The overpopulation stories are pretty much a myth, and "The Population Bomb" (source of many of these myths) has been thoroughly debunked, just like "Silent Spring"
Farm subsidies arent tax breaks. They are direct payments to the farmer for each unit of a crop grown (52 cents per bushel harvested for wheat) which acts like an artificial increase in the market price for wheat. they were instituted specifically to increase production of particular crops to stabilize supply, and therefore prices, and to encourage greater production of crops that are usually not the most lucrative choice. (tomatoes pay more per acre than corn, until you add the subsidy) They also help to avert market gluts,where every farmer comes to the same decision about crop planting, and the market is flooded with say... watermelons, but there isnt a carrot in sight.
The downside to subsidies is the lack of a cap on payments. for smaller farmers with a hundred acres or less, a guaranteed minimum of $22.40 per acre (average wheat harvest of 35-40 bushels an acre x government guaranteed minimum price per bushel of 56 cents, so if wheat drops below 56 cents = $22.40/acre) isnt going to make him plant wheat instead of unsubsidized barley,($4.40/bushel x average barley harvest of 66.7 bushels/acre = $293.48/acre) but if you got 1/2 a million acres, that guaranteed $20 per acre becomes a fine choice, covering your investments and labour even if the bottom drops out of the wheat market, and all you get its the govt payout of 56 cents a bushel. if the bottom drops out of the barley market, you could get stuck with a crop that costs more to harvest than it's worth.
Crop subsidies with a cap of even $1 million/year per "farmer" (Archer Daniels Midland being counted as 1 farmer) would eliminate some of the advantage the super-corps and agricultural giants exercise over the small farmer, and actually making them pay real property taxes like a real farmer, instead of depreciated investment taxes would kick them square in the nuts.
As to the tax break for children, the deduction for children is just like the personal deduction for income tax. Their personal deduction is just claimed by their guardian rather than themselves. The actual cost of feeding clothing and housing crib-midgets is far higher than the deduction, so only a daft moron would use the child tax deduction as his impetus to reproduce... But then there are a lot of real pea-brains on the loose these days, and they seem to be voting Obama.
Welfare Foodstamps WIC and other "safety net" programs do increase payments "PER UNIT" (that's what they call kids in Dept. of Health and Human Services memos). In California, the payout increases significantly with each additional UNIT of yard-monster production, up to a limit of 9 UNITS. Course any sensible shopper will tell you, after 9 the cost per UNIT drops dramatically so thats just good sense... When you have been offered a $200 book of foodstamps for $20 by a bitch driving a new mercedes, you have to wonder who runs these programs. (happened to me in SF, in 1999) Sadly, those who will misuse the system are also those most likely to reproduce, by design or by stupidity. I dont want starving crotch-droppings littering the streets of every urban center,but I also dont want Welfare-Millionaires suckling at the government teat. It's a conundrum. Maybe we can feed the Welfare-Millionaires to poor children, like Soylent Green. Lets test this out by first Soylentizing the Congress and Senate. Why just the fat content between their ears could feed the nation for months!