Nitrogen Management Research Articles

Applying Different Organic Amendments Optimizes Soil Nitrogen Management and Increases Greenhouse Tomato Yield

Applying Different Organic Amendments Optimizes Soil Nitrogen Management and Increases Greenhouse Tomato Yield

Characteristics and key driving factors of nitrous oxide emissions from a full-scale landfill leachate treatment system

The characteristics of N2O emission from a full-scale landfill leachate treatment system were investigated by in-situ monitoring over 1.4 years and driving factors responsible for these emissions were identified by statistical analysis of multidimensional environmental variables. The results showed that the maximum N2O emission flux of 2.21 × 107 mg N·h−1 occurred in the nitrification tanks, where 98.5 % of the total N2O was released, with only 1.5 % of the total N2O emitted from the denitrification tanks. Limited oxygen in nitrification tank was responsible for N2O hotspot. The N2O emissions from the parallel lines A and B (both comprising the primary biochemical system) accounted for 52.6 % and 46.6 %, respectively, while the secondary biochemical system contributed only 0.8 % to the total emissions. Higher nitrite concentration in line A and lower nitrogen loading in the secondary biochemical system caused these discrepancies. We found that during the steady state of leachate treatment, intensive N2O emissions of 253.4–1270.5 kg N·d−1 were measured. The corresponding N2O emission factor (EF) ranged from 8.86 to 49.6 %, much higher than those of municipal wastewater treatment. But N2O EF was inconceivably as low as 0.42 % averagely after system maintenance. Influent with low salinity was the key reason, followed by the high MLSS and varying microbial community after maintenance. The dominant genus shifted from Lentimicrobium and Thauera to Norank-F-Anaerolineaceae and Unclassified-F-Rhodocyclaceae. This study underscores the significance of landfill leachate treatment in urban nitrogen management and provides valuable insights into the characteristics and driving factors of N2O emissions from such systems. The findings offer important references for greenhouse gas emission inventories and strategies for N2O control in full-scale wastewater treatment plants.

Improving prediction accuracy of CSM-CERES-Wheat model for water and nitrogen response using a modified Penman-Monteith equation in a semi-arid region

Context or problemThe implementation of crop models for water and nitrogen management are important in preserving water resources and reducing groundwater pollution. The Decision Support System for Agrotechnology Transfer (DSSAT) is a collection of field-scale process-based crop models that simulate crop growth and yield in response to water and nitrogen management as well as many other factors. Objective or research questionThe objective of this study was to improve the simulation of irrigation and nitrogen fertilizer effects on growth and yield of winter wheat using locally modified Penman-Monteith (PM) equation. Specifically, we focused on improving the estimation of ETo using a locally modified Penman-Monteith (PM) equation in the CSM-CERES-Wheat model. MethodsField measured data from a two-year experiment (2009–2010 and 2010–2011) in a semi-arid region were used to calibrate and evaluate the CSM-CERES-Wheat model in a region with strong advective condition. In this experiment, the irrigation treatments were 1.2, 1.0, 0.8, 0.5 times by full irrigation requirements and rain-fed, and nitrogen treatments were 0, 46, 92, and 136 kg N ha−1. ResultsUsing the CSM-CERES-Wheat model with the unmodified PM equation resulted in some growth variables such as: aboveground dry matter, grain yield, and grain nitrogen uptake with high normalized root mean square error (NRMSE) of 0.51, 0.35, and 0.32, respectively. However, using the modified PM equation for ETo module under semi-arid condition improved the soil water content estimation and the model outputs, such as the above ground dry matter, grain yield and grain nitrogen uptake with NRMSE of 0.2, 0.15 and 0.16, respectively, that are accurate. This modification provided more accurate estimations, particularly in our experimental site in semi-aid region with strong advective conditions. ConclusionsThe findings of this study indicated that the locally modified PM equation in the CSM-CERES-Wheat model enhanced the accuracy of estimating irrigation and nitrogen fertilizer on the growth and yield of winter wheat. By improving the estimation of ETo value, the model's performance in simulating crop responses to water and nitrogen management was significantly enhanced. Implications or significanceThe utilization of the accurately estimated ETo value of the modified PM equation has significant importance in the practical application of the CSM-CERES-Wheat model. Furthermore, this modification greatly enhances the accuracy of model outputs, particularly at our experimental site located in a semi-arid region with robust advective conditions.

