How can nitrogen be fixed in agricultural soil?

Nitrogen fixation in agricultural soil primarily occurs through the symbiotic relationship between legumes and specific bacteria, such as Rhizobium species. These bacteria inhabit the root nodules of legumes and have the unique ability to convert atmospheric nitrogen (N₂) into ammonia (NH₃), which plants can then utilize for growth. This process enriches the soil with usable nitrogen, enhancing soil fertility without the need for synthetic fertilizers.

Legumes, such as clover, peas, and beans, are especially important in this context because they can thrive in nitrogen-poor soils while simultaneously contributing to soil nitrogen levels. This natural method of nitrogen fixation is not only beneficial for the crop rotation systems but also improves overall soil health and reduces dependence on chemical interventions.

In contrast, irrigation techniques, synthetic fertilizers, and frequent tilling do not contribute to the natural fixation of nitrogen in the soil. Instead, irrigation primarily focuses on water delivery, synthetic fertilizers provide nitrogen in a ready-to-use form but do not promote fixation, and tilling can lead to erosion and a decrease in soil structure rather than enhancing nitrogen levels. Thus, the relationship between legumes and nitrogen-fixing bacteria stands out as the most effective and sustainable method for improving nitrogen availability in agricultural soils.