Iron Sulfate foliar sprays for chlorosis

[zands]

Impacts
Application of chelated iron to the soil has become a standard practice for growing tropical and subtropical fruit trees in calcareous soils. However, chelated iron is extremely expensive. In subtropical and tropical fruit orchards in south Florida, chelated iron can represent up to 80% of the total fertilizer cost and up to 50% of the total agricultural chemical costs for subtropical and tropical fruit production. There is obviously a need for a cheaper alternative to the application of chelated iron for preventing or alleviating iron deficiency in fruit crops grown in calcareous soils. Foliar applications of weak acids or weak acids combined with iron sulfate is a much cheaper alternative to chelated iron for preventing iron deficiencies in subtropical fruit and tropical fruit crops. Thus there is the potential to significantly reduce production costs thereby making the subtropical and tropical fruit industry more globally competitive. In addition to the tremendous costs associated with soil applications of chelated iron, soil applied iron chelates can be easily leached from the root zone if irrigation is excessive. Leaching of chelated iron away from the root zone not only wastes very costly iron fertilizer, but also has the potential for polluting the groundwater aquifer, which in south Florida is only a few meters below the soil surface. Therefore, in addition to potential huge financial savings, this research has the potential to reduce environmental pollution from leaching of soluble iron from the soil into the groundwater.

More here>>>>>>

http://www.reeis.usda.gov/web/crisprojectpages/0203864-foliar-acid-applications-to-prevent-iron-deficiency-in-tropical-fruit-crops-grown-in-calcareous-soils.html


Summary>>>
A foliar of iron sulfate plus an acid such as citric or sulfuric can be very effective and less expensive than the iron chelates used at the roots or as a foliar. Chelated iron can be 80% of fertilizer expenses in tropical and subtropical fruit orchards










Here is the rest of this study>>>>




Goals / Objectives
The overall objective of this project will be to evaluate foliar applications of weak (citric, ascorbic and dilute sulfuric) acids as cost-effective alternatives to the current standard practice of applying very expensive chelated iron to calcareous soil to prevent iron deficiency in tropical and subtropical fruit trees. The specific hypotheses to be tested are: 1)foliar applications of weak acids will decrease the pH of the leaf apoplast of trees grown in calcareous soils, thus increasing the bioavailability of iron and preventing or eliminating iron deficiency 2)incorporating the spraying of weak acids into an orchard management program will provide a more cost effective means of preventing iron deficiency in subtropical and tropical fruit crops than the current practice of applying chelated iron to the soil.
Project Methods
Greenhouse experiments will be conducted with common commercial cultivars of one to two-year-old avocado (Persea americana Mill.), carambola (Averrhoa carambola L.), lychee (Lychi chinensis L.)and pond apple (Annona glabra L.) trees. Plants will be purchased from commercial nurseries. Trees will be transplanted from the nursery media into pots containing Krome very gravelly loam soil that has been collected in the field at TREC. After three months, trees of each species will be divided into the following treatments: 1) foliar application of ascorbic acid and no iron applied to the soil, 2) foliar application of citric acid and no iron applied to the soil, 3) foliar application of dilute sulfuric acid and no iron applied to the soil, 4) no foliar application and no iron applied to the soil, and 5) no foliar acid application and chelated iron applied to the soil at a recommended rate (0.5 oz/tree). Orchard experiments will also be conducted at TREC with avocado (cv. Booth 7 on seedling rootstocks), carambola (cv. Arkin on Goldenstar rootstock) and lychee (cv. Brewster). Treatments applied to orchard trees will be the same as those applied to the plants in the greenhouse except that foliar sprays will be applied to orchard trees every two weeks with an air-blast sprayer for two consecutive years. In greenhouse and orchard experiments, leaf chlorophyll index will be measured periodically from mature (hardened off) and young (recently fully expanded) leaves of each tree with a SPAD chlorophyll meter. The pH of the leaf apoplast will be measured with an ion-selective microelectrode. Concentrations of Fe3+ and Fe2+ and total extractable iron in the leaves and total extractable iron in the soil will be determined in the greenhouse and orchard experiments. Immediately before imposing treatments and one year after treatments are applied, height and trunk diameter of trees in each treatment in the greenhouse will be measured. Greenhouse trees will harvested about one year after initial treatment applications and dry weights of leaves stems and roots of plants in each treatment will be determined. In the orchard experiment, trunk diameter (10 cm above the soil surface) will be measured before treatments are imposed, after one year and just prior to termination of the experiment. Fruit from trees in each treatment in the orchard will be harvested when fruit are mature and fruit number and weight per tree will be determined. Economic analyses will be performed at each stage of the assessment to ensure that the technologies tested and generated are cost effective and sustainable.
Progress 09/15/06 to 09/14/07

