Manure Use in Grain Production Systems Josh McGrath & Edwin Ritchey Soil Management Specialists

The 4R’s of Number Two Rate – lower rate might provide higher N return and limit P risk Timing – Fall applied manure provides little N value Placement – Surface application has potential to lose nutrients, tillage has potential to lose soil Source – Still working on this for manure

Manure N is all about the N cycle

Nitrogen Cycle NH3 N2 NO N2O Thermal N2 Fixation Atmospheric Deposition Legumes Volatilization Deposition of plant and animal residue Symbiotic BNF N2 NH3 N2O Denitrification Nitrogen Cycle NO Plant Uptake Deprotonation Non-Symbiotic BNF NO2- Protonation Organic N NO3- NH4+ Mineralization The nitrogen cycle is complex with many forms and rapid transformation between soil pools – many are biologically mediated and therefore hard to predict – spatially and temporally variable Nitrification Immobilization Leaching Sorption Desorption Fixed NH4 (2:1 clays and organic matter)

Manure Nitrogen Cycle Manure contains organic N Some as urea Inorganic N Mostly ammonium Some nitrate Manure Application Manure Nitrogen Cycle Urea Organic N NH4+ Manure N is mostly organic. Dry manures have some ammonium and little nitrate. Liquid manures and biosolids might have more nitrate. During storage manure N is relatively stable – especially dry manure like poultry litter Urea and uric acid in poultry litter make up a large portion of the readily available N. Poultry litter can have 10 – 20 lbs NH4-N/ton. If surface applied some of this will volatilize (depends on temperature, moisture, and wind speed)

Urea in the presence of urease (already in the manure) rapidly hydrolyzes to form ammonium Manure Application Manure Nitrogen Cycle Urea Urease Organic N NH4+ Mineralization In the presence of urease, above ~45 degrees F, urea is rapidly converted to NH4+ N. Really doesn’t get going until about 60F I think. Immobilization

NH3 If not incorporated (rain, tillage, injection) the ammonium can quickly volatilize as ammonia gas Volatilization Manure Application NH3 Manure Nitrogen Cycle Deprotonation Urea Protonation Urease Organic N NH4+ Mineralization When surface applied the NH4-N in the manure and from urea hydrolysis can deprotonate, forming NH3, and volatilize. Incorporation of manure through rainfall, tillage or injection minimizes this loss. Wet manures are subject to much more volatile N loss than dry manures. In coarse textured soils some N can volatilize if only incorporated a couple inches. The objective of manure management is to retain as much N as possible on the soil CEC as NH4 Immobilization

NH3 Ammonium can be rapidly converted to nitrate depending on moisture and temperature Volatilization Manure Application NH3 Manure Nitrogen Cycle Deprotonation Urea Protonation Urease Organic N NO3- NH4+ Mineralization Nitrification is temperature and moisture dependent. Nitrifying bacteria mediate the process. Nitrification Immobilization

Manure Nitrogen Cycle Nitrate readily leaches NH3 Volatilization Manure Application NH3 Manure Nitrogen Cycle Deprotonation Urea Protonation Urease Organic N NO3- NH4+ Mineralization Once N is in the NO3 form it can move with water in the soil profile. Where leaching is a concern this can result in significant loss of N. Nitrification Immobilization Leaching

Manure Nitrogen Cycle Nitrate readily leaches and denitrifies NH3 N2 NO N2O Nitrate readily leaches and denitrifies Volatilization Manure Application N2 NH3 N2O Manure Nitrogen Cycle Denitrification NO Deprotonation Urea NO2- Protonation Urease Organic N NO3- NH4+ Mineralization In anaerobic environments denitrifying bacteria start stealing O from the nitrate and the N can be converted to a gas and lost. Nitrification Immobilization Leaching

Manure Nitrogen Cycle Crops utilize the nitrate and ammonium pools NH3 NO N2O Crops utilize the nitrate and ammonium pools Volatilization Manure Application N2 NH3 N2O Manure Nitrogen Cycle Denitrification NO Plant Uptake Deprotonation Urea NO2- Protonation Urease Organic N NO3- NH4+ Mineralization Crops can utilize N as NO3 or NH4. Advantage: Because organic N in manure is constantly mineralizing during the growing season there are some advantages to manure in that it matches crop uptake requirements. Disadvantage: Because organic N is constantly mineralizing it continues to supply mineral N that can be lost after the growing season is over or before crops start taking up N rapidly. Disadvantage: It’s difficult to predict manure N mineralization. It varies across the field and across time because it’s dependent on soil microbes, soil chemistry, and weather. Nitrification Immobilization Leaching

