Soil properties following long-term application of

Soil properties following long-term application of stockpiled feedlot manure containing straw or wood-chip bedding under barley silage production J. J. Miller1, B. W. Beasley1, C. F. Drury2, X. Hao1, and F. J. Larney1

Can. J. Soil. Sci. Downloaded from pubs.aic.ca by Agriculture and Agri-food Canada on 09/02/14 For personal use only.

1

Agriculture and Agri-Food Canada, 5403-1st Ave. South, Lethbridge, Alberta, Canada T1J 4B1; and 2Agriculture and Agri-Food Canada, 2585 County Road 20, Harrow, Ontario, Canada NOR 1GO. Received 17 September 2013, accepted 20 January 2014. Published on the web 5 February 2014. Miller, J. J., Beasley, B. W., Drury, C. F., Hao, X. and Larney, F. J. 2014. Soil properties following long-term application of stockpiled feedlot manure containing straw or wood-chip bedding under barley silage production. Can. J. Soil Sci. 94: 389402. The influence of long-term land application of stockpiled feedlot manure (SM) containing either wood-chip (SM-WD) or straw (SM-ST) bedding on soil properties during the barley (Hordeum vulgare L.) silage growing season is unknown. The main objective of our study was determine the effect of bedding material in stockpiled manure (i.e., SM-WD vs. SM-ST) on certain soil properties. A secondary objective was to determine if organic amendments affected certain soil properties compared with unamended soil. Stockpiled feedlot manure with SM-WD or SM-ST bedding at 77 Mg (dry wt) ha 1 yr 1 was annually applied for 13 to 14 yr to a clay loam soil in a replicated field experiment in southern Alberta. There was also an unamended control. Soil properties were measured every 2 wk during the 2011 and 2012 growing season. Properties included water-filled pore space (WFPS), total organic C and total N, NH4-N and NO3-N, water-soluble nonpurgeable organic C (NPOC), water-soluble total N (WSTN), denitrification (acetylene inhibition method), and CO2 flux. The most consistent and significant (P50.05) bedding effects on soil properties in both years occurred for total organic C, C:N ratio, and WSTN. Total organic C and C:N ratio were generally greater for SM-WD than SM-ST, and the reverse trend occurred for WSTN. Bedding effects on other soil properties (WFPS, NH4-N, NO3-N, NPOC) occurred in 2012, but not in 2011. Total N, daily denitrification, and daily CO2 flux were generally unaffected by bedding material. Mean daily denitrification fluxes ranged from 0.9 to 1078 g N2O-N ha1 d1 for SM-ST, 0.8 to 326 g N2O-N ha1 d 1 for SM-WD, and 0.6 to 250 g N2O-N ha 1 d1 for the CON. Mean daily CO2 fluxes ranged from 5.3 to 43.4 kg CO2-C ha1 d1 for SM-WD, 5.5 to 26.0 kg CO2-C ha1 d 1 for SM-ST, and from 0.5 to 6.8 kg CO2-C ha1 d1 for the CON. The findings from our study suggest that bedding material in feedlot manure may be a possible method to manage certain soil properties. Key words: Denitrification, nitrogen, nitrous oxide, carbon dioxide, bedding, straw, wood-chips, manure, irrigation, barley Miller, J. J., Beasley, B. W., Drury, C. F., Hao, X. et Larney, F. J. 2014. Proprie´te´s du sol apre`s une application prolongeé de fumier de parc d’engraissement stocke´ en meule et renfermant de la litie`re de paille ou de copeaux de bois dans le cadre de la culture d’orge d’ensilage. Can. J. Soil Sci. 94: 389402. On ignore quels effets l’application prolongeé de fumier de parc d’engraissement stocke´ en meule (FM) et contenant de la litie`re soit de copeaux de bois (FM-CB), soit de paille (FM-PA) peut avoir sur les proprie´te´s du sol durant la pe´riode ve´ge´tative de l’orge d’ensilage (Hordeum vulgare L.). L’e´tude devait principalement e´tablir les conse´quences du mate´riau servant de litie`re et pre´sent dans le fumier (a` savoir FM-CB c. FMPA) sur certaines proprie´te´s du sol. Un objectif secondaire consistait a` de´terminer si les amendements organiques modifient certaines proprie´te´s du sol, comparativement au sol non bonifie´. Les auteurs ont applique´ annuellement 77 Mg (poids sec) de FM-CB ou de FM-PA par hectare pendant de 13 a` 14 ans a` un loam argileux, dans le cadre d’une expe´rience sur le terrain, re´pe´teé, dans le sud de l’Alberta. L’expe´rience incluait une parcelle te´moin, sans amendement du sol. Les proprie´te´s du sol ont e´te´ mesureés toutes les deux semaines durant la pe´riode ve´ge´tative de 2011 et 2012 et comprenaient l’espace des pores emplis d’eau (WFPS), la concentration totale de C organique et de N, la concentration de N-NH4 et de N-NO3, la concentration de C organique hydrosoluble non purgeable (NPOC), la concentration totale de N hydrosoluble (WSTN), la deńitrification (me´thode de l’inhibition par l’ace´tyle`ne) et les flux de CO2. Les effets les plus cohe´rents et les plus significatifs (P 5 0,05) de la litie`re sur les proprie´te´s du sol observe´s au cours des deux anneés prećiteés se rapportent au C organique total, au ratio C:N et au WSTN. En geńe´ral, le C organique total et le ratio C:N e´taient plus e´leve´s avec le FMCB qu’avec le FM-PA, la tendance inverse ayant e´te´ observeé pour le WSTN. Les effets de la litie`re sur les autres proprie´te´s du sol (WFPS, N-NH4, N-NO3, NPOC) ont e´te´ observe´s en 2012, mais pas en 2011. La concentration totale de N, la deńitrification quotidienne et les flux quotidien de CO2 ne sont geńe´ralement pas affecte´s par le mate´riau composant la litie`re. Les flux de deńitrification quotidiens moyens variaient de 0,9 a` 1 078 g de N-N2O par hectare et par jour pour le FM-PA, de 0,8 a` 326 g de N-N2O par hectare et par jour pour le FM-CB et de 0,6 a` 250 g de N-N2O par hectare et par jour

