Corn Response to Composting and Time of Application of Solid Swine Manure
Terrance D. Loecke, Matt Liebman,* Cynthia A. Cambardella, and Tom L. Richard
ABSTRACT social impacts of doing so have some producers and
scientists searching for alternative forms of management Swine production in hoop structures is a relatively new husbandry
in which manure is handled as a solid (Honeyman, 1996). system in which a mixture of manure and bedding accumulates. This
manure/bedding pack can be applied to crop fields directly from a hoop One option involves swine production in deep-bedded structure or piled for composting. During 2000 and 2001, field experi- hoop structures. In Iowa, nearly one million head of swine ments were conducted near Boone, IA, to determine the effects of are finished per year in these hoop structures (Leopold form of solid swine manure (fresh or composted) and time of manure Cent. for Sustainable Agric., 2001). Swine hoop struc-application (fall or spring) on corn (Zea maysL.) nutrient status and tures are typically bedded with corn stalks or cereal yield. Fresh and composted manure were applied at 340 kg total N
straw, which absorb urine and feces throughout the four-ha⫺1. Urea N fertilizer treatments of 0, 60, 120, and 180 kg N ha⫺1
to six-month production cycle. During this time, some were used to determine N fertilizer equivalency values for the manure.
in situ composting occurs although the extent of this In 2000, but not in 2001, fresh manure decreased corn emergence by
unmanaged decomposition varies widely. Swine manure 9.5% compared with the unamended, nonfertilized control treatment.
from hoop structures can be spread on fields immedi-No corn yield differences due to the form or the time of manure
ap-plication were detected in 2000, but all treatments receiving manure ately after animals are removed from the buildings, or it produced more corn grain than the unamended control. In 2001, fall can be piled for additional composting (Tiquia et al., application of manure increased corn grain yield more than spring 2000).
application, and composted manure increased yield more than fresh Composted manure has a number of potential advan-manure, with spring-applied fresh manure providing no yield response
tages over fresh manure, including reductions in viable beyond the unamended control. Mean N supply efficiency, defined
weed seed content (Wiese et al., 1998; Eghball and Le-as the N fertilizer equivalency value Le-as a percentage of the total N
soing, 2000), improvements in handling characteristics applied, was greatest for fall-applied composted manure (34.7%),
(by reducing manure volume and associated transporta-intermediate for fall-applied fresh manure (24.3%) and spring-applied
tion costs), and a reduction in particle size leading to composted manure (25.0%), and least for spring-applied fresh
ma-nure (10.9%). increased uniformity of field application (Rynk, 1992).
Compost-amended soils can increase crop growth be-yond levels explainable by nutrient effects (Valdrighi et al., 1996), provide protection from plant pathogens
O
ver one billion metric tonsof N are excreted in(Hoitink and Kuter, 1986), and suppress weed seedling swine (Sus scrofaL.) manure in the United States
emergence (Menalled et al., 2002). Phytotoxic substances annually (NRCS, 2000). Swine manure applied to crop
contained in fresh solid swine manure, such as high fields can be an important source of plant nutrients and
concentrations of NH⫹
4–N, decrease with time of
com-organic matter, which can improve soil quality (Khaleel
posting (Tiquia and Tam, 1998) and time following soil et al., 1981). Nevertheless, current practices for
man-application. Disadvantages of composting are poten-agement and utilization of swine manure can potentially
tially large losses of C and N and labor and capital contribute to degradation of water and air quality
costs associated with extra manure handling and space (Sharpley et al., 1998; Zebarth et al., 1999). Better
man-requirements for the compost piles. Losses of N mea-agement options are needed.
sured during composting of animal manure have ranged Most swine manure in the USA is handled and stored
as a liquid (NRCS, 2000), but the environmental and from 20 to 70% (Martins and Dewes, 1992; Rao Bhami-dimarri and Pandey, 1996; Eghball et al., 1997; Tiquia et al., 2002). Garrison et al. (2001) estimated that 41% T.D. Loecke, Dep. of Crop and Soil Sci., Michigan State Univ., 539
Plant and Soil Sciences Bldg., East Lansing, MI 48824-1325; M. Lieb- of total N contained in fresh swine hoop manure was lost man, Dep. of Agron., 3405 Agronomy Hall, Iowa State Univ., Ames, during two months of intensively managed composting. IA 50011-1010; C.A. Cambardella, USDA-ARS, 310 Natl. Soil Tilth Synchrony of plant-available soil nutrients and crop Lab., Ames, IA 50011-3120; and T.L. Richard, Dep. of Agric. and
nutrient demand is essential for optimum crop perfor-Biosyst. Eng., 3222 Natl. Swine Res. and Inf. Cent., Iowa State Univ.,
Ames, IA 50011-3080. Partial funding for this work was provided by mance and environmental protection (Magdoff, 1995). the Leopold Center for Sustainable Agriculture (Project 2000-42), If plant-available N (NO⫺
3 and NH⫹4) is not supplied in
the Iowa Department of Natural Resources (Project 00-G550-01CG), synchrony with crop demand, then substantial N losses and Chamness Technology (Project 1221). We thank J. Ohmacht, D.
