Net Water Use Research Articles

Chitosan fabricated biogenic silver nanoparticles (Ch@BSNP) protectively modulate the defense mechanism of tomato during bacterial leaf spot (BLS) disease

Herein, the impact of chitosan fabricated biogenic silver nanoparticles (Ch@BSNP) has been evaluated for the protective management of bacterial leaf spot (BLS) disease in tomatoes caused by Xanthomonas campestris (NCIM5028). The Ch@BSNP originated by the Trichoderma viride (MTCC5661) derived extracellular compounds and subsequent chitosan hybridization. Spherical-shaped Ch@BSNP (30–35 nm) treated diseased plants were able to combat the biotic stress, as evidenced by the decreased elevated response of stress markers viz; anthocyanin (34.02%), proline (45.00%), flavonoids (20.26%), lipid peroxidation (10.00%), guaiacol peroxidase (36.58%), ascorbate peroxidase (41.50%), polyphenol oxidase (25.34%) and phenylalanine ammonia-lyase (2.10 fold) as compared to untreated diseased plants. Increased biochemical content specifically sugar (15.43%), phenolics (49.10%), chlorophyll, and carotenoids were measured in Ch@BSNP-treated diseased plants compared to untreated X. campestris-infested plants. The Ch@BSNP considerably reduced stress by increasing net photosynthetic rate and water use efficiency along with decreased transpiration rate and stomatal conductance in comparison to infected plants. Additionally, the expression of defense-regulatory genes viz; growth responsive (AUX, GH3, SAUR), early defense responsive (WRKYTF22, WRKY33, NOS1), defense responsive (PR1, NHO1, NPR1), hypersensitivity responsive (Pti, RbohD, OXI1) and stress hormones responsive (MYC2, JAR1, ERF1) were found to be upregulated in diseased plants while being significantly downregulated in Ch@BSNP-treated diseased plants. Furthermore, fruits obtained from pathogen-compromised plants treated with Ch@BSNP had higher levels of health-promoting compounds including lycopene and beta-carotene than infected plant fruits. This nano-enabled and environmentally safer crop protection strategy may encourage a sustainable agri-system towards the world's growing food demand and promote food security.

Assessing restoration and degradation of natural and artificial vegetation in the arid zone of Northwest China

Assessing vegetation restoration and degradation trends is important for regional ecological conservation and sustainable development, yet few studies have examined the characteristics of these trends in natural and artificial vegetation in arid zones. In this study, we develop an assessment framework based on two common ecological indicators, Net Primary Productivity (NPP) and Water Use Efficiency (WUE). We discuss the restoration and degradation trends of natural and artificial vegetation in China’s Northwest Arid Region (NAR) and analyze the similarities and differences between the changes in the two. Our results reveal the following: (1) Both natural vegetation (Nav) NPP and artificial vegetation (Arv) NPP in the NAR are dominated by significant growth, with precipitation being the most influential factor. Arv NPP changes are greater than Nav NPP. (2) WUE and NPP have similar spatial distribution characteristics, with precipitation and temperature dominating WUE changes in the Qilian Mountains and s southern Xinjiang, respectively. In the near future, Nav WUE is expected to be dominated by improvement to degradation, while Arv WUE will continue to improve under human intervention. These two indices respond differently to the environmental factors that cause their changes. (3) Nav and Arv exhibit similar restoration and degradation trends, mainly dominated by early recovery with Nav displaying a slightly more prominent restoration trend than Arv. The NPP-WUE assessment framework will help to rapidly assess vegetation degradation and restoration at large scales, providing new perspectives for research in this field.

Arbuscular mycorrhizal fungi promote photosynthesis in Antirrhinum majus L. under low-temperature and weak-light conditions

Low-temperature and weak-light conditions have major effects on the growth and flower quality of horticultural plants. A greenhouse pot experiment was performed to investigate the effects of arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae and Glomus versiforme) on the growth, photosynthesis, and chlorophyll fluorescence parameters of snapdragon (Antirrhinum majus L.) under low-temperature and weak-light stress. The growth and biomass of snapdragon were higher following inoculation with F. mosseae and G. versiforme compared with control plants. The percentage of mycorrhizal colonization and root activity were high in A. majus plants with AMF. AMF inoculation enhanced the net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency of plants under low-temperature and weak-light conditions. Furthermore, the chlorophyll content, potential activity of photosystem II (PSII), effective photochemistry quantum efficiency of PSII, actual photochemical quantum efficiency of PSII, and photochemical quenching coefficient were higher in AMF-inoculated plants than in uninoculated plants. The application of AMF reduced the intercellular CO2 concentration and non-photochemical quenching coefficient. Thus, snapdragon plants treated with F. mosseae and G. versiforme are more resistant to low-temperature and weak-light stress than untreated plants.

