Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils.

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

Differential effects of sulfamethoxazole concentrations on the enzymatic dynamics of aerobic composting.

Enzymatic activities play an important role in the biological composting processing of agricultural wastes. This paper explores the effect of sulfamethoxazole (SMX) (Control, 25 mg/kg, 50 mg/kg, and 100 mg/kg) on the enzymatic activities of cellulase, protease, urease, and arylsulfatase. Compost samples were taken at three different intervals for analysis (day 0, day 25, and day 45). The findings revealed that at the start of the composting process, a strongly negative effect on enzymatic behavior was observed, and this response was significantly dependent on SMX concentrations (p < 0.05). The inhibition was consistent across all treatments. According to the results, the negative impact of SMX on community structure can result in selection pressure. Furthermore, all of the treatments had drastically improved enzymatic activity by the end of the composting process (day 45). This effect was presumably caused by the deterioration of SMX and a substantial stress reduction.

Thermal Stresses in Maize: Effects and Management Strategies.

Climate change can decrease the global maize productivity and grain quality. Maize crop requires an optimal temperature for better harvest productivity. A suboptimal temperature at any critical stage for a prolonged duration can negatively affect the growth and yield formation processes. This review discusses the negative impact of temperature extremes (high and low temperatures) on the morpho-physiological, biochemical, and nutritional traits of the maize crop. High temperature stress limits pollen viability and silks receptivity, leading to a significant reduction in seed setting and grain yield. Likewise, severe alterations in growth rate, photosynthesis, dry matter accumulation, cellular membranes, and antioxidant enzyme activities under low temperature collectively limit maize productivity. We also discussed various strategies with practical examples to cope with temperature stresses, including cultural practices, exogenous protectants, breeding climate-smart crops, and molecular genomics approaches. We reviewed that identified quantitative trait loci (QTLs) and genes controlling high- and low temperature stress tolerance in maize could be introgressed into otherwise elite cultivars to develop stress-tolerant cultivars. Genome editing has become a key tool for developing climate-resilient crops. Moreover, challenges to maize crop improvement such as lack of adequate resources for breeding in poor countries, poor communication among the scientists of developing and developed countries, problems in germplasm exchange, and high cost of advanced high-throughput phenotyping systems are discussed. In the end, future perspectives for maize improvement are discussed, which briefly include new breeding technologies such as transgene-free clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas)-mediated genome editing for thermo-stress tolerance in maize.

Potential Mechanisms of Abiotic Stress Tolerance in Crop Plants Induced by Thiourea.

Abiotic stresses, such as temperature extremes, drought, salinity, and heavy metals are major factors limiting crop productivity and sustainability worldwide. Abiotic stresses disturb plant growth and yield formation. Several chemical compounds, known as plant growth regulators (PGRs), modulate plant responses to biotic and abiotic stresses at the cellular, tissue, and organ levels. Thiourea (TU) is an important synthetic PGR containing nitrogen (36%) and sulfur (42%) that has gained wide attention for its role in plant stress tolerance. Tolerance against abiotic stresses is a complex phenomenon involving an array of mechanisms, and TU may modulate several of these. An understanding of TU-induced tolerance mechanisms may help improve crop yield under stress conditions. However, the potential mechanisms involved in TU-induced plant stress tolerance are still elusive. In this review, we discuss the essential role of TU-induced tolerance in improving performance of plants growing under abiotic stresses and potential mechanisms underlying TU-induced stress tolerance. We also highlight exploitation of new avenues critical in TU-induced stress tolerance.

Effects of increased levels of atmospheric CO2 and high temperatures on rice growth and quality.