Abbreviations: C:N, organic C:organic N ratio; NPOC, nonpurgeable organic C; SM, stockpiled manure; TOC, total organic C; WFPS, water-filled pore space; WD, wood chips; WSTN, watersoluble total N Can. J. Soil Sci. (2014) 94: 389402 doi:10.4141/CJSS2013-087

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390 CANADIAN JOURNAL OF SOIL SCIENCE pour la parcelle te´moin. Les flux quotidiens moyens de CO2 variaient de 5,3 a` 43,4 kg de C-CO2 par hectare et par jour pour le FM-CB, de 5,5 a` 26,0 kg de C-CO2 par hectare et par jour pour le FM-PA et de 0,5 a` 6,8 kg de C-CO2 par hectare et par jour pour la parcelle te´moin. Ces re´sultats laissent croire que le mate´riau employe´ comme litie`re dans les parcs d’engraissement puis utilise´ comme fumier pourrait servir a` ge´rer certaines proprie´te´s du sol.


Mots cle´s: Deńitrification, azote, oxyde nitreux, dioxyde de carbone, litie`re, paille, copeaux de bois, fumier, irrigation, orge

Most feedlots on the Canadian prairies use bedding during the winter to increase cattle performance, improve the comfort, health and welfare of the animals, as well as to reduce the amount of mud or manure ‘‘tag’’ on cattle hides (McAllister et al. 1998; Feeder Associations of Alberta Ltd. 2000). Barley straw is the main bedding used, since it is readily available from nearby fields where feed barley is grown. However, in some years, when barley straw is in short supply or markets fluctuate, other bedding materials such as wood chips or shavings may be used (McAllister et al. 1998). The effect of feedlots shifting from barley straw to wood-chip bedding and subsequent long-term land application of manure containing these two bedding materials on soil properties is unknown. Bedding material in manure may be a possible practice to manage carbon and nitrogen cycling in soils, and minimize N losses to the environment. Very few studies have compared soil properties under long-term application of feedlot manure containing either wood chip or straw bedding. A long-term field experiment was initiated in 1998 at Lethbridge, in southern Alberta. This region has the highest concentration of feedlots in Canada. The influence of bedding material in stockpiled or composted feedlot manure on soil nutrients and salinity was studied after 1 to 3 yr of annual application of amendments (Miller et al. 2004, 2005), while available N and P and accumulation of N, P, and Cl in soil profiles were examined after nine annual applications (Miller et al. 2010), and the distribution of N and P in dry-sieved aggregates after 11 annual applications (Miller et al. 2012). These studies were generally based on soil sampling once per year, usually in the fall after harvest and prior to application of amendments. However, the influence of even longerterm ( 11 yr) bedding materials in stockpiled feedlot manure on soil physical and chemical properties during the growing season has not been studied. Wood chips and barley straw have very different physical and chemical properties that may affect soil properties when these bedding materials are applied to cropland with feedlot manure during the long term. Wood chips generally degrade much slower than straw because of higher lignin content and larger particles of wood chips and bark peelings (Allison and Anderson 1951; Bollen and Lu 1957; Allison 1965; Saliling et al. 2007). Wood particles are also generally less soluble in water compared with straw (Harper and Lynch 1982; Horvath 2006). Water absorption by wood chips versus straw will depend on moisture content of wood, whether the barley straw is chopped or unchopped, and

the proportion of finer particles, such as sawdust, in the wood-chip mixture. A moisture content of B30% is critical to maximize the absorbency of wood chips (The Welsh Assembly Government 2006). Water absorption is greater for un-chopped compared with chopped barley straw because of the reduction in weight of water held by capillary action within the straw stems (Schofield 1988). A greater proportion of sawdust in wood chips will increase water absorption, since absorption increases with decreasing particle size. Stockpiled manure with wood-chip bedding has 42% greater total C and 52% greater C:N ratio compared with stockpiled manure with straw bedding (Miller et al. 2009a). In contrast, stockpiled manure with straw bedding has a greater pH (by 0.7 units), 1.7-fold greater NO3-N, 1.2-fold greater NH4-N, and 4% greater total N compared with wood-chip bedding (Miller et al. 2009a). The higher C:N ratio of stockpiled manure with wood chips (22:1) compared with straw (15:1) bedding (Miller et al. 2009a) may also cause N immobilization in soils amended with manure and wood chips (Sommerfeldt and MacKay 1987). Although soil N immobilization under stockpiled manure with wood chips (SM-WD) was not evident after short-term (41 d) aerobic incubation (Miller et al. 2010), longer-term (44 wk) incubation found that mineralization rate constants (k) were lower for soil amended for 8 yr with SM-WD compared with stockpiled manure with straw (SM-ST) (Medhi et al. 2010). Miller et al. (2010) found that bedding effects on soil N mineralization depended on year, with no consistent trend. Miller et al. (2012) reported that N mineralization was similar in soil amended with stockpiled or compost manure containing wood chips versus straw bedding for smaller (B0.47 to 1.2 mm diam.) dry-sieved aggregates. However, in larger (]1.2 to 12.7 mm) soil aggregates, soil N mineralization occurred under straw, whereas N immobilization occurred under wood chips. The main objective of our study was to compare the influence of long-term (1314 yr) land application of stockpiled feedlot manure containing either wood chip or barley straw bedding on soil C and N status, denitrification, and CO2 emissions. The influence of bedding materials on water-filled pore space (WFPS) was also examined. We hypothesized that bedding material would have a significant effect on these selected soil properties because of their different physical and chemical properties. A secondary objective was to compare the effect of the organic amendments on certain soil properties compared to unamended control.


