Old spears and ferns can be removed by hand or by gently tilling or mowing, using caution not to damage the crowns. Burning is another option if it is safe and legal to do so.
Asparagus spears emerge from early to mid-April in Manhattan but earlier in southern Kansas and later in northern Kansas.
Fertilize asparagus after the harvest, as needed, based upon a soil test. General recommendations are to apply 1 to 2 pounds of 10-20-10 or 11-15-11 fertilizer per 20 feet of row. If only nitrogen is needed, apply 1 pound of 16-0-0 or ½ pound of 30-4-5, 27-3-3 or similar fertilizer per 20 feet of row. Most of these high nitrogen fertilizers are lawn fertilizers but can be used for this crop as long as they don’t contain a weed preventer or killer. Water in the fertilizer application with ¼ inch of water.