Spreader calibration

The tarp method is okay – gives general idea The tarp method is okay – gives general idea. You should do a couple passes using centers you are planning on using

Spreader Calibration – Distribution is important -Using pans gives you the rate and distribution. Helps you understand what centers you should use

With manure, splitting might be more important Applying total N with manure will jack up soil P concentrations More complete mineralization of manure N occurs with lower rate The bugs are hungry so they chew on the tough meat Fertilizer at sidedress helps the mineralization process Sidedress allows you time to assess growing season and tweak rate PSNT PSU Agronomy Guide 12 -Applying manure to meet total crop N needs might result in application of 3 – 5 times more P than the crop will utilize. Over time this can result in significant soil P accumulation. P is rather immobile in soil, but once a soil reaches the point of P saturation high dissolved P losses can occur. In addition, P can be lost through erosion of soil particles, which in fields with high STP results in high total P losses. -There is some evidence that with lower manure rates a higher percentage of the total N becomes available in the growing season. This might mean lower total N being available, but it means more efficient use of the N that is applied. -Reserving a portion of the total N planned for an inorganic side-dress application gives you a chance to assess how much N you are getting from your manure. Probably a better estimate than just a pre-application manure test. PSNT -Side-dress also encourages microbial activity resulting in higher mineralization rates and more efficient conversion of manure N to plant available forms.

Pre-sidedress Soil Nitrate Test (PSNT) On fields with a history of manure use or forage legume, early season nitrate is proportional to N availability later in season soil is sampled to a depth of 12 inches corn is 6” to 12” tall portable, easy-to-use meters allow local analysis of soil and rapid delivery of results widely used across NE and Midwest, though interpretations differ by state

0.93 critical level for response 25 mg/kg critical range Magdoff, F.R., W.E. Jokela, G.F. Griffin, and S.D. Klausner. 1992. Predicting N fertilizer needs for corn in humid regions: Advances in the Northeast. p. 29-42 In Predicting N fertilizer needs for corn. Bulletin Y-226. National Fertilizer and Environmental Research Center, Tennessee Valley Authority, Muscle Shoals, AL.

Sidebar on plant sampling

Determining the right rate and timing You’ve got to have a plan…even if it’s not a good one

AGR-146 Plant available N estimates Accounts for ammonia volatilization -UK provides estimates of the proportion of total N in manure available (mineralized) in a growing season. -These estimates account for volatilization.

AGR-146 Plant available N estimates Accounts for denitrification and nitrate leaching -UK provides estimates of the proportion of total N in manure available (mineralized) in a growing season. -These estimates account for volatilization. -And for nitrate leaching and denitrification losses -All of these transformations are very difficult to predict -The longer the manure sits out there the less accurate these estimates are (e.g. fall application) -There are other ways to predict “plant available N” -With fall application or not incorporated you might get much less than what these say -These are just estimates don’t bet on them. -Ultimately adaptive management is required – come up with a plan, assess it, and adjust – constantly

AGR-146 Don’t forget the carry-over -Residual N from previous manure applications is often overlooked, but very important…this is really hard to predict because of the amount of time that has passed since application. PSNT, LCM, check strips, and cornstalk nitrate test all provide means to assess – adaptive management

Field management Managing manure NUE

Methods: Tillage Implements

Management versus source Cumulative P at load from four different tillage practices in SAME corn field Wye Research and Education Center (2006) One field, four tillage treatments, three replicates Same manure rate Same soil test P Same hydrology and slope Very different results Soil Test P = 65 mg kg-1

BMPs are spatially and temporally variable in efficacy Surface applied poultry litter provided a strong P signal in runoff immediately after application in 2006 In subsequent years non- runoff producing rain events preceded first runoff event and there was no treatment effect Tillage on steeper slopes would have likely increased total P loading

Poultry Litter Subsurfer USDA-ARS, Booneville, AR Dale Bumpers Small Farms Research Center

How it works Opening discs open slot Pulverized litter (internal patented mechanism) is delivered to the slot Closing wheels seal the soil surface Can be adjusted to meet a variety of rates Greater accuracy and precision across a range of rates

Auger delivery system This picture shows pellets- they work fine. We’ve had engineering challenges using poultry litter with wood shaving bedding. Currently working on new design that is more “field-read.”