MILLER ET AL. * SOIL PROPERTIES FOLLOWING FEEDLOT MANURE

MATERIALS AND METHODS Study Design The field experiment was initiated in the fall of 1998 on a clay loam (290 g kg1 clay, 420 g kg1 sand) Dark Brown Chernozemic soil at the Agriculture and AgriFood Research Centre at Lethbridge, Alberta (lat. 498 38?N, long. 112848?W). The current study was conducted in 2011 and 2012 and utilized a subset of the original larger randomized complete block experiment as previously described by Miller et al. (2009a). The experimental treatments were 77 Mg ha1 yr1 (dry wt) rate of stockpiled feedlot manure containing either straw or wood-chip bedding. In addition, an unamended control was included. Each of the three treatments was replicated four times. Individual plots were 6 m 25 m in size. The feedlot manure was stockpiled for up to 2 mo prior to land application. Annual beef manure application rates in this area range from approximately 13 to 57 Mg ha1 (dry wt), with a mean value of 38 Mg ha1 (Porcupine Corral Cleaning Ltd., personal communication 2005). Details of the feedlot, pen manure and bedding material (Miller et al. 2003) were previously reported. Bedding materials were un-chopped barley straw (ST) and wood chips (WD) as described by Miller et al. (2009a). The wood-chip bedding (Sunpine Forest Products, Sundre, AB) consisted of a mixture of 50% wood chips, bark, and post peelings, and 50% fine sawdust. The tree source was a 4:1 mixture of lodgepole pine (Pinus contorta var. latifolia Engelm.) and white spruce [Picea glauca (Moenich) Voss]. The organic amendments were applied annually to the plots in the fall (late October to late November) of each year from 1998 to 2011 using a box-style manure spreader with horizontal beaters, and incorporated to a depth of approximately 20 cm using an offset disc cultivator. The extraction procedures and chemical analyses of the amendments applied have been previously reported (Miller et al. 2003). The barley (Hordeum vulgare) cultivar Duke was grown from 1999 to 2004, the cultivar Kasota from 2005 to 2010, and the cultivar Vibar in 2011 and 2012. The crop was harvested in August at the silage, softdough, or Zadok’s growth stage 85. The crop was seeded on May 16 and harvested on Aug. 16 in 2011; respective dates in 2012 were May 16 and Aug. 08. The barley was irrigated with a side-roll system to meet crop water use requirements. Irrigation amounts of 25.4, 50.8, and 38.1 mm were applied on Jul. 05, Jul. 18, and Oct. 03 in 2011. Irrigation amounts of 50.8, 50.8, 25.4, and 44.5 mm were applied on Jul. 06, Jul. 10, Jul. 18, and Sep. 10 in 2012. Soil Denitrification and Carbon Dioxide Flux Measurements Daily denitrification and CO2 fluxes were measured on intact soil cores incubated (24 h) in the field, using the acetylene inhibition technique (Method 37.7, Drury et al. 2008), and as previously outlined in detail by

391

Miller et al. (2012). Duplicate soil cores (6 cm i.d. 10 cm long) were taken from each of the treatment plots in all four replicates using a sliding-hammer hand probe with sample holder for soil core. This gave a total of eight cores per treatment. Denitrification measurements were conducted every 2 wk between May 17 and Aug. 22 in 2011 and between May 16 and Aug. 14 in 2012. Details of the core sampling, incubation, and calculation of daily denitrification flux (g N2ON ha1 d1) were previously reported (Miller et al. 2012). The same calculation methods were also used to determine daily CO2-C flux (kg CO2-C ha1 d 1). Measurement of CO2 flux on the soil cores where acetylene (C2H2) has been added may slightly overestimate absolute values of daily CO2 flux (Guo et al. 2012). However, 72 h incubation is the time needed for a typical soil microbial community to start metabolizing C2H2 (Guo et al. 2012), and our incubation was only 24 h. In addition, our primary focus was on relative differences among treatments, and the same amount of acetylene was added to all soil cores from all treatments. Soil Analysis Volumetric water content, WFPS, and soil bulk density were calculated for each soil core used to determine gas flux. The WFPS was calculated as the quotient of volumetric water content divided by soil porosity (Liu et al. 2007). Soil porosity was calculated using soil bulk density and assuming a mean particle density of 2.65 g cm 3. Separate soil cores (010 cm) were taken using a handprobe for NH4 and NO3 analysis. A 10-g sub-sample was collected from the soil core, mixed with 50 mL KCl (2 M), and shaken at low speed for 1 h. Ammonium-N was measured using the Berthelot reaction with salicylate on the autoanalyzer (Rhine et al. 1998). Nitrate-N was measured on an autoanalyzer using the hydrazine reduction method (Kempers and Luft 1988). Total N and total C in soil were determined on unacidified soil samples using the Dumas automated combustion technique (McGill and Figueiredo 1993) and the CNS analyzer (Carla Erba, Milan, Italy). Acidified soil samples were analyzed to determine total organic C (TOC), and then total inorganic C was calculated from the difference from total C. Water soluble non-purgeable organic C (NPOC) and total N (WSTN) were determined on 1:100 extracts (2 g air-dried soil:200 mL water). High extraction ratios were used to obtain sufficient extract for analysis, and similar to Zhang et al. (2011), all extractions were conducted on air-dried samples. Samples were shaken for 30 min, centrifuged at 5000 rpm for 10 min, and then filtered through 0.45-mm syringe filters. The extracts were then analyzed for dissolved NPOC and WSTN using Shimadzu TOC-VCSH/TNM-1 Organic Carbon and Total Nitrogen Analyzer (Shimadzu Scientific, Inc., Columbia, MD). The pH of surface (015 cm) soil was measured on three dates in 2011 (Jun. 22, Jul. 25, Aug. 11) and 2012 (Jun. 19, Jul. 20, Aug. 08).

