Major nutrient management systems for rice-wheat cropping were compared for their potential to credit organic carbon (C) to the soil, its fractionation into active (very labile, VLc; labile, Lc) and ...passive (less labile, LLc; non-labile, NLc) pools, and crop yield responses. A ten-year long experiment was used to study effects of: (i) no inputs (Control, O), (ii) 100% inorganic fertilizers (F) compared to reduced fertilizers inputs (55%) supplemented with biomass incorporation from (iii) opportunity legume crop (Vigna radiata) (LE), (iv) green manure (Sesbania aculeata) (GM), (v) farmyard manure (FYM), (vi) wheat stubble (WS), and (vii) rice stubble (RS). Maximum C input to soil (as the percentage of C assimilated in the system) was in GM (36%) followed by RS (34%), WS (33%), LE (24%), and FYM (21%) compared to O (15%) and F (15%). Total C input to soil had a direct effect on soil C stock, soil C fractions (maximum in VLc and LLc), yet the responses in terms of biological yield were controlled by the quality of the biomass (C:N ratio, decomposition, etc.) incorporated. Legume-based biomass inputs accrued most benefits for soil C sequestration and biological productivity.
Mungbean is a relatively drought tolerant leguminous crop with a short life cycle. Using leaf water loss (LWL) as a screen for drought tolerance, two mungbean genotypes exhibiting more than two–fold ...variation in leaf water loss were explored for the genetic variation in their physiological and molecular responses to drought. Efficient stomatal regulation together with better photosynthetic capacity constituted an important trait combination for drought adaptation in water saving low LWL genotype. The stomatal closure under drought was accompanied with a concomitant down-regulation of farnesyl transferase gene. However, cooler canopy temperature, a well branched root system coupled with a relatively higher proline accumulation in water spending high LWL genotype constituted another set of adaptive traits operating when exposed to deficit soil moisture conditions. We report drought induced down-regulation of proline dehydrogenase and the presence of 118 base pair intron in this gene. The high seed yield of low LWL genotype despite a hotter canopy might be attributed to higher net assimilation and quantum yield recorded under drought in this genotype. Thus, these interlinked features contribute to adaptive mechanisms of mungbeans which is widely grown in harsh environments exposed to drought and high temperatures.
Symbiotic effectiveness of rhizobitoxine (Rtx)-producing strains of Bradyrhizobium spp. in soybean (cultivar NRC-37/Ahilya-4) under limited soil moisture conditions was evaluated using phenomics ...tools such as infrared(IR) thermal and visible imaging. Red, green and blue (RGB) colour pixels were standardized to analyse a total of 1017 IR thermal and 692 visible images. Plants inoculated with the Rtx-producing strains B. elkanii USDA-61 and USDA-94 and successive inoculation by B. diazoefficiens USDA-110 resulted in cooler canopy temperatures and increased canopy greenness. The results of the image analysis of plants inoculated with Rtx-producing strains were correlated with effective nodulation, improved photosynthesis, plant nitrogen status and yield parameters. Principal component analysis (PCA) revealed the reliability of the phenomics approach over conventional destructive approaches in assessing the symbiotic effectiveness of Bradyrhizobium strains in soybean plants under watered (87.41-89.96%) and water-stressed (90.54-94.21%) conditions. Multivariate cluster analysis (MCA) revealed two distinct clusters denoting effective (Rtx) and ineffective (non-Rtx) Bradyrhizobium inoculation treatments in soybean. Furthermore, correlation analysis showed that this phenotyping approach is a dependable alternative for screening drought tolerant genotypes or drought resilience symbiosis. This is the first report on the application of non-invasive phenomics techniques, particularly RGB-based image analysis, in assessing plant-microbe symbiotic interactions to impart abiotic stress tolerance.
Background:
Peninsular India, being completely under the influence of monsoonal climate, suffers crop yield variability due to rainfall distribution-induced soil moisture constraints. Timely and ...appropriate assessment of this rainfall and soil moisture-induced crop yield variability serves as a key for exemplary relief assistance. Per cent available soil moisture (PASM) is one among several drought declaration indices followed by stakeholders in India for declaration of drought, needs re-evaluation as the existing criteria in unable to capture the yield loss due to ineffective classification of PASM categories. This study attempts to revise the agricultural drought classes by PASM based on relationships established between yield of major rainfed crops of the study region and PASM.
