The invention provides methods for providing Bacillus spores for application to agricultural soil or plant material. The methods comprise suspending the Bacillus spores in a liquid consisting essentially of water and an organic acid, including acetic acid, wherein the acid lowers the pH so that the spores are inhibited from germination and growth; and so that growth of unwanted microorganisms in the suspension is prevented. Compositions formed according to the methods of the invention are also provided.