Brassica carinata physiological response to land preparation method and seeding rate

ABSTRACT Best management practices that optimize agronomic performance and make Brassica carinata production compatible with existing cropping systems are crucial for the establishment of a carinata supply chain in the southeastern United States. To this end, research was carried out to quantify land preparation method (conventional, no-till, broadcast-disc, and ripper-roller) and seeding rate effects on (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on B. carinata physiology, yield, and seed chemical composition. Data were collected on days to 50% flowering; canopy cover; gaseous exchange parameters (leaf net photosynthesis, stomatal conductance, transpiration, intercellular CO2, and water use efficiency); leaf area index; root weight; shoot weight; aboveground biomass; yield; and seed chemical composition. Leaf net photosynthesis was affected by land preparation treatment, being greater under the ripper-roller treatment, particularly during bolting. On the other hand, a decrease in photosynthesis, stomatal conductance, and water use efficiency was observed as seeding rate increased, especially during bolting. Carinata seed under the ripper-roller land preparation had the greatest oil content but lowest glucosinolates and protein contents. Yield did not respond to land preparation. Yield was minimized (732 kg seed ha−1) at the 1.12 kg ha−1 seeding rate and maximized (1087 kg seed ha−1) at the 5.6 kg ha−1 seeding rate. No land preparation by seeding rate interaction was observed for gas exchange parameters and LAI during any of the growth stages, nor was any interaction observed for yield. Carinata’s physiological response to seeding rate did not depend on land preparation method employed.

Populus euphratica males exhibit stronger drought and salt stress resistance than females

Much attention has been paid on dioecious plants and their responses to environmental stresses. However, little information is available on sexual dimorphism in Populus euphratica Oliver, which usually grows in arid desert areas and exposes to drought and salinity stress. In this study, we investigated female and male seedlings of P. euphratica and their growth and anatomical structure, gas exchange, water and nitrogen use, oxidative stress and antioxidants under drought, salinity, and the combined stress. We found that there were no significant sexual differences in P. euphratica under control conditions (well-watered and no salt addition). However, males showed stronger resistance to drought, salinity and especially to the combined stress, as they had protective structures, higher biomass, net photosynthetic rate (Pn), water and nitrogen use, osmotic adjustment and reactive oxygen species (ROS) scavenging ability, and a lower leaf Cl– content under stress conditions. The significant sex × drought × salinity interactions for biomass, Pn, water and nitrogen use, superoxide radicals (O2–), proline and free amino acids (FAA) indicated that sexual dimorphism occurs depending on the stress gradients, implying contrasting adaptive responses and life strategies in P. euphratica females and males under stress conditions. Due to the sexual dimorphism of P. euphratica under drought and salinity stress, more severe shifts in the sex ratio of P. euphratica forests may occur under future climate change with aggravated aridity and soil salinity.

Leaf Traits and Resource Use Efficiencies of 19 Woody Plant Species in a Plantation in Fangshan, Beijing, China

Plantations are typically monocultures, which limits their sustainability. Therefore, understanding acclimatization strategies and resource use efficiencies in plant species and life forms aids the improvement of vegetation diversity and ecological functions. Here, 19 species from forest plantations in Fangshan, Beijing, China were studied. We determined their net photosynthetic (Pn), and transpiration rates (E), light response curve, stomatal conductance (gs), and leaf nitrogen (N) content. We analyzed the leaf N content (Nmass), specific leaf area (SLA), maximum net photosynthetic rate (Pnmax), water use (WUE), nitrogen use (NUE), and carbon use (CUE) efficiencies and connected them with both species and life forms. Pnmax, SLA, Nmass, WUE, NUE, and CUE significantly differed among species. Evergreen conifers had the lowest SLA and Nmass but the highest WUE and CUE. Evergreen coniferous trees had lower SLA, Nmass, Pnmax, and NUE but higher WUE than deciduous trees and shrubs. The SLA, Nmass, and Pnmax of nitrogen-fixing plants were the highest. A correlation analysis revealed that WUE was positively correlated with CUE and negatively correlated with NUE. Moreover, WUE was negatively correlated with Nmass and SLA. These insights into the adaptability differences of woody plant species and life forms provide a scientific basis for the selection of appropriate species for sustainable forest plantations.

