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The Effect of Dairy Compost on Summer Annual Grasses Grown as Alternative Silages
90
et al. The ProfessionalMuir Animal Scientist 17:90–94
Effect of Dairy Compost on TheSummer Annual Grasses Grown as Alternative Silages J. P. MUIR*,1, S. R. STOKES†, PAS, and E. P. PROSTKO** Departments of *Soil and Crop Sciences and †Animal Science, Texas A&M University System, Stephenville, TX 76401 and **Department of Crop and Soil Sciences, University of Georgia, Tifton, GA 31793
Abstract
2, respectively), the hybrid Pennisetum (0.221% Yr 1 and 0.228% Yr 2, respectively) and the grain sorghum (0.193% Yr 1 and 0.199% Yr 2, respectively). Pearl millet had the greatest P uptake from the soil (25.9 kg ha-1 Yr 1 and 36.2 kg ha-1 Yr 2, respectively), while forage sorghum had the lowest P uptake from the soil (17.9 kg ha-1 Yr 1 and 13.4 kg ha-1 Yr 2, respectively).
throughout the farm system. Research has demonstrated a wide range SS20 forage sorghum (Sorghum of P uptake from forage crops, bicolor), SS10 sorghum-sudan (Sorghum ranging from 14.6 kg P ha-1 yr-1 (Poa annua) to 83.0 kg P ha-1 yr-1 (Sorghum spp. hybrid), SM60 pearl millet halepense; 12). (Pennisetum glaucum), Nutrifeed Corn silage is the preferred forage (Pennisetum spp. hybrid), and CA 737 in dairy rations because of its palatgrain sorghum (Sorghum bicolor) were ability and high-energy content. grown under irrigation at the However, corn lacks drought hardiStephenville Research and Extension ness and requires early spring seeding Center in the spring seasons of 1998 and (Key Words: Forages, Sorghum, that may interfere with autumn/ 1999. Dairy manure compost was Millet, Compost, Phosphorus.) winter small-grain forage production incorporated into subplots at 11.2 t DM in the South. As a result, alternative ha-1 each yr. The sorghum-sudan and forage sorghum hybrids produced consiscrops are needed for silage and hay tently high tonnage both years (P<0.05), production. Pearl millet (Pennisetum Recent interest in composting while the grain sorghum was among the americanum) and hybrids of pearl manure has arisen within the dairy lowest yields both years. Fiber concenmillet and napier grass (Pennisetum industry to facilitate storage and trations were lowest (P<0.05) for the purpureum) are drought-tolerant, transport (13). Composting should grain sorghum, and in sacco DM disapsummer annual grasses (3, 11). encourage better distribution of dairy Sorghum (Sorghum bicolor) varieties pearance and CP concentrations were manure over a more expansive consistently highest for both the grain have been developed for both forage sorghum and the hybrid Pennisetum. The acreage. This would help avoid soil and grain production. Forage phosphorus (P) overload or long-term sorghums have proven post-harvest application of compost over two seasons increased soil phosphorus (P) to 2.4 times buildup from manure application in regrowth that result in greater yields fields close to cattle housing (1). that of soil without compost and inthan corn (7), but nutritional value creased average forage P concentration by There is a movement in certain decreases quickly once seed producwatershed areas toward changing 32% the second year. Average forage P tion is initiated (9). Sorghum-sudan land application rates from a nitroconcentrations were highest (P<0.05) in hybrids (S. bicolor x Sorghum gen (N) basis toward a P basis; this the millet (0.214% Yr 1 and 0.258% Yr sudanense) are used almost exclusively movement could potentially increase as a ratooning hay crop (15) with land-area-requirement (LAR) per high quality and yield (14). The animal to 1.2 ha per animal (1). By objectives of this trial were to evaluselecting forage crops that extract ate summer annual grasses for their 1To whom correspondence should be ad- greater amounts of P, dairy producers agronomic traits (forage yield and P dressed: [email protected] could more efficiently cycle P uptake), nutritional characteristics
Introduction
Summer Annual Grasses as Alternative Silage Crops
TABLE 1. Agronomic data for summer silage monocots grown in central Texasa. Entry
Yr
SS20 forage sorghum
Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2
SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA737 grain sorghum
No. of DAP, first harvests harvestb 2 2 3 3 2 2 3 2 2 2
119 116 85 79 94 98 85 88 91 98
DAP, last harvestc
Days to maturity
205 180 205 181 157 168 205 166 157 171
103 90 68 60 79 84 68 83 79 86
aForage
sorghum, sorghum-sudan, pearl millet, and grain sorghum were harvested at soft dough; Nutrifeed pennisetum was a photoperiod-sensitive hybrid harvested at a 1.2-m height. bDAP = days after planting to first harvest. cDAP = days after planting to last harvest.
[CP, NDF, ADF, lignin and in sacco disappearance (ISD)], potential as alternatives for corn silage in dairy production systems, and responses to soil-applied manure compost.
