Final Report Title: PI and Co-PIs: PI Address: PI Phone: PI Fax: PI Abstract Introduction

Transcription

1 Final Report Title: Application of Dairy Slurry on Alfalfa Fields, and Subsequent Effects on Nutritive Value and Silage Fermentation Characteristics of the Harvested Forage PI and Co-PIs: Wayne Coblentz (PI), Richard E. Muck (Co-PI), Mark Borchardt (Co-PI), Susan Spencer (Co-PI), Bill Jokela (Co-PI), Mike Bertram (Co-PI), and Ken Coffey (Co-PI) PI Address: 2615 Yellowstone Drive, Marshfield, WI PI Phone: PI Fax: PI Abstract Frequently, dairy producers ask questions about the potential risks of applying dairy manure, usually in liquid or slurry form, to growing alfalfa. In many cases, this management option is considered when storage reservoirs are approaching capacity during summer months. One caution associated with this management practice is the potential to inoculate alfalfa with sources of clostridia from the dairy slurry, thereby risking subsequent undesirable clostridial silage fermentations. The objectives of this project were to assess the effects of dairy-slurry application on the subsequent nutritive value and fermentation characteristics of alfalfa balage. During 2012, dairy slurry was applied to the second (HARV1) and third cutting (HARV2) of alfalfa at an overall mean rate of 42,100 L/ha. Twelve 0.17-ha plots received dairy slurry i) immediately after the previous harvest (stubble), ii) after one week of regrowth, or iii) after two weeks of regrowth. Four 0.17-ha control plots receiving no dairy slurry also were evaluated as controls. Applications of dairy slurry had no effect on dry matter (DM) yield; mean yields for HARV1 and HARV2 were 2,477 and 781 kg DM/ha, respectively. Generally, applications of dairy slurry did not exhibit any meaningful effect on the nutritive value of pre- or post-ensiled alfalfa, nor were fermentation characteristics of the silages affected. Clostridium tyrobutyricum, which is known to negatively affect cheese production, was not detected in the dairy slurry, nor was it found in pre-ensiled forage or fermented silages. Counts for Clostridium cluster 1 were greater for slurry-applied plots compared to controls; there also was evidence across these studies that delaying slurry application for one or two weeks following the previous harvest resulted in further increases in counts of Clostridium cluster 1. Based on these results, applications of dairy slurry are less risky when applied directly to stubble, but risks increase when applications are delayed until after alfalfa has initiated regrowth. Introduction Dairy producers frequently inquire about the potential risks of applying dairy slurry onto alfalfa during summer months. Usually, these inquiries occur when storage reservoirs are approaching capacity, and the dairy producer has a very urgent need to remove manure from the storage reservoir. A number of problems have been associated with this management practice (Lory et al., 2000; Ketterings et al., 2006; Rankin, 2006), including salt or ammonium burn, smothering as a result of excessive application rates, damage from spreader wheel traffic, and potential inoculation of silage with undesirable bacteria, such as enterobacteria and clostridia (Buxton and O Kiely, 2003). Clostridial silages are characterized by a higher (less acidic) final ph, and by greater production of ammonia and butyric acid than occurs in normal silages. Our objectives for this

2 project were to assess the effects of dairy-slurry application on silage fermentation, clostridial counts, and the nutritive value of alfalfa silages conserved as balage. Materials and Methods This research was conducted on a 2.7-ha site located on the University of Wisconsin Marshfield Agricultural Research Station (Stratford, WI). Sixteen m (0.17-ha) research plots were established with a north-south orientation; plots were divided into four field blocks based on topography (slope). Within each field block, one plot was randomly assigned to the following treatments: i) control (no slurry applied); ii) slurry applied to alfalfa stubble; iii) slurry applied after one week of regrowth; or iv) slurry applied after two weeks of regrowth (Figure 1). Block 1 Block 2 Block 3 Block 4 C 7 14 S S 14 C 7 7 C 14 S 14 7 S C Figure 1. Treatment assignments for dairy slurry applications: C = control, no slurry applied; S = slurry applied immediately after harvest onto alfalfa stubble; 7 = slurry application delayed 7 days after harvest; and 14 = slurry application delayed 14 days after harvest. The first cutting of Pioneer 55V48 alfalfa was harvested as silage on 1 June 2012, and dairy slurry was applied to alfalfa stubble on 4 June. Subsequent (delayed) applications occurred on 11 and 18 June. Dairy slurry was broadcast-applied at a mean rate of 42,400 ± 5,271 L/ha with a Calumet Model 5000 Spreader (Calumet-Imperial Industries, Wausau, WI) configured such that the distribution pattern was comparable in width to the 14-m wide plots (Figure 2). The mean characteristics and composition of the dairy slurry were: density = 1.07 ± kg/l; DM = 5.7 ± 1.84%; N = 3.9 ± 0.52 %; NH4-N = 1.7 ± 0.32%; P = 0.77 ± 0.105%; K = 4.1 ± 0.92%; S = 0.30 ± 0.026; ash = 36.1 ± 6.56%; C:N ratio = 9.7 ± 1.02; and Clostridium cluster 1 = 6.89 ± log10 genomic copies/g (University of Wisconsin Soil and Forage Laboratory, Marshfield, WI; Coblentz et al., 2014). Clostridium tyrobutyricum, which negatively affects cheese production, was not detected within the dairy slurry. On 10 July, alfalfa from the 16 field plots was mowed and conditioned (Case-International Harvester Model WD1903; CNH America LLC, Racine, WI), and then merged and packaged in m large-square bales (Case-International Harvester Model LB333) the next day (Figure 3). A total of 33 bales were produced (HARV1), which

