High ammonia (NH₃) emissions from fertilized soil in China have led to various concerns regarding environmental safety and public health. In response to China's blue skies protection campaign, effective NH₃ reduction measures need to consider both mitigation efficiency and food security. In this context, we conducted a meta-analysis (including 2980 observations from 447 studies) to select effective measures based on absolute (AV) and yield-scaled (YSAV) NH₃ volatilization reduction potential, with the aim of establishing a comprehensive NH₃ mitigation framework covering various crop production sectors, and offering a range of potential solutions. The results showed that manipulating crop density, using an intermittent irrigation regime for paddy field rice, applying N as split applications or partially substituting inorganic fertilizer N with organic N sources could achieve reductions in AV and YSAV reduction of 10–20 %; adopting drip irrigation regimes, adding water surface barrier films to paddy fields, or using double inhibitor (urease and nitrification), slow-release or biofertilizers could achieve 20–40 % mitigation; plastic film mulching, applying fertilizer by irrigation or using controlled-release fertilizers could yield 40–60 % reduction; use of a urease inhibitor, fully substituting fertilizer N with organic N, or applying fertilizer by deep placement could decrease AV and YSAV by over 60 %. In addition, use of soil amendments, applying suitable inorganic N sources, or adopting crop rotation, intercropping or a rice-fish production model all had significant benefits to control AV. The adoption of any particular strategy should consider local accessibility and affordability, direct intervention by local/government authorities and demonstration to encourage the uptake of technologies and practices, particularly in NH₃ pollution hotspot areas. Together, this could ensure food security and environmental sustainability.

Vegetable production in solar greenhouses in northern China results in the excessive use of nitrogen (N) fertilizers and water via flooding irrigation. Both factors result in low N use efficiency and high environmental costs because groundwater becomes contaminated with nitrate (NO3−). Four consecutive tomato (Lycopersicum esculentum Mill.) cropping seasons were tested whether drip fertigation and/or the incorporation of maize straw (S) may significantly reduce NO3− and dissolved organic N (DON) leaching while increasing the water-use efficiency (WUE) and partial factor productivity of applied N (PFPN) of the tomatoes. The following treatments were used: ① conventional flooding irrigation with overfertilization (CIF, 900 kg N ha−1 season−1), ② CIF + S, ③ drip irrigation with optimized fertilization (DIF, 400 kg N ha−1 season−1), ④ DIF + S. We found that (1) DIF significantly increases the PFPN and WUE by 262% and 73% without compromising the yield compared with CIF, respectively. (2) For CIF, approximately 50% of the total N input was leached at a NO3−/DON ratio of approximately 2:1. (3) Compared with CIF, DIF reduced NO3− and DON leaching by 88% and 90%, respectively. Water percolation was positively correlated with N leaching (p < 0.001). (4) Straw application only reduced NO3− leaching losses in the first year and did not affect DON leaching overall, although DON leaching was increased in DIF in the first growing season. In conclusion, DIF significantly reduces NO3− and DON leaching losses by approximately 90% compared with the current farmer practice (CIF). Considering the significant DON leaching losses, which have been overlooked because previous measurements focused on NO3−, DON should be considered as a primary factor of environmental pollution in conventional solar greenhouse vegetable production systems.

Biochar has been widely accepted as a soil amendment to improve nitrogen (N) use efficiency, but the effect of biochar on N transformation metabolic pathways is unclear. A field experiment was conducted to evaluate the effect of biochar on N transformation in drip-irrigated cotton field. Four treatments were set as (1) no N fertilization (CK), (2) N fertilizer application at 300 kg ha⁻¹ (N300), (3) N fertilizer application plus cotton straw (N300+ST), and (4) N fertilizer application plus cotton straw–derived biochar (N300+BC). Result showed that soil total N in N300+ST and N300+BC was 16.3% and 24.9% higher than that in N300, respectively. Compared with N300+ST, the nitrate N (NO₃⁻-N) in N300+BC was significantly increased. Acidolyzable N and non-acidolyzable N in N300+ST and N300+BC were higher than those in CK and N300, while N300+BC performed better than N300+ST. Furthermore, the N fertilizer use efficiency of cotton in N300+ST and N300+BC was 15.1% and 23.2% higher than that in N300, respectively. Both N fertilizer incorporations with straw and biochar significantly altered the microbial community structures and N metabolic pathways. Genes related to denitrification and nitrate reduction in N300+ST were higher than those in N300, and N300+BC significantly increased nitrification and glutamate synthesis genes. Therefore, N fertilizer application plus cotton straw–derived biochar changed the microbial community composition, increased nitrification and glutamate synthesis enzyme genes which were beneficial to the accumulation of soil N content, and improved soil N retention capacity thus to increase N fertilizer use efficiency.