Materials and Methods In early April 1998 (Yr 1) and 1999 (Yr 2), 8.5-m × 3.6-m plots were seeded with five commercially avail-
TABLE 2. Forage yields (kg DM ha-1) of summer grass silages grown in central Texasa. Harvest Item Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD aAveraged
First
Second
Third
Total
11,241b 8,423c 8,408c 6,757d 6,323d 0.001 544.0
5,612b 5,486b 3,455c 3,529c 4,153c 0.001 370.0
0 2,635 0 1,168 441 >0.50
16,853b 16,544b 11,863c 11,455c 10,917c 0.001 756.2
6,776c 4,339c 9,872b 6,411c 5,192c 0.001 821.0
1,921c 8,208b 3,801c 5,469bc 2,496c 0.001 662.9
0 4,048 0 0 0 >0.50
8,697de 16,595b 13,673bc 11,880cd 7,688e 0.001 1190.9
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. b,c,d,eMeans in the same column from the same year with different superscripts are significantly different (P<0.05) according to Duncan’s multiple range test.
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able summer, annual monocots (Table 1). Nutrifeed pennisetum, a Pennisetum spp. hybrid, is new to the U.S. market, and seed is currently being imported from New Zealand. The CA737 sorghum is a grain type and was included for comparison because of its possible use as highstarch silage. Sorghum-sudan and forage millet are widely utilized as a hay or green chop, whereas the forage sorghum has proven ensiling qualities. All entries were seeded at 10 kg seed ha-1 both years in 8.5-m rows, with 90 cm between rows. Plots were maintained free of weeds by manual removal. The same entries and manure levels were applied to the same plots and subplots, respectively, throughout both years. Plots were replicated four times as blocks: each was split, and dairy compost was applied at 11.2 t DM ha-1 yr-1 on half the plot. Compost analysis indicated an average P concentration of 0.58% and an average N concentration of 1.3%, DM basis. This P concentration is similar to that reported by Dou et al. (2) and close to that reported by Jones and Sanderson (8) for north Texas (0.55%). This was equivalent to 67.3 kg P ha-1 yr-1 and 134.6 kg P ha-1 total for the experiment. Soil in the experimental area was sampled to a 150-mm depth prior to the experiment. Samples had a pH of 6.5, 13 ppm P, 24 ppm NO3, 130 ppm K, 855 ppm Ca, and 124 ppm Mg (averaged across all plots). Each subplot was sampled at the end of the second season to determine treatment effects on soil P. Soil P was determined by NH4Oac-EDTA-extractable P procedure of Hons et al. (6). Ammonium nitrate was applied at 179.2 kg ha-1 yr-1 to subplots not receiving compost and at 33.6 kg ha-1 yr-1 to subplots receiving compost. This resulted in all subplots receiving an equal amount of total N. An additional 84 kg N ha-1 yr-1 was applied in July to all plots. From March through October, rainfall totaled 540 mm in Yr 1 and 355 mm in Yr 2. To supplement this soil moisture, 430 and 440 mm of irriga-
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tion water were applied during Yr 1 and 2, respectively. The inner 3.3 m2 of each subplot was harvested with a mower at a 12cm stubble height whenever entries reached soft-dough stage or attained a 1.2-m height (Nutrifeed pennisetum). As a result, different entries were harvested at different dates and number of times. Subsamples were dried at 55oC for 48 h to determine DM and then ground through a shear mill with a 2-mm screen. To determine P and N concentrations, samples were digested using a modification of the aluminum block digestion procedure of Gallaher et al. (4). Sample weight was 1.0 g, digested in 5 g of 33:1:1 K2SO4/CuSO4/ TiO2 up to 2 h at 400oC using 17 mL of H2SO4. Phosphorus and N in the digestate were determined by semiautomated colorimetry (5), using a Technicon Autoanalyzer II (Technicon Industrial Systems, Tarryton, NY). Lignin and ADF were determined using the procedures of Van Soest and Robertson (16). In sacco disappearance after 48 h was measured utilizing 2.5-g samples in 8 x 8 cm polyester cloth bags held in 381 x 483 mm polyester 10-mm mesh bags. Triplicate samples were weighed and placed in rumen-fistulated steers fed a 100% sorghum-sudan hay diet containing 13.5% CP. Following in sacco digestion, bags were washed until rinse water was clear and dried for 48 h at 55oC, and the remaining material was weighed to calculate ISD percentage. The experimental design was a complete randomized split-plot (four blocks) and ANOVA were run on dependent variables using MSTAT-C (Microcomputer Statistical Program; Michigan State University, Lansing, MI) (10). Forage species were the main plots,and compost was applied to subplots. Mean separations were determined by Duncan’s multiple range test when interactions between factors were not significant, but simple effects were significant. Years were not treated as a factor since compost application (applied to the same subplots both years) had a
Muir et al.
TABLE 3. Effect of compost application on forage yield, P, and CP concentrations in summer annual monocots grown in central Texas. Manure levela Item Yr 1 DM yield, kg ha-1 P, % DM P yield, kg ha-1 CP, % DM CP yield, kg ha-1 Yr 2 DM yield, kg ha-1 P, % DM P yield, kg ha-1 CP, % DM CP yield, kg ha-1
11.2 t
0t
P
SD
14,343 0.189 27.1 12.6 1,807
12,710 0.159 20.2 12.1 1,538
0.02 0.01 0.001 >0.50 0.03
478.2 0.0774 1.21 0.42 69.6
12,371 0.231 28.6 6.8 841
11,043 0.175 19.3 7.4 817
0.22 0.001 0.004 0.13 >0.50
753.2 0.0093 2.29 0.26 68.0
aManure
was applied at 0 or 11.2 t DM ha yr-1. Manure x entry interaction was nonsignificant (P>0.10) in both years.
with an increase in yield of 19% in Yr 2. The addition of compost to subplots increased DM yield, on average, for all entries, by 13% in Yr 1 There was a large variability in and 12% in Yr 2 (Table 3). This days after planting (DAP) for first increase was the same for all entries. harvests and intervals between cuts as This may have been a result of the determined by variable plant develop- increase in soil P as well as greater ment (Table 1). SS20 forage sorghum cation exchange capacity, which averaged the longest first harvest, 118 decreased fertilizer N loss and end, with an average of 97 d between hanced soil-moisture retention. harvests. SS10 sorghum-sudan and Fiber concentrations are listed in nutrifeed pennisetum had the shortTable 4. The CA737 grain sorghum est maturity (82 and 87 d, respecwas especially low in NDF, ADF, and tively), and averaged 64 and 76 d, lignin. Acid detergent fiber for respectively, between harvests. Com- CA737 grain sorghum in Yr 1 (26.8%) post did not appear to affect matuwas 26% lower (P<0.05) than the rity rates. average ADF value for the remaining First-harvest yields were greater four entries and 18% lower (P<0.05) than subsequent harvests for all in Yr 2 (29.5%). Lignin levels of Yr 1 entries except the sorghum-sudan in CA737 grain sorghum (2.95%) and Yr 2 (Table 2). Sorghum-sudan yields Nutrifeed (2.85%) were lower than were equal to or greater than (P<0.05) that of the other three entries. the other entries, averaging 16.5 t Nutrifeed had the lowest lignin DM ha-1 for Yr 1 and 16.6 DM ha-1 concentration in Yr 2 (3.68%). for Yr 2, although it required three Moisture stress may have increased harvests. The forage sorghum yields the fiber concentrations in Yr 2 since were 48% higher (P<0.05) in Yr 1 the overall average ADF that yr was (16.8 t DM ha-1) than in Yr 2 (8.7 t 11% higher, and lignin was 23% DM ha-1), indicating that this species higher than in Yr 1. The increase in may require more soil moisture than harvest intervals the second year also the other entries. In contrast, millet may have contributed to higher fiber appeared to require less moisture, content in Nutrifeed pennisetum.
cumulative effect on subplot soil characteristics.
Results and Discussion
Summer Annual Grasses as Alternative Silage Crops
TABLE 4. Fiber components and in sacco DM disappearance for summer silage grasses grown in central Texasa. Item
Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD
NDF
Lignin
ISDb
29.3e 32.5d 35.0c 32.5d 26.8f 0.001 0.60
3.58d 4.50c 4.40c 2.75e 2.95e 0.001 0.140
75.6d 71.6e 64.3f 79.5c 78.8c 0.001 1.21
33.3f 35.2e 38.8c 37.1d 29.5g 0.001 0.38
4.14ef 4.81d 5.66c 3.68f 4.20e 0.001 0.18
77.6c 73.4d 65.4e 77.6c 76.4c 0.001 0.55
ADF (% DM)
53.8e 56.7d 62.9c 63.1c 51.0f 0.001 0.83
aAveraged
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. bISD = in sacco DM disappearance. c,d,e,f,gMeans in the same column from the same year with different superscripts are significantly different (P<0.05) according to Duncan’s multiple range test.
TABLE 5. Crude protein and P concentration and P removal by summer silage grasses grown in central Texasa.
Item Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD aAveraged
P removed (kg ha-1)
CP (% DM)
P (% DM)
5.2d 7.6c 6.9c 9.9b 9.0b 0.001 0.67
0.107d 0.143c 0.214b 0.211b 0.193b 0.001 0.0122
17.9c 23.6bc 25.9b 24.6bc 21.1bc 0.05 1.93
0.155d 0.175cd 0.258b 0.228bc 0.199bcd 0.001 0.0147
13.4c 29.1bc 36.2b 27.4bc 16.8c 0.001 3.63
6.5 6.8 7.3 7.1 7.7 >0.10 0.41
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. All values are expressed on a DM basis. b,c,dMeans from the same year and in the same column followed by similar letters differ (P<0.05) according to Duncan’s multiple range test.
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The low NDF values during Yr 1 and high ISD rates for Yr 1 and Yr 2 in the grain sorghum and the forage sorghum indicate that these would be the forages of choice where high digestibility is desired (Table 4). In sacco disappearance rates were high for the pennisetum hybrid as well. Crude protein concentration was greatest in the pennisetum hybrid and CA 737 grain sorghum in Yr 1 (Table 5), but was undifferentiated among entries in Yr 2. Lower soil moisture during Yr 2 (66% of Yr 1 rainfall) may have stressed plants and lowered CP concentration. The SS20 forage sorghum CP was the lowest of all the entries, averaging 5.85% over both years. It is possible that more N fertilizer needed to be applied to the higher yielding entries in order to raise CP concentration in these. Compost application did not affect CP concentration in the herbage either year, perhaps because of a dilution factor as a result of higher yields. The application of composted manure increased herbage P concentration both years (P<0.05 Yr 1 and 2; Table 3). Averaged over all entries, P concentration was 0.159% in Yr 1 and 0.175% in Yr 2 when no compost was applied; concentrations rose to 0.189% (19% higher) in Yr 1 and 0.231 (32% higher) in Yr 2 in herbage from subplots where compost was applied. There were differences among entries as well, with the forage millet, pennisetum hybrid, and grain sorghum having as high or higher concentrations of P than the forage sorghum and sorghum-sudan both years (Table 5). When DM yield was multiplied by concentration, the forages from subplots with manure compost yielded 34 and 48% more P in Yr 1 and Yr 2, respectively, than from plots without manure (Table 5). Soil P in subplots with manure averaged 26.7 ppm after the second season. This was 2.4 times greater (P=0.001) than the water-soluble P available in subplots without manure. Soil P was not affected by forage species despite the differences in P uptake among plants (Table 5).
