Shelterbelts do fix carbon and some trees do fix nitrogen, but the dominant ecological benefit is their limiting of wind-caused soil erosion. Shelterbelts mimic a forest ecosystem by diverting wind currents away from soil that is often exposed by tilling.

Tilling has the benefit of increasing permeability of the soil for water and creating favorable conditions for young seedlings. No-till farming does not have these benefits, but it does reduce the risk of soil erosion because tilling generally destroys preestablished root systems.

Mulching can actually provide habitat for slugs, while removing mulch and topsoil puts your fields at serious risk of soil depletion and eventual erosion. Flooding your fields is also ineffective and could jeopardize your existing crops (and soil health for that matter!). Finding and squishing every single pest might put a small dent in the crops lost, but how much is your time worth? Mixed cropping is the best option, because many pests are specialists and feed off certain crops (leafy greens, drupes, etc.). Some of your crops will suffer but not all of them. 

Terracing creates level shelves on hillsides to hold water and soil for growing crops. This method can be very expensive. Rangelands are the areas of land that are grazed on by animals. A monoculture refers to the cultivation of a single crop or animal, while a polyculture involves the cultivation of multiple different types of crops and/or animals in a given area.

Vegetation used for green material is typically still-growing or freshly cut. 

Traditional subsistence agriculture provides enough food to support one family and occasionally a surplus to sell, trade, or store.

GMO stands for "genetically modified organisms.” Scientists have manipulated the genetic material of the organism to create more productive crops.   GMO's combine traits from significantly different species, creating an organism that has never occurred in nature. The resultant organism is less stable and likely to be modified, creating toxins or other negative mutations. The benefits of using GMO's include higher crop yields, as well as cultivating crops needing less water that are able to grow in harsher climates.

The farmer should use a nonselective herbicide. We can narrow down the answer choices to herbicides because they are used to control plants and weeds. The question also states that there are multiple species of weeds that the farmer needs to control. This means the farmer should use a nonselective herbicide, which kills multiple species—rather than a selective herbicide that will only kill a certain plant species. Insecticides are the wrong answer choice because they control for insects, not plants. 

IPM stands for "integrated pest management." IPM is a process that minimizes the impact of pests upon agricultural or natural areas that pose minimal risks to people or the environment. In this process farmers may shield disease prone species from pests by planting a barrier of healthy pest resistant crops in front of them.

The correct response is The Green Revolution. The father of this revolution was Norman Borlaug. He received a Nobel Peace Prize in 1970s for his working in the Green Revolution, credited as saving a billion lives because of his involvement in the agricultural enhancements.