Weed by hand frequently or with a hoe, working shallowly to prevent damage to roots.
Fertilizing a young and growing orchard
Maintaining a good fertilization program can keep trees vigorous and help prevent infections of bacterial blast or canker, oak root fungus, and powdery mildew. Mineral nutrients are classified as macronutrients and micronutrients. The term ‘’macronutrients” refers to those elements that plants require in large amounts (N, P, K, Ca, Mg, S). The term “micronutrients” (or “trace elements”) applies to plant nutrients that are essential to plants but are needed only in small amounts [Fe, Zn, Mn, B, Cu, Mo, Ni (nickel), Cl (chlorine)]. Visual deficiency symptoms of N, P, K, Ca, Mg, Fe, Zn, Mn, B, Cu, and Mo (nitrogen, phosphorus, potassium, calcium, magnesium, iron, zinc, manganese, boron, copper and molybdenum) can usually be recognized by distinctive symptoms that most often occur in the leaves, but can sometimes be seen in the fruit, branches, or general growth of the tree. The most common deficiency symptoms found in apricot are nitrogen and zinc.
Types of fertilizer to use: Generally, only two types of commercial fertilizers are required: a balanced fertilizer (8-8-8, 13-13-13), and a nitrogen fertilizer such as ammonium nitrate (33-0-0), or ammonium sulfate (21-0-0). Urea (46-0-0) is a good source of nitrogen. The balanced or complete fertilizer contains nitrogen, phosphorous, and potassium, the elements needed in the largest amounts by apricot trees. The nitrogen fertilizer stimulates vegetative growth later in the year. The numbers 8-8-8 or 13-13-13 represent the percentage of nitrogen-phosphorus-potassium the fertilizer has. DAP is diammonium phosphate (18-46-0). If soil pH is above 6.5, use ammonium sulfate (21-0-0) as the nitrogen source as it helps acidify the soil. If soil pH is 6.5 or below, use another source of nitrogen. If soil pH is above 7.5, do not apply phosphorus fertilizer. Do not ever apply sulfur directly to apricot trees.
Scatter fertilizer under the spread of branches and just beyond the dripline of the outermost branches. To prevent fertilizer burn, do not apply fertilizer closer to the trunk than 20 cm. You may apply fertilizer any time from late fall to early spring. Water thoroughly to carry the nitrogen down into the root zone. Remove competition for nutrients and water by keeping the ground bare under the tree using shallow cultivation, herbicides, or organic mulches.
Don’t apply excessive amounts of fertilizer. Too much nitrogen causes excessive branch growth, inhibits fruit set, causes poor fruit color and flavor, delays ripening and may subject the tree to more severe winter injury. Also, late application of nitrogen, after mid July, can prevent the proper “hardening off” of the tree for winter dormancy.
Fertilizing apricot trees that are 3 years and older
Nitrogen should be applied annually, usually during the growing season. To improvefruit quality and color, nitrogen levels should be low but not deficient as the harvest nears. Excessive nitrogen can cause softer fruit, poor fruit color, and reduced storage and shelf life; it can also increase problems with numerous pests. Apply well away from the trunk and water thoroughly after application. Apply half to two-thirds of the fertilizer in autumn and the rest in spring. Rates for different nitrogen sources per tree per year year (use only 1 of these): 1.4 to 2.3 kg of ammonium sulfate, 1 kg of urea, 2 to 3 kg ammonium nitrate, Well-rotted animal manure (e.g. poultry manure 20 to 30 kg per tree)
3 year-old tree: Apply a fertilizer containing potassium, such as muriate of potash (1 to 2 kg per tree) or a mixed N:P:K fertilizer (4 to 8 kg per tree depending on the potassium (K) content). 4th year and older: Halve these rates.
Dig in 10 kg of superphosphate (20 kg for trees six years and older) around the tree. Do not repeat this. OR: Use three to five leaf sprays of 0.5% (5 g per liter) of monosodium phosphate, plus a wetting agent.
If trees show symptoms of Magnesium deficiency, do not apply any potassium fertilizer. Increase the amount of nitrogen fertilizer. Apply magnesium carbonate or a lime containing magnesium to tree. Spray leaves two or three times with 1% (10g per litre) magnesium nitrate or 2% magnesium sulphate plus a wetting agent.
