In autumn and winter of 1995, the weather was a mix of rain and sunshine. From early spring to the onset of heavy rains, temperatures were relatively high. However, after nine days of continuous rainfall, the temperature dropped significantly. If winter fertilizer was applied to teak trees before the rain, the low temperature and wet conditions reduced the root’s ability to absorb nutrients, slowed root growth, and even caused root rot. Some pomelo orchards did not irrigate their fertilization ditches in time, leading to dry ditches that were too deep. This made it easier for spring rains to cause waterlogging and further damage to the roots, resulting in significant leaf drop. Overall, the main reasons for extensive leaf loss during winter and spring included low temperatures, mechanical injuries, prolonged drought, improper pesticide use, pests and diseases, over-fertilization—especially excessive acid fertilizers—which led to yellowing of old leaves and massive defoliation, with more than 80% of leaves falling in some cases. In severe situations, up to 100% of the foliage could be lost. Some citrus trees suffered large-scale leaf loss.
Orchard management issues also contributed to the problem. For example, applying more than two or two borax units per grapefruit tree led to boron toxicity. This caused yellowing of old leaves in winter and resulted in over 90% leaf drop before the cold season. Although new leaves emerged in spring, there were few flowering buds, leading to poor fruit set and small fruits. During bad weather, mixing too many types of fertilizers and placing them too close to the trees increased the risk of root rot and subsequent leaf fall. Prolonged drought created additional stress, especially when wounds from pruning or girdling were larger than 1 cm. Deep plowing during winter damaged roots, causing severe leaf loss. After soil expansion, the damage often led to more spring flowers but poor fruit development. Throughout the year, weak trees had a higher risk of fruit cracking during ripening.
Spring shoots and young leaves were often exposed to high concentrations of pesticides, which severely damaged new growth, impaired chlorophyll production, and caused winter leaf yellowing and heavy defoliation. Poor drainage in pomelo orchards, combined with deep plowing and spring rains, allowed water to seep into the soil around the roots, weakening the trees and causing leaf loss. Excessive use of acid fertilizers, such as heavy calcium, potassium sulfate, and potassium chloride, led to soil acidification, land collapse, and nutrient loss, all contributing to leaf drop.
In orchards with weak tree vigor, high concentrations of rosin mixtures used in winter caused defoliation after spraying. The use of lime sulfur on deciduous plants in these areas also contributed to leaf loss. Lignosulfate cocktails are generally not recommended for grapefruit trees. Pests and diseases were another major threat, causing yellowing of leaves in late fall and heavy leaf drop in cold winters.
To address these issues, several measures were proposed: (1) Improve overall orchard management practices. (2) Increase the use of farm manure to enhance soil fertility. (3) Apply nitrogen, phosphorus, and potassium in proper amounts, while adding calcium and magnesium phosphates. Reduce the use of calcium superphosphate and apply lime in summer to neutralize acidic soil and increase calcium levels. (4) During the spring shoot and young fruit stage, spray a mixture of one and a half borax and potassium dihydrogen phosphate at a rate of 1-2 times per 100 pounds of water. (5) In winter, cultivate shallowly around mature and old trees without deep-rooting. Weeding should only occur outside the canopy. Special attention must be given to orchards in paddy fields to protect root growth and maintain evergreen foliage. In winter, each old pomelo tree should have one or two sprigs girdled to avoid complete girdling, ensuring the preservation of tree vitality and preventing excessive leaf loss that could reduce flower production and ultimately affect fruit yield.
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Breathing Filter
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Size: adult/Child/infant
Type: Angled type/Straight Type
Color: Green,blue, purple
STERILE :EO
Package: Individual package
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