Impact of diverse tillage and nitrogen management on growth and yield of conservation agriculture-based wheat (Triticum aestivum)

A study was carried out during the winter (rabi) seasons of 2020–21 and 2021–22 at ICAR-Indian Agricultural Research Institute, New Delhi to assess the effects of diverse tillage and nitrogen management scenarios on growth, development, and yield of a conservation agriculture (CA)-based wheat (Triticum aestivum L.) crop grown in sequence with maize (Zea mays L.). Experiment was conducted in split plot design (SPD) comprised of 3 different tillage practices in main plots [Conventional tillage + residue (CT); Zero tillage + residue (ZT); and Permanent beds + residue (PB)] and 5 nitrogen (N) options in sub plots [Control (zero nitrogen); Recommended dose of N-RDN @150 kg N/ha (50 kg N/ha Basal + 2-equal splits at 37 days after sowing (DAS) and 84 DAS); Green Seeker (GS) based application of N @148 kg N/ha (GS); Urea super granules applied as basal @75 kg N/ha + GS based N application (USG); and Slow release fertilizer as 100% basal application @150 kg N/ha (SRF)] with 3-replications. The findings revealed that in both the seasons, both tillage and nitrogen management approaches significantly affected wheat growth, yield characteristics, and overall yield, whereas the time to anthesis and physiological maturity, and test weight remained unaffected. Within the spectrum of tillage practices, leaf area index (LAI) and yield attributes exhibited the trend PB>ZT>CT. PB recorded the highest grain yield (5159 kg/ha), followed by ZT (4916 kg/ha) and the lowest grain yield was observed with CT (4578 kg/ha). The wheat grain yields were 12.7% and 7.4% higher in PB and ZT, respectively, over to CT. Among nitrogen management options, the grain yield exhibited the pattern USG>N150>SRF>GS>N0. This study emphasizes that adopting conservation agriculture (CA) practices, particularly CA-based permanent beds using urea super granules (USG) for nitrogen management can improve wheat growth and yield.

Metabolic coupling between soil aerobic methanotrophs and denitrifiers in rice paddy fields

Paddy fields are hotspots of microbial denitrification, which is typically linked to the oxidation of electron donors such as methane (CH4) under anoxic and hypoxic conditions. While several anaerobic methanotrophs can facilitate denitrification intracellularly, whether and how aerobic CH4 oxidation couples with denitrification in hypoxic paddy fields remains virtually unknown. Here we combine a ~3300 km field study across main rice-producing areas of China and 13CH4-DNA-stable isotope probing (SIP) experiments to investigate the role of soil aerobic CH4 oxidation in supporting denitrification. Our results reveal positive relationships between CH4 oxidation and denitrification activities and genes across various climatic regions. Microcosm experiments confirm that CH4 and methanotroph addition promote gene expression involved in denitrification and increase nitrous oxide emissions. Moreover, 13CH4-DNA-SIP analyses identify over 70 phylotypes harboring genes associated with denitrification and assimilating 13C, which are mostly belonged to Rubrivivax, Magnetospirillum, and Bradyrhizobium. Combined analyses of 13C-metagenome-assembled genomes and 13C-metabolomics highlight the importance of intermediates such as acetate, propionate and lactate, released during aerobic CH4 oxidation, for the coupling of CH4 oxidation with denitrification. Our work identifies key microbial taxa and pathways driving coupled aerobic CH4 oxidation and denitrification, with important implications for nitrogen management and greenhouse gas regulation in agroecosystems.

Different Management of Nitrogen Application Affected Growth Characteristic of Maize (Zea mays L)

A field study was conducted during Kharif 2019-20 at Professor Jayashankar Telangana State Agricultural University (PJTSAU), Rajendranagar, Hyderabad, Telangana, India to evaluate different handheld decision support tools for precision nitrogen management in rainfed maize (Zea mays L.). The study utilized a randomized block design and was replicated three times. The eight treatments included applying nitrogen through the State-recommended dose of 200 kg ha-1 in three splits (RDN), using a leaf color chart (LCC) based on N at thresholds 3 and 4, using a soil plant analysis development (SPAD) chlorophyll meter based on N at thresholds 35 and 40, and using a Green Seeker based on N at NDVI 0.6 and 0.8 in comparison with RDN and absolute control. Based on Green Seeker NDVI at threshold 0.8, the results showed that applying nitrogen resulted in considerably greater yields for maize grain (8408 kg ha-1), stover (9923 kg ha-1), and harvest index (45.8%). with higher yield and growth parameter viz., test weight (36.3 g ), No. of grain rows row-1 (36.7), cob length (18.9 cm), plant height (223.7 cm), leaf area (6385.75 cm2) and dry matter accumulation (18193 kg ha-1) as compared to RDN. Similarly, Green Seeker based N at NDVI 0.8 also registered higher net returns (Rs. 118961 ha-1) and B: C ratio (4.05).

