Effects of Partial Blackwater Substitution on Soil Potential NI-Trogen Leaching in a Summer Maize Field on the North China Plain

In China, promoting harmless blackwater treatment and resource utilization in rural areas is a priority of the “toilet revolution”. Exploring the effects of blackwater application in arid areas on soil nitrogen losses can provide a basis for more effective water and fertilizer management. This study analyzed nitrogen leaching and maize yield under blackwater application in the summer maize season of 2020. A total of 5 treatments were used: no fertilizer, single chemical fertilizer application (CF), single blackwater application (HH), and combined chemical fertilizer and blackwater application ratios of 1:1 (CH1) and 2:1 (CH2). The total nitrogen leached from the fertilization treatments was 53.14–60.95 kg·ha−1 and the leached nitrate nitrogen was 34.10–40.62 kg·ha−1. Nitrate nitrogen accounted for 50–62% of the total leached nitrogen. Compared with blackwater treatments, nitrate nitrogen moved into deeper soil layers (80–100 cm depth) during the CF treatment. Compared with CF, HH significantly reduced the maize yield by 24.39%. The nitrogen surplus of HH was higher than that of other fertilizer treatments. Considering nitrogen leaching, maize yield, and economic benefits, the CH2 treatment presented the optimal results. These findings address knowledge gaps and assist in guiding policy-makers to effectively promote China’s “toilet revolution”.

Inequality of nitrogen use and loss in global croplands caused by climate change

Maintaining food production while reducing agricultural pollution is a grand challenge under the threats of global climate change, which has exerted negative impacts on agricultural sustainability. How agricultural nitrogen use and loss respond to climate change is rarely understood. Here we show that climate change leads to inequality of cropland nitrogen use and loss across global regions based on historical data for the period 1961-2018 from 143 countries. Increases of yield, nitrogen surplus and nitrogen use efficiency (NUE) are identified in 30% of countries, while reductions are observed for the remaining 70% of countries, as a result of climate change. Farm size changes further intensify the inequality of nitrogen use and pollution in global croplands. Yet, enlarging farm size can facilitate climate change adaptation, by which global cropland NUE could be increased by one-third in 2100 compared to 2018 under future shared socioeconomic pathways. Our results would be of great significance to sustain global agriculture as well as eliminate national inequalities on food production and agricultural pollution control.

The response of potato tuber yield, nitrogen uptake, soil nitrate nitrogen to different nitrogen rates in red soil

Nutrient-deficient red soil found in the southern region of China is increasingly being used for potato crops to meet the demand for this staple food. The application of nitrogen fertilizer is necessary to support the production of higher tuber yields; however, the links between nitrate nitrogen and the nitrogen balance in red soil are unknown. A field experiment was conducted in Jiangxi Province in 2017 and 2018 to determine the effects of different nitrogen application rates, 0 kg ha−1 (N0), 60 kg ha−1 (N60), 120 kg ha−1 (N120), 150 kg ha−1 (N150), 180 kg ha−1 (N180), 210 kg ha−1 (N210), and 240 kg ha−1 (N240, the highest rate used by local farmers), on potatoes growing in red soil. Data on tuber yield, crop nitrogen uptake, and the apparent nitrogen balance from the different treatments were collected when potatoes were harvested. Additionally, the content and stock of nitrate nitrogen at different soil depths were also measured. Nitrogen fertilization increased tuber yield but not significantly at application rates higher than 150 kg ha−1. We estimated that the threshold rates of nitrogen fertilizer application were 191 kg ha−1 in 2017 and 227 kg ha−1 in 2018, where the respective tuber yields were 19.7 and 20.4 t ha−1. Nitrogen uptake in potato in all nitrogen fertilization treatments was greater than that in N0 by 61.2–237% and 76.4–284% in 2017 and 2018, respectively. The apparent nitrogen surplus (the amount of nitrogen remaining from any nitrogen input minus nitrogen uptake) increased with increasing nitrogen application rates. The nitrate nitrogen stock at a soil depth of 0–60 cm was higher in the 210 and 240 kg ha−1 nitrogen rate treatments than in the other treatments. Moreover, double linear equations indicated that greater levels of nitrogen surplus increased the nitrate nitrogen content and stock in soils at 0–60 cm depths. Therefore, we estimate that the highest tuber yields of potato can be attained when 191–227 kg ha−1 nitrogen fertilizer is applied to red soil. Thus, the risk of nitrate nitrogen leaching from red soil increases exponentially when the apparent nitrogen balance rises above 94.3–100 kg ha−1.