can occur before or after periods of crop demand. The Sundberg, and R. Vandepol for technical assistance in the field and
quantity of plant-available N is dynamic and reflects the laboratory. Received 5 Dec. 2002. *Corresponding author (mliebman@
iastate.edu). balance between N mineralization, N immobilization, and removal of inorganic or organic N from the soil rooting Published in Agron. J. 96:214–223 (2004).
zone (e.g., via leaching, volatilization, denitrification,
American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA soil erosion, and plant uptake). Soil physical conditions,
Table 1. Characteristics of the surface 20 cm of soil in experiment
including temperature, water status, and aeration, and
fields before treatment applications.
the C/N ratio and C constituents (especially lignin
quan-Soil parameter 14 Oct. 1999 28 Sept. 2000
tities) of organic materials are the primary factors
affect-ing mineralization rates (Jenny, 1980; Swift et al., 1979). Bulk density, g cm⫺3 1.3 1.2
Total organic C, Mg ha⫺1 43.5 46.7
In previous investigations, corn yield responses to
Total organic N, Mg ha⫺1 3.8 4.1
composted and fresh manure have been similar when Nitrate N, kg ha⫺1 13.0 19.3
these amendments were applied at the same time (Reider Ammonium N, kg ha⫺1 4.0 1.8
Mehlich-1 P, kg ha⫺1 115 113
et al., 2000; Eghball and Power, 1999; Brinton, 1985;
Mehlich-1 K, kg ha⫺1 381 270
Ma et al., 1999; Xie and MacKenzie, 1986). However, pH 6.6 6.4
Electrical conductivity, S m⫺1 0.0155 0.0178
N use efficiencies observed in these studies indicate that plant-available N from manure-derived compost is
typically equal to or less than that from fresh manure. All of the fresh and composted hoop manure was produced Timing of amendment application can influence crop on the Iowa State University Rhodes Research Farm in
Mar-responses but often interacts with weather conditions shall County, IA, except for the fresh manure applied in the spring of 2001, which came from a commercial farm in Story
(Warman, 1995; Talarczyk et al., 1996; Sanchez et al.,
County, IA. Urea N was side-dressed in plots that did not
re-1997).
ceive manure at corn growth stage V6 (Hanway, 1963) (9 June
Currently, no guidelines are available for when and
2000 and 18 June 2001) and was incorporated within 24 h of
in what form (composted or fresh) swine hoop manure
application using an interrow cultivator. Corn (‘Pioneer 35P12’)
should be field-applied to best utilize it as a nutrient
was planted at 68 000 seeds ha⫺1on 4 May 2000 and 74 000 seeds
resource and to minimize potential negative environ- ha⫺1on 9 May 2001. Weed control was achieved with a
preplant-mental impacts. The objective of this study was to deter- incorporated application of metolachlor [2-chloro-N -(2-ethyl-6-mine first-year corn response to season of application methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] at 1.5 (fall vs. spring) and form of swine hoop manure (com- kg a.i. ha⫺1, interrow cultivation at plant growth stage V6, and
posted or fresh). hand weeding.
Plant, Soil, and Amendment Sampling and Analysis MATERIALS AND METHODS
A 4-L composite sample of each amendment (fresh or
com-Field Site and Experimental Design posted manure) was collected immediately before materials
were applied to plots, generating one sample per plot and Field plot research was conducted at the Iowa State
Univer-sity Agronomy and Agricultural Engineering Research Farm four replicates per treatment. Samples were stored at⫺20⬚C in plastic freezer bags, then thawed, homogenized, separated near Boone, IA (42⬚1⬘N, 93⬚45⬘W), during 2000 and 2001 on
Clarion loam (fine-loamy, mixed, superactive, mesic Typic Hap- for various analyses (total P, K, NH⫹
4–N, NO⫺3–N, moisture,
ash content, pH, and electrical conductivity), and then refro-ludolls) and Nicollet loam (fine-loamy, mixed, superactive,
mesic Aquic Hapludolls) soils. Soil samples taken from the zen until individual parameters were analyzed. Amendment total C and N were determined after acidification with 0.5M
surface 20 cm before fall application of amendments indicated
adequate P and K fertility levels in both years (Table 1). HCl (1:2 sample/solution ratio), air drying, grinding, and dry combustion in a Carlo-Erba NA1500 NCS elemental analyzer The field used for the 2000 experiment was cropped with oat
(Avena sativaL.) in 1999; the field used for the 2001 experi- (Haake Buchler Instruments, Paterson, NJ) as described by Cambardella et al. (2003). Total P and K were determined on ment was cropped with soybean [Glycine max(L.) Merr.] in
2000. Neither field had received animal manure for at least dried ground samples by USEPA method 3051 at a commercial laboratory (Midwest Laboratory, Omaha, NE) following a pro-the previous 8 yr. Annual and long-term weapro-ther data were
collected from an automated weather station located⬍1 km tocol given by Dancer et al. (1998). Ammonium N and nitrate N were determined using 2MKCl extracts (1:80 amendment/ from the field sites (Fig. 1).
