More and more acres of corn grown for silage are being harvested using custom harvest operators. Some custom operators are harvesting large acreages (>20,000 acres). In order to harvest all of the acres, often operators have to start earlier and finish later. Some operators are encouraging growers to start anytime after the "milk" stage.

How significant are corn silage yield and quality changes during the fall? Corn is somewhat unique as a forage. Like alfalfa corn silage quality is very high just prior to flowering (silking) and then decreases as the plant develops through silking, blister and milk growth stages. Unlike alfalfa, quality then begins to increase as development continues and grain filling progresses. In fact, corn silage quality is better near maturity than at flowering.

Milk per acre accounts for changes in fiber, digestibility and yield of a forage. Tables 1 and 2 show the relative yield (Milk per acre) changes of corn at various corn development stages for two recent studies conducted in Wisconsin. Optimum yield and quality is achieved between the stages of 50 and 25% kernel milk (R5.5 to R5.8). At the Milk stage (R3) relative milk per acre yield was lowest. Depending on the study, milk per acre increased to between 35 and 65 % of the maximum at the Dough stage (R4). As the season progressed, relative yield further increased to between 71 and 81% of the maximum at the R5 Dent stage.

These data suggest that an optimum harvest period exists for maximizing milk per acre yield. Harvest should not begin until after the dent stage and preferably around 50% kernel milk. Harvesting prior to the dent stage will significantly reduce milk yield per acre. Farmers must also consider harvesting at the proper moisture for the storage structure to insure proper fermentation and storage.

Table 1. Relative milk per acre yield changes during development for corn during 1988, 1989 and 1990 at Marshfield, WI.
Corn stage	Relative yield (Milk per acre)
	% of maximum
R4 Dough	65
R5 Dent	81
R5.5 (50% kernel milk)	100
R5.75 (25% kernel milk)	95
R6 Black layer	93

Table 2. Relative milk per acre yield changes during development for corn during 1993 at Arlington, WI. Corn was planted May 11.
Calendar date	Corn stage	Relative yield (Milk per acre)
		% of maximum
July 11	V11	10
July 21	V14	20
July 31	R1 Silking	27
August 10	R2 Blister	30
August 20	R3 Milk	20
August 30	R4 Dough	35
September 10	R5 Dent	71
September 21	R5.5 (50% kernel milk)	87
October 5	R5.8 (20% kernel milk)	100