Soil Field Capacity Research Articles

Adapting 3-PG foliar variables to deciduous trees in response to water restriction: poplar short rotation plantations under Mediterranean conditions

Abstract Poplar plantations growing in short rotation are a crucial biomass source of raw material for bioenergy and/or bioproducts, making an important contribution towards achieving a low-carbon bioeconomy. To optimize yield predictions of poplar plantations, this study aims to adapt the foliar variables of the process-based model 3-PG (Physiological Principles Predicting Growth) to a deciduous species like poplar. A total of 138 trees were sampled from a poplar plantation of the highly productive hybrid P. x canadensis (‘AF2’) over a first rotation at a planting density of 10 000 trees ha−1. Two irrigation scenarios, full soil field capacity (FC) and 50% FC, were considered to take into account the impact of climate change in the context of irrigation restrictions. Based on this information, the objectives were not only to determine the required species-specific foliar parameters but also to adapt the 3-PG model architecture to a pattern of variation along each growing season and identify the foliar parameters which present a significant response to restrictive irrigation. For this, specific leaf area (SLA) changes were modelled and the litterfall rate (${\gamma}_F$), and maximum canopy quantum efficiency (${\alpha}_{Cx}$) were calculated. SLA follows a similar dynamic in terms of water availability and year, with SLA for mature leaves being 19.9 m2 kg−2 and the SLA at the beginning of the growing season 10.4 m2 kg2. Leaf litter season begins in late August and lasts until early December, with 26 per cent litterfall by October. Additionally, the highly sensitive parameter ${\alpha}_{Cx}$ was calibrated and a proposed value of 0.093 molC mol PAR−1 was used. The validation of the proposed parameterization showed realistic estimates of the changes of leaf biomass and LAI during the growing season. These results will enable improved 3-PG-based estimations of the real variation along the growing season of variables such as Net Primary Productivity, leaf litterfall or analysis of the soil–plant nutrient cycle.

Mitigation of drought disaster in sorghum (Sorghum bicolor l. Moench) in Ultisol soil with application of soil amendments and NPK for diversification and improvement of food security

Drought is a common obstacle in crop cultivation. One third of the world’s food land is experiencing drought, which is increasing from year to year. Mitigation measures are needed to maintain national food security. The use of compost and biochar on Ultisol soils can increase crop yields and productivity under drought stress. Research on Jantho Ultisol soil with low fertility using a soil amadement of 10 t. ha−1, compost can increase soil pH from 4.57 to 5.97 at 50% field capacity soil moisture, an increase in sorghum yield from 1.54 t.ha−1 to 3.37 t.ha−1. Application of biochar 10 t.ha−1 increased pH from 4.57 to 5.03 at 50% field capacity soil moisture, an increase in yield from 1.5 4 t.ha−1 to 2.65 t.ha−1 with 600 kg ha−1 NP K fertilization at 50% soil field capacity moisture. The application of compost and biochar was effective in increasing soil pH and sorghum yield on Ultisol soil. This has mitigated the impact of drought and is an opportunity to increase productivity, diversify of food to increase food security towards food sustainability.

Evaluation of IoT based smart drip irrigation and ETc based system for sweet corn

Smart irrigation is one form of precision irrigation that can help farmers maximize crop production while preserving water and energy. Many different types of smart irrigation system can be used, but there is no scientific consensus about which type is the finest. The purpose of this study was to compare various irrigation methods: an IoT-based soil moisture monitoring (IoT-SM) method using moisture sensors and an ET–based strategy. The best irrigation scheduling strategy should be determined by commercial production: keeping the soil water content near field capacity will result in a better fresh yield but not a more dry matter. Sweet corn was chosen as the crop under study. Growth characteristics (plant height, yield, and water productivity) were compared for each of the two approaches. For IoT based soil moisture monitoring method, two irrigation regimes were used: 43.5 per cent and 34.8 per cent (as field capacity (FC) of soil and 80% of FC, respectively) and crop evapotranspiration (ETc 100 per cent) for the ET-based method. The results showed that the IoT-SM 43.5 per cent could produce higher yields of about 12.05% and water savings by 11% compared to the ETc 100 per cent-based irrigation method. The developed IoT system was durable and water-resistant, allowing it to be deployed in outdoor agriculture. At the same time, a solar power supply eliminates the need for cabling and reduces sensor node maintenance.

