Fe and micronutrient nutrition of turf - Natrural Products
 
Micronutrients
 
Seven elements are classified as micronutrients in plant nutrition literature: Fe, Mn, Zn, Cu, B, Mo, and Cl..
 
These elements, although critical and essential for plant growth and survival, are termed micronutrients due to the relatively small quantities required by plants compared to the other eight essential elements.
 
Plant tissue testing has been the most promising method of determining potential micronutrients deficiencies of turfgrasses.
 
As with the macronutrients, however, a variety of factors may influence tissue levels measured in the subsequent interpretation of these levels for diagnostic purposes, including the turfgrass species and varieties (Waddington and Zimmerman, 1972; Butler and Hodges, 1967) and time of sampling (Waddington and Zimmerman, 1972; Hall and Miller, 1974).
 

What levels are micronutrients found in plants?

  • N, P, K - % or parts per 100
  • Ca, Mg, S - parts per 1000 (between 0.1-0.5%)
  • micronutrients-parts per 1,000,000
 
Iron
 
Iron is probably the most important micronutrient in practical terms regarding turfgrass performance.
 
It has been the focus of the greatest amount of turfgrass micronutrient research.
 
Iron is essential in chlorophyll synthesis, as a constituent of several heme and nonheme enzymes and carriers, and may play a role in nucleic acid synthesis.
 
Tissue Fe levels of different turfgrass species grown under identical conditions differ dramatically.
 
Waddington and Zimmerman (1972) reported average tissue Fe concentrations of :
turf species
Fe tissue concentration (mg kg-1)
annual bluegrass
135
Kentucky bluegrass
107
colonial bentgrass
204
creeping bentgrass
170
tall fescue
127
creeping red fescue
111
perennial ryegrass
162
 
Jones (1980) establish the general sufficiency range of 35 to 100 mg kg-1 for turfgrasses.
 
Conditions that may induce Fe deficiencies are varied.
Soils that have a high pH, have very high P levels, are calcareous, or have inherently very low Fe, such as a sandy soil, may cause deficiencies.
 
Iron deficiency may be amplified by high growth rates caused by N applications or by excessive levels of other metal ions.
 
Cold and wet soils, particularly in spring, when growth rates tend to be high, may also induce a Fe deficiency.
 
Ryan et al. (1975) were able to alleviate Fe deficiencies of common bermudagrass grown on calcareous soil through the application of sulfuric acid.
 
Thus, maintaining a soil pH below 7.0 should help minimize some Fe-deficiency problems.
 
Some potential exists for minimizing Fe-deficiencies problems, where soil conditions or management practices may favor such deficiencies, through the selection of Fe-efficient turfgrasses.
 
Kurtz (1981) found substantial differences among zoyiagrass cultivar selections in their ability to use available Fe.
 
Harivandi and Butler (1980) and McCaslin et al. (1981) have found differences in Fe chlorosis among Kentucky bluegrass and bermudagrass varieties as well.
 
The application of Fe, however, has historically been the most common in practical means of correcting Fe deficiencies.
 
Minner and Butler (1984) reported that Kentucky bluegrass color improved with applications of FeSO4 up to a rate of 49 kg ha-1 of Fe.
 
They also found that the initial production of acceptable color could be achieved at much lower rates with Fe chelates compared to FeSO4.
 
Snyder and Schmidt (1974) found that applications to creeping bentgrass of Fe in combination with N, compared to N alone, enhanced appearance, chlorophyll content, and early spring growth, while offsetting the injurious effect of heavy fall-winter N applications.
 
Recovery from Winter desiccation was also improve with Fe applications.
 
In comparing Fe sources, they determined that chelated Fe produced a better root system then FeSO4.
 
Due to the color enhancement achieved with Fe applications without an increase in topgrowth, recent attention has been given to Fe applications as a partial replacement for N and in situations were no apparent Fe deficiencies exist.
 
Yust et al. (1984) investigated means of enhancing the color of Kentucky bluegrass in lieu of excessive N fertilization.
 
They found that color enhancement due to Fe applications at rates of 1.1, 2.2, and 4.5 kg of Fe ha-1 lasted for several weeks to several months depending on the weather following application.
 
When cool wet periods followed application, color enhancement due to Fe applications without N lasted only two to three weeks.
 
When cool dry periods followed application, color enhancement lasted several months.
 
Iron chelate, compared to FeSO4, at the 2.2 kg ha-1 rate, produce the best overall results.
 
Combining Fe with 25 kg of N ha-1 produce color equal to 49 kg of N ha-1.
 
Due to the relatively small actual quantities of micronutrients needed by turfgrass plants, the potential for creating detrimental effects or toxicity strongly exists, both through overapplication or complex interactions with other essential elements.
 
