Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2001
Publication Date: N/A
Citation: Interpretive Summary: For economic and efficient production of meat and dairy products producers need an inexpensive, readily available on farm source of high protein forage. Legume crops such as alfalfa have traditionally been used to provide this high protein forage. Soybeans are less expensive to establish and do not require insecticide to prevent damage from annual infestations of the potato leafhopper. In addition, soybean is a spring-seeded annual that can provide high protein forage when winter killing depletes alfalfa stands. The U.S. Department of Agriculture recently released three soybean cultivars bred for use as forage: Derry, Donegal, and Tyrone. The forage soybeans produced higher yields of forage when grown in rows that are 10 inches apart versus rows that are 30 inches apart. Yields were higher with later harvest versus early harvest. The ability of the new forage cultivars to produce high yields of high quality forage will enable dairy farmers and livestock producers to more efficiently provide products such as milk, cheese, meat, and wool for consumers at reasonable prices. The information in this report will provide guidance to research and extension scientists in making recommendations to farmers producing forage for livestock enterprises.
Technical Abstract: Soybean [Glycine max (L.) Merrill] has been used almost exclusively as a grain crop since the 1940's, but its potential as a high-protein annual forage crop is beginning to receive renewed attention from plant breeders. Tall forage-type soybean cultivars in maturity group V and VI have released. Our objective was to provide information for Upper Midwest conditions on yield and forage quality of these tall soybean cultivars as affected by harvest date and row spacing. We grew tall, grain, and a 1940's-era hay soybeans at two locations with harvests in early and late September. Average maturities of tall, grain, and hay soybeans were R3 (early harvest) to R4 or R5 (late harvest), R6 (early harvest) to R7 (late harvest), and R7 at both harvests, respectively. Consequently, forage of tall soybeans was mostly leaves and stems at both harvests, whereas, grain soybeans contained an average of 455 g kg-1 and 1190 kg ha-1 pods at the early and late harvests, respectively. There was no harvest date by soybean entry interaction for forage yield. Tall, grain, and hay types had average forage yields of 8.9, 8.7, and 5.7 Mg ha-1, respectively. Because of differences in maturity and pod proportion in the forage, tall soybean had lower crude protein and higher fiber in the total forage than grain- or hay-types. Average forage CP for tall, grain, and hay types was 146 g kg-1, 232 g kg-1, and 225 g kg-1, respectively. Increasing row width from 0.25 m to 0.76 m decreased yield from 10.3 Mg ha-1 to 9.5 Mg ha-1. An adapted tall soybean that would reach the full seed formation (R6) by harvest could have superior yield and similar quality as an adapted grain-type soybean.