If you have a stream or any sort of water in the area you would be eligible to put a 180 ft buffer of trees on it with the Riparian Buffer CRP program. Of course that is just like any other CRP contract in that is pays a portion of the cost to plant the trees, and then you get an annual payment for the next 10-15 years.
If there is no water, you are likely not eligible for any of the other CRP options. Your next best option to improve the habitat would be a cost sharing program. These do not come with an annual payment, but they do cover a portion of the cost of planting the trees or shrubs.
The 3 most common cost share programs in Iowa are REAP (state program), EQIP, and WHIP (both federal programs). There is a minimum of 3 acres necessary to qualify for a REAP tree planting and would cover 75% of the cost up to a maximum of $600/acre ($450 paid for if it cost $600/acre). EQIP and WHIP are flat rate payment programs with no minimums to qualify. Flat rate means there are established rates for each forestry practice ($270/acre for EQIP) and no matter how much the planting costs, you will receive the set rate.
REAP funds are pretty short in a lot of counties, but EQIP is usually quite available. If you are thinking EQIP, you should stop into your local NRCS office and get signed up as they are having another ranking and the sign up deadline is March 30th.
Best bet is to stop into your local NRCS office and discuss your options with them. They will help you determine what you are eligible for and what your best option may be.