392 CANADIAN JOURNAL OF SOIL SCIENCE


A 1:2 (5 g: 10 mL) soil:water mixture was prepared, shaken for 1 h, and the pH measured on soil slurry using a pH meter. Statistical Analysis A MIXED model analyses (Littell et al. 1998; SAS Institute Inc. 2005) was conducted by year on waterfilled pore space, C and N status, denitrification, and CO2 emissions in the 2 yr (20112012) of this study. A REPEATED statement for sampling date with compound symmetry covariance structure was utilized. Treatment and sampling dates were fixed effects in the model, replicate was a random effect. The UNIVARIATE procedure with normal plot option was utilized to test the normality of the sample and if a logarithmic transformation (log1) was required. Main treatment and interaction effects were evaluated using least squares means (LSM). A probability level of P50.05 was considered significant for F statistic values and LSM comparisons. A protected least-significant difference (LSD) test was used to compare LSM values. Multiple step-wise regression was conducted to determine the relationships between daily denitrification and CO2 rates (arithmetic values) and independent variables potentially affecting daily gas emissions. Entry of the independent variable into the model was considered significant at the P 50.15 level. RESULTS AND DISCUSSION Precipitation, Irrigation, and Air Temperature Precipitation during the growing season (May 01Aug. 31) was 26% greater in 2011 than the long-term mean, and was close (4% greater) to the long-term mean in 2012 (Table 1). Fifty percent more irrigation water was applied in 2012 than 2011 due to differences in precipitation between these 2 years. However, total water from precipitation and irrigation was only slightly greater (2.2%) in 2012 compared with 2011. Mean air temperature in both years was slightly lower than long-term mean, and it was 1.38C greater in 2012 than in 2011. Water-filled Pore Space There was a significant treatment by date effect on WFPS in 2011 (Table 2). Mean values were similar for SM-ST and SM-WD for all eight dates in 2011 (Fig. 1a). Mean values on Jun. 13, Jun. 28, Jul. 14, and Aug. 22 Table 1. Precipitation (May 01 to Aug. 31) and irrigation applied to experimental plots at Lethbridge in 2011 and 2012

Year

Precipitation (mm)

Irrigation (mm)

Total water applied (mm)

Mean air temp. (8C)

2011 2012 LTMz

277.7 229.2 220.1

114.3 171.5

392.0 400.7

14.2 15.5 16.3

z

LTM, long-term mean at Agriculture and Agri-Food Research Center at Lethbridge (19812010).

were greater for the unamended control compared with the two organic amendments. The opposite trend occurred on May 17 when mean values were greater for SM-WD compared with the control. We were surprised by the lower WFPS for amended than unamended surface soil since most studies have generally reported a positive response of soil water retention across a wide range of water potentials (Miller et al. 2002). It is unlikely that differences in infiltration caused this unexpected finding since infiltration measured at adjacent long-term manure plots was greater in amended than unamended soils (Miller et al. 2002). It is possible that more organic matter in the amended soils caused greater infiltration into the sub-surface depths, and therefore lowered the water content in the surface soil. Seasonal changes in surface crusting and hydrophobicity may also have contributed to the unexpected finding for amended versus unamended soils. Treatment had a significant effect on WFPS in 2012 (Table 2), when mean values were greatest for SM-ST, followed by SM-WD, and then the CON (Fig. 1b). Overall, bedding had no influence on WFPS for the eight sampling dates in 2011 (despite the significant treatment date interaction), and it was 10% greater for SM-ST than SM-WD when averaged for the seven dates in 2012 (no interaction). This was consistent with similar mean moisture content of SM-WD and SM-ST (Miller et al. 2009a) that was applied to these soils. Water absorption by different bedding materials depends on the physical (e.g., particle size, structure, dry matter, water content) and chemical properties (e.g., hydrophobicity) of the materials. Previous research showed contrasting findings of liquid or water absorption by wood-chips or straw bedding. Some studies reported that fine sawdust absorbed more liquid than chopped straw (Midgley 1950), or that straw bedding in dairy cattle pens absorbed more liquid effluent than wood-chip bedding (Davies 2006). In contrast, others have reported greater liquid absorption by straw than wood shavings or sawdust (Millar 1955). The proportion of fine sawdust relative to bark peelings and wood-chips likely determines the relative liquid absorbency of straw versus wood-chip bedding. A moisture content ofB30% is also critical to maximize the absorbency of wood chips (The Welsh Assembly Government 2006). Miller et al. (2000) reported that water absorption (gravimetric) by unchopped barley versus wood chips was dependent on the interaction with time. Water absorption was twofold greater for wood chips than barley straw after 2 h, it was similar at 5.5 and 56.5 h, and water absorption was twofold greater for barley straw than wood-chips after 113 h. The lower water absorption by wood-chips than straw at 113 h was likely due to the wood-chips becoming saturated to30% water content, which likely reduced absorption. The greater WFPS for SM-ST than SMWD in 2012 for our study may be related to the greater longer-term absorption of water by straw compared with wood-chips.


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Table 2. Treatment (T) and sampling date (D) effects on water-filled pore space (WFPS), total organic C (TOC), total N (TN), C:N ratio, NH4-N, NO3N, water-soluble non-purgeable organic C (NPOC), water-soluble total N (WSTN), daily denitrification (DN), and daily CO2-C flux in 2011 and 2012 Treatment

WFPS

TOC

TN

C:N

NH4-N

NO3-N

NPOC

WSTN

DN

CO2-C

2012 T D T D Transf.

* *** NS log

*** *** *** log

*** ** * unt

*** NS *** unt

*** *** NS log

*** *** ** log

*** *** * unt

*** NS *** log

*** *** *** log

*** *** * log

z

Probability levels: *(0.10), **(0.05), ***(0.001). Transf.transformation for MIXED model analysis. untuntransformed or arithmetic values, log log transformed values.

y

a) 1 CON SM-ST SM-WD

0.8 a

a

b b

0.6

b

a

b

b ab b

a

ab b

b

Aug 8

0.4

a b

a

Aug 22

WFPS (m3m–3)