3 included at least two bales from each plot. For HARV1, one bale from each plot was made at 46.2% moisture (IDEAL) and a second bale at 34.5% moisture (DRY). Figures 2 and 3. Application of slurry to alfalfa plots (Figure 2; left) and baling of alfalfa prior to wrapping as silage (Figure 3; right). All bales from HARV1 were tagged, measured, weighed, and sampled before they were wrapped (Model 995 TSR; McHale Engineering Limited; Ballinrobe, Co. Mayo, Ireland) with 7 layers (28 table revolutions) of plastic stretch film (BENCO Ploy Films, LLC; Leola, PA). Bales were then stored on a concrete pad until a final sampling date (29 May 2013). Dairy slurry application treatments were repeated following HARV1 on 12, 20, and 26 July for the stubble, one-week delay, and two-week delay application treatments, respectively. Alfalfa forage was mowed, conditioned, baled, and wrapped as described previously on 10 and 11 August (HARV2) at 49.1% moisture. Initially, our intention was to evaluate the effects of repeated slurry applications over a series of harvests; however, weather conditions during July and early August became increasingly droughty, and forage yields for HARV2 were reduced to about 1/3 of those observed for HARV1 (2,477 vs. 781 kg DM/ha). As a result, for HARV2, only one abbreviated bale (mean length = 0.89 m) was made from each plot at an ideal moisture concentration for balage (49.1%). Wrapped bales from HARV2 (n = 16) also were stored on a concrete pad until a final sampling date on 31 May All bales were sampled on a pre- and post-storage basis and analyzed for nutritive value, ph, buffering capacity (BC), water-soluble carbohydrates (WSC), starch, silage fermentation products, and counts of Clostridium cluster 1. The counts of Clostridium cluster 1 were performed by qpcr techniques described in detail by Coblentz et al. (2014). Results from HARV1 were analyzed as a split-plot design with slurry-application treatments as wholeplots and moisture concentrations (IDEAL or DRY) as sub-plots. For HARV2, the design was condensed to a randomized complete block with slurry-application strategies as treatments because of the lack of forage needed to produce both IDEAL and DRY bales from each plot. Treatment means were compared with the following orthogonal contrasts: i) no slurry (control) vs. all slurry treatments; ii) immediate (stubble) application vs. delayed applications; iii) one vs. twoweek delayed applications; and iv) IDEAL vs. DRY bale moisture (HARV1 only).