Apply two or three foliar sprays containing 0.25% (2.5 g per litre) of manganese sulphate, plus a wetting agent.
Spray with a “chelated zinc” during the growing season. Repeat if new growth still shows deficiency symptoms. Soil applications are not very effective because the roots of fruit crops occupy deep soil layers and zinc does not easily move in the soil. Although foliar sprays are more effective, foliar-absorbed Zn is not easily translocated in plants, which necessitates repeated spray applications and diminishes the ability of foliar sprays to alleviate Zn deficiency in all plant parts.
Recognizing nutrient deficiencies
If nitrogen is deficient, older lower leaves of fruit trees may become yellow, terminal shoot growth is reduced, and fruit yields decline since the tree may not set or carry much fruit. If nitrogen is excessive, vegetative growth may be lush, but fruit set may be reduced and fruit maturity delayed by 7 to 10 days. Therefore, either an excess or deficiency of nitrogen should be avoided. Yellow leaves of new growth usually indicate iron or zinc deficiency, and in severe cases the entire tree may be yellow. Leaves are small, narrow, closely spaced and mottled with yellow, especially new leaves. Lateral leaf buds may fail to grow. Affected trees have small new leaves. Iron deficiency appears as yellowing between major veins of the leaf. Other deficiencies are uncommon.
Regular irrigation is needed to grow tree fruit. Uniform soil moisture is important in maintaining tree vigor, productivity, and fruit size. It is especially important to provide the tree with adequate water during the first year after planting to help develop a good root system. Irrigate from the onset of growth in the spring through the growing season after harvest. Avoid frequent shallow irrigation. Frequent, light watering encourages a shallow root system and can cause the development of wood rot which attacks the trunks and roots, killing the tree. Less frequent and deeper watering is preferable. Irrigate your trees with a deep soaking every 7 to 15 days, depending on the season and weather. It may be helpful to make a depression or basin around trees to collect water and aid in summer irrigation. However, excessive irrigation or excessive precipitation can create a problem with rot around the trunk collar. It is also important to level the soil surrounding the tree in the fall. This prevents water from collecting and freezing around the trunk during the winter and causing injury to the tree. Surface irrigation by furrows and flooding (Gravity flow): Furrows should be filled with water and then drained, to ensure that the entire root system receives a sufficient amount of water. Border berms can be used to contain the water for a 1 to 2 day period for adequate absorption. Berms should then be removed until the next watering. Soil-based Scheduling Methods (How to know when to water): Irrigation should bedone when about 50% of the water has been depleted from the soil. To check the water content in the soil, take a trowel, shovel, or soil tube and dig down 20 to 40 cm. A soil that has about 50% available water will feel as follows:
coarse – appears almost dry, will form a ball that does not hold shape; loamy – forms a ball, somewhat moldable, will form a weak ribbon when squeezed between fingers, dark color; clayey – forms a good ball, makes a ribbon an inch or so long, dark color, slightly sticky. Mulches are beneficial to young fruit trees. Mulches of any plant material, such as shredded bark, grass clippings, straw, or sawdust conserve soil moisture, moderate extreme soil temperatures, and help reduce competition from weeds and turf. Apply a mulch 10 to 15 cm deep, but keep the mulch several inches away from the trunk. In early fall, remove the mulch. This lets the roots know that temperatures are getting cooler and winter is on its way. The tree will begin to harden off or get physiologically ready for winter. Removing the mulch also prevents mice and other rodents from hiding in the mulch and chewing off the bark during the winter.
When all factors are favorable trees can set too many fruit. An overabundance of fruit on a tree may weaken it and result in fewer buds, leading to a smaller crop for the next season. A heavy crop also can result in small-sized fruit of poor quality. To avoid these problems, thin trees two to three weeks after bloom. Remove all but the largest fruit in each cluster. Remove small, insect- or disease-injured fruit first and follow recommended average spacing distances. Fruit should be spaced by 7 to 10 cm apart Young orchard under flood irrigation Flood irrigation contained by border berms on each branch, with small branches having only 1 or 2 fruit. Thinning should be done to allow a closer spacing near the base of the branch and a wider spacing near the tip of the branch. This is done to avoid the branch bending or breaking off from too much weight at the tip.