Ecosystem Functioning of the Loess Plateau in China from Vegetation Restoration Relied Largely on Climate

Climate change and anthropogenic replantation are supposed to greatly change vegetation coverage and ecosystem stability and functions, e.g., net primary productivity (NPP), evapotranspiration (ET) and water use efficiency (WUE). Our study compared WUE of nature- and human-induced forest cover increase on the Loess Plateau since 2000 using satellite-derived Vegetation Continuous Fields (VCF), NPP, ET. This study also applied over 30 years of model-based NPP and meteorological observations to compare the stability and changes brought up by the Grain for Green Project. The result showed that the average forest coverage fraction increased from 7.1% (~4.5 × 104 km2) in 2000 to 11.2% (~7.3 × 104 km2) in 2014. Artificial forest cover increase occupied 76.43% of the significantly increasing tree cover regions. The role of revegetation practice in NPP and ET became gradually more dominant than climate factors in artificial forests from the northern to the southern part of the Loess Plateau. For areas experiencing limited forest coverage increase, artificial forest areas showed higher WUE than natural forest areas under similar mean annual precipitation (MAP). The difference in stability was small between neighboring natural and artificial forest areas. The northwest of the Loess Plateau had an increasing resilience, whereas the south of the Plateau had an increased resistance to precipitation and temperature change. The higher dependency of the northern reforested areas on climate fluctuation indicates a growing threat of water scarcity to the sustainability of anthropogenic reforestation in semi-arid regions.

Morphological and physiological response of Chinese tallow (Triadica sebifera) to an extreme cold spell in subtropical, coastal forests of China

Acute and extreme weather events can cause considerable damage to the tissues of trees, including stem death and branch or leaf distortion, which may limit their survival and reproduction. In January 2016, a rare cold spell impacted the coastal forests of subtropical China. Using post-hoc assessments, we evaluated the morphological and physiological response of Chinese tallow (Triadica sebifera L.) to the extreme cold spell in two distinct ecoregions, one (Xiangshan, China) representing the cold spell impacted zone and the other (Taizhou, China) representing the non-affected zone. To determine if the extreme cold events impacted the vigor of Chinese tallow, we assessed differences in growth rate, leaf characteristics, and leaf gas exchange. As age may affect tree morphological and physiological response to stress, we grouped subject trees into three distinct cohorts, namely, seedlings (1–2 years old), young-aged (5–6 years old), and middle-aged (10–12 years old). Our results suggest that although tree height and diameter did not differ, leaf area expansion and leaf mass were reduced in the impacted zone. In seedling and young-aged trees, the cold spell significantly reduced leaf net photosynthetic (An), transpiration rates (Tr), stomatal conductance (Gs) and water use efficiency (WUE) while leaf intercellular CO2 concentration (Ci), vapor pressure deficit (Vpd), and intercellular CO2 pressure (Ci-Pa) increased. In contrast, the middle-aged group was less responsive to the cold spell. Across all cohorts, the event did not affect leaf temperature (Tleaf), but the activity of superoxide dismutase (SOD) and peroxidase (POD) decreased. We also detected increases of leaf malondialdehyde (MDA) and free proline (Pro) contents in young-aged and middle-aged groups. Hence, the extreme cold spell caused remarkable negative effects on the morphological and physiological traits of Chinese tallow. Redundancy analysis revealed that the cold spell also impacted the subsequent recovery process of damaged Chinese tallow by reducing the ability of leaf to utilize microenvironmental resources (radiation, air humidity, and CO2) for gas exchange. Results from this study are important to strengthen our understanding of Chinese tallow responding to extreme cold stress within its native range, also be helpful to predict the distributions of Chinese tallow in its invasive range where it has devastating impacts to coastal ecosystems in the southeast US.

How does irrigation alter the water, carbon, and nitrogen budgets in a large endorheic river basin?

