Abstract
Maximum manure N use efficiency by corn ( Zea mays L.) requires that N mineralization and subsequent plant availability coincide with N uptake demand. Information regarding the effects of time of manure application and use of a nitrification inhibitor on manure mineralization and corn yield is needed for producers to make sound manure management decisions. Studies were conducted at seven southern Minnesota sites over 3 yr to determine the effects of three manure application times (mid‐September, mid‐October, and late April), two manure rates, and a nitrification inhibitor, (nitrapyrin [NP] 1.0 lb a.i./acre), on corn yield and soil nitrate N concentration (0 to 12 in.) at the V4 growth stage. Application rates ranged from 3000 to 4000 gal/acre for the low rate and from 6000 to 8000 gal/acre for the high rate. For the four sites receiving liquid dairy ( Bostaurus ) manure, soil nitrate N was greatest when manure was applied in April and lowest when applied the previous September. The addition of NP increased soil nitrate N at three sites but affected grain yields at only one site when averaged across time and rate of manure application. Grain yields for the April, October, and September applications averaged 146, 142, and 139 bu/acre, respectively, across manure rates and NP treatments, with April exceeding the September application time (P < 0.10). When liquid swine ( Sus scrofa domesticus ) manure was used, the effects of application time and NP on soil nitrate N concentration and grain yield depended on climatic conditions. At one site where 8.5 in. of rain fell in a 5‐wk period in the spring, NP significantly increased both soil nitrate N concentration and grain yield for the October application but had no effect with the April application. Similar effects of NP on soil nitrate N were found at the other sites, but grain yields were not increased. Results from the seven site‐yr support about a 5% yield increase with April application compared with fall applications. However, it is unlikely that many farmers will consider this an economic advantage because of logistical challenges often faced with spring applications of manure in the Northern Corn Belt. Research Question Optimizing the use of N from manure requires that mineralization and subsequent plant availability of N from the manure coincides with plant uptake. Time of manure application (fall vs. spring) and use of a nitrification inhibitor are management decisions facing farmers that may greatly affect the agronomic value of manure and associated potential environmental risks. In this study, we determined the effect of three manure application times, two application rates, and the use of nitrapyrin (NP) on soil nitrate N concentrations at the V4 growth stage and corn grain yield. Using both dairy and swine manure, our hypothesis was that corn yields would probably be greatest with spring application of manure and with the addition of NP to fall‐applied manure. Literature Summary Research conducted in areas where soil temperatures generally remain above 32°F during the winter showed higher yields and uptake of N from spring‐applied manure than with fall applications. On the other hand, fall application of solid dairy manure in Wisconsin was superior to spring application when spring weather was wet and cool. Adding NP to manure has shown inconsistent results with positive responses when used with fall‐applied swine manure in Indiana and no response with spring‐applied liquid dairy manure in Wisconsin. Study Description Field studies were conducted at seven locations during a 3‐yr (1993–1995) period in south‐central Minnesota. Soil texture of the mollisols ranged from silt loam to silty clay loam. Oats, soybean, and millet were the previous crops, and irrigation was not used. Soil test P and K levels were high to very high and should have precluded any response to these nutrients. Liquid dairy manure was applied at four sites with three sites receiving liquid swine manure. Targeted times of application were mid‐September, mid‐October, and late April. Two application rates (low = 3000 or 4000 gal/acre and high = 6000 or 8000 gal/acre) were sweep‐injected about 4 to 5 in. deep. Nitrapyrin at a rate of 1 lb a.i./acre was added to one‐half of the manure treatments. Fertilizer N as urea was applied in the spring at rates of 0, 50, 100, and 150 lb N/acre. All treatments were replicated four times in a randomized, complete‐block design. Soil samples were taken from the 0 to 12‐in. depth at the V4 stage and analyzed for nitrate N. Com grain yields were determined by combine harvesting. Applied Questions Did time of manure application influence soil nitrate N concentration at the V4 stage