III. FERTILIZER NUTRIENTS FROM LIVESTOCK MANURE

The following documentation shows how the estimates were derived from Census of Agriculture data. The objective is to derive an estimate of the average livestock numbers over the Census year (1992), multiply it by an amount of manure specific to each type of livestock, and multiply the result by an estimate of the average nutrient content of the specified manure.

The Census numbers do not provide for an average inventory of livestock; the inventory variable in the Census files is for the inventory on December 31. Thus, the average livestock numbers were derived from a combination of sales over the year and end-of-year inventory (if both were available) or from either sales or inventory if only one value was available. This allowed for manure credit estimates on those farms that raise livestock only sporadically during the year (with no inventory on December 31) or that ceased production during the Census year.

The formulae are shown here in programming style (K810-K812 means the value of variable K810 minus the value for the variable K812). The naming conventions are:

1. Kxxx refers to a variable for the unpublished Census file, i.e., farm level data. The number xxx refers to the 3 digit variable ID number shown in the Census questionnaire (see the Appendix in any State Census report). The results of the query will be subject to the standard disclosure screens; this probably will result in county-level data for those ('selected') counties with sufficient farms of any given type to avoid disclosure problems. The data for the remaining counties would then be aggregated into a 'rest of state' category.
2. d_xxxxxx refers to a variable in the published Census report, i.e., a county total. This file is accessed through the INFORMIX SQL structure; the SQL statements are not shown specifically but can be easily derived from the information given. This file includes all counties; however, any information that was suppressed in the publication will be 'computed' as zero. This file will be used to derive the initial set of draft numbers for the ASM and HUMUS model runs for the October 1 deadline.

3. In the manure nutrient equations (beef_n etc.), the documentation is consistently shown in the format:

   cow_n = cowinv*11.5*3.3 which means:

   [the pounds of nitrogen generated by beef cows] = [the inventory of beef cows in AU] * [11.5 i.e.,. the number of tons of manure produced by one AU of beef cows in one year] * [3.3 i.e.,. the number of pounds of nitrogen contained in 1 ton of beef cow manure]

   The manure and nutrient values used in this equation were taken from Table A-8. The manure nutrient content values used were those that accounted for nutrient losses during storage (after losses), not as the excreted values.

4. The values for 'state recovery factor for Kxxx' are not listed specifically here, they vary by state and type of livestock. These values were derived by Chuck Lander and David Moffitt from published data and a survey of NRCS and other knowledgeable staff. These numbers (in effect) show the ratio of confined production by type of livestock by state.

To show how these computations work, we use a hypothetical farm in a mythical county in Pennsylvania⁶. This farm has an inventory on December 31 of 100 dairy cows, 200 beef cows (where both beef and dairy cows have associated calves and yearlings as shown below), 100 sows, 500 pigs on feed, 1,000 layers, 25,000 broilers, and 100 turkeys. Further, the farm has sales during the year of 90 head of cattle (of which 50 were fed cattle), 20 sows, 800 hogs and pigs (of which 100 were feeder pigs for further feeding), 100 layers, 75,000 broilers, 10 turkey hens, and 300 fed turkeys.

A. Cattle

The Census has two inventory variables that we need to disaggregate, namely K806 (heifer and heifer calves) and K807 (steers and bulls of all ages). We need to partition the sum of K806 and K807 into: 1) young calves (calving to roughly 425 lbs), 2) cattle grass-fed (primarily heifers and steers between roughly 425 and 650 lbs), 3) heifers being raised for herd replacement (raised from roughly 650 lbs to full weight), 4) feedlot animals (fed from roughly 650 lbs to market weight), and 5) bulls. This partition assumed:

• a 90 percent calving rate
• an equal split between heifer and bull calves
• a 15 percent replacement rate (annual) for beef cows
• a 20 percent replacement rate (annual) for dairy cows
• in the absence of any data about bull numbers, the inventory of bulls is included with the grass-fed animal numbers and the sales component for bulls is included with the beef cow sales.

A1. Young Calves

i. Beef

assume 4 calves per AU produced per year K804*0.9

assume 5 months on feed (but only 1 cycle per year)

No if calfbinv=K804*0.9*(5/12)/4

manure nutrients (in lbs)

calfb_n = calfbinv*10.59*3.3

calfb_p = calfbinv*10.59*2.86

calfb_k = calfbinv*10.59*7.08

recoverable nutrients = calfb_{N,P,K} * (state recovery factor for K804)

Shortcut for input number for ASM/HUMUS:

calfbinv=(d_140020*0.9*5)/(12*4)

then proceed as above.

