Carbon footprint of synthetic nitrogen under staple crops: A first cradle-to-grave analysis.

More than half of the world's population is nourished by crops fertilized with synthetic nitrogen (N) fertilizers. However, N fertilization is a major source of anthropogenic emissions, augmenting the carbon footprint (CF). To date, no global quantification of the CF induced by N fertilization of the main grain crops has been performed, and quantifications at the national scale have neglected the CO2 assimilated by plants. A first cradle-to-grave life cycle assessment was performed to quantify the CF of the N fertilizers' production, transportation, and application to the field and the uses of the produced biomass in livestock feed and human food, as well as biofuel production. We quantified the direct and indirect inventories emitted or sequestered by N fertilization of main grain crops: wheat, maize, and rice. Grain food produced with N fertilization had a net CF of 7.4 Gt CO2eq. in 2019 after excluding the assimilated C in plant biomass, which accounted for a quarter of the total CF. The cradle (fertilizer production and transportation), gate (fertilizer application, and soil and plant systems), and grave (feed, food, biofuel, and losses) stages contributed to the CF by 2%, 11%, and 87%, respectively. Although Asia was the top grain producer, North America contributed 38% of the CF due to the greatest CF of the grave stage (2.5 Gt CO2eq.). The CF of grain crops will increase to 21.2 Gt CO2eq. in 2100, driven by the rise in N fertilization to meet the growing food demand without actions to stop the decline in N use efficiency. To meet the targets of climate change, we introduced an ambitious mitigation strategy, including the improvement of N agronomic efficiency (6% average target for the three crops) and manufacturing technology, reducing food losses, and global conversion to healthy diets, whereby the CF can be reduced to 5.6 Gt CO2eq. in 2100.

Optimizing maize yields using growth stimulants under the strategy of replacing chemicals with biological fertilizers.

Partial replacement of chemicals with biological fertilizers is a recommended strategy to reduce the adverse environmental effects of chemical fertilizer losses. Enhancing the reduced mineral with biological fertilizers strategy by foliar application of humic acid (HA) and amino acids (AA) can reduce environmental hazards, while improving maize (Zea mays L.) production under semiarid conditions. The recommended doses of N, P and K (e.g., 286 kg N ha-1, 75 kg P2O5 ha-1 and 67 kg K2O ha-1) were applied as the first fertilization level (100% NPK) and were replaced with biofertilizers by 100%, 75%, 50% and 25% as levels of reducing mineral fertilization. These treatments were applied under four foliar applications of tap water (TW), HA, AA and a mixture of HA and AA. Our results reported significant reductions in all parameters, including maize ear yield attributes and grain nutrient uptake, when replacing the mineral NPK with biofertilizers by 25-100% replacement. However, these reductions were mitigated significantly under the application of growth stimulants in the descending order: HA and AA mixture>AA>HA>TA. Applying a mixture of HA and AA with 75% NPK + biofertilizers increased ear length, grain yield, grain uptake of N and K, and crude protein yield by 37, 3, 4, 11 and 7%, respectively as compared with 100% mineral fertilizer only. Moreover, all investigated parameters were maximized under the application of 75% NPK + biofertilizers combined with AA or the mixture of HA and AA, which reveals the importance of growth stimulants in enhancing the reduced chemical NPK strategy. It could be concluded that the mineral NPK rate can be reduced by 25% with biofertilization without any yield losses when combined with HA and AA under arid and semi-arid conditions. That achieves the dual goals of sustainable agriculture by improving yield, while reducing environmental adverse effects.

Maintaining higher grain production with less reactive nitrogen losses in China: A meta-analysis study.