• Irrigation substantially alters the water, carbon, and nitrogen budgets in the cropland area. • Evapotranspiration as well as surface runoff and baseflow is sharply increased after irrigation. • Water use efficiency of each crop species is significantly enhanced because of irrigation. • The cropland area of the Heihe River Basin switches from being a carbon source to a carbon sink as a result of irrigation. Irrigation can substantially alter the hydrologic and biogeochemical cycles in river basins. However, little attention has been given to the quantitative evaluation of the effects of irrigation on both of these cycles. In this study, we utilized the latest version of the Community Land Model (CLM5) to assess the effects of irrigation on the water, carbon, and nitrogen budgets in a cropland area of a large endorheic river basin (Heihe River Basin, HRB) in northwestern China and further identified the contributions of each type of crop to the abovementioned budgets. The model has been validated against local flux towers, remote sensing products, and reanalysis datasets, demonstrating the capability of CLM5 in capturing the temporal and spatial characteristics of water, carbon, and nitrogen at the basin scale. Two numerical experiments, one with irrigation and one without it, were conducted to explore the relationships between water and carbon/nitrogen budgets for the period from 2000 to 2018. The simulation results showed that the greatest amount of irrigation was applied in the summer (>50 mm month −1 ) and then declined to a low level during the other seasons. Evapotranspiration (ET) in the cropland area sharply increased from 106 mm year −1 to 508 mm year −1 , with an increase in surface runoff and baseflow after irrigation. Both irrigated gross primary production (GPP), net ecosystem exchange (NEE) and water use efficiency (WUE) peaked in the summer, which corresponded to the crop growing season. A shift in NEE from 6 gC m −2 year −1 to –229 gC m −2 year −1 indicated that the cropland area in the HRB switched from being a carbon source to a carbon sink because of irrigation. The corn area presented the largest increase/decrease in GPP/NEE after irrigation, whereas the lowest increase/decrease in GPP/NEE was observed in the cotton area. Total ecosystem carbon (TEC) and total ecosystem nitrogen (TEN) markedly increased as a result of irrigation, with increases of 3.29 × 10 13 gC and 2.96 × 10 12 gN, respectively, throughout the year in the cropland area. Overall, our study demonstrates that irrigation has substantial impacts on water, carbon, and nitrogen budgets in the cropland area of the HRB and provides important insights into the application of CLM5 in an arid basin with multiple crop types.

Integrated metabolomic and transcriptomic analyses reveal different metabolite biosynthesis profiles of Juglans mandshurica in shade.

Light is not only a very important source of energy for the normal growth and development of plants, but also a regulator of many development and metabolic processes. The mechanism of plant growth and development under low light conditions is an important scientific question. With the promulgation of the law to stop natural forest cutting, understory regeneration is an important method for artificial forest afforestation. Here, the growth and physiological indexes of Juglans mandshurica, an important hardwood species in Northeast China, were measured under different shade treatments. In addition, transcriptome and metabolome were compared to analyze the molecular mechanism of shade tolerance in J. mandshurica. The results showed that the seedling height of the shade treatment group was significantly higher than that of the control group, and the 50% light (L50) treatment was the highest. Compared with the control group, the contents of gibberellin, abscisic acid, brassinolide, chlorophyll a, and chlorophyll b in all shade treatments were significantly higher. However, the net photosynthetic rate and water use efficiency decreased with increasing shade. Furthermore, the transcriptome identified thousands of differentially expressed genes in three samples. Using enrichment analysis, we found that most of the differentially expressed genes were enriched in photosynthesis, plant hormone signal transduction and chlorophyll synthesis pathways, and the expression levels of many genes encoding transcription factors were also changed. In addition, analysis of differentially accumulated metabolites showed that a total of 470 differential metabolites were identified, and flavonoids were the major differential metabolites of J. mandshurica under light stress. These results improved our understanding of the molecular mechanism and metabolite accumulation under light stress in J. mandshurica.

Effects of Exogenous Salicylic Acid (SA), 6-Benzylaminopurine (6-BA), or Abscisic Acid (ABA) on the Physiology of Rosa hybrida ‘Carolla’ under High-Temperature Stress

The study of the regulatory mechanism of exogenous plant growth regulators (PGRs) on the relevant physiological indicators is essential to maintain the normal growth of Rosa hybrida under high-temperature conditions. The photosynthetic and physiological characteristics of the ornamental cut rose Rosa hybrida ‘Carolla’ under high temperature were studied by spraying leaves with various concentrations of exogenous salicylic acid (SA; 0.5, 1.0, 1.5, or 2.0 mmol·L−1), 6-benzylaminopurine (6-BA; 10, 20, 30, or 50 μmol·L−1), abscisic acid (ABA; 10, 20, 30, or 50 mg·L−1), or distilled water (control). The results indicated that a foliar spray of either SA, 6-BA, or ABA could mitigate the impact of high temperatures. Compared to the control, the application of SA, 6-BA, or ABA increased the net CO2 assimilation rate (An), transpiration rate (E), stomatal conductance (Gs), and water use efficiency (WUE) of ‘Carolla’, while decreasing the leaf relative electrical conductivity (REC) and malondialdehyde (MDA) content. The applications of SA, 6-BA, or ABA increased the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) and altered the proline (Pro), soluble protein, and soluble sugar contents. The results showed that foliar sprays of SA, 6-BA, or ABA could enhance the heat tolerance of ‘Carolla’ by promoting photosynthesis, cell membrane structural stability, antioxidant enzyme activity, and osmoregulation in plants under high-temperature stress. The experiment showed that 1.5 mmol·L−1 SA, 20 μmol·L−1 6-BA, or 75 μmol·L−1 ABA could alleviate the damage caused by high temperatures, with 20 μmol·L−1 6-BA having the best effect.

