Often times we cna look at the leaves of a plant to determine what nutrients are missing in the soil which the plants need. It would be nice to have a repository of images with accompanying deficiency information. Is there anywhere I can find such?
Here is the general rule-of-thumb I use to identify nutrient deficiences in plants.
Deficiencies indicated by symptoms appearing first on older leaves
- chlorosis starting from leaf tips, later leaves turn yellowish-brown: N
- reddish/purple discoloration on green leaves or stalks: P
- leaves with brown necrotic margins and/or spots: K
- stripe chlorosis, mainly between veins, while veins remain green: Mg
- spot necrosis: greyish-brown stripe-form spots in oats (grey-speck disease): Mn
- dark-brown spots in oats and barley, whitish spots in rye and wheat: Mn
Deficiencies indicated by symptoms appearing first on younger leaves:
- completely yellowish-green leaves with yellowish veins: S
- yellow or pale yellow to white leaves with green veins: Fe
- youngest leaf with white, withered and twisted tip: Cu
- yellowish leaves with brownish spots and/or leaf deformed (part of acidity syndrome): Ca
You'll notice that manganese toxicity and calcium deficiency look the same. It's because when calcium is low, ph is also low and when ph is low, manganese in the soil becomes too readily available to the plant (as well as aluminum) and produces toxicity symptoms.
Also, just because something is missing from the plant, doesn't mean it's missing from the soil. It could be tied up by ph (as iron is unavailable at high ph) or tied up by excess of some other nutrient. Periods of floods can result in short manganese toxicity problems. Droughts can result in a broad spectrum of deficiencies as roots have no soil solution from which to draw nutrients.