Managing reactive nitrogen (Nr) in agricultural production is crucial for addressing the triple challenges of food security, climate change and environmental degradation. Intensive work has been conducted to investigate the effects of mitigation strategies on reducing Nr losses by ammonia emission (Nr-NH3), nitrous oxide emission (Nr-N2O) and nitrate leaching (Nr-NO3-) separately. This meta-analysis evaluated the efficiency of each strategy in mitigating Nr losses coupled with grain yield responses. The results indicate that producing one Megagram (Mg) of wheat grains caused higher Nr losses, twice that of rice and 17% that of maize. The Nr-NH3 and Nr-NO3- were the dominant sources of Nr losses of the three crops (96%), while Nr-NH3 only presented 86% of the total Nr losses for rice. Reducing the N rate strategy decreased the yield by 33% and the Nr losses by 62% compared with the conventional rate (150-250 kg N ha-1) as an average of the three crops. In contrast, increasing the N rate higher than 250 kg N ha-1 amplified the yield by 15% but also caused a 71% increase in Nr losses compared with the conventional rate. Although subsurface application decreased Nr losses by 5%, this study rejected this approach as an effective strategy due to a 4% yield decline on average of the grain crops. Slow-release fertilizers decreased Nr-NH3 and Nr-N2O losses by 41-58% and 54-89%, respectively, of the highest losses under urea in the three crops, but also led to yield reductions. Organic amendments achieved the highest drop in Nr-NO3- loss by 66% in maize coupled with yield declines. Biochar increased wheat and maize yields by 0.3 and 0.1 Mg, respectively, coupled with 1 kg reduction in Nr losses. On average, inhibitors augmented the grain yields by 0.2 Mg ha-1 for each 1 kg decline in Nr losses. In conclusion, for sustainable agricultural intensification, biochar (for wheat only) and inhibitors (for the three crops) are strongly recommended as mitigation strategies for Nr losses from grain crop production systems in China.

Coupling the environmental impacts of reactive nitrogen losses and yield responses of staple crops in China.

Cropland reactive nitrogen losses (Nr) are of the greatest challenges facing sustainable agricultural intensification to meet the increases in food demand. The environmental impacts of Nr losses and their yield responses to the mitigation strategies were not completely evaluated. We assessed the environmental impacts of Nr losses in China and coupled the efficiency of mitigation actions with yield responses. Datasets about Nr losses in China were collected, converted into potentials of acidification (AP), global warming (GWP), and aquatic eutrophication (AEP), and analyzed by a meta-analysis program. Results showed that producing 1 Mg of rice grains had the highest AP (153 kg acid equiv.), while wheat had the highest GWP and AEP (74 kg CO2 equiv. and 0.37 kg PO4 equiv., respectively). Using the conventional rates (averagely, 200, 230, and 215 kg N ha-1) of urea as a surface application to produce 131.4, 257.2, and 212.1 Tg of wheat, maize, and rice resulted in 17-33 Tg, 7-10 Tg, and 6-87 Gg of AP, GWP, and AEP, respectively. For their balanced effect on reducing AP, GWP, and AEP while maximizing yields, inhibitors, and subsurface application could be set as the best mitigation strategies in wheat production. Inhibitors usage and biochar are strongly recommended strategies for sustainable production of maize. None of the investigated strategies had a balanced effect on rice yield and the environment, thus new mitigation technologies should be developed.

Application of neural network and time series modeling to study the suitability of drain water quality for irrigation: a case study from Egypt.

Limited water resources are one of the major challenges facing Egypt during the current stage. The agricultural drainage water is an important water resource which can be reused for agriculture. Thus, the current study aims to assess the quality of drainage water for irrigation purpose through monitoring and predicting its suitability for irrigation. The chemical composition of Bahr El-Baqr water drain, especially salinity, as well as ions are mainly involved in calculating indicators of water suitability for irrigation, i.e., Ca2+, Mg2+, Na+, K+, HCO-3, Cl-, and SO42-. Further analysis was carried out to evaluate the irrigation water quality index (IWQI) through integrated approaches and artificial neural network (ANN) model. Further, ARIMA models were developed to forecast IWQI of Bahr El-Baqr drain in Egypt. The results indicated that the computed IWQI values ranged between 46 and 81. Around 11% of the samples were classified as excellent water, while 89% of the samples were categorized as good water. The results of IWQI showed a standard deviation of 8.59 with a mean of 62.25, indicating that IWQI varied by 13.79% from the average. ANN model showed much higher prediction accuracy in IWQI modeling with R2 value greater than 0.98 during training, testing and validation. A relatively good correlation was obtained, between the actual and forecasted IWQI based on the Akaike information criterion (AIC); the best fit models were ARIMA (1,0) (0,0) without seasonality. The determination coefficient (R2) of ARIMA models was 0.23. Accordingly, 23% of IWQI variability could be explained by different model parameters. These findings will support the water resources managers and decision-makers to manage the irrigation water resources that can be implemented in the future.

Integrative application of licorice root extract or lipoic acid with fulvic acid improves wheat production and defenses under salt stress conditions.

