Nitrogen nutrition in cotton and control strategies for greenhouse gas emissions: a review

Unveiling novel insights into haloarchaea (Halolamina pelagica CDK2) for alleviation of drought stress in wheat

Plant growth promoting microorganisms have various implications for plant growth and drought stress alleviation; however, the roles of archaea have not been explored in detail. Herein, present study was aimed for elucidating potential of haloarchaea (Halolamina pelagica CDK2) on plant growth under drought stress. Results showed that haloarchaea inoculated wheat plants exhibited significant improvement in total chlorophyll (100%) and relative water content (30.66%) compared to the uninoculated water-stressed control (30% FC). The total root length (2.20-fold), projected area (1.60-fold), surface area (1.52-fold), number of root tips (3.03-fold), number of forks (2.76-fold) and number of links (1.45-fold) were significantly higher in the inoculated plants than in the uninoculated water stressed control. Additionally, the haloarchaea inoculation resulted in increased sugar (1.50-fold), protein (2.40-fold) and activity of antioxidant enzymes such as superoxide dismutase (1.93- fold), ascorbate peroxidase (1.58-fold), catalase (2.30-fold), peroxidase (1.77-fold) and glutathione reductase (4.70-fold), while reducing the accumulation of proline (46.45%), glycine betaine (35.36%), lipid peroxidation (50%), peroxide and superoxide radicals in wheat leaves under water stress. Furthermore, the inoculation of haloarchaea significantly enhanced the expression of stress-responsive genes (DHN, DREB, L15, and TaABA-8OH) and wheat vegetative growth under drought stress over the uninoculated water stressed control. These results provide novel insights into the plant-archaea interaction for plant growth and stress tolerance in wheat and pave the way for future research in this area.

Genetic and Morpho-Physiological Differences among Transgenic and No-Transgenic Cotton Cultivars

Three carbon-chain extension genes associated with fatty acid synthesis in upland cotton (Gossypium hirsutum), namely GhKAR, GhHAD, and GhENR, play important roles in oil accumulation in cotton seeds. In the present study, these three genes were cloned and characterized. The expression patterns of GhKAR, GhHAD, and GhENR in the high seed oil content cultivars 10H1014 and 10H1041 differed somewhat compared with those of 10H1007 and 2074B with low seed oil content at different stages of seed development. GhKAR showed all three cultivars showed higher transcript levels than that of 2074B at 10-, 40-, and 45-days post anthesis (DPA). The expression pattern of GhHAD showed a lower transcript level than that of 2074B at both 10 and 30 DPA but a higher transcript level than that of 2074B at 40 DPA. GhENR showed a lower transcript level than that of 2074B at both 15 and 30 DPA. The highest transcript levels of GhKAR and GhENR were detected at 15 DPA in 10H1007, 10H1014, and 10H1041 compared with 2074B. From 5 to 45 DPA cotton seed, the oil content accumulated continuously in the developing seed. Oil accumulation reached a peak between 40 DPA and 45 DPA and slightly decreased in mature seed. In addition, GhKAR and GhENR showed different expression patterns in fiber and ovule development processes, in which they showed high expression levels at 20 DPA during the fiber elongation stage, but their expression level peaked at 15 DPA during ovule development processes. These two genes showed the lowest expression levels at the late seed maturation stage, while GhHAD showed a peak of 10 DPA in fiber development. Compared to 2074B, the oil contents of GhKAR and GhENR overexpression lines increased 1.05~1.08 folds. These results indicated that GhHAD, GhENR, and GhKAR were involved in both seed oil synthesis and fiber elongation with dual biological functions in cotton.

Utilizing waste compost to improve the atmospheric CO2 capturing in the rice-wheat cropping system and energy-cum‑carbon credit auditing for a circular economy

The study aimed to manage industrial wastes and create a module for using compost from waste for crops cultivation to conserve energy, reduce fertilizer use and Greenhouse gas (GHG) emissions, and improve the atmospheric CO2 capturing in agriculture for a green economy. In the main-plot, the experiment's results using NS3 found 50.1 and 41.8 % more grain yield and total carbon dioxide (CO2) sequestration in the wheat-rice cropping sequence, respectively, compared to the NS0. Moreover, the treatment CW + TV in the sub-plot observed 24.0 and 20.3 % higher grain yield and total CO2 sequestration than B + PS. Based on interaction, the NS3× CW + TV resulted in a maximum total CO2 sequestration and C credit of 47.5 Mg ha-1 and US$ 1899 ha-1, respectively. Further, it was 27.9 % lower in carbon footprints (CFs) than NS1 × B + PS. Regarding another parameter, the treatment NS3 observed a 42.4 % more total energy output in the main-plot than that of NS0. Further, in the sub-plot, the treatment CW + TV produced 21.3 % more total energy output than B + PS. Energy use efficiency (EUE) and net energy return in the interaction of NS3× CW + TV were 20.5 and 138.8 % greater than the NS0 × B + PS, respectively. In the main-plot, the treatment NS3 obtained a maximum of 585.0 MJ US$-1 and US$ 0.24 MJ-1 for energy intensity in economic terms (EIET) and eco-efficiency index in terms of energy (EEIe), respectively. While in the sub-plot, the CW + TV was observed at a maximum of 571.52 MJ US$-1 and US$ 0.23 MJ-1 EIET and EEIe, respectively. The correlation and regression study showed a perfect positive correlation between grain yield and total C output. Moreover, a high positive correlation (0.75 to 1) was found with all other energy parameters for grain energy use efficiency (GEUE). The variability in the wheat-rice cropping sequence's energy profitability (EPr) was 53.7 % for human energy profitability (HEP). Based on principal component analysis (PCA), the eigenvalues of the first two principal components (PCs) had been greater than two, explaining 78.4 and 13.7 % of the variability. The experiment hypothesis was to develop a reliable technology for safely using industrial waste compost, minimizing energy consumption and CO2 emissions by reducing chemical fertilizer input in agriculture soils.

Long-term nitrogen fertilizer management for enhancing use efficiency and sustainable cotton (Gossypium hirsutum L.)

Optimal management of nitrogen fertilizer profoundly impacts sustainable development by influencing nitrogen use efficiency (NUE) and seed cotton yield. However, the effect of long-term gradient nitrogen application on the sandy loam soil is unclear. Therefore, we conducted an 8-year field study (2014-2021) using six nitrogen levels: 0 kg/hm2 (N0), 75 kg/hm2 (N1), 150 kg/hm2 (N2), 225 kg/hm2 (N3), 300 kg/hm2 (N4), and 375 kg/hm2 (N5). The experiment showed that 1) Although nitrogen application had insignificantly affected basic soil fertility, the soil total nitrogen (STN) content had decreased by 5.71%-19.67%, 6.67%-16.98%, and 13.64%-21.74% at 0-cm-20-cm, 20-cm-40-cm, and 40-cm-60-cm soil layers, respectively. 2) The reproductive organs of N3 plants showed the highest nitrogen accumulation and dry matter accumulation in both years. Increasing the nitrogen application rate gradually decreased the dry matter allocation ratio to the reproductive organs. 3) The boll number per unit area of N3 was the largest among all treatments in both years. On sandy loam, the most optional nitrogen rate was 190 kg/hm2-270 kg/hm2 for high seed cotton yield with minimal nitrogen loss and reduced soil environment pollution.

Reducing carbon footprints and increasing net ecosystem economic benefits through dense planting with less nitrogen in double-cropping rice systems

Excessive application of nitrogen fertilization in farmland systems can cause nitrogen wastage, environmental pollution, and increase greenhouse gas (GHG) emissions. Dense planting is one of the efficient strategies for nitrogen fertilizer reduction within rice production. However, there are paying weak attention to the integrative effect of dense planting with less nitrogen (DPLN) on carbon footprint (CF), net ecosystem economic benefit (NEEB) and its components in double-cropping rice systems. Herein, this work aims to elucidate the effect via field experiments in double-cropping rice cultivation region with the treatments set to conventional cultivation (CK), three treatments of DPLN (DR1, 14 % nitrogen reduction and 40,000 hills per ha density increase from CK; DR2, 28 % nitrogen reduction and 80,000 hills density increase; DR3, 42 % nitrogen reduction and 120,000 hills density increase), and one treatment of no nitrogen (N0). Results showed that DPLN significantly reduced average CH4 emissions by 7.56 %-36 %, while increasing annual rice yield by 2.16 %-12.37 % compared to CK. Furthermore, the paddy ecosystem under DPLN served as a carbon sink. Compared with CK, DR3 increased gross primary productivity (GPP) by 16.04 % while decreasing direct GHG emissions by 13.1 %. The highest NEEB was observed in DR3, which was 25.38 % greater than CK and 1.04-fold higher than N0. Therefore, direct GHG emissions and carbon fixation of GPP were key contributors to CF in double-cropping rice systems. Our results verified that optimizing DPLN strategies can effectively increase economic benefits and reduce net GHG emissions. DR3 achieved an optimal synergy between reducing CF and enhancing NEEB in double-cropping rice systems.

Increase in cotton yield through improved leaf physiological functioning under the soil condition of reduced chemical fertilization compensated by the enhanced organic liquid fertilization

Introduction

Low agricultural nutrient input efficiency remains a significant impediment for crop production globally. To address this issue in cotton agroecosystems, there is a need to develop sustainable crop nutrient management strategies to achieve high crop yields. We hypothesized that organic liquid fertilizer (OF) combined with reduced chemical fertilizer (CF) would enhance cotton yield by improving leaf functioning and soil properties. However, the underlying mechanism and its related process is poorly understood.

Methods

This study explored the effects of OF combined with reduced CF on cotton yield, physiology and soil properties. Treatments included a single application of CF (CF: N, P2O5 and K2O applied at 228, 131 and 95 kg ha-1) and combined applications of OF and CF (OF0.6-OF1.4) in the following ratios: OF0.6, OF+60% CF; OF0.8, OF+80% CF; OF1.0, OF+100% CF; OF1.2, OF+120% CF; OF1.4, OF+140% CF.

Results and discussion

The result showed that compared with CF, OF0.8, OF1.0 and OF1.2 increased soil organic matter (SOM) content by 9.9%, 16.3% and 23.7%, respectively. Compared with CF, the OF0.6, OF0.8, OF1.0, and OF1.2 treatments increased leaf area (LA) by 10.6-26.1%, chlorophyll content (Chl content) by 6.8-39.6%, and the efficiency of photosystem II (PSII) light energy (Y(II)), electron transfer rate of PSII (ETR) and photochemical quenching (qP) by 3.6-26.3%, 4.7-15.3% and 4.3-9.8%, respectively. The OF0.8 treatment increased net photosynthetic rate (P n), stomatal conductance (G s) and transpiration rate (E) by 22.0%, 27.4% and 26.8%, respectively, resulting in higher seed cotton yield. The seed cotton yield and economic coefficient were positively correlated with P n, E, G s and Y(II) from the full boll stage to the boll opening stage. In summary, the OF0.8 treatment can maintain a high SOM content and photosynthetic performance with reduced chemical fertilizer input without sacrificing yield. The integration of OF+80% CF (OF0.8) is a promising nutrient management strategy for highly efficient cotton production under mulch drip irrigation systems.