4 Results and Discussion Yield. For both HARV1 and HARV2, there were no significant contrasts (P 0.193) comparing yields of DM from plots receiving various slurry-application strategies. Overall, plots from HARV1 yielded 2,477 kg DM/ha, but yields from HARV2 were greatly reduced (781 kg DM/ha), largely in response to droughty growing conditions. Nutritive Value. On a post-ensiled basis, differences for specific measures of nutritive value generally were not statistically significant; therefore data are summarized across treatments and presented and discussed only as overall means (Table 1). Generally, silages analyzed from HARV1 had numerically greater concentrations of fiber components, but less CP and energy (TDN) than observed for HARV2 silages. The fermentation process contributed to small changes in forage nutritive value between pre- and post-ensiled forages (data not shown). Overall, recoveries of DM were reasonable for these ensiling and storage techniques (95.6 ± 5.36%); under these conditions, the observed small losses of DM are likely respiratory in nature (Rotz and Muck, 1994), and typically result in minor increases in fiber components and CP, and small losses of energy (TDN). Our results were consistent with these generalizations. Table 1. Post-ensiled nutritive value (% of DM) for alfalfa balage harvested at Stratford (WI) during Item 2 HARV1 SEM HARV2 SEM NDF ADF Hemicellulose Cellulose Lignin CP NDICP ADICP Ash TDN Adapted from Coblentz et al. (2014). 2 Abbreviations: NDF, neutral-detergent fiber; ADF, acid-detergent fiber; CP, crude protein; NDICP, neutral-detergent insoluble CP; ADICP, acid-detergent insoluble CP; and TDN, total digestible nutrients. Indicators of Ensilability. For HARV1, no significant contrasts were observed for initial ph (6.06; P 0.360), BC (369 meq/kg DM; P 0.063), WSC (7.2%; P 0.099), and starch (0.62%; P 0.121). Similarly, there were no contrasts detected (P 0.083) for these response variables within HARV2, except for the contrast of control vs. slurry-applied plots for concentrations of WSC (6.0 vs. 5.4%; P = 0.037). For these response variables, the most notable numerical difference between HARV1 and HARV2 was associated with BC, which was substantially greater for HARV2 (438 meq/kg DM), thereby corroborating the better nutritive value observed for HARV2 forages (Table

5 1). Muck and Walgenbach (1985) have reported that proportions of leaf tissue and BC are positively related in alfalfa forages. On a post-ensiled basis, the only significant contrast (data not shown) was observed for differences in final (fermented) ph between IDEAL and DRY silages (5.54 vs. 5.61; P = 0.008) for HARV1. Two considerations should be noted with respect to this observation. First, the final overall ph for both HARV1 (mean = 5.58) and HARV2 (mean = 5.42) were relatively high for fermented forages; Muck (1990) has demonstrated that final silage ph and bale moisture are inversely related for alfalfa silages. Therefore, the final ph for the alfalfa balage produced in these experiments should be greater than observed for precision-chopped alfalfa silages that are frequently ensiled at moisture concentrations > 60%. Secondly, several researchers (Nicholson et al., 1991; Muck et al., 2003; Savoie and Jofriet, 2003) have noted that balage often undergoes no particle-size reduction. As a result, WSC are released slowly, thereby slowing the proliferation of lactic-acid producing bacteria and limiting silage fermentation rate. The slightly more acidic final ph for HARV2 reflects a greater final moisture concentration across all bales (50.6%) compared to HARV1 (43.4%). Silage Fermentation Products. As observed for measures of nutritive value, there was little effect of slurry-application treatments on products of silage fermentation; therefore, data are presented (Table 2) and discussed as overall means for each harvest. Throughout HARV1, bales with an initial moisture < 45% produced little or no detectable lactic acid (0.02 ± 0.057%), while wetter bales (> 45%) exhibited increased production (0.57 ± 0.578%). Lactic acid production was greater for HARV2 (overall mean = 1.43%), which reflects the higher initial moisture concentration within those bales. For both HARV1 and HARV2, typical end products of clostridial silage fermentations (butyric acid and NH3) were present in very minimal concentrations, indicating clostridial activity during fermentation had little effect on these alfalfa silage bales. Table 2. Fermentation products for alfalfa balage harvested at Stratford (WI) during ,2 Item 1 HARV1 SEM HARV2 SEM Lactic acid Acetic acid Succinic Acid Formic acid Butyric Acid Ethanol , 3-Butanediol NH3-N NH3-N, % of N All concentrations expressed on a % of DM basis unless otherwise specified. 2 Adapted from Coblentz et al. (2014). Enumeration of Clostridia. Following fermentation and storage over winter, core samples obtained from alfalfa silage bales indicated that counts of Clostridium cluster 1 were strongly affected by slurry-application strategies (Table 3). Within HARV1 bales, clostridial counts were

