HARARE (Reuters) - Zimbabwe's government halved its economic growth forecast to 1.5 percent this year from the 3.2 percent it had projected earlier, Finance Minister Patrick Chinamasa said in a half-year budget statement on Thursday. In the document presented to parliament, Chinamasa said the contributions from the mining, tourism, construction, manufacturing and finance sectors would be weighed down by poor output in agriculture due to drought. "Deceleration in overall economic growth signifies the contribution of agriculture, and the need for drought proofing the economy given adverse effects of climate changes," he said.