ACS CCN1 cheat sheet

Essential macronutrients: N, P, K, Ca, Mg, S; micronutrients: B, Cl, Cu, Fe, Mn, Mo, Ni, Zn.

Law of the Minimum: yield is limited by the most deficient essential nutrient, not by total nutrient supply.

Cation exchange capacity (CEC) is the sum of exchangeable cations a soil can hold, expressed in cmol(+)/kg or meq/100 g.

Base saturation = (sum of exchangeable basic cations ÷ CEC) × 100; Ca, Mg, K, Na are the basic cations.

Liebig-type sufficiency ranges: below critical level = deficiency; above = luxury consumption or toxicity risk.

Soil pH governs nutrient availability: P and most micronutrients are most available near pH 6.0–6.8 for mineral soils.

Mobile nutrients (N, K, Mg) show deficiency first in older leaves; immobile nutrients (Ca, Fe, B) in younger leaves.

CEC is dominated by clay type and organic matter: humus and smectite hold far more cations than kaolinite or sand.

Fertilizer grade N-P2O5-K2O is a percentage by weight; elemental P = %P2O5 × 0.44 and elemental K = %K2O × 0.83.

Urea (46-0-0) hydrolyzes to ammonium and is subject to volatilization loss if not incorporated or rained in.

Anhydrous ammonia (82-0-0) is a high-analysis N source requiring injection and soil sealing to prevent loss.

DAP (18-46-0) and MAP (11-52-0) supply both N and P; MAP is acidic, DAP is slightly alkaline in reaction.

Ammonium nitrate (34-0-0) supplies half nitrate and half ammonium N and is a regulated oxidizer material.

Limestone raises pH; its neutralizing value depends on CaCO3 equivalence and fineness of grind.

Gypsum (CaSO4·2H2O) adds Ca and S without raising pH and can help displace excess sodium.

Manure and compost nutrient content varies widely; analysis is required before crediting N-P-K to a nutrient budget.

A representative soil sample is a composite of 15–20 subsamples from a uniform management zone, typically 0–6 or 0–8 inches for row crops.

Soil test P and K are reported as extractable concentrations (ppm) and converted to lbs/acre using the 2-million-lb furrow slice: ppm × 2 = lb/acre.

Soil test correlation and calibration relate test levels to crop response and to fertilizer recommendation rates.

Plant tissue sampling should target a defined plant part and growth stage; results are interpreted against sufficiency ranges for that stage.

Tissue analysis complements soil tests by revealing nutrient uptake and antagonisms (e.g., high K suppressing Mg).

Soil pH, buffer pH, and lime requirement are distinct: buffer pH estimates the amount of lime needed to reach a target pH.

Nitrate-N in the root zone can be used for pre-sidedress or presidedress nitrogen testing to adjust in-season N rates.

Sampling depth and timing must be consistent across years to allow valid trend comparison of soil test values.

A nutrient management plan sets realistic yield goals, credits all sources (soil, manure, legume, irrigation), and matches applications to crop uptake.

Right rate, right source, right time, right place (4Rs) is the core decision framework for nutrient stewardship.

Banding and knifing place fertilizer below the surface near roots, improving P and K efficiency over broadcast.

Split or sidedress N applications reduce leaching and denitrification risk compared with a single large preplant application.

Starter fertilizer should be placed away from the seed (e.g., 2×2) to limit salt injury and ammonia toxicity.

Legume N credit: a preceding alfalfa or soybean crop supplies N that must be subtracted from the planned fertilizer rate.

Application rate = (target nutrient rate) ÷ (fraction of nutrient in the material), adjusted for any nutrient credits.

Fertigation and variable-rate application use soil and crop data to match nutrient supply to spatially variable demand.

Nitrogen loss pathways: leaching of nitrate, denitrification (N2, N2O), volatilization of ammonia, and erosion of sediment-bound N and P.

Phosphorus loss is driven mainly by erosion and runoff of particulate P and by dissolved P in surface flow.

Nitrification inhibitors slow ammonium-to-nitrate conversion, reducing leaching and denitrification risk.

Urease inhibitors delay urea hydrolysis, reducing ammonia volatilization when urea cannot be incorporated promptly.

Cover crops and buffer strips reduce nitrate leaching and trap sediment-bound P before it reaches water bodies.

Applying N below the crop's immediate need and avoiding fall application in high-leaching environments reduce nitrate loss.

Soil test P above the agronomic critical level indicates elevated risk of dissolved P loss in runoff.

N2O is a potent greenhouse gas; denitrification from excess nitrate and saturated soils is a major agricultural source.

Nitrogen drives vegetative growth and protein; excess N can delay maturity, reduce lodging resistance, and lower sugar or quality in some crops.

Potassium improves stalk strength, drought tolerance, and fruit quality; K demand peaks during reproductive growth.

Phosphorus is critical at early establishment for root development and is most efficiently applied near the seed zone.

Sulfur deficiency is increasingly common; it affects protein synthesis and is required for oilseed and legume crops.

Boron and calcium are immobile in plants; deficiency appears in new growth and can cause fruit disorders such as blossom-end rot.

Late-season N or K management in high-value crops can affect quality attributes such as sugar content, firmness, and storage life.

Legumes fix N via rhizobia; inoculation and adequate P, K, S, and micronutrients support nodulation and N fixation.

Yield goal setting should be based on realistic yield history and site potential, not on maximum recorded yields.

Anhydrous ammonia is a hazardous compressed gas; handling requires training, PPE, and emergency response procedures.

Ammonium nitrate is an oxidizer regulated for storage security and quantity limits; it can support combustion.

Fertilizer storage areas should be separated from pesticides, fuels, and water sources, and kept dry and ventilated.

Nutrient management plans must comply with applicable state and federal rules, including concentrated animal feeding operation requirements.

Professional ethics require recommendations based on sound science, disclosure of conflicts of interest, and accurate record keeping.

Fertilizer labels and guarantees are legally binding; misbranding or misrepresenting nutrient content is prohibited.

Pesticide and fertilizer application near water, wells, and sensitive areas must follow setback and buffer requirements.

Report spills and releases according to regulatory requirements and maintain current safety data sheets for stored materials.

Economic optimum N rate (EONR) is the rate where the marginal cost of the last unit of N equals the marginal value of the resulting yield.

Partial budget analysis compares added returns and added costs of a nutrient management change.

Field records should capture field ID, crop, yield, nutrient source, rate, timing, method, and weather conditions at application.

Nutrient use efficiency (NUE) = crop nutrient uptake ÷ nutrient supplied; higher NUE indicates less loss per unit produced.

Fertilizer cost per unit nutrient = (material price per ton) ÷ (lb nutrient per ton ÷ 2000).

Decision support tools include soil test calibration databases, nutrient budget spreadsheets, and variable-rate prescription software.

Multi-year records allow trend analysis of soil test values and help evaluate whether nutrient balance is positive or negative.

Return on investment of fertilizer is evaluated against yield response curves, not against the absolute cost of the material.

Domain 9 overlaps with Domain 7 in this exam outline; see Domain 7 for regulatory, safety, and ethics content.

Anhydrous ammonia requires pressure-rated equipment and trained operators due to its toxic and corrosive properties.

Ammonium nitrate storage must address fire and oxidizer hazards and may be subject to quantity and security rules.

Fertilizer storage should prevent runoff and contamination of surface and groundwater.

Nutrient management plans must comply with applicable state and federal requirements.

Ethical recommendations are based on sound science, disclose conflicts, and avoid overrecommending nutrients.

Fertilizer guarantees on labels are legally enforceable.

Setback and buffer requirements protect water and sensitive areas during application.