Increased NUE P. Kleinman, USDA-ARS Broadcast treatments were yield limited. Probably by N that did not mineralize or volatilized P. Kleinman, USDA-ARS

Works in heavy cover crop or pasture Does pretty well in heavy residue.

Injection, Instinct, and UAN All plots received 90 lbs pre-plant N per acre from one of three sources Injected ACT with Nitrapyrin Surface applied normal litter Surface applied UAN Side-dressed N at V6 with 0, 45, 90, or 135 lbs/acre Irrigated Included 0 N check and high N preplant (270 lbs/acre) Flat rate of N before planting from three sources. ACT is a “high” N litter. Not much different from standard litter so for point of this example doesn’t matter. Nitrapyrin = Instinct Used 5 way streamers to apply UAN Side-dressed at v6 to get response curve

Injection, Instinct, and UAN Main-plot Treatment Total N (%) NH4-N (%) Organic N (%) PAN (%) PAN (lbs/ton or lbs/gal) Pre-Plant N rate (lbs/acre) Pre-plant Rate (tons/acre or gal/acre) 1 - ACT 3.32 0.68 2.64 2.00 40.06 90 2.25 2 - Normal 3.19 0.70 2.50 1.94 38.87 2.32 3 - 50-UAN   30 3.25 27.69 OrgN= TN – NH4 = 3.32 – 0.68 = 2.64 PAN = 0.5*OrgN + NH4 = 1.32 + 0.68 = 2.00% In the mid-Atlantic we calculate plant available N per ton of manure. This shows application rates of manure and UAN (gal/acre) We applied half the N upfront as ACT or normal litter or UAN We applied the same amount of N upfront, just different amounts of litter Assumes all the NH4-N and ½ half of the organic N is available in the first year

Injection, Instinct, and UAN Highest N recovery from injected PL with nitrapyrin Litter surface applied matched UAN We see a much better response to N with the injected litter and nitrapyrin. Probably early season leaching and more complete mineralization in the soil later in the season. We seemed to run out of N with UAN late in the season.

Less N and same yield

Sidedress needed @ 245 bu/acre Normal litter: 126 lb-N/acre Injected/treated: 42 lb-N/acre Less N and same yield

More yield across all N rates

More yield across all N rates Yield @ sidedress of 100 lb-N/a Normal litter: 243 bu/acre Injected/treated: 259 bu/acre More yield across all N rates

Field Storage of Poultry Litter

Basics Litter should be placed high and dry Push pile up into conical shape Flat spots or humps collect water and degrade litter Keep area around pile as clean as possible Crust formation protects litter Very little N and P are lost Salt accumulation under pile can inhibit crop growth after pile removal

N loss to soil over time (~100 ton pile) Using the standard pile size (i.e., 100-ft long and 18-ft wide) and estimated soil bulk densities, it is possible to estimate the loading rate of N into the soil from the poultry litter pile based on length of time the pile has been in place. For each of the time-of-removal treatments (15-day, 30-day, 45-day, 90-day, 120-day, and 150-day), the following amounts of inorganic N were found in the underlying soil: 4.0, 12.0, 7.6, 9.2, 11.7, and 10.4 pounds, respectively in year 1; and the amounts were 3.4, 8.4, 8.7, 16.1, 13.7, and 15.6 pounds, respectively in year 2. These data suggest that maximum N loading was reached in 30 days in year 1 and 90 days in year 2. Greg Binford, Unpublished

Economic Value of Poultry Litter Tool http://www.uky.edu/Ag/AgEcon/shockley_jordan.php Calculators available for grain crops and pasture, hay, silage Tweak management to see cost/value relationship In reality fall application of poultry litter removes majority of value

Summary Know what you are using (test manure) Know how much you are using (calibrate spreader) Is it worth the price compared to commercial fertilizer – pencil it out Proper field storage is far better (economically and environmentally) than fall application

Josh.mcgrath@uky.edu Follow @NPK_Professor 45