b

Jul 26

Jul 14

Jun 28

Jun 13

0

Jun 2

0.2

May 17

Total Organic Carbon, Total Nitrogen, and C:N Ratio There was a significant treatment by date effect on total organic C in 2011 and 2012 (Table 2). Mean total organic C values were greater for SM-WD compared with SM-ST for five of seven dates in 2011 (Fig. 2a). Mean total organic C values were significantly greater for SM-WD compared with SM-ST for all seven dates in 2012 (Fig. 2b). Mean total organic C values were always greater for amended treatments compared with CON in both years. Our finding of generally greater total organic C in soil amended with SM-WD compared with SM-ST in both years was consistent with the 42% greater total organic C content of SM-WD than CM-ST (Miller et al. 2009a). It was also consistent with greater cumulative total C (inorganicorganic) applied (19982010) for the SM-WD treatment (173 Mg ha1) compared with the SM-ST treatment (130 Mg ha 1). Treatment had a significant effect on total N in 2011 (Table 2). Mean values in 2011 were similar for SM-ST and SM-WD, but mean values were fourfold greater for amended treatments than the CON (Fig. 2c). There was a significant treatment by date interaction on total N in 2012 (Table 2). Mean values were generally similar between the two organic amendments except for Jun. 25, when mean values were greater for SM-WD compared with SM-ST (Fig. 2d). Mean total N values were always greater for organic amendments compared with unamended CON. Our finding of no bedding effect on total N concentration was consistent with similar mean concentrations of total N in SM-WD (15.8 g kg1) and SM-ST (16.4 g kg 1) amendment (Miller et al. 2009a). In addition, cumulative total N applied in the SM-ST treatment (8.4 Mg ha1) was only slightly greater than for SM-WD (7.7 Mg ha1), which was consistent with similar total N in our soil during 2011 and 2012. There was a significant treatment by date effect on the C:N ratio in 2011 and 2012 (Table 2). Mean C:N values were significantly greater for SM-WD than SM-ST for five of seven sampling dates in 2011 (Fig. 3a), and for all seven sampling dates in 2012 (Fig. 3b). This trend of

2011 b) 1

0.8 WFPS (m3m–3)


2011 ---------------------------------------------------------------------------- Prob.Fz ---------------------------------------------------------------------------Treatment (T) *** *** *** *** *** *** *** *** NS *** Date (D) *** *** NS * *** *** *** *** *** *** T D *** * NS ** *** *** *** NS *** *** unt unt unt unt log unt log log log log Transf.y

0.6 a b

b

0.4

0.2

0

2012

Fig. 1. Treatment effects on water-filled pore space (WFPS) in 2011 (a) and 2012 (b). Vertical bars are mean values plus one standard error. The treatments are unamended control (CON), and 77 Mg ha1 annual rate of stockpiled feedlot manure (SM) with straw (SM-ST) or wood chips (SM-WD). For each sampling date, means with the same letters (or no letters) are not significantly different at P 50.05.

394 CANADIAN JOURNAL OF SOIL SCIENCE a)

c) 10 CON SM-ST SM-WD a

a

a

a

100

b a

a

b

a

aa

b b

b

6

4 b

50 c

Aug 8

c

0

Aug 22

c

Jul 26

Jun 28

Jun 13

c

Jun 2

2

b

Jul 14

b

May 17

0

a

a

8 Total N (g kg–1)

150

c

2011

2011 b)

d) 200

10

a aa

a a

b b

b

50

2

b

b

b

b

c

b

b

2012

0

Aug 14

c

Jul 23

Jul 9

c

Aug 14

c

c

Jun 12

c

Jun 25

c

May 16

c

0

4

Jul 23

b

a

Jul 9

b

b

a

a

a

Jun 25

b

a

b

6

Jun 12

a

100

a

a

a a

May 30

a

a

May 16

a

Total N (g kg–1)

150

a

a

8

May 30

Total organic C (g kg–1)


Total organic C (g kg–1)

200

2012

Fig. 2. Treatment effects on total organic C in 2011 (a) and 2012 (b), and on total N in 2011 (c) and 2012 (d). Vertical bars are mean values plus 1 standard error. The treatments are unamended control (CON), and 77 Mg ha 1 annual rate of stockpiled feedlot manure (SM) with straw (SM-ST) or wood chips (SM-WD). For each sampling date, means with the same letters are not significantly different at P50.05.

greater C:N ratio for SM-WD than SM-ST was consistent with 52% greater mean C:N ratio for SM-WD (22.2) compared with SM-ST (14.6) amendment (Miller et al. 2009a). Mean C:N values in 2011 ranged from 11.4 to 14.2 for SM-WD, and from 10.1 to 12.3 for SM-ST; and in 2012 ranged from 13.6 to 14.8 for SM-WD compared with 9.9 to 10.4 for SM-ST. The higher C:N ratio of softwoods (400:1) compared with straw (100:1) often results in greater net N immobilization and depression of nitrate concentrations in soil under wood chips (Sommerfeldt and MacKay 1987). Mean C:N ratios B15 in our study for soil amended with SM-WD and SM-ST suggested limited release of available N over the short-term. Qian and Schoenau (2002) reported limited mineralization over the short-term (67 d) when the organic C:N ratio was between 13 and 15, and it tended to decrease N availability in the short-term if the ratio was 15.

Ammonium and Nitrate There was a significant treatment by date effect on NH4-N in 2011 (Table 2). Mean values were similar for SM-ST and SM-WD for seven of the eight sampling dates (Fig. 4a). The one exception was on May 17, when the mean was greater for SM-ST compared to SM-WD. Mean NH4-N values in 2011 were greater for amended treatments compared to the CON (Fig. 4a). Treatment had a significant main effect on NH4-N in 2012 (Table 2), when mean values were greatest for SM-WD, followed by SM-ST, and then the CON (Fig. 4b). Overall, mean NH4-N in the soil was similar for the two amendments in 2011. The differences on May 14 are likely due to differences in NH4 content for the two amendments that were applied during the previous fall. For this particular year, these differences in amendment NH4 content may have persisted into the following

MILLER ET AL. * SOIL PROPERTIES FOLLOWING FEEDLOT MANURE a) 25 CON SM-ST SM-WD

C:N ratio

20 a

15

a b

10

c

c

a

b

b

a

a

a ab

b

b

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spring due to below-normal temperatures and slower denitrification. The greater mean values for SM-WD than SM-ST in 2012 were surprising since mean NH4-N concentration was 21% greater for SM-ST compared to SM-WD amendment (Miller et al. 2009a), and N mineralization is generally greater in soils with lower C:N ratios (Havlin et al. 1999). However, Miller et al. (2010) also reported significantly greater NH4-N in soil (060 cm) for SM-WD than for SM-ST after nine annual applications of amendments (19982006). The relatively low concentrations of NH4-N (Fig. 3a, b) compared to NO3-N (Fig. 3c, d) in the soil suggests that soil nitrification may have converted most of the NH4-N

