Robert Carter Sep 19, 2019:

I have virtually no experience in this field at all, but independently I came to the same conclusion as Tomasso (who does seem very experienced).
Marcha larga = high/higher gear
Marcha corta = low/lower gear
A couple of references:

En la marcha 6 se consiguen los 7 km/h al régimen nominal. Es la que hemos llamado "Marcha Corta". En la marcha 8 se consiguen los 7 km/h a 1.800 r/min. Esa sería la que hemos llamado "Marcha Larga".
http://www.terralia.com/terralias/view_report?magazine_repor...

He tested shifting to a higher tractor gear and slowing engine speed to maintain the desired ground speed.
https://sprayers101.com/gear-up-throttle-down/

Tomasso Sep 19, 2019:

gear reduction or lack of same Reverse gear is too fast ( ratio too low) when backing up to attach tools,( plow, ditcher, 3 point ) a slower gear would be better .(higher ratio)

If a tractor has a high gear reverse, it lunges quickly, assuming CLUTCH and standard transmission) releasing the clutch is tricky, if it has AUTOMATIC trans, it is more flexible and may include temporary reduction through a torque multi plate amplifier.