Long‐term 4R nitrogen management in dryland wheat–fallow systems

AbstractSeveral short‐term studies have investigated 4R (right source, rate, time, and place) N management for dryland wheat (Triticum aestivum L.) production and profitability, but few long‐term studies exist in the United States or abroad. This study evaluated long‐term impacts of several aspects of 4R N management on dryland hard red wheat yield, protein, and return to N. Experiments were conducted at Nephi and Blue Creek, UT, during 1995–2007. Fourteen N treatments evaluated performance of starter fertilizer, fall applications of anhydrous ammonia (AA) with and without nitrapyrin (AA‐Nitrapyrin and AA, respectively), and several split applications in the fall and spring. Across years, winter wheat required N to increase yield, protein, and returns at both sites. Applying 56 kg N ha−1 as AA in the fall usually produced the best return to N compared to other N treatments. Starter N (6 kg N ha−1) at fall planting rarely increased yield, protein, or returns at either site. Across both sites, nitrapyrin increased mean annual yield by 0.6 Mg ha−1 and mean return to N by $150 ha−1. Spring application of N was rarely required and only increased yield in 13% of the years. Results indicate that nitrapryin is often needed with fall AA applications to optimize yield and returns and that starter N or extra N in the spring are rarely economical in dryland wheat in Utah and possibly the greater Intermountain West. Further, N rate had the most influence among 4Rs on wheat production and should be the focus of future efforts to improve 4R stewardship.

Reducing livestock quantities to avoid manure nitrogen surplus: would meat self-sufficiency be met in eastern regions of China?

In building a sustainable food system, the management of livestock production should avoid nitrogen (N) surplus and ensure animal-sourced food self-sufficiency. Reducing livestock quantities in regions producing excess of animal-sourced food and livestock manure is an effective approach for mitigating manure N surplus. In this study, we considered the eastern regions of China as a case study to quantitatively analyze whether meat self-sufficiency could be met when reducing the livestock quantity to avoid manure N surplus. In addition to considering the baseline scenario, considering the current livestock quantity (scenario C), we defined three strategies corresponding to livestock reduction scenarios: taking meat self-sufficiency as a priority regardless of the manure balance (scenario TB); taking manure N surplus avoidance as a priority regardless of the meat balance (scenario MNB); and considering the most limiting conditions between satisfying meat self-sufficiency and avoiding manure N surplus (scenario LF). A balance index was used to describe the excess (i.e., positive value) or deficiency (i.e., negative value) of meat and manure N. Concerning the whole of eastern China, in scenario LF, the meat balance index (TBI) and manure N balance index (MNBI) were 0.25 and −0.39, respectively, which could satisfy meat demand while avoid manure N surplus (for scenarios C, TB, and MNB, the TBIs were 1.95, 0, and 1.09, and the MNBIs were 0.56, −0.48, and 0, respectively). At the regional level, the regions with meat self-sufficiency accounted for more than 70% in the LF scenario, and manure N surplus could be avoided in all regions. However, southwestern China should adopt further measures, such as trading among adjacent regions and increasing manure fertilizer application, to satisfy the meat demand while avoiding surplus manure N.

