Evaluating short-term effects of rice straw management on carbon fractions, composition and stability of soil aggregates in an acidic red soil with a vegetable planting history.

Red soils are characterised by acidic pH and limitations in carbon, nitrogen, water, and soil structure. To overcome such limitations, improved soil aggregation is the key to improving the physical and chemical properties of soil. Applying organic amendments such as straw can lead to corresponding soil aggregation and stability changes. Therefore, we explored the short-term effects of rice straw amendment, either alone or in combination with biochar, on improving the carbon fractions, stability, and composition of soil aggregates in red soil with a history of vegetable planting. The study consisted of four treatments: control (no organic material, CK), biochar alone (5% homemade straw biochar, B), straw alone (12% rice straw, S), and biochar with straw (5% homemade straw biochar + 12% rice straw, BS). Our results showed that equal amounts of straw and biochar substantially reduced the number of mechanically stable aggregates (MSA), mean weight diameter (MWD), and geometric mean diameter (GMD) of the soil. BS treatment reduced >0.25 mm aggregate content (R0.25), MWD and GMD by 24.06%, 56.81%, and 62.19%, respectively, compared with that of the control. The addition of straw greatly enhanced the water-stable macromolecular content and stability coefficient of the soil, but treatment B had no obvious effect. The S treatment had the greatest effect on R0.25, MWD and GMD, increasing them by 143.94%, 246.67%, and 181.82%, respectively, compared with that of the control. Soil organic carbon (SOC) was significantly increased by straw addition and carbonisation treatment, and the effect of the BS treatment was the best, with an increase of 325.63% compared with that of the control. The organic carbon content in the aggregates of different particle sizes treated with different organic materials also increased significantly. In the soil reactive organic carbon fraction, applying biochar alone did not affect microbial biomass carbon (MBC), dissolved organic carbon (DOC), or easily oxidized organic carbon (EOC) but could increase the particulate organic carbon (POC) content. All the treatments with straw application significantly increased the MBC, DOC, EOC, and POC content, and the highest effect was obtained by applying both straw and biochar in an integrated form, i.e., the BS treatment. In conclusion, the co-application of biochar and straw sequestered more carbon and revamped soil C pools than either biochar or straw alone and could be a promising option for the sustainable use of red soils to ameliorate the aforementioned limitations associated with this soil type.

Thiourea improves yield and quality traits of Brassica napus L. by upregulating the antioxidant defense system under high temperature stress.

High temperature stress influences plant growth, seed yield, and fatty acid contents by causing oxidative damage. This study investigated the potential of thiourea (TU) to mitigate oxidative stress and restoring seed oil content and quality in canola. The study thoroughly examined three main factors: (i) growth conditions-control and high temperature stress (35 °C); (ii) TU supplementation (1000 mg/L)-including variations like having no TU, water application at the seedling stage, TU application at seedling stage (BBCH Scale-39), water spray at anthesis stage, and TU application at anthesis stage (BBCH Scale-60); (iii) and two canola genotypes, 45S42 and Hiola-401, were studied separately. High temperature stress reduced growth and tissue water content, as plant height and relative water contents were decreased by 26 and 36% in 45S42 and 27 and 42% Hiola-401, respectively, resulting in a substantial decrease in seed yield per plant by 36 and 38% in 45S42 and Hiola-401. Seed oil content and quality parameters were also negatively affected by high temperature stress as seed oil content was reduced by 32 and 35% in 45S42 and Hiola-401. High-temperature stress increased the plant stress indicators like malondialdehyde, H2O2 content, and electrolyte leakage; these indicators were increased in both canola genotypes as compared to control. Interestingly, TU supplementation restored plant performance, enhancing height, relative water content, foliar chlorophyll (SPAD value), and seed yield per plant by 21, 15, 30, and 28% in 45S42; 19, 13, 26, and 21% in Hiola-401, respectively, under high temperature stress as compared to control. In addition, seed quality, seed oil content, linoleic acid, and linolenic acid were improved by 16, 14, and 22% in 45S42, and 16, 11, and 23% in Hiola-401, as compared to control. The most significant improvements in canola seed yield per plant were observed when TU was applied at the anthesis stage. Additionally, the research highlighted that canola genotype 45S42 responded better to TU applications and exhibited greater resilience against high temperature stress compared to genotype Hiola-401. This interesting study revealed that TU supplementation, particularly at the anthesis stage, improved high temperature stress tolerance, seed oil content, and fatty acid profile in two canola genotypes.

nirS and nosZII bacterial denitrifiers as well as fungal denitrifiers are coupled with N2O emissions in long-term fertilized soils.

Fertilizer application plays a critical role in soil fertility and crop yield and has been reported to significantly affect soil denitrification. However, the mechanisms by which denitrifying bacteria (nirK, nirS, nosZI, and nosZII) and fungi (nirK and p450nor) affect soil denitrification are poorly understood. Therefore, in this study, we investigated the effect of different fertilization treatments on the abundance, community structure, and function of soil denitrifying microorganisms in an agricultural ecosystem with long-term fertilization using mineral fertilizer or manure and their combination. The results showed that the application of organic fertilizer significantly increased the abundance of nirK-, nirS-, nosZI-, and nosZII-type denitrifying bacteria as the soil pH and phosphorus content increased. However, only the community structure of nirS- and nosZII-type denitrifying bacteria was influenced by the application of organic fertilizer, which led to a higher contribution of bacteria to nitrous oxide (N2O) emissions than that observed after inorganic fertilizer application. The increase in soil pH reduced the abundance of nirK-type denitrifying fungi, which may have presented a competitive disadvantage relative to bacteria, resulting in a lower contribution of fungi to N2O emissions than that observed after inorganic fertilizer application. The results demonstrated that organic fertilization had a significant impact on the community structure and activity of soil denitrifying bacteria and fungi. Our results also highlighted that after organic fertilizer application, nirS- and nosZII-denitrifying bacteria communities represent likely hot spots of bacterial soil N2O emissions while nirK-type denitrifying fungi represent hot spots for fungal soil N2O emissions.

Organic Amendments Improved the Productivity and Bio-Fortification of Fine Rice by Improving Physiological Responses and Nutrient Homeostasis under Salinity Stress.

Salