magnesium, sulfur, boron, zinc, molybdenum fertilizers separately, which saves labor, time, and fertilizer, and truly makes up for what is lacking. Applying Yishizhuang special fertilizer for rape properly and sufficiently, compared with the fertilizers that farmers are used to buying, the increased production and income are equivalent to the price of buying a bag of fertilizer. In the long run, this is a "zero investment" that gets completely different results with the same amount of money!