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

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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 78% of the earth’s atmosphere.

gas, which is  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 + organisms (mineralization).

by soil  3) Most NH 4 + (nitrification).

is converted to NO 3 - by nitrifying bacteria  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 3 + H 2 O  ◦ Urea: (NH 2 ) 2 CO + 4O 2 2H + + 2NO 3 + CO 2 +H 2 O  ◦ Ammonium Nitrate: NH 4 NO 3 + 2O 2 2H+ + 2NO 3 + H 2 O

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

Phosphorus:



Phosphorus is an essential plant nutrient

◦ ◦ Energy Transfer (ATP)    Good Supply of P Increased root growth Early maturity Greater straw strength in cereals

Band application on winter wheat  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.

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

Nitrogen cycle (source: http://www.epa.gov) ◦ ◦ ◦ ◦ ◦ Residual Nitrate (NO 3 ) Organic Matter Mineralization Organic Materials (Manure) Previous Crop (Legumes) Irrigation (NO 3 Content)

  Nitrogen fertilizer rates can be substantially reduced by accounting for N Credits.

N credits can vary widely.

Soil scientist uses hydraulic probe to extract soil samples (Photo courtesy of USDA NRCS).

◦ ◦ ◦ ◦ Deep soil sampling Material analysis Previous crop credit Irrigation water sampling

 Nitrogen rates can be determined using UNL Extension publications specifically written for individual crops.

 These publications are located at: http://www.ianrpubs.unl.edu

 UNL recommendations can be determined from tables or from equations (corn example, In: EC117): Soil Nitrate ppm 1 3 6 9 12 18 24 60 90 120 Yield Goal (bu/ac) 150 180 210 240 270 Organic Matter 1% Recommended N rate based on soil N, yield goal and soil organic matter (lb N/acre) 90 75 120 105 155 140 185 170 220 200 250 235 280 265 315 295 50 25 5 0 0 80 60 35 0 0 115 90 65 20 0 145 120 100 50 0 180 155 130 80 35 210 185 160 115 65 240 215 195 145 95 275 250 225 175 130

 UNL Corn N Recommendation Algorithm: Photo courtesy of USDA NRCS ◦ 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]

 ◦ ◦ 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)) = 56 35 + 240 – 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: 45 + 8 = 53 lbs/ac Photo courtesy of USDA NRCS ◦ ◦ N recommendation (credits): 126 lbs/ac Table recommendation: 155 – 180 lbs/ac

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

◦ ◦ ◦ ◦ 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 21-0-0 (24% S) K or K-Mg sulfates (18% S) CaSO 4 (16-18% S) ZnSO 4 (14% S) Phosphates (16-20-0{15%}: newer have low S)  ◦ ◦ Thiosulfates 12-0-0-26S (ATS) 0-0-25-17S (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) Nutrient Applicator (Source: http://www.deere.com)  ◦ ◦ Broadcast: Surface Incorporated

 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).