Abstract: This invention relates to inhibiting leaching of crop treating chemicals into the ground water, aqua-system and surrounding soil of the treatment site by contacting the plant or plant site with an effective leach inhibiting, plant tolerating amount of a lactam containing polymer selected from the group of a crosslinked or non-crosslinked N-alkenyl lactam homopolymer or copolymer with a C.sub.2 to C.sub.30 comonomer selected from the group of an alkenoic acid; an alkenyl- anhydride, ester, ether, amino ester or amino amide and an alpha mono- or di- olefin, in which the lactam unit of the polymer is represented by the formula ##STR1## wherein R is C.sub.3 to C.sub.6 alkylene optionally substituted with C.sub.1 to C.sub.20 alkyl; R.sub.1 and R.sub.2 are each independently C.sub.2 to C.sub.20 alkyl or hydrogen and n has a value of from 0 or 2.