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When both yield and quality indicators are considered, forage sorghum had the most potential. However, in situations where cropping systems preclude autumn harvests to allow for earlier smallgrain planting, yields may be considerably lower. Where early secondharvest dates are desired, grain sorghum varieties may be more attractive. Crops such as forage sorghum and pearl millet, with proportionally heavier first harvests, would fit into single-harvest schemes. The application of composted manure had a positive effect on both forage yield and crop P concentration. Pearl millet was able to remove 46% of the P applied in the compost. However, the addition of compost resulted in a net increase of 16 ppm P to the soil by the second year. Because soil analysis indicates only what P will be available to the crop over the season (not total soil P), enhanced crop P uptake does not necessarily result in a P decrease in subsequent soil analysis.
Implications There is a trade-off in annual forage grasses between biomass production and forage quality. This is expected as taller, thicker stalks need stronger structural support. Ruminal disappearance of DM indicated that higher fiber contents resulted in lower rates of disappearance. Within cropping schemes including autumn small-grain planting, faster maturing, higher quality grain sorghum, or photoperiod-sensitive Nutrifeed
Muir et al.
pennisetum might have more application, despite lower production yields. Forage P concentrations were higher in the less productive grasses, indicating that P availability in the soil may have limited P uptake by the more productive plants. Efficiency of soil P extraction capacity has a potentially significant application in the selection of grass forages used in phytoremediation of high P soils or for improving the efficiency of P cycling in confined animal feeding operations with access to forage fields.
6. Hons, F. M., L. A. Larson-vollmer, and M.A. Locke. 1990. NH4Oac-EDTA-extractable phosphorus as a soil test procedure. Soil Sci. 149:249. 7. Jones, R. M., and J. C. Read. 1988. Effect of irrigation, nitrogen, and plant population on corn and sorghum grown for silage. Forage Research in Texas. Texas Agric. Exp. Stn. publication CPR 4593, College Station. 8. Jones, R. M., and M. A. Sanderson. 1996. Mineral composition and pH of dairy waste. Forage Research in Texas. C.P.R. 5258, TAEX, College Station, TX. 9. McCormick, M. E., D. R. Morris, B. A. Acherson and D. C. Blouin. 1995. Ratoon cropping forage sorghum for silage: yield, fermentation, and nutrition. Agron. J. 87:952. 10. MSTAT-C. 1993. User’s Guide to MSTATC. Michigan State University, East Lansing, MI.
Literature Cited 1. Auvermann, B. A. 1999. Manure and wastewater production and characteristics. In: Dairy Outreach Program Area Training Manual. S. R. Stokes (ed.). Texas Agricultural Extension Service, Stephenville, TX. 2. Dou, Z. J. D. Toth, R. Allshouse, C. F. Ramberg, and J. D. Ferguson. 2000. Phosphorus fraction distribution in animal waste. In Proc. 8th Int. Symp. Animal Agric. Food Processing Wastes. J. A. Moore (ed.). A.S.A.E., St. Joseph, MI, Oct. 9–11 Des Moines, IA. 3. Boddorff, D., and W. R. Ocumpaugh. 1985. Forage quality of pearl millet x napiergrass hybrids and dwarf napiergrass. Proc. Soil Crop Sci. Soc. Florida 45:170. 4. Gallaher, R. N., C. O. Weldon, and J. G. Futral. 1975. An aluminum block digester for plant and soil analysis. Soil Sci. Soc. Am. Proc. 39:803. 5. Hambleton, L. G. 1977. Semiautomated method for simultaneous determination of phosphorus, calcium, and crude protein in animal feeds. A.O.A.C. 60:845.
11. Muldoon, D. K., and C. J. Pearson. 1979. The hybrid between Pennisetum americanum and Pennisetum purpureum. Herbage Abstr. 49:189. 12. Piersynski, G. M., and T. L. Logan. 1993. Crop, soil, and management effects on phosphorus soils test levels. J. Prod. Agric. 6:513. 13. Rynk, R. 1994. Status of dairy manure composting in North America. Compost Sci. & Utilization Winter:20. 14. Sanderson, M. A., F. R. Miller, and R. M. Jones. 1995. Forage quality and agronomic traits of sorghum-sudangrass hybrids. Texas Agric. Exp. Stn. publication MP-1765, College Station. 15. Skerman, P. J., and R. Riveros. 1990. Tropical Grasses. FAO, Rome. p 695. 16. Van Soest, P. J., and J. B. Robertson. 1980. Systems of analysis for evaluating fibrous feeds. p. 49. In Standardization of Analytical Methodology for Feeds: Proc. Int. Workshop, Ottawa, ON. Mar. 12-14 1979. W. J. Pigden et al. (ed.) Rep. IDRC-134e. Int. Dev. Res. Ctr., Ottawa, ON, Canada, and Unipub, New York.
