Orchard Expansion May Diminish Groundwater Replenishment While Amplifying Nitrate Pollution in a Cultivated Loess Critical Zone

Niu, Liantao and Jia, Xiaoxu and Yang, Xiaofan and Yang, Ting and Turkeltaub, Tuvia and Binley, Andrew and Vanderborght, Jan and Ren, Lidong and Liao, Xiaoyong and Shao, Ming'an (2025) Orchard Expansion May Diminish Groundwater Replenishment While Amplifying Nitrate Pollution in a Cultivated Loess Critical Zone. Water Resources Research, 61 (10): e2025WR040. ISSN 0043-1397

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Abstract

Plain Language Summary: Agricultural land‐use and management changes significantly alter vadose zone hydrology and nitrate (NO3−) transport within the Earth's Critical Zone (CZ). In this study, we built a model that uses many vertical soil columns to represent the soil. We used this model to estimate how much water reaches the groundwater and how much NO3− moves downward under two land use systems: traditional cropland and orchards. We also tested how differences in soil hydraulic properties affect the results. These differences create large uncertainties in the predicted amount of water recharge and NO3− leakage, especially in orchards. In the central and eastern parts of the region, groundwater is more susceptible to NO3− pollution. Converting cropland to orchards reduces the amount of water reaching the groundwater but increases the amount of NO3− moving downward, raising the risk of groundwater pollution. Future large‐scale shifts from croplands to orchards require caution, particularly in regions with shallow soil and coarse texture.