FAQs

Question:

We live up in the mountains and have many oaks on our property. We have noticed brown growths near the end of branches that looks as if someone had thrown cow manure into the trees and it stuck! Also, we have some round balls" hanging from the oak trees as well as some growths that are near the end of young twigs that look to be impaled on the twigs. What are these and where do they come from?"

Answer

Wherever oaks occur, they are attacked by a small group of insects called galls makers. These insects cause deformities of plant tissue. The majority of gall making insects that attack oaks are wasps. Galls are produced by powerful plant growth-regulating chemicals or other stimuli produced by the insect that react with plant hormones. Some stimuli are feeding or egg laying. The inner walls of the galls are rich in protein and thus provide the larvae living in the gall a concentrated food source. The larvae are somewhat protected from predators while they are in the galls. Galls come in several shapes and sizes. They can be globular, dish-shaped or look like thorny, spiny balls. Galls are specific as to the kind of oak they occur on. For example, those found on the black oak group do not occur on the white oak group. Many galls exhibit a characteristic gall alternation of generations. That is that the offspring of a gall wasp may produce galls that are completely different from those produced by their parents, but identical with those by their grandparents. Also, the site of the galls usually will be produced on a different part of the tree than those of their parents. It is reported that 717 species of gall wasp are found in North America. That number is decreasing as biologists unravel the mystery of alternating generations pairs and identify single species.

Source

Insects That Feed on Trees and Shrubs, 2nd Edition. Warren T. Johnson and Howard H. Lyon. 1991. Page 440.

Question:

I have some juniper trees whose tips are turning brown. The trees were planted over 20 years ago and they receive enough water. When the branches are moving a yellow powder falls out of the infected" area. What is causing the browning of the tips. Is it an insect or a fungus of some kind?"

Answer

After examining a sample of the plant it was determined to have normal growth. The small brown tips are the developing male portion of the trees and when mature will produce pollen. The yellow power that falls off the plant when disturbed is indeed pollen.

Question:

The cottonwood in our back yard has several limbs that are dying in the center of the tree. It is growing in a fescue lawn. What is causing this to happen?

Answer

Cottonwood trees are native to rivers, streams and washes in Arizona. They require a lot of water. You need to water the lawn and then deep soak for the cottonwood tree. If you water shade trees with only the 1 to 2 inches of week per water required by the lawn you will not supply the 3 to 6 inches of water per week that large trees will need. This is because lawn roots are primarily in the first foot of soil. The majority of tree and shrub roots will be in the top two to three feet of soil. During the hot summer weather trees will extract large amounts of water from the soil each day. Shallow watered tree roots will tend to be closer to the surface of the ground. However, the genetics of the tree has a lot to do with the depth of rooting. I have known of several cases where the tree roots where growing up to the soil surface and the owners cut the roots out so they would not have to run over them with the lawn mower. By doing this you sever the roots that uptake nutrients and water to specific limbs of the tree causing them to die.

Question:

How much fertilizer do shade trees need, what kind is the best, and when should it be applied?

Answer

Ornamental trees and shrubs planted in fertile, well drained soil that are growing normally do not need extra nutrients. If they are not doing well fertilization may be helpful but only after the problem causing poor growth is corrected. Symptoms of poor growth may be light green or yellow leaves; smaller and/or fewer than normal leaves or dead spots; wilting of foliage; few flowers; short annual twig growth; and branch tip die back. These symptoms of poor growth may be caused by poor environmental situations like: inadequate soil aeration and moisture, or nutrition; adverse climatic conditions; wrong pH; or insects and diseases. Normally the only nutrient applied to established trees and shrubs in nitrogen. Other situations like chlorotic leaves, manifested by yellowing of leaves but veins remain green, require specific applications of a nutrient, in this case iron. The amount of nitrogen needed will depend on the size of the plant. Measure the diameter of the trunk about one foot from the ground. Apply 0.05 pounds of actual nitrogen/inch of trunk diameter. If a tree has a trunk diameter of six inches multiply by 0.05 to get 0.3 pounds of actual nitrogen. Divide the amount of nitrogen by the percentage of nitrogen content of the fertilizer to be applied. For example: 0.3 pounds of nitrogen applied as 21% ammonium sulfate would be: 0.3/21% = 1.43 pounds of ammonium sulfate fertilizer from the bag. Distribute the fertilizer evenly by measuring the distance between the trunk and drip line and multiply by 125%. This will determine the outer boundary radius for fertilizer application. Distribute the fertilizer evenly in the outer 2/3 of this circle. For example: If the trunk is eight feet from the drip line, then the outer boundary will be ten feet, (8 X 125% = 10). Apply fertilizer around the tree or shrub in a doughnut shaped band this 3.3 feet to 10 feet from the trunk, (10/3 = 3.3). Applications are best applied from early spring.