Example:

200 beef cows 90 percent calving ratio 5 months in 'young calf' status

4 young calves per AU 10.59 tons manure per AU 3.3 lbs N per ton manure

5 percent of manure recoverable (produced in confinement)

calfb_n=(200*0.9*5*10.59*3.3*0.05)/(12*4) = 32.76 lbs of N

ii. Dairy

assume 4 calves per AU produced per year K805*0.9

assume 5 months on feed (but only 1 cycle per year)

No if calfdinv = K805*0.45*(5/12)/4

manure nutrients (in lbs)

calfd_n = calfdinv*10.59*3.3

calfd_p = calfdinv*10.59*2.86

calfd_k = calfdinv*10.59*7.08

recoverable nutrients = calfd_{N,P,K} * (state recovery factor for K805)

Shortcut for input number for ASM/HUMUS:

calfdinv=(d_140036*0.45*5)/(12*4)

then proceed as above.

Example:

100 dairy cows 90 percent calving ratio 5 months in 'young calf' status

4 young calves per AU 10.59 tons manure per AU 3.3 lbs N per ton manure

80 percent of manure recoverable (produced in confinement)

calfd_n=(100*0.45*5*10.59*3.3*0.8)/(12*4) = 131.05 lbs of N

A2. Grass-Fed Cattle

Computed from the number of beef and dairy cows (to take the calves through the next step in the cycle). The number is also used to account for bulls (roughly 5 percent of cow inventory), because the ratio of feeders to cows is likely closer to 80 percent, than the 90 percent asserted here. The difference is intended to account for the manure production from bulls for the full year, rather than the 100 days specified here.

i. Beef

assume 1.82 animals per AU

produced per year 0.9*(K804)

sales ignore the sales data (K808 would include resale)

assume 100 days duration (but only 1 cycle per year)

No if grassinv= 0.9*(K804)*(100/365)/1.82

manure nutrients (in lbs)

grass_n = grassinv*12.05*1.82

grass_p = grassinv*12.05*1.1

grass_k = grassinv*12.05*4.53

recoverable nutrients = grass_{N,P,K} * (state recovery factor for K804)

Shortcut from published Census:

grassinv= 0.9*(d_140020)*(100/365)/1.82

then proceed as above.

Example:

200 beef cows 90 percent calving ratio

5 months in 'young calf' status 1.82 animals per AU 11.32 tons manure per AU

2.56 lbs N per ton manure

5 percent of manure recoverable (produced in confinement)

grass_n=(200*0.9*100*11.32*2.56*0.05)/(365*1.82) = 39.26 lbs of N

ii. Dairy

assume 1.82 animals per AU

produced per year 0.45*(K805)

sales ignore the sales data (K808 would include resale)

assume 100 days duration (but only 1 cycle per year)

No if grassinv= 0.45*(K805)*(100/365)/1.82

manure nutrients (in lbs)

grass_n = grassinv*12.05*1.82

grass_p = grassinv*12.05*1.1

grass_k = grassinv*12.05*4.53

recoverable nutrients = grass_{N,P,K} * (state recovery factor for K804)

Shortcut for number from published Census:

grassinv= 0.45*(d_140036)*(100/365)/1.82

then proceed as above.

Example:

100 dairy cows 45 percent calving ratio (accounting for veal sales)

5 months in 'young calf' status 1.82 animals per AU 12.05 tons manure per AU

1.82 lbs N per ton manure

5 percent of manure recoverable (produced in confinement)

grass_n=(100*0.45*100*12.05*1.82*0.05)/(365*1.82) = 7.43 lbs of N

A3. Calves Raised for Breeding Herd:

i. Beef

assume 1.14 calves per AU

needed per year K804*0.15

assume 5 months on feed (but only 1 cycle per year)

No if heifbinv=K804*0.15*(5/12)/1.14

manure nutrients (in lbs)

heifb_n = heifbinv*12.05*1.82

heifb_p = heifbinv*12.05*1.1

heifb_k = heifbinv*12.05*4.53

recoverable nutrients = heifb_{N,P,K} * (state recovery factor for K804)

Shortcut for input number for ASM/HUMUS:

heifbinv=(d_140020*0.15*5)/(12*1.14)

then proceed as above.

