Sustainable agriculture means growing food in ways that protect soil, water, and ecosystems so farms can keep producing long-term. It’s important because it prevents soil erosion, maintains fertility, reduces pollution, and supports food security—issues tested in Unit 5 (Land and Water Use) on the APES exam (Unit 5 = 10–15% of multiple choice) and tied to Learning Objective STB-1.E. Key practices include contour plowing, windbreaks, terracing, no-till and strip cropping, perennial crops and cover crops, crop rotation, adding green manure/limestone (liming), agroforestry, polyculture, rotational grazing to prevent overgrazing, and compost/cover crops to boost organic matter and water-holding capacity. These methods reduce erosion, improve nutrient cycling, and lower reliance on synthetic inputs—topics you’ll see in free-response and multiple-choice questions. For a focused review, see the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn), the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Contour plowing prevents soil erosion by following the natural contours (curved lines of equal elevation) of a slope when planting and tilling. Instead of rows running downhill, the furrows run perpendicular to runoff. That slows water flow, so less surface runoff and less ability for water to carry soil particles downhill. Slower water also has more chance to infiltrate, increasing soil moisture and reducing sheet erosion. Over time, sediment collects in the furrows, creating small natural barriers that further reduce erosion—an effect similar to terracing but simpler to implement. This method is listed in the CED under EK STB-1.E as a soil conservation practice; it’s often paired with cover crops or strip cropping for better results. For a quick AP review, see the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

No-till agriculture means you plant crops without plowing or turning over the soil. Instead of regular tilling, seeds are placed directly into residue from the previous crop. The key differences: no-till preserves soil structure and plant cover, which reduces soil erosion (EK STB-1.E.1), increases organic matter and water-holding capacity, and helps sequester carbon. Regular (conventional) farming uses tillage to loosen soil and control weeds, which can increase erosion, decrease soil organic matter, and disrupt soil organisms. Trade-offs: no-till often reduces fuel use and runoff and supports soil conservation (contour plowing, cover crops are complementary), but it may rely more on herbicides for weed control and can require new equipment/management. For AP exam focus, know no-till is listed as a soil-conservation strategy in Topic 5.15 (see the Topic study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn)). For practice, check Fiveable’s APES problems (https://library.fiveable.me/practice/ap-environmental-science).

Crop rotation improves soil fertility in a few clear ways that match the CED: instead of planting the same crop that depletes the same nutrients year after year, farmers alternate crops with different nutrient needs and rooting patterns (EK STB-1.E.2). Planting a legume (like clover or soy) in the rotation adds nitrogen because of symbiotic N-fixing bacteria, so the next crop benefits without extra synthetic N. Different roots exploit different soil layers, reducing nutrient depletion and improving structure. Rotations also let you use green manure or cover crops to return organic matter, which increases cation exchange capacity and water-holding ability. Finally, rotations break pest and disease cycles, so soils stay healthier and need fewer chemical inputs. This is a key sustainable practice on the APES CED (STB-1.E); review Topic 5.15 on Fiveable (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and try practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Farmers use windbreaks to reduce wind erosion and protect soil, crops, and livestock. Windbreaks are rows of trees, shrubs, or tall vegetation planted perpendicular to prevailing winds; they slow wind speed near the ground, which lowers the amount of topsoil blown away and reduces evapotranspiration from crops. By breaking the wind they also trap drifting snow (improving soil moisture) and create microclimates that can raise crop yields. Roots from windbreak plants increase soil stability and add organic matter, helping long-term soil conservation—one of the EK goals in the CED (EK STB-1.E.1). Windbreaks are a sustainable ag practice you should know for Unit 5 (Land and Water Use). For a quick refresher, see the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and more unit resources (https://library.fiveable.me/ap-environmental-science/unit-5). For extra practice, try the APES question bank (https://library.fiveable.me/practice/ap-environmental-science).