Question:

I have several trees, shrubs and bushes that have leaves that are turning yellow but the veins remain green. I water them every other day and feel that they are receiving enough water. What can I do to correct this problem?

Answer

The leaf yellowing is called iron chlorosis and is caused by insufficent iron in the plant leaves. If you look closely you will see that the older leaves are not effected. Iron is necessary in the formation of chlorophyll, the green pigment of plant leaves and stems. Our soils are alkaline, meaning that they have pH's above 7.0. As soil pH increases above 7 iron forms other molecular complexes which are not taken up by plants. Water logged soils or anarobic conditions can cause iron to be unavailable.

Control

Decrease the amount of water given plants, checking the soil to see if watering is necessary. Lowering soil pH will make iron more available. Changing soil pH is a long term proposition but can be accomplished by adding acidifing materials such as soil sulfur and/or gypsum. Iron can be applied to the soil or the leaves to help correct this problem. Iron applied to the soil is slower acting but is longer lasting than iron sprayed on the foliage. There are several dry products that can be soil applied; these include Ironite", iron sulfate and other forms of iron. These products are poured into holes that are about poked into the soil one to one and a half feet deep, placed around the drip line of the affected plant and serves as a reservoir of available iron. Foliar applied irons are usually liquids and can also come in chelated forms. Chelates are "chemical jaws" which protect the iron from becoming bound up with other chemicals before it is inside the plant. Once near or inside the plant the chelating agent is dissolved and the chelated chemical is available. Chelates can be applied to the soil also but only Sequestrene 138, (6% iron), will work well in our alkaline soils. It is red in color as a powder and when added to water has the color of blood and is expensive as blood! The Sequestrene 330, (10% iron), is yellow in color and is applied to the foliage only. It should only be soil applied to acid soil, if not it will become bound up and not available to the plant. Look at the product color to know which chelated iron is being used and how to properly apply it. Always read and understand the label before using chemicals."

Question:

My mesquite tree has mistletoe in it. Is there any way to rid my trees of this growth?

Answer

There are several genera and species of mistletoe. In Arizona we have 5 species of Phoradendron (leafy mistletoes) and 3 species of Arceuthobium. The latter, called dwarf mistletoe, infests only conifers. Leafy mistletoes are considered as hemi-parasites, which means that they produce some or all of their own energy through photosynthesis but depend on the host for water and minerals. Mistletoes elicit a disease response from most hosts and are considered pathogens. However, mistletoes seldom kill healthy hosts except dwarf mistletoe, which can cause severe damage in coniferous forests. Severely infested trees usually have been subjected to other stresses that increased their susceptibility such as drought, flooding, soil compaction, nutrient deficiencies, etc.

The "root" of a leafy mistletoe is directly connected to the host's xylem (that part of the plant's plumbing that conducts water and minerals from the roots to the leaves). The "root" of a dwarf mistletoe is connected to the host's phloem as well as the xylem. The phloem conducts sugars and other products of photosynthesis from the leaves to other parts of the plant. So the dwarf mistletoe is highly parasitic, depending on the host, for photosynthate as well as water and minerals.

Leafy mistletoes can occur on several hundred host species. Mistletoe creates a drain on host resources that reduce growth, decreases vigor, and increases susceptibility to other diseases and insect pests. Local symptoms can include dieback, formation of witches' broom, and weakened branches. Dwarf mistletoe, in particular, can cause spiketop, where the entire host crown dies and also causes witches' broom which increases the diversion of water, minerals, and nutrients to the site of infestation.

Control

Removal of the branch below the mistletoe remains an economical and fairly efficient method of mistletoe control. However, control by pruning requires diligence. Birds eat mistletoe berries and spread the seed which is unaffected by the digestive tract. So any fruiting mistletoe that survives pruning is a source for reinfestation. Chemical treatment has not been effective to date. In one study 2,4-D was injected in infected eucalyptus trees. The chemical killed 70% to 100% of the mistletoes, but partially defoliated all trees and killed 5% of them.