Example:

200 beef cows 15 percent replacement rate 5 months in 'heifer' status

1.14 animals per AU 12.05 tons manure per AU 1.82 lbs N per ton manure

5 percent of manure recoverable (produced in confinement)

heifb_n=(200*0.15*5*12.05*1.82*0.05)/(12*1.14) = 12.02 lbs of N

ii. Dairy

assume 0.94 calves per AU

needed per year K805*0.2

assume 5 months on feed (but only 1 cycle per year)

No if heifdinv = K805*0.2*(5/12)/0.94

manure nutrients (in lbs)

heifd_n = heifdinv*12.05*1.82

heifd_p = heifdinv*12.05*1.1

heifd_k = heifdinv*12.05*4.53

recoverable nutrients = heifd_{N,P,K} * (state recovery factor for K805)

Shortcut for input number for ASM/HUMUS:

heifdinv=(d_140036*0.2*5)/(12*0.94)

then proceed as above.

Example:

100 dairy cows 20 percent replacement rate 5 months in 'heifer' status

0.94 animals per AU 12.05 tons manure per AU 1.82 lbs N per ton manure

80 percent of manure recoverable (produced in confinement)

heifb_n=(100*0.2*5*12.05*1.82*0.8)/(12*0.94) = 155.54 lbs of N

A4. Cattle on Feed:

assume 1.14 animals per AU

sales K812

assume 140 days on feed (= 2.5 cycles per year)

No if beefinv = K812/(1.14*2.5)

manure nutrients (in lbs)

beef_n = beefinv*10.59*4.39

beef_p = beefinv*10.59*2.86

beef_k = beefinv*10.59*7.08

recoverable nutrients = beef_{N,P,K} * (state recovery factor for K812)

Shortcut for input number for ASM/HUMUS:

beefinv=(d_140137)/(2.5*1.14)

then proceed as above.

Example:

50 fed cattle sold 140 days in feedlot

1.14 animals per AU 10.59 tons manure per AU 4.39 lbs N per ton manure

85 percent of manure recoverable (produced in confinement)

beef_n=(50*140*10.59*4.39*0.85)/(365*1.14) = 664.78 lbs of N

A5. Breeding Herd

i. Beef Cows:

assume 1 cow per AU

inventory, cows K804 AU inventory K804

sales, cows K810-K812 AU sales K810-K812

assume 365 days on feed (continuous replacement)

If K804>0 and K810-K812=0 then cowinv=K804

If K804=0 and K810-K812>0 then cowinv=K810-K812

If K804>0 and K810-K812>0 then cowinv=(K804+K810-K812)/2

manure nutrients (in lbs)

cow_n = cowinv*11.5*3.3

cow_p = cowinv*11.5*3.23

cow_k = cowinv*11.5*7.44

recoverable nutrients = cow_{N,P,K} * (state recovery factor for K804)

Shortcut for input number for ASM/HUMUS:

cowinv= d_140020 then proceed as above.

Example:

90-50=40 head (non-fed) cattle sold 20 cows in inventory

full year in feedlot 1.0 animals per AU

11.5 tons manure per AU 3.3 lbs N per ton manure

5 percent of manure recoverable (produced in confinement)

average inventory=(20+90-50)/2 =30

cow_n=(30*1*11.5*3.3*0.05)/(1*1) = 56.92 lbs of N

ii. Dairy Cows:

assume 0.74 dairy cows per AU

inventory, dairy K805 AU inventory K805/0.74

There is no sales variable for dairy cows. Dairy cows are 'sold' via K810-K812, thus the related manure is computed as though this were a beef cow.

assume 365 days on feed (continuous replacement)

No if dairinv=K805/0.74

manure nutrients (in lbs)

dair_n = dairinv*15.24*4.3

dair_p = dairinv*15.24*1.65

dair_k = dairinv*15.24*6.04

recoverable nutrients = dair_{N,P,K} * (state recovery factor for K805)

Shortcut for input number for ASM/HUMUS:

dairinv=d_140036/0.74

then proceed as above.