Outputs
The following treatments were applied to carambola, lychee and avocado trees in orchards in southern Florida: 1) foliar application of ascorbic acid - 2 g/L, 2) foliar application of citric acid - 2 g/L, 3) foliar application of sulfuric acid - 100 mg/L, 4) foliar application of ascorbic acid plus iron sulfate 5) foliar application of citric acid plus iron sulfate, 6) foliar application of sulfuric acid plus iron sulfate, 7) chelated iron applied to the soil, and no iron or acid applied to the plants. However, treatments 2 and in an avocado orchard, trees received all treatments except for treatments 1 and 3. In the carambola and lychee orchards all foliar applications of acid plus iron sulfate resulted in leaves that were as green or greener (as determined with a SPAD meter) than those of the soil-applied iron treatment and greener than the control treatment that received no iron applications to the foliage or soil. The effects of the acid plus ferrous sulfate treatment were greatest with ascorbic and sulfuric acids for both species. The effects of foliar sprays on re-greening of leaves were first visibly detectable after two foliar applications of acids plus ferrous sulfate. For carambola and lychee, total leaf iron concentration and ferrous iron concentration in the leaves were greater for all of the acid plus iron foliar applications and soil iron application treatment than the controls or the acid only foliar treatments. There were no statistically significant differences in sap pH among treatments. Treatments in the avocado orchard were initiated later than treatments in the lychee and carambola orchard because it took time for avocado trees in an orchard to become sufficiently chlorotic for the study. In the avocado orchard, after six treatments, foliar sprays of ascorbic acid plus iron sulfate resulted in leaves that were as green as those of plants receiving soil applications of chelated iron. There were no statistically significant differences in leaf sap pH among treatments. However, ferrous iron concentrations in the leaves were greater in the soil applied iron or foliar acid plus iron treatments than in all other treatments. Total leaf iron concentration in avocado was highest for the sulfuric acid plus ferrous sulfate and citric acid plus ferrous sulfate than the other treatments. Preliminary economic analysis for carambola, lychee and avocado orchards indicated that foliarly applied acids plus ferrous iron is a much cheaper alternative to the current standard practice of applying chelated iron to the soil.

Impacts
Application of chelated iron to the soil has become a standard practice for growing tropical and subtropical fruit trees in calcareous soils. However, chelated iron is extremely expensive. In subtropical and tropical fruit orchards in south Florida, chelated iron can represent up to 80% of the total fertilizer cost and up to 50% of the total agricultural chemical costs for subtropical and tropical fruit production. There is obviously a need for a cheaper alternative to the application of chelated iron for preventing or alleviating iron deficiency in fruit crops grown in calcareous soils. Foliar applications of weak acids or weak acids combined with iron sulfate is a much cheaper alternative to chelated iron for preventing iron deficiencies in subtropical fruit and tropical fruit crops. Thus there is the potential to significantly reduce production costs thereby making the subtropical and tropical fruit industry more globally competitive. In addition to the tremendous costs associated with soil applications of chelated iron, soil applied iron chelates can be easily leached from the root zone if irrigation is excessive. Leaching of chelated iron away from the root zone not only wastes very costly iron fertilizer, but also has the potential for polluting the groundwater aquifer, which in south Florida is only a few meters below the soil surface. Therefore, in addition to potential huge financial savings, this research has the potential to reduce environmental pollution from leaching of soluble iron from the soil into the groundwater.

