Crop residue and manure application

For most producers, it is important that every field operation leave the maximum amount of residue cover on the soil surface. However, for those producers who use manure as a nutrient, reducing odors from manure applications is equally important because neighbors often complain more often about odor from manure application than about odor from the facilities. Producers find themselves balancing good crop residue cover and the reduction of odor from manure applications.

Narrow nives on drag hose applicator

Above: Narrow knives on a drag hose applicator.

Several researchers recently presented their findings about the effects of manure application equipment on odor, residue cover, and crop yields. The experiments evaluated swine pit manure (liquid) application methods in no-till soybean and corn residue during three crop seasons (1996-1998). Crop yield levels were taken at harvest.

Sweep incorporation on a tank applicator

Above: Sweep incorporation on a tank applicator.

Below: Covering discs on a tank agitator.

Covering discs on a tank agitator.

Manure was applied by one of six different treatments (in the spring and fall of each of the three crop seasons). Residue was measured immediately before and after each treatment, and odor samples were taken from the surface within 5 minutes after the manure was applied, and 1 day after treatment (or later, depending on weather conditions).

For this study, the manure was applied to the field at a rate of 5,000 gallons per acre, at an applicator speed of 5 miles per hour. Researchers used a Better-Bilt vacuum tank, model 3400 (3,400-gallon capacity) manufactured by Top Air Manufacturing. The tank had an attached tool bar with four manure outlets set at a 30-inch spacing to apply manure between 30-inch rows. The liquid manure was applied by one of six methods: 1) injection with a conventional knife (2 inches in width); 2) injection with a conventional sweep (16 inches in width); 3) surface broadcast application followed by disk incorporation (manure outlets raised to 12 inches above the soil surface and diffusing the manure on a splash plate just below the outlet); 4) surface broadcast application only (manure outlets raised to 12 inches above soil surface and diffusing the manure on a splash plate just below the outlet); 5) injection with a narrow-profile knife (a 1-inch knife designed to minimize soil disturbance); or 6) surface application behind "row cleaners" (accomplished by moving residue from a narrow strip with a spoke wheel row cleaner, applying manure in a narrow surface band, then returning the residue over the band with spoke closing wheels).

In general, researchers found that incorporation methods resulted in higher corn yields (but not soybean yields) and lower odor. Choice of incorporation method to maintain residue cover was more important in soybean stubble with the narrow-row profile knife (5), row cleaner (6), and conventional knife methods (1), leaving more residue than injection with conventional sweeps (2) and broadcast application followed by disking (3). In corn residue, conventional knife incorporation (2) maintained residue cover as well as other incorporation methods. And surface applications resulted in higher odor levels but better preservation of crop residues.

If odor during application is a concern, avoid broadcast application methods--soil incorporation reduced odor levels by 20 to 90 percent compared with broadcast operations. (Refer to the tables for more information.)

For producers looking for answers, the best solution may lie in determining the ability of their equipment to reach an acceptable balance between reducing odor thresholds, maintaining residue cover, and affecting crop yields.

SOYBEAN After manure

application
After planting After manure

application
After planting After manure

application
After planting

Residue remaining

and residue

cover+
1995-96

residue

remaining*
1995-96

residue

cover+
1995-96

residue

remaining*
1995-96

residue

cover+
1996-97

residue

remaining*
1996-97

residue

cover+
1996-97

residue

remaining*
1996-97

residue

cover+
1997-98

residue

remaining*
1997-98

residue

cover+
1997-98

residue

remaining*
1997-98

residue

cover+

Fall 54 47 31 12 71 68 83 55 60 44 106 43
Spring 52 36 37 11 56 45 98 43 54 32 113 30

Application
Broadcast 92 72 18 13 93 82 89 72 103 68 70 47
Row cleaner 44 35 48 14 78 69 83 54 65 42 104 43
Narrow knife 67 47 23 12 71 63 87 54 49 33 114 37
Disk/incorporate 31 25 40 8 34 31 94 27 25 17 136 22
Sweep 34 26 45 12 45 40 86 34 42 28 131 33
Knife 55 43 26 11 59 52 105 53 57 38 104 38

*Residue remaining = (% residue cover after operation/%residue cover before operation) x 100%. For example if 80% residue cover exists before field operation and 60% cover exists after operation, residue remaining = 75% [(60%/80%) x 100%].

+Percentage residue cover after operation (= 60% in example from *).

CORN After manure

application
After planting After manure

application
After planting After manure

application
After planting

Residue remaining

and residue

cover+
1995-96

residue

remaining*
1995-96

residue

cover+
1995-96

residue

remaining*
1995-96

residue

cover+
1996-97

residue

remaining*
1996-97

residue

cover+
1996-97

residue

remaining*
1996-97

residue

cover+
1997-98

residue

remaining*
1997-98

residue

cover+
1997-98

residue

remaining*
1997-98

residue

cover+

Fall 85 80 48 41 82 77 78 60 65 60 77 43
Spring 81 76 53 38 71 62 95 57 76 62 75 39

Application
Broadcast 100 94 43 40 98 89 79 70 98 86 58 50
Row cleaner 86 81 50 40 78 71 87 60 81 70 50 34
Narrow knife 85 80 48 43 75 68 81 54 69 60 80 43
Disk/incorporate 81 76 50 37 71 65 79 50 34 30 106 30
Sweep 64 61 66 38 63 57 97 54 57 50 85 40
Knife 82 77 46 38 74 67 96 63 78 68 77 49

*Residue remaining = (% residue cover after operation/%residue cover before operation) x 100%. For example if 80% residue cover exists before field operation and 60% cover exists after operation, residue remaining = 75% [(60%/80%) x 100%].

+Percentage residue cover after operation (= 60% in example from *).

Odor from manure

application on soybean

residue
Fall 1996

At application
Fall 1996

1 day after

application
Fall 1996

5 days after

application
Spring 1997

At application
Spring 1997

1 day after

application
Fall 1997

At application
Fall 1997

1 day after

application
Spring 1998

At application
Spring 1998

1 day after

application

(odor units)
Broadcast 807 876 63 140 40 162 94 1451 211
Row cleaner 185 52 43 61 44 81 114 45 158
Narrow knife 173 64 60 12 36 85 97 181 87
Disk/incorporate 65 53 43 26 13 121 96 302 98
Sweep 94 60 43 35 16 102 109 181 64
Knife 256 113 43 33 43 128 98 257 72
Untreated soil -- -- -- -- 12 -- 94 241 84

Odor units are the number of clean-air dilutions required to reach a threshold odor level for a panel of four observers.

Odor from manure

application on corn

residue
Fall 1996

At application
Fall 1996

5 days after

application
Spring 1997

At application
Spring 1997

1 day after

application
Fall 1997

At application
Fall 1997

1 day after

application
Spring 1998

At application
Spring 1998

1 day after

application

(odor units)
Broadcast 389 43 216 30 183 115 1604 196
Row cleaner 67 43 188 30 100 86 385 82
Narrow knife 247 70 106 38 82 109 181 85
Disk/incorporate 75 43 56 25 157 91 273 60
Sweep 57 43 25 26 122 76 136 38
Knife 502 53 16 18 116 105 121 73
Untreated soil -- -- -- 12 -- 118 241 94

Odor units are the number of clean-air dilutions required to reach a threshold odor level for a panel of four observers.

This article originally appeared on pages 175-177 of the IC-482(23) -- October 11, 1999 issue.

Updated 10/10/1999 - 1:00pm