Differential sensitivities of photosynthetic processes and carbon loss mechanisms govern N-induced variation in net carbon assimilation rate for field-grown cotton

Nitrogen (N) deficiency limits the net carbon assimilation rate (AN), but the relative N sensitivities of photosynthetic component processes and carbon loss mechanisms remain relatively unexplored for field-grown cotton. Therefore, the objective of the current study was to define the relative sensitivity of individual physiological processes driving N deficiency-induced declines in AN for field-grown cotton. Among the potential diffusional limitations evaluated, mesophyll conductance was the only parameter substantially reduced by N deficiency, but this did not affect CO2 availability in the chloroplast. A number of metabolic processes were negatively impacted by N deficiency, and these effects were more pronounced at lower leaf positions in the cotton canopy. Ribulose bisphosphate (RuBP) regeneration and carboxylation, AN, and gross photosynthesis were the most sensitive metabolic processes to N deficiency, whereas photosynthetic electron transport processes, electron flux to photorespiration, and dark respiration exhibited intermediate sensitivity to N deficiency. Among thylakoid-specific processes, the quantum yield of PSI end electron acceptor reduction was the most sensitive process to N deficiency. It was concluded that AN is primarily limited by Rubisco carboxylation and RuBP regeneration under N deficiency in field-grown cotton, and the differential N sensitivities of the photosynthetic process and carbon loss mechanisms contributed significantly to photosynthetic declines.

Uptake of nitrogen and nitrogen use efficiency of soil through agrotain coated urea and its integration with farmyard manure

Since the green revolution, excessive utilization of chemical fertilizers has become prevalent due to concerns about the integrity of food production for the growing population. This indiscriminate use harms the fertility of the soil, especially in sandy soils where nutrient leaching, particularly nitrogen, results in yield losses as well as environmental and health problems. A pot experiment was carried out at Gomal University, Pakistan, in March 2022 to assess the nitrogen use efficiency, nitrogen uptake, and yield of okra. There were nine treatments with four replicates and the treatment combinations were established using a completely randomized design (CRD). Urea coated with agrotain (urease inhibitor) was applied each at 120 and 84 kg N ha^-1 in 2 or 3 splits. Urea at 84 kg N ha^-1 was also used in combination with Farmyard manure (FYM) and compared against the control (100% recommended urea). Obtained results showed that inhibitor-treated urea significantly increased soil concentrations of NO₃^-N and NH₄^-N over non-inhibitor-treated urea. The highest NO₃^-N was recorded where urea alone and urea treated with 3 L (3 L) agrotain was applied to 100%. The highest ammonical-N was recorded, where 70% urea treated with 3 L agrotain was applied. Urea, in combination with FYM, significantly increased the organic matter. Electrical conductivity in extract (ECe), and pH of the soil. The improvement in yield with inhibitor was at par with 70% and 100% urea. The highest improvement of 16% in fruit yield and 7.29% nitrogen use efficiency was obtained in the treatment receiving 120 kg N ha^-1 treated with 3 L agrotain compared with non-inhibitor urea. The 2nd highest improvement of 10% in fruit yield on account of increased fruit length, stem diameter, and number of fruits, and 5.97% nitrogen use efficiency (NUE) was obtained in treatment receiving 120 kg N ha^-1 in combination with FYM in comparison to control. These results suggested that the use of N inhibitor significantly increased the okra fruit yield on account of enhancing ammonical-N and increased N use efficiency.

Effects of nitrogen input on soil bacterial community structure and soil nitrogen cycling in the rhizosphere soil of Lycium barbarum L

Lycium barbarum L., goji berry, is a precious traditional Chinese medicine and it is homology of medicine and food. Its growth is heavily dependent on nitrogen. The use of chemical fertilizers has significantly promoted the yield of goji berry and the development of the L. barbarum L. industry. However, crop plants are inefficient in the acquisition and utilization of applied nitrogen, it often leads to excessive application of nitrogen fertilizers by producers, which cause negatively impact to the environment ultimately. The exploration of an interaction model which deals with crops, chemical fertilizers, and rhizosphere microbes to improve nitrogen use efficiency, is, therefore, an important research objective to achieve sustainable development of agriculture greatly. In our study, we explored the effects of nitrogen input on soil microbial community structure, soil nitrogen cycling, and the contents of nutrients in L. barbarum fruits. The structure and composition of the bacterial community in the rhizosphere soil of L. barbarum were significantly different under different nitrogen supply conditions, and high nitrogen addition inhibited the diversity and stability of bacterial communities. Low nitrogen input stimulated the relative abundance of ammonia-oxidizing bacteria (AOB), such as Nitrosospira, catalyzing the first step of the ammonia oxidation process. The results of the GLMM model showed that the level of nitrogen fertilizer (urea) input, the relative abundance of AOB, the relative abundance of Bradyrhizobium, and their combinations had significant effects on the soil nitrogen cycling and contents of nutrients in L. barbarum fruits. Therefore, we believe that moderately reducing the use of urea and other nitrogen fertilizers is more conducive to improving soil nitrogen use efficiency and Goji berry fruit quality by increasing the nitrogen cycling potential of soil microorganisms.