Recent research efforts have focused on interrupting fruit set with hormone sprays combined with pruning. Resistant cultivars and biological control remain as possible long term solutions.

Wrapping the mistletoe and infected branch with black plastic to block light and increasing heat has proven somewhat effective. The plastic must remain around the branch for several months.

Source

Paine & Harrison. 1992. HortTechnology 2:34-330.

Question:

My mesquite trees have brown round bumps on many of the limbs. In fact some of the branches have ooze dripping from them. Is this scale?

Answer

Yes the problem is scale, soft brown scale in fact. Scale are a super family" of over 200 insects that feed on plant sap while females protect themselves with a soft or hard "shell" body covering. Males can be winged. Scale produce young by eggs or by bearing live young. The young, called crawlers, may crawl out from under mother's covering and move to another location, usually close by, and then set up "housekeeping". One to five generations will be produced each year depending on the species and environmental conditions. Scale are protected by the covering they make for themselves and it is very hard to penetrate with pesticides."

Control

Physical removal by spraying a hard stream of water may work, however many times they are stuck on the plant very tightly. Even rubbing off the scale with a stiff brush can be effective. Using systemic insecticides can help control scaled but many times does not work very well. Suffocating or penetrating their shell" are methods also used to kill this pest. Dormant oil sprays are used when plant leaves are no longer than a half inch in early spring. If used later leaf damage may occur. Rubbing alcohol applied to scale will penetrate their waxy shell covering and kill them. Use 70% isopropyl (rubbing) alcohol, mixing 1 to 2 cups of alcohol per quart of water. Since alcohol can damage some plants first test spray on a small area. Wait for a day or two to see if damage occurred, if not it is safe to spray. You can mix insecticidal soap up according to the label directions but substitute rubbing alcohol for half of the water. A recipe a that has proven effective in the past for scale control and other insects is made by mixing one cup cooking oil plus 1 Tablespoon of dish detergent (non-citrus). Mix one to two teaspoons of this solution with one cup of water. Spray mixture on the infected plant until it drips off. It is best to spray a few leaves and then check for leaf burn the next day before spraying the entire plant. With many of these treatments the scale will not drop off of the plant but will remain attached even though they are dead. Pry some off several days after treatment to determine if the scale are dead. If not treat again."

Question:

I have several 12 year old Arizona cypress trees with needles that are turning brown. The middle to center of the limbs on the lower branches are affected. What disease is causing this? What can I do about it?

Answer

As evergreen trees get older the leaves, called needles or scales, on older branches, (those that are close to the tree trunk or base of the tree), will naturally brown and fall off. These leaves are old having served the tree well but have become shaded out and are not contributing to the tree's growth. During normal winters adequate moisture falls. This winter however was unusually dry. Because of little or no moisture supplemental water was necessary. Several people have called with questions about browning evergreens. Usually people will state that they did not water their trees last winter. Evergreens need about one third the of water during the winter compared to the rest of the year. Therefore, water the trees and watch for new growth. The tips of the branches should be green and healthy because that is where shoot growth takes place. Also, water at the tree drip line and out from that point. Feeder roots are located usually out from the drip line not next to the tree trunk. I trees are planted through plastic that has crushed granite or gravel on top, take a pitch-fork and poke holes through the plastic to allow rain fall into the soil.

Question:

I have several Arizona Cypress trees that are dying. There are holes in the trunks and the tips are breaking off. What is happening to my tree?

Answer

The problems observed on your tree are two different insects. Both are aggressive pests of stressed cypress and junipers on Arizona. The first is Western Cedar Borer. This borer will attack and seriously injure or kill trees. It seems to prefer older, large trees. Adults are bright emerald with serial dark areas on the wing covers. Flatheaded larvae bore from the branches into the main trunk where they feed on the heartwood for several years.

The second insect is the Juniper Twig Pruner. It causes dieback on the tips of tree branches. The insect is a small long-nosed beetle. The adult has a reddish-orange head and brownish to black body. Eggs are laid on the branches, often near an intersection of twigs, one to two feet from the branch tip. Larvae are small, white, cylindrical, legless grubs that kill the twigs by boring though the centers. The life cycle may take as long as two years to complete.

Control

No practical controls or preventive measures have been developed for Western Cedar Borer or Juniper Twig Pruner. The Juniper Twig Pruner damage can be unsightly when populations are high but this pest rarely seriously injures trees. However, the Western Cedar Borer will kill trees.