Evaluation of Some Okra and Molokhia Landraces under Irrigation Water Salinity Stress

Aims: Evaluate eight landraces of okra and five landraces of molokhia, collected from different region of Egypt, under different levels of irrigation water salinity.
 Study Design: The experimental design used was a split-plot in a randomized complete blocks design with three replicates, where the four irrigation water salinity concentrations were arranged in the main plots, whereas, landraces of okra or molokhia were arranged in the sub plots.
 Place and Duration of Study: This investigation was carried out during the two successive summer seasons of 2021 and 2022 at Soil Salinity Laboratory Research, Alexandria Governorate, Agricultural Research Center.
 Methodology: Four levels of saline irrigation water were applied having EC of 625 (tap water as a control), 2000, 4000 and 6000 ppm which was applied as necessary according to soil field capacity (27.85%).
 Results: Generally, all the studied traits, of okra and molokhia, decreased as the salinity level increased except for the spines of edible pods which was in contrast, in both seasons. There were significant differences among the studied eight landraces of okra and the studied five landraces of molokhia for all the studied traits in both seasons. Edible pods yield/plant of Behera landrace was not significantly affect by irrigation at salinity levels up to 2000 ppm of salinity level in 2022 season. Moreover, Alexandria and Gharbya landraces were the least affected by increasing salinity levels comparing with the rest of landraces in both seasons. With respect to molokhia, Fresh leafy yield/plot of Alexandria landrace was not significantly affected by irrigation at salinity levels up to 2000 ppm of salinity level in the first seasons.
 Conclusion: It can be recommended to cultivate Behera, Alexandria and Gharbya landraces of okra and Alexandria and Kafr Elsheikh landraces of molokhia when irrigation with relatively high levels of salinity, as these landraces were relatively less affected by increasing salinity concentration. These landraces can also be introduced into breeding programs to improve them or develop new varieties that are more salt-tolerant.

Drought-flood abrupt alteration events over China

Drought-flood abrupt alternation (DFAA) is characterized by a period of persistent drought followed by sudden heavy precipitation at a certain level, with impacts on ecosystems and socioeconomic environment. At present, previous studies have mainly focuses on the monthly scale and regional scale. However, this study proposed a multi-indicator daily-scale method for identifying the DFAA occurrence, and explored the DFAA events over China from 1961 to 2018. The DFAA events mainly occurred in the center and southeast of China, especially in the Yangtze River Basin, Pearl River Basin, Huai River Basin, Southeast Rivers Basin, and south part of the Southwest Rivers Basin. The spatial coverage has a statistically significant (p < 0.05) increasing trend over China, of 0.355 %/decade. The occurrence and spatial coverage of DFAA events increased by decades, and were mainly concentrated in summer (around 85 %). The possible formation mechanisms were closely related to global warming, atmospheric circulation index anomalies, soil properties (e.g., soil field capacity), etc.

O CO2 elevado induz a regulação negativa da fotossíntese e alivia o efeito do déficit hídrico em Ceiba pentandra (Malvaceae)