Genome-wide identification and analyses of cotton high-affinity nitrate transporter 2 family genes and their responses to stress

Nitrate transporters (NRTs) are crucial for the uptake, use, and storage of nitrogen by plants. In this study, 42 members of the GhNRT2 (Nitrate Transporter 2 family) were found in the four different cotton species. The conserved domains, phylogenetic relationships, physicochemical properties, subcellular localization, conserved motifs, gene structure, cis-acting elements, and promoter region expression patterns of these 42 members were analyzed. The findings confirmed that members of the NRT2 family behaved typically, and subcellular localization tests confirmed that they were hydrophobic proteins that were mostly located on the cytoplasmic membrane. The NRT2 family of genes with A.thaliana and rice underwent phylogenetic analysis, and the results revealed that GhNRT2 could be divided into three groups. The same taxa also shared similar gene structure and motif distribution. The composition of cis-acting elements suggests that most of the expression of GhNRT2 may be related to plant hormones, abiotic stress, and photoreactions. The GhNRT2 gene was highly expressed, mainly in roots. Drought, salt, and extreme temperature stress showed that GhNRT2 gene expression was significantly up-regulated or down-regulated, indicating that it may be involved in the stress response of cotton. In general, the genes of the NRT2 family of cotton were comprehensively analyzed, and their potential nitrogen uptake and utilization functions in cotton were preliminarily predicted. Additionally, we provide an experimental basis for the adverse stress conditions in which they may function.

Enhancement of nitrogen use efficiency through agronomic and molecular based approaches in cotton

Cotton is a major fiber crop grown worldwide. Nitrogen (N) is an essential nutrient for cotton production and supports efficient crop production. It is a crucial nutrient that is required more than any other. Nitrogen management is a daunting task for plants; thus, various strategies, individually and collectively, have been adopted to improve its efficacy. The negative environmental impacts of excessive N application on cotton production have become harmful to consumers and growers. The 4R's of nutrient stewardship (right product, right rate, right time, and right place) is a newly developed agronomic practice that provides a solid foundation for achieving nitrogen use efficiency (NUE) in cotton production. Cropping systems are equally crucial for increasing production, profitability, environmental growth protection, and sustainability. This concept incorporates the right fertilizer source at the right rate, time, and place. In addition to agronomic practices, molecular approaches are equally important for improving cotton NUE. This could be achieved by increasing the efficacy of metabolic pathways at the cellular, organ, and structural levels and NUE-regulating enzymes and genes. This is a potential method to improve the role of N transporters in plants, resulting in better utilization and remobilization of N in cotton plants. Therefore, we suggest effective methods for accelerating NUE in cotton. This review aims to provide a detailed overview of agronomic and molecular approaches for improving NUE in cotton production, which benefits both the environment and growers.

Organic amendments and conservation tillage improve cotton productivity and soil health indices under arid climate

Long-term different tillage system field trials can provide vital knowledge about sustainable changes in soil health indices and crop productivity. This study examined cotton productivity and soil health indices under different tillage systems and organic materials. The present study was carried out at MNS University of Agriculture, Multan to explore the effect of different tillage systems: conventional tillage (T₁), conservation tillage (T₂), and organic materials: control (recommended dose of synthetic fertilizers; 160:90:60 kg ha^-1NPK), poultry manure (10 t ha^-1 PM), compost (10 t ha^-1 CM), farmyard manure (20 t ha^-1 FYM), and biochar (7 t ha^-1 BC) on cotton productivity and soil health indices. Two years field trials showed that different tillage systems and organic materials significantly improved the growth, morphological, and yield attributes of cotton and soil health indices. The cotton showed highest seed cotton yield (3692-3736 kg ha^-1), and soil organic matter (0.809-0.815%), soil available nitrogen (74.3-74.6 mg kg^-1), phosphorus (7.29-7.43 mg kg^-1), and potassium (213-216 mg kg^-1) under T₂ in comparison to T₁ system during both years of field experiment, respectively. Similarly, PM (10 t ha^-1) showed highest seed cotton yield (3888-3933 kg ha^-1), and soil organic matter (0.794-0.797%), nitrogen (74.7-75.0 mg kg^-1), phosphorus (7.39-7.55 mg kg^-1), and potassium (221-223 mg kg^-1) when these are compared to FYM (20 t ha^-1), CM (10 t ha^-1), and BC (7 t ha^-1) during both years of field experiment, respectively. These findings indicate that conservation tillage system with application of 10 t ha^-1 PM are the best practices for the sustainable cotton production and to ensure improvement in the soil health indices under arid climatic conditions.

Thiamine functions as a key activator for modulating plant health and broad-spectrum tolerance in cotton

Global climate changes cause an increase of abiotic and biotic stresses that tremendously threaten the world's crop security. However, studies on broad-spectrum response pathways involved in biotic and abiotic stresses are relatively rare. Here, by comparing the time-dependent transcriptional changes and co-expression analysis of cotton (Gossypium hirsutum) root tissues under abiotic and biotic stress conditions, we discovered the common stress-responsive genes and stress metabolism pathways under different stresses, which included the circadian rhythm, thiamine and galactose metabolism, carotenoid, phenylpropanoid, flavonoid, and zeatin biosynthesis, and the mitogen-activated protein kinase signaling pathway. We found that thiamine metabolism was an important intersection between abiotic and biotic stresses; the key thiamine synthesis genes, GhTHIC and GhTHI1, were highly induced at the early stage of stresses. We confirmed that thiamine was crucial and necessary for cotton growth and development, and its deficiency could be recovered by exogenous thiamine supplement. Furthermore, we revealed that exogenous thiamine enhanced stress tolerance in cotton via increasing calcium signal transduction and activating downstream stress-responsive genes. Overall, our studies demonstrated that thiamine played a crucial role in the tradeoff between plant health and stress resistance. The thiamine deficiency caused by stresses could transiently induce upregulation of thiamine biosynthetic genes in vivo, while it could be totally salvaged by exogenous thiamine application, which could significantly improve cotton broad-spectrum stress tolerance and enhance plant growth and development.

