Tim Shaver & Richard Ferguson University of Nebraska-Lincoln

 C, H, O = 95% of plant weight  N, P, K = Primary (macro) nutrients  Ca, Mg, S = Secondary nutrients  Micro-nutrients = B, Cu, Fe, Mn, Mo, Zn, Cl

 Mass Flow ◦ Dissolved nutrients in water flowing toward the root. ◦ Soluble and abundant elements (N, Ca, Mg, S)  Diffusion ◦ Movement of nutrients from an area of high concentration to an area of low concentration ◦ Low concentration area created by active uptake of nutrients at the root (K and P)  Interception ◦ Root growth explores new soil regions

 N is the most frequently deficient nutrient in crop production.  The ultimate source of N is N 2 gas, which is 78% of the earth’s atmosphere.  Higher plants cannot metabolize N 2, therefore, N 2 must be converted to plant available N.

 N 2 can be converted to plant available forms through several processes: ◦ Symbiotic microorganisms (legumes) ◦ Non-symbiotic microorganisms ◦ Lightning (electrical discharges) forming N oxides ◦ Synthetic manufacture (N fertilizers) Plant available forms: Nitrate (NO 3 - ) Ammonium (NH 4 + )

 1) Atmospheric, plant, & animal residue N is added to the soil.  2) Organic N in residue is mineralized to NH 4 + by soil organisms (mineralization).  3) Most NH 4 + is converted to NO 3 - by nitrifying bacteria (nitrification).  4) NH 4 + and NO 3 - are taken up by plants.  5) Various loss mechanisms

 Used in the formation of proteins which provide the framework for plant structures in which biochemical reactions occur.  N is an integral part of chlorophyll (photosynthesis).  N is associated with high photosynthetic activity, vigorous growth, and dark green color.

 Generally stunted, and yellow in appearance.

 Anhydrous Ammonia: ◦ NH 3 + 2O 2 H + + NO H 2 O  Urea: ◦ (NH 2 ) 2 CO + 4O 2 2H + + 2NO CO 2 +H 2 O  Ammonium Nitrate: ◦ NH 4 NO 3 + 2O 2 2H+ + 2NO H 2 O

 Monoammonium Phosphate: ◦ NH 4 H 2 PO 4 + O 2 2H + + NO H 2 PO 4 - +H 2 O  Diammonium Phosphate: ◦ (NH 4 ) 2 HPO 4 + O 2 3H + + 2NO H2PO H 2 O

 Phosphorus is an essential plant nutrient ◦ Energy Transfer (ATP) ◦ Good Supply of P  Increased root growth  Early maturity  Greater straw strength in cereals Phosphorus:

 Second most important nutrient for crop growth ◦ Lower need than N  P is a relatively immobile nutrient  Fewer loss mechanisms in the environment than N  Can become unavailable in the soil. Band application on winter wheat

 Monoammonium Phosphate: ◦ NH 4 H 2 PO 4 + O 2 2H + + NO H 2 PO 4 - +H 2 O  Diammonium Phosphate: ◦ (NH 4 ) 2 HPO 4 + O 2 3H + + 2NO H2PO H 2 O

 Stunted in Growth  Abnormal dark-green color  Reddish -purple color (Severe deficiency symptom) ◦ Often seen in early spring on low phosphorus sites. ◦ Often as soils warm, phosphorus deficiency symptoms disappear.

 Essential plant nutrient  Next to nitrogen, crops absorb more K than any other nutrient  Soil K is related to soil minerals (feldspar, mica) and not organic matter like N and P  Western Nebraska has high quantities of K due to the mineral makeup of the soil and climate (low weathering).

 Depending on soil type, 90 to 98% of K is in relatively unavailable forms.  Over time, soil minerals weather, slowly releasing K to more plant available forms.  Absorbed by roots as K + ion.  Responsible for enzyme activation and water uptake (osmotic “pull”).

 Potassium chloride (KCL)  Potassium sulfate (K 2 SO 4 )  Potassium magnesium sulfate (K 2 SO 4 MgSO 4 )  Potassium nitrate (KNO 3 )  Nebraska soils with 125ppm or greater considered sufficient.

 Urea Example: ◦ (NH 2 ) 2 CO ◦ Molecular Weight (from periodic table) :  N = 14(2)=28  H = 1(4)=4  C = 12(1)=12  O = 16(1)=16 60 N = 28/60 = 46%

 Efficient N fertilizer use requires that credit is given for sources of N already available in the soil. ◦ Residual Nitrate (NO 3 ) ◦ Organic Matter Mineralization ◦ Organic Materials (Manure) ◦ Previous Crop (Legumes) ◦ Irrigation (NO 3 Content) Nitrogen cycle (source:

 Nitrogen fertilizer rates can be substantially reduced by accounting for N Credits.  N credits can vary widely. ◦ Deep soil sampling ◦ Material analysis ◦ Previous crop credit ◦ Irrigation water sampling Soil scientist uses hydraulic probe to extract soil samples (Photo courtesy of USDA NRCS).

