For those of you out there managing pasture with K-line irrigation, wanted to share my experience with a DIY automatic timer setup, in case it's helpful.
We're on a shared pump (and gravity fed system), so we have to turn k-lines lines on and off at the riser when we want to start and stop the flow of water. For the last two seasons I've been using a Hunter Node timer (battery powered), which is about the size of a large coffee mug. You just cut the K-line near the riser, shove in barbed-to-threaded PVC fittings on either side of the cut (secured with hose clamps), thread on the valve (Hunter makes a durable one), attach the Node timer and its DC solenoid, and then secure the coffee-mug-sized timer to the valve with some duct tape. The timer (and tape!) come off for winter, but the valve stays in place in the K-line.
We're on our second season with the setup. After a second mow, when we're just using pasture for forage and keeping it greenish for fire risk reduction, it's simple to cut way down on water usage - a few hours overnight. It sure feels better to try to leave water in the river this time of year.
One limitation when you are on a shared pump with other families: if your pump is like ours, *someone* has to have a line open and running when yours switch off so you don't stress/bust the pump. But a little coordination can clear that hurdle. On a gravity feed this is not an issue.