Previously this week, I wrote an article discussing nitrogen needs within the almond orchard. Application of nitrogen, as briefly discussed, varies in efficiency based upon techniques of application and irrigation/fertigation systems. Below are some tips to maximize efficiency and reduce losses for many common fertilizer application strategies.
Maximize Efficiency:
1. Apply N only when leaves are present and the tree roots are active. Avoid dormant season applications.
2. Efficiency can be increased by applying N in small doses more frequently than large doses less frequently.
3. Apply a uniform irrigation that is adequate to carry the N into but not past the root zone.
4. Because young fruit trees have a fairly constant N uptake, apply multiple applications of N throughout the growing season.
5. Mature trees need most of the N in the spring, around 70-75% of the nitrogen budget.
6. Late summer/postharvest applications, 25-30% of the budget,will help with flower bud differentiation and formation for next year's crop.
7. Fertigation has generally been very efficient in N applications.
8. Analyze leaves in July each year to fine tune N level to the orchard. Maintain the level in the adequate range.
Minimize Losses:
1. If fertilizer is surface applied, disc or irrigate N into the root zone shortly after application.
2. Fertilize the tree, not the covercrop. Evaluate how best to bypass the covercrop. This may be by applying the fertilizer to the herbicide sprayed strip, mowing, or cultivating the covercrop.
3. Don't over irrigate. Nitrogen is soluble and moves with water. Excessive runoff of tail water or leaching will remove N.
Thursday, April 29, 2010
Monday, April 26, 2010
Nitrogen Use of Almonds
David Doll, Farm Advisor, UCCE Merced
Nitrogen is considered a major or essential element of plant growth.It is necessary for proper leaf development, fruit development and growth, and to renew and invigorate fruit wood. As trees come into production, their need for nitrogen increases due to the physiological processes involved in fruit development, foliage formation, and the formation of tree reserves. Meeting the tree’s demand for nitrogen during these processes is critical since a shortage of this element can reduce yields.
Previous research has shown that most of the nitrogen applied to an orchard becomes part of the hull, shell, and kernel. Therefore, by estimating the crop load of the coming growing season, we can determine the tree’s need for nitrogen. The nitrogen used in the almond crop (hulls, shells, and kernals) is about equivalent to 5% of the kernal pounds per acre yield. For example, a 3000 kernal pound yield uses about 150 pounds of nitrogen. Applications of just 150 pounds, however, will not replace the nitrogen lost to the crop due to inefficiencies of nitrogen delivery. Generally speaking, multi-application fertigation programs are the most efficient (around 80%), while one, large broadcast application is least efficient (around 50%). Tips for increasing efficiency will be included in another entry.
To help estimate nitrogen needs and budget, a new nutrient model has been developed at UC Davis by Dr. Patrick Brown and colleagues. This model, taking into account yields, July leaf sample analysis, and point sources of nitrogen which include manure, nitrate in the groundwater, and soil, can predict the needed amount of nitrogen needed for the coming year. Nitrogen application rate estimates are based on reaching the optimal levels of leaf nitrogen content (2.2-2.5%). Furthermore, annual potassium applications applied can also be calculated. This model can be found here.
Nitrogen is considered a major or essential element of plant growth.It is necessary for proper leaf development, fruit development and growth, and to renew and invigorate fruit wood. As trees come into production, their need for nitrogen increases due to the physiological processes involved in fruit development, foliage formation, and the formation of tree reserves. Meeting the tree’s demand for nitrogen during these processes is critical since a shortage of this element can reduce yields.
Previous research has shown that most of the nitrogen applied to an orchard becomes part of the hull, shell, and kernel. Therefore, by estimating the crop load of the coming growing season, we can determine the tree’s need for nitrogen. The nitrogen used in the almond crop (hulls, shells, and kernals) is about equivalent to 5% of the kernal pounds per acre yield. For example, a 3000 kernal pound yield uses about 150 pounds of nitrogen. Applications of just 150 pounds, however, will not replace the nitrogen lost to the crop due to inefficiencies of nitrogen delivery. Generally speaking, multi-application fertigation programs are the most efficient (around 80%), while one, large broadcast application is least efficient (around 50%). Tips for increasing efficiency will be included in another entry.
To help estimate nitrogen needs and budget, a new nutrient model has been developed at UC Davis by Dr. Patrick Brown and colleagues. This model, taking into account yields, July leaf sample analysis, and point sources of nitrogen which include manure, nitrate in the groundwater, and soil, can predict the needed amount of nitrogen needed for the coming year. Nitrogen application rate estimates are based on reaching the optimal levels of leaf nitrogen content (2.2-2.5%). Furthermore, annual potassium applications applied can also be calculated. This model can be found here.
Monday, April 19, 2010
SIlver Leaf of Almond - Another heart-wood rotter
Silver leaf is a fungal disease of the xylem tissues of many various species of fruit trees. Caused by t he fungus Chondrostereum purpureum, it is commonly found in riparian areas containing hardwood trees such as willows, poplar, birch, and oaks.
Figure 1: Padre leaves showing symptoms of silverleaf (left) versus leaves from a healthy Padre tree (right).