Improving Horse Welfare and Environmental Sustainability in Horse Husbandry: Linkage between Turnout and Nitrogen Surplus

A scientific consultation tool is currently being developed in Germany to assess, analyze, and improve animal welfare on site and simultaneously consider aspects of environmental sustainability in horse husbandry in order to contribute to a resource-conserving and responsible handling of natural resources and the welfare of living beings. To date, no study has assessed to what extent species-appropriate free-range locomotion possibilities are implemented on horse farms and to what extent turnout areas are affected by unwanted nutrient inputs from horse excretions. Using the indicators “species-appropriate turnout” (hereafter: “turnout”) and “unwanted nitrogen inputs in water bodies” (based on “nitrogen surplus”), we exemplarily examine animal- and environmentally relevant aspects of horse husbandry. We conducted 88 assessments on 46 horse farms (n = 2220 horses) to test literature-based indicators of animal welfare and environmental sustainability. We found that the indicator “nitrogen surplus,” used to assess an aspect of environmental sustainability, was mostly a problem in the wintertime (summertime = −4.24, range: −109.27–58.97; wintertime: mean: 12.01, range: −35.19–468.00 nitrogen surplus per hectare, n = 44 farms, p < 0.001), when the horses had a reduced space allowance for free locomotion. On most farms, “turnout” was provided daily for several hours, but in many of the single housing systems, not all horses had the possibility for free locomotion (24.1 ± 20.4% of horses per farm), which is unacceptable in terms of animal welfare. Husbandry systems with a large enough space allowance for turnout (≥200 m2 per horse) were found to be measures with a valuable synergetic effect, providing a resource which is an opportunity both for an environmentally sustainable and welfare-friendly horse husbandry. Demanuring remarkably decreased the nitrogen surplus (p < 0.001). Hence, based on the study, we recommend to daily demanure the pasture or paddock if the space allowance is less than 200 m2 per horse. In conclusion, regarding animal welfare, group housing is favorable, but regarding a site-specific environmentally friendly or even biodiversity-enhancing management, space allowance per horse is a crucial factor rather than the type of housing system. The two selected exemplary indictors demonstrate the need for a holistic and comprehensive decision support system that considers the linkage between horse welfare and environmental sustainability in order to assist peoples’ decision-making with horses under their care.

Assessment of Nitrogen Flows at Farm and Regional Level When Developing the Manure Management System for Large-Scale Livestock Enterprises in North-West Russia

Arranging efficient manure management is the major environmental challenge in livestock farming in the Leningrad Region, with manure nitrogen being regarded as the main pollution source. The study aimed to identify the baselines for taking integrated manure management decisions towards reducing nitrogen losses applying nitrogen surplus and nitrogen use efficiency (NUE) as indicators calculated at the regional and municipal district level. At the regional level, NUE was found to be 34% and N surplus was 103 kg ha−1. Eleven “environmentally friendly” districts had a mean NUE of 59%, a mean N surplus 39.6 kg ha−1 and a mean animal density 0.89 LSU ha−1. Four districts were identified as “hot spots”, with an animal density in the range from 2.6 to 67 LSU ha−1, NUE from 1 to 37% and N surplus from 87 to 3082 kg ha−1. A scenario was suggested for the redistribution of organic fertilisers between “hot spots” and “environmentally friendly” districts, allowing each district to increase the N surplus to the regional value. Nitrogen flows and measures improving NUE at the farm level through organisational activity and advanced practices were considered with the help of the “N input − N output” diagram and the example of the nitrogen flows on a pilot dairy farm.