Publications
Crane, J.H., B. Schaffer, W. Montas. 2007. Effect of ascorbic acid plus ferrous sulfate on leaf greeness of carambola (Averrhoa carambola L.) Trees. Proc. Fla. State Hort. Soc. (in press).Crane, J.H., B. Schaffer, Y.C. Li, E.A. Evans, W. Montas, C. Li. 2007. Effect of foliarly-applied acids and ferrous sulfate on iron nutrition of avocado trees. Proc. VI World Avocado Congress, Vina del Mar, Chile (in press).
Progress 09/15/05 to 09/14/06

Outputs
For subtropical and tropical fruit crops in calcareous soil, foliar applications of weak acids with or without iron sulfate were tested as alternatives to applying expensive chelated iron to calcareous soil to prevent iron deficiency. In a greenhouse study, avocado (Persea americana), carambola, (Averrhoa carambola), lychee (Litchi chinensis), and pond apple (Annona glabra) trees in pots containing calcareous soil received the following treatments: 1) foliar application of ascorbic acid - 2 g/L, 2) foliar application of citric acid - 2 g/L, 3) foliar application of sulfuric acid - 100 mg/L, 4) foliar application of ascorbic acid plus iron sulfate 5) foliar application of citric acid plus iron sulfate, 6) foliar application of sulfuric acid plus iron sulfate, 7) chelated iron applied to the soil, and no iron or acid applied to the plants. The same treatments were applied to carambola, lychee and avocado trees in orchards. However, because deionized water was used for greenhouse treatments and well water was used for orchard treatments, the concentrations of acids were adjusted for the orchard treatments to achieve the same pH as in the greenhouse experiments. Various spreader/stickers were tested with each acid plus iron sulfate formulation prior to initiating the treatments. All spreader/stickers tested except Freeway resulted in brown spots on the foliage indicating poor spreading and absorption of iron. Therefore, Freeway was added to all of the foliar treatments. Also, prior to initiating treatments, all treatments were tested for phytotoxicity and none was observed. Treatments were applied at 2-3 week intervals. Leaf chlorophyll index, a measure of leaf greenness, was measured periodically from five mature and five young leaves of each tree with a SPAD chlorophyll meter. The pH of the leaf sap, total iron concentrations in the leaves and soil and ferrous iron concentrations in the leaves were determined periodically. For carambola and lychee trees in the greenhouse and orchards, all foliar applications of acid plus iron sulfate resulted in leaves that were as green or greener than those of the soil-applied iron treatment and greener than leaves of the controls. All foliar acid treatments without iron resulted in leaves that were slightly greener than the controls but not as green as the other treatments. In the greenhouse study, avocado and pond apple in the control treatment did not show any symptoms of iron chlorosis, so there were no significant effects of the foliar acid treatments with or without iron sulfate. Avocado treatments in an orchard have just been initiated and data will be collected soon. Leaf and soil iron concentrations are still being analyzed from greenhouse and orchard studies. Preliminary economic analysis indicated that foliarly applied acids plus ferrous iron is a much cheaper alternative to the current standard practice of applying chelated iron to the soil.

Impacts
Application of chelated iron to the soil has become a standard practice for growing tropical and subtropical fruit trees in calcareous soils. However, chelated iron is extremely expensive. In subtropical and tropical fruit orchards in south Florida, chelated iron can represent up to 80% of the total fertilizer cost and up to 50% of the total agricultural chemical costs for subtropical and tropical fruit production. There is obviously a need for a cheaper alternative to the application of chelated iron for preventing or alleviating iron deficiency in fruit crops grown in calcareous soils. Foliar applications of weak acids or weak acids combined with iron sulfate is a much cheaper alternative to chelated iron for preventing iron deficiencies in subtropical fruit and tropical fruit crops. Thus there is the potential to significantly reduce production costs thereby making the subtropical and tropical fruit industry more globally competitive. In addition to the tremendous costs associated with soil applications of chelated iron, soil applied iron chelates can be easily leached from the root zone if irrigation is excessive. Leaching of chelated iron away from the root zone not only wastes very costly iron fertilizer, but also has the potential for polluting the groundwater aquifer, which in south Florida is only a few meters below the soil surface. Therefore, in addition to potential huge financial savings, this research has the potential to reduce environmental pollution from leaching of soluble iron from the soil into the groundwater.

Publications
Publications

    Crane, J.H., B. Schaffer, W. Montas. 2007. Effect of ascorbic acid plus ferrous sulfate on leaf greeness of carambola (Averrhoa carambola L.) Trees. Proc. Fla. State Hort. Soc. (in press).
    Crane, J.H., B. Schaffer, Y.C. Li, E.A. Evans, W. Montas, C. Li. 2007. Effect of foliarly-applied acids and ferrous sulfate on iron nutrition of avocado trees. Proc. VI World Avocado Congress, Vina del Mar, Chile (in press).

