Detailed Explanation of Summer Pruning Techniques and Methods for Navel Oranges
I. Variety Selection and Orchard Establishment. Through our comparative observation of 15 navel orange strains introduced and suitable for the subtropical humid climate, we found that Newhall, Linna, Frost, Fukumoto, and New-79 displayed high and stable yields, excellent quality, and strong marketability, making them valuable for promotion and development. The selection of navel orange seedlings should ensure...
Summer pruning of navel oranges has two functions: 1. Renewing localized branches and shoots, and improving the distribution of nutrients in the tree. The growth vigor and fruiting capacity of citrus branches and shoots change as the branching order increases. The higher the branching order, the weaker the secondary shoots produced, until eventually there is almost no ability to produce secondary shoots at all. That is, parts with lower branching orders naturally produce renewal shoots. It is precisely based on this natural law of citrus growth that pruning, mainly through heading back, is carried out to renew weak branch groups on the outer canopy, stimulate reserve branches, and thereby achieve the goal of improving fruiting capacity. 2. Increasing the proportion of secondary shoots and autumn shoots as fruiting mother branches, thus increasing yield. The second shoot segment on which navel orange autumn shoots bear fruit, such as the autumn segment of spring-autumn shoots, summer-autumn shoots, or even the autumn segment of spring-summer-autumn three-cycle shoots, contains twice as much carbohydrate as other one-year-old branches and shoots, and also has stronger physiological activity, so it can accumulate more organic nutrients and become a good fruiting mother branch for the following year. Summer pruning can stimulate abundant, high-quality autumn shoots, which helps increase yield. Combined with winter retrenchment, it improves ventilation and light penetration and extends the number of years of full fruit-bearing.1. Techniques for summer pruning of navel oranges:
1.1 The suitable time for summer pruning: generally, for older trees, heavily fruiting trees, weak trees, and citrus orchards without irrigation conditions, pruning can be done in early to mid-July to force out Beginning of Autumn shoots; for vigorous trees and young trees, pruning can be done in early August to force out End of Heat shoots.
1.2 Pruning targets:
For weak branch groups, navel oranges can be headed back at a point on the base branch of the branch group where the thickness is 0.6-1 cm, leaving a small branch or healthy leaf; for fruiting mother branches that dropped flowers and fruit or branches that dropped flowers and fruit, head back at an appropriate point; for strong spring and summer shoots, head back leaving 5-8 leaves; the extension branches of the main branches and secondary main branches should not be allowed to bear fruit; for upright single-terminal fruit branches, exchange the fruit for shoots by cutting at the base of the fruit stalk.
1.3 Pruning intensity and selection of the cutting position. Because summer pruning is carried out in the vigorous growing season, large saw cuts and heavy pruning are not suitable. The degree of pruning intensity is measured by how many leaves are removed. At the cut position, healthy leaves should always be retained; especially when heading back upright, thick, vigorous branches, a small leafy branch should be left at the cut and then the small branch headed back, so as to avoid disease infection or drying out.
2. Management after summer pruning
2.1 Strengthen fertilizer and water management. Half a month before summer pruning, sufficient high-quality autumn fertilizer should be applied, and the amount applied should account for 40-50% of the total annual fertilizer amount. Fertilization should be combined with irrigation to stimulate autumn shoots.
2.2 Bud removal and shoot release, selection and retention, and pinching. The first bud below the cut sprouts first and should be removed promptly. Wait until the first, second, and third buds and the new buds throughout the tree have generally sprouted; once there are enough of them, bud removal can be stopped. If clustered growth appears, when the new shoots are 10-15 cm long, select and retain 2-3 strong shoots per base branch that are evenly distributed and slanting outward, and remove the weak new shoots.
2.3 The focus of insect control and shoot protection is the control of the citrus leafminer. After shoot release, when the new shoots are about 3 mm long, spray 500x Shachongshuang + 1500-2000x Qianlong, once every 5-7 days, for 2-3 consecutive sprays. After the new shoots unfold their leaves, attention should be paid to controlling red spider mites to ensure the new shoots are not damaged. When spraying pesticides, urea and potassium dihydrogen phosphate can be added for foliar topdressing to promote the greening of new leaves.