and corn grain yield? Soil nitrate N concentration was generally greatest when dairy manure was applied in April and lowest for the September application. Grain yields were about 5% higher for April application than for fall applications. When swine manure was used, response to application time was highly dependent on spring and early summer weather. Under wet conditions, April application of manure gave substantially higher nitrate N concentration and grain yields compared with October application. When weather was more normal, soil nitrate N was greater for April application, but grain yields were unaffected by application time. Averaged across the 7 site‐yr, grain yield from fall manure application was about 7 bu/acre less than from spring application. However, because of logistical challenges, i.e., soil compaction, timeliness issues, inadequate manure storage capacity, etc., it is likely that many farmers in the Northern Corn Belt will not consider this an economic disadvantage. Was NP effective at increasing soil nitrate N concentration and grain yield? The addition of NP to manure increased soil nitrate N at five sites but only increased grain yield at two sites. At the site where 8.5 in. of rain fell in a 5‐wk period during May and June, grain yield was increased 16 bu/acre when manure plus NP was applied in October but was not affected by NP when applied in April. Did the in‐season soil nitrate test at the V4 stage serve as a good predictor of N availability from the manure? Based upon published current standard critical levels (above which no fertilizer is recommended), pre‐sidedress nitrate soil testing did not adequately predict N supply to corn from manure that had been applied within 8 to 9 mo prior to soil sampling. This was especially true for dairy manure. Recommendations Fall application of liquid dairy and swine manure, when soil temperatures have cooled to about 50°F or less, provides an agronomically acceptable alternative to spring application for the livestock producer. Although the addition of NP did not give conclusive results in our studies, soil nitrate N concentration was often increased by NP, and under wetter‐than‐normal spring conditions, yields were improved when NP was added to fall‐applied swine manure. These data suggest that NP should be considered when applying recommended rates of liquid swine manure before soils have cooled to remain below 50°F.
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Claims 16
Claim · model-written summary
Dairy manure applied in April produced greatest soil nitrate, with September lowest.
- Taxon
- Corn
Zea mays subsp. mayst0 - Treatment
- manure was applied in Aprile0
- Outcome
- soil nitrate Ne0
- Direction
- greateste0
- Comparator
- the previous Septembere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soil nitrate N was greatest when manure was applied in April and lowest when applied the previous September”
t0“Corn”
Claim · model-written summary
Nitrapyrin increased soil nitrate at three dairy manure sites.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe0
- Outcome
- soil nitrate Ne0
- Direction
- increasede0
- Qualifier
- at three sitese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The addition of NP increased soil nitrate N at three sites”
t0“Corn”
Claim · model-written summary
Nitrapyrin affected corn grain yield at only one dairy manure site.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe1
- Outcome
- grain yieldse0
- Qualifier
- only one sitee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but affected grain yields at only one site when averaged across time and rate of manure application”
t0“Corn”
e1“The addition of NP increased soil nitrate N at three sites”
Claim · model-written summary
April manure application yielded 146 bu/acre, exceeding September application at 139 bu/acre.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- Aprile0
- Outcome
- Grain yieldse0
- Direction
- exceedinge0
- Comparator
- Septembere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yields for the April, October, and September applications averaged 146, 142, and 139 bu/acre, respectively, across manure rates and NP treatments, with April exceeding the September application time (P < 0.10)”
t0“Corn”
Claim · model-written summary
October manure application averaged 142 bu/acre grain yield.
- Taxon
- CornZea mays subsp. mayst0
- Outcome
- Grain yieldse0
- Qualifier
- Octobere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yields for the April, October, and September applications averaged 146, 142, and 139 bu/acre, respectively”
t0“Corn”
Claim · model-written summary
With swine manure, application timing and nitrapyrin effects depended on climate.