 Nitrogen rates can be determined using UNL Extension publications specifically written for individual crops.  These publications are located at:

 UNL recommendations can be determined from tables or from equations (corn example, In: EC117):

 UNL Corn N Recommendation Algorithm: ◦ N need (lb/ac): 35 +(1.2 x EY) -(8 x N ppm) -(0.14 x EY x OM) -credits [35+(1.2xEY)-(8xNO 3 -Nppm)-(0.14xEYxOM)-credits] Photo courtesy of USDA NRCS

 Algorithm Example: ◦ Expected Yield (EY) = 200 bu/ac; OM = 2% ◦ Soil Nitrate (Surface 8 inches) = 5 ppm [35+(1.2xEY)-(8xNO 3 -Nppm)-(0.14xEYxOM)-credits] 35 +(1.2 x EY(200)) = 240 -(8 x N ppm(5))= 40 -(0.14 x EY(200) x OM%(2)) = – 40 – 56 = 179 lbs N/ac Photo courtesy of USDA NRCS

 N Credits: ◦ Previous Soybean: 45 lbs/ac ◦ Previous Alfalfa: 150 lbs/ac (70-100% stand) 120 lbs/ac (30-69% stand) 90 lbs/ac (0-29% stand) ◦ Water: 1 ppm N = 2.7 lbs/ac *Photos courtesy of USDA NRCS

 N Credit Example: ◦ Previous Crop: Soybean (45 lbs/ac) ◦ Water: 3 ppm (3 x 2.7 = 8 lbs/ac) ◦ N recommendation: 179 lbs/ac ◦ N Credits: = 53 lbs/ac ◦ N recommendation (credits): 126 lbs/ac ◦ Table recommendation: 155 – 180 lbs/ac Photo courtesy of USDA NRCS

 Using the UNL N algorithm calculate the recommended amount of N for corn using the following information: ◦ Expected Yield 190 bu/ac ◦ Residual Soil N = 8 ppm ◦ Organic Matter = 2.0% ◦ Previous Crop = Soybean ◦ Irrigation water N content = 5 ppm

Tim Shaver Nutrient Management Specialist UNL WCREC

 N, P, K = Primary (macro) nutrients  Ca, Mg, S = Secondary nutrients  Micro-nutrients = B, Cu, Fe, Mn, Mo, Zn, Cl  Zn, Fe, and Sulfur most common deficiencies in NE.

 Soil minerals  Soil organic matter  Crop residue  Manures/organic amendments  Fertilizers, Pesticides  Irrigation water  The atmosphere

 Corn and dry beans sensitive  Other crops more tolerant  Deficiency expression ◦ Stunted crop, short internodes ◦ Reduced chlorophyll production ◦ Striping on corn leaves ◦ Often seen early in season then visual symptoms may disappear

 Water solubility controls fertilizer Zn availability (40 to 50% required) ◦ ZnSO 4, Lignosulfonate, ZnEDTA are best  ZnEDTA is 2 to 5 X more effective than other high water soluble sources.

 Wide spread problem from western US to Iowa  Lack of chlorophyll caused by plant’s inability to take up Fe from soil  Severity depends on crop & soil  Major problem of lawns and gardens

Fe Deficient Corn

◦ FeSO 4 ·7H 2 O ◦ Foliar – 1% FeSO 4 ·7H 2 O solution ◦ FeEDDHA ◦ Oxysulfates, FeGels, FeSO 4 ·H 2 O  Look for cheaper sources of by-product ferrous sulfate  Foliar a last resort

 S is a secondary nutrient  Required for protein formation  Deficiencies primarily on sandy soils  Early season deficiency more common with cool, wet soils (no or reduced till, high water table, river valleys)

 Sulfates ◦ (24% S) ◦ K or K-Mg sulfates (18% S) ◦ CaSO 4 (16-18% S) ◦ ZnSO 4 (14% S) ◦ Phosphates ( {15%}: newer have low S)  Thiosulfates ◦ S (ATS) ◦ S (KTS)  Elemental S ◦ 90% - 99% S depending on granulation

 Fertilizer placement options generally involve surface or subsurface applications.  This depends on: ◦ Crop and crop rotation ◦ Soil test level ◦ Mobility in the soil ◦ Equipment availability Using Global Position System equipment for precision application of fertilizer. (Photo courtesy of USDA NRCS).

Pre-plant:  Band: ◦ Surface (Dribble) ◦ Subsurface (Knife)  Broadcast: ◦ Surface ◦ Incorporated Nutrient Applicator (Source:

 At Planting:  Band ◦ Surface ◦ Subsurface  Below and to side of seed ◦ Starter (pop up) Application of anhydrous ammonia fertilizer at planting time (Photo courtesy of USDA NRCS).

After Planting  Sidedressing ◦ Anhydrous ◦ Fluid Sources (UAN)  Surface and Subsurface  Topdress ◦ Solid and Liquid Sources Nitrogen being applied to growing corn (Photo courtesy of USDA NRCS).