(Adds full-year forecast cuts, CEO quote, background, byline)
Aug 2 (Reuters) - Bunge Ltd, the U.S. agricultural commodities trader, reported a 34 percent drop in quarterly profit on Wednesday as slow farmer selling in South America hurt margins in its mainstay agribusiness, but forecast a better second half of 2017.
The latest results matched Wall Street's lowered estimates after the company warned of a shortfall last month.
Despite the rosier forecast for the rest of the year, Bunge lowered the full-year earnings estimate for its agribusiness and food and ingredients units for a second straight quarter.
"We are optimistic about a much better second half of the year, but some market headwinds will persist," said Chief Executive Officer Soren Schroder.
Bunge and rivals Archer Daniels Midland Co, Cargill Inc and Louis Dreyfus Co, known as the ABCD quartet of grain trading giants, have been stung by the global grains glut following four years of bumper harvests around the world.
On Tuesday, rival Archer Daniels said slow farmer sales in South America dragged down profits for its soybean processing business.
Bunge, which was targeted for a possible takeover by commodities trader Glencore Plc in May following a weak first quarter, unveiled a cost-cutting and restructuring plan last month that is says will slash costs by $250 million by the end of 2019.
Some analysts expect Bunge's second consecutive weak quarter to invite another approach by Glencore while others believe the overhaul could buy time to deliver on promised growth.
The second quarter was marked by slow farmer selling in South America and a difficult export market as ample global crop supplies and hand-to-mouth buying by importers limited trading opportunities.
The company sold 36.2 million metric tons of grains and other commodities in its agribusiness in the second quarter, but gross profit from the business fell more than half to $157 million.
On Wednesday, the company slashed its full-year agribusiness earnings target to $550 to $650 million, from $800 to $925 million in the first quarter, and its food and ingredients target to $210 million to $230 million, from $245 to $265 million.
Net income available to shareholders fell to $72 million, or 51 cents per share, in the quarter, from $109 million, or 78 cents per share, a year earlier.
Excluding one-time items, the company earned 17 cents per share, matching the average analyst expectation, according to Thomson Reuters I/B/E/S.
Net sales rose 10.5 percent to $11.65 billion.
Bunge shares closed down 0.4 percent on Tuesday at $78.06. (Reporting by Karl Plume in Chicago; Additional reporting by Ahmed Farhatha in Bengaluru; Editing by Sai Sachin Ravikumar and Jeffrey Benkoe)