Although different plant extracts and plant growth regulators are used as biostimulants to support plants grown under salt stress conditions, little information is available regarding the use of licorice root extract (LRE) or lipoic acid (LA) as biostimulants. Studies on the application of LRE or LA in combination with fulvic acid (FA) as natural biostimulants have not been performed. Therefore, in this study, two pot experiments were conducted to evaluate the potential effects of LRE (5 g L-1) or LA (0.1 mM) supplemented as a foliar spray in combination with FA (0.2 mg kg-1 soil) on osmoprotectants and antioxidants, growth characteristics, photosynthetic pigments, nutrient uptake, and yield as well as on the anatomical features of the stems and leaves of wheat plants irrigated with three levels of saline water (0.70, 7.8, and 14.6 dSm-1). Moderate (7.8 dSm-1) and high (14.6 dSm-1) levels of salinity caused a significant (p ≤ 0.05) increase in the activities of SOD, APX CAT, POX, and GR as well as in electrolyte leakage, malondialdehyde level, and reactive oxygen species (O2‒ and H2O2) levels compared to those in controls (plants irrigated with tap water). However, the leaf relative water content, membrane stability index, NPK uptake, leaf area, plant height, spike length, straw yield, grain yield, and protein content of wheat grains significantly (p ≤ 0.05) decreased. Addition of LRE or LA and/or HA to wheat plants under saline stress significantly (p ≤ 0.05) enhanced their morphological and physio-biochemical characteristics in parallel with increases in the activities of enzymatic antioxidants. Salinity stress altered (p ≤ 0.05) wheat stem and leaf structures; however, treatment with LRE + FA significantly improved these negative effects. These findings indicate that FA + LRE treatment significantly improved the antioxidant defense system of the plants, thereby reducing ROS levels and increasing wheat growth and production under saline conditions.

Can secondary metabolites extracted from Moringa seeds suppress ammonia oxidizers to increase nitrogen use efficiency and reduce nitrate contamination in potato tubers?

Nitrification inhibition as an alleviation tool to decrease nitrogen (N) losses and increase N use efficiency (NUE) as well as reducing NO3- accumulation in plants is a promising technology. No study thus far has directly or indirectly to use the secondary metabolites extracted from Moringa (Moringa oleifera Lam) seeds as nitrification inhibitors. Moringa seed extract (MSE) was studied based on its content of phenolic compounds (PC) and for its antioxidant characteristic. A 2-year field experiment and 30-day incubation experiment were conducted with three treatments of control (CK), N fertilizer (300 kg N ha-1 and 200 mg N kg-1 soil for the field and incubation experiment, respectively), and N fertilizer with MSE (500 ppm as a TPC) to investigate the responses of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to MSE and the consequences for NUE and NO3- accumulation in potato tubers. Total phenolics amount was 144 mg gallic acid equivalent g-1 MSE, while flavonoid contents were 76.6 quercetin equivalent g-1 MSE. MSE showed antioxidant activity that was comparable to the standard antioxidants TBHQ and gallic acid. MSE application with N fertilizer retarded the nitrification process, as indicated by a higher NH4+-N and lower NO3--N content, compared with N fertilizer application alone. NH4+-N content reduced to initial CK level on Day 20 under N fertilizer application alone. However, NH4+-N content decreased to initial control level on Day 30 when MSE was applied. The mechanisms resulted from curbing AOB growth by phenolic compounds (TPC, TF, TAC), leading to a delay in nitrification process. AOB increased significantly when N fertilizer was applied alone; on the contrary, AOA was not sensitive to N fertilizer (with and without MSE). Increase in NUE from 37.5% to 66.3% in potato plants under MSE application with N fertilizer was also observed compared with N fertilizer application alone. The highest NO3- accumulation (569 mg NO3- kg-1) in tubers was recorded under N fertilizer application without MSE. MSE application significantly decreased NO3- accumulation (92 mg NO3- kg-1) in tubers which is lower than the maximum value of accepting tubers (200 mg NO3- kg-1). The highest average of N uptake, fresh and dry weight, carotenoids, chlorophyll a, chlorophyll b and nitrate reductase activity was recorded when MSE was applied with N fertilizer. Accordingly, using of Moringa extracted secondary metabolites to suppress AOB growth in the soil is a significant strategy to reduce nitrification rate and N loss from soils, and therefore increase NUE as well as reducing NO3- accumulation in potato tubers.

Budgeting nitrogen flows and the food nitrogen footprint of Egypt during the past half century: Challenges and opportunities.