Question:

I have a 'Globe Willow' that has a dark-colored sap running down the bark. I seem to be coming from under the wood near the crotch of the tree. What is the cause of this? I see some insects in this sap. Is there a bore causing the damage? The dark sap is dripping on my patio and discoloring the flagstones. What can I do?

Answer

Your tree is suffering from a disorder called slime flux or wet wood. These two diseases are thought to be bacterial infections, however these diseases are poorly understood. The water soaked, discolored appearance with constant bleeding of the sap at or below the branch crotches and trunk are the visual symptoms of this disease. Liquid may seep out of cracks or wounds and run down the bark. The liquid contains microorganisms that will cause the liquid to ferment and become dark in color, sticky and smelly and some insects may feed on it. Pressure can build up under the bark from fermentation and cause splitting and cracking. Normally the disease is not observed in young trees probably because of rapid growth which makes invasion of bacteria and fungi rare. Generally trees are at least 5 years old and have developed heartwood become infected. Wilting and die back of branches may occur. Younger trees may have leaves that yellow, wilt or curl, turn colors and then drop early. Susceptible trees grown in Arizona include: ash, (Fraxinus species), elms (Ulmus species), poplars (Populus species), willows (Salix species), mulberry (Morus species), and mesquite; common, honey and chilean (Prosopis species).

Control

Slime flux infection can aggravate wounds and cause death of bark cambium. This disease may need to be controlled in large specimen trees. Holes may be drilled to relieve pressure under the bark. Drill a 1/4 or 1/2 inch hole at an upward angle below the bleeding and insert a plastic tube snugly and permanently into the first inch or two of the hole. This reduces the internal pressure and facilitates drainage of the fermented toxic material. Remove any dead or weak branches. Fertilize and water to keep the tree in a vigorous state. For the stains on your flagstone place a piece of cardboard or plastic to catch the dark liquid. If the stone is stained perhaps bleaching would help.

Question:

I have a young spruce tree that is drying up on one side. The needles are falling off and part of the tree is bare. The tree is watered well. The tree is planted three feet from the northwest side of the house. What is the problem?

Answer

The tree is probably infected with spider mites. This can be determined by placing a white piece of paper under a branch while giving the branch a quick tap. Spider mites will be dislodged, fall on the paper and look like little speck running around. These animals are not insects but arachnids, members of the spider family. With a magnifying glass you can see that these tiny creatures have two body parts: a head and a abdomen, and eight legs. There are numerous species of mites, both harmful and beneficial. Spider mites thrive in hot, dry weather. Trees planted to close to a house will try and push the house over! Also the afternoon sun reflects heat off of the house on to the tree and provides a perfect environment for mites.

Control

If proper cultural practices are used predacious mites normally control harmful mites. If mites become a problem washing them off with a hard stream of water can help destroy small infestations. Dormant oil sprays applied during early spring also help keep mites in check. Dusting sulfur is labeled for mites and is an organic treatment. Care must be used when using sulfur during high temperatures because burning of plant tissue may occur. Chemical miticide are available to control sever infestations. Registered products include Kelthane (dicifol), and Omite (propargite). Always follow the label instructions when using any pesticide.

Question:

When should I prune my trees, shrubs, fruit trees, berries, grapes, and roses?

Answer

Pruning is a dwarfing, stimulating and stressful event. It's best to start most pruning January or February. However, diseased or dead limbs and root suckers can be removed at any time.

In the fall plants are slowing down and entering a dormant period. The dormant period is a physiological stage where buds cannot be forced to grow even under ideal conditions. Trees and shrubs are moving compounds from the leaves and branches and storing carbohydrates in the trunks and roots.

Pruning during fall and winter may stimulated buds that are going dormant to begin growing using energy and other resources that are normally stored to survive winter. Next spring's growth takes a lot of energy and if used up in the fall and winter because of pruning stimulation and can cause plants to become stressed and even die if winter conditions are severe.

All of this growth needs to occur in the spring before photosynthesis can begin anew in deciduous plants. Even evergreens' growing activity in the winter slows and in some cases stops. Stimulating new growth is just opposite of what the plant needs to have happen to survive the winter season. This is harmful when plants should be going "to sleep." A plant that has been pruned in late fall can be damaged or killed when it starts growing and a freeze occurs.

