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Establishing a correct yield goal is the first step for developing a sound fertilizer recommendation. Producers typically measure and record grain yields in detail. Yields of hay, silage, and pasture often are not recorded with the same detail, so yield goals are often more difficult to set for these harvest systems. This Crop File contains suggestions for setting proper yield goals in these situations.
Potential silage yields can be estimated from grain yield history. One ton of corn silage (at 65% moisture) typically contains about 7 to 8 bushels of grain, but this differs between hybrids. Dividing the grain yield goal by 7.5 furnishes a reasonable estimate of silage yield goal (see Table 1), but may require individual adjustments for moisture or quality.
If corn is stressed, about one ton of silage will be harvested for each 5 bushels of grain yield. If the corn contains little or no grain, estimate about one ton of silage per foot of plant height including tassel.
Grain sorghum harvested as silage averages 50% to 60% grain content under normal conditions. Silage yields will range from one- half to two-thirds the silage yield of forage sorghum varieties, depending on conditions.
Yields of small grain hays and silages can also be estimated from the grain yield history. Each ton of small grain hay (at 15% moisture) typically contains about 13 to 15 bushels of grain. Each ton of small grain silage (at 60% moisture) contains about 6 to 7 bushels of grain. Table 2 provides a range of small grain hay and silage yield equivalents at different grain yield levels.
ServiTech fertilizer recommendations for grass and legume forages are based on hay production. If these forages are to be harvested by grazing, production goals expressed as "animal units" (AU) can be used to estimate the equivalent hay yield goal based on a particular stocking rate.
Animal units are a way of expressing the total forage demand in common units. This system assumes that one animal unit (1 AU) is a "standard animal". Animals of different type are then expressed as a fraction of the "standard animal". Table 3 compares AU equivalents
between different types of livestock. For example, one cow with a calf at side is assumed as one animal unit (1.0 AU). Five sheep (0.2 AU each) or two weaned 12-month-old calves (0.5 AU each) are expected to consume as much forage as the cow-calf pair.
One "animal unit month" or "AUM" is the amount of forage required to support one AU for 30 days - which is assumed to be 680 pounds of forage dry matter. One ton of hay (90% dry matter) is equivalent to 2.5 AUM's. In other words, one ton of hay (or the equivalent amount of fresh forage dry matter) would be expected to support one animal unit for a 2.5 month grazing period.
AUM values can also be used to convert from a hay yield to a stocking rate. For example, the amount of fertilizer recommended for a 2 ton per acre grass hay yield should produce enough forage to support either two cow/calf pairs or four yearling calves per acre for a 2.5 month grazing period. This assumes the pasture or range is in good condition and that the producer uses proper grazing management. Table 4 provides a typical range of AUM's and equivalent hay tonnages for different crops.