Egypt is the largest nitrogen (N) fertilizer consumer in Africa. However, its nitrogen use efficiency (NUE) is low, and the relationships between both dietary options and the NUE trend with reactive N (Nr) release into the environment in Egypt have not yet been studied. In this study, we estimated the changes in the N budget and NUE in Egypt during the past 56 years (1961-2016). We also calculated particular virtual N factors (the average amount of Nr released to the environment during food production per unit of N consumption) for major food items to estimate their N footprints (NF). The total N input to croplands increased from 136 kg N ha-1 y-1 (1961-1970) to 307 kg N ha-1 y-1 (2010-2016), while the total crop N uptake increased from 101 kg N ha-1 y-1 to 136 kg N ha-1 y-1, indicating a decrease of NUE from 71% (1960s) to 44% during 2010-2016. Gaseous N emissions of NH3, N2O, and NO increased from 97, 5.6, and 8.3 Gg N y-1 to 339, 29, and 39 Gg N y-1. The total per capita food NF increased from 15 kg N capita-1 y-1 (1961-1970) to 26 kg N capita-1 y-1 (2010-2016). There was a change in the average per capita food consumption NF and food production NF from the 1960s (3.2 and 11.3 kg capita-1 y-1) to 2010-2016 (5.9 and 20.3 kg N capita-1 y-1). There is a dire need to increase the NUE and decrease the food NF in Egypt to minimize the negative consequences of Nr on the environment.

Does the application of silicon and Moringa seed extract reduce heavy metals toxicity in potato tubers treated with phosphate fertilizers?

Two field trials were carried out in two successive agricultural seasons to study the possibility of using silicon (Si) and Moringa seed extract (MSE) for reducing heavy metal contamination resulting from phosphate fertilizers addition to potato tubers. A randomized complete block design experiment was performed using three replicates. Various sources of phosphate fertilizers as ordinary super phosphate and rock phosphate were added at rate of 100 kg P ha-1 prior sowing. Silicon was added as potassium silicate (20% SiO2) at rate of 6 L ha-1, and MSE was also added at rate of 150 L ha-1 in three equal doses with the 2nd, 4th, and 6th irrigations during the last 10 min of drip irrigation. Results indicated that the addition of phosphate fertilizers increased fresh tuber yield, dry weight yield, NPK uptake, catalase, peroxidase, superoxide dismutase, and glutathione reductase of potato either alone or combined with silicon and MSE. The accumulation rate of Cu, Cd, and Ni in potato was higher with the single addition of rock phosphate fertilizer compared with single addition of super phosphate fertilizer. The highest reduction (P < 0.05) in heavy metal accumulation in potato leaves and tubers as well as soil was found with MSE treatment plus super phosphate fertilizer. It is recommended to add MSE at a rate of 150 L ha-1 along with fertilizing the potato crop with ordinary super phosphate fertilizer.

Potato tubers contamination with nitrate under the influence of nitrogen fertilizers and spray with molybdenum and salicylic acid.

A field trial was conducted through 2015 and 2016 growing seasons to study the effect of nitrogen fertilizer sources and foliar spray with molybdenum (Mo), salicylic acid (SA) and their combination on tubers yield, some chemical constituents, nutrients uptake, nitrate accumulation and nitrate reductase activity in potato tubers. N source was added at a rate of 350 kg N ha-1in five equal doses as two different forms, the first is urea and the second is ammonium sulfate plus calcium nitrate equally. SA was sprayed with three rates of 0, 75 and 150 mg l-1. Also, Mo as ammonium molybdate was sprayed using three rates 0, 50 and 100 mg l-1Mo. Both treatments of SA and Mo were applied separately as well as with each other, at three successive times 30, 50 and 70 days after planting of potato plants. Results indicated that the addition of 350 kg N ha-1 as ammonium sulfate and calcium nitrate equally caused a significant elevation (P > 0.05) in fresh weight, chlorophyll b, carotenoids, chlorophyll a, nitrate reductase activity, dry weight and NPK uptake by potato tubers compared with the same amount of nitrogen in the form of urea only. All the aforementioned characteristics were improved with increasing concentration of Mo and/or SA. The highest accumulation of nitrate was recorded under the addition of 350 kg N ha-1 as urea alone. The highest average of all the aforementioned characteristics was observed at the treatment of 350 kg N ha-1 as ammonium sulfate and calcium nitrate equally plus spraying with 100 mg l-1Mo and 150 mg l-1 SA. In contrast, this treatment gave the lowest accumulation of nitrates in potato tubers.