Due to the cool growing season, frost and late planting date of many fields, I have been receiving numerous requests for determining the value of immature corn. Unfortunately no standard method exists for determining value. Arriving at a fair and equitable price for corn silage is difficult due to the number of factors involved that are dynamic and biologically variable. Some factors include production costs, grain price, harvesting costs, costs of handling, hauling and storage, grain drying costs, fertility value of stover, and forage quality (especially starch content and neutral detergent fiber digestibility-NDFD). The amount of moisture has a major influence on its feed value and needs to be considered to accurately determine fair silage prices. Some growers will want to calculate the price based on corn grain yield (as the alternative harvestable crop) and some dairymen will want to calculate the price based on alternative forages (primarily alfalfa as the alternative forage source). In either case the final price is affected by supply and demand within a region. This year Wisconsin has high demand.

Typical calculation methods for pricing normal corn silage include:

Relative feed value of a known forage market.
Silage ($/T) = 1/4 to 1/2 value of hay
Silage ($/T) = 6 to 8 times the price of a bushel of corn. If already harvested, then 10 times.
Feed replacement or substitution costs
Use market prices for energy, protein, and digestibility (NE_L of corn, soybean meal, hay)
Contracted price above the cost of production (280-320 $/A).

For most crops, forage quality and value is high prior to flowering and decreases with maturity, that is fiber levels increase and digestible energy decreases. Corn is somewhat unique in that forage quality increases with maturity. Digestible energy of corn silage is found in both stover (NDFD) and grain (starch). Immature corn will have a lower proportion of grain in the silage. Two approaches to consider for calculating the value of immature corn silage are:

Reduce the value of immature corn silage by the cost of buying back grain to bring the grain:stover ratio to a more normal proportion.
Use MILK2000 to calculate milk per ton potential from immature corn silage.

Tables 1 and 2 describe Milk per ton and Milk per acre changes of corn hybrids harvested at different stages of development. Original values were calculated from a closed NIR equation developed using wet chemistry (Darby and Lauer, 2002). NIR scans were kept and values recalculated using a global calibration equation (02HBW) in 2003. Negative starch content values early in development were assumed to be 0%. Milk per acre and milk per ton were calculated using the Milk2000 spreadsheet. For overall means of this data set, see Wisconsin Crop Manager July 1, 2004 11(17):109-111.

For all hybrids, Milk per acre increased to a maximum sometime during the dent stage (R5) (Ritchie et al., 1993). But, for the purposes of determining corn silage value, overall quality of corn silage is best expressed using Milk per ton. Greatest Milk per ton was usually measured during the dent stage (R5) of corn development. Average maximums across all hybrids equaled 3334 lb milk per ton. High Milk per ton was also measured prior to silking (V14 to V18) and averaged 2970 lb milk per ton. Corn silage at its lowest Milk per ton value occurred around the Milk stage (R3) and minimums for all hybrids averaged 2529 lb milk per ton. Thus, using Milk per ton as a measure of value, corn silage harvested prior to silking would be 89% of the level observed during the dent stage. Corn silage harvested at R3 would be 75% of the level observed during the dent stage.