Deal and Engel (1965) reported severe discoloration, burning, and inhibition of rhizome formation of Kentucky bluegrass from the application of 56 kg of Fe ha-1.
 
Under high fertility, all Fe rates investigated adversely affected sod density for 10 weeks.
 
Yust et al. (1984) observe no serious injury (consider foliar dieback) to Kentucky bluegrass from Fe applications up to 17.7 kg ha-1.
 
A blackish green color appeared on turf treated with Fe applications of 4.5 to 17.7 kg ha-1; however, it generally recovered within two weeks.
 
Manganese
 
Manganese serves in plant nutrition as an activator of numerous enzymes, particularly oxidation-reduction reactions, and as a constituent of one known enzyme.
 
It is involved in chlorophyll synthesis and plays a role in photosynthesis.
 
The amount of Mn found in turfgrass tissue is typical of most micronutrients.
 
Waddington and Zimmerman (1972) measured average Mn levels of:
turf species
Mn tissue concentration (mg kg-1)
annual bluegrass
250
Kentucky bluegrass
154
colonial bentgrass
414
creeping bentgrass
339
tall fescue
434
creeping red fescue
185
perennial ryegrass
304
 
A great deal of tissue Mn variation can occur throughout the year.
 
Waddington and Zimmerman (1972), for example found tissue Mn in creeping bentgrass to vary from a low of 163 mg kg-1 to a high of 391 mg kg-1 in one season.
 
Jones (1980) suggests a sufficiency range of 25 to 50 mg kg-1 for turfgrasses.
 
As with most of the micronutrients, few observations of turfgrass responses to Mn have been noted.
 
Deal and Engel (1965) reported that Mn applications to Kentucky bluegrass did not affect clipping yields, but lower rates stimulated root growth and improved color for about four weeks when fertility levels were low.
 
Soil Reaction
 
The effect of soil reaction on turfgrass performance has been reported in numerous studies.
 
The reasons for these responses may be numerous, but are often not precisely known.
 

They may include:

  1. direct effects, such as H-ion toxicity
  2. increased or decreased availability of essential elements
  3. increased availability of nonessential elements, such as aluminum which become toxic
  4. indirect effects, such as changing the microbial environment and thus their populations.
    These microbiological changes may in turn affect turfgrass performance through their effect on disease incidence, thatch decomposition, and N conversion reactions and thus N availability the turfgrass plant.
 
Soil reaction changes may be brought about through numerous means.
 
Increases in soil acidity may be due to material applications by humans, such as NH4-based N fertilizers and S or S-containing pesticides, or by natural processes, such as thatch and organic matter decomposition.
 
Decreases in soil acidity may be brought about by the addition of liming materials or continued use of irrigation water having a basic reaction.
 
The mechanisms of these reactions and the characteristics and comparison of various liming and acidifying agents, as well as the effects on nutrient availability and uptake, have been reviewed in detail.
 
Turfgrass species have been reported to have somewhat different optimal ranges of soil reaction.
 
Musser (1950) reported the soil reaction ranges for good growth.
 
turf species
Optimum soil pH
zoysiagrass
4.5 to 7.6
bermudagrass
5.1 to 7.1
centipedegrass
4.0 to 6.1
St. Augustinegrass
6.1 to 8.1
creeping red fescue
5.4 to 7.6
chewing fescue
5.4 to 7.6
tall fescue
5.4 to 7.6
bentgrass
5.4 to 7.6
Kentucky bluegrass
6.0 to 7.6
annual bluegrass
5.1 to 7.6
roughstock bluegrass
5.7 to 7.6
ryegrasses
5.5 to 8.1
 
Growth and establishment responses to differences in soil reaction have been shown, but also vary considerably.
 
Juska (1959) reported on the influence of liming 'Meyer' zoysiagrass.
Substantial increases in root, stolen, and topgrowth occurred as soil pH was increased by liming from 4.7 to 6.1 if N was applied as well.
 
If N was not applied, this change in soil reaction had little effect.
No detrimental effect occurred with increases in soil pH to 8.0, was stolen growth actually being further encourage.
 
Murray and Foy (1980) reported that tall fescue was much more tolerant of acid soil than Kentucky bluegrass. In another report (Murray and Foy, 1978), they found that tall fescue had greater sensitivity to soil acidity than fine-leaved fescues, with greater tall fescue growth occurring in a soil pH of 5.7 than 4.3.
 
Although fine-leaved fescues also exhibited increased growth at the higher pH, the majority of cultivars had adequate growth at 4.3 soil pH.
 
Juska and Hanson (1966) reported greater root yields of annual bluegrass on a loamy sand with a pH of 6.5 versus 4.5, although they found no differences on a silt loam.
 