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in the soil to NO3, and greater nitrification for SM-ST than SM-WD may have contributed to greater NH4-N for SM-WD in 2012. There was a significant treatment by date effect on NO3-N in 2011 and 2012 (Table 2). Mean NO3-N values were similar for SM-ST and SM-WD for seven of the eight dates in 2011, and mean values were mostly similar between amended treatments and the CON (Fig. 4c). The one exception was on May 17 when mean values were considerably greater for SM-ST compared to SMWD. Mean NO3-N values were greater for SM-ST than SM-WD for six of seven dates in 2012, and mean values were always greater for amended treatments compared with CON (Fig. 4d). Overall, mean NO3-N concentrations were generally similar for the two bedding materials for most sampling dates in 2011, but they were greater for SM-ST than SM-WD in 2012. The mean NO3-N was 69% greater for SM-ST compared with SM-WD amendment (Miller et al. 2009a). The large burst of NO3-N for the amended soils on May 17 in 2011 was likely due to high NH4-N at this time, and the latter may have been caused by greater N mineralization in the spring. An increased supply of NH4 will generally increase nitrification or conversion of NH4 to NO3 (Havlin et al. 1999), and NH4 supply is the single most important environmental factor influencing soil nitrification (Paul 2007). Miller et al. (2010) reported that bedding effects on soil NO3-N (060 cm) varied with application rate or year. Soil pH can also influence soil nitrification, with greater nitrification rates with increased pH and lower rates with increased acidification (Cheng et al. 2013). Soil pH was significantly lower for SM-WD (7.5490.04) than SM-ST (7.8390.04) in 2011. It was also significantly lower for SM-WD (7.6990.03) than SM-ST (7.8190.04) in 2012. However, the soil pH was only 2 to 4% lower for SM-WD than SM-ST in both years, and all pH values were mildly to moderately alkaline (7.58.0). Therefore, the wood chips in SM-WD did not likely decrease the soil pH sufficiently to affect soil nitrification. This was likely due to the low ratio of bedding to manure, and more dominant effect of manure increasing soil pH relative to wood chips decreasing soil pH. An increase in soil pH from cattle manure application is due to buffering from bicarbonates and organic acids (Whalen et al. 2000). Water-soluble Non-purgeable Organic Carbon and Total Nitrogen There was a significant treatment by date interaction effect on NPOC in 2011 and 2012 (Table 2). Bedding had a significant effect on mean NPOC values for two of seven dates in 2011, when mean values were greater for SM-WD than SM-ST on Jun. 13 and Jul. 26 (Fig. 5a). Mean NPOC values were greater for SM-WD than SMST on four (May 30, Jun. 12, Jun. 25, Jul. 09) of seven dates in 2012 (Fig. 5b). Mean NPOC values in 2011 and

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2012 were always greater for the organic amendments compared with unamended CON. Greater NPOC for SM-WD than SM-ST for four of seven sampling dates in 2012 may have been due to more rapid decomposition of more soluble C in SM with ST than WD. Wood decomposes or is mineralized more slowly than straw because wood contains less available and water-soluble carbohydrate and more resistant lignin than straw (Allison and Anderson 1951; Bollen and Lu 1957; Allison 1965). Softwoods generally contain about 28% lignin compared with 18% for cereal straw (Epstein 1997). In addition, since more soluble carbon materials in soils are more rapidly decomposed (Chantigny 2003), the shorter half-life of NPOC in soil with SM-ST than SM-WD may have contributed to greater NPOC in soil amended with SM-WD in 2012.

It is possible that greater leaching of NPOC for SMST than SM-WD by rainfall and irrigation during the growing season may have resulted in lower concentration of NPOC in the surface (010 cm) soil for SM-ST compared with SM-WD. There was a main treatment effect on WSTN in 2011 (Table 2). Mean WSTN values were significantly greater by 2- to 10-fold for SM-ST compared with SM-WD and the CON (Fig. 5c). There was a significant treatment by date effect on WSTN in 2012 (Table 2), when mean values were greatest for SM-ST, followed by SM-WD, and then the CON on all dates except for May 30 and Jun. 25 (Fig. 5d). On May 30, WSTN was significant greater for SM-ST than SM-WD and the CON, and on Jun. 25, it was greater for two amended treatments compared with CON. Overall, WSTN was significantly

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Fig. 5. Treatment effects on water-soluble non-purgeable organic C (NPOC) in 2011 (a) and 2012 (b), and water-soluble total N (WSTN) in 2011 (c) and 2012 (d). The treatments are unamended control (CON), and 77 Mg ha 1 annual rate of stockpiled feedlot manure (SM) with straw (SM-ST) or wood chips (SM-WD). For each sampling date, means with the same letters are not significantly different at P50.05.

greater for SM-ST compared with SM-WD in both years. Greater WSTN for SM-ST than SM-WD was likely due to greater water solubility of straw compared with wood-chips. Cereal straw has a maximum water solubility of 10% (Harper and Lynch 1982) compared with a maximum value of 4% for pine wood (Horvath 2006). The smaller particle size of straw compared with the much larger particles of wood chips, bark, and post peelings may have also enhanced water solubility, as solubility decreases with increasing particle size (Horvath 2006). Our finding was also consistent with greater physical degradation of straw than wood chips (Saliling et al. 2007), and this suggested a greater potential for organic N release to water. Straw also decomposes or is mineralized faster than wood chips because straw contains more available and water-soluble

carbohydrate and less resistant lignin than wood (Allison and Anderson 1951; Bollen and Lu 1957; Allison 1965). Mean values of NPOC and WSTN were generally greater for the amended treatments compared with the unamended control in both years (Fig. 5). Previous studies reported significant increases in water-extractable organic C and organic N immediately following application of organic amendments such as manure or crop residues, and this has generally been attributed to the presence of soluble materials in the amendments (Chantigny 2003). However, this soluble material is often rapidly decomposed in soil, and water-extractable C and N may return rapidly to background levels. We sampled the soil during the growing season following amendment application the previous fall. Therefore, the long period


