Spring Tilling in Colorado: When to Incorporate Compost and How Much Organic Matter for Alkaline Clay

Colorado Springs (zone 6), 750 sq ft veg garden. Plans to rent rototiller March 11, add 1 yd homemade compost + 5 bags mushroom compost + 5 bags steer manure. Asks: (1) good time to till? (2) Is this amount/balance good for alkaline clay?

Timing

Till anytime soil isn't too wet—should crumble to pea-to-golf-ball size. March 11 is fine if soil condition allows.

Organic Matter Limit

Max 40% organic matter by volume. Your homemade compost is best (coarser, improves texture). Mushroom compost and manure are fine but not fertilizer substitutes.

Fertilizer and pH

You'll still need fertilizer. Target pH 6.5–7.0. Till again in fall; freezes improve texture. Consider a rape cover crop for green manure next spring.