The impact of pristine and modified rice straw biochar on the emission of greenhouse gases from a red acidic soil

With the growing awareness of environmental impacts of land degradation, pressure is mounting to improve the health and productivity of degrading soils, which could be achieved through the use of raw and modified biochar materials. The primary objective of the current study was to investigate the efficiency of pristine and Mg-modified rice-straw biochar (RBC and MRBC) for the reduction of greenhouse gases (GHG) emissions and improvement of soil properties. A 90 days' incubation experiment was conducted using treatments which included control (CK), two RBC dosages (1% and 2.5%), and two MRBC doses (1% and 2.5%). Soil physico-chemical and biological properties were monitored to assess the effects due to the treatments. Results showed that both biochars improved soil physicochemical properties as the rate of biochar increased. The higher rates of biochar (RBC_2.5 and MRBC_2.5) particularly increased enzymatic activities (Catalase, Invertase and Urease) in comparison to the control. Data obtained for phospholipid fatty acid (PLFA) concentration indicated an increase in the Gram-negative bacteria (G-), actinomycetes and total PLFA with the increased biochar rate, while Gram-positive bacteria (G+) showed no changes to either level of biochar. As regards fungi concentration, it decreased with the biochar addition, whereas arbuscular mycorrhizal fungi (AMF) showed non-significant changes. The release of CO₂, CH₄ and N₂O showed a decreasing trend over the time. CO₂ cumulative emission decreased for MRBC₁ (5%) and MRBC_2.5 (9%) over the pristine biochar treatments. The cumulative N₂O emission decreased by 15-32% for RBC₁ and RBC_2.5 and by 22-33% for MRBC₁ and MRBC_2.5 as compared to the control, whereas CH₄ emission showed non-significant changes. Overall, the present study provides for the first-time data that could facilitate the correct use of Mg-modified rice biochar as a soil additive for the mitigation of greenhouse gas emission and improvement of soil properties.

Impact of Plant Spacing and Nitrogen Rates on Growth Characteristics and Yield Attributes of Egyptian Cotton (Gossypium barbadense L.)

This current study was performed to determine the influences of plant spacing, Nitrogen (N) fertilization rate and their effect, on growth traits, yield, and yield components of cotton (Gossypium barbadense L.) cv. Giza 97 during the 2019 and 2020 seasons. A split plot experiment in three replicates was utilized whereas the cotton seeds were planted at 20, 30, and 40 cm, as main plots and nitrogen at 75, 100, and 125%, was in subplots. The results revealed that the planting spacing at 40 cm significantly (p ≤ 0.01) increased plant height, number of fruiting branches per plant, number of bolls per plant, boll weight (BW), lint percentage (L%), seed cotton yield (SCY), lint cotton yield (LCY), seed index and lint index by 165.68 cm, 20.92, 23.93, 3.75 g, 42.01%, 4.24 ton/ha, 5.16 ton/ha, 12.05, 7.86, respectively, as average in both seasons. The application of N fertilizer rate at 125% caused a maximum increase in growth and yield parameters i.e., plant height (169.08 cm), number of vegetative branches (2.67), number of fruiting branches per plant (20.82), number bolls per fruiting branch (1.39), number of bolls per plant (23.73), boll weight (4.1 g), lint percent (41.9%), seed index (11.8 g), and lint index (8.2), while the plants treated with 100% N rates exhibited highest seed cotton yield (4.3 ton/ha) and lint cotton yield (5.6 ton/ha), as average in both seasons. Combining plant spacing at 40 cm between plants with a 100% N fertilizer rate recorded the highest lint cotton yield (5.67 ton/ha), while the highest seed cotton yield (4.43 and 4.50 ton/ha) was obtained from 125% N fertilizer rate under planting spacing 20 and 40 cm, respectively. Conclusively, a wide density (40 cm) with 125% N is a promising option for improved biomass, cotton growth, yield, physiological traits, and fiber quality.

Development of an Automated Linear Move Fertigation System for Cotton Using Active Remote Sensing

Optimum nitrogen (N) application is essential to the economic and environmental sustainability of cotton production. Variable-rate N fertigation could potentially help farmers optimize N applications, but current overhead irrigation systems normally lack automated site-specific variable-rate fertigation capabilities. The objective of this study was to develop an automated variable-rate N fertigation based on real-time Normalized Difference Vegetation Index (NDVI) measurements from crop sensors integrated with a lateral move irrigation system. For this purpose, NDVI crop sensors and a flow meter integrated with Arduino microcontrollers were constructed on a linear move fertigation system at the Edisto Research and Education Center in Blackville, South Carolina. A computer program was developed to automatically apply site-specific variable N rates based on real-time NDVI sensor data. The system’s ability to use the NDVI data to prescribe N rates, the flow meter to monitor the flow of N, and a rotary encoder to establish the lateral’s position were evaluated. Results from this study showed that the system could accurately use NDVI data to calculate N rates when compared to hand calculated N rates using a two-sample t-test (p > 0.05). Linear regression analysis showed a strong relationship between flow rates measured using the flow meter and hand calculations (R2 = 0.95), as well as the measured distance travelled using the encoder and the actual distance travelled (R2 = 0.99). This study concludes that N management decisions can be automated using NDVI data from on-the-go handheld GreenSeeker crop sensors. The developed system can provide an alternative N application solution for farmers and researchers.