Methods:
Analysis of yield variability due to PASM was carried out based on long term observations in experiments conducted at five dry farming locations (Akola, Parbhani, Kovilpatti, Ananthapuramu and Bengaluru) of peninsular India. The average yield for each category of PASM was calculated and tabulated for regression analysis. The PASM
versus
yield in each group was correlated and regression equations were developed if significant positive correlations were established.
Results:
The range of available soil moisture to obtain at least 50 percent of optimum yield in cereals (maize: 26 and finger millet: 52.9 PASM), pulses (pigeon pea: 37.2 PASM), oilseeds (soybean: 26.8 to 30.5, groundnut: 53.8 to 61.7 PASM) and commercial crops (cotton: 26.3 PASM) was 26–61 percent.
Conclusion:
The revised PASM-based drought classes (0–50 severe; 51–75 mild and 76–100 no drought) would help in drought declaration and precise identification of drought-hit areas for meaningful relief assistance. However, there is further investigation is needed to include a soil component for further fine-tuning of the criteria.
Degradation of soils due to sodification is now widespread in arid and semiarid areas irrigated with groundwater having residual alkalinity. We monitored the changes in soil physical, chemical, and ...hydraulic characteristics of a sandy loam soil irrigated for the last two decades with two types of alkali waters (AW1, AW2) having similar salts (total electrolyte concentration, TEC=30 me L−1) and sodium adsorption ratio (SARiw 10 mmol L−1) but varying in residual sodium carbonate, RSC (5 me L−1 in AW1 and 10 me L−1 in AW2), and when latter irrigation water (AW2) was ameliorated to neutralize RSC equivalent to 5 me L−1 with either sulfuric acid (AW2 +SA) or gypsum (AW2 +GYP). Deterioration of overall soil quality was evidenced by increased bulk density and penetration resistance, decreased aggregate stability, increased soil pH and sodicity, and decline in accumulation of soil organic carbon, especially with AW2. Exchangeable sodium percentage (ESP) build up ranged between 2.1 and 3.3 times SARiw. The steady infiltration rate (IR) in soil irrigated with good quality water, GQW (Electrical conductivity, ECiw=0.52dSm−1; RSC=1.2 me L−1), was 5.4 mm h−1 (IR-GQW) while it reduced to 2.2, 1.0, 1.7, and 1.8 mm h−1 with AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The adverse effects of soil sodification exacerbated with rainwater (RW; simulated with deionized water, EC <0.03dSm−1) infiltration, further reducing the IR to 1.1, 0.7, 1.4, and 1.0 mm h−1 for AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The recovery of IR was only a little (2–11%) when RW was replaced with respective irrigation waters, even when the surface 5 cm was tilled to break soil crusts (ST). This indicates permanent damage to soil structure and water transmission characteristics through the development of sub-soil throttles with moved-in clays. Power functions described the surface soil ESP to control IR (R2 =0.53–0.83 **), and the ESP values for 0.25 IR-GQW were 24.5, 15.8, 17.4, 14.5 and 14.4 for IW (respective irrigation waters), RW, IW-RW, RW-IW, and RW-IW-ST-IW sequences of infiltration events, respectively. There were considerable reductions in post-infiltration water storage in the soil profile, and a slowed down redistribution of infiltrated water were also observed. The neutralization of RSC with either sulfuric acid or gypsum improved the hydro-physical properties; the impact of gypsum being slightly better especially in improving soil stability characteristics.
•Irrigation waters with residual alkalinity cause irreversible soil degradation.•2-decades of alkali water irrigation resulted in impaired hydraulic properties.•Rainwater infiltration rates (IR) were lower than alkali water infiltration rates.•Improvements in hydro-physical properties with sulfuric acid & gypsic amendments.•Impact of gypsum better than sulfuric acid for sodicity hazard and soil stability.