6 greater for slurry-applied bales than for control bales receiving no slurry (5.40 vs log10 genomic copies/g; P < 0.001), and counts for delayed applications were greater than those observed when slurry was applied to directly onto alfalfa stubble (5.51 vs log10 genomic copies/g; P = 0.018). Clostridial counts following application delays by one compared to two weeks did not differ (overall mean = 5.51 log10 genomic copies/g; P = 0.176), nor did comparisons of bales made at IDEAL or DRY moisture concentrations (P = 0.133). For HARV2, results were similar, except that counts for silage bales made following a two-week slurry application delay were greater than following a one-week delay (6.23 vs log10 genomic copies/g; P < 0.001). Clostridium tyrobutyricum was not detected in any silage bale. Table 3. Counts of Clostridium cluster 1 for alfalfa balage harvested at Stratford (WI) during ,2 Slurry Application Bale Moisture Contrasts (P > F) Treatment HARV1 HARV2 No slurry Stubble week delay week delay SEM IDEAL DRY SEM All slurry vs. no slurry < < Stubble vs. delayed < week vs. 2 week delay < IDEAL vs. DRY All counts expressed as log10 genomic copies/g. 2 Adapted from Coblentz et al. (2014). Conclusions and Comments Based on the clostridial counts from HARV1 and HARV2, risks of clostridial fermentations within alfalfa silages are greater whenever dairy slurry is applied; however, risks are lower when the slurry is applied to stubble compared to delayed applications onto growing plants. For this study, the use of balage techniques that require a reduced moisture concentration compared to precisionchopped silages likely limited the potential for clostridial fermentations. Reducing moisture concentrations by field wilting is a common recommendation for avoiding clostridial fermentations in precision-chopped silages (Albrecht and Beauchmin, 2003; Muck et al., 2003). Although we did not directly compare precision-chopped silages with balage in this study, these results suggest that a silage inoculant supporting production of lactic acid should be used whenever dairy slurry is applied to alfalfa stubble or regrowth. Furthermore, it may be prudent to consider

7 some additional field drying relative to traditional recommendations ( 70% moisture; Muck et al., 2003) for precision-chopped silages. We did not attempt to assess salt or ammonium burn, smothering, or wheel damage to alfalfa plants within our experimental design. However, visual observations made during these experiments suggest that slurry should be applied to alfalfa stubble, and any applications to growing alfalfa should be viewed as a last resort (Figure 4). If this is necessary, it may be better to apply slurry on old stands, rather than risk damage to recently established alfalfa plants. Figure 4. Salt or ammonium burn (left) and wheel-traffic damage (right) to alfalfa forages following applications of dairy slurry. In these studies, these potential problems did not result in statistical differences in forage yield. References Albrecht, K.A., and K.A. Beauchemin Alfalfa and other perennial legume silage. p In D.R. Buxton, R.E. Muck, and J.H. Harrison (ed.) Silage Science and Technology. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Madison, WI. Buxton, D.R., and P. O Kiely Preharvest plant factors affecting ensiling. p In D.R. Buxton, R.E. Muck, and J.H. Harrison (ed.) Silage Science and Technology. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Madison, WI. Coblentz, W.K., R.E. Muck, M.A. Borchardt, S.K. Spencer, W.E. Jokela, M.G. Bertram, and K.P. Coffey Effects of dairy slurry on silage fermentation characteristics and nutritive value of alfalfa. J. Dairy Sci. (in press). Ketterings, Q.M., E. Frenay, J.H. Cherney, K.J. Czymmek, S.D. Klausner, L.E. Chase, and Y. Schukken Application of manure to established alfalfa. Agronomy Fact Sheet Series. Fact Sheet #16. Cornell University Cooperative Extension, Ithaca, NY.

8 Lory, J.A., R.L. Kallenbach, and C.A. Roberts Managing manure on alfalfa hay. #G4555. University of Missouri Cooperative Extension, Columbia, MO. Muck, R.E., L.E. Moser, and R.E. Pitt Postharvest factors affecting ensiling. p In D.R. Buxton, R.E. Muck, and J.H. Harrison (ed.) Silage Science and Technology. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Madison, WI. Muck, R.E., and R.P. Walgenbach Variations in alfalfa buffering capacity. ASAE Paper No Am. Soc. Agric. Eng., St. Joseph, MI. Nicholson, J.W.G., R.E. McQueen, E. Charmley, and R.S. Bush Forage conservation in round bales or silage: effect on ensiling characteristics and animal performance. Can. J. Anim. Sci. 71: Rankin, M Applying manure to alfalfa. Focus on Forage. Vol. 8: No. 2. University of Wisconsin Cooperative Extension, Madison, WI. Rotz, C. A., and R. E. Muck Changes in forage quality during harvest and storage. p In G.C. Fahey et al. (ed.) Forage Quality, Evaluation, and Utilization. Proc. Natl. Conf. on Forage Quality, Evaluation, and Utilization, Lincoln NE Apr American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Madison, WI. Savoie, P., and J.C. Jofriet Silage storage. p In D.R. Buxton, R.E. Muck, and J.H. Harrison (ed.) Silage Science and Technology. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Madison, WI. Keywords: alfalfa, dairy slurry, clostridial fermentations, silage Acknowledgement: Partial funding for this study was provided by the Midwest Forage Research Program of the Midwest Forage Association.