Greenhouse gas emissions and mitigation potential of hybrid maize seed production in northwestern China

Although hybrid maize seed production is one of the most important agriculture systems worldwide, its greenhouse gas (GHG) emissions and potential mitigation measures have not been studied. In this study, we used life cycle assessment (LCA) to quantify the GHG emissions of 150 farmers run by 6 companies in an area of northwest China known for hybrid maize seed production. The results indicated that the average reactive nitrogen (Nr) losses and GHG emissions from hybrid maize seed production were 53 kg N ha^-1 and 8077 kg CO₂ eq ha^-1, respectively. Furthermore, the average nitrogen and carbon footprints of the process were 12.2 kg N Mg^-1 and 1495 kg CO₂ eq Mg^-1, respectively. Nitrogen fertilizer and electricity consumption for irrigation were the main contributors to high GHG emissions, accounting for 60% and 30% of the total, respectively. The GHG emissions from seed production for different companies varied greatly with their resource input. There was also a large variation in environmental burdens among the 150 farmers. Based on an analysis of the yield group, we found that the carbon footprint of the first group (the one with the highest yield) was 27% lower than the overall average. Scenario analysis suggests that a combined reduction of N input rate, optimizing irrigation, and increasing yield can eventually mitigate the carbon footprint of hybrid maize seed production by 37%. An integrated systematic approach (e.g., ISSM: integrated soil-crop system management) can reduce the GHG emissions involved in producing hybrid maize seeds. This study provides quantitative evidence and a potential strategy for GHG emissions reduction of hybrid maize seed production.

Biochar and slow-releasing nitrogen fertilizers improved growth, nitrogen use, yield, and fiber quality of cotton under arid climatic conditions

The efficiency of nitrogenous fertilizers in South Asia is on a declining trajectory due to increased losses. Biochar (BC) and slow-releasing nitrogen fertilizers (SRNF) have been found to improve nitrogen use efficiency (NUE) in certain cases. However, field-scale studies to explore the potential of BC and SRNF in south Asian arid climate are lacking. Here we conducted a field experiment in the arid environment to demonstrate the response of BC and SRNF on cotton growth and yield quality. The treatments were comprised of two factors, (A) nitrogen sources, (i) simple urea, (ii)neem-coated urea, (iii)sulfur-coated urea, (iv) bacterial coated urea, and cotton stalks biochar impregnated with simple urea, and (B) nitrogen application rates, N₁=160 kg ha^-1, N₂ = 120 kg ha^-1, and N₃ = 80 kg ha^-1. Different SRNF differentially affected cotton growth, morphological and physiological attributes, and seed cotton yield (SCY). The bacterial coated urea at the highest rate of N application (160 kg ha^-1) resulted in a higher net leaf photosynthetic rate (32.8 μmol m^-2 s^-1), leaf transpiration rate (8.10 mmol s^-1), and stomatal conductance (0.502 mol m^-2 s^-1), while leaf area index (LAI), crop growth rate (CGR), and seed cotton yield (4513 kg ha^-1) were increased by bacterial coated urea at 120 kg ha^-1 than simple urea. However, low rate N application (80 kg ha^-1) of bacterial coated urea showed higher nitrogen use efficiency (39.6 kg SCY kg^-1 N). The fiber quality (fiber length, fiber strength, ginning outturn, fiber index, and seed index) was also increased with the high N application rates than N2 and N3 application. To summarize, the bacterial coated urea with recommended N (160 kg ha^-1) and 75% of recommended N application (120 kg ha^-1) may be recommended for farmers in the arid climatic conditions of Punjab to enhance the seed cotton yield, thereby reducing nitrogen losses.

Nitrogen use efficiency in cotton: Challenges and opportunities against environmental constraints

Nitrogen is a vital nutrient for agricultural, and a defieciency of it causes stagnate cotton growth and yield penalty. Farmers rely heavily on N over-application to boost cotton output, which can result in decreased lint yield, quality, and N use efficiency (NUE). Therefore, improving NUE in cotton is most crucial for reducing environmental nitrate pollution and increasing farm profitability. Well-defined management practices, such as the type of sources, N-rate, application time, application method, crop growth stages, and genotypes, have a notable impact on NUE. Different N formulations, such as slow and controlled released fertilizers, have been shown to improve N uptake and, NUE. Increasing N rates are said to boost cotton yield, although high rates may potentially impair the yield depending on the soil and environmental conditions. This study comprehensively reviews various factors including agronomic and environmental constraints that influence N uptake, transport, accumulation, and ultimately NUE in cotton. Furthermore, we explore several agronomic and molecular approaches to enhance efficiency for better N uptake and utilization in cotton. Finally, this objective of this review to highlight a comprehensive view on enhancement of NUE in cotton and could be useful for understanding the physiological, biochemical and molecular mechanism of N in cotton.

Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture

Plant growth-promoting bacteria (PGPB) and humic substances (HSs) are promising options for reducing the use of pesticides and mineral fertilizers. Although many studies have shown the effects of PGPB and HSs separately, little information is available on plant responses to the combined application of these biostimulants despite the great potential for the simultaneous action of these biological inputs. Thus, the objective of this review is to present an overview of scientific studies that addressed the application of PGPB and HSs to different crops. First, we discuss the effect of these biostimulants on biological nitrogen fixation, the various effects of the inoculation of beneficial bacteria combined with the application of HSs on promoting the growth of nonleguminous plants and how this combination can increase bacterial colonization of plant hosts. We also address the effect of PGPB and HSs on plant responses to abiotic stresses, in addition to discussing the role of HSs in protecting plants against pathogens. There is a lack of studies that address the role of PGPB + HSs in biocontrol. Understanding the factors involved in the promotion of plant growth through the application of PGPB and HSs can assist in the development of efficient biostimulants for agricultural management. This approach has the potential to accelerate the transition from conventional cultivation to sustainable agrosystems.

Using GIS tools to detect the land use/land cover changes during forty years in Lodhran District of Pakistan

Land use/land cover (LULC) change has serious implications for environment as LULC is directly related to land degradation over a period of time and results in many changes in the environment. Monitoring the locations and distributions of LULC changes is important for establishing links between regulatory actions, policy decisions, and subsequent LULC activities. The normalized difference vegetation index (NDVI) has the potential ability to identify the vegetation features of various eco-regions and provides valuable information as a remote sensing tool in studying vegetation phenology cycles. Similarly, the normalized difference built-up index (NDBI) may be used for quoting built-up land. This study aims to detect the pattern of LULC, NDBI, and NDVI change in Lodhran district, Pakistan, from the Landsat images taken over 40 years, considering four major LULC types as follows: water bodies, built-up area, bare soil, and vegetation. Supervised classification was applied to detect LULC changes observed over Lodhran district as it explains the maximum likelihood algorithm in software ERDAS imagine 15. Most farmers (46.6%) perceived that there have been extreme changes of onset of temperature, planting season, and less precipitation amount in Lodhran district in the last few years. In 2017, building areas increased (4.3%) as compared to 1977. NDVI values for Lodhran district were highest in 1977 (up to + 0.86) and lowest in 1997 (up to - 0.33). Overall accuracy for classification was 86% for 1977, 85% for 1987, 86% for 1997, 88% for 2007, and 95% for 2017. LULC change with soil types, temperature, and NDVI, NDBI, and slope classes was common in the study area, and the conversions of bare soil into vegetation area and built-up area were major changes in the past 40 years in Lodhran district. Lodhran district faces rising temperatures, less irrigation water, and low rainfall. Farmers are aware of these climatic changes and are adapting strategies to cope with the effects but require support from government.

Developing the first halophytic turfgrasses for the urban landscape from native Arabian desert grass

Climate change is occurring and is influencing biological systems through augmented temperatures, more inconstant precipitation, and rising CO₂ in the atmosphere. For sustainable landscaping, it was essential to assess the diversity of native/wild grasses and their suitability for turf and to combat the salinity problem in the region. For this purpose, a native halophytic grass, Aeluropus lagopoides, was investigated by conducting mowing tests on its ecotypes during the year 2014-2016 under desert climatic conditions. The research was carried out in two phases, i.e. Phase-I was for collection and establishment of ecotypes from various parts of UAE, while in Phase-II, mowing tests were conducted. During mowing tests, 50 ecotypes of A. lagopoides were given various mowing treatments (i.e. they were cut back at 1-, 2-, 3-, 4- and 5-cm heights) in field conditions. Significant differences were found among various ecotypes for different agronomic parameters such as ground cover, canopy stiffness, leaf number, clippings fresh and dry weights and internode length. Overall, the grass exhibited better performance at mowing heights of 3 and 4 cm, which are the standard mowing heights for turfgrasses. Ecotypes FA5, RA3, RUDA2, RUDA7 and RUADA1 of A. lagopoides showed the best performance against mowing shock and became the candidates for the turfgrass varieties from the native Arabian flora.

Spatial and temporal variations of the greenhouse gas emissions in coastal saline wetlands in southeastern China

Coastal wetlands are crucial to global climate change due to their roles in modulating atmospheric concentrations of greenhouse gases (GHGs) (CO₂, CH₄, N₂O). Under a warming climate, we investigated spatial and temporal variations of GHGs emissions over the coastal wetlands in southeastern China during 2012-2014. Five dominant land cover types in coastal wetlands have been considered, including the bare mud flat (BF), the Spartina alterniflora flats (SAF), the Suaeda glauca flats (SGF), the Phragmites australis flat (PAF), and the Scripus triqueter flat (STF). The results showed that the annual average CO₂ fluxes were 305.8, 588.8, 370.2, and 136.5 mg m^-2 h^-1 from spring to winter. CH₄ fluxes presented to be a sink in spring (- 0.02 mg m^-2 h^-1), and functioned as a source in the following seasons. Correlation analysis indicated that the surface air temperature and the cumulative precipitation could be two main factors that influenced the seasonal and inter-annual variations of GHGs emissions. In addition, we provided a regional budget of GHGs emissions that suggested the variations of GHGs emissions under a warming climate.