The core of the experiment consisted of a factorial treat- solution ratio) and Lachat flow analysis (Lachat Instruments, Milwaukee, WI) (Keeney and Nelson, 1982). Amendment ment design that crossed season of application (fall or spring)
with form of manure (fresh or composted hoop manure). An moisture content was determined by drying at 70⬚C for 48 h, ash content was determined by ignition at 550⬚C, and pH and additional set of treatments (0, 60, 120, and 180 kg N ha⫺1urea)
was applied to plots not receiving manure and was used to electrical conductivity were determined using a 1:5 amend-ment/water slurry.
estimate N fertilizer equivalency of the manure. Treatments
were arranged in a randomized complete block design with To monitor plant and soil N status throughout the growing season, late-spring soil NO⫺
3–N concentration, ear leaf N and
four replications. Plot size was 3.8 m (five rows with a 0.76-m
row spacing) by 10.7 m in 2000 and 12.2 m in 2001. Manure chlorophyll contents, and fall stalk NO⫺
3–N concentration were
measured. All plant and soil parameters were measured from treatments were applied by hand in the fall (22 Oct. 1999 and
24 Oct. 2000) and spring (25 Apr. 2000 and 25 Apr. 2001) at the center three rows of each plot. Soil NO⫺
3–N samples,
con-sisting of a composite of ten 2-cm-diam. soil cores from the a rate of 340 kg N ha⫺1based on moisture and total N content
of samples taken 2 wk before application (Table 2). Amend- surface 30 cm, were collected from each plot on 3 June 2000 and 4 June 2001 and were processed according to procedures ments were incorporated with a disk into the surface 15 cm
within 6 h of application. Application rates were chosen based described by Blackmer et al. (1989).
Thirty leaf chlorophyll meter readings were taken in each on the assumption that one-third of the total applied N (i.e.,
110 kg N ha⫺1) would be available during the first year after plot using a Minolta SPAD-502 chlorophyll meter (Minolta,
Ramsey, NJ) as others have done (Piekielek and Fox, 1992). application, as was observed by Eghball and Power (1999).
This expected quantity of available N is approximately equal Readings were taken 1.5 cm from the leaf edge of the center (lengthwise) of the topmost fully expanded leaf or the same to the N harvested in 9.0 Mg of corn grain, the long-term
Fig. 1. (a) Monthly average daily temperature and (b) total precipitation for 2000, 2001, and the 50-yr average at a weather station located ⬍1 km from the field sites.
Ten ear leaves were collected in each plot at growth stage surface from each plot at grain harvest, dried at 60⬚C for 4 d, ground to pass a 0.85 mm screen, and analyzed for NO⫺
3–N
R1 (Hanway, 1963) for nutrient analysis. Ear leaf samples
were dried at 60⬚C for 4 d, ground to pass a 0.85-mm screen, (Binford et al., 1992). and analyzed for total Kjeldahl N. Ear leaf P concentrations
were determined by nitric acid plus peroxide digestion
fol-Statistical Analysis
lowed by inductively coupled plasma mass spectrometry
(Har-ris Laboratory, Lincoln, NE). Grain was harvested with a Analysis of variance (ANOVA) was conducted using the PROC GLM routine of SAS (SAS Inst., 1999) to test for main combine from 9.8 and 10.7 m of the center three rows of each
plot in 2000 and 2001, respectively. Reported grain yields are and interaction effects, with blocks, years, and treatments in the model. Single degree-of-freedom contrasts were used to adjusted to a moisture content of 155 g kg⫺1. Fifteen stalk
Table 2. Composition of organic amendments.