The increased atmospheric temperatures resulting from the increased concentration of atmospheric carbon dioxide (CO2) have had a profound influence on global rice production. China serves as an important area for producing and consuming rice. Therefore, exploring the effects of the simultaneously rising levels of atmospheric CO2 and temperatures on rice growth and quality in the future is very important. The present study was designed to measure the most important aspects of variation for rice-related physiological, ecological and quality indices in different growing periods under a simultaneous increase of CO2 and temperature, through simulation experiments in climate-controlled growth chambers, with southern rice as the study object. The results indicated that the ecological indices, rice phenology, and leaf area would decrease under a simultaneous increase of CO2 and temperature. For the physiological indices, Malondialdehyde (MDA) levels increased significantly in the seedling period. However, it showed the trend of increase and subsequent decrease in the heading and filling periods. In addition, the decomposition of soluble protein (SP) and soluble sugar (SS) accelerated in filling period. The rice quality index of the Head Rice Rate showed the decreasing trend and subsequent increase, but the Chalky Rice Rate and Protein Content indices gradually decreased while the Gel Consistency gradually increased.

Exogenous application of plant growth regulators (PGRs) induces chilling tolerance in short-duration hybrid maize.

Chilling stress hampers the optimal performance of maize under field conditions precipitously by inducing oxidative stress. To confer the damaging effects of chilling stress, the present study aimed to investigate the effects of some natural and synthetic plant growth regulators, i.e., salicylic acid (SA), thiourea (TU), sorghum water extract (SWE), and moringa leaf extract (MLE) on chilling stress tolerance in autumn maize hybrid. Foliar application of growth regulators at low concentrations was carried out at six leaf (V6) and tasseling stages. An increase in crop growth rate (CGR), leaf area index (LAI), leaf area duration (LAD), plant height (PH), grain yield (GY), and total dry matter accumulation (TDM) was observed in exogenously applied plants as compared to control. In addition, improved physio-biochemical, phenological, and grain nutritional quality attributes were noticed in foliar-treated maize plots as compared to non-treated ones. SA-treated plants reduced 20% electrolyte leakage in cell membrane against control. MLE and SA were proved best in improving total phenolic, relative water (19-23%), and chlorophyll contents among other applications. A similar trend was found for photosynthetic and transpiration rates, whereas MLE and SWE were found better in improving CGR, LAI, LAD, TDM, PH, GY, grains per cob, 1000 grain weight, and biological yield among all treatments including control. TU and MLE have significantly reduced the duration in phenological events of crop at the reproductive stage. MLE, TU, and SA also improved the grain protein, oil, and starch contents as compared to control. Enhanced crop water productivity was also observed in MLE-treated plants. Economic analysis suggested that MLE and SA applications were more economical in inducing chilling stress tolerance under field conditions. Although eliciting behavior of all growth regulators improved morpho-physiological attributes against suboptimal temperature stress conditions, MLE and SA acted as leading agents which proved to be better stress alleviators by improving plant physio-biochemical attributes and maize growth.

Salicylic acid confers salt tolerance in potato plants by improving water relations, gaseous exchange, antioxidant activities and osmoregulation.

BACKGROUND: Potato is an important vegetable; however, salt stress drastically affects its growth and yield. A pot experiment was therefore conducted to assess salicylic acid efficacy in improving performance of potato cultivars, grown under salt stress (50 mmol L-1 ). Salicylic acid at 0.5 mmol L-1 was sprayed on to potato plants after 1 week of salinity application. RESULTS: Salt stress effects were ameliorated by salicylic acid effectively in both the studied cultivars. N-Y LARA proved more responsive to salicylic acid application than 720-110 NARC, which confirmed genetic variation between cultivars. Salicylic acid scavenged reactive oxygen species by improving antioxidant enzyme activities (superoxide dismutase, catalase, peroxidases) and regulating osmotic adjustment (proline, phenolic contents), which led to enhanced water relation and gaseous exchange attributes, and thereby increased potassium availability and reduced sodium content in potato leaves. Moreover, potato tuber yield showed a positive correlation with potassium content, photosynthesis and antioxidant enzyme activities. CONCLUSION: Salt tolerance efficacy of salicylic acid is authenticated in improving potato crop performance under salt stress. Salicylic acid effect was more pronounced in N-Y LARA, reflecting greater tolerance than 720-110 NARC, which was confirmed as a susceptible cultivar. Hence salicylic acid at 0.5 mmol L-1 and cultivation of N-Y LARA may be recommended in saline soil. © 2016 Society of Chemical Industry.