Outputs
OUTPUTS: Iron deficiency is a major problem of many tropical tree species grown in calcareous soils. Applying chelated iron to calcareous soil is efficacious but very expensive. The effects of foliarly applied organic acids and organic acids plus ferrous sulphate (Fe) on iron nutrition of avocado, carambola and lychee trees in calcareous soil was investigated in southern Florida. Trees in orchard and greenhouse studies received the following foliar treatments: ascorbic acid (AA alone), ascorbic acid plus FS (AA+Fe), citric acid plus FS (CA+Fe), and sulphuric acid plus (SA+Fe). Additional treatments were chelated iron (EDDHA-Fe) applied to the soil 3 times at 27-28 day intervals and a control receiving no iron or acid (CNT). All foliar treatments included the organosilicone adjuvant, Freeway. Later, additional tests were conducted comparing soil applications of chelated iron to foliar applications of ferrous iron with and without the organosilcone adjuvant and the solution adjusted to various pHs. Data collection included total and ferrous iron content in leaves, leaf greenness as determined with a SPAD meter, plant growth, and yield. In general, applications of weak organic acids were only slightly effective at reducing iron deficiency. However, foliar applications of iron sulphate combined with the organosilicone adjuvant was almost as effective at preventing or eliminating iron deficiency as soil applications of chelated iron. Foliar applications of ferrous sulphate with no adjuvant were not effective at preventing iron deficiency and all other adjuvants tested resulted in phytotoxicity or poor absorption of foliarly applied iron. Economic analysis indicated that foliar acid-iron treatments were about 60 to 88% less costly than soil applications of chelated iron. Further tests are underway to determine the best application rates and timing of foliar sprays for preventing iron deficiency to tropical fruit crops growing in calcareous soil. Future studies will also focus on a combining of soil applications of chelated iron with foliar iron sulphate sprays to determine if combining the two would be the best compromise between cost effectiveness and prevention of iron deficiency. Results have been disseminated to growers and extension workers through workshops, field demonstrations, presentations at state, national and international horticultural meetings and publications in non-refereed journals. Results will eventually be published in refereed journals after some additional data are collected. PARTICIPANTS: Bruce Schaffer, P.I., Project coordinator and designer. Responsible for oversight of all aspects of the project Yuncong Li, Co-PI., Coordinator of nitrogen analysis. Jonathan Crane, Co-P.I., Management of field applications and field data collection Chunfang Li, Senior Biologist, Assisted with data collection and data analysis and maintenance of experimental plots. Wanda Montas, Senior Biologist, Assisted with data collection Mike Gutierrez, Research Technician, Assisted with data collection TARGET AUDIENCES: Tropical fruit growers and extension personnel in areas with calcareous agricultural soils. PROJECT MODIFICATIONS: The methodology for sap pH collection was too variable to be scientifically useful. Therefore, data for this variable was not collected after the first year. During the first 2 years of the study, there were several hurricanes and storms that significantly reduced fruit yields in the field. Therefore, yield data was not collected until the last year for the study. however, we will continue treatments and continue to collect yield data for at least 2 years after this study is terminated.

Impacts
Application of chelated iron to the soil has become a standard practice for growing tropical and subtropical fruit trees in calcareous soils. However, chelated iron is extremely expensive. In subtropical and tropical fruit orchards in south Florida, chelated iron can represent up to 80% of the total fertilizer cost and up to 50% of the total chemical cost for subtropical and tropical fruit production. There is obviously a need for a lower cost alternative to the application of chelated iron for preventing or alleviating iron deficiency in tropical and subtropical fruit trees grown in calcareous soils. Thus there is potential to significantly reduce production costs and thereby make the subtropical and tropical fruit industry more globally competitive. In addition to the tremendous costs associated with applications of chelated iron to orchards, chelated iron can be leached from the root zone if irrigation is excessive. Leaching of chelated iron away from the root zone not only was very costly iron fertilizer, but also has the potential for polluting the groundwater aquifer, which in south Florida is only a few meters below the soil surface. Therefore, in addition to potentially huge financial savings, this research has the potential to reduce environmental pollution from leaching of soluble iron from the soil into the groundwater.[/size][/font][/left]

[stressbaby]

Interesting...vitamin C is often combined with ferrous sulfate to improve iron absorption in humans.

[TropicalFruitHunters]

Geesh...you say that like you're a doctor or something!!     LOL!