et al. The ProfessionalMuir Animal Scientist 17:90–94
Effect of Dairy Compost on TheSummer Annual Grasses Grown as Alternative Silages J. P. MUIR*,1, S. R. STOKES†, PAS, and E. P. PROSTKO** Departments of *Soil and Crop Sciences and †Animal Science, Texas A&M University System, Stephenville, TX 76401 and **Department of Crop and Soil Sciences, University of Georgia, Tifton, GA 31793
Abstract
2, respectively), the hybrid Pennisetum (0.221% Yr 1 and 0.228% Yr 2, respectively) and the grain sorghum (0.193% Yr 1 and 0.199% Yr 2, respectively). Pearl millet had the greatest P uptake from the soil (25.9 kg ha-1 Yr 1 and 36.2 kg ha-1 Yr 2, respectively), while forage sorghum had the lowest P uptake from the soil (17.9 kg ha-1 Yr 1 and 13.4 kg ha-1 Yr 2, respectively).
throughout the farm system. Research has demonstrated a wide range SS20 forage sorghum (Sorghum of P uptake from forage crops, bicolor), SS10 sorghum-sudan (Sorghum ranging from 14.6 kg P ha-1 yr-1 (Poa annua) to 83.0 kg P ha-1 yr-1 (Sorghum spp. hybrid), SM60 pearl millet halepense; 12). (Pennisetum glaucum), Nutrifeed Corn silage is the preferred forage (Pennisetum spp. hybrid), and CA 737 in dairy rations because of its palatgrain sorghum (Sorghum bicolor) were ability and high-energy content. grown under irrigation at the However, corn lacks drought hardiStephenville Research and Extension ness and requires early spring seeding Center in the spring seasons of 1998 and (Key Words: Forages, Sorghum, that may interfere with autumn/ 1999. Dairy manure compost was Millet, Compost, Phosphorus.) winter small-grain forage production incorporated into subplots at 11.2 t DM in the South. As a result, alternative ha-1 each yr. The sorghum-sudan and forage sorghum hybrids produced consiscrops are needed for silage and hay tently high tonnage both years (P<0.05), production. Pearl millet (Pennisetum Recent interest in composting while the grain sorghum was among the americanum) and hybrids of pearl manure has arisen within the dairy lowest yields both years. Fiber concenmillet and napier grass (Pennisetum industry to facilitate storage and trations were lowest (P<0.05) for the purpureum) are drought-tolerant, transport (13). Composting should grain sorghum, and in sacco DM disapsummer annual grasses (3, 11). encourage better distribution of dairy Sorghum (Sorghum bicolor) varieties pearance and CP concentrations were manure over a more expansive consistently highest for both the grain have been developed for both forage sorghum and the hybrid Pennisetum. The acreage. This would help avoid soil and grain production. Forage phosphorus (P) overload or long-term sorghums have proven post-harvest application of compost over two seasons increased soil phosphorus (P) to 2.4 times buildup from manure application in regrowth that result in greater yields fields close to cattle housing (1). that of soil without compost and inthan corn (7), but nutritional value creased average forage P concentration by There is a movement in certain decreases quickly once seed producwatershed areas toward changing 32% the second year. Average forage P tion is initiated (9). Sorghum-sudan land application rates from a nitroconcentrations were highest (P<0.05) in hybrids (S. bicolor x Sorghum gen (N) basis toward a P basis; this the millet (0.214% Yr 1 and 0.258% Yr sudanense) are used almost exclusively movement could potentially increase as a ratooning hay crop (15) with land-area-requirement (LAR) per high quality and yield (14). The animal to 1.2 ha per animal (1). By objectives of this trial were to evaluselecting forage crops that extract ate summer annual grasses for their 1To whom correspondence should be ad- greater amounts of P, dairy producers agronomic traits (forage yield and P dressed: [email protected] could more efficiently cycle P uptake), nutritional characteristics
Introduction
Summer Annual Grasses as Alternative Silage Crops
TABLE 1. Agronomic data for summer silage monocots grown in central Texasa. Entry
Yr
SS20 forage sorghum
Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2 Yr 1 Yr 2
SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA737 grain sorghum
No. of DAP, first harvests harvestb 2 2 3 3 2 2 3 2 2 2
119 116 85 79 94 98 85 88 91 98
DAP, last harvestc
Days to maturity
205 180 205 181 157 168 205 166 157 171
103 90 68 60 79 84 68 83 79 86
aForage
sorghum, sorghum-sudan, pearl millet, and grain sorghum were harvested at soft dough; Nutrifeed pennisetum was a photoperiod-sensitive hybrid harvested at a 1.2-m height. bDAP = days after planting to first harvest. cDAP = days after planting to last harvest.
[CP, NDF, ADF, lignin and in sacco disappearance (ISD)], potential as alternatives for corn silage in dairy production systems, and responses to soil-applied manure compost.
Materials and Methods In early April 1998 (Yr 1) and 1999 (Yr 2), 8.5-m × 3.6-m plots were seeded with five commercially avail-
TABLE 2. Forage yields (kg DM ha-1) of summer grass silages grown in central Texasa. Harvest Item Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD aAveraged
First
Second
Third
Total
11,241b 8,423c 8,408c 6,757d 6,323d 0.001 544.0
5,612b 5,486b 3,455c 3,529c 4,153c 0.001 370.0
0 2,635 0 1,168 441 >0.50
16,853b 16,544b 11,863c 11,455c 10,917c 0.001 756.2
6,776c 4,339c 9,872b 6,411c 5,192c 0.001 821.0
1,921c 8,208b 3,801c 5,469bc 2,496c 0.001 662.9
0 4,048 0 0 0 >0.50
8,697de 16,595b 13,673bc 11,880cd 7,688e 0.001 1190.9
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. b,c,d,eMeans in the same column from the same year with different superscripts are significantly different (P<0.05) according to Duncan’s multiple range test.