Drip irrigation is of prime importance from several points of view as the most effective and reliable method. Nevertheless, emitter clogging is the major problem related to this technology. Furthermore, pressure compensating button emitters are widely used considering their advantages resulting from the uniform distribution of water, reduction of evaporation, and deep percolation. In the present study, we report on four pressures compensating button emitters and their resistance to the clogging. Our research objectives incorporate two aspects; executing a 980-h experiment of drip irrigation by taking into consideration the temperature calibration equation, and evaluating the performance of the emitters by using the following four parameters: the relative average discharge (Dra), coefficient of uniformity (CU), emitter uniformity (EU), and the flow rate variation (qᵥₐᵣ). Thus, analyzing the evaluation of those parameters provides the potential of choosing emitters that have a high resistance to the clogging. The main conclusion of this research effort is that three types of the four emitters display a satisfactory resistance to clogging.

Balancing the nitrogen derived from sewage effluent and fertilizers is essential for efficiently utilizing the nitrogen and minimizing the environmental degradations when applying sewage effluent. Pot experiments of maize (Zea mays L.) under drip irrigation were performed using ¹⁵N labeled urea to quantify the nitrogen balances of sewage effluent and fertilizers. Field experiments were conducted to confirm the findings of pot experiments. Four nitrogen rates ranging from 0 to 2.64 g/pot (0–210 kg/ha equivalently) for pot experiments and from 0 to 180 kg/ha for field experiments were established applying either secondary sewage effluent (SW) or groundwater (GW). Both pot and field experiments revealed that SW irrigation boosted nitrogen uptake and yield of maize compared to GW irrigation. However, the sewage-derived effects decreased with increasing nitrogen rates. SW irrigation could facilitate the uptake of ¹⁵N labeled urea relative to GW irrigation. Nonetheless, the nitrogen containing in effluent possibly had lower uptake effectiveness than the fertilizer urea for maize, suggesting greater potential for nitrogen losses resulting from effluent nitrogen compared to urea nitrogen. The percentage utilization of effluent nitrogen declined from 43 to 34% in 2014 and 48 to 32% in 2015 as nitrogen rates increased from 0 to 2.64 g/pot. Besides, the percentages utilization of total nitrogen (including effluent and fertilizers) under SW irrigation increased from 43 to 55% in 2014 and from 48 to 55% in 2015 when the rates increased from 0 to 1.76 g/pot, and subsequently decreased to 48% in 2014 and 44% in 2015 at the rate of 2.64 g/pot. This result was strengthened by the pattern of nitrogen recovery efficiency observed in the field experiments. Overall results of pot and field experiments recommended an optimal rate of 120 kg/ha for maize under drip irrigation applying SW to maximize nitrogen use efficiency and achieve an acceptably high yield.

Negative pressure irrigation (NPI) is a new water supply technology that can save water and improve fertilizer utilization efficiency. The objective of this study was to determine the effects of different irrigation treatments on the yield and quality of rapeseed, nitrate distribution in soil, and the composition of rhizosphere bacterial communities in a greenhouse. During the entire rapeseed growth period, NPI reduced water consumption by 23 and 23% compared to that reduced by conventional irrigation (CI) and drip irrigation (DI), and NPI improved water use efficiency (WUE) by 67 and 59% more than CI and DI, respectively. Under NPI, the soil water content remained relatively stable within the range of 9.7–11.7%, which was a lower range of variation than that under CI and DI of 8.6–13.3%. NPI significantly improved the yield, quality, and plant nutrients of rapeseed. The NO₃-N content was always lowest at the different sampling times and soil layers under the NPI-L treatment. NPI significantly increased the microbial diversity in the rhizosphere soil of rapeseed and increased the abundance of Actinobacteria while decreasing that of Proteobacteria and Acidobacteria. Simultaneously, the performance of rapeseed was better under the NPI-L fertilizer concentration (0.15%) than under NPI-H (0.20%). Eventually, the combination of the evaluated regimes demonstrated that NPI is the best irrigation technique for saving water and obtaining relatively high rapeseed yields and quality while improving nitrogen utilization and the composition of rhizosphere bacterial communities. The results of this study provide a scientific basis for planting rapeseed in agricultural facilities.

Biosolid, i.e., dehydrated sludge from effluent treatment stations, has been progressively used as an agricultural fertilizer due to its high organic matter and nutrient contents. Elephant grass (Cenchrus purpureus (Schumach.) Morrone) presents easy adaptation and high yields, being used for animal feeding and for energy purposes. The objective of this work was to analyze the production and bromatological parameters of elephant grass with four different doses of biosolid, one of chemical fertilizer and a control plot, with two replicates each. A field experiment was carried out using a randomized block design with three blocks, totaling 18 plots, which received biosolid fertilization at 1×, 2×, 4×, and 8× the levels recommended by the Brazilian National Environment Council, along with conventional chemical fertilization and no fertilization, all under similar drip irrigation. Tukey’s test indicated a significant difference at p < 0.01 for total production in the first cut and acid detergent fiber in the second cut. At p < 0.05, significant differences were detected for total nitrogen and total protein in the first cut. The elephant grass yield under “1× biosolid” was similar to that reached with chemical fertilization. Physical and bromatological characteristics indicated potential use as animal feed and energy source. For doses higher than specified by Brazilian standards (2×, 4×, and 8×), further studies are required to verify possible contamination from heavy metals, pathogenic microorganisms, and n.

