Bag Preparation
Make holes into the transplanting bags for drainage. When you perforate the bags, space the holes to make sure that the drainage is not impaired in any part of the medium.
For larger bags, bore the holes beginning from the lower half of the bag downward. The lowest line of holes should be placed at the base of the filled bag. This could be determined by filling the bag enough medium to let it stand. The point which forms the edge of the base is the right place to position the holes equally distanced from each other.
For bags with ready-made folds (not gazette type), cut-off the two bottom corners (square in size) of the bag. These holes are built purposely for good drainage and aeration.
Transplanting
Uproot the seedling carefully. Before transplanting, soak the selected seedlings for 3-5 minutes in a fungicide solution (1-2 tbsp per gallon of water) for added protection. Transplant them 8 in x 12 in bags.
Press down the medium so that it has good contact with the roots. Water the seedlings immediately after transplanting. Keep the newly transplanted seedlings in the shade until they can withstand the sun and rain. During this critical stage, it is necessary to control fungal pathogens especially those responsible for damping off.
Nutrition
Fertilization is essential to optimize the growth of potted plants. However, insufficient nutrition will result in poor growth while over fertilization can result in vegetative growth, pH imbalance, excess nutrients, and salinity.
If the media mixture used has sufficient amount of compost, this could be enough to supply the nutrient requirements of the citrus plants until they are ready for transplanting. Otherwise, supplement with commercial fertilizer through fertigation (applying fertilizer dissolved in irrigation water) or basal application.
A solution containing 540mg/L of potassium nitrate and 857 mg/L ammonium nitrate could meet sufficiently the approximate requirement of 80% nitrate and 20% ammonium nitrate.
Irrigation
Water is very essential for normal growth of plants. Exercise care irrigation; see to it that the medium is kept moist to prevent drying of the seedlings. However, too much watering could create problems like leaching of nutrients and encouraging disease incidence.
The simplest way to determine if the medium has the right amount of moisture is to squeeze some of the medium in your hand. If the medium forms a tight ball when squeezed, this means the medium is too wet. A medium with the correct amount of moisture should crumble even when squeezed.
Asexual Propagation
For citrus, the usual propagation methods used by the Center are chip budding and side grafting. Only uniform healthy seedlings should be asexually propagated. Seedlings at 4-5 months are ready for side grafting, while seedlings at 6-10 months are propagated through chip budding.
Budding and grafting can be done anytime, if there is a suitable stock on which the bark is slipping or vigorously growing, and when suitable bud wood is available. Usually, the bark is slipping in April to November, depending on location.
To produce new plants, choose rootstocks of pencil size to 2 cm (3/4 in) diameter. Prune thorns and twigs from the area to be budded. The area to be budded should be at least 15 cm (16 in) above the soil level.
Selecting scion/bud wood. Collect buds from a tree of the desired variety.
· Select bud sticks from the next to last flush (the wood behind the current flush), and from the current growth flush after it has matured and hardened. You can use older growth flushes if the bark is still green. Round twigs about the size of a pencil are preferred. The buds located in the axils of the leaves (where the leaf is attached to the wood) should be well-developed, but still dormant.
· After cutting the bud wood from the tree, remove the undesirable wood and/or growth flush.
· Trim the remaining bud wood to 20-25 cm long (8-10 in).
· Cut off leaves leaving a stub of the petiole 3-4 mm (1/8 in) long to protect the buds.
· Label the trimmed bud sticks and use immediately, or place in plastic bags and store in a cool place. Include a moist paper towel to maintain the turgidity and freshness of bud sticks.
Storing bud wood/ scion. After collection, use bud wood as soon as possible, but it can be stored for several months under proper conditions.
· Seal the bundled bud sticks in a plastic bag and store in a refrigerator. The optimum storage temperature is 5 degrees Celsius (40 degrees F); it should not be allowed to go below 2 degrees Celsius (35 degrees F). The vegetable drawer of the refrigerator is the best place.
· Check the stored bud wood every 2 weeks for the presence of mold or excess moisture in the bag. Bud wood lightly affected with mold should be carefully washed in cold soapy water, rinsed and re-bagged in a clean bag. Excessively moist bud wood can be blotted lightly on paper towels. Discard moldy, shriveled, or darkened bud wood.
Selection of rootstock. The rootstock variety must have the following characteristics:
· Compatible with the scion variety allowing good growth, long life, good yield, and good fruit qualities;
· Readily available, preferably polyembryonic to get uniform seedlings and high percent germination;
· Adapted to a wide range of soil depth, texture, structure, pH, salinity, moisture, and nutrient supply; and
· Resistant to soil-borne disease like Phytophthora gummosis.
Steps in Chip Budding
1. Prepare the rootstock (clean the selected portion 6 in above the ground).
2. Make a notch on the desired portion.
3. Make a slant V cut above the notch (2 cm long).
4. Prepare the scion/ cultivar following steps 2 and 3.
5. Place the scion/ bud eye into the rootstock.
6. Wrap with budding tape.
7. Observe for 3 weeks to 1 month.
8. Remove budding tape.
9. Observe the bud eye for 1 week.
10. Top cut the plants having green bud eye to reduce the growth and to produce new plant.
Steps in Side Grafting
1. First, a small (about 5 mm) upward cut is made on the flat portion of the rootstock beside the third or fourth bud. The tissue is completely removed. This is followed by a downward cut with a thin sliver of wood, about 1.0 cm, just below the first cut, like a flap.
2. Then, the scion, about 1.5 cm, consisting of only one bud, is cut just above the bud. The longer portion is below the bud. A thin sliver of the bark and wood is also removed on the flat portion of the scion, and a slanting cut is made at the back portion.
3. The bud is inserted into the rootstock.
4. To fix the bud in place, it is wrapped with parafilm (Parafilm ‘M’), instead of the usual budding tape / transparent plastic sheet.
5. After a bout 1 month from propagation, the bud will emerged by itself from the parafilm, so there is no need to remove the parafilm wrap.
Training
For asexually propagated seedlings, maintain only single stem. Allow the scion to branch only after it reaches high from the bud union. If the scion branches before it reaches 1 ft, the branches may pose a problem (especially for lemon). When they are already grown in the orchard the lower branches may reach the ground especially when laden with fruit. For some mandarin varieties, it may be necessary to stake the budlings to straighten the scion.
After the bud has grown several inches, the rootstock top can be removed completely by making a slanting cut (high end on the same side as the bud) about 1 cm (1/2 in) above the bud.
As the bud grows, stake and tie it at regular intervals to prevent breakage. Remove all other buds and suckers from the rootstocks as they appear.
Source: FARM PRIMER, PCARRD, BNCRDG-BPI, HARRDEC, BSU