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able summer, annual monocots (Table 1). Nutrifeed pennisetum, a Pennisetum spp. hybrid, is new to the U.S. market, and seed is currently being imported from New Zealand. The CA737 sorghum is a grain type and was included for comparison because of its possible use as highstarch silage. Sorghum-sudan and forage millet are widely utilized as a hay or green chop, whereas the forage sorghum has proven ensiling qualities. All entries were seeded at 10 kg seed ha-1 both years in 8.5-m rows, with 90 cm between rows. Plots were maintained free of weeds by manual removal. The same entries and manure levels were applied to the same plots and subplots, respectively, throughout both years. Plots were replicated four times as blocks: each was split, and dairy compost was applied at 11.2 t DM ha-1 yr-1 on half the plot. Compost analysis indicated an average P concentration of 0.58% and an average N concentration of 1.3%, DM basis. This P concentration is similar to that reported by Dou et al. (2) and close to that reported by Jones and Sanderson (8) for north Texas (0.55%). This was equivalent to 67.3 kg P ha-1 yr-1 and 134.6 kg P ha-1 total for the experiment. Soil in the experimental area was sampled to a 150-mm depth prior to the experiment. Samples had a pH of 6.5, 13 ppm P, 24 ppm NO3, 130 ppm K, 855 ppm Ca, and 124 ppm Mg (averaged across all plots). Each subplot was sampled at the end of the second season to determine treatment effects on soil P. Soil P was determined by NH4Oac-EDTA-extractable P procedure of Hons et al. (6). Ammonium nitrate was applied at 179.2 kg ha-1 yr-1 to subplots not receiving compost and at 33.6 kg ha-1 yr-1 to subplots receiving compost. This resulted in all subplots receiving an equal amount of total N. An additional 84 kg N ha-1 yr-1 was applied in July to all plots. From March through October, rainfall totaled 540 mm in Yr 1 and 355 mm in Yr 2. To supplement this soil moisture, 430 and 440 mm of irriga-
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tion water were applied during Yr 1 and 2, respectively. The inner 3.3 m2 of each subplot was harvested with a mower at a 12cm stubble height whenever entries reached soft-dough stage or attained a 1.2-m height (Nutrifeed pennisetum). As a result, different entries were harvested at different dates and number of times. Subsamples were dried at 55oC for 48 h to determine DM and then ground through a shear mill with a 2-mm screen. To determine P and N concentrations, samples were digested using a modification of the aluminum block digestion procedure of Gallaher et al. (4). Sample weight was 1.0 g, digested in 5 g of 33:1:1 K2SO4/CuSO4/ TiO2 up to 2 h at 400oC using 17 mL of H2SO4. Phosphorus and N in the digestate were determined by semiautomated colorimetry (5), using a Technicon Autoanalyzer II (Technicon Industrial Systems, Tarryton, NY). Lignin and ADF were determined using the procedures of Van Soest and Robertson (16). In sacco disappearance after 48 h was measured utilizing 2.5-g samples in 8 x 8 cm polyester cloth bags held in 381 x 483 mm polyester 10-mm mesh bags. Triplicate samples were weighed and placed in rumen-fistulated steers fed a 100% sorghum-sudan hay diet containing 13.5% CP. Following in sacco digestion, bags were washed until rinse water was clear and dried for 48 h at 55oC, and the remaining material was weighed to calculate ISD percentage. The experimental design was a complete randomized split-plot (four blocks) and ANOVA were run on dependent variables using MSTAT-C (Microcomputer Statistical Program; Michigan State University, Lansing, MI) (10). Forage species were the main plots,and compost was applied to subplots. Mean separations were determined by Duncan’s multiple range test when interactions between factors were not significant, but simple effects were significant. Years were not treated as a factor since compost application (applied to the same subplots both years) had a
Muir et al.
TABLE 3. Effect of compost application on forage yield, P, and CP concentrations in summer annual monocots grown in central Texas. Manure levela Item Yr 1 DM yield, kg ha-1 P, % DM P yield, kg ha-1 CP, % DM CP yield, kg ha-1 Yr 2 DM yield, kg ha-1 P, % DM P yield, kg ha-1 CP, % DM CP yield, kg ha-1
11.2 t
0t
P
SD
14,343 0.189 27.1 12.6 1,807
12,710 0.159 20.2 12.1 1,538
0.02 0.01 0.001 >0.50 0.03
478.2 0.0774 1.21 0.42 69.6
12,371 0.231 28.6 6.8 841
11,043 0.175 19.3 7.4 817
0.22 0.001 0.004 0.13 >0.50
753.2 0.0093 2.29 0.26 68.0
aManure
was applied at 0 or 11.2 t DM ha yr-1. Manure x entry interaction was nonsignificant (P>0.10) in both years.