Example:

20 cows in inventory full year in feedlot

0.74 animals per AU 15.24 tons manure per AU

4.3 lbs N per ton manure

85 percent of manure recoverable (produced in confinement)

dair_n=(20*1*15.24*4.3*0.85)/(1*0.74) = 1505.46 lbs of N

B. Hogs

B1. Hogs for Breeding

assume 2.67 sows per AU

inventory, sows K816 AU inventory K816/2.67

There is no variable in the census that identifies the number of sows sold; they are included in 'hogs and pigs sold' other than 'feeder pigs'. Because the vast majority of animals in this category are hogs for slaughter, we cannot estimate the sales of sows. So the computations have to proceed on the inventory variable by itself. No big problem, because the number of sows is likely to be quite constant over time (except for the farm that sells out - in which case the manure will be computed as for fed hogs below).

assume 365 days on feed (continuous replacement)

No if sowinv=K816/2.67

manure nutrients (in lbs)

sow_n = sowinv*6.11*3.32

sow_p = sowinv*6.11*3.62

sow_k = sowinv*6.11*7.04

recoverable nutrients = sow_{N,P,K} * (state recovery factor for K816)

Shortcut for input number for ASM/HUMUS:

sowinv=d_150018/2.67

then proceed as above.

Example:

100 sows in inventory

full year in feedlot 2.67 animals per AU

6.11 tons manure per AU 3.32 lbs N per ton manure

80 percent of manure recoverable (produced in confinement)

sow_n=(100*1*6.11*3.32*0.8)/(1*2.67) = 607.8 lbs of N

B2. Hogs on Feed  

assume 9.09 hogs per AU

inventory, hogs K817 AU inventory K817/9.09

sales, hogs K820-K822 AU sales (K820-K822)/9.09

assume 180 days on feed (= 2 cycles per year)

If K817>0 and (K820-K822)=0 then fhoginv=K817/9.09

If K817=0 and (K820-K822)>0 then fhoginv=(K820-K822)/(2*9.09)

If K817>0 and (K820-K822)>0 then fhoginv=(K817+(K820-K822)/2)/(2*9.09)

manure nutrients (in lbs)

fhog_n = fhoginv*14.69*2.82

fhog_p = fhoginv*14.69*2.8

fhog_k = fhoginv*14.69*7.16

recoverable nutrients = fhog_{N,P,K} * (state recovery factor for K817)

Shortcut for input number for ASM/HUMUS:

fhoginv=(d_150024+(d_150032-d_150049)/2)/(2*9.09)

with an adjustment in those counties where sales information was not disclosed then proceed as above.

Example:

500 'other hogs and pigs' (not used for breeding) in inventory

800 hogs and pigs sold (of which 100 were feeder pigs for further feeding)

six months in feedlot 9.09 animals per AU

14.69 tons manure per AU 2.82 lbs N per ton manure

80 percent of manure recoverable (produced in confinement)

avg. inventory = (500 +(800-100)/2)/2 = 425

fhog_n=(425*1*14.69*2.82*0.8)/(1*9.09) = 1549.48 lbs of N

C. Layer Chickens

C1. Hens - layers

assume 250 layers per AU

inventory, layers K892 AU inventory K892/250

sales, layers K893 AU sales K893/250

assume 365 days on feed (= continuous replacement)

If K892>0 and K893=0 then layerinv=K892/250

If K892=0 and K893>0 then layerinv=K893/250

If K892>0 and K893>0 then layerinv=(K892+K893)/(2*250)

manure nutrients (in lbs)

layer_n = layerinv*11.45*18.46

layer_p = layerinv*11.45*8.5

layer_k = layerinv*11.45*9.4

recoverable nutrients = layer_{N,P,K} * (state recovery factor for K892)

Shortcut for input number for ASM/HUMUS:

layerinv=(d_160005+d_160031)/(2*250)

then proceed as above.

Example:

1,000 layers in inventory 100 layers sold

continuous replacement

250 animals per AU 11.45 tons manure per AU

18.46 lbs N per ton manure

95 percent of manure recoverable (produced in confinement)

avg. inventory = (1,000 +100)/2 = 550

layer_n=(550*1*11.45*18.46*0.95)/(1*250) = 441.76 lbs of N

C2. Pullets

assume 455 pullets under 3 months old per AU

and 250 pullets over 3 months old per AU

inventory, <3 mo K896 AU inventory K896/455

inventory >3 mo K894 AU inventory K894/250

sales K895 AU inventory K895/404

The Census has a single sales variable (K895) for pullets, regardless of age. Assume that sales of pullets are 'always' as pullets at four months; the corresponding AU is then the weighted average of 3 months at 455/AU and 1 month at 250/AU.

