Know your Micro-Nutrients; how they work, get absorbed by the roots (uptake), are assimilated into the plant tissues, how to pinpoint a deficiency and its symptoms and what to do to correct a nutrient-lack situation. 

Before I start describing each and every micro-nutrient I'd like to remind you that every field is a different situation, that soil sampling is the first step in assessing and managing a farm and that if resources are available (time, money, equipment and know-how) compartmentalizing fields into homogeneous sections is ALWAYS recommended. The most important soil property that affects nutrient and mineral availability is pH (Figure 1).

If we look at the Figure 1, what can we get from it ? Ideal pH for most crops would be in the ''Very slightly acid" to the "Very slightly alkaline" or pH 6.5 - 7.5. In soils with low pH there will be a less availability of the most important nutrients (N, P, K, S, Ca, Mg, Mo) because they will be either bound to the soil coloids (Clay and Organic Matter) since the soluble forms (Soluble form is the form that the plants will uptake the elements) are positively charged or have been transformed into lose-able forms due to interactions with the Protons [H+] in the solution. . Furthermore, other Elements will be in a higher concentration (Fe, Mg, B, Cu, Zn) which can cause an adverse situation around the Rhizosphere, although those elements are needed by the plants, they need to be in extremely low concentrations. 

Management practices to correct such situation is the addition of a strong base like Lime Stone (CaCO3 or Calcium Carbonate). Another property to keep in mind while deciding whether to increase or decrease the pH of a soil is the Soil's Buffer Capacity, which is the measure (quantitative) of the resistance of the Soil solution to pH change when adding an Acid or a Base. 

• Sulfur (S): 
• Functions in plants: Essential for amino acid synthesis and protein formation. Necesarry for seed production, increase oil content in oilseed crops and promotes nodulation in legumes. 
• Form used by plants: SO4-- (Sulfate).
• Forms in the soil: Sulfate anion (SO4--), Element sulfur (S) and Organic sulfur (tied up to OM).
• Factors leading to its deficiency: Low OM, heavy texture soils, eroded soils, cold wet or poorly drained soils.
• Deficiency symptoms: Stunting, yellowing or chlorosis, newer tissue is yellower than older tissues, delayed maturity. Alfalfa and Corn are more affected by its deficiency due to they higher demand for this element. 

• Magnesium (Mg):
• Functions in plants: Actively involved in photosynthesis, forming the chlorophyll molecule. Involved in translocation of P in the plant. Regulates the uptake of other elements.
• Form used by plants: Mg++ (Exchangeable magnesium cation)
• Forms in the soil: Mg++, chemical compound as carbonates, oxides, bicarbonates, and silicates. Component of complex soil mineral structures.
• Soil factors leading to its deficiency: Acid sandy soils, excessive K fertilization.
• Deficiency symptoms: Interveinal chlorosis in the older to newer leaves. veins remain green. 

• Calcium (Ca)
• Functions in plants: Essential in Calcium Pectate (plant cell walls strenght), promotes root formation and leaf development, increases nodulation and bacterial activity in legumes, protein synthesis. 
• Form used by plants: Ca++ (Calcium cation)
• Forms in the soil: Ca++, chemical compound as carbonates, bicarbonates, oxides and silicates. 
• Soil factors leading to its deficiency: Acid soils (Strong acid range from Figure 1).
• Deficiency symptoms: Both root and shoot apex stunting, leaf tips can stick together and unfold abnormally. Younger growth can die back on the edges.q

• Zinc (Zn)
• Functions in plants: Essential for protein synthesis. Promotes seed and grain formation and plant maturity. Necessary for growth regulation and enzyme systems as a co-factor.
• Form used by plants: Zn++ (Exchangeable Zinc Cation)
• Forms in the soil: Zn++ held to clay coloids and OM, part of Zn mineral complexes.
• Soil factors leading to its deficiency: Low OM soils, sandy and eroded soils, high pH, calcerous soils (Zn will become less soluble as pH surpases 7,0). High P test levels, cold wet and poorly drained soils. Compation.
• Deficiency symptoms: General stunting by shortened internodes. Striped chlorosis (grasses) and mottling (broadleaves). Notorious in older young leaves as it is translocated to the newer growth. 

• Boron (B) 
• Functions in plants: Facilitates the transport of sugars through membranes, necessary for cell division and cell development, involved in plant utilization of N and P, including synthesis of nucleic acids and protein.
• Form used by plants: BO3--- (anion)
• Forms in the soil: H3BO3, H2BO3-, BO3---, B(OH)4-
• Soil factors leading to its deficiency: Precipitated on soil mineral surfaces, especially the micaceous clay minerals, Low B Test (Boiling Water Extraction), sandy, low organic matter soils that leach easily, soils in high rainfall climates, high pH, drought.
• Deficiency symptoms: Shortened internodes at the tip apix (rosette appearence).

• Iron (Fe)
• Functions in plants: Essential for chlorophyll formation, necessary for photosynthesis, part of enzyme system necessary for plant respiration, formation of some proteins.
• Form used by plants: Fe++ (cation).
• Forms in the soil: Fe++ (Ferrous) or Fe+++ (Ferric), insoluble oxides and hydroxides. 
• Soil factors leading to its deficiency: Excessive P, Ca, Zn, Mn, Cu can reduce Fe availability. pH greatly affects its availability.
• Deficiency symptoms: Stunting and spindly. Chlorosis of younger growth, veins remain green. Most notorious in Milo and Soybeans. 

• Manganese (Mn)
• Functions in plants: Essential for photosynthesis. Co-factor of several enzymes. Involved in nitrate assimilation. 
• Form used by plants: Mn++ (cation)
• Forms in the soil: Mn++
• Soil factors leading to its deficiency: Very sensitive to pH. Soluble and available in acid soils. Strong acid soils can have a Mn toxicity for the plants. 
• Deficiency symptoms: Yellowing between leaf veins, veins remain green (soybeans, edible beans, potatoes).

• Copper (Cu)
• Functions in plants: Essential in plant enzymes and protein synthesis. Promotes seed production. Important to chlorophyll formation. 
• Form used by plants: Cu++ (Cation)
• Forms in the soil: Cu+ (Cuprous cation) and Cu++ (Cupric cation). Adsorbed to clay mineral surfaces. Part of organic complexes. 
• Soil factors leading to its deficiency: Very high pH soils. High OM % (peat, mucks). Excessive Zn, Fe, or Mn may reduce its availability. Sandy soils.
• Deficiency symptoms: Small grains, leaf tips wilt, then die, looking like frost damage. Leaf tips stick together. Chlorosis and necrosis of youngest leaves.

• Molybdenum (Mo)
• Functions in plants: Required in legume nodule to fix N from atmosphere. Component of the enzyme in plants which causes Nitrate to be reduced to amino nitrogen, used in protein synthesis. 
• Form used by plants: MoO4-- (anion).
• Forms in the soil: MoO4-- (Molybdate) anion, pH 5-6 as HMoO4- anion. 
• Soil factors leading to its deficiency: low soil pH, solubility declines as pH icnreases. Very sandy soils, especially high weathered soils may be low in available Mo. 
• Deficiency symptoms: Poor nodule formation on legume roots. Pale green to yellow color of older leaves. Stunted plant growth. 

I hope you find this useful. I promise I will pin some pictures soon.