EFFECTS OF MOISTURE CONTENT ON CORN SILAGEDENSITY AND STORAGE LOSSES IN A LARGE TOWER SILO1

H.A. Jackson and J.R. Lessard

Engineering Research Service and Animal Research Institute, Agriculture Canada, Ottawa, Ontario K1A 0C6

Received 10 August 1976

Jackson, H.A. and J.R. Lessard. 1977. Effects of moisture content on corn silage density and storage losses in a large tower silo.Can. Agric. Eng. 19:57-58.

The capacity, average density, settlement and storage losses of corn silage stored at different moisture contents in a large towersilo were measured. The results are in close agreement with presently used estimates obtained by extrapolating results from smallsilos. The silo dry matter (DM) capacity was relatively constant, appearing to be independent of silage DM content. Averagesettled silage densities differed by less than 10% from comparable estimates in the Canadian Farm Building Code. The silage DMlosses suggest that in large tower silos, corn should be ensiled at a DM content of 35% to minimize DM losses.

INTRODUCTION

Tower silo capacity and silage densityinformation is available (American Societyof Agricultural Engineers) (ASAE) 1975;Standing Committee on Farm BuildingStandards (SCFBS) 1975). This informationwas collected from silos up to 12 m (40 ft) inheight (McCalmont 1963; Otis and Pomroy1957) and extrapolated for heights beyond12 m (40 ft). The size of most silos on farmstoday is in the range for which onlyextrapolated information is available.

Storage losses for corn silage have beenestimated (Watson and Nash 1960; Zelter1969; Zimmer 1971) but there is a scarcity ofrecent data on the relationship of moisturecontent of corn silage to dry matter (DM)losses in large tower silos.

PROCEDURE

A 9.1 X 24.4-m (30 X 80-ft) silo was usedto obtain measurements of silo capacity,silage density and storage losses as afunction of ensiling whole-plant corn atdifferent moisture contents. The silo was

filled with corn silage at average DMcontents of 28.3, 32.9 and 45.4% in 1971,1972 and 1973, respectively.

The crop was harvested and loaded by aself-propelled, two-row, corn harvester setfor 1.3 cm (0.5 inch) theoretical chop. Thematerial was weighed in self-unloading forage wagons and then blown into the silo.Samples of fresh forage were taken fromeach wagon load and oven-dried for 24 h at100 C for DM determination.

A silage distributor with a deflectingchute rotating at a constant speed distributed the silage symmetrically about thecenter of the silo. For the final 3 m (10 ft) avariable speed, spinning disk-type distributor was used. Silage depth was measuredeach morning at the start of the fillingoperation and at monthly intervals duringthe storage period. When filled, a plastic

'Contribution no. 467 from Engineering ResearchService and no. 645 from Animal Research

Institute.

TABLE! CORN SILAGE CAPACITY AND LOSS RESULTS IN A 9.1 X 24.4-M TOWER SILO

1971 1972 1973

Total stored (tonnes) 1,450 1,204 906

% DM stored 28.3 32.9 45.4

Total DM stored (tonnes) 410 396 411

Total fed (tonnes) 1,178 1,066 806

% DM fed 31.6 33.9 44.3

Total DM fed (tonnes) 372 361 357

% total loss 19 11.5 11.1

% DM loss 9.2 8.8 13.6

Harvest dates 21 Sept. - 4 Oct. 2 Oct. - 17 Oct. 21 Sept. - 9 Oct.

Feeding dates 24 Jan. - 8 June 20 Feb. - 16 July 30 Apr. -9 Oct.

Stage of maturity dent dent mature

Unsettled silage depth (m) 24.1 24 23.8

Settled silage depth (m) 20.7 21.5 22.2

Settlement (m) 3.4 2.5 1.6

% settlement 14.1 10.4 7.2

Avg unsettled density! (kg/m3) 916 764 580

Avg settled density (kg/m3)J 1,067 853 621

Avg settled density (SCFBS 1975)§ 1,005 880 647

t Based on total stored and unsettled silage depth.JBased on total stored and settled silage depth.§Based on settled silage depths from this study.

cover was placed over the top and weighedwith additional chopped forage.

During the feeding period, the silage wasloaded into feed trucks equipped with loadcells for weighing. Silage depth measurements and samples for DM determinationwere taken weekly. Silage DM was determined by toluene distillation (Dewar andMcDonald 1961), making a correction forvolatiles in the distillate.

RESULTS

The measured capacity and loss resultsfor the tower silo for the 3 yr are listed inTable 1.

During the first year, the total weight losswas rather high (19%) in comparison to DMloss (9.2%), due to a high initial moisturecontent (71.7%) resulting in a substantialamount of seepage. A steady stream of silagejuice poured out of the silo through theunloading hatches during filling and for aperiod afterwards. Seepage losses during thesecond year were small with only slightly

drier silage (67.1% moisture). In this casejust a trickle of juice came out through thehatches near the end of filling and for a shortperiod afterwards. No seepage was noticedthe third year. The DM loss (13.6%) for thethird year was greater than for the previous 2yr-

The total weight of silage stored eachyear varied substantially due to the differentmoisture contents, but there was very littledifference in the total weight of DM storedeach year.

