What are the fruit-setting measures for papaya trees? Introduction to key cultivation techniques
The purpose of fruit setting is to increase the fruit-setting rate and reduce flower and fruit drop. There are three main reasons for flower and fruit drop in papaya: first, the tree is not vigorous, showing either excessive or weak growth, and the tree body lacks nutrients, causing severe flower and fruit drop; second, poor pollination and fertilization, and the ovary lacks hormones to mobilize nutrients, causing flower and fruit drop; third, excessive fruit set, excessive nutrient consumption, and inability to meet demand, causing fruit drop. In response to these situations, specific measures must be taken to try to set fruit.
1. Reasonable pruning to increase the fruit-setting rate.
On the basis of winter pruning, supplementary pruning before flowering can further regulate the number of flower buds and maintain a suitable ratio of nutrient branches to fruiting branches. Removing excess flower buds early and cutting back and renewing weak branches can save and concentrate nutrients and increase the fruit-setting rate.
Pinching the growing tips of numerous and vigorous new nutrient shoots, removing part of the vigorous stem tip growth points, reducing the synthesis of auxin and gibberellin and nutrient consumption, and alleviating competition for nutrients between vegetative growth and young fruit development can increase the fruit-setting rate.
2. Foliar fertilization.
In early spring before papaya sprouting, spraying the branches with 0.5%-1% urea to supplement nitrogen has the effect of increasing stored nutrients, enlarging the area of early-emerging leaves, improving early photosynthetic efficiency, and promoting fruit setting.
On the premise that the tree grows vigorously and the main mineral nutrients are well supplied, spraying trace element fertilizers has a clear effect on promoting fruit setting, especially in orchards lacking certain trace elements. Spraying 2-3 times around full bloom with 0.3% borax solution plus 0.3% urea solution can promote pollen germination and pollen tube elongation, accelerate the pollination and fertilization process, and significantly increase the fruit-setting rate.
3. Arranging pollinizer trees and auxiliary pollination during flowering.
Papaya self-pollination has a relatively high seed-setting rate, about 50%, while cross-pollination has a seed-setting rate of 87%. The xenia effect is obvious, so appropriate pollinizer trees need to be provided in production. When pollinizer varieties with large fruit and high quality are provided, the fruit they produce is also large.
When the weather is unfavorable during flowering, or the number of pollinizer trees is insufficient or improperly matched, artificial auxiliary pollination is needed. Select high-quality pollinizer varieties and pick bell-shaped flowers about to open from vigorous trees, then remove the anthers. When pollinating, if the quantity is small, use a brush to dip pollen and dab it onto the stigma of fully open flowers; if the quantity is large, use 10 kg water, 0.5 kg white sugar, 30 g urea, 10 g borax, and 20 g pollen to make a 500-fold pollen solution and spray it with a backpack sprayer.
4. Flower and fruit thinning.
Timely thinning of excessive flowers and fruits on papaya trees to achieve a reasonable load is an important technical measure for seeking high yield, stable yield, and high quality, and for preventing and overcoming alternate bearing. Generally, producers thin flower buds during pruning, thin buds before flowering, thin flowers at flowering, and complete fruit thinning from one week to one month after flower drop.
In artificial flower thinning, first thin weak-growing, small, poor-quality flowers; first thin clustered flowering branches and branches with dense inflorescences. First thin the upper part of the tree, then the lower part; first thin the inner canopy, then the outer periphery. On a main branch, thin relatively heavily at the base and tip, and retain relatively more in the middle. For branch group flowers, retain the front and thin the rear in preparation for cutting back. Within an inflorescence, thin the side flowers and retain the central flower.
For fruit thinning, first thin misshapen small fruits, then according to the amount of fruit to be retained, determine whether to retain a single fruit or double fruits. The spacing between retained fruits should be about 20 cm for large fruits and about 15 cm for small fruits.