ABSTRACT The simultaneous effect of elevated CO2 concentration and drought on trees is still under investigation in the Amazon. We evaluated the effect of CO2 levels (400 and 800 ppm) and water regimes (50% and 100% soil field capacity) on photosynthetic traits, chlorophyll fluorescence, and total biomass accumulation in Ceiba pentandra. In well-watered plants, light-saturated photosynthesis (PN-sat) increased in plants exposed to elevated CO2, but both PN-sat and stomatal conductance decreased in response to water deficit. The maximum carboxylation rate of Rubisco declined under elevated CO2, which indicates down-regulation of photosynthesis at elevated CO2. The Fv/Fm ratio was not affected by treatments. Notwithstanding, total plant biomass and leaf area were reduced by 34-37% under water deficit, but they were not affected by CO2 levels. The PN-sat values measured in well-irrigated plants at ambient CO2 were similar to those observed in plants subjected to elevated CO2 and water deficit (p = 0.26). We concluded that the effect of water deficit on PN-sat was mitigated by elevated CO2. These results suggest that the increase of atmospheric CO2 concentrations associated to climate changes can at least partly offset the negative effect of drought in this multiuse and widely distributed species.

Spatial Analysis of Soil Properties and Site-Specific Management Zone Delineation for the South Hail Region, Saudi Arabia

Sustainable soil management with the appropriate understanding of soil characteristics is vital in maintaining and improving agriculture soil management. The objectives of the present study are to characterize the spatial variability of soil using the GIS technique and used agglomerative hierarchical clustering (AHC) for the delineation of management zones (MZs) for precision agriculture. A total of 111 soil samples were collected from 37 soil profiles in systematic depths (0–50, 50–100, and 100–150 cm) from the South Hail region, KSA. Samples were analyzed for pH, ECe, CaCO3, available macro and micronutrients, and hydrological properties. The best fit models, using ArcGIS software, were J-Bessel for pH, Clay, bulk density (BD), and available water (AW); K-Bessel for EC and available N; Stable for CaCO3, P, K, Fe, Zn, Sand, field capacity (FC) and saturated hydraulic conductivity (Ks); Spherical for Mn and Cu; Gaussian for saturation percentage (SP); whereas exponential for permanent wilting point (PWP). The principal component analysis (PCA) resulted in six principal components (PCs) explaining 79.75% of the total variance of soil properties. The PC1 was strongly influenced by soil BD, FC, clay, PWP, Ks, and sand. PC2 was dominated by N, ECe, and CaCO3; PC3 was dominated by pH; PC4 was dominated primarily by K and P, PC5 was mainly dominated by Fe; Mn, and Cu, and PC6 was mainly dominated by SP and Zn. Based on AHC, four soil management zones (MZs) cover 77.94, 14.10, 7.11 and 0.85% of the studied area. Management zone 1 (MZ1) and Management zone 3 (MZ3) are classified as moderately saline while Management zone 2 (MZ2) is classified as highly saline soils, greater than the limiting critical value for the sensitive crops. The potential solutions to reduce salinization in the area include: reducing irrigation, moving to salt-tolerant crops or applying humic acids to fix anions and cations and eliminate them from the root zone of the plants. Treating the area with diluted sulfuric acid to remove salts and reduce ECe to less than 2 dSm−1, to get maximum productivity. This finding is diagnostic for determining the amount of fertilizer and irrigation water to be applied to soils in different management zones. Its emphasis’s the importance of site-specific management for long-term crop productivity and, as a result, reducing environmental hazards caused by uneven fertilizers and water applications.

Organic carbon and silt determining subcritical water repellency and field capacity of soils in arid and semi-arid region

Soil water repellency (SWR) is frequently observed in different types of land use and climates. Since SWR potentially enhances the difficulty of water infiltration in soil, the phenomenon can severely impact the water use of plants in arid regions. Therefore, understanding the origin of SWR is crucial in arid and semi-arid regions. This study investigated the fundamental and hydrological properties of soils in three arid ecosystems (desert, farmland, and forest). Analysis was done to determine any potential links between these properties, vegetation cover, and the severity of SWR. It was found that SWR was positively correlated with soil organic carbon (SOC), silt content, and field capacity of soil, where the SWR was in subcritical SWR range. The linear correlation and hierarchical clustering analysis confirmed that the SOC and silt content was the critical factor affecting the occurrence and persistence of SWR. The major source of organic carbon and nutrients to the soil was vegetation, which also had an impact on the distribution of soil carbon. The most striking observation was that the silt content was strongly correlated with both field capacity (r = 0.817, p = 0.001) and SWR (r = 0.710, p = 0.010), which can be attributed to the SOC on silt. In arid and semi-arid regions, the specific surface area of silt was relatively larger than that of sand. Meanwhile, compared to the clay in soil, the proportion of silt was much higher. The results imply that silt could significantly affect the soil hydrological properties and that silt content could serve as a new proxy for predicting water repellency in arid and semi-arid regions.