Mammalian cell cultivation using nutrients extracted from microalgae

Mammalian cells have been used in various research fields. More recently, cultured cells have been used as the cell source of "cultured meat." Cell cultivation requires media containing nutrients, of which glucose and amino acids are the essential ones. These nutrients are generally derived from grains or heterotrophic microorganisms, which also require various nutrients derived from grains. Grain culture, in turn, requires many chemical fertilizers and agrochemicals, which can cause greenhouse gas emission and environmental contamination. Furthermore, grain production is greatly influenced by environmental changes. In contrast, microalgae efficiently synthesize various nutrients using solar energy, water, and inorganic substances, which are widely used in the energy sector. In this study, we aimed to apply nutrients extracted from microalgae in the culture media for mammalian cell cultivation. Glucose was efficiently extracted from Chlorococcum littorale or Arthrospira platensis using sulfuric acid, whereas 18 of the 20 proteinogenic amino acids were efficiently extracted from Chlorella vulgaris using hydrochloric acid. We further investigated whether nutrients present in the algal extracts could be used in mammalian cell cultivation. Although almost all C2C12 mouse myoblasts died during cultivation in a glucose- and amino acid-free medium, the cell death was rescued by adding algal extract(s) into the nutrient-deficient media. This indicates that nutrients present in algal extracts can be used for mammalian cell cultivation. This study is the first step toward the establishment of a new cell culture system that can reduce environmental loads and remain unaffected by the impact of environmental changes.

Reducing the carbon footprint per unit of economic benefit is a new method to accomplish low-carbon agriculture. A case study: adjustment of the planting structure in Zhangbei County, China

BACKGROUND

The development of low-carbon agriculture is promising for mitigating climate change. This study used adjustments to the planting structure in Zhangbei County, China, as an example to evaluate whether the carbon footprint per unit of economic benefit is a suitable indicator of low-carbon agriculture and to determine if low-carbon agriculture is not necessarily low-input non-intensive agriculture.

RESULTS

The results showed that total greenhouse gas emissions increased; therefore, the adjustments to the planting structure were ostensibly not a low-carbon process. However, if we obtain the same economic benefit as the actual distribution of the planting industry by adopting the scenario of planting only grain crops, then the annual greenhouse gas emissions would be 1608.00 × 10³  t CO₂ eq, and 5769.94 × 10³  ha of farmland would be required. However, if we adopt the scenario of planting only vegetable crops, then only 82.52 × 10³  ha of farmland would be required, and the annual greenhouse gas emissions would be 323.52 × 10³  t CO₂ eq.

CONCLUSIONS

These results indicated that the carbon footprint per unit of economic benefit is a suitable indicator to assess agricultural sustainability and that intensive agriculture with high input and high output is a form of low-carbon agriculture if the carbon footprint per unit of economic benefit is low. © 2019 Society of Chemical Industry.

Trends of electronic waste pollution and its impact on the global environment and ecosystem

Electronic waste (e-waste) is used for all electronic/electrical devices which are no more used. Conventionally, waste management policies are desfighandle the traditional waste. Although e-waste contains toxic materials, however, its management is rarely focused by policy makers; therefore, its negative impact on the global environment, ecosystem, and human health is aggravated. The review outlines the categories of e-waste materials, major pollutants including ferrous/non-ferrous metals, plastics, glass, printed circuit boards, cement, ceramic, and rubber beside, some valuable metals (such as copper, silver, gold, platinum). Toxic elements from e-waste materials, released in the air, water, and soil, include arsenic, cadmium, chromium, mercury, and lead, causing pollution. Although their roles in biological systems are poorly identified, however, they possess significant toxic and carcinogenic potential. It is therefore critical to monitor footprint and device strategies to address e-waste-linked issues from manufacturing, exportation, to ultimate dumping, including technology transmissions for its recycling. This review traces a plausible link among e-waste condition at a worldwide dimension, as far as settlement procedures to keep it secure and carefully monitored when traded. Their fate in the three spheres of the earth, i.e., water, soil, and air, impacts human health. The strategies and regulation to handle e-waste generation at the global level have been discussed. Graphical abstract .

Performance of Aeluropus lagopoides (mangrove grass) ecotypes, a potential turfgrass, under high saline conditions

Climate change has become a real threat, and its impacts are being felt throughout the world. Temperature is considered one of the significant elements by the recent consequences of climate change and global warming, specially the salinity which is increased at higher temperature. Turfgrasses are adversely affected due to an increasing trend in salinity. The main aim of this investigation was to find out salt-tolerant ecotypes from native species of UAE to mitigate the salinity problem. Performance of a native grass, Aeluropus lagopoides, was investigated under high saline conditions during the year 2014 under the UAE climatic conditions. The experiment was planned under randomised complete block design (RCBD) with two factors and four replications. During the experiment, 50 ecotypes of Aeluropus lagopoides, alongside Paspalum vaginatum (as control), were tested at different salt levels, i.e. 0, 15, 30, 45, 60 and 75 dSm^-1. Significant differences were found among various ecotypes as well as salinity levels for different agronomic traits including green cover, canopy stiffness, leaf colour and salinity of leaf rinseates. Most of the ecotypes tolerated salinity up to 30 dSm^-1, maintaining the quality, but beyond this level the quality declined. However, some of the ecotypes survived under high salinity, even beyond sea level (75 dSm^-1). All the ecotypes, except RUA2, RUA3 and RUA1, showed better performance than P. vaginatum, the prevailing commercial turfgrass in the UAE. Based on their performance, the ecotypes RUDA7, FA5, RA3, RUDA2 and RA2 could be used for turf purposes under saline conditions.