cn2redjeep,
The smaller Kubotas are just like all smaller tractors: low mass and limited horsepower.
The mass affects your ability to "dig into" a load because you cannot carry much momentum and you have little wheel weight and will spin tires quickly. Once into the load, you cannot "lift" and "drive" at the same time without loading up the engine.
A massive CASE loader can gently dig into a load of material and lift away a full bucket because of the overall mass of the machine. Kubota recommends NOT ramming the pile but scraping the front of the pile while lifting and curling the bucket. Takes practice but, its very effective and its easy to get a 75-95% bucket load. You may have to back-drag the material to build up enough to have a chance of filling the bucket. After the pile face gets below 24", you can try rolling scoops, depending on the type of material.
Have your loader checked to make sure it will lift the specified design load, then learn to work within those limitations. It's not a big machine but, they can do a heck of a lot of work when you get used to them.