Water Saving Using Thermal Imagery-Based Thresholds for Timing Irrigation in Potatoes under Drip and Furrow Irrigation Systems

Under the current water crisis in agriculture, irrigation methods for saving and conserving water are necessary. However, these methods must guarantee an appropriate yield with a concomitant economic benefit and a reduced environmental impact. In this study, two irrigation thresholds for irrigation timing (IT) based on thermal imagery were analyzed with the UNICA potato variety in three trials under drip (DI) and furrow (FI) irrigation during 2017–2018 in Lima, Peru. The control (T1) remained at &gt;70% of soil field capacity. For other treatments, thresholds were defined based on stomatal conductance at light saturation (T2: 0.15 and T3: 0.05 mol H2O m−2s−1) and crop water stress index (T2: 0.4 and T3: 0.6) based on canopy temperature. An integrated index (IIN) was established for the valuation of treatments using the criteria of high fresh tuber yield (FTY) and a low total amount of irrigated water, production cost (PC), and total C emissions (TE) and using criteria of a score. FI-T2 (0.69–0.72) and DI-T3 (0.19–0.29) showed the highest and lowest IIN value, respectively. FTY in T2 was not significantly reduced under FI, resulting in a lower PC regarding DI–T2 and emphasizing the usefulness of thermal imagery in determining watering schedules in potatoes under furrow irrigation systems.

Effect of Fertilization and Agricultural Amendments on the quality of a Prairy Established on a Volcanic Soil, Andosol

This research was established at El Prado-IASA1 farm, Agricultural Engineering Career, on a soil of volcanic origin of the Andisol order, in order to evaluate the quality of the forage due to the effect of chemical fertilization and four amendments: lime (E1), gypsum (E2), magnesium silicate (E3) and phosphate rock (E4), mixed amendment (EM) and two level of NPK fertilization. These treatments were applied in an established meadow with: kikuyo (Pennisetum clandestinum), blue grass (Dactylis glomerata), perennial rye grass (Lolium perenne) and white clover (Trifolium repens). The amendments and fertilization were incorporated after the first cut, in an amount equivalent to 1500 of lime, 500 of gypsum, 300 of magnesium silicate and 300 of phosphate rock kg ha-1 year-1, plus fertilization F1: N100-P50-K50 and F2: N300-P100-K100, fractionated for 10 cuts per year. The variables evaluated were: green mass production, dry matter, macro and micronutrient soil content. The forage assessment was based on the physiological growth of rye grass as a dominant prairie species. The results positively affected the quality and production of forage in t ha-1, due to the effect of lime, phosphate rock, and NPK fertilization. There was a high fixation of NH4, K, and P, due to the effect of amorphous minerals, high Fe content, and water deficit. Hence it is recommended to keep close to the soil's field capacity level.