Impact of Biochar Application at Water Shortage on Biochemical and Physiological Processes in Medicago ciliaris.

The application of biochar is mostly used to improve soil fertility, water retention capacity and nutrient uptake. The present study was conducted in order to study the impact of biochar at water deficiency conditions on the physiological and biochemical processes of Medicago ciliaris seedlings. Seedlings were cultivated under greenhouse conditions in pots filled with a mixture of soil and sand mixed in the presence or absence of 2% biochar. Plants of uniform size were subjected after a pretreatment phase (72 days) either to low (36% water holding capacity, water potential low) or high soil water potential (60% water holding capacity, water potential high). Pots were weighed every day to control and maintain a stable water holding capacity. In Medicago ciliaris, drought led to a significant reduction in plant growth and an increase in the root/shoot ratio. The growth response was accompanied by a decreased stomatal conductance and a reduction of the net CO2 assimilation rate and water use efficiency. The associated higher risk of ROS production was indicated by a high level of lipid peroxidation, high antioxidant activities and high proline accumulation. Soil amendment with biochar enhanced the growth significantly and supported the photosynthetic apparatus of Medicago ciliaris species by boosting chlorophyll content and Anet both under well and insufficient watered plants and water use efficiency in case of water shortage. This increase of water use efficiency was correlated with the biochar-mediated decrease of the MDA and proline contents in the leaves buffering the impact of drought on photosynthetic apparatus by increasing the activity of enzymatic antioxidants SOD, APX, GPOX and GR and non-enzymatic antioxidants, such as AsA and DHAsA, giving the overall picture of a moderate stress response. These results confirmed the hypothesis that biochar application significantly reduces both the degree of stress and the negative impact of oxidative stress on Medicago ciliaris plants. These results implied that this species could be suitable as a cash pasture plant in the development of agriculture on dry wasteland in a future world of water shortages.

Impact of Different Colour Low Tunnel Shade Nets and Mulches on Water use Efficiency and Nutrient use Efficiency in Chrysanthemum

An investigation was carried out in an experimental field of the College of Agricultural Engineering, University of Agricultural Sciences, Raichur, to investigate the effect of different coloured low tunnel shade nets and different mulches on water use efficiency and nutrient use efficiency of chrysanthemum. The results revealed that the values of daily evapotranspiration under different colours’ low tunnel shade net were less than the values of evapotranspiration under open field for all months. It is because of the green-house effect and low radiation. The values of ET during the seasons were lower under white-coloured shade net compared to open field conditions. The results indicate that significant irrigation water savings occur in chrysanthemums under different coloured low tunnel shade nets as compared to open field cultivation. It is also found that the chrysanthemum crop requires approximately 31%, 28%, and 23% less water under white, green, and black shade net compared to the total water required under open field cultivation. The highest water use efficiency was recorded with the white colour low tunnel shade net (28.78 kg ha-1 mm-1) and this was followed by the green shade net (28.64 kg ha-1 mm-1), black shade net (13.09 kg ha-1 mm-1) and lowest water use efficiency was recorded under open field conditions (10.58 kg ha-1 mm-1). Among the different mulches, the highest water use efficiency was recorded by the use of white coloured mulch (24.36 kg ha-1 mm-1) and this was followed by silver mulch (21.75 kg ha-1 mm-1), black mulch (20.82 kg ha-1 mm-1), and jute mulch (19.38 kg ha-1 mm-1). The lowest water use efficiency was recorded where mulch was not used (15.05 kg ha-1 mm-1). The highest nutrient use efficiency was recorded with the white colour low tunnel shade net (Nitrogen (N)=72.51 kg ha-1, Phosphorous (P)=12.37 kg ha-1 and Potassium (K)=73.84 kg ha-1 ) and this was followed by the green shade net (N=66.77 kg ha-1, P=10.28 kg ha-1 and K=64.33 kg ha-1), open field conditions (N=58.08 kg ha-1, P=8.72 kg ha-1 and K=56.36 kg ha-1) and lowest nutrient use efficiency was recorded under black shade net (N=51.60 kg ha-1, P=6.98 kg ha-1 and K=49.75 kg ha-1). Among the different mulches, the highest nutrient use efficiency was recorded by the use of white colour mulch (N=77.53 kg ha-1 P=11.74 kg ha-1 and K=73.20 kg ha-1) and this was followed by silver mulch (N=70.50 kg ha-1, P=10.61 kg ha-1 and K=66.86 kg ha-1), black mulch (N=65.08 kg ha-1, P=9.51 kg ha-1 and K=64.09 kg ha-1), and jute mulch (N=57.75 kg ha-1, P=8.96 kg ha-1and K=64.09 kg ha-1). The lowest nutrient use efficiency was recorded where mulch was not used (N=40.22 kg ha-1, P=7.11 kg ha-1 and K=44.44 kg ha-1). The results indicated that there is a bright scope for cultivation of chrysanthemum under white colour low tunnel shade net with white plastic mulch.

