Slightly dark, clods crumble. The suggestions below are the most common seen for improving furrow irrigation. Water must infiltrate as evenly as possible across a field. Then, try to improve control over the total infiltration and reduce or reuse surface runoff. This all assumes that you have a reasonably accurate estimate of how much water is actually needed.
Water has to advance faster in lighter soils than in heavier.
Note that you don't necessarily want even water advance in all furrows. This may mean using a higher flow for a shorter time in non-wheel rows. If primarily cross the field, surge irrigation may help since surge acts to reduce infiltration rates quickly. Utilize an irrigation scheduling system so that you have reasonably accurate estimates of WHEN and HOW MUCH to irrigate. Install a tailwater reuse system - improves overall irrigation efficiency by saving tailwater for reuse.