Agro-technologies for greenhouse gases mitigation in flooded rice fields for promoting climate smart agriculture

We investigated methane (CH4) and nitrous oxide (N2O), two important greenhouse gases (GHGs) emissions using the closed chamber method from a flooded rice field in Brahmaputra valley of Assam, northeast part of India. We tried to understand the factors responsible for the emission and identify appropriate agro-technologies for their mitigation. Various factors like water level, drainage management, soil organic carbon management, crop management, fertilizer amendment, cultivar type etc. affect the GHG production and emission from the flooded rice soil. In this study, six treatments were employed, namely, farmer's practice (FP), recommended fertilizer dosage (RDF), direct seeded rice (DSR), intermittent wetting drying (IWD), use of efficient methanotrophs (MTH), and use of ammonium sulfate as a nitrogen source for real-time nitrogen management using leaf color chart, (AS). GHG flux was measured through the static closed chamber technique. Soil temperature, pH, and redox potential (Eh) and other soil physico-chemical and biological properties that have a potential role in GHG emission were also assessed. The lowest CH4 flux was observed in IWD treatment. The highest CH4 but lowest N2O flux was observed in RDF thus portraying a tradeoff relationship among these two GHGs. The highest N2O flux was observed in AS. Changes in Eh strongly altered CH4 and N2O emissions. The CH4 flux for the growing season varied from 62.5 to 86.3 kg ha−1 with an average of 72.4 kg ha−1. The average N2O flux was 0.89 kg ha−1 with values fluctuating between 0.72 – and 1.08 kg ha−1. The findings of this study could assist in understanding the factors affecting the source, production, and sink of these two important GHGs. IWD, along with judicious N-based fertilizer use, could provide significant respite from GHG emissions in rice-based agriculture. These climate-smart strategies not only reduce emissions but also have the potential to improve yield.

Field and simulation studies on yield, water and nitrogen dynamics and use efficiency in rice-wheat crops in sequence

ContextThe dominant rice-wheat cropping system in the Indo-Gangetic plain faces challenges of water depletion and nitrogen pollution of groundwater as well as declining productivity caused by over irrigation and nitrogen fertilization by the farmers. To appreciate the apt use of irrigation water and nitrogen fertilizer in rice and wheat crops it is essential to explore the water and nitrogen balances as well as dynamics in these crops, involving complex interaction between weather, soil, irrigation water and nitrogen fertilizer management. ObjectiveThe objective of the study is to quantify yield, field water balance components, water use efficiency, water productivity, water footprint, and water and nitrogen dynamics of rice and wheat crops in relation to season, varieties, irrigation regimes and nitrogen levels. MethodsField experimentations were conducted in double split plot design along with calibrated and validated HYDRUS 1D model use for two years comprising of treatments in rice i.e. two varieties (PR122-V1 and PR126-V2), two irrigation regimes (2-days drainage period-I1 and soil water suction 16 kPa-I2) and two nitrogen levels (120-N1 and 90-N2 kg N ha−1); and in wheat, two varieties (Unnat PBW343-V1 and Unnat PBW550-V2), two irrigation (1.2 IW/CPE-I1 and 0.9 IW/CPE-I2) regimes and two nitrogen levels (120-N1 and 90-N2 kg N ha−1). ResultsThe highest grain yield recorded was 7.6 t ha−1 in treatment combination of V1I2N1 in rice and 5.4 t ha−1 in V1I1N1 in wheat owing to better plant growth and yield attributes (biomass production, number of effective tillers, panicle length, and 1000 grain weight). Total water footprints were lower in the treatment combination of V1I1N1 in rice and V1I2N1 in wheat. The water budget revealed a higher percent contribution of the total water input to drainage (62 %) in rice ensuing restoration of water in the soil profile; and to evapotranspiration (ET) (100 %) in wheat ensuing water depletion. Modeling water and nitrogen dynamics showed higher root water uptake in I2 treatment in rice and with I1 treatment in wheat; and leaching losses of NO3-N under rice than wheat; and under I2 treatment than I1 as well as in N1 than N2. ConclusionsThe V1I2N1 treatment in rice and V1I1N1 treatment in wheat demonstrated superior grain yield, soil water storage, and root water uptake. Conversely, V1I1N1 treatment in rice and V1I2N1 treatment in wheat showed higher water use efficiency and lower water footprint. SignificanceIt helps to evaluate the effectiveness of irrigation and nitrogen management strategies in maximizing crop productivity while minimizing environmental impacts.

Effects of Water and Nitrogen Control on the Growth Physiology, Yields, and Economic Benefits of Lycium barbarum Plants in a Lycium barbarum + Alfalfa System.