Exogenous applications of plant growth regulators (PGRs) were evaluated for their effects on growth, physiological attributes, and yield of sodicity stressed paddy during 2018 and 2019. Crop was ...grown in fixed lysimeters enduring sodicity stress due to long-term irrigation with two types of alkali waters having residual sodium carbonate RSC (AW
1
: 5 and AW
2
: 10 me/L), and latter (AW
2
) ameliorated to neutralize RSC equivalent to 5 me/L with either sulfuric acid or gypsum. Consequent losses in paddy yield with different alkalinity water irrigation ranged between 17–48% and 34–100% during 2018 and 2019, respectively. Each plot, receiving different alkalinity water irrigation, was further divided into four equal parts for evaluation of PGRs. PGRs included thio-urea (TU, 500 ppm), potassium nitrate (PN, 15 g/L), and combinations of TU + PN during 2018 while latter was replaced with salicylic acid (SA, 10 µM) in 2019. PGRs were sprayed four times, i.e., at tillering, maximum growth, panicle initiation to grain formation, and two days after 3rd spray. The increase in grain yield was equal to 14, 12, and 12% with TU, PN, and TU + PN during 2018 and 5–14% during 2019. PGRs triggered physiological attributes like photosynthetic rate, SPAD values, proline, membrane injury, malondialdehyde, and relative water content. Maas and Hoffman-type response functions showed that, at exchangeable sodium percentage (%) 30, the relative yields were 0.59, 0.53, and 0.49 under TU, PN, and control (No PGR), respectively. These results signify the agronomic usefulness of foliar spray of PGRs in improving paddy yield in the alkali groundwater irrigation-induced sodicity stress areas.
Graphical Abstract
The amelioration effect of water‐soluble vitamin pyridoxine against stress was evaluated in milkfish, Chanos chanos exposed to endosulfan. Two hundred and twenty‐five fish were distributed randomly ...into five treatments, each with three replicates. Four isocaloric and isonitrogenous diets with graded levels of pyridoxine feed were as follows: normal water and fed with control diet (En0/PY0); endosulfan‐treated water and fed with control diet (En/PY0); and endosulfan‐treated water and fed with 50 (En/PY 50 mg/kg), 75 (En/PY 75 mg/kg) and 100 mg/kg (En/PY 100 mg/kg) pyridoxine‐supplemented feed. The endosulfan in treated water was maintained at a level of 1/40th of LC50 (0.52 ppb). The effect of dietary pyridoxine supplementation was studied in terms of antioxidative enzymes (catalase, superoxide dismutase, glutathione‐S‐transferase), stress markers heat‐shock protein 70, caspase‐3, cortisol, acetylcholine esterase (AChE), blood glucose, immunohaematological parameters (total protein, albumin, globulin and A/G ratio, nitroblue tetrazolium, RBC, WBC, Hb), gill histopathology and a subsequent challenge study with Vibrio parahaemolyticus. The antioxidative enzymes, stress markers, albumin and A/G ratio were significantly (p < 0.01) elevated, brain AChE and immunohaematological parameters were significantly (p < 0.01) decreased, and chromosome aberration and gill histopathology were also altered due to endosulfan exposure. The relative survival % was reduced due to the combined effect of endosulfan stress and bacterial challenge. Fish fed the diet supplemented with pyridoxine at 75 and 100 mg/kg was found to restore the studied parameter towards normal compared with control and indicated protection against endosulfan‐induced stress significantly (p < 0.01). Results obtained in the present study indicate that the supplementation of 75 and 100 mg/kg of pyridoxine in the diet has a definitive role in the mitigation of the endosulfan‐induced stress in milkfish, C. chanos fingerlings.