Soil Denitrification Flux Mean daily denitrification fluxes ranged from 0.9 to 1,078 g N2O-N ha1 d1 for SM-ST, 0.8 to 326 g N2O-N ha1 d1 for SM-WD, and 0.6 to 250 g N2ON ha1 d1 for the CON (Fig. 6a, b). Denitrification rates in nonfertilized and N-fertilized, nonirrigated and irrigated agricultural soils range from 0 to 655 g N2ON ha1 d 1, with a mean rate of 36 g N2O-N ha 1 d1 (Barton et al. 1999). Lowrance (1998) reported daily

denitrification rates of 1,762 g N2O-N ha1 d 1 for soils amended with liquid manure, which was similar to our maximum value. Paul and Zebarth (1997) reported daily denitrification values B200 to 500 g N2O-N ha1 d1 for manured soil during the fall and winter following dairy cattle slurry application, and daily values B100 g N2O-N ha1 d1 for unamended soils. There was a significant treatment by date effect on daily denitrification in 2011 and 2012 (Table 2). There was a significant difference between bedding materials for only one of eight sampling dates in 2011, when mean daily values were greater for SM-ST than SM-WD on Jun. 13 (Fig. 6a). Mean daily denitrification values were generally similar for the amended treatments and greater than the CON at the beginning of the season. Mean daily denitrification values in 2012 were significantly different for the two bedding treatments for only one of seven dates, when mean values were greater for c)

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of time between amendment application and soil sampling may have resulted in us measuring lower absolute concentrations of NPOC and WSTN. However, spring tillage, irrigation, and increased root growth during the growing season may also have enhanced microbial activity and mineralization of organic matter (Chantigny 2003), and this may have increased short-term water-extractable C and N in our soil during the growing season.

2012

Fig. 6. Treatment effects on daily denitrification in 2011 (a) and 2012 (b), and daily CO2-C flux in 2011 (c) and 2012 (d). The treatments are unamended control (CON), and 77 Mg ha 1 annual rate of stockpiled feedlot manure (SM) with straw (SM-ST) or wood chips (SM-WD). For each sampling date, means with the same letters (or no letters) are not significantly different at P50.05.



SM-ST compared with SM-WD on Jun. 12 (Fig. 6b). Mean daily values for amended treatments were significantly greater than the CON for three (May 16, May 30, Jul. 23) of seven dates in 2012. Overall, daily denitrification was generally similar for SM-ST and SM-WD over both years. Inconsistent bedding effects on daily soil denitrification flux may have been due to factors such as variability in denitrification rate, number of replicate cores, the lag period between gas measurements in relation to manure application the previous fall (contributing to low absolute emissions), and other factors such as soil moisture that may have exerted greater control on denitrification (Miller et al. 2012). Our finding of no bedding effect on daily denitrification was consistent with other researchers who reported similar daily denitrification rates for biofilter media with wood chips or wheat straw (Kim et al. 2003; Saliling et al. 2007). Hao et al. (2004) also found similar cumulative N2O emissions from windrow composts of feedlot manure with either straw or wood chips. In contrast, Warneke et al. (2011) reported greater NO3 removal and hourly denitrification rates in biofilters with wheat straw compared with pine wood chips. Water-soluble total N was the most influential factor that influenced daily denitrification and explained 28% of this gas variation (Table 3). In contrast, water-soluble NPOC explained only 0.8% of daily denitrification. This indicated that daily denitrification in our soils was more related to labile organic N rather than C, and suggested that specific water-soluble organic N compounds in soil acted as electron donors for denitrification. Previous studies have reported that soil denitrification was strongly influenced by water-soluble C (Burford and Bremer 1975; Paul and Beauchamp 1989; Miller et al. 2009b), Table 3. Multiple linear regression (step-wise) analysis describing the relationship between mean daily denitrification (arithmetic values) and daily CO2 flux versus selected independent variables Regression parametersz Parametery

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Multiple linear step-wise regression equation is: ybob1x1b2x2 . . . bkxk where y is dependent variable, bo is the intercept, and bi (i1, . . . k) the partial regression coefficient associated with independent variable xi. y WFPSwater-filled pore space, WSTNwater-soluble total N, NPOCnon-purgeable organic C, Tempincubation temperature, TOCtotal organic C of soil.

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but we are not aware of any studies that have reported the greater influence of water-soluble total N compared with C on soil denitrification. The greater influence of water-soluble N on daily denitrification compared with total organic N also suggested that this gas flux was more dependent on labile rather than stable N. Soil denitrification is strongly influenced by the supply of water-soluble or readily decomposable organic matter or available carbon (Bremner and Shaw 1958; Burford and Bremner 1975; Havlin et al. 1999; Miller et al. 2008, 2009b). However, some studies have found that denitrification in long-term manured soils was more related to total organic C (labile and stable C) rather than just labile water-soluble C (Goulding and Webster 1989). Water-filled pore space was the second most influential factor on daily denitrification, and explained 10% of this gas flux (Table 3). The importance of soil water content (and temperature) in controlling fluxes of N2O is linked primarily to the biological nature of N transformations (Heller et al. 2010). Miller et al. (2012) reported that WFPS had the greatest influence on daily soil denitrification under fresh versus composted manure on these same experimental plots. Waterlogging of soil causes rapid denitrification by impeding the diffusion of O2 to sites of microbiological activity (Havlin et al. 1999). Carbon Dioxide Flux Mean daily CO2 fluxes ranged from 5.3 to 43.4 kg CO2-C ha 1 d1 for SM-WD, from 5.5 to 26.0 kg CO2-C ha1 d 1 for SM-ST, and from 0.5 to 6.8 kg CO2-C ha1 d1 for the CON (Fig. 6c, d). Our maximum daily CO2 fluxes were similar to values reported by Collins et al. (2010), greater than those reported by Ellert and Janzen (2008), and lower than those found by Heller et al. (2010), and all three studies used the chamber method. In a 2-yr study in Washington, USA, Collins et al. (2010) reported daily CO2 up to 45 kg CO2-C ha1 d1 for unamended soils and up to 60 kg CO2-C ha1 d1 for soil amended with liquid dairy manure. Ellert and Janzen (2008) reported maximum daily CO2 fluxes of 0.034 kg CO2C ha1 d1 for soil with and without manure and cropped to corn at Lethbridge. However, they applied beef manure only once every 5 yr, which may account for their lower emissions. Heller et al. (2010) reported maximum daily emissions of 72 to 480 kg CO2-C ha1 d1 for unamended and amended (chicken manure) soils in a 3-yr study in Israel where amendments were annually applied. There was a significant treatment by date effect on daily CO2 flux in 2011 and 2012 (Table 2). There was a significant difference between bedding materials for mean CO2 fluxes on three (Jun. 28, Aug. 08, and Aug. 22) of eight dates in 2011, when mean values were greater for SM-WD compared with SM-ST (Fig. 6c). There was a significant difference between bedding materials on mean CO2 fluxes for only one of seven dates in 2012, when mean values were greater for SM-WD compared