In the production of economic forests, there are common issues such as excessive application of water and fertilizer, redundant plant growth, and low economic benefits. Reasonable water and fertilizer management can not only help address these problems but also improve the absorption and use efficiency of water and fertilizer resources by plants, promoting the green and efficient development of the fruit and forestry industry. In order to explore a suitable water and nitrogen management mode for Lycium barbarum, field experiments were conducted in this study from 2021 to 2022. Specifically, four irrigation modes (according to the proportion ratio of soil moisture content to field moisture capacity θf, 45-55% θf (W1, severe water deficiency), 55-65% θf (W2, moderate water deficiency), 65-75% θf (W3, mild water deficiency), and 75-85% θf (W4, sufficient irrigation)) and four nitrogen application levels (0 kg·ha-1 (N0, no nitrogen application), 150 kg·ha-1 (N1, low nitrogen application level), 300 kg·ha-1 (N2, medium nitrogen application level), and 450 kg·ha-1 (N3, high nitrogen application level)) were set up to analyze the influences of water and nitrogen control on the plant height, stem diameter, chlorophyll content, photosynthetic characteristics and yield, and economic benefits of Lycium barbarum in the Lycium barbarum + Alfalfa system. The study results show that the plant height and stem diameter increment of Lycium barbarum increase with the irrigation amount, increasing first and then decreasing with the increase in the nitrogen application level. Meanwhile, the chlorophyll contents in Lycium barbarum continuously increase throughout their growth periods, with Lycium barbarum treated with W4N2 during all growth periods presenting the highest contents of chlorophyll. In a Lycium barbarum + Alfalfa system, the daily variation curve of the Lycium barbarum net photosynthetic rate presents a unimodal pattern, with maximum values of the daily average net photosynthetic rate and daily carboxylation rate appearing among W4N2-treated plants (19.56 μmol·m-2·s-1 and 157.06 mmol·m-2·s-1). Meanwhile, the transpiration rates of Lycium barbarum plants continuously decrease with the increased degree of water deficiency and decreased nitrogen application level. W1N2-treated plants exhibit the highest leaf daily average water use efficiency (3.31 μmol·s-1), presenting an increase of 0.50-10.47% in efficiency compared with plants under other treatments. The coupling of water and nitrogen has significantly improved the yields and economic benefits of Lycium barbarum plants, with W4N2-treated and W3N2-treated plants presenting the highest dried fruit yield (2623.07 kg·ha-1) and net income (50,700 CNY·ha-1), respectively. Furthermore, compared with other treatment methods, these two treatment methods (W4N2 and W3N2) exhibit increases of 4.04-84.08% and 3.89-123.35% in dried fruit yield and net income indexes, respectively. Regression analysis shows that, in a Lycium barbarum + Alfalfa system, both high yields and economic benefits of Lycium barbarum plants can be achieved using an irrigation amount of 4367.33-4415.07 m3·ha-1 and a nitrogen application level of 339.80-367.35 kg·ha-1. This study can provide a reference for improving the productivity of Lycium barbarum plants and achieving a rational supply of water and nitrogen in Lyciun barbarum + Alfalfa systems in the Yellow River Irrigation Area of Gansu, China, and other similar ecological areas.

Residual Effect of Nitrogen and Weed Management Practices in Maize on Succeeding Groundnut

Background: Cereal-legume cropping system is considered to be one of the better alternatives for sustaining soil fertility and increasing the yield. At present maize-groundnut cropping system is gaining importance under both rainfed and irrigated situations. Maize, being an exhaustive and weed-sensitive crop, is supplied with large doses of fertilizers and new herbicide molecules.Since maize is exhaustive and weed sensitive crop, there was a usage of excessive fertilizers and new herbicides. There is a need to assess the carry over effect of fertilizers and new generation herbicides in leguminous crops like groundnut. Methods: The experiment was conducted during two consecutive rabi seasons of 2019-20 and 2020-21 on sandy loam soils of S.V. Agricultural College, Tirupati andhra Pradesh. Maize hybrid DHM -117 was sown and maintained with general cultivation practices except for nitrogen and weed management methods was raised after harvest of maize in undisturbed layout to study the residual effect of different nitrogen and weed management practices imposed in maize. Result: Residual effect of nitrogen and weed management practices imposed in preceding maize did not exert any significant influence on germination percentage, phytotoxicity and SPAD chlorophyll meter reading (SCMR) values but efficacy of herbicide residue found to be significant with weed management practices. Growth parameters, yield attributes pod yield, haulm yield and economics were higher in groundnut with brown manuring, which was however, in parity with hand weeding twice at 15 and 30 DAS, pre emergence application of atrazine 1.0 kg ha-1 fb post emergence application of topramezone 30 g ha-1 and pre emergence application of atrazine 1.0 kg ha-1 fb post emergence application of tembotrione 120 g ha-1 and lower with unweeded check and it was remained in parity with application of parthenium water extract15 lha-1 twice at 15 and 30 DAS, application of sunflower water extract 15 lha-1 twice at 15 and 30 DAS, pre emergence application of atrazine 1.0 kg ha-1 fb post emergence application of parthenium water extract 15 lha-1 and pre emergence application of atrazine 1.0 kg ha-1 fb post emergence application of sunflower water extract 15 lha-1 in the order of ascent. None of their interaction effects were found to be significant during both the years of study and in pooled mean.

