What are the key points for managing a citrus orchard in winter?
The key points for managing a citrus orchard in winter focus on the following aspects:
1. Remove winter shoots. As temperatures drop, citrus fruit trees gradually enter a relative dormant period. In the South Asian tropical citrus production areas where temperatures are relatively higher, young citrus trees will sprout scattered winter shoots. Winter shoots grow thin and weak and are not easy to mature, have no useful value, and should be removed in time to avoid consuming nutrients, which is not conducive to nutrient accumulation.
2. Harvest at the right time and store properly
(1) Harvest at the right time: In December, the late-maturing varieties among citrus fruits have matured and entered the harvest period. At this time, harvesting should be carried out in successive stages and batches according to the maturity period and the fruit's color, size, weight, soluble solids, and other indicators. When harvesting, you can first pick the yellow ones and leave the green ones, carrying out the harvest in 2-3 rounds, with graded harvesting. Each tree should be harvested according to three grades: large, medium, and small, and harvested in stages and batches according to the amount for market. If the fruit is to be used for storage, it can be harvested when 70-80% mature; for fresh eating, it should be harvested when 80-90% mature.
(2) Proper storage: Fruit harvesting must be done after the dew has dried on a sunny day. To avoid mechanical injury to the fruit, use the “one fruit, two cuts” method: first cut 1-2 cm from the fruit stalk, then cut flush with the fruit stalk, cut lightly, and handle gently. After harvesting, remove injured, diseased, and insect-damaged fruit, grade by size, box them, and sell. For fruit intended for storage, after harvest it should immediately undergo chemical treatment, be drained of the solution in a cool place, pre-stored to sweat, then wrapped individually in film, and then put into storage.
3. Fertilizer and water management. Apply harvest fertilizer appropriately: late-maturing varieties should be given one harvest fertilizer application before harvest to help promote recovery of tree vigor and flower bud differentiation. After harvest, spray once with 0.3% urea + 0.3% monopotassium phosphate for foliar feeding, and irrigate once to help restore tree vigor, preserve leaves through winter, and enhance cold resistance. For trees in an on-year, old and weak trees, appropriately apply nitrogen fertilizer; for trees in an off-year, increase phosphorus and potassium fertilizer, combined with deep plowing and green manure incorporation for soil improvement. Before harvest, appropriately control water to facilitate fruit storage and promote flower bud differentiation. However, in dry winter areas, attention should be paid to appropriate irrigation, which is beneficial to root growth, helps restore tree vigor, and reduces winter leaf drop; in low-temperature areas, irrigate appropriately to improve the plant's cold resistance.
4. Pruning and orchard cleanup. After harvest, clean up the orchard, pruning diseased and insect-damaged branches, dead branches, crossing branches, and overlapping branches. To reduce overwintering pests and diseases, the pruned diseased and insect-damaged branches and dead branches and fallen leaves should be gathered and burned. When pruning, proceed reasonably according to the growth characteristics of citrus. For strong branches pressing the top, use the “skylight” method by removing them from the base of large branches. Thin out shaded branches and crossing and overlapping branches inside the canopy, and retract branch groups between rows and on the outer canopy that block sunlight, so as to maintain ventilation and light penetration within the tree body and the orchard.
5. Pest and disease control. After harvest, when tree vigor has basically recovered, spray promptly to control winter pests and diseases. When spraying, ensure the whole tree is sprayed evenly, comprehensively, and thoroughly; the inside and outside of the canopy, trunk, main branches, framework branches, and branches at all levels must all be sprayed. Only in this way can overwintering adult insects, larvae, and eggs be eliminated. The agents used include 0.8-1 degree Baume lime sulfur mixture, 10-15 times rosin-soda mixture and 99% diesel oil emulsion 150 times, 40% Supracide emulsifiable concentrate 800-1000 times, etc.
6. Deep plowing and soil improvement, mounding soil and mulching to protect roots. In winter, citrus orchards should be deeply plowed throughout the orchard to improve the soil, preferably before frost, with a depth of about 30 cm. It should be shallower within the drip line of the canopy and deeper outside the drip line. Most orchards in South China are acidic red-yellow soils, with a pH value between 5-6.5. When turning the soil, spread lime (100 kg of lime per mu). First, it can neutralize soil acidity; second, lime has the effect of eliminating overwintering pests and diseases. After turning, the tree basin should be properly shaped around the root zone; mound soil 10 cm and cover with rice straw, crop stalks, dry grass, etc. to protect the roots and enhance cold resistance for overwintering.