English

To study pre-sowing seed treatment (seed priming) of hormone Mepiquat chloride (MC) (PIX) on physiological properties and increase drought tolerance in cotton (Shayan cultivar), a factorial experiment was performed in a completely randomized design with 3 replications. In this research, the seeds were initially exposed to two doses of the growth-regulatory hormone mepiquat chloride, including 5 and 10 g/l and control before being planted in pots.After the emergence of the plant from the soil, dry treatments based on the soil field capacity (FC) at three levels of irrigation at 25, 50, and 100% of field capacity for six weeks are applied to them, and growth indices, the activity of antioxidant enzymes, amount of hydrogen peroxide and malondialdehyde as well as changes in the two hormones of abscisic acid and endogenous gibberellin was investigated. According to the results of this research, the effect of seed priming with PIX and the interaction of drought × pre-sowing seed treatment on all physiological traits were significant at the level of 1%. The results of experimental data showed that drought stress (especially severe drought) reduced most growth indicator and physiological traits (fresh and dry weight of root and shoot, shoot length, fresh and dry weight of leaf, leaf area, root peroxidation activity, leaf phenol content, amount of gibberellin ) and only increased abscisic acid content (74%), root diameter (38%), root length(14%), leaf thickness, (15%) compared to the control. pre-sowing seed treatment with PIX, while increasing the dry weight (28% roots and 34% leaves) and thickness roots (58%) and 96% leaves (96%), increased catalase (88%) and peroxidase (6%) activity and abscisic acid content (73%) of leaves, reduced hydrogen peroxide (17%), malondialdehyde (20%) of leaves, and gibberellin (40%) of roots. Under extreme drought stress, the application of PIX decreased the amount of phenolic compounds in leaves by 44% as compared to the control. The interplay of drought stress × PIX decreased root gibberellin by 25% and raised leaf abscisic acid by 183%. According to the study results, seed priming with PIX improved the physiological and biochemical responses of cotton under drought conditions

Modification of Soil Physical Properties by Maize Straw Biochar and Earthworm Manure to Enhance Hydraulic Characteristics under Greenhouse Condition

The deterioration of soil physical properties had led to a decrease in soil–water availability in facility agriculture. Thus, an experiment was set up with five soil treatments of 0% (CK, No additives), 3% biochar (BA3, Mass ratio), 3% earthworm manure (QA3), 5% biochar (BA5), and 5% earthworm manure (QA5) to investigate the effects on soil physical properties and hydraulic characteristics under greenhouse conditions. The physical properties of soil including the soil bulk density (BD) and total porosity (TP) were measured; the results showed that BA5 provided the lowest soil BD (1.24 g·cm−3) and the highest TP (53.09%) and was 13.8% higher than CK. More importantly, the saturated hydraulic conductivity (KS), field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of the soils treated with biochar and earthworm manure were significantly higher than those of CK. At the same application rate, the effect of biochar on soil–water permeability and water-retention capacity was significantly higher than that of earthworm manure, in which the soil–water-characteristic curve (SWCC) showed that as BA5 &gt; BA3 &gt; QA5 &gt; QA3 &gt; CK, the FC and AWC increased from 28.90% and 14.13% under CK, respectively, to 40.73% and 21.91% under BA5, respectively; and the KS, FC, PWP and AWC of BA5 increased by 45.93%, 40.91%, 27.46% and 54.96% compared with CK, respectively. The results revealed that the improvement of the soil TP was conducive to the enhancement of the soil KS and FC, enhanced the soil–water permeability and the water-retention capacity, and ultimately increased the AWC. From the perspective of improving the facility soil and economic benefits, the application of 5% biochar is considered to be the most beneficial.

Effect of degree of water stress on growth and fecundity of velvetleaf (Abutilon theophrasti) using soil moisture sensors