Pruning of pine, juniper, cedar, fir, and spruce tree and shrubs should be done during the spring. Pruning is a stressful event for nearly all plants. The mentioned conifers are not growing much if any during the winter season and will have growth start in the spring. Waiting until spring to prune or trim these plants will afford them the opportunity to heal properly because of the strength they will have during the spring push of growth.

Pruning of fruit trees should be done when trees are dormant, after rest is completed in the winter. Generally rest requirements are obtained after Christmas. Pruning can be started in January and continue through bloom in the spring. Fruit trees can be pruned until flower pedals fall. For stone fruits; i.e. apricots, almonds, cherries, peaches, plums and nectarines and for pome fruits; i.e. apples, pears and quince pruning can continue until bloom is completed.

Small fruits; i.e., blackberries, grapes, raspberries, currants and gooseberries are best pruned during the dormant season. Grapes can be pruned through bloom but have a tendency to "bleed". This is not as detrimental as one might think and it is better to prune grapes a little late than let them grow in to a knurled mass! Blackberries and raspberries bare fruit on one year old canes. The two year old canes need to be removed because they have born fruit and are dead. Thinning out weak canes can also be done through bloom. Currents and gooseberries should be dormant pruned by removing wood that is 3 years old by cutting it back to the base or to a main branch.

Roses that bloom several times during the year should be dormant pruned in the late winter or early spring before new growth begins. Roses that bloom only once during the year are pruned after blooming n late spring or summer after flowering. Roses are dormant pruned except in the case of climbing roses which are pruned after flowering.

If you have question on a specific plant's pruning requirements contact the Extension Office in Sierra Vista or Willcox or consult a good pruning book like Sunset's Pruning Book.

Question:

When my roses bloom they have brown and black petal edges and are deformed. Also the leaves are sticky. Some of the leaves are covered with yellow spots mixed with the green color of the leaves. What is causing these problems and what can I do?

Answer

Your roses have two insect problems and a virus. The flower petals are brown or black because of a very small insect called the western flower thrip, Frankliniella occidentalis (Pergande). Adult thrips are about 1/8, (2 mm), in length, usually tan-to-dark brown-bodied, with four feather like wings. The young or nymphs are creamy white and wingless and develop into adults in about two weeks. The adults enter a rose bud and lay eggs inside the immature flower. The eggs hatch and the resulting nymphs and adults injure the plant by rasping the bud, flower and leaf tissue of host plants and then suck the exuding sap. This causes petal tissue to die and results in brown or black petal edges. Thrips also affect other flower, fruit and vegetable plants. These include apples and peaches which result in surface damage to the fruit. Onions, snap beans, chrysanthemums, gladiolus and iris are also damaged by other thrips species. There has been many more thrips the last couple of years because of the above normal rainfall which has provided abundant wildflower and weed crops for the thrips to live on and thus increased populations. The other insect problem is aphids. These small insects are yellow to green in color and suck sap from plants that they infect. The "sugars" which they do not metabolize are excreted and fall onto the leaves of the plant. This is the sticky, shiney substance that you see. Sometimes ants and flies will "milk" aphids for this exudate and feed on it. So if ants are spotted on plants there is a good chance that aphids are present. The yellow marks mixed with the green color of the leaves is a virus or a complex of several viruses. The spotted yellow-green leaf color is known as mottling and is very symptimatic of viruses. These viruses generally do not kill the plant but can weaken it."

Control

Several insects are predators of thrips and aphids. These include ladybird beetles and their larva, minute pirate bug and lacewings. Thrips have alternate hosts of weeds and wildflowers. By controlling host plants thrip populations will be lowered. Because thrips do damage inside the rose buds a systemic insecticide should be used. There are several products on the market which control thrips and aphids systemically. Sometimes disystox, a systemic insecticide, is included in rose fertilizer. Always follow label directions when applying pesticides. To reduce the problems of viruses in plants purchase virus-indexed or certified virus free plants. Virus infected plants can be a source of infection that can be transmit to healthy plants by aphids or other insects. Therefore, control the aphids and other insects vectors to control the spread of virus diseases.

Source

Insect Pests of Farm, Garden and Orchard. 7th Ed. R. H. Davidson and W. F. Lyon. pp. 305-6, 311-12.

Question:

The leaves of my roses are drying up. The leaves have a white-grayish fuzzy material coating them. What is this and what can I do?