Total
Time of application Form H2O Ash P K C N C/N NHⴙ4–N NO⫺3–N pH† EC†
g kg⫺1‡ g g⫺1 S m⫺1
1999 Fall Fresh manure 624 406 11.5 21.7 323 28.6 11.3 3500 15 8.8 0.46
Composted manure 340 624 11.7 20.6 181 16.9 10.7 500 820 8.0 0.59
2000 Spring Fresh manure 631 302 11.0 24.7 343 30.0 11.5 2770 78 8.2 0.57
Composted manure 313 726 8.8 15.4 144 12.8 11.2 730 750 8.1 0.55
2000 Fall Fresh manure 389 284 11.3 20.5 323 24.8 13.0 910 18 8.5 0.70
Composted manure 317 608 7.4 12.9 199 17.2 11.6 360 750 7.4 0.50
2001 Spring Fresh manure 613 418 5.2 13.0 316 22.3 14.2 1560 96 8.3 0.23
Composted manure 534 595 6.7 16.6 206 16.3 12.7 940 140 8.3 0.51
† Electrical conductivity (EC) and pH were determined using a 5:1 water/amendment slurry.
‡ Moisture content is expressed on a wet weight basis, and all other concentration parameters are expressed on a dry matter basis.
nitrate concentrations were square-root–transformed before NH⫹
4–N to NO⫺3–N ratios observed here suggest that the
statistical analysis to meet the ANOVA assumption of homog- composted manure generally was more decomposed than eneity of variances. Correlations between soil and plant parame- the fresh manure; the exception being the manure ters were made on an experimental unit basis using PROC applied in the spring of 2001, which had a more simi-CORR in SAS. PROC REG of SAS was used to fit quadratic lar NH⫹
4–N/NO⫺3–N ratio than at all other application
equations to the relationship between grain yields and urea
times (Table 2).
N fertilizer rates.
Each of the applied amendments contained a substan-tial quantity of total P (Table 2). Annual applications
RESULTS AND DISCUSSION
of livestock manure to fields in corn–soybean rotationsat rates sufficient to meet corn N requirements have
Weather Conditions
the potential to accumulate soil P (Jackson et al., 2000) The period from amendment application in October
due to higher P application rates than grain P removal 1999 until corn planting in May 2000 was warmer and rates. In our study, the P application rate ranged from drier than the 50-yr average (Fig. 1a and 1b) whereas
79 to 242 kg P ha⫺1(Table 3), with mean P application
the 2000–2001 winter was colder and wetter than the rates of 121 and 188 kg P ha⫺1for fresh and composted
50-yr average (Fig. 1a and 1b). Mean monthly
tempera-hoop manure, respectively, and 167 and 142 kg P ha⫺1
tures during the 2000 and 2001 growing seasons were
for fall- and spring-applied amendments, respectively typical compared with the 50-yr average (Fig. 1a). Both
(Table 3). During 2000–2001, corn and soybean yields growing seasons had lower-than-normal total
precipita-in Boone County, IA, averaged 9.7 and 2.7 Mg ha⫺1
tion (Fig. 1b), but the precipitation patterns differed
(NASS, 2002), respectively, which would have removed between years. The 2000 growing season began with dry
an estimated 28 kg P ha⫺1 yr⫺1 for corn and 16 kg P
soil conditions followed by timely but limited
precipita-ha⫺1yr⫺1for soybean (Voss et al., 1999). The combined
tion. In contrast, the 2001 growing season was drier than
P removal rate from one cycle of a corn–soybean rota-normal from mid-June until September but began with
tion therefore would have been 44 kg P ha⫺1. A
compari-moist soil conditions in May following the wet winter
son of the P applied in this study with the estimated P season (Fig. 1b).
grain removal indicates that one application of either fresh or composted hoop manure per rotation cycle
Amendment Composition and Application
would lead to soil P accumulation. It should be noted, Carbon/N ratios of the applied amendments ranged however, that fresh hoop manure had a higher N/P ratio from 10.7:1 to 14.2:1 with means of 12.5:1 and 11.6:1 for (Table 3), which would slow soil P accumulation com-fresh and composted manures, respectively (Table 2). pared with composted hoop manure if P removal rates Materials with C/N ratios of less than 20:1 are generally for grain were equal in the two management systems. thought not to immobilize soil N (Mathur et al., 1993)
although short-term immobilization with partially com- Table 3. Loading rates of organic amendments. posted hoop manure (C/N ratios of 12:1 to 15:1) has been
Application rate† observed (Cambardella et al., 2003). The amendments
Time of application Form N P C DM‡
applied in the spring of 2001 had the highest C/N ratios,
perhaps due to the cool and wet conditions of the fall– kg ha⫺1 Mg ha⫺1
winter–spring period of 2000–2001, which may have Fall 1999 Fresh manure 340 130 3.66 11.3
Composted manure 340 240 3.74 20.7 slowed decomposition in the compost windrows. These
Spring 2000 Fresh manure 340 120 3.85 11.2 weather conditions also likely increased the bedding
Composted manure 340 230 3.76 26.1 requirement and/or altered the bedding management
Fall 2000 Fresh manure 340 150 4.38 13.6
on the commercial farm from which the fresh manure Composted manure 340 140 3.89 19.5
applied in the spring of 2001 was obtained. Spring 2001 Fresh manure 340 80 4.77 15.1
Composted manure 340 140 4.24 20.6 The ratio of NH⫹
4–N to NO⫺3–N has been used as an
indicator of compost maturity (Mathur et al., 1993), with † Application rates of total N, P, and C contained within each manure. ‡ DM, dry matter.