Table 1. Corn silage yield and quality response to harvest date at Arlington during 1998.
Harvest date	Growth stage	Kernel milk	Forage yield	Forage moisture	Crude protein	ADF	NDF	IVD	NDFD	Starch	Milk per Acre	Milk per Ton
		%	T/A	%	%	%	%	%	%	%	lb/A	lb/T	%
Dairyland Stealth 1400 (100 d RM)
July 14	V14	--	3.1	86.8	14.0	36.0	66.3	73.7	60.3	0.0	8792	2877	94
July 24	R1.0	--	4.5	83.7	11.2	37.2	66.3	73.5	59.9	0.0	11984	2691	88
August 3	R1.3	--	5.1	80.9	10.3	33.8	61.6	74.1	58.0	0.0	11830	2326	76
August 12	R3.1	--	6.5	79.4	8.8	34.0	61.2	74.2	57.9	1.6	15056	2325	76
August 22	R3.7	--	9.0	73.5	8.8	29.0	54.3	77.8	59.1	15.0	27534	3059	100
September 1	R5.0	76	7.6	71.0	7.4	28.2	50.9	77.0	54.9	19.0	22314	2922	96
September 11	R5.0	63	10.8	61.3	7.4	23.1	44.0	78.9	52.0	25.4	31969	2961	97
September 21	R5.0	14	10.7	54.7	6.7	25.0	46.5	76.3	49.3	26.2	30233	2822	92
Dekalb DK591 (110 d RM)
July 14	V14	--	3.0	88.3	13.8	36.6	66.9	73.8	60.8	0.0	8797	2895	86
July 24	V18	--	4.5	84.8	10.8	38.7	68.5	72.8	60.3	0.0	12637	2783	83
August 3	R1.3	--	5.8	82.7	8.7	37.7	65.6	71.5	56.8	0.0	13507	2328	69
August 12	R3.0	--	6.9	80.9	8.5	35.3	63.5	74.4	59.7	0.0	16331	2376	71
August 22	R3.6	--	8.2	77.2	8.8	33.2	58.5	75.0	57.4	8.1	21764	2657	79
September 1	R4.8	100	11.0	70.9	8.1	26.4	48.7	78.9	56.7	21.4	34512	3127	93
September 11	R5.0	51	9.8	62.1	7.5	21.8	42.1	81.3	55.5	30.0	32929	3368	100
September 21	R5.0	20	11.1	61.9	7.3	28.1	50.5	75.5	51.7	23.1	33025	2966	88
Golden Harvest H2387 (100 d RM)
July 14	V14	--	3.4	88.6	13.2	37.6	68.4	71.4	58.2	0.0	9140	2707	82
July 24	R1.0	--	4.1	84.7	10.3	38.0	67.9	71.6	58.3	0.0	10713	2612	77
August 3	R1.8	--	5.6	81.5	10.0	34.7	62.8	72.5	56.3	0.0	12643	2268	67
August 12	R3.5	--	6.2	79.4	9.7	31.4	57.9	76.1	58.8	4.3	15273	2477	73
August 22	R3.9	--	7.3	77.2	8.7	32.0	57.2	74.3	55.7	10.5	19510	2675	79
September 1	R5.0	75	10.6	66.4	7.9	22.1	43.0	81.8	57.7	28.2	36205	3402	100
September 11	R5.0	35	9.3	62.3	7.1	23.6	45.3	78.3	52.2	27.3	29282	3147	93
September 21	R5.5	4	10.1	52.3	6.8	24.3	46.6	77.1	51.0	29.5	28931	2870	84
Golden Harvest H2497 (110 d RM)
July 14	V14	--	3.1	88.3	13.3	37.1	67.2	72.4	59.0	0.0	8733	2784	95
July 24	R1.0	--	4.5	84.8	10.3	39.0	68.3	71.8	58.7	0.0	11964	2647	90
August 3	R1.0	--	5.4	81.6	8.3	37.7	65.5	70.2	54.5	0.0	11757	2166	74
August 12	R3.0	--	6.8	80.2	8.6	34.1	61.4	73.0	56.0	0.3	14579	2131	73
August 22	R3.6	--	8.4	75.2	8.0	31.4	56.2	75.5	56.4	10.0	21835	2594	89
September 1	R4.9	86	9.3	70.7	7.3	27.4	49.7	77.2	54.3	19.6	26748	2880	98
September 11	R5.0	69	12.1	60.8	7.4	22.2	43.0	78.9	50.8	26.3	35289	2927	100
September 21	R5.0	33	10.7	62.5	7.0	24.9	45.5	76.3	47.9	25.1	30058	2816	96
V stages = number of leaf collars; R1 = Silking; R2 = Blister; R3 = Milk; R4 = Dough; R5 = Dent; R6 = Black layer