Optimization of nitrogen management reduce nitrogen stress and enhance productivity of super-seeder sown wheat under rice residue incorporation

The in-situ management of rice straw incorporation has become an essential practice in the rice–wheat cropping system with the growing adoption of super-seeder among farmers. While this equipment facilitates straw incorporation, nutrient immobilization from organic residues during decomposition poses a challenge to production. This study investigates the effect of bio-decomposer, nitrogen (N) level, and N scheduling on on various parameters in super-seeder sown wheat over two consecutive years (2020–21 and 2021–22). The experiment was laid in split-split-plot design without (B0) and with (B1) bio-decomposer, two nitrogen levels 150 (N1) and 180 (N2) kg ha−1 and three N splits (%) viz., 50: 25:25 (S1), 40: 30: 30 (S2), and 30:35:35 (S3) and replicated thrice. Results indicate significantly higher N concentration and uptake at pre- and post-anthesis with N2 and S1 compared to N1, S2, and S3. Post-anthesis N accumulation (post-NA) and remobilization (NR) were notably higher with N2. Dry matter accumulation (DMA) at anthesis and harvest significantly increased with N2 and S1 compared to N1 and S3, leading to significantly improved grain yield by 8.3% and 10.9% (two years mean). Soil urease activity (UA) significantly increased with bio-decomposer, N2, and S1 compared to B0, N1, and S3 at 30 and 60 DAS. Moreover, bio-decomposer enhanced soil microbial biomass carbon (SMBC). These findings underscore the importance of higher N levels with a greater basal N proportion in mitigating N stress and promoting sustainable wheat productivity. It also highlight the significance of effectively utilizing and conserving rice residue in the rice–wheat system.

Sustainable management strategies for balancing crop yield, water use efficiency and greenhouse gas emissions

CONTEXTTo ensure food security in the face of climate change, it is crucial to use effective agricultural management practices that produce the triangular win-win for water, crops, and environments. OBJECTIVEThis study aimed to explore the sustainable management measures for balancing crop yield, water use efficiency (WUE) and greenhouse gas (GHG) emissions in China during 1981–2020. METHODSThe study selected the Beijing-Tianjin-Hebei (BTH) region of China as the research area, where there were sharp contradictions among water shortage, food security and polluted environment. Four irrigation treatments and four fertilization treatments were set referring to the local cultivated experiences. The daily dynamic changes in crop yield, WUE and GHG emissions were simulated by optimized Agricultural Production Systems sIMulator (APSIM) model. RESULTS AND CONCLUSIONSThe irrigations had positive impacts on crop yield and WUE in BTH region. The irrigation amount's rise caused a gradual augmentation in the total yield of winter wheat and summer maize from 1981 to 2020.The highest total yield was achieved under W4 irrigation treatment (320 mm water for winter wheat and 60 mm water for summer maize), with an annual mean of 24,579.2 kg·ha−1. The annual average WUE under the W3 irrigation treatment (240 mm water for winter wheat) was the highest, with an average of 13.9 kg·ha−1·mm−1. However, extensive fertilization exacerbated soil GHG emissions. The soil GHG emissions were found to be significant increase as the input amount of fertilization. The FI fertilization measure (no fertilization) was assessed to have the least impact on the environment, with an average GHG emissions of 0.4 Mg·CO2-eq·ha−1. The optimal goals of high yield, high WUE and low GHG emissions were achieved by choosing effective combination practices of water and nitrogen management. Overall, the W3 irrigation and F3 fertilization (180 kg/ha fertilizer for winter wheat and 120 kg/ha fertilizer for summer maize.) treatments had the maximum water-fertilizer production indexes in the BTH region. SIGNIFICANCEThis study highlights the importance of agricultural management measures for guaranteeing food security and environmental sustainability at the same time under climate change.