Table 4. Treatment means, analysis of variance, and correlation to yield for plant population and late-spring soil nitrate concentration during 2000 and 2001.
Plant population Soil nitrate
Time of application Form Total rate 2000 2001 2000 2001
kg N ha⫺1 Plants ha⫺1 NO
3
⫺–N,g g⫺1
None None (control) 0 65 900 72 800 8.3 3.3
Side-dressed (at V6) Urea 60 63 300 72 700 7.8 3.2
Side-dressed (at V6) Urea 120 67 400 73 300 8.5 4.6
Side-dressed (at V6) Urea 180 65 200 72 900 8.9 3.5
Fall Fresh manure 340 61 000 72 800 10.7 5.8
Fall Composted manure 340 63 500 72 700 15.8 5.3
Spring Fresh manure 340 58 300 72 500 9.1 5.2
Spring Composted manure 340 64 000 73 800 19.6 5.8
Standard error (SE) 1 050 910 1.1 0.5
Source of variation
Treatment contrasts P⬎F
Forms (F)
Urea fertilizer linear response ns ns ns ns
Urea fertilizer quadratic response ns ns ns ns
Urea fertilizer cubic response * ns ns ns
Control vs. all organic amendments ** ns *** ***
Among amendments (fresh vs. composted) *** ns *** ns
Time of application (A)
Amendments (fall vs. spring) ns ns ns ns
F⫻A
Amendments (fresh vs. composted)⫻(fall vs. spring) ns ns * ns
Correlation to yield (r) ⫺0.20ns ⫺0.11ns 0.47* 0.18ns
* Significant at theP⬍0.05 probability level. ** Significant at theP⬍0.01 probability level. *** Significant at theP⬍0.001 probability level.
Corn Emergence
midwest and northeast USA to predict corn yield re-sponse to N fertilizer (Blackmer et al., 1989; Magdoff, In 2000, corn emergence was negatively affected by1991). Although this method has been calibrated for fresh manure applied in both fall and spring (Table 4).
synthetic N fertilizer sources and to a limited extent for We believe these plant emergence effects were likely
soils amended with liquid swine manure (Hansen, 1999), caused by a combination of physical and chemical
influ-it has not been calibrated for soils receiving solid live-ences of the fresh manure. In the spring of 2000,
fresh-stock manure. In an evaluation of corn yield responses manure clods were visible on the soil surface despite
to variations in soil NO⫺
3–N concentration, Blackmer et
tillage. Combined with dry soil surface conditions, which
al. (1989) set the maximum soil NO⫺
3–N concentration
required a deeper-(8–10 cm)-than-normal (4–6 cm)
plant-in the surface 30 cm at which to expect a yield response ing depth for seed to soil moisture contact, the physical
from applications of synthetic N fertilizer at 25 g g⫺1
and/or chemical effects of the fresh-manure clods on
for unmanured soils in years with normal or below-the soil surface over below-the plant row prevented consistent
normal spring precipitation, at 20 to 22 g g⫺1for
un-emergence. Fall-applied fresh manure tended to reduce
manured soils in years with wet springs, and at 11 to plant emergence less than spring-applied fresh manure
15g g⫺1for manured soils.
in 2000 (Table 4). This was probably due to degradation
In both years of our study, soil NO⫺
3–N concentrations
and/or dispersion of any potential phytotoxic substances
were higher in plots receiving manure than in the un-and physical degradation of the fresh manure clods that
amended fertilizer-free control (Table 4). A significant occurred during the winter following fall application of
manure form ⫻ application time interaction was de-manure. Tiquia et al. (1996) found NH⫹
4–N concentra- tected for soil NO⫺
3–N concentrations in 2000 (Table 4),
tion (ranging from⬍500 to 4200g g⫺1) to be the most
with the highest soil NO⫺
3–N concentrations found in
important chemical component of solid swine manure
plots treated with spring-applied composted manure in predicting phytotoxic effects on vegetable seedlings.
and the lowest found in plots amended with spring-Despite the stand reductions observed in the present
applied fresh manure. The lower soil NO⫺
3–N
concentra-study, plant population densities were not correlated
tions observed in 2001 compared with 2000 (Table 4) with grain yields (Table 4).
may have reflected the high soil moisture conditions In 2001, plant emergence was not affected by manure
before sampling (Fig. 1b), which could have caused ni-treatments (Table 4). Moist soil conditions throughout
trate leaching or denitrification losses. the spring of 2001 allowed for adequate reductions of
fresh-manure clod size during tillage and thus
elimi-Ear Leaf Nitrogen and Phosphorus
nated the plant emergence problems observed in 2000.