AbstractVelvetleaf (Abutilon theophrasti Medik.) is a troublesome broadleaf weed that competes with crops for resources such as soil moisture. Water stress can affect the ability of weed species to grow and produce seeds. The objective of this study was to determine the effect of degree of water stress on the growth and fecundity of A. threophrasti using soil moisture sensors under greenhouse conditions. Abutilon threophrasti seeds collected from a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] field were grown in silty clay loam soil, and plants were maintained at 100%, 75%, 50%, and 25% soil field capacity (FC) corresponding to no, light, moderate, and high water-stress conditions, respectively. Water was added daily to pots based on soil moisture levels detected by a Meter Group 5TM sensor to maintain the desired water-stress level required by treatment. Plants maintained at 100% FC had the maximum number of leaves (28 leaves plant−1), followed by 21 and 15 leaves plant−1 at 75% and 50% FC, respectively. Abutilon threophrasti at 100% and 75% FC achieved maximum plant height (108 to 123 cm) compared with 83 cm at 50% FC. Abutilon threophrasti maintained at 75% FC had the greatest growth index (79,907 cm3) followed by 72,197 cm3 at 100% FC and 64,256 cm3 at 50% FC. Seed production was similar at 100%, 75%, and 50% FC (288 to 453 seeds plant−1) compared with 2 seeds plant−1 at 25% FC. This is because the majority of plants maintained at 25% FC did not survive more than 77 d after transplanting. Seed germination was 96% to 100% at 100%, 75%, and 50% FC compared with 20% germination at 25% FC. Abutilon threophrasti can survive ≥50% FC continuous water-stress conditions, although with reduced leaf number, plant height, and growth index compared with 75% and 100% FC.

Shrub encroachment in alpine meadows increases the potential risk of surface soil salinization by redistributing soil water

Alpine meadows are undergoing shrub encroachment due to climate change and human activities, which affects the health of alpine meadow ecosystems. Previous studies mostly focused on the impact of shrub encroachment on vegetation communities, but few studies were focused on the impact of shrub encroachment on soil pH. This study shed light on this topic by measuring soil moisture and water holding capacity under different levels of shrub encroachment (shrub coverage ranging from 8% to 90%) in alpine meadows located on the Qinghai-Tibet Plateau. Results showed that the intensification of shrub encroachment increased soil saturated water content, soil capillary moisture capacity and soil field capacity, but decreased soil moisture at the uppermost soil layer (0–10 cm). The increase of soil saturated water content and soil capillary moisture capacity increased soil pH. The intensification of shrub encroachment increased soil pH at soil depth of 0–10 cm, but decreased soil pH at soil depth of 20–30 cm. Overall, shrub encroachment could increase soil water and salt upward transport by reducing soil moisture and enhancing soil capillary moisture capacity, resulting in an increase of soil pH. These findings are conducive to better understand the impact of shrub encroachment on the redistribution of soil salinity in alpine meadows, and can provide a theoretical basis for predicting the changes of alpine meadow community facing future climatic change and human activities.

TIP1;1 expression could modulate the recovery of stomatal opening during rehydration in Sorghum bicolor

Stomatal conductance (gs) takes longer to recover after drought when compared to leaf water potential or leaf water content (RWC). Aquaporins, known for transporting water through membranes, could modulate gs recovery. Using Sorghum bicolor, we tested whether members of the plasma membrane (PIP) and tonoplast (TIP) intrinsic aquaporin subfamilies could influence gs after a 20-day drought. Potted plants under soil field capacity (control), severe water deficit (SWD; 30% (m/m) soil water content), and progressive severe water deficit (PSWD; water withheld until maximum stress) were used. Soil (Ψsoil), predawn (ΨPD), and midday (ΨMD) leaf water potentials, photochemical, and gas exchange parameters were measured during drought and 12 days of recovery. After 17 days of drought, gs of SWD and PSWD was 4-times lower than control, and it took 6 days to recover. ΨPD, ΨMD, and RWC, however, recovered after 24 h. SbPIP1;2, SbPIP2;5, and SbTIP1;1 were all down-regulated on the day of maximum stress, but only SbTIP1;1 showed consistent alleviation of its down-regulation as gs recovered. SbTIP1;1 expression was positively correlated with gs, leaf transpiration, and hydraulic conductivity (KL), but only in SWD plants. The slow gs recovery seems to be associated with the alleviation of SbTIP1;1 down-regulation as rehydration progresses.