Effects of organic fertilizers on growth characteristics and fruit quality in Pear-jujube in the Loess Plateau

The ecological environment of the hilly and gully area of the Loess Plateau in northern Shaanxi is fragile and the soil fertility is low. As a result, the yield and quality of Pear-jujube which constitute one of the dominant economic forests in this region, have been severely restricted. At present, the scientific application of fertilizer is important for comprehensively improving the quality of fruit trees, and for devising the optimal management of fruit trees. In particular, the application of organic fertilizers plays an important role in improving soil and improving fruit quality. In this experiment, a field study was conducted to understand the effects of different organic fertilizer applications on physiological growth, photosynthetic characteristics, reproductive growth and nutritional quality of Pear-jujube in the Loess Plateau. The results showed that organic fertilizer significantly promoted the physiological growth of Pear-jujube. The Pear-jujube bearing branch and leaf area under the soybean cake fertilizer (SC) treatment were 20.17 cm and 1246 mm2/leaf, respectively, which are increased by 34% and 44.46% compared with the no fertilizer treatment, which was a control check (CK). The total chlorophyll content of fertilization treatment was significantly higher than that of CK (P < 0.05). The maximum of chlorophyll content was 10.90 mg/dm2 under the biogas fertilizer (BM). The content of LAI was in the order BM > conventional fertilizer (CF) > sheep manure (SM) > SC > CK. The changing trend of gap fraction was opposite to that of LAI, and the density of light was consistent with that of LAI. The density of light BM was the largest, reached 38.06 mol/(m2 d), which was 15.13% higher than that of CK. Organic fertilizer significantly improved the net photosynthetic rate (Pn) and water use efficiency (WUEp) of Pear-jujube. The WUEp of SC was up to 3.30%. Organic fertilizer significantly promoted the reproductive growth and improved the nutritional quality of Pear-jujube. The yield under the SC was 19,177 kg/hm2, increased by 138.5% compared with that of CK. The fruit water content (FWC), total soluble solids (TSS), solid-acid ratio (TSS/TA), Vc and total flavonoids content improved, and the maxima of FWC, TSS, TSS/TA, Vc and total flavonoids content under the SC treatment were 86.30%, 18.48%, 40.17, 46.18 mg/kg and 14.35 mg/kg, respectively, which were significantly different from those of CK (P < 0.05). Organic fertilization effectively promotes the growth, development, yield and fruit quality of Pear-jujube in the Loess Plateau and the effect of the soybean cake fertilizer is the most significant.

Regulation effects of carbonized apple branches on absorption, distribution, and utilization of 15N single-labeled ammonium nitrate (15NH4NO3 or NH415NO3) in Malus hupehensis