Duell (1974) reported that Kentucky bluegrass varieties produce maximum growth in a pH range of 6.0 to 6.5, perennial ryegrass at 6.0 to 6.4, and tall fescue at 6.0 to 7.0.
 
All of the species decreased in growth above a pH of 7.0.
 
Contrary to other reports, red fescue growth was found to decrease as the pH increased from 4.2 to 7.6 due to limestone applications.
 
Due to species differences in preferred soil reaction, proportions of species in turfgrass mixtures can be affected by soil pH.
 
Musser (1948) found the portion of Kentucky bluegrass on a Kentucky bluegrass-bentgrass turf was higher under low acidity, with bentgrass showing a wide range of tolerance to soil pH.
 
Within a given species, cultivars may show substantial differences in response to soil pH levels.
 
Murray and Foy (1980) compared 12 Kentucky bluegrass cultivars at soil pH levels of 4.4 up to 7.6.
 
Only six cultivars produce measurable growth at a pH of 4.4.
 
Liming to raise soil pH to 5.0 substantially increased growth of all cultivars.
 
Relationships between soil reaction and various diseases have been reported.
 
Ledeboer and Skogley (1967) found greater incidence of Dollar Spot on bentgrass when 2440 kg of limestone ha-1 was applied than when none was applied; however,
 
Couch and Bloom (1960) and Turner (1980) reported no influence of pH or liming on Dollar Spot of bentgrass or perennial ryegrass, respectively.
 
Bloom and Couch (1960) found an interaction between N levels and pH on brown patch severity of bentgrass , with pH having an influence when N was moderate to high, but not when N was low.
 
Turner (1980) found decreases in red thread incidence of perennial ryegrass with two limestone applications of 3050 kg ha-1 on a soil with a pH of 5.6 , although lower rates of applications had little influence.
 
Sartin (1985) reported that annual bluegrass encroachment during the cool season into bermudagrass increased from 0 to 63% as soil pH increased from 5.0 to 5.8.
 
It appeared that the incidence of annual bluegrass and common chickweed and bermudagrass during the cool-season growth period could be minimized by maintaining the soil pH between 4.5 and 5.0.
 
Turner et al. (1979) reported less dandelion encroachment into 'Merion' Kentucky bluegrass on soil with a pH of 5.6 than a soil limed to pH 6.4.
 
Natural Products
 

Natural products may be classified loosely as:

  1. organic fertilizers
  2. antioxidants
  3. biostimulants
  4. soil organic matter
 
Organic fertilizers generally contain partially decomposed organic matter from sources such as animal waste products, seaweed, or other plant or animal products.
 
They are often augmented by small amounts of mineral fertilizer sources.
 
Antioxidants
 
Antioxidants can reduce some stresses.
 

Stress can result from the accumulation of reactive oxygen species (ROS)

  • superoxide O2-
  • H2O2
  • hydroxy radicals -OH
 
ROS causes membrane damage, lipid oxidation and enzyme inactivation.
 
  • Antioxidant defenses
  • alpha-tocapherol (vitamin E)
  • Beta-Carotene
  • superoxide dismutase (SOD)

O2- in the presence of SOD   ->   H2O2 dehydro a scorbute reductose  ->   H2O
 
Biostimulants
 
what are they
  • seaweed extracts
    • contain cytokinins, auxins
  • humic acid extracts
    • humates
  • triazole fungicides
    • synthetic
  • plant growth regulators
  • others
    • selenium
    • salicylic acid (aspirin)
 

Biostimulant claims

  1. increased stress tolerance
  2. reduce diseases
  3. increased root growth
 

plant responses to cytokinins

  1. increased leaf production
  2. increased chlorophyll levels
  3. leaf senescence is delayed
  4. apical dominance is reduced
  5. root growth is reduced
 
The benefit of cytokinins seems to be a delay in leaf senescence that may increased overall photosynthesis efficiency.
 
This could lead to more root growth since extra carbohydrates could be produced.
 

Plant responses to auxins

  1. increased cell elongation
  2. regulates apical dominance
  3. promotes formation of lateral roots
 
Seaweed extracts contain both cytokinins and auxins and can increase root mass and the root/shoot ratio.
 
Research has been somewhat inconclusive with both positive and negative results.
 
Humic acid - humates
 
These are organic molecules that may stimulate color and growth by serving as chelating agents.
 
FE, Mn, Zn may be taken up more readily when humates are applied to turf.
 
Triazole fungicides
examples propiconazole (Banner), triadimefon (Bayleton)
 

What do they do?

  1. control diseases
  2. increased root growth
  3. show growth regulating activity
  4. synthetic plant growth regulators
    • covered later in class