Answer

Powdery mildew is affecting roses. Powdery mildews are common, widespread, and on many crop and ornamental plants. The total loss by these organisms each year probably surpass the losses caused by any other single type of plant disease. There are many species of powdery mildew. Your apple tree was probably infected by Podosphoera leucotricha and your roses by Spaerotheca pannosa. These fungi are common and cause serious problems in cool and warm humid areas, but are even more of a problem in warm dry climates like Arizona. Powdery mildew spores (fungal seeds"), can be released, germinate, and cause infection when the relative humidity in the air is fairly high, but there is no film of water on plant surface. This spring, with abnormally high rainfall, has favored the growth and spread of powdery mildew. Once infection has begun the fungus spreads on plant surfaces regardless of the moisture conditions in the atmosphere. These organisms send haustoria (feeding organs), into the epidermal cells of plants to obtain nutrients. Powdery mildews are obligate parasites; meaning they cannot be cultured on artificially growing media in the laboratory but must grow on the their specific hosts. Powdery mildew seldom if ever kills its host but utilize their nutrients, reduce photosynthesis, increase respiration and transpiration, impairs growth, and can reduce yields as much as 20-40 percent."

Control

When planting roses or other susceptible plants place them in location with good sunlight and air flow, i.e. not up against the house. Prune plants properly to open them up to ensure air flow through the plant. A rose or euonymus planted on the shady north side of a house will surely have powdery mildew problems. Many new rose varieties have disease resistance to powdery mildew. This resistance will help, but may not completely eliminate the need for chemical control. Chemical controls include spraying or dusting sulfur. Care must be taken not to apply sulfur on hot days because plant tissue can be burned. Other chemical controls include benomyl (Benlate), triadimefon (Bayleton) and triforine (Funginex).

Source

Plant Pathology, George N. Agrios. Third Edition, 1988, pp. 337-342.

Question:

I am confused about fertilizers. What do the numbers on the bag mean? What are the differences between organic and chemical fertilizers?

Answer

By law 3 numbers are required on a fertilizer bag. These are the percentage by weight of nitrogen (N), phosphorus (P) and potassium (K) or N-P-K in that order. Therefore, a bag of ammonium phosphate is marked 16-20-0 or 16% N , 20% P, and 0% K. The N is actual total N no matter what the form. P is really the percentage of P205 and K is really percentage of K2O. (A small side-note: to get the actual amount of P you must multiply the number on the bag by 43% and by 83% to get the actual amount of K. These percentages are derived by taking the atomic weight of the element in question and dividing by the atomic weight of the molecule that the element is in. There have been efforts to revise the current labeling of fertilizers so that only the percentage of P and K appear, but these efforts thus far have ended in failure.) Our soils need N for normal plant growth. This is because it leaches from the root zone. N is absorb most of their N in the NH4+ ammonium and NO3- nitrate. These are both inorganic molecules. Generally plants use nitrate form over the ammonium form. Ammonium is converted to N in the soil by aerobic bacteria and some fungi, therefore cool, wet soils have less active bacteria and will yield less nitrate nitrogen. Nitrate forms of nitrogen are taken up by plants directly and is better used in cool, moist soils. Many nitrogen based fertilizers are made by a process which uses atmospheric nitrogen, the air we breath is about 78% nitrogen, and natural gas or methane under high pressure and heat. Organic forms of nitrogen must be mineralized that is converted into inorganic nitrogen by soil microorganisms for plant use. Also the carbonaceous material of the organic matter is broken down in to humus by soil organisms and use N as an energy source. Organic sources of nitrogen included blood meal which is usually around 15% nitrogen. Our desert soils are also low in native phosphorus and should be added at planting time. Phosphorus binds with the soil and does not leach or can not be melted" into the soil with water like nitrogen. There are several forms of phosphorus many being produced by treating phosphate rock with an acid like phosphoric acid. This yield triple super phosphate or 0-45-0 on the fertilizer bag and can be neutralized with ammonia to make ammonium phosphate and liquid fertilizers. Organic forms of phosphorus are available with bonemeal, 0-12-0 being the most common. Potassium is not needed usually in our desert soils. There are many fertilizers on the market which have other nutrients for plant growth. Higher priced fertilizers have some of these nutrients added and increase the cost. Organic based fertilizers like manures and composts have lower plant nutrient levels but add organic matter to our soils and are more beneficial in this regard than chemically based fertilizers. However, the cost and high amounts needed of organic fertilizers for normal plant growth are very high when compared to bagged chemical fertilizers.

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