with an increase in yield of 19% in Yr 2. The addition of compost to subplots increased DM yield, on average, for all entries, by 13% in Yr 1 There was a large variability in and 12% in Yr 2 (Table 3). This days after planting (DAP) for first increase was the same for all entries. harvests and intervals between cuts as This may have been a result of the determined by variable plant develop- increase in soil P as well as greater ment (Table 1). SS20 forage sorghum cation exchange capacity, which averaged the longest first harvest, 118 decreased fertilizer N loss and end, with an average of 97 d between hanced soil-moisture retention. harvests. SS10 sorghum-sudan and Fiber concentrations are listed in nutrifeed pennisetum had the shortTable 4. The CA737 grain sorghum est maturity (82 and 87 d, respecwas especially low in NDF, ADF, and tively), and averaged 64 and 76 d, lignin. Acid detergent fiber for respectively, between harvests. Com- CA737 grain sorghum in Yr 1 (26.8%) post did not appear to affect matuwas 26% lower (P<0.05) than the rity rates. average ADF value for the remaining First-harvest yields were greater four entries and 18% lower (P<0.05) than subsequent harvests for all in Yr 2 (29.5%). Lignin levels of Yr 1 entries except the sorghum-sudan in CA737 grain sorghum (2.95%) and Yr 2 (Table 2). Sorghum-sudan yields Nutrifeed (2.85%) were lower than were equal to or greater than (P<0.05) that of the other three entries. the other entries, averaging 16.5 t Nutrifeed had the lowest lignin DM ha-1 for Yr 1 and 16.6 DM ha-1 concentration in Yr 2 (3.68%). for Yr 2, although it required three Moisture stress may have increased harvests. The forage sorghum yields the fiber concentrations in Yr 2 since were 48% higher (P<0.05) in Yr 1 the overall average ADF that yr was (16.8 t DM ha-1) than in Yr 2 (8.7 t 11% higher, and lignin was 23% DM ha-1), indicating that this species higher than in Yr 1. The increase in may require more soil moisture than harvest intervals the second year also the other entries. In contrast, millet may have contributed to higher fiber appeared to require less moisture, content in Nutrifeed pennisetum.
cumulative effect on subplot soil characteristics.
Results and Discussion
Summer Annual Grasses as Alternative Silage Crops
TABLE 4. Fiber components and in sacco DM disappearance for summer silage grasses grown in central Texasa. Item
Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD
NDF
Lignin
ISDb
29.3e 32.5d 35.0c 32.5d 26.8f 0.001 0.60
3.58d 4.50c 4.40c 2.75e 2.95e 0.001 0.140
75.6d 71.6e 64.3f 79.5c 78.8c 0.001 1.21
33.3f 35.2e 38.8c 37.1d 29.5g 0.001 0.38
4.14ef 4.81d 5.66c 3.68f 4.20e 0.001 0.18
77.6c 73.4d 65.4e 77.6c 76.4c 0.001 0.55
ADF (% DM)
53.8e 56.7d 62.9c 63.1c 51.0f 0.001 0.83
aAveraged
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. bISD = in sacco DM disappearance. c,d,e,f,gMeans in the same column from the same year with different superscripts are significantly different (P<0.05) according to Duncan’s multiple range test.
TABLE 5. Crude protein and P concentration and P removal by summer silage grasses grown in central Texasa.
Item Yr 1 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD Yr 2 SS20 forage sorghum SS10 sorghum-sudan SM60 pearl millet Nutrifeed pennisetum CA 737 grain sorghum P SD aAveraged
P removed (kg ha-1)
CP (% DM)
P (% DM)
5.2d 7.6c 6.9c 9.9b 9.0b 0.001 0.67
0.107d 0.143c 0.214b 0.211b 0.193b 0.001 0.0122
17.9c 23.6bc 25.9b 24.6bc 21.1bc 0.05 1.93
0.155d 0.175cd 0.258b 0.228bc 0.199bcd 0.001 0.0147
13.4c 29.1bc 36.2b 27.4bc 16.8c 0.001 3.63
6.5 6.8 7.3 7.1 7.7 >0.10 0.41
for plots with and without compost; compost x entry interaction was nonsignificant (P>0.10) for both years. All values are expressed on a DM basis. b,c,dMeans from the same year and in the same column followed by similar letters differ (P<0.05) according to Duncan’s multiple range test.
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The low NDF values during Yr 1 and high ISD rates for Yr 1 and Yr 2 in the grain sorghum and the forage sorghum indicate that these would be the forages of choice where high digestibility is desired (Table 4). In sacco disappearance rates were high for the pennisetum hybrid as well. Crude protein concentration was greatest in the pennisetum hybrid and CA 737 grain sorghum in Yr 1 (Table 5), but was undifferentiated among entries in Yr 2. Lower soil moisture during Yr 2 (66% of Yr 1 rainfall) may have stressed plants and lowered CP concentration. The SS20 forage sorghum CP was the lowest of all the entries, averaging 5.85% over both years. It is possible that more N fertilizer needed to be applied to the higher yielding entries in order to raise CP concentration in these. Compost application did not affect CP concentration in the herbage either year, perhaps because of a dilution factor as a result of higher yields. The application of composted manure increased herbage P concentration both years (P<0.05 Yr 1 and 2; Table 3). Averaged over all entries, P concentration was 0.159% in Yr 1 and 0.175% in Yr 2 when no compost was applied; concentrations rose to 0.189% (19% higher) in Yr 1 and 0.231 (32% higher) in Yr 2 in herbage from subplots where compost was applied. There were differences among entries as well, with the forage millet, pennisetum hybrid, and grain sorghum having as high or higher concentrations of P than the forage sorghum and sorghum-sudan both years (Table 5). When DM yield was multiplied by concentration, the forages from subplots with manure compost yielded 34 and 48% more P in Yr 1 and Yr 2, respectively, than from plots without manure (Table 5). Soil P in subplots with manure averaged 26.7 ppm after the second season. This was 2.4 times greater (P=0.001) than the water-soluble P available in subplots without manure. Soil P was not affected by forage species despite the differences in P uptake among plants (Table 5).