To improve the utilization of nitrogen fertilizer and orchard waste, the apple branches were separated and pyrolyzed into carbonized wood and carbonized bark, and then applied to root-zone soil of potted Malus hupehensis. The physiological characteristics of leaves and roots were detected, and the absorption, utilization, and distribution of 15NH4NO3 and NH415NO3 in plants were analyzed using the 15N isotope tracer technique. The results indicated that the net photosynthetic rate and water use efficiency of leaves, the root growth, and the activity of nitrate reductase and glutamine synthetase were greatest increased by 1.0% (w:w) carbonized bark and carbonized wood, and the effect of carbonized bark was more effective. The carbonized bark more effectively increased nitrogen derived from fertilizer (Ndff) value in all organs, the distribution of 15N in roots, and utilization of the 15NH4NO3 and NH415NO3 of Malus hupehensis compared with carbonized wood at the same application ratio, and 1.0% ratio performed better than other ratios in these terms. The Malus hupehensis treated with carbonized bark had the highest utilization ratio of 15NH4NO3 (10.54%) when the application ratio was 1.0%, and the corresponding parameter of NH415NO3 was 12.98%. The soil immobilization capacity of 15N was improved, and carbonized bark resulted in the greatest decrease in the loss ratios of 15NH4NO3 and NH415NO3 under 1.0% ratio, which decreased by 27.33% and 30.08%, respectively. For reducing nitrogen loss and improving nitrogen utilization, carbonized bark was more effective than carbonized wood, mainly because bark contained more cellulose and less lignin than wood.

Optimization of water and land allocation in salinity and deficit- irrigation conditions at farm level in Qazvin plain.

Improper extraction of water from resources especially in arid and semi-arid regions leads to a decrease in the quality of water and soil resources. In such areas, management activities such as increasing water productivity in agricultural sector would be a key step towards sustainable development. Therefore, water resources management to improve the allocation of limited water supplies is essential. In this study, a non-linear programming optimization model have been combined with a AquaCrop model to determine the optimal water and land allocation considering the quality issues of both water and soil resources with focusing on enhancing agriculture water productivity. For this purpose, the spatial variations of chemical and physical properties of soil in the Qazvin plain were taken into account. The soil of study site was divided into three salinity classes, and three weather conditions were identified by Standardized Precipitation Index (SPI). Moreover, five irrigation strategies were modeled under each weather condition. To understand the response of major crops under cultivation to water and salinity, the AquaCrop model was calibrated and validated (2005-2020) and utilized in the objective function. Accordingly, the production functions of the different products were obtained, and the cultivation area as well as amount of water consumption of the crops were optimized by using the target functions of maximum net income and maximum water use efficiency. The results showed that the model is capable of simulating crop yield in salinity and water deficit conditions. The coefficient of determination (R2) for barley, wheat and maize was equal to 0.86, 0.92, and 0.96, respectively. Findings reveal that total irrigation water could be reduced by 20% on average without profit reduction when compared to the profit of the present situation. Total economic profit could be increased by 18% on average through the optimization of water allocation and cropping pattern with the same water supply amount as that of the current situation. Also, the water productivity increased between 12 to 30% under these conditions. Therefore, the proposed model can efficiently optimize the amount of irrigation water and cultivation area on a regional scale considering salinity conditions.

Effects of elevated CO2 on grain yield and quality in five wheat cultivars

AbstractElevated atmospheric CO2 concentrations (e[CO2]) have a significant impact on plant physiology, grain yield and quality and the specific response of plants to e[CO2] is closely linked to cultivars. Here, five Chinese wheat (Triticum aestivum L.) cultivars were grown under ambient CO2 (a[CO2], 400 ppm) and e[CO2] (800 ppm). CO2 enrichment significantly increased net photosynthetic rate and water use efficiency but depressed stomatal conductance. e[CO2] increased the carbon (C) concentration but decreased the nitrogen (N) concentration in all five cultivars, whereas the effect of e[CO2] on grain yield was highly dependent on cultivar. Moreover, e[CO2] caused a significant reduction in grain minerals and protein, although the magnitude of reduction was different among these cultivars. The starch concentrations in the grains and flour viscosity were not significantly affected at e[CO2]. These findings improve our understanding of the interactive effect of CO2 conditions and cultivars on plant performances and provide a research basis to select suitable wheat cultivars to deal with food crisis in future climate.

Bacillus subtilis Inoculation Improves Nutrient Uptake and Physiological Activity in Sugarcane under Drought Stress.