Soil moisture distribution pattern of surface drip irrigated mango

At present, Pakistan has been facing acute shortage of irrigation water and farmers have been using conventional irrigation methods for orchards, such as flood and basin irrigation, thus wasting huge amount of fresh water. Therefore, it is necessary to find efficient irrigation methods to cope with this major burning issue. The micro drip irrigation method is considered efficient but in the case of mango orchards there is a problem of irrigation frequency, number of emitters, and duration of flow from emitters to meet water demand. Considering the above, an experiment was conducted in the experimental field of the Sindh Agriculture University, Tandojam, by installing the drip system with two circular peripheries of lateral lines in clay loam soil covering the entire canopy of a mature mango tree. The radius of the first and second periphery around the tree trunk was 100 cm and 150 cm, respectively. Four emitters with 4 dm3∙h –1 discharge of individual dipper were fixed in each periphery. Emitters were tested for six different irrigation times, i.e. 1, 2, 3, 4, 5 and 6 h, to observe the moisture distribution pattern. Hydraulic characteristics, such as density, field capacity, porosity, infiltration rate, available water and permanent wilting point (PWP), were determined using standard methods (1.4 g∙cm –3, 33%, 49%, 8 mm∙h –1, 12.41% and 20% respectively). The texture class of the soil profile was determined as clay loam at the soil depth 0–120 cm. Fifty soil samples were collected at 0–10, 10– 30, 30–60, 60–90, and 90–120 cm depths and at 0–20, 20–40, 40–60, 60–80 and 80–100 cm distances on two opposite sides of emitters. The emitters provided sufficient moisture up to field capacity in clay loam soil with flow duration of 4 h. The maximum moisture distribution efficiency was 77.89% with flow duration of 4 h at vertical depth of 0–120 cm and 0–100 cm distance horizontally among four emitters as compared to 1, 2, 3 h flow duration which under irrigated the canopy area and 5, 6 h flow duration which excessively irrigated the canopy area of the mango tree. The water demand of the mango tree was met by 4 h flow duration which provided adequate moisture to the entire canopy up to 120 cm depth in the root zone and water saving was calculated as 15.91% under the installed drip irrigation system as compared with the conventional (basin) irrigation method.

Preconditioning to Water Deficit Helps Aloe vera to Overcome Long-Term Drought during the Driest Season of Atacama Desert.

Throughout evolution, plants have developed different strategies of responses and adaptations that allow them to survive in different conditions of abiotic stress. Aloe vera (L.) Burm.f. is a succulent CAM plant that can grow in warm, semi-arid, and arid regions. Here, we tested the effects of preconditioning treatments of water availability (100, 50, and 25% of soil field capacity, FC) on the response of A. vera to prolonged drought growing in the hyper-arid core of the Atacama Desert. We studied leaf biomass, biochemical traits, and photosynthetic traits to assess, at different intervals of time, the effects of the preconditioning treatments on the response of A. vera to seven months of water deprivation. As expected, prolonged drought has deleterious effects on plant growth (a decrease of 55–65% in leaf thickness) and photosynthesis (a decrease of 54–62% in Emax). There were differences in the morphophysiological responses to drought depending on the preconditioning treatment, the 50% FC pretreatment being the threshold to better withstand prolonged drought. A diurnal increase in the concentration of malic acid (20–30 mg mg−1) in the points where the dark respiration increased was observed, from which it can be inferred that A. vera switches its C3-CAM metabolism to a CAM idling mode. Strikingly, all A. vera plants stayed alive after seven months without irrigation. Possible mechanisms under an environmental context are discussed. Overall, because of a combination of morphophysiological traits, A. vera has the remarkable capacity to survive under severe and long-term drought, and further holistic research on this plant may serve to produce biotechnological solutions for crop production under the current scenario of climatic emergency.

