In Shulchan Aruch Even Ha'ezer siman 1 siff 8, the Mechaber as explained by the Beis Shmuel, has multiple levels of chiuv for a person to marry a woman of childbearing capabilities, and what his chiyuv would be to sell a Seffer Torah in order to marry her. If he has kids (i.e. yotzeh pru urvu), or if he does not have kids, or just to get married so as not to live alone and possibly come to aveira. The Beis Shmuel explains that marrying to have more children is only Derabanan and therefore we are not so machmir so we wouldn't force him to marry (back when that was enforced).
Most importantly though is the Ramma who mentions some cases where he should not mary a women of childbearing capabilities, one of them is if he already has many kids and he is afraid that marrying a new woman who will have kids will cause fighting between his children and his wife, than it is allowed to marry a woman who cannot have children.
This is the closest to population planning you will get. Its all on a personal level, which the mitzvah is, personal, not societal. Notice also its only about a new wife, no hetter to be mishamesh bimoch with the childbearing wife, even for fear of yorshim fighting. One more point is he is addressing a real fear of yorshim fighting. Worrying about running out of earth started with Kayin and Hevel and has continued ever since, as of yet it is hard to justify as a real fear, but then we might not need a real fear, just the type of fear that gets people to fight. And land is definitely a good one at that.