Sugarcane (Saccharum spp.) is one of the most important crops in the world. Throughout the sugarcane’s growth stages, periods of drought are common, causing detrimental effects on plant growth. Therefore, the search for strategies for minimizing the impact of drought on sugarcane development is of great interest. Plant growth-promoting bacteria hold the potential for improving tolerance to drought in agricultural systems. Thus, the present study aimed to evaluate whether inoculation with Bacillus subtilis can reduce the negative effects of drought on the nutritional, physiological, and morphological characteristics of sugarcane plants. For this, sugarcane was cultivated in a greenhouse, under controlled conditions of water and temperature, with the aid of four treatments: without and with inoculation of B. subtilis, in normal conditions of water availability, and in conditions of water restriction (2 × 2 factorial), with four replications. In treatments with inoculation, the pre-emerged seedlings were immersed in a B. subtilis solution and transplanted into experimental pots. Our results showed that inoculation with B. subtilis improved plant nutrition and chlorophyll concentrations. As a result, the gas exchange parameters (especially net photosynthetic rate and water use efficiency) were also improved, even under drought conditions. In addition, stress parameters (antioxidant metabolism activity) were reduced in inoculated plants. The sum of these beneficial effects resulted in increased root growth, tillering, stalk weight, and higher sucrose concentration in the stalks.

The salicylic acid mediates selenium-induced tolerance to drought stress in tomato plants

The role of selenium (Se) in mitigating detrimental effects of drought stress on the plants has been reported, but the mechanism is still unclear. In this study, the function of Se fertilization on tomato (Solanum lycopersicum L.) under drought stress was characterized. Our results showed that the growth reduction caused by drought stress was alleviated by application of exogenous Se to a large extent. In addition, the treatment of Se significantly increased the net photosynthetic rate (Pn), transpirational rate (Tr), stomatal conductance (Gs) and water use efficiency (WUE) than in the absence of Se under drought stress treatment. Se addition also significantly inhibited the increase of malondialdehyde (MDA), soluble sugar and proline levels of tomato leaves and produced less reactive oxygen species (ROS) accumulation under drought stress. Furthermore, Se supplementation to the nutrient solution significantly increased the endogenous salicylic acid (SA) and methylated SA (MeSA) levels in tomato roots and promoted the conversion from SA to MeSA in tomato leaves under drought stress conditions via regulating the expression levels of several genes involved in SA biosynthesis and conversion such as PAL1, ICS, SAMT and SABP2. But the pretreatment with ABT (1-aminobenzotriazole, a SA inhibitor) abolished the beneficial effect of Se on drought stress tolerance of plants. These results suggested that Se application promoted photosynthetic efficiency and plant growth, alleviated drought-induced oxidative stress, and increased the endogenous SA levels, thereby imparting drought stress tolerance of tomato plants. This study may provide a theoretical basis for utilization of Se fertilizer to improve the yield and quality of agricultural products under stress.

Crop-growth-based spatially-distributed optimization model for irrigation water resource management under uncertainties and future climate change

The spatially distributed AquaCrop-multiobjective robust possibilistic programming (distributed AquaCrop-MORPP) model that considers spatially-distributed land, soil and management features has been proposed for irrigation scheduling optimization under uncertain conditions. Compared with traditional simulation-optimization models, it improved the robustness of decision making by optimizing irrigation amounts and dates considering physical crop growth process and the spatial heterogeneity of soil, crop and irrigation. Additionally, it enhanced the AquaCrop-optimization model by handling uncertainties presented as fuzzy and stochastic variables. Moreover, it enhanced the applicability of multi-objective programming (MOP) by balancing contradictory relationships between the objectives of the net economic benefit and field water use efficiency, which were simulated and calculated by the spatially-distributed AquaCrop model. Fifty groups of optimal Pareto solutions were obtained by solving the spatially-distributed AquaCrop-MORPP model using a fast and elitist multi-objective genetic algorithm (NSGA-II) method. Subjective decision-making methods (e.g., Technique for order preference by similarity to an ideal solution (TOPSIS) and prospect theory) were used to select specific alternatives from the Pareto solutions to provide recommendations for managers from different viewpoints. The alternatives that maximized field water use efficiency or net economic benefit separately were selected to cope with emergencies. To obtain optimal irrigation scheduling under future climate change, the RCP4.5 future climate scenario was integrated with the spatially-distributed AquaCrop-MORPP model. The model was verified by applying it to the Yingke Irrigation District (YID), Heihe River Basin (HRB), China. The results showed that the maximum field water use efficiency and net economic benefit in 2021 improved by 24% and 1.3% than those in 2012 for the alternative selected by TOPSIS method. The irrigation scheduling with varied irrigation dates improved by 3.7% and 5% than the irrigation scheduling with fixed irrigation dates for field water use efficiency and net economic benefit, separately. The study provides a framework about how to build spatially-distributed crop simulation-optimization model with consideration of tradeoffs amid multiple objectives to optimize irrigation schedules, and how to select alternatives based on managers’ risk attitudes, and offer a series of Pareto solutions for managers.