Water and Nitrogen Dynamics in Drip Fertigated Tomato for Water of Different Qualities under Polyhouse Conditions


 Water and NO3-N dynamics in the soil during the growing season is an important tool in improving the nitrogen management and environmental protection. HYDRUS-2D has been widely used to predict the water and NO3-N distribution in the soil. The objective of this study was to simulate the water and NO3-N distribution in the soil under drip fertigated tomato irrigated with different water qualities under polyhouse conditions. Field data were collected on spatial and temporal distribution of water and available NO3-N during growing season. The model was calibrated for the hydraulic conductivity and parameters were used for the validation of the model. The model performance in simulating the water and NO3-N was evaluated by using coefficient of determination (R2), root mean square error (RMSE), index of agreement and Nash–Sutcliffe model efficiency (NSE). For both calibration and validation, the higher values of R2 from 0.70 to 0.99 for water distribution and 0.70 to 0.96 for NO3-N distribution showed that observed and predicted values are highly correlated. The value of RMSE ranges from 0.004 to 0.0016 for water and 0.002-0.006 for NO3-N distribution. The index of agreement value varied from 0.86-0.98 for water distribution and 0.89-0.99 for NO3-N distribution. The values of NSE (nearer to 1) i.e. 0.17 to 0.98 for water distribution and -0.09 to 0.94 for NO3-N distribution show that HYDRUS-2D was predicting with good accuracy. From these results, it can be concluded that the model performs well for predicting the water and NO3-N distribution in the tomato crop irrigated with different water qualities under polyhouse conditions.

Decreasing denitrification rates poses a challenge to further decline of nitrogen concentration in Lake Taihu, China

Nitrogen (N) concentrations in many lakes have decreased substantially in recent years due to external load reduction to mitigate harmful algal blooms. However, little attention has been paid to the linkage between the lakes’ nitrogen removal efficiency and improved water quality in lakes, especially the variation of denitrification rate (DNR) under decreasing N concentrations. To understand the efficiency of N removal under improving water quality and its influence on the N control targets in Lake Taihu, a denitrification model based on in situ experimental results was developed and long-term (from 2007 to 2022) water quality and meteorological observations were used to estimate DNR and relate it to the amount of N removal (ANR) from the lake. The concentration of total nitrogen (TN) in Lake Taihu decreased from 3.28 mg L−1 to 1.41 mg L−1 from 2007 to 2022 but the reduction showed spatial heterogeneity. The annual mean DNR decreased from 45.6 μmol m−2 h−1 to 4.2 μmol m−2 h−1, and ANR decreased from 11.85×103 t yr−1 to 1.17×103 t yr−1 during the study years. N budget analysis suggested that the amount of N removed by denitrification accounted for 23.3 % of the external load in 2007, but decreased to only 4.0 % in 2022. Thus, the contribution of N removal by internal N cycling decreased significantly as water quality improved. Notably, the proportion of ANR in winter to total ANR increased from 14 % in 2007 to 23 % in 2022 due to warming. This could potentially lead to N deficiencies in spring and summer, thus limiting the availability of N to phytoplankton. A TN concentration of less than 1.0 mg L−1 in the lake and 1.5 mg L−1 in the inflowing lake zones in spring contribute to local N-limitation in Lake Taihu for cyanobacteria control. Our study revealed a general pattern that N removal efficiency decreases with improved water quality, which is instructive for eutrophic lakes in nitrogen management.

