Tissue Test & Find the Nutrient That's Limiting Yield

It compares your leaf-analysis value to the published sufficiency range (a low and a high edge) for your exact crop and growth stage. A value inside the band is sufficient; in the bottom 15% of the band it is flagged low (marginal); below the low edge it is low, and below about 85% of the low edge it is a clear deficiency. Above the high edge it is high, and more than 50% of the band width above is excess (toxicity risk). Every nutrient you enter gets one of those five verdicts.

The limiting nutrient is the one furthest below its sufficiency band — the shortfall capping growth. By Liebig's law of the minimum, yield is set by the scarcest nutrient relative to need, no matter how well-supplied the others are. So the tool ranks all your entered nutrients worst-first and names the single most-limiting one, because correcting it gives the biggest response. Fixing nutrients that are already sufficient does nothing for yield.

The ranges are from SERA-IEG-6 "Reference Sufficiency Ranges for Plant Analysis in the Southern Region of the US" (Southern Cooperative Series Bulletin #394), cross-checked against University of Minnesota Extension and Mosaic Crop Nutrition plant-analysis tables. Macronutrients N, P, K, Ca, Mg and S are in percent dry matter; micronutrients B, Zn, Mn, Fe and Cu are in mg/kg (ppm) dry matter, for the index leaf at the stated growth stage.

Nutrient concentrations in leaves shift as a plant grows — they are usually highest in young tissue and dilute as the plant bulks up. So a value that is sufficient for corn at the V6 whole-plant stage may read low for the ear leaf at silking. Sampling the wrong leaf or the wrong stage shifts the verdict, which is why the tool makes you pick the crop and stage and the ranges adjust accordingly. Always match the dropdown to what your lab actually sampled.

No. Enter only the nutrients your lab reported; leave the rest blank or zero and the tool skips them. It diagnoses and ranks just the nutrients you provide, so a partial lab report (say only N, P, K and Zn) still gives a valid limiting-nutrient verdict among those. Adding more nutrients simply widens the comparison and can reveal a deeper shortfall you had not suspected.

Low is marginal — the value is just under or in the bottom edge of the sufficiency band, so the nutrient is borderline and worth watching or topping up. Deficient means a clear shortfall, below about 85% of the low edge, where visible symptoms and yield loss are likely. Both trigger a corrective-spray suggestion, but a deficient nutrient is the more urgent fix and is more likely to be the overall limiting nutrient.

Yes. A value above the high edge is flagged high, and well above it (more than 50% of the band width over) is excess, which can be toxic or can induce a deficiency of another nutrient — high potassium depressing magnesium uptake is a classic example. The tool counts high and excess nutrients separately so you can spot an imbalance that no amount of the deficient nutrient will fix on its own.

For each deficient or low nutrient the tool names a standard foliar correction — for example foliar urea at 1–2% for nitrogen, Epsom salt (MgSO₄) at 1–2% for magnesium, zinc sulphate at 0.5% buffered with lime for zinc, and Solubor at 0.1–0.2% for boron (which has a narrow safe band). Foliar feeding is a fast top-up; the tool also reminds you to correct the underlying soil supply or pH lock-up so the deficiency does not return.

The built-in table covers twelve crop-and-stage combinations: corn at the V6 whole-plant and ear-leaf-at-silking stages, wheat at boot, rice at tillering, soybean at early pod, cotton at first bloom, tomato at first fruit, potato at early bulking, citrus spring-flush leaf, sugarcane at grand growth, coffee, and banana at flowering. Each has its own full set of macro- and micronutrient ranges for the leaf and stage shown.

A tissue test is the most direct measure of what the plant actually took up, so it is excellent for confirming a suspected deficiency and for ranking which nutrient is limiting. Its accuracy depends on sampling the right leaf at the right stage and handling the sample cleanly. Pair it with a soil test: the leaf says what the plant has, the soil says what is available, and together they tell you whether the cause is supply, pH lock-up or antagonism.

Apply the suggested corrective foliar spray for a fast response, then re-test about 10–14 days later to confirm the value has moved back into the band. At the same time trace the root cause — low soil supply, a pH that locks up the nutrient (high pH locks iron), or an antagonism from an over-applied nutrient — and adjust the season's program so the deficiency does not recur next sampling.

No. A soil test measures what is available in the ground and drives fertilizer rates before or at planting; a tissue test measures what the growing crop has actually accumulated and is used in-season to diagnose and fine-tune. This tool is the tissue-test side — it interprets leaf numbers. For converting soil-test ppm into fertilizer rates, use a soil-test recommendation tool instead.

No. Everything runs in your browser — your leaf-analysis numbers are never sent anywhere, stored, or uploaded. You can paste a full lab report, read the diagnosis, copy the plain-text summary, and close the tab with nothing retained. That makes it safe to use with confidential agronomy data from a paid lab.