Ammonia (NH₃) volatilization is one of the main pathways of N loss from farmland soil. Saline water irrigation can have direct or indirect effects on soil NH₃ volatilization, N leaching, and crop N uptake. This study was conducted to evaluate the effects of irrigation water salinity and urea-N application rate on NH₃ volatilization and N use efficiency in a drip-irrigated cotton field. The experiment consisted of three levels of irrigation water salinity: fresh water, brackish water, and saline water (electrical conductivities of 0.35, 4.61, and 8.04 dS/m, respectively). The N application rates were 0, 240, 360, and 480 kg/ha. The results showed that soil salinity and soil moisture content were significantly higher in the saline water treatment than in either the fresh or brackish water treatments. Irrigation water salinity significantly increased soil NH₄-N concentration, but NO₃-N concentration decreased as water salinity increased. The amount of N leaching varied from 5.0 to 25.5 kg/ha, accounting for 1.81 to 4.79 % of the urea-N applied under different water salinity and N application rate treatments. Both the amount of N leaching and the proportions of applied N lost through leaching significantly increased as water salinity increased. N application increased the amounts of N leaching, but the ratios of applied N were not affected by N application rate. Soil NH₃ volatilization increased rapidly after urea fertigation, and peaked at 1–2 days after N application, then decreased rapidly. The amount of NH₃ volatilization varied from 9.0 to 33.7 kg/ha, accounting for 3.2 to 3.8 % of the N applied in all treatments. Soil NH₃ volatilization was significantly higher in the saline water treatment than that in either the fresh or the brackish water treatments. Cotton N uptake increased significantly as N application rate increased, but decreased with irrigation water salinity increased. In conclusion, saline water irrigation with high N application rate induced high N leaching and NH₃ volatilization losses, thereby dramatically reducing the apparent N recovery (ANR) of cotton.

Inorganic N fertilizer and irrigation water types on the C and N dynamics are poorly understood. This work aimed to evaluate the effect of different N fertilizer and irrigation water types on soil C and N mineralization. The farmland experiment was conducted with three types of N fertilizer (urea, ammonium sulfate, and slow-release urea) and drip irrigation with two types of water (groundwater and reclaimed water) for a summer maize-winter wheat crop rotation. Soil samples were collected from the experimental farmland for incubation experiments. The results showed that the average cumulative mineralization of soil C (incubation 20 days) and N (incubation 14 weeks) in different treatments ranged from 73.50 to 91.37 mg kg⁻¹ and 52.65 to 64.04 mg kg⁻¹, respectively. N fertilization significantly increased dissolved organic carbon (DOC), dissolved organic nitrogen (DON), soil organic carbon (SOC), and soil organic nitrogen (SON) contents in the soils, but N fertilizer and irrigation water types had no significant influence on them. Correspondingly, N fertilization significantly enhanced the mineralization of C by 14.14–21.22 % and N by 15.81–22.16 % in soils but no significant difference among different N fertilizer types. Compared with groundwater, reclaimed water irrigation enhanced the mineralization of C by 3.33 % and N by 1.01 %, but the difference was not statistically significant. The cumulative mineralization of C and N in soils after DOM removal average significantly decreased 9.83 and 14.83 %, respectively, which indicates that DOM plays an important role in soil C and N mineralization. Our results indicate that inorganic N fertilization promotes soil C and N mineralization, which may inevitably aggravate global warning. Reclaimed water irrigation had similar influence on soil C and N mineralization as groundwater irrigation; thus, we recommend irrigation with reclaimed water in water shortage areas.

The present study aimed to look at the fate of protozoan parasite Cryptosporidium parvum oocysts applied through surface drip irrigation on reclaimed water irrigation-history and non-history sandy-loam (Hamra) soil columns. A new and simple isolation method for recovery of oocysts from soil samples was developed and used along this study. The new soil isolation method of oocysts is based on the “two phase separation method” formerly used to recover Clostridium perfringens spores from sediments and soil samples with minor modifications. The range recovery achieved by this method was 64-95% (mean 61.2 ± 17.4). The objectives of the second part of this study were to investigate several physical and chemical factors governing transport and survival of C. parvum oocysts in sandy-loam soil columns by breakthrough curves. Comparison of fresh water and reclaimed water irrigation revealed that reclaimed water irrigated-history soil was more hydrophobic allowing water flow through channels with poor oocysts retention and fast flow. Examination of the organic matter effect (originating from reclaimed water irrigation) on oocysts breakthrough revealed that their soil infiltration increased. Calculations of oocysts concentration at different columns depths showed that most of the oocysts were retained in the first 5 cm of soil column. In the present study, comparing the two soil types (history and non-history of effluents irrigation) beside the surface electrostatic charge, one of the main elements found to affect oocysts infiltration and transport in soil columns was soil hydrophobicity caused by soluble organic matter originating from reclaimed water irrigation. Therefore, prior to application in soil irrigation, reclaimed water should be treated to high quality (i.e. membrane technology as the best option) to prevent enhanced transport of various pathogens through those irrigated soils.