Evaluating top losses in Argentine corn silages

Abstract Text:

The aim of the study was to quantify how much of the quantity and quality is being lost from the top of corn silages when compared with silo mass across Argentina. Fifty corn silages were sampled in Buenos Aires, Santa Fe and Entre Rios provinces. Composite samples (3 sub-samples each) were taken in each silo (from 44 to 488 days since the silages were done), from the core (CS: between 50 to 100 cm inside) or the top (TS: within 50cm), refrigerated until freezing and analyzed for pH, DM, OM and Ashes. Measures of packing density was done by sampling site plus particle size separation using the PSP and finally OM losses were calculated as the difference between % and tons found in the top compared with the core. Data were analyzed as RCB design, using each silo as Block (50), within each block the treatment was the sampling location (CS and TS) and ANOVA by variable was obtained using alpha 0.05. Of total sampled silages 33, 16 and 1 were storage in stack, bunker and pile silos, respectively; most covered using white and black (36) or black (7) standard plastic and 7 uncovered. No one used additives or special covering systems for the surface. Results are presented in next table.

Item	Top n=50	Core n=50	SE
DM, %	32.4	31.9	0.112
OM, as %DM	78.7b	93.2a	0.141
ASHES, as %DM	21.3a	6.8b	0.141
pH	5.44a	3.84b	0.002
PS, % >0.75 in	13.41	13.50	1.06
PS, % 0.31 to 0.75 in	70.26	69.41	1.07
PS, % 0.07 to 0.31 in	15.89	16.65	0.22
PS, % <0.07 in	0.43	0.44	0.003
Packing density, kgDM/m3	264.7b	294.2a	11.86

_{^ab Means within a row with unlike letters differ (P<0.01). PS = Particle size.}

From silos which originally had as a mean 8382 m³, exposed surface averaged 1398 m³which involved about 291 tons of OM within each silo. Of exposed OM, we estimated that 23.9% is being lost in the top, averaging 69 tons of OM in each of the sampled silages. When we tried to relate OM losses with days after ensiling or packing density, low relationships were detected; suggesting that practices around covering and uncovering were responsible of top losses.

Keywords: Corn silage, Top losses