Final answer:
Farmers can replace nitrogen in the soil through recycling plant and animal waste, crop rotation, and the use of ammonia-based fertilizers.
Step-by-step explanation:
Farmers can replace nitrogen in the soil by utilizing several methods. One way is through the recycling of plant and animal waste, which is rich in nitrogen. This waste can be composted and added to the soil, providing a natural source of nitrogen. Another method is crop rotation, where different crops are planted in a particular order. This helps to break the cycle of nitrogen depletion, as some crops can fix nitrogen from the air and make it available in the soil. Additionally, farmers can use ammonia-based fertilizers, which are synthetic compounds that contain nitrogen and can supply it directly to the soil.
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