Concentrations and Chlorophyll Meter Readings
Late-Spring Soil Nitrate Concentration
Chlorophyll meter readings of corn ear leaves at growthstage R1 responded positively to urea application in both The NO⫺
3–N concentration in the surface 30 cm of soil
in-Table 5. Treatment means, analysis of variance, and correlation to grain yield for SPAD chlorophyll meter readings and corn ear leaf N and P concentrations at growth stage R1, and fall stalk nitrate concentrations in 2000 and 2001.
SPAD Ear leaf N Ear leaf P Fall stalk nitrate
Time of application Form Rate 2000 2001 2000 2001 2000 2001 2000 2001
kg N ha⫺1 g kg⫺1 NO
3
⫺–N,g g⫺1†
None None (control) 0 55.7 52.6 20.5 25.2 2.5 2.0 4.5 (20) 4.9 (38)
Side-dressed (at V6) Urea 60 60.4 54.6 24.5 25.1 2.9 2.2 4.5 (20) 4.3 (25)
Side-dressed (at V6) Urea 120 61.2 56.2 26.5 26.7 3.1 2.1 26.0 (815) 23.3 (566)
Side-dressed (at V6) Urea 180 61.8 58.0 27.0 27.9 3.3 2.2 77.7 (6123) 37.9 (1491)
Fall Fresh manure 340 58.0 57.5 24.1 26.2 3.5 2.2 10.1 (135) 18.3 (402)
Fall Composted manure 340 60.1 58.3 24.6 26.3 3.0 2.2 9.6 (119) 6.5 (52)
Spring Fresh manure 340 57.2 50.7 23.1 23.2 3.4 2.1 5.3 (31) 8.0 (66)
Spring Composted manure 340 60.0 55.1 25.5 25.5 3.4 2.2 7.1 (58) 5.0 (36)
Standard error (SE) 0.53 0.81 0.9 0.7 0.1 0.1 3.2 2.4
Source of variation
Treatment contrasts P⬎F
Forms (F)
Urea fertilizer linear response *** *** *** ** *** ‡ *** ***
Urea fertilizer quadratic response *** ns ‡ ns ns ns *** **
Urea fertilizer cubic response ns ns ns ns ns ns ns ns
Control vs. all organic amendments *** ** *** ns *** * ns ns
Among amendments (fresh vs. composted) *** ** ns ‡ ns ns ns **
Time of application (A)
Amendments (fall vs. spring) ns *** ns ** ns ns ns *
F⫻A
Amendments (fresh vs. composted)⫻(fall vs. spring) ns * ns ‡ ‡ ns ns ‡
Correlation to yield (r) 0.70*** 0.51* 0.44* 0.55** 0.25ns 0.35* 0.54** 0.37*
* Significant at theP⬍0.05 probability level. ** Significant at theP⬍0.01 probability level. *** Significant at theP⬍0.001 probability level.
† Analysis of variance conducted on square-root–transformed data. Data in parentheses are means of raw data. ‡ Significant at theP⬍0.1 probability level.
creasing rates of urea fertilizers (p⬍0.001) was found phyll meter readings at growth stage R1 correlated well with final corn grain yield (Table 5). Eghball and Power in 2000, suggesting that N was not limiting in the higher
urea application rates (120 and 180 kg N ha⫺1) at this (1999) also found a strong correlation (r ⬎ 0.71)
be-tween chlorophyll meter readings and grain yield, except point in the season (Table 5). However, because
chloro-phyll meters are useful for indicating N deficiencies, but in a season of low precipitation. In our study, ear leaf not for determining excessive soil N availability (Schep- N concentration and chlorophyll readings at R1 were ers et al., 1992), this issue remains unresolved. also well correlated with each other (2000: r ⫽ 0.54,
Eghball and Power (1999) found similar chlorophyll P⬍0.01; 2001: r⫽ 0.64,P⬍ 0.0001).
meter reading results when comparing composted and Corn ear leaf P concentrations increased linearly with noncomposted beef feedlot manure to unamended con- increasing rates of urea application in both years (Ta-trols throughout the growing season. In 2000 of our study, ble 5). This may indicate that plants in the higher urea composted manure treatments (fall- and spring-applied) treatments foraged for soil P more efficiently and/or had higher chlorophyll readings than fresh manure (fall- that the hydrolysis of urea lowered soil pH, thus making and spring-applied), and the mean of all manure treat- more soil P available to plants (Miller and Ohlrogge, ments was greater than the no-amendment control (Ta- 1958; Olson and Dreier, 1956). Differences in ear leaf ble 5). A significant interaction was detected in 2001 P between years may have been due to differences in between form of manure and timing of application (Ta- early-season soil moisture although many fertility and ble 5). Spring-applied fresh-manure plots in 2001 had environmental factors can interact to influence ear leaf the lowest chlorophyll readings among the manure treat- P concentrations (Voss et al., 1970). In 2001, there were ments whereas fall-applied fresh and composted manure minimal differences between treatments with regard to had the highest readings and the spring-applied com- ear leaf P concentration (Table 5).
posted manure gave an intermediate value (Table 5).