Conceptual Model of Digital Nitrogen Management in Agricultural Crops

Conceptual Model of Digital Nitrogen Management in Agricultural Crops

Evaluation of N nutrition and optimal fertilizer rate for ridge-furrow mulched maize based on critical N dilution curve under different water conditions

Optimizing nitrogen (N) management based on the critical N dilution curve (NCDC) has been proven a precision fertilization strategy to diagnose crop N nutrition status. However, few explorations have been done to establish a NCDC for dryland maize under double ridge-furrow mulching, a planting system that has been widely adopted in semi-arid areas. Moreover, the influences of various rainfall conditions on NCDC remain unclear. Therefore, a 9-yr field nitrogen fertilization experiment from 2013 to 2021 (five nitrogen rates: 0, 75, 150, 225, and 300 kg N ha–1, respectively, represented by N0, N0.25, N0.50, N0.75, and N1) was applied to established the NCDC under two planting systems (Flatting without mulching, CK; Double ridge-furrow with mulching, DRFM) and two rainfall types (rainfall season and drought season). Compared with CK, DRFM significantly increased plant dry matter (PDM, 5.5–12.8%) and N concentration (4.2–6.9%), ultimately improved grain yield (+16.9%), cumulative nitrogen recovery efficiency (CNRE, +9.8%) and crop water productivity (WPc, +26.3%). Rainfall from jointing to silking stage was an important contributor to grain yield. Compared with rainy season, drought season triggered a 51.7% yield loss and 17.1% reduction in NRE, respectively. The NCDC of the CK and DRFM were Nc=36.6×PDM−0.37 and Nc=38.4×PDM−0.36 in rainy season, respectively; the NCDC of the CK and DRFM were Nc =34.5×PDM−0.27 and Nc=37.3×PDM−0.30 in drought season, respectively. The nitrogen nutrition index (NNI) and plant nitrogen requirement (PNR) based on the NCDC intuitively recorded the N nutritional status. The improved soil micro-environment, PDM and N uptake was recorded in N0.75 (225 kg N ha–1 yr–1) under wet season and in N0.50 (150 kg N ha–1 yr–1) under drought season, respectively, which brought an increase in crop productivity with a suitable N nutrition status. The findings highlight an accurate and effective method for assessing the N nutrition status of rainfed maize, and optimize fertilization strategy for sustainable production in semi-arid regions.

Severe nitrogen leaching and marked decline of nitrogen cycle-related genes during the cultivation of apple orchard on barren mountain

Limited available lands have led to the widespread practice of establishing orchards on barren mountains to expand apple cultivation in China. However, improper nitrogen (N) management strategies in intensive orchards escalate costs and also contribute to environmental contamination. A long-term field experiment was conducted in a representative apple-producing area in Shandong Province, China, to assess the environmental risks associated with newly established orchards. This research utilized lysimeters and soil metagenomic sequencing to investigate N leaching loss and the functional microbial profiles associated with the N cycle during apple cultivation on barren mountains. Five treatments were implemented: no inorganic N fertilizer, traditional farmer's fertilization, drip irrigation with a water-soluble fertilizer, resin-coated urea, and grass interplanting. Among treatments involving inorganic N, the total N leaching rate ranged from 16.5% to 30.7% of the total N fertilizer input. Notably, in treatments with equivalent N fertilizer applications, the water-soluble fertilizer treatment exhibited the highest N leaching loss rate -(20.2–29.0%), while the grass interplanting and resin-coated urea treatments showed significantly lower rates of N leaching loss (17.0–24.9% and 15.2–24.5%, respectively). The abundance of N cycle-related genes experienced a marked decline (17.1–18.8%) during the cultivation of orchards on barren mountains. The water-soluble fertilizer treatment displayed the highest potential for nitrification, contributing to elevated N leaching. Both resin-coated urea and traditional farmer's fertilization treatments exhibited the highest abundance of genes associated with N2O emission risk to the atmosphere. However, the grass interplanting treatment, while effectively reducing N leaching, also triggered the most pronounced soil acidification. Spearman correlation analysis revealed that the decline in pH, coupled with an increase in soil NO3--N concentration and electrical conductivity (EC), were the primary factors contributing to the reduction in the abundance of key N cycle functions. In summary, excessive use of inorganic N fertilizer in orchard environments led to increased N leaching, altered soil physicochemical properties, and significant impacts on N cycle-related genes. The elevated ionic strength in soils might be responsible for both the high N leaching loss and the decrease in N cycle function abundance. In intensive orchard cultivation, each N fertilization strategy mentioned above comes with its environmental drawbacks. Further investigation is warranted to achieve a balance between productivity and environmental protection.

Nitrogen Management for Optimum Potato Yields and Low Environmental Impact in Northwest China

Nitrogen Management for Optimum Potato Yields and Low Environmental Impact in Northwest China