Farm equipment comes in various types to meet the needs of farms of all sizes. Tractors are the primary tool and can pull many attachments for different farming tasks. Combine harvesters accomplish harvesting, threshing, and winnowing crops like grains in a single pass. Plows are tractor attachments that cut furrows in the soil for loosening, turning, and clearing vegetation. Harrows are used after plowing to break up clumps and smooth the soil surface in preparation for planting. Fertilizer spreaders are used to evenly distribute seeds and fertilizers across fields.