An attempt was made to assess the effect of dietary pyridoxine supplementation on growth performance and cellular metabolic enzymes of Chanos chanos fingerlings under endosulfan induced stress. ...Two‐hundred and twenty‐five fish were randomly distributed into five treatments, each with three replicates and fed four isocaloric and isonitrogenous diets with graded levels of pyridoxine for 45 days. Endosulfan concentration in the water was maintained at sublethal level of 1/40th of 96 h LC50 (0.52 ppb). Dietary pyridoxine supplementation significantly enhanced growth performance viz. weight gain (%), specific growth rate, feed conversion ratio and protein efficiency ratio of fish compared to control diet fed group. The results of this experiment revealed that the activities of digestive and metabolic enzymes were significantly improved after feeding with dietary pyridoxine supplementation in C. chanos. Significantly increased muscle and brain ascorbic acid content was observed in fish fed diets containing pyridoxine. Histological studies on liver of fish fed pyridoxine‐supplemented diet showed the normal architecture of hepatocytes compared to non‐pyridoxine fed group. The results obtained in this study revealed that the inclusion of pyridoxine in diet has a protective effect against endosulfan induced stress in C. chanos fingerlings through metabolic enzyme activities and vitamin C content. This study has a potential in ameliorating the toxic effect of endosulfan induced stress using dietary supplementation of pyridoxine.
Root-tissue colonizing bacteria demonstrated with multiple PGP traits from sorghum plants were identified as
Ochrobactrum
sp. EB-165,
Microbacterium
sp. EB-65,
Enterobacter
sp. EB-14 and
Enterobacter ...cloacae
strain EB-48 on the basis of 16S rRNA gene sequencing. Here, the in vivo experiments using ½-MS media and ½-MS media + 15% PEG 8000 (for inducing drought stress) indicated stress tolerance imparting ability of these rhizobacterial endophytes in a non-stay green and senescent genotype (R-16) of sorghum. In the experiment with sterile soilrite mix base, seed bacterization with these isolates showed improved plant growth specifically the roots, in terms of root length (~ 44.2 to 50.8% over controls), root dry weight (~ 91.3 to 99.8% over controls) and root surface area (~ 1 to 1.5 fold over controls) under drought stress. Rhizobacterial endophytes were successful, not only in providing better cellular osmotic adjustment in leaves (≥ 1-fold increase in proline accumulation over controls), but favorable physiological responses like Relative Water Content (RWC) and cell Membrane Stability Index (MSI) in the inoculated plants during the drought stress induction. Up-regulation of drought responsive genes like
sbP5CS2
and
sbP5CS1
was observed in these endophytes-treated plants as compared to untreated control and
Escherichia coli
DH5α (negative control)-treated plants. Interestingly, the stress imparting traits of rhizobacterial endophytes, including up-regulation of specific genes, were observed during sorghum seedling growth only under drought stresses. The results of this study lead to the conclusion that the potential endophytic rhizobacterial interactions can contribute to plant growth promotion as well as induced stress tolerance in sorghum.
Purpose
Soil sodification through irrigation with alkali groundwater is quite extensive in arid to semi-arid regions of the world. Therefore, the long-term effects of alkali and partially neutralized ...water irrigations were quantified on sandy loam soils.
Methods
The experiment was conducted in semi-controlled concrete lysimeters of 2 × 2 × 2 m
3
with drainage outlets at bottom and filled with sandy loam soils. These were irrigated with five types of irrigation water, i.e. good quality water (GQW), synthetic alkali water (SAW) having the residual sodium carbonate (RSC) ~ 5 me L
−1
(SAW
1
), SAW of RSC ~ 10 me L
−1
(SAW
2
), SAW
2
partially neutralized up to RSC ~ 5 me L
−1
with gypsum (SAW
2
+ GYP) and SAW
2
partially neutralized up to RSC ~ 5 me L
−1
with sulphuric acid (SAW
2
+ SA).
Results
Perpetual irrigation with residual alkalinity water deteriorated soil quality through increasing its soil pH, electrical conductivity and total inorganic carbon content and diminishing soil microbial activities, total organic carbon (TOC) and its active pools. Increased soil pH further induced negative effect on soil microbial activities and TOC as well as its active pool. Conversely, availability of phosphorous and potassium increased but nitrogen availability remained unaffected.
Conclusions
Irrigation with increasing RSC water caused proportionate deterioration in soil quality. Partial neutralization of irrigation water RSC from ~ 10 to ~ 5 me L
−1
with gypsum or sulphurous amendments did not suffice for sustaining long-term soil quality. It suggested substantial revision in existing recommendation of alkali water neutralization for irrigation to achieve the land degradation neutrality, food security and sustainability.
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