Green manure is a cover crop you grow specifically to improve the soil, then cut and mix into the field before it flowers. Think legumes (like clover or vetch) or fast-growing grasses planted between cash crops—they prevent erosion, add organic matter, and (if they’re legumes) add nitrogen through nitrogen fixation. Farmers use green manure as part of crop rotation and soil-fertility strategies (EK STB-1.E.2 on the CED). On the AP exam you might see it as a method to improve soil fertility or reduce erosion compared to leaving fields bare. For a quick review, check the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn). Need more practice? Fiveable has lots of APES practice problems (https://library.fiveable.me/practice/ap-environmental-science).

When livestock overgraze an area they remove too much vegetation, damaging plant roots and reducing ground cover. That leads to increased soil erosion (wind and water), lower water infiltration, loss of soil fertility, reduced plant diversity, and—in extreme cases—desertification. Overgrazed soil also stores less carbon and lets nutrients wash away, so future productivity falls. Rotational grazing fixes this by regularly moving animals between fenced paddocks so no one pasture is grazed continuously (that’s the CED idea of “regular rotation of livestock”). Each paddock gets a recovery period for plants to regrow roots and rebuild ground cover, which restores soil structure, reduces erosion, improves water infiltration and fertility, and often increases plant diversity. It essentially mimics natural herd movement and is listed as a sustainable soil/land management practice in the CED (STB-1.E). Review this topic’s study guide for AP-aligned details (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and try practice questions for Unit 5 (https://library.fiveable.me/practice/ap-environmental-science).

Terraces are basically flat “steps” cut into a hillside that break one long steep slope into many shorter, gentler slopes. That does three important APES things: it reduces slope steepness and slope length (so gravity-driven runoff has less energy), it slows water so more can infiltrate instead of running off, and it traps soil and sediment on each step instead of letting it wash downhill. Slower runoff means less sheet, rill, and gully erosion and better water for crops (increased infiltration). Terracing is listed in the CED as a soil-conservation method (alongside contour plowing, strip cropping, etc.), so it’s a classic sustainable-agriculture practice you should be able to describe on the exam. For a quick review on terracing and other conservation strategies, check the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) or the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5). For extra practice, try related problems at (https://library.fiveable.me/practice/ap-environmental-science).

Strip cropping is a soil-conservation planting pattern that alternates strips of different crops (often a row crop with a cover crop or perennial) across a slope to reduce erosion and slow runoff. The idea is the strips interrupt water flow and trap sediment, protecting topsoil—so it directly helps prevent soil erosion (CED EK STB-1.E.1). Regular crop planting usually means planting one crop continuously across a field (monoculture) with rows oriented without those alternating protective strips; that’s more vulnerable to erosion, especially on slopes or in heavy rain. Key differences: strip cropping alternates crops and often follows contours to slow runoff; regular planting is uniform and less effective at conserving soil. Strip cropping is an AP-relevant soil conservation strategy you should know for Unit 5 (see the Topic 5.15 study guide for more: https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn). For extra practice, try problems at (https://library.fiveable.me/practice/ap-environmental-science).

Farmers add limestone (liming) to raise acidic soils’ pH. Acidic soils lock up nutrients and can release toxic aluminum and manganese. Adding ground limestone (calcium carbonate, sometimes with magnesium) neutralizes H+ ions, increases pH, and makes nutrients like nitrogen, phosphorus, and potassium more available to plants. It also improves soil structure and boosts beneficial microbial activity that helps decompose organic matter and cycle nutrients. Limestone can therefore increase crop yield and reduce metal toxicity in roots. This matches EK STB-1.E.2 (strategies to improve soil fertility include adding limestone). If you want a quick review for APES Topic 5.15, check the Sustainable Agriculture study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and practice problems (https://library.fiveable.me/practice/ap-environmental-science)—both are useful for free-response questions about soil management.

