[mikepurvis]

For a small bed like the one in the demonstration, surely that's more simply managed with a drip hose and maybe a timer?

Drip hoses are also better from a water consumption point of view since it goes straight to the soil— you don't lose any to runoff or evaporation.

[bluGill]

Large farms put the hoses in the ground - the water never touches the air (well I assume some will seep to the surface, but not much), instead it is applied only close to the roots. You need to be very careful to apply your seeds just above the hose, but this is a solved problem: modern farming can place each seed to within 2cm of where intended over large fields even when the tractor is planting 50 rows at a time at 20km/h.