Corn ear leaf N concentration at growth stage R1 re-
Corn Grain Yield
sponded positively to urea application in both years
(Ta-Corn grain yields increased in both years in response ble 5) although the intensity of the response was greater
to increasing rates of urea application (Fig. 2; Table 6). in 2000 than in 2001. The mean ear leaf N concentration
The highest yields in response to urea application were of all manure treatments was higher than that of the
similar in both years, but the yield of the control control in 2000, but no difference between manure
treat-ment was lower in 2000 than in 2001. This pattern was ments and the control was detected in 2001 (Table 5).
similar to that observed for the ear leaf N concentration The season of manure application was important for the
at plant growth stage R1 and may reflect the influence 2001 corn crop; fall-applied manure generated higher
of the previous year’s crop on the quantity and quality ear leaf N concentrations than did spring-applied
ma-of organic matter added to the soil and its N mineraliza-nure (Table 5).
Fig. 2. Grain yield from urea N rates side-dressed at plant growth stage V6 and fresh manure and compost treatments from 2000 and 2001. Error bars represent plus/minus one standard error. Grain yields were adjusted to a moisture content of 155 g kg⫺1. Treatment contrasts are presented in Table 6.
the 2000 corn crop, which followed oat, had a lower greater than those from fresh-manure treatments (10.3 yield than the 2001 corn crop, which followed soybean vs. 8.8 Mg ha⫺1). Additionally, fall-applied manure
pro-(6.7 vs. 8.1 Mg ha⫺1). duced higher yields than did spring-applied manure
The mean grain yield from manure treatments was (10.1 vs. 8.9 Mg ha⫺1) (Table 6).
greater than the control in both years (Table 6; Fig. 2). The poor yield response to spring-applied fresh ma-In 2000, no grain yield differences were detected due nure was more pronounced in 2001 when early-season to the time of application or the form of manure (com- soil conditions were moist and cool relative to 2000. In posted or fresh manure) (Table 6). In contrast, in 2001, Wisconsin, similar results were found in wet-cool springs grain yields from composted manure treatments were if fresh solid dairy manure was applied immediately be-fore corn planting (Talarczyk et al., 1996). Talarczyk et al.
Table 6. Analysis of variance of corn grain yields in 2000 and 2001. (1996) attributed this result to a pattern of manure N
mineralization that was slower than normal. Fall appli-P⬎F
Source of variation cation of solid manure in their study and in our study
Treatment contrasts 2000 2001
resulted in more consistent yield benefits than did spring
Forms (F) applications. This may be due to more timely net N
Urea fertilizer linear response *** ***
mineralization relative to plant N demand with fall ap-Urea fertilizer quadratic response ns ns
Urea fertilizer cubic response ns ns plication vs. spring application. Control vs. all organic amendments *** **
Among amendments (fresh vs. composted) ns ***
Time of Application (A)
Nitrogen Fertilizer Equivalency and
Amendments (fall vs. spring) ns **
F⫻A
Nitrogen Supply Efficiency
Amendments (fresh vs. composted)⫻(fall vs. spring) ns nsA quadratic equation was fit to the yield data of urea ** Significant at theP⬍0.01 probability level.
Table 7. Calculated N fertilizer equivalency values and N supply (Table 5). In 2001, fresh-manure applications resulted efficiencies of amendments, based on corn yield response to urea in higher stalk NO⫺
3–N concentrations than composted-fertilizer side-dressed at corn growth stage V6, in 2000 and 2001.
manure applications, and fall applications gave higher
N fertilizer N supply stalk NO⫺
3–N concentrations than did spring-applied
equivalency value efficiency†
Time of manure. The relationship of stalk NO⫺3–N concentration
application Form 2000 2001 Mean 2000 2001 Mean to grain yield in 2000 followed closely the relationship kg N ha⫺1 % described by Binford et al. (1992), but this pattern was Fall Fresh manure 103 60 82 30.7 17.9 24.3 not as distinct in 2001 (figure not shown). It is unclear Fall Composted manure 96 137 117 28.6 40.8 34.7 if this was due to limited available soil N or increased Spring Fresh manure 79 ⫺6 37 23.5 ⫺1.8 10.9
NO⫺
3 assimilation efficiencies. For example, in 2001,
de-Spring Composted manure 97 71 84 28.9 21.1 25.0
spite having similar yields, the fall-applied composted-† N supply efficiency defined as the N fertilizer equivalency value expressed
manure treatment resulted in lower stalk NO⫺
3–N
con-as a percentage of the total N applied (340 kg N ha⫺1).