Perennials hold soil better than annuals mainly because they don’t get pulled up every year. Their deep, permanent root systems bind soil, increase porosity, and keep organic matter in place—so you get less erosion from wind and water (that’s exactly what the CED lists under soil conservation: perennial crops, no-till, contour plowing, windbreaks). Because you don’t till as often with perennials, you disturb soil less, which preserves structure and microbial life and reduces runoff and nutrient loss. Perennials also provide year-round ground cover (like cover crops or agroforestry), cutting erosion during rainy seasons when annual fields are bare. For APES, link this to STB-1.E (soil conservation methods) in Unit 5: Land and Water Use. For a quick topic refresher, see the Sustainable Agriculture study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and more practice questions at (https://library.fiveable.me/practice/ap-environmental-science).

For the AP exam you should memorize the key soil-conservation methods and fertility strategies listed in the CED. Main erosion-prevention methods: contour plowing, windbreaks (shelterbelts), planting perennial crops, terracing, no-till agriculture, and strip cropping. To improve soil fertility: crop rotation, adding green manure/cover crops, and liming (adding limestone) to adjust pH. Also know rotational grazing to prevent overgrazing. Be ready to describe how each reduces erosion or boosts fertility (e.g., terraces slow runoff; no-till keeps soil structure; green manure returns nutrients). These are directly tied to EK STB-1.E.1–1.E.3 and often show up in multiple-choice or FRQ solutions about sustainable agriculture (Unit 5). For a focused review see the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5). For extra practice try their APES question bank (https://library.fiveable.me/practice/ap-environmental-science).

Rotational grazing is moving livestock regularly between pastures so no single area gets overgrazed (CED: rotational grazing—EK STB-1.E.3). That benefits animals because they get access to fresher, higher-quality forage, better nutrition, and reduced parasite loads (pastures rest breaks break parasite cycles). It benefits the environment by preventing overgrazing, which reduces soil erosion, soil compaction, and loss of plant cover—helping conserve soil and maintain water infiltration (link to soil conservation methods in the CED). Rested paddocks recover biomass and root systems, which improves nutrient cycling, increases plant biodiversity, and can boost carbon sequestration in soils. On the AP exam, you might be asked to describe how rotational grazing prevents overgrazing and supports soil health (Unit 5 content). For a quick topic review, check the Sustainable Agriculture study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Sustainable agriculture reduces environmental problems by keeping soil, water, and ecosystems healthy so farms don’t become sources of pollution or habitat loss. Practices from the CED—contour plowing, windbreaks, terracing, no-till, strip cropping, cover crops, perennial crops, crop rotation, green manure, liming, agroforestry, polyculture, and rotational grazing—prevent soil erosion, maintain fertility, reduce runoff of sediments and fertilizers, and limit overgrazing. That lowers nutrient runoff and eutrophication, reduces need for synthetic fertilizer (cutting greenhouse-gas and fossil-fuel use), and preserves biodiversity and habitat. On the AP exam, you should be able to name these methods (EK STB-1.E.1–1.E.3) and explain how they prevent specific problems (soil loss, decreased fertility, water pollution, overgrazing). For a focused review check the Topic 5.15 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn), the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Soil erosion’s a big deal because it removes the topsoil that holds most nutrients and organic matter, lowering crop yields, increasing runoff and sediment in waterways, and reducing soil’s water-holding capacity—all of which harm ecosystems and food security (Unit 5 content). The best ways to stop it are the soil-conservation practices named in the CED: contour plowing, terracing, strip cropping, windbreaks, planting perennial crops and cover crops, and no-till agriculture. Improve fertility and resilience with crop rotation, green manure (cover crops plowed in), and liming to correct pH. For grazing land, use rotational grazing to avoid overgrazing and erosion. These are common AP solutions you should recognize for free-response questions about land-use problems. Review the Topic 5.15 study guide for concise examples and diagrams (https://library.fiveable.me/ap-environmental-science/unit-5/sustainable-agriculture/study-guide/NstFolnzQv41vpfvpFNn) and practice applying these in FRQs at (https://library.fiveable.me/practice/ap-environmental-science).