A farm call this week brought me to an orchard showing signs of silver leaf infection. Silver leaf is so named because of its ability to make laves appear silver in color (Figures 1 and 2). This appearance is due to a toxin produced by the fungus that is carried through the xylem to the leaves. Once within the leaves, it creates a separation between the epidermis and palisade layer, creating an air gap that interferes with the normal interception of light. As the disease progresses, leaves curl upward at the edges and turn brown (Figure 3). Scaffolds will eventually collapse, shortly followed by tree death.
Figure 2: Close up comparison of a Padre leaf showing symptoms of silverleaf (left) versus a healthy leaf (Right).
Irregular cankers found within the xylem tissue of dead and/or dying branches is another characteristic symptom of the disease (Figure 4). In later stages of tree decline, spore-bearing conks or shelf like mushrooms form in the fall. Generally found on the north side, these mushrooms are gray to white in appearance and have a smooth, purplish lower surface. The spores from the mushrooms can infect neighboring trees, and are released upon rain events. Exited spores are moved by the wind and the mushrooms can produce spores for 2 years.
Figure 3: Severe infections of silverleaf are characterized by curled leaves and necrotic margins.
Wounds with exposed xylem or sapwood or vulnerable to infection. This includes pruning wound cuts, growth cracks, wind cracks, or growth inclusions that have not healed completely over. The most commonly affected variety is Padre, followed by Butte. Any age of tree can become infected, but trees between the ages of 3-5 are most commonly observed with the disease. This may be due to the amount of pruning cuts made to train the young tree. It can take up to 2 years after infection for symptoms to become obvious.
To prevent the infection of trees, tree injury should be avoided - especially during rainy periods. Avoid excessive pruning or removal of large branches that require a long time to heal. If cuts need to be made, make them as early in the fall as possible to avoid having susceptible wounds during the rainy period. Cuts made to trees in spring, summer, or fall can take one to several weeks to heal, while cuts made in the winter may take longer. In areas of high disease pressure, applications of the biocontrol fungus Trichoderma harzianum can be made to pruning cuts to help prevent infection by the silverleaf pathogen.
Figure 4: Cross section of a tree infected with silverleaf shows a distinctive ireegular shaped canker within the heartwood.
There is no way to cure a tree affected by silverleaf. Affected trees should be removed and burned before the conks form in the fall. Furthermore, try to remove as many roots as possible upon replanting. Once one tree is found within the orchard, there usually are a few more. Be sure to scout the orchard for other diseased trees.
Figure 1: Padre leaves showing symptoms of silverleaf (left) versus leaves from a healthy Padre tree (right).
A farm call this week brought me to an orchard showing signs of silver leaf infection. Silver leaf is so named because of its ability to make laves appear silver in color (Figures 1 and 2). This appearance is due to a toxin produced by the fungus that is carried through the xylem to the leaves. Once within the leaves, it creates a separation between the epidermis and palisade layer, creating an air gap that interferes with the normal interception of light. As the disease progresses, leaves curl upward at the edges and turn brown (Figure 3). Scaffolds will eventually collapse, shortly followed by tree death.
Figure 2: Close up comparison of a Padre leaf showing symptoms of silverleaf (left) versus a healthy leaf (Right).
Irregular cankers found within the xylem tissue of dead and/or dying branches is another characteristic symptom of the disease (Figure 4). In later stages of tree decline, spore-bearing conks or shelf like mushrooms form in the fall. Generally found on the north side, these mushrooms are gray to white in appearance and have a smooth, purplish lower surface. The spores from the mushrooms can infect neighboring trees, and are released upon rain events. Exited spores are moved by the wind and the mushrooms can produce spores for 2 years.
Figure 3: Severe infections of silverleaf are characterized by curled leaves and necrotic margins.
Wounds with exposed xylem or sapwood or vulnerable to infection. This includes pruning wound cuts, growth cracks, wind cracks, or growth inclusions that have not healed completely over. The most commonly affected variety is Padre, followed by Butte. Any age of tree can become infected, but trees between the ages of 3-5 are most commonly observed with the disease. This may be due to the amount of pruning cuts made to train the young tree. It can take up to 2 years after infection for symptoms to become obvious.
To prevent the infection of trees, tree injury should be avoided - especially during rainy periods. Avoid excessive pruning or removal of large branches that require a long time to heal. If cuts need to be made, make them as early in the fall as possible to avoid having susceptible wounds during the rainy period. Cuts made to trees in spring, summer, or fall can take one to several weeks to heal, while cuts made in the winter may take longer. In areas of high disease pressure, applications of the biocontrol fungus Trichoderma harzianum can be made to pruning cuts to help prevent infection by the silverleaf pathogen.
Figure 4: Cross section of a tree infected with silverleaf shows a distinctive ireegular shaped canker within the heartwood.
There is no way to cure a tree affected by silverleaf. Affected trees should be removed and burned before the conks form in the fall. Furthermore, try to remove as many roots as possible upon replanting. Once one tree is found within the orchard, there usually are a few more. Be sure to scout the orchard for other diseased trees.
