Dynamic Effect Of Crop Intercropping On Nitrate Leaching In Agricultural Soils

The nitrogen use efficiency of modern agricultural systems is notoriously poor.About 20%of the nitrogen applied to fertilizer is lost in the form of nitrate and is not absorbed by plants,resulting in waste of resources and pressure on the environment and human health.Especially in intensive vegetable production system,nitrate leaching is very serious due to high-intensity fertilization and irrigation and incomplete development of vegetable roots.Therefore,it is of great significance to study strategies to alleviate nitrate leaching for improving nitrogen utilization efficiency of protected agricultural plants and alleviating non-point source pollution in agricultural systems.Firstly,¹⁵N labeling technology was used to reveal the formation and transformation process of nitrate nitrogen in agricultural soil and its related microbial control mechanism.Secondly,monoculture and intercropping planting modes were designed to find intercropping models with low nitrogen leaching loss and high nitrogen utilization efficiency.Finally,the application of the selected pepper/maize intercropping pattern on the field scale was practiced,at the same time,the mechanism of controlling nitrate leaching in intercropping mode was explored by setting grid and PVC board.This research mainly produces the following results:?1?After urea was applied to three kinds of soils,nitrification driven by AOB and denitrification driven by nir S-type bacteria in neutral high carbon nitrogen soil lead to high NO₃^-leaching loss and high N₂O emission,while nitrification and denitrification in two kinds of acidic soils were mainly driven by AOA and nir K-type bacteria respectively.?2?Intercropping pattern of shallow-rooted pepper with deep-rooted alfalfa and maize depends on enhancing root nutrient absorption in deep soil layer,and increasing nitrogen utilization rate.In particular,pepper/maize intercropping pattern significantly slowed down nitrate leaching,and nitrogen uptake and utilization increased by 28%compared with monoculture.?3?Pepper/maize intercropping pattern planted in the field can significantly slow down nitrogen loss.Luxuriant plant roots and AOB-driven nitrification play an important role in soil NO₃^-retention in the 25-50 cm soil layer.Pepper/maize intercropping system may mainly enhances nutrient absorption through niche complementation between roots,thus increasing soil nitrogen utilization efficiency and effectively reducing apparent nitrogen loss.In a word,pepper/maize intercropping pattern relies on the complementary nutrient preference of roots to enhance nutrient absorption and effectively prevent nitrate leaching,which is of good application value for mitigating non-point source pollution in protected agriculture.