Average silage unsettled and settleddensities are given in Table 1for the 3 yr. Theaverage unsettled density is the density at theend of the filling period based on the totalweight of silage stored and the unsettleddepth of silage. The average settled density isthe density at the beginning of the unloadingperiod based on the total weight of silagestored and the settled depth of silage. Alsoshown for comparison are average densitiesof settled silage from SCFBS (1975) basedon the settled silage depths from thisexperiment.

CANADIAN AGRICULTURAL ENGINEERING. VOL. 19 NO. 2, DECEMBER 1977 57

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Silage settlement for the 3 yr is shown inFig. 1. Most of the settlement occurredduring the first month after completion offilling. The magnitude of the settlement isrelated to DM content, varying from 14.1%at 28.3% DM to 7.2% at 45.4% DM.

DISCUSSION

Dry matter losses were representative ofconcrete tower silos (under 10%) in the first 2yr. A comparison of the results of those yearsindicates that the first year crop (71.7%moisture) did not suffer significantly higherDM losses than the second year even afterlosing about 8% of the ensiled weight asseepage. Highest DM losses were observedin the third year for the crop ensiled at anaverage of 54.6% moisture, probably theresult of oxidations due to insufficient

compaction.The DM capacity of the 9.1 X 24.4-m (30

X 80-ft) silo was approximately the same forthe 3 yr, appearing to be independent of themoisture content of the crop at ensiling time.This DM capacity averaged 406 tonnes (447tons) at 10.4% average settlement. UsingASAE (1975) data, the DM capacity ofa 9.1X 24.4-m (30 X 80-ft) silo with 70% moisturecontent silage is approximately 406 tonnes(447 tons) at 7.5% settlement — settleddepth 22.6 m (74 ft), average settled density913 kg/m^ (57 lb/ft*). Using SCFBS (1975)data, the silo capacity is approximately 421

58

40 60 80 100 120 140

TIME AFTER FILLING (DAYS)

Figure 1. Settlement of corn silage in a 9.1 X 24.4-m (30 X 80-ft) tower silo.

tonnes (464 tons) at 10% settlement —settled depth 21.9 m (72 ft), average settleddensity 974 kg/m* (60.8 lb/ft*). The ASAE(1975) and SCFBS (1975) DM capacitypredictions are, respectively, equal to and3.7% higher than the average of the resultsfrom this study.

The average settled densities from thisstudy are in close agreement with theestimated densities from SCFBS (1975) asshown in Table 1. In 1971, the SCFBS (1975)average settled density value was 6% lower,while in 1972 and 1973 these values were 3

and 4% higher, respectively. The high 1971average settled density value from this studyis;probably due to the heavy seepage losseswhich were not deducted from this densityvalue.

One main difference between the ensilingtechniques used in this experiment and thoseof most previous experiments was the use ofa silage distributor to help avoid the formation of the dense, irregular pillars reportedearlier (Otis and Pomroy 1957).

The present data suggest that corn shouldbe ensiled at a DM content of about 35% inorder to minimize DM losses. They alsoindicate that SCFBS (1975) estimates towithin 10% the apparent average settleddensities for corn silage in large concretetower silos.

ACKNOWLEDGMENTS

The technical assistance of Linda Neill and R.

Alary is gratefully acknowledged. The cooperation of the operational staff at the AnimalResearch Institute is appreciated.

AMERICAN SOCIETY OF AGRICULTURAL

ENGINEERS. 1975. Tower silos: unit weightof silage and silo capacities. Agriculturalengineers yearbook. ASAE Data: ASAED252, p. 492.

DEWAR, W.A. and P. McDONALD. 1961.Determination of dry matter in silage bydistillation in toluene. J. Sci. Food. Agric. 12:970.

McCALMONT, J.R. 1963. Farm silos. Misc.Publ. No. 810 (Rev.), Agric. Res. Serv., U.S.Dep. Agric, Washington, D.C.

OTIS, C.K. and J.H. POMROY. 1957.Density: atool in silo research. Agric. Eng. 38(12): 860-863.

STANDING COMMITTEE ON FARMBUILDING STANDARDS. 1975. Apparentdensity of settled silage in vertical silos.National Research Council of Canada. Canadian farm building code. NRCC Publ. No.13992, p. 136.

WATSON, S.J. and M.J. NASH. 1960. Theconservation of grass and forage crops. Oliverand Boyd, Edinburgh.

ZELTER, S.Z. 1969. Extent, nature, causes andnutritional significance of losses in forageduring harvesting and conservation especiallyby ensilage. Crop Conservation and Grassland. Proc. 3rd Meeting Eur. Grassl. Fed. pp.183-200.

ZIMMER, E. 1971. Factors affecting fermentation in silo. Technological papers presented atInternational Silage Research Conference,Washington, 1971. pp. 38-78.

CANADIAN AGRICULTURAL ENGINEERING, VOL. 19 NO. 2, DECEMBER 1977