Wednesday, April 14, 2010
Monday, April 12, 2010
Glyphosate Damage on Almond
A number of calls have came in in regards to glyphosate drift damage. Drift injury from fall applications of the herbicide glyphosate (Trade names Roundup, Rodeo, Touchdown, Ranger, etc.)often appear the following spring upon the first flush of growth. The growth response from glyphosate application is very unique, with the overall tree appearing yellow (Figure 1 and 2) with deformed leaves having a "boot-lace" appearance (Figure 2), bud and limb death (Figure 3), and in severe cases, tree death.
Figures 1 and 2: Almond trees showing symptoms of exposure to glyphosate. Most likely, the herbicide drifted onto the tree in the fall, with symptoms appearing the following spring.
Many growers ask how a fall application of herbicide can still cause damage the following spring. Glyphosate, being a systemic herbicide, is designed to be stable once inside the plant. When glyphosate is applied to the leaves of a weed, the chemical is able to move through the leaf cuticle and enter into the phloem of the plant. From this point, it is translocated to the root, or other tissues, exits the phloem and inhibits the formation of amino acids that are critical for plant growth, killing the plant. If, however, glyphosate is applied to a woody plant (i.e. tree) entering dormancy, the chemical may not be systemically translocated, but "stuck" in the phloem tissue within the area of application. Once the plant breaks dormancy, the flow of carbohydrates from root to shoot move the herbicide into the newly formed tissues, causing deformed growth and possibly bud and shoot death.
Figure 3: "Boot Lace" appearance of almond leaves is often indicative of glyphosate exposure.
Figure 4: Dieback of the apical bud of a young almond shoot caused by the accidental application of glyphosate.
Glyphosate damage is often confused with zinc deficiency. If a tree is zinc deficient, the leaf symptoms will worsen, while a glyphosate damaged tree will slowly recover (if not killed!). A previous blog discussed the varying possibilities of glyphosate and zinc deficiency in almond trees.
If symptoms similar to the pictures above appear in your orchard, be sure to apply herbicides with care in order to prevent herbicide drift. Drift injury can be prevented by following precautions mentioned on the label of the herbicide used, avoiding applications during windy weather, and using proper pressures, rates, and maintained equipment. More information in regards to herbicide drift prevention can be found in a previous entry.
Figures 1 and 2: Almond trees showing symptoms of exposure to glyphosate. Most likely, the herbicide drifted onto the tree in the fall, with symptoms appearing the following spring.
Many growers ask how a fall application of herbicide can still cause damage the following spring. Glyphosate, being a systemic herbicide, is designed to be stable once inside the plant. When glyphosate is applied to the leaves of a weed, the chemical is able to move through the leaf cuticle and enter into the phloem of the plant. From this point, it is translocated to the root, or other tissues, exits the phloem and inhibits the formation of amino acids that are critical for plant growth, killing the plant. If, however, glyphosate is applied to a woody plant (i.e. tree) entering dormancy, the chemical may not be systemically translocated, but "stuck" in the phloem tissue within the area of application. Once the plant breaks dormancy, the flow of carbohydrates from root to shoot move the herbicide into the newly formed tissues, causing deformed growth and possibly bud and shoot death.
Glyphosate damage is often confused with zinc deficiency. If a tree is zinc deficient, the leaf symptoms will worsen, while a glyphosate damaged tree will slowly recover (if not killed!). A previous blog discussed the varying possibilities of glyphosate and zinc deficiency in almond trees.
If symptoms similar to the pictures above appear in your orchard, be sure to apply herbicides with care in order to prevent herbicide drift. Drift injury can be prevented by following precautions mentioned on the label of the herbicide used, avoiding applications during windy weather, and using proper pressures, rates, and maintained equipment. More information in regards to herbicide drift prevention can be found in a previous entry.
Wednesday, April 7, 2010
Monday, April 5, 2010
Almond Leaf Rust - Treat now to prevent late season defoliation
Prevention: Orchards favoring high humidity often have rust problems. Encouraging air movement by planting on wider spacings (22' between rows), hedging, or selective pruning may help reduce canopy humidity. Microsprinklers and solid set sprinklers may increase canopy humidity since evaporation of sprayed water may occur. Sanitation (leaf mowing, breakdown) should be employed to reduce overwintering inoculum.
Treatment: In orchards that have a history of rust, a two spray fungicide program should be used to reduce disease and clean up the orchard. The first application should be applied 5 weeks after petal fall and followed up with a 2nd application at 10 weeks post petal fall. DMI (FRAC Group 3) or strobilurins (FRAC Group 11) provide good to excellent control. Broad spectrum fungicides such as sulfur and topsin provide a good, cheap control and also allow an option for fungicide rotation. More information on fungicide efficacy can be found here.
Applications of zinc sulfate (20-40 lbs/acre) applied in late October/early November should be made to help reduce overwintering populations of rust. The zinc will hasten leaf fall, and prevent the rust inoculum from increasing. In orchards of severe infestation, applying a low rate of nitrogen to the surface leaf debris will help speed up the natural degradation of the leaves. A similar treatment is used to reduce overwintering populations of apple scab in Michigan.
Subscribe to:
Posts (Atom)