sealPurdue News

September 13, 2002

Soybeans need rain, may have to harvest as a forage

WEST LAFAYETTE, Ind. – As the old saying goes, "rain makes grain," but since some farmers haven't seen much moisture this summer, it has them wondering what to do with the soybean crop.

"In southern Indiana, there is a strip of land about two counties wide that lies parallel to the Ohio River and borders the Ohio state line where beans have been under extreme stress for the last two months," said Ellsworth Christmas, Purdue University Extension soybean specialist. "Many of these beans have fewer than 10 pods per plant when they should have at least 35 per plant. If we don't get rain shortly, many of these pods will abort the beans and will have very low yields."

Rain is a necessity across all of Indiana to help the soybean crop into harvest. Christmas said rain in the southern one-third of the state will prevent the abortion of pods and seed.

In most of Indiana, flowering is over, and rain at this point will only help stabilize the crop and prevent it from further deterioration. In order to salvage what crop there is, Christmas said the soybeans need an inch and a half of rain through the next three to four weeks to carry them to maturity.

The soybean plant can respond to rain as long as the leaves are green. However, a number of fields of group II and early group III soybeans are beginning to show some leaf yellowing, indicating they have reached maturity. Rain will not benefit these fields.

"Yield is made up of basically three components: plants per acre, seed per plant and weight of the seed," Christmas said. "Rain will stabilize seed count and will give a normal seed size. Lack of rain will probably cause the plant to abort seed and/or pods, which reduces the seed count as well as seed size."

Most farmers will have to accept lower yields this fall; however, some livestock farmers may have the option to harvest their soybean crop early as a forage, said Keith Johnson, Purdue Extension forage specialist.

Farmers need to look at the potential grain yield and market value of the soybean crop and determine whether it has more worth as a grain than as a forage. If it does, then the money earned as a grain could be used to purchase hay, he said. Johnson cautions farmers because it will not be an easy task finding abundant hay supplies in the region this year.

Johnson and Christmas also said farmers should not consider harvesting soybeans for forage until flowering is over.

Farmers need to look at the crop's maturity stage and realize that soybeans as a forage maintain quality fairly well compared to most forages as they mature. The amount of energy, or total digestible nutrients, does not decline as quickly in soybeans versus commonly used perennial grasses and legumes, Johnson said. Soybeans should be harvested as a forage before leaves begin to yellow.

"As the crop dries, the leaves are going to dry quicker than the stem and excessive shattering can occur during baling," Johnson said. "Some of the quality also will be lost because of not getting soybean grain into the baler. Because of these issues, it may be an easier option to cut the crop for silage rather than hay."

Also before harvesting soybeans for forage, farmers should review what herbicides were applied to the crop and when they were applied. Some herbicides may have forage harvest restrictions.

Sandy Weaver, Farm Service Agency Tippecanoe County executive director, said farmers should notify their FSA agent if they chose to harvest soybeans for forage. Farmers also will need to have their soybean acreage appraised if they have crop insurance.

For more information about herbicide restrictions. For more information on harvesting soybeans as a forage, see the Purdue Extension publication CL-15, "Considerations when using soybeans as a forage," on the Internet.

Writer: Jennifer Doup, (765) 494-8406,

Sources: Ellsworth Christmas, (765) 494-6373,

Keith Johnson, (765) 494-4800,

Sandy Weaver, (765) 448-1805,

Related Web site:

Purdue Extension Harvest Update Web site

Purdue News Service: (765) 494-2096;

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