¶ Table 1. Typical Corn Silage Yields at Different Grain Yield Levels |
||
|---|---|---|
| Grain Yield bu/ac |
Estimated Silage Yield ton/ac |
|
| 75 | 9 – 10 | |
| 100 | 13 – 14 | |
| 125 | 17 – 18 | |
| 150 | 20 – 21 | |
| 175 | 22 – 23 | |
| 200 | 25 – 27 | |
| 225 | 28 – 30 | |
| 250 | 31 – 33 | |
| 275 | 34 – 36 | |
¶ Table 2. Typical Small Grain Hay and Silage Yields at Different Grain Yield Levels |
||
|---|---|---|
| Grain Yield bu/ac |
Estimated Hay Yield ton/ac |
Estimated Silage Yield ton/ac |
| 20 | 1½ – 2½ | 4 – 4½ |
| 30 | 2½ – 3 | 4½ – 6 |
| 40 | 3 – 3½ | 7 – 8 |
| 50 | 3½ – 4 | 8½ – 9 |
| 60 | 4½ – 5 | 10 – 11 |
| 70 | 5 – 5½ | 11½ – 12 |
| 80 | 5½ – 6 | 13 – 13½ |
| 90 | 6 – 6½ | 14½ – 15 |
| 100 | 7 – 7½ | 16 – 16½ |
¶ Table 3. Animal Unit (AU) Equivalents to Calculate Grazing for Different Animal Types |
|
|---|---|
| Animal Type | Animal Units |
| CATTLE | |
| • Cow w/ calf at side | 1.00 |
| •. Cow, non-lactating | 0.90 |
| •. Replacement heifer, 24 - 36 months old | 1.00 |
| •. Steer, two years old | 0.90 |
| •. Yearling, 18-24 months | 0.80 |
| •. Yearling, 12-18 months | 0.70 |
| •. Calf, weaned, under 12 months old | 0.50 |
| •. Calf, not weaned, under 12 months old | 0.30 |
| •. Young bulls, 12 - 24 months old | 1.20 |
| •. Bulls, 24 - 60 months | 1.50 |
| HORSES | |
| • Yearlings | 0.75 |
| • Two-year old horses | 1.00 |
| • Mature light horses | 1.25 |
| SHEEP and GOATS | |
| • Sheep (mature) | 0.20 |
| • Lamb (weaned to yearling) | 0.12 |
| • Yearling lamb | 0.15 |
| • Ram | 0.25 |
| • Goat, mature | 0.15 |
| • Yearling goat | 0.10 |
¶ Table 4. Typical Range of Seasonal AUM's and Equivalent Hay Tonnage Per Acre |
||
|---|---|---|
| Forage Type | AUM Range per Acre | Equivalent Hay Yield ton/ac |
| Bermudagrass | ||
| Non-Irrigated | 2 – 10 | 1 – 4 |
| Irrigated | 10 – 16 | 4 – 7 |
| Bromegrass | ||
| Non-Irrigated | 2 – 8 | 1 – 3 |
| Irrigated | 10 – 13 | 4 – 5 |
| Bluestem | ||
| Non-Irrigated | 2 – 6 | 1 – 3 |
| Irrigated | 10 – 16 | 4 – 5 |
| Grass/Alfalfa | ||
| Non-Irrigated | 2 – 8 | 1 – 3 |
| Irrigated | 9 – 14 | 3 – 5 |
| Small grain, graze out | ||
| Non-Irrigated | 1 – 6 | 1 – 2 |
| Irrigated | 4 – 8 | 2 – 3 |
| Sudan and Sorghums | ||
| Non-Irrigated | 2 – 8 | 1 – 3 |
| Irrigated | 10 – 12 | 4 – 5 |
| Wheatgrass, intermediate | ||
| Non-Irrigated | 2 – 6 | 1 – 3 |
| Irrigated | 8 – 11 | 3 – 4 |
| Lovegrass | ||
| All | 5 – 10 | 2 – 4 |
Kansas State Univ. 1979. Sell your crop as hay, grain, silage, or graze out. MF-487. Dept of Economics, Coop Ext. Svc., KSU,
Waller, S., L. Moser, and B. Anderson. EC 86-113. A guide for planning and analyzing a year-round forage program. Univ. of Nebr. Coop. Ext. Svc., Lincoln, Nebr. 18 pg.
Manske, L. 1997. Animal unit equivalent for beef cattle based on metabolic weight. 1997 Res. Report. Dickinson Res. Ext. Center., North Dakota State Univ. http://www.ag.ndsu.nodak.edu/dickinso/research/1997/animal.htm accessed 11/10/2011.
Redfearn, D. and T. Bidwell. Stocking Rate: The key to successful livestock production. Pub. PSS-2871. Oklahoma Coop Ext. Svc., Stillwater, Okla. 8 pg.
Blonde, G. Buying and selling corn silage: What’s a fair price? Univ. of Wisconsin Ext., Waupaca County. http://www.uwex.edu/ces/crops/uwforage/BuyingSellingCS.pdf accessed 11/10/11