HARTFORD, Conn. - Changes in the agriculture industry are part of the reason Allegis Realty Investors acquired Batterymarch: Agrivest last month.Along with the federal government's exit from the fa rm business, Agrivest appealed to Allegis because the firm makes private real estate investments, Allegis' focus; it had consistent performance; and it is negatively correlated with other Allegis offerings, said Allegis Chief Execu tive Officer James O'Keefe. The firm also was attractive because of the changing manner in which farmers will plant crops and a greater awareness of the investment sector by pension funds and their consultants."With the passage of the farm bill last year, we entered into a new era: the gradual departure of government from farm (planting) decisions," said James McCandless, Agrivest's chief investment officer. "Farming is moving toward a market-oriented app roach."Batterymarch: Agrivest, Glastonbury, Conn., an institutional investor in farmland, has $235 million under management and makes equity and debt investments. Its pension fund clients include the $36.2 billion State Teacher Re tirement System of Ohio, the $26 billion AT&T Co. pension fund and the $40 billion pension fund for Lucent Technologies Inc.The firm is the third largest pension fund farmland investor, behind Prudential Agriculture Investments, Pa rsippany, N.J., with $397 million under management and Cozad/Westchester, Champaign, Ill., with $279 million.Agrivest will operate independently under the Allegis umbrella. The 10-person management team will remain intact."Jim (Mc Candless) and his team will have equity in the business," said Mr. O'Keefe. "We think that is a key enfranchisement for a manager."Pension fund investment in agriculture land has increased to $875 million as of October 1996 from $30 million in 1989, said Mr. O'Keefe. The National Council of Real Estate Investment Fiduciaries began publishing an agriculture index in 1995.Agrivest operates 90 properties in 14 states. Those farms produce 25 different crops, including grapes, apples, citrus fruits and soybeans.The firm came on the market following Batterymarch founder Dean LeBaron's sale of his $6 billion institutional equity money management business in late 1994."We were next in lin e," said Mr. McCandless.