[FlyingFoxFruits]

thanks Zands,

intersting info.

[KarenRei]

Interesting... I stock both citric acid and iron sulfate.  If I ever get any iron deficiencies, I'll give that a try.

[jez251]

For those of you in the South Florida area, where exactly do you get the iron sulfate or chelated iron supply? From Atlantic-Florida East Coast Fertilizer & Chemical? Home Depot? Are there any other places to get these nutritional supplies?

I have a few plants that look like they have chlorosis, primarily my Nance, Grumichama and Vexator!

Jaime

[ofdsurfer]

jez251 - I purchased chelated iron from diamond r fertilizer for around $45 for a five lb bag.

[jez251]

jez251 - I purchased chelated iron from diamond r fertilizer for around $45 for a five lb bag.

Thanks, ofdsurfer... I'll take a look at their site to see their offerings.

Jaime

[Pan Dulce]

The funny thing is the soil has plenty of iron but it is bound to the minerals in the calcareous soils and the need for chelated iron drenches.  This new iron sulfate/ PH reduced water mix is not something you will be able to mix at home, but from what I understand will be hundreds of times cheaper than chelated iron.  Maybe the recipe will be released and all the dooryard, and commercials types will benefit.

[Saltcayman]

The funny thing is the soil has plenty of iron but it is bound to the minerals in the calcareous soils and the need for chelated iron drenches.  This new iron sulfate/ PH reduced water mix is not something you will be able to mix at home, but from what I understand will be hundreds of times cheaper than chelated iron.  Maybe the recipe will be released and all the dooryard, and commercials types will benefit.

I'm not sure what the results will be but I just added mulch, sulphur and humates to my soil to bring the ph down to make the iron more available. You have to keep adding sulphur every few months.  Soil has ph of 8.2.  I have a calcareous red laterite soil and my fingers crossed:) has anyone els tried sulphur?   Dave

[zands]

The funny thing is the soil has plenty of iron but it is bound to the minerals in the calcareous soils and the need for chelated iron drenches.  This new iron sulfate/ PH reduced water mix is not something you will be able to mix at home, but from what I understand will be hundreds of times cheaper than chelated iron.  Maybe the recipe will be released and all the dooryard, and commercials types will benefit.

I have iron sulfate and citric acid....both from eBay. I am ready to mix them and use them when I find the right amounts and application. Proper use of plain iron sulfate foliar is on the internet, I have it somewhere. So just add some acid. The right amount and some dish washing soap. I'll try it when I know more

[FlyingFoxFruits]

what are some saftey concerns when using this mix of chemicals?

will I burn some skin off my hands or stain my eyeballs a nice ruddy hue?

or is there no real safety issues associated with this application?

[Pan Dulce]

Nope just gonna become Ironman 

[Bananimal]

jez251 - I purchased chelated iron from diamond r fertilizer for around $45 for a five lb bag.

What is the dose and application method for their chelated iron?  I use Diamond R all the time for my ferts.  They have never set up a website with a full list of the stuff they carry.

Dan

[Guanabanus]

Be very careful spraying iron on foliage, especially iron sulfate--- it burns leaves more easily than most other nutrients.  This why, when large amounts of iron are needed, soil application is usually preferred.

There is now an organically-approved herbicide in which iron is the active ingredient.

[CTMIAMI]

I had yellowing avocado trees that tested normal for iron while using iron sulphate in my regular granular fertilization program, My soil PH is 7.5, I have added Chelated iron but the one made for high PH soil and the trees  greens up right away.  Sequestrine 138 is the brand. They also have generic equivalent.

The spraying thing is Ok it you have a few trees and if they are not too tall. In my case a have several acres with micro jet irrigation and it is a breeze to apply the iron with the irritation system.   if you add the equipment and labor cost the cheleted is less expensive and more effective in high PH soil. 

[FlyingFoxFruits]

I can vouch for Har on this one!

I drenched the heck out of some plants I have (M. strigipes, and A. diversifolia), and during thesse high concentration applications, I got some product on my leaves..which resulted in leaf burn!

they will live, but some the leaves don't look happy.

Be very careful spraying iron on foliage, especially iron sulfate--- it burns leaves more easily than most other nutrients.  This why, when large amounts of iron are needed, soil application is usually preferred.

There is now an organically-approved herbicide in which iron is the active ingredient.