The Gemara in Bava Kama 28a says:
ת"ש בעל הבית שהניח פאה מצד אחד ובאו עניים ונטלו מצד אחר זה וזה פאה וא"א עביד איניש דינא לנפשיה אמאי זה וזה פאה לנקוט פזר וליתיב אמר רבא מאי זה וזה פאה לפוטרן מן המעשר כדתניא המפקיר את כרמו והשכים בבקר ובצרו חייב בפרט ובעוללות ובשכחה ובפאה ופטור מן המעשר
(Translation of the relevant part): What is meant by the ruling of: This produce and that produce are both considered pe’a? It means that they are considered pe’a with regard to exempting both portions of produce from tithes. Just as the portion that the poor people took is exempt from tithes, so is the portion that he allocated initially. This is as it is taught in a baraita: In the case of one who renounces ownership of his vineyard and arose early in the morning before anyone else took possession of it and harvested it, the one who renounces ownership is obligated in the mitzva of individual fallen grapes left for the poor [peret], and in the mitzva of incompletely formed clusters of grapes left for the poor [olelot], and in the mitzva of forgotten clusters of grapes left for the poor, and in the mitzva of pe’a, the four gifts to the poor that the Torah requires one to give from a vineyard (see Leviticus 19:9–10). But he is exempt from the mitzva to tithe his produce, because this requirement does not apply to an ownerless field. Likewise, in the above case the portion of the field that was allocated for pe’a is exempt from tithes even after the owner reclaims it, as pe’a is considered ownerless property in this regard.
Rashi explains here that even though the owner reclaimed the part of the field he designated as pe'ah, it is exempt from ma'aserot (דאף פאה הנשארת הפקר חשיבא ואע"ג דנקט לה איהו פטורה ממעשר).
So couldn't a person theoretically designate 99% of his field as pe'ah (since one can't designate all of it, as per Tosefta Peah 1:1) and then reclaim all of it (excluding the part that actually needs to be given as pe'ah, i.e., 1/60th of his field) and thereby be exempt from giving ma'aser except on that 1%?