Pasture Management by the Seasons

the spring 2 to 3 weeks so as long as you have enough paddocks in the rotation you shouldnt need to confine horses to stress lot unless it is raining and soggy.
Summer
Any time that grasses are green and growing is a good time to evaluate your pastures. Take a walk through each one and note the proportions of bare ground weed cover and desirable cover. A quick and easy method for this is the Equine Pasture Evaluation Disc. This can help you make decisions about renovation and reseeding.
Cool season grass orchardgrass Kentucky bluegrass timothy tall fescue brome etc. growth slows significantly when it gets hot and dry. If grazing rotationally you may need to confine horses to a stress lotdry lot while you wait for a paddock to recover to 810 inches. Make sure to feed hay since theyre not consuming pasture forage.
If its a mild summer and theres plenty of moisture you can make another nitrogen application for increased summer growth. Around June you can apply another 2030 lbs of N if there is adequate rainfall and forage. Lime P and K can also be applied in the summer if they were not applied in the spring.

Identify weeds of concern and make a pasture weed inventory. By the time weeds are large and mature in the summer you cant do much other than mow them and prevent them from spreading seeds. However once you identify them and their life cycles you can look up the most effective herbicide and the most effective time to control them next year. Remember that weed control is an ongoing process and often requires pasture improvement so a single treatment is unlikely to solve all your problems.

If you plan on hiring someone to do pasture work in the fall get in touch with them
early. Fall is a very busy season for custom applicators. Find out if your laneways and pasture gates are wide enough for the equipment to get through and turn around.