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Interaction with soil mineral particles (SMPs) and organic matters can significantly determine the fate of nanoparticles (NPs) in the environment such as waters, sediments, and soils. In this study, the heteroaggregation of CeO 2 NPs with different soil minerals (kaolinite, montmorillonite, goethite and hematite) and the influence of extracellular polymeric substance (EPS) were studied. The obvious heteroaggregation between CeO 2 NPs with different SMPs were demonstrated via co-settling and aggregation kinetics experiments. The variety in the heteroaggregation between CeO 2 NPs with different SMPs is mainly induced by the difference in their surface properties, such as surface charge, specific surface areas and surface complexation. The presence of EPS can result in great inhibition on the heteroaggregation between CeO 2 NPs with the positive charged goethite by enhancing the electrostatic repulsion between NPs and mineral colloids. However, the influence of EPS on the interaction between CeO 2 NPs with negative charged SMPs is more dependent on the steric stabilization. The presence of EPS may promote the migration of CeO 2 NPs in environment and then increase their risks to human health and ecosystems. These findings contribute to better understanding interactions between NPs and SMPs and have important implications on predicting the behaviors and risks of NPs in the natural environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

The relationships between nitrogen and yield and between water and yield, and the fate of nitrogen under plastic film mulching for spring maize were studied with field plots and microplots in the southern Loess Plateau. The results showed that plastic-film mulching (N120C) could increase maize yield by 46.7%, comparing with no-mulching(N120UC) in same rate of fertilizer. The maize yield potentiality of mulching might be played fully, comparing with CK (no nitrogen), treatments N120 (urea nitrogen 120 kg.hm-2), N180 (urea nitrogen 180 kg.hm-2) and N120 M (urea nitrogen 120 kg.hm-2 + organic manure nitrogen 60 kg.hm-2) could raise grain yield by 41.8%, 43.9% and 34.7%, respectively. Mulching planting raised water use efficiency (WUE) by 57.9%, and raised rainfall use efficiency (RUE) by 54.5%. N120, N180 and N120M improved WUE by 38.4%, 47.4% and 32.4%, respectively, and improved RUE by 42.3%, 43.9% and 34.7%, respectively. Because the organic manure applied was not fully rotted cattle dung, which supplied available nitrogen slowly than urea, it raised yield and WUE to a low extent. Meanwhile, the experiment showed that 73.0%-83.7% of water used by maize from rainfall, which indicated that the key water to determine maize yield was rainfall in spring maize growth period. Mulching planting for maize had little impact on the fate of nitrogen fertilizer. The total recovery of nitrogen had little difference, NUE decreased 7.3%, and residual N in soil raised 6.4%, comparing with N120UC. A great part of the residual N was in 0-20 cm of soil, and no risk occurred for nitrogen leaching and accumulation to deeper soil layers in the first growth season.

The effect of long-term fertilization on the yield of winter wheat was studied on the basis of 18-year located experiment on the Loess Plateau. The results showed that the winter wheat yield increased 418.1 kg.hm-2 under N fertilization, and the average increasing rate was different with precipitation. In average and rain rich year, the average increasing rate were 30.3% and 58.9%, respectively, but in drought year, the yield decreased, and its average decreasing rate was 13.9%. The winter wheat yield under P fertilizer increased in drought year, and decreased in average and rain rich year. The average increasing rate was 6.5% in drought year, and the average decreasing rate was 15.4% and 10.0%, respectively. The average increasing rate in M, NP, PM, NM and NPM was 82.8%, 127.8%, 18.9%, 144.4%, and 169.3%, respectively. In addition, precipitation affected the amount of spike, grains per spike, and weight of thousand-grains.

The NO3(-)-N accumulation and distribution in soil profile of Loess Plateau dry highland were studied by long-term field trials. The results showed that NO3(-)-N was accumulated in the soil profile under N-fertilization. Application of P-fertilizer or organic manure reduced the NO3(-)-N content and its leaching depth in the soil profile. The deepest depth of NO3(-)-N accumulation was 120-200 cm under N treatment, and the peak of the accumulation was the highest in NPM treatment, with the depth of 60-120 cm. The NO3(-)-N accumulation depth was 80-140 cm for NP. Without nitrogen application, there was no evident accumulation of NO3(-)-N in soil profile. The more nitrogen used, the more NO3(-)-N accumulated in soil profile. Under the same nitrogen application rate, NO3(-)-N accumulation might decrease with increasing P application.

On the basis of long-term fertilization experiments in gully area of Loess Plateau, the relationships among fertilizations, NO3(-)-N accumulation, and moisture distribution in soil profiles were evaluated. The results showed that fertilization and rainfall significantly influenced the yields. NO3(-)-was accumulated in soil profiles under N and P fertilizers and organic manure(NPM) and N and P fertilizer (NP) treatment. The accumulated NO3-N reached 340 kg.hm-2 in 60-120 cm under NPM treatment, and 220 kg.hm-2 in 80-140 cm under NP treatment, respectively. Soil moisture in 100-300 cm was significantly reduced under NPM treatment. Under NP treatment, it was significantly reduced in dry year and normal year, while under organic manure(M) treatment, it was significantly reduced in dry year. Soil moisture under P and CK treatments was relatively stable in different years. N uptake under NPM and NP treatments was significantly decreased in dry year. It reflected the close relationship among soil moisture, crops, and fertilization.