The Nitrogen Budget of Coastal Eastern Guangdong in the Last 15 Years

Nitrogen pollution has caused severe ecological and environmental crisis, especially in densely populated coastal regions. Using a mathematical model based on statistical data series from industry, agriculture, environmental protection, and population in 2000, 2005, 2010, and 2015, this paper aims to estimate the nitrogen income and expenditure of coastal Eastern Guangdong, to reveal the temporal variation of the nitrogen budget in the coastal region with high agriculture intensity, and to suggest a management strategy for the local nitrogen control. The results show that: coastal Eastern Guangdong is a nitrogen surplus region, with nitrogen load and nitrogen flux varying in the range 276.01–299.60 kg N ha−1 yr−1 and 221.26–239.06 kg N ha−1 yr−1, respectively, during the period 2000–2015; from 2000 to 2015, the overall nitrogen surplus and the nitrogen surplus unit area showed an obvious upward trend, indicating that nitrogen pollution in the area was deteriorating; agricultural used fertilizer serves as the main contributor to nitrogen input, while water nitrogen accounts for the highest portion of nitrogen output; despite the fluctuation of nitrogen input and output, water nitrogen output steadily increased, suggesting a stronger water environment management requirement. This research provides reference for researchers and decision-makers in the ecological and environmental domains.

“Application of Hydrological Simulation models to solve pollution impacts in the water management decision-making processes. Measures for the recovery of Mar Menor sea lake and “Campo de Cartagena” aquifer (Spain)”

&lt;p&gt;The use of fertilizers and pesticides in agriculture activity is a worldwide extended practice since decades for improving crops performance, which can cause, however, with excessive dosage rates, aquifers&amp;#8217; pollution and water quality problems, like the study case hereby presented of Mar Menor sea-lake waterbody and &amp;#8220;Campo de Cartagena&amp;#8221; aquifer, in the southern coast of Spain.&lt;/p&gt;&lt;p&gt;Due the agricultural practices, the Campo de Cartagena aquifer presents in this moment high values of nitrate, around 150 mgNO&lt;sub&gt;3&lt;/sub&gt; / l, appearing also these high values of nitrogen in soil in this area. This situation produces a great contribution of nitrogen to the Mar Menor lake, by two mainly processes, firstly, continuously through groundwater returns to the waterbody&amp;#8217;s surface and secondly, through the precipitation events when a large amount of nitrogen is washed from soil by the rainfall. Finally, the large amount of nitrogen incomes to the Mar Menor sea lake contributes to deteriorate the status of this waterbody and also promotes the eutrophication processes that have been taking place during last years.&lt;/p&gt;&lt;p&gt;A large watershed scale nitrates&amp;#8217; transport simulation model, Patrical Model (Perez-Mart&amp;#237;n et al., 2016), is used to estimate the measures to recovery the &amp;#8220;Campo de Cartagena&amp;#8221; aquifer. The model establishes, mathematically, the relationship between nitrogen application, nitrogen surplus (excess), and nitrate concentration in groundwater and surface waterbodies.&lt;/p&gt;&lt;p&gt;Model results show that it is necessary to reduce around 80% of the current nitrogen surplus in the &amp;#8220;Campo de Cartagena&amp;#8221; aquifer to recovery the good status in the aquifer. This reduction of nitrogen surplus can be obtained by reducing the fertilizers dosage and consequently the nitrates contribution, with a maximum dose of nitrogen applied by farmers of 170 kgN /ha. Applying this measure could reduce significantly the nitrogen retained in soil in 1-2 years, so the nitrogen contribution during rainfall events also could be reduced significantly. Nitrogen levels in groundwater will gradually decrease in the following years, reaching values around 50 mgNO&lt;sub&gt;3&lt;/sub&gt; / l in 7-9 years after the application of these measures.&lt;/p&gt;

Understanding the Impact of a Major Hydro-Agricultural Project in Low Mondego Area (Portugal)

The Low Mondego (Baixo Mondego, in Portuguese) river basin has been considerably modified by human interventions to prevent floods and to improve agricultural conditions over recent decades. This work analyzes the main impacts arising from those interventions and the socio-economic context in which they occurred. The development and application of a framework to compute the variation of the nitrogen surplus between 1986 and 2018 in the Low Mondego watershed in the central part Portugal is presented. The nitrogen mass balances take into consideration different land use types, inputs and outputs, thereby making it possible to understand how human interventions have impacted the variation of the surplus. It is noticeable that the major nitrogen sources are related to the agricultural sector. However, factors such as the implementation of the Code of Good Agricultural Practices, as well as social conditions, and regulations to reduce nitrogen emissions to the atmosphere helped to cut the nitrogen surplus. This work shows how improving the agricultural conditions has served to increase the crop productivity in improved areas. Very particular social circumstances led to the reduction in anthropogenic nitrogen sources, which has been accompanied by a decline in the nitrogen that is exported at the river outlet.