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When both yield and quality indicators are considered, forage sorghum had the most potential. However, in situations where cropping systems preclude autumn harvests to allow for earlier smallgrain planting, yields may be considerably lower. Where early secondharvest dates are desired, grain sorghum varieties may be more attractive. Crops such as forage sorghum and pearl millet, with proportionally heavier first harvests, would fit into single-harvest schemes. The application of composted manure had a positive effect on both forage yield and crop P concentration. Pearl millet was able to remove 46% of the P applied in the compost. However, the addition of compost resulted in a net increase of 16 ppm P to the soil by the second year. Because soil analysis indicates only what P will be available to the crop over the season (not total soil P), enhanced crop P uptake does not necessarily result in a P decrease in subsequent soil analysis.
Implications There is a trade-off in annual forage grasses between biomass production and forage quality. This is expected as taller, thicker stalks need stronger structural support. Ruminal disappearance of DM indicated that higher fiber contents resulted in lower rates of disappearance. Within cropping schemes including autumn small-grain planting, faster maturing, higher quality grain sorghum, or photoperiod-sensitive Nutrifeed
Muir et al.
pennisetum might have more application, despite lower production yields. Forage P concentrations were higher in the less productive grasses, indicating that P availability in the soil may have limited P uptake by the more productive plants. Efficiency of soil P extraction capacity has a potentially significant application in the selection of grass forages used in phytoremediation of high P soils or for improving the efficiency of P cycling in confined animal feeding operations with access to forage fields.
6. Hons, F. M., L. A. Larson-vollmer, and M.A. Locke. 1990. NH4Oac-EDTA-extractable phosphorus as a soil test procedure. Soil Sci. 149:249. 7. Jones, R. M., and J. C. Read. 1988. Effect of irrigation, nitrogen, and plant population on corn and sorghum grown for silage. Forage Research in Texas. Texas Agric. Exp. Stn. publication CPR 4593, College Station. 8. Jones, R. M., and M. A. Sanderson. 1996. Mineral composition and pH of dairy waste. Forage Research in Texas. C.P.R. 5258, TAEX, College Station, TX. 9. McCormick, M. E., D. R. Morris, B. A. Acherson and D. C. Blouin. 1995. Ratoon cropping forage sorghum for silage: yield, fermentation, and nutrition. Agron. J. 87:952. 10. MSTAT-C. 1993. User’s Guide to MSTATC. Michigan State University, East Lansing, MI.
Literature Cited 1. Auvermann, B. A. 1999. Manure and wastewater production and characteristics. In: Dairy Outreach Program Area Training Manual. S. R. Stokes (ed.). Texas Agricultural Extension Service, Stephenville, TX. 2. Dou, Z. J. D. Toth, R. Allshouse, C. F. Ramberg, and J. D. Ferguson. 2000. Phosphorus fraction distribution in animal waste. In Proc. 8th Int. Symp. Animal Agric. Food Processing Wastes. J. A. Moore (ed.). A.S.A.E., St. Joseph, MI, Oct. 9–11 Des Moines, IA. 3. Boddorff, D., and W. R. Ocumpaugh. 1985. Forage quality of pearl millet x napiergrass hybrids and dwarf napiergrass. Proc. Soil Crop Sci. Soc. Florida 45:170. 4. Gallaher, R. N., C. O. Weldon, and J. G. Futral. 1975. An aluminum block digester for plant and soil analysis. Soil Sci. Soc. Am. Proc. 39:803. 5. Hambleton, L. G. 1977. Semiautomated method for simultaneous determination of phosphorus, calcium, and crude protein in animal feeds. A.O.A.C. 60:845.
11. Muldoon, D. K., and C. J. Pearson. 1979. The hybrid between Pennisetum americanum and Pennisetum purpureum. Herbage Abstr. 49:189. 12. Piersynski, G. M., and T. L. Logan. 1993. Crop, soil, and management effects on phosphorus soils test levels. J. Prod. Agric. 6:513. 13. Rynk, R. 1994. Status of dairy manure composting in North America. Compost Sci. & Utilization Winter:20. 14. Sanderson, M. A., F. R. Miller, and R. M. Jones. 1995. Forage quality and agronomic traits of sorghum-sudangrass hybrids. Texas Agric. Exp. Stn. publication MP-1765, College Station. 15. Skerman, P. J., and R. Riveros. 1990. Tropical Grasses. FAO, Rome. p 695. 16. Van Soest, P. J., and J. B. Robertson. 1980. Systems of analysis for evaluating fibrous feeds. p. 49. In Standardization of Analytical Methodology for Feeds: Proc. Int. Workshop, Ottawa, ON. Mar. 12-14 1979. W. J. Pigden et al. (ed.) Rep. IDRC-134e. Int. Dev. Res. Ctr., Ottawa, ON, Canada, and Unipub, New York.