with SM-ST on Jun. 25 (Fig. 6d). Mean fluxes in 2011 and 2012 were consistently greater for amended treatments compared with unamended CON. Overall, daily CO2 fluxes were generally similar for SM-ST and SM-WD. For the few dates when significant differences did occur, daily CO2 fluxes were greater for SM-WD than SM-ST. It is possible that greater soil respiration for SM-WD may have been due to greater aeration of soil caused by larger particles of wood chips. Hao et al. (2004) hypothesized that the presence of wood chips in windrow compost piles may increase convection of air through the windrows, thereby increasing the supply of O2, thereby increasing aerobic decomposition. However, they found similar cumulative CO2-C emissions in compost windrows of feedlot manure with barley straw or wood chips. Total organic C had the greatest influence on daily CO2 flux and explained 35% of this gas emission (Table 3). Water-soluble C and N had no significant influence on daily CO2 flux. The significant influence of total organic C but not water-soluble C (or N) on daily CO2 flux suggested that soil respiration was more dependent on stable rather than labile C. Soil CO2 emissions are influenced by soil temperature, soil moisture, vegetation type, substrate quantity and quality, microbial biomass and activity, as well as land use and management (Ding et al. 2007). Heller et al. (2010) reported that CO2 flux in soils amended with corn residues and pasteurized chicken manure for 3-yr were most influenced by concentration of NH4-N in the soil. Waterfilled pore space was the second most dominant factor influencing daily CO2 flux and explained 12% of the variation (Table 3). High bursts of soil CO2 immediately after irrigation have been reported in short-term (2-yr) studies (Reicosky et al. 1999) and longer-term (8-yr) studies (Mariko et al. 2007). Contrasting findings of possible dominant factors influencing CO2 fluxes between our and other studies may be related to the different time periods of measurement, climate, soil, and other environmental factors. There was a weak but significant correlation between daily CO2 and denitrification fluxes (r0.22, P 0.0026), which suggested that the two gas emissions were decoupled or not synchronized. Ellert and Janzen (2008) reported that hourly CO2 and N2O emissions were sometimes intertwined and related such as after legume or manure was incorporated, but were decoupled at other times such as in the spring when sporadic bursts of N2O occurred. They also found that CO2 fluxes followed seasonal trends and peaked during the growing season, whereas N2O showed no consistent trends and emissions occurred sporadically in bursts throughout the year. CONCLUSIONS The findings from our study showed that total organic C, C:N ratio, and WSTN were significantly affected by bedding material in both years; other properties were

only affected in 2012 (WFPS, NH4-N, NO3-N, NPOC); and the remainder (total N, daily denitrification, daily CO2 flux) were generally unaffected. Total organic C and the C:N ratio in both years were significantly greater for SM-WD than SM-ST, but WSTN was greater for SM-ST than SM-WD. In 2012, WFPS and NO3-N were significantly greater for SM-ST than SMWD, and NH4-N and NPOC were greater for SM-WD than SM-ST. Our findings suggest that these amendments may be used to manage total organic C, C:N ratio, and water-soluble total N in a clay loam soil. Future research is also needed to examine soil properties when feedlot manure containing a mixture of straw and wood-chip bedding is used in feedlots and then applied to cropland.

ACKNOWLEDGEMENTS Field and laboratory assistance was provided by Chloe Bryant. Wayne Calder of Agriculture and Agri-Food Canada in Harrow, Ontario, conducted the N2O and CO2 gas analysis. We thank Brett Hill for conducting the non-purgeable organic C and water-soluble total N analysis, Clarence Gilbertson for the total C, total organic C, and total N analysis, and Bonnie Tovell for conducting NH4-N and NO3-N analysis. Allison, F. E. and Anderson, M. S. 1951. The use of sawdust as mulches and soil improvement. USDA, Circular No. 891, Washington, DC. Allison, F. E. 1965. Decomposition of wood and bark sawdusts in soil, nitrogen requirements, and effects on plants. USDAARS Tech. Bull. No. 1332. Washington, DC. Barton, L., McLay, D. A., Schipper, L. A. and Smith, C. T. 1999. Annual denitrification rates in agricultural and forest soils: a review. Aust. J. Soil Res. 37: 10731093. Bollen, W. B. and Lu, K. C. 1957. Effect of Douglas-fir sawdust mulches and incorporations on soil microbial activities and plant growth. Soil Sci. Soc. Am. J. 21: 12351241. Bremner, J. M. and Shaw, K. 1958. Denitrification in soil. II. Factors affecting denitrification. J. Agric. Sci. 51: 4052. Burford, J. R. and Bremner, J. M. 1975. Relationships between the denitrification capacities of soils and total, water-soluble and readily decomposable soil organic matter. Soil Biol. Biochem. 7: 389394. Chantigny, M. H. 2003. Dissolved and water-extractable organic matter in soils: A review on the influence of land use and management practices. Geoderma 113: 357380. Cheng, Y., Wang, J., Mary, B., Zhang, J., Cai, Z. and Chang, S. X. 2013. Soil pH has contrasting effects on gross and net nitrogen mineralizations in adjacent forest and grassland soils in central Alberta, Canada. Soil Biol. Biochem. 57: 848857. Collins, H. P., Streubel, J. D., Frear, C., Chen, S., Granatstein, D., Kruger, C., Alva, A. K. and Fransen, S. F. 2010. Application of AD dairy manure effluent to fields and associated inpacts. Center for Sustaining Agriculture and Natural Resources (CSANR), CSANR Research Rep. No. 2010-001. Washington State University, Pullman, WA. [Online] Available: http://csanr.wsu.edu/publications/researchreports/CFF% 20Report/CSANR2010-001.Ch10.pdf [2014 Jan. 09]


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