assume 120 days on feed, but only 2 cycles per year

If (K894>0 or K896>0) and K895=0 then pullinv=K894/250 + K896/455

If K894=0 and K896>0 and K895>0 then pullinv=(K896/455 + K895/(2*404))/2

If K894>0 and K896=0 and K895>0 then pullinv=(K894/250 + K895/(2*404))/2

If K894>0 and K896>0 and K895>0 then pullinv=(K894/250+K896/455 + K895/(2*404))/2

The manure values were defined per AU of pullets regardless of age, so the following computation holds:

manure nutrients (in lbs)

pull_n = pullinv*8.32*13.6

pull_p = pullinv*8.32*8.95

pull_k = pullinv*8.32*10.27

recoverable nutrients = pull_{N,P,K} * (state recovery factor for K896)

Shortcut for input number for ASM/HUMUS:

pullinv=(d_160016/250+d_160018/455+d_160033/(2*404))/2

then proceed as above.

D. Broiler Chickens

assume 455 broilers per AU

inventory, broilers K898 AU inventory K898/455

sales, broilers K899 AU sales K899/455

assume 60 days on feed (= 6 cycles per year)

If K898>0 and K899=0 then broilinv=K898/455

If K898=0 and K899>0 then broilinv=K899/(6*455)

If K898>0 and K899>0 then broilinv=(K898+K899/6)/(2*455)

manure nutrients (in lbs)

broil_n = broilinv*14.97*16.1

broil_p = broilinv*14.97*6.61

broil_k = broilinv*14.97*9.48

recoverable nutrients = broil_{N,P,K} * (state recovery factor for K898)

Shortcut for input number for ASM/HUMUS:

broilinv=(d_160020+d_160035/6)/(2*455)

then proceed as above.

Example:

25,000 broilers in inventory 75,000 broilers sold

continuous replacement

455 animals per AU 14.97 tons manure per AU

16.1 lbs N per ton manure

95 percent of manure recoverable (produced in confinement)

avg. inventory = (25000 +75000/6)/2 = 18750

layer_n=(18750*1*14.97*16.1*0.95)/(1*455) = 9435.42 lbs of N

E. Turkeys

E1. Turkeys for Breeding

assume 50 hens per AU:

inventory, hens K902 AU inventory K902/50

sales, hens K903 AU sales K903/50

assume continuous replacement (= 1 cycle per year)

If K902>0 and K903=0 then heninv=K902/50

If K902=0 and K903>0 then heninv=K903/50

If K902>0 and K903>0 then heninv=(K902+K903)/(2*50)

manure nutrients (in lbs)

hen_n = heninv*9.12*11.2

hen_p = heninv*9.12*11.23

hen_k = heninv*9.12*6.84

recoverable nutrients = hen_{N,P,K} * (state recovery factor for K902)

Shortcut for input number for ASM/HUMUS:

heninv=(d_160024+d_160043-d_160045)/(2*50)

with an adjustment in those counties where sales information was not disclosed

then proceed as above.

Example:

100 hens in inventory 10 hens sold

continuous replacement

50 animals per AU 9.12 tons manure per AU

11.2 lbs N per ton manure

95 percent of manure recoverable (produced in confinement)

avg. inventory = (100 +10)/2 = 55

layer_n=(55*1*9.12*11.2*0.95)/(1*50) = 106.74 lbs of N

E2. Turkeys on Feed

assume 67 turkeys per AU

inventory, turkeys K900 AU inventory K900/67

sales, turkeys K901 AU sales K901/67

assume 180 days on feed (= 2 cycles per year)

If K900>0 and K901=0 then turkinv=K900/67

If K900=0 and K901>0 then turkinv=K901/(2*67)

If K900>0 and K901>0 then turkinv=(K900+K901/2)/(2*67)

manure nutrients (in lbs)

turk_n = turkinv*8.18*16.18

turk_p = turkinv*8.18*10.06

turk_k = turkinv*8.18*10.44

recoverable nutrients = turk_{N,P,K} * (state recovery factor for K900)

Shortcut for input number for ASM/HUMUS:

turkinv=(d_160022-d_160024+d_160045/2)/(2*67)

with an adjustment in those counties where inventory information was not disclosed then proceed as above.

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