Mulching impact of Jatropha curcas L. leaves on soil fertility and yield of wheat under water stress

In present studies we have evaluated mulching impact of Jatropha curcas leaves on soil health and yield of two wheat (Triticum aestivum L.) varieties Wadan-2017 (rainfed) and Pirsabak-2013 (irrigated) under imposed water stress. Mulch of Jatropha leaves was spread on the soil surface at the rate of 0, 1, 3 and 5 Mg ha−1 after seed germination of wheat. Water stress was imposed by skipping irrigations for one month at anthesis stage of wheat maintaining 40% soil field capacity. We found a significant decline in soil microbial biomass carbon (30.27%), total nitrogen (22.28%) and organic matter content (21.73%) due to imposed water stress in non-mulch plots. However, mulch application at 5 Mg ha−1 significantly improved soil organic matter (38.18%), total nitrogen (37.75%), phenolics content (16.95 mg gallic acid equivalents/g) and soil microbial biomass carbon (26.66%) as compared to non-mulch control. Soil health indicators like soil carbonates, bicarbonates, electrical conductivity, chloride ions and total dissolved salts were decreased by 5 Mg ha−1 mulch application. We noted a decline in yield indicators like spike weight (14.74%), grain spike−1 (7.02%), grain length (3.79%), grain width (3.16%), 1000 grains weight (6.10%), Awn length (9.21%), straw weight (23.53%) and total grain yield (5.98%) of wheat due to imposed water stress. Reduction in yield traits of wheat due to water stress was higher in Pirsabak-2013 than Wadan-2017. Jatropha leaves mulch application at 5 Mg ha−1 significantly minimized the loss in yield traits of wheat crop caused by water stress. Jatropha curcas leaves mulch application at 5 Mg ha−1 is recommended for the successful establishment of wheat crop under water deficit conditions.

Biochar derived from hazelnut shells mitigates the impact of drought stress on soybean seedlings

ABSTRACT This study investigated the interactive effects of drought stress with biochar on plant growth, the physiological and biochemical attributes of soybean seedlings. A pot trial tested the effect of amending a loamy sandy soil with biochar at three doses: 0%, 3% and 6% in the alleviation of drought stress, imposed by adjusting soil moisture content at three levels (in terms of soil field capacity, FC): 100% FC, 75% FC and 50% FC. Water deficit negatively influenced the growth of soybean seedlings and chlorophyll content of leaves, particularly in non-amended plants whereas biochar amendment boosted the growth and chlorophyll content, particularly under drought stress. Drought stress elevated malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, sucrose and abscisic acid (ABA) contents as well as the antioxidant enzyme activity [peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD)] of soybean leaves but reduced the contents of indole acetic acid (IAA) and gibberellic acid (GA); biochar amendment counteracted the impact of drought. The findings of the study indicate that biochar amendment can enhance soybean growth by modulating the plant physiology and biochemistry under drought stress.

The Effect of Moringa oleifera Lam. Leaf Aqueous Extract on Seed Yield and Fibre Quality of Linseed under Water Deficit Stress

Moringa oleifera leaf extract contains active ingredients with stimulatory effects on natural processes of plants like uptake of nutrients, photosynthesis, biomass production and flowering. Therefore, we conducted field experiments to determine the effects of M. oleifera leaf aqueous extract (MLAE) on growth and fibre quality of three linseed varieties viz. Roshni, BL1 and Chandni under water deficit stress for two years. Water deficit stress was imposed during tillering growth phase (60 days after sowing) by skipping four irrigations, keeping 40% soil field capacity. The MLAE (5%) was applied to leaves once before the start of water deficit stress period and next 15 days after imposition of water deficit stress. Analysis of MLAE showed the presence of natural phenolics (150 mg gallic acid equivalents (GAE)/mL extract) and essential nutrients like Ca, Mg, K, Zn, Mn, and Fe. Positive impact of the MLAE was observed on plant height, tillers production, leaf chlorophyll pigments, phenolics content, sugars content, seed yield and fibre quality of linseed both under non-stress and water deficit stress. Our studies concluded that MLAE can be a probable approach for maintaining normal growth and fibre quality of linseed plants under short supply of water.