Effects of Different Slopes and Fertilizer Types on the Grey Water Footprint of Maize Production in the Black Soil Region of China

Abstract Grey water footprints (GWFs) can be used as an indicator to describe the influence of diffuse pollution on water environments and identify major contaminants. To improve the calculation of GWF, we conducted a field experiment with combinations of different slopes and fertilizer types on maize production in the black soil region of China. The goals of this study were to determine the actual amount of water used to dilute the pollutants; to explore the changes in the GWF under different slopes and fertilization types; and to identify the most critical pollutants and determine if they are consistent with those identified in previous studies. The results showed that the average GWFs of maize production were much different in 2016 and 2017. The GWFs of the 5° plots were much larger than those of the 1° plots and 3° plots, and the GWFs of the mineral fertilizer plots were larger than those of the organic manure plots in most cases. The loss rates of total nitrogen (TN) in the mineral fertilizer plots and the organic manure plots were all 0.2% in 2016 and 2.7% and 3.1% in 2017, respectively, which was much lower than 10% as reported in most articles. The most frequent critical pollutant was total nitrogen (TN), while total phosphorus (TP) and chemical oxygen demand (COD) were also critical pollutants in some cases, which differed somewhat from the results of previous studies. The uneven annual distribution of rainfall led to large interannual differences in the size of the GWFs. Therefore, using field observations, pollutant loss from agricultural ecosystems could be determined in line with local conditions, which should provide a reference for relevant measures to control diffuse pollution.