Table 2. Corn silage yield and quality response to harvest date at Arlington during 1999.
Harvest date	Growth stage	Kernel milk	Forage yield	Forage moisture	Crude protein	ADF	NDF	IVD	NDFD	Starch	Milk per Acre	Milk per Ton
		%	T/A	%	%	%	%	%	%	%	lb/A	lb/T	%
Dekalb DK591 (110 d RM)
July 12	V15	--	3.7	86.6	13.7	34.0	62.3	81.2	69.8	0.0	11917	3199	96
July 19	V18	--	4.2	86.2	12.1	38.1	67.8	76.9	65.9	0.0	13281	3153	94
July 28	R2.0	--	5.7	83.7	9.2	36.2	64.2	77.9	65.6	0.2	15837	2782	83
August 6	R3.0	--	8.3	80.1	8.5	34.6	60.9	78.7	65.0	4.1	23402	2832	85
August 15	R4.3	--	9.0	76.4	8.9	29.9	53.3	80.8	64.0	16.2	30044	3323	99
August 25	R4.6	100	10.0	75.2	8.0	28.9	53.3	79.3	61.1	23.4	33139	3325	99
September 3	R5.0	70	12.1	64.7	7.0	26.8	50.2	79.4	58.8	25.5	40094	3314	99
September 13	R5.0	39	12.6	59.8	7.1	23.1	45.3	80.8	57.8	31.6	41987	3342	100
Golden Harvest H2387 (100 d RM)
July 12	V18	--	3.4	86.6	12.8	35.5	64.4	78.6	66.9	0.0	10643	3094	85
July 19	R1.0	--	3.9	85.4	12.1	36.7	66.2	76.5	64.5	0.0	11787	2999	83
July 28	R2.3	--	5.9	82.5	9.9	33.0	60.5	79.8	66.6	1.7	16545	2817	78
August 6	R3.6	--	7.9	78.9	8.3	29.8	54.8	82.0	67.2	11.9	25142	3196	88
August 15	R4.8	--	8.8	74.4	8.1	25.6	47.8	83.1	64.7	24.9	31797	3621	100
August 25	R5.0	79	9.4	72.2	7.8	25.3	48.8	80.9	60.9	29.8	32322	3444	95
September 3	R5.0	55	11.8	60.9	7.7	24.5	48.8	81.5	62.3	28.8	40683	3455	95
September 13	R5.0	4	11.0	51.8	6.7	23.3	46.9	79.9	57.2	34.2	34130	3094	85
Golden Harvest H2497 (110 d RM)
July 12	V15	--	3.6	86.7	13.0	33.3	61.5	81.4	69.8	0.0	11261	3115	93
July 19	R1.0	--	4.1	86.6	11.5	38.3	68.1	75.8	64.4	0.0	12485	3043	90
July 28	R2.1	--	5.7	83.8	9.8	35.5	63.8	77.1	64.1	1.0	15785	2779	83
August 6	R2.9	--	7.1	80.6	8.3	34.0	60.4	76.8	61.6	4.5	18911	2654	79
August 15	R4.1	--	8.4	76.5	8.6	29.1	52.3	79.9	61.5	18.2	27694	3295	98
August 25	R4.9	92	9.5	74.6	7.8	25.9	49.2	79.8	58.9	26.6	31808	3342	99
September 3	R5.0	61	11.6	65.4	7.2	26.2	50.2	80.1	60.1	26.6	39168	3367	100
September 13	R5.0	38	11.2	62.4	6.4	23.6	45.4	80.0	56.1	32.3	37274	3333	99
Pioneer 36H36 (100 d RM)
July 12	V18	--	3.6	84.9	12.7	34.0	61.3	81.4	69.6	0.0	11197	3072	86
July 19	R1.0	--	4.2	84.9	11.2	36.6	65.6	78.8	67.7	0.0	13009	3090	86
July 28	R2.8	--	6.2	81.4	8.9	34.1	61.3	80.6	68.4	2.3	17997	2923	82
August 6	R3.9	--	7.7	77.2	8.4	30.7	55.0	81.8	66.9	13.0	25108	3282	92
August 15	R5.0	--	9.1	73.4	8.0	27.3	49.7	82.6	65.0	23.7	32480	3585	100
August 25	R5.0	75	9.7	71.2	8.0	25.0	48.1	81.7	61.9	28.9	33874	3502	98
September 3	R5.0	50	10.1	64.3	6.9	26.4	50.6	80.0	60.4	25.9	34210	3374	94
September 13	R5.0	10	10.0	58.7	7.1	22.2	44.9	81.4	58.6	33.7	33696	3360	94
V stages = number of leaf collars; R1 = Silking; R2 = Blister; R3 = Milk; R4 = Dough; R5 = Dent; R6 = Black layer

Literature Cited

Darby, H. M. and J. G. Lauer. 2002. Harvest date and hybrid influence on corn forage yield, quality and preservation. Agron. J. 94:559-566.

Ritchie, S. W., J. J. Hanway, and G. O. Benson. 1993. How a corn plant develops. Iowa State University CES Special Report No. 48. 21 pp.