- Taxon
- CornZea mays subsp. mayst0
- Outcome
- soil nitrate N concentration and grain yielde0
- Qualifier
- depended on climatic conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When liquid swine ( Sus scrofa domesticus ) manure was used, the effects of application time and NP on soil nitrate N concentration and grain yield depended on climatic conditions.”
t0“Corn”
Claim · model-written summary
At a wet site, nitrapyrin increased soil nitrate with October manure application.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe0
- Outcome
- soil nitrate N concentratione0
- Direction
- increasede0
- Qualifier
- October applicatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At one site where 8.5 in. of rain fell in a 5‐wk period in the spring, NP significantly increased both soil nitrate N concentration and grain yield for the October application but had no effect with the April application.”
t0“Corn”
Claim · model-written summary
At a wet site, nitrapyrin increased corn grain yield for October manure application.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe0
- Outcome
- grain yielde0
- Direction
- increasede0
- Qualifier
- October applicatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NP significantly increased both soil nitrate N concentration and grain yield for the October application”
t0“Corn”
Claim · model-written summary
At the wet site, nitrapyrin had no effect with April manure application.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe2
- Outcome
- soil nitrate N concentration and grain yielde1
- Direction
- no effecte0
- Qualifier
- April applicatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but had no effect with the April application”
e1“both soil nitrate N concentration and grain yield for the October application”
t0“Corn”
e2“NP significantly increased both soil nitrate N concentration”
Claim · model-written summary
Across seven site years, April manure application supported about 5% higher yield than fall application.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- April applicatione0
- Outcome
- yielde0
- Direction
- increasee0
- Value
- 5%e0
- Comparator
- fall applicationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Results from the seven site‐yr support about a 5% yield increase with April application compared with fall applications.”
t0“Corn”
Claim · model-written summary
Nitrapyrin increased soil nitrate at five sites.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe0
- Outcome
- soil nitrate Ne0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The addition of NP to manure increased soil nitrate N at five sites”
t0“Corn”
Claim · model-written summary
Nitrapyrin increased grain yield at two sites.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- NPe1
- Outcome
- grain yielde0
- Direction
- increasede0
- Qualifier
- two sitese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but only increased grain yield at two sites”
e1“The addition of NP to manure increased soil nitrate N at five sites”
t0“Corn”
Claim · model-written summary
At the wet site, October manure plus nitrapyrin increased grain yield by 16 bu/acre.
- Taxon
- CornZea mays subsp. mayst0
- Treatment
- manure plus NPe0
- Outcome
- grain yielde0
- Direction
- increasede0
- Value
- 16 bu/acree0
- Qualifier
- Octobere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grain yield was increased 16 bu/acre when manure plus NP was applied in October”
t0“Corn”
Claim · model-written summary
The soil nitrate test did not adequately predict nitrogen supply from recent manure.
- Taxon
- CornZea mays subsp. mayst0
- Outcome
- predict N supply to corne0
- Direction
- did not adequatelye0
- Comparator
- manure that had been applied within 8 to 9 moe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pre‐sidedress nitrate soil testing did not adequately predict N supply to corn from manure that had been applied within 8 to 9 mo prior to soil sampling.”
t0“Corn”
Claim · model-written summary
Fall application of liquid manure at cool soil temperatures is an agronomically acceptable alternative.
- Taxon
- CornZea mays subsp. mayst0
- Outcome
- Fall application of liquid dairy and swine manuree0
- Qualifier
- when soil temperatures have cooled to about 50°F or lesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fall application of liquid dairy and swine manure, when soil temperatures have cooled to about 50°F or less, provides an agronomically acceptable alternative to spring application”
t0“Corn”
Claim · model-written summary
The authors recommend considering nitrapyrin for liquid swine manure before soils cool below 50°F.
- Taxon
- CornZea mays subsp. mayst0
- Outcome
- NP should be considerede0
- Qualifier
- before soils have cooled to remain below 50°Fe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NP should be considered when applying recommended rates of liquid swine manure before soils have cooled to remain below 50°F.”
t0“Corn”
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