centrations than did the 120 and 180 kg N ha⫺1urea N
treatments. This suggests that factors other than N ef-linear trend was statistically significant (Table 6), the
fects may have contributed to the grain yield response quadratic function produced a better fit to the data and
to manure. thus allowed for a more realistic extrapolation between
the yield data of urea N fertilizer and manure treatments
(see Blevins et al., 1990). Based on each quadratic urea
SUMMARY
response curve, N fertilizer equivalency values were
cal-At the rates used in this study, spring application of culated for each manure treatment mean (Table 7).
Ni-fresh hoop manure resulted in problems with corn emer-trogen supply efficiencies for the different manure
treat-gence, lower N use efficiencies, and inconsistent yields. ments were calculated by dividing N fertilizer equivalency
Although treatment effects were not always significant, values by the total amount of N applied in each manure
measurements of soil NO⫺
3–N concentrations at plant
(Table 7). On average, fall application of manure gave
growth stage V6 and apparent ear leaf chlorophyll and N higher N fertilizer equivalency values and higher N
sup-concentrations at growth stage R1 indicated that spring-ply efficiencies than did spring application, and
com-applied fresh manure supplied less N to the plants before posted manure provided more consistent N benefits than
and during flowering than did the other manure treat-did fresh manure. At the application rate used in this
ments. Thus, N deficits may have contributed to lower experiment, spring-applied fresh manure produced
in-yields in the spring-applied fresh-manure treatment com-consistent N benefits.
pared with the other manure treatments. Increasing It is not surprising that fall application of manure
spring-applied fresh hoop manure application rates to tended to be more effective in supplying N to corn, given
meet crop N demands may be detrimental to plant emer-the longer time and greater number of accumulated heat
gence and may increase soil N immobilization. units associated with fall, rather than subsequent spring,
In 2001, stalk NO⫺
3–N concentrations in the manure
application. Nevertheless, monitoring of soil N losses
treatments were low (⬍500g g⫺1) compared with the
and net N mineralization in response to the timing of
stalk NO⫺
3–N concentrations of urea N treatments
de-manure application would help to clarify whether the
spite similar grain yields (Tables 5 and 6; Fig. 2). A observed N fertilizer equivalencies and N supply
effi-similar pattern was observed in the soil NO⫺
3–N
concen-ciencies were due to patterns of N transformation and
trations in the late spring of 2001 relative to grain yield release or other non-N-related factors. More research
where manure treatments resulted in soil NO⫺
3–N
con-is needed to address thcon-is question.
centrations below levels predicted to provide for opti-mal yield despite similar yields to urea N treatments.
Fall Stalk Nitrate Concentration
This finding supports the concept that soils freshlyamended with biologically active organic materials have Nitrate concentration in the lower portion of a corn
stalk (the section between 15 and 35 cm above the soil different N dynamics than those amended with mineral N fertilizers (Magdoff, 1991; Cambardella et al., 2003). surface) at plant maturity has been used as an indicator
of late-season soil NO⫺
3–N concentrations and/or envi- A more detailed examination of the seasonal N
mineral-ization and crop N uptake patterns in response to fresh ronmental stress (Binford et al., 1992). A stalk NO⫺
3–N
concentration of⬎2000g g⫺1 indicates excessive soil or composted hoop manure is needed to determine
when and if supplemental N fertilizers may increase N NO⫺
3 or stress whereas concentrations⬍200g g⫺1
indi-cate insufficient inorganic soil N for maximum economic use efficiencies.
Although we observed similar mean N supply effi-grain yield (Binford et al., 1992).
In our study, urea application resulted in positive ciencies for fall-applied fresh manure (24.3%) and spring-applied compost (25.0%) (Table 7), the potential stalk NO⫺
3 responses in both years (Table 5). The
signifi-cant quadratic responses that were observed typically for large N losses during composting of fresh hoop ma-nure (Garrison et al., 2001) suggests that fall-applied occur as plant-available soil N becomes greater than the
plant’s ability to assimilate NO⫺
3 into amino acids (Bin- fresh manure may be more desirable than spring-applied
compost for whole-farm N conservation. However, ni-ford et al., 1992). In both years, all manure treatments
resulted in stalk NO⫺
3–N concentrations ⬍500 g g⫺1, trate leaching potential could be relatively high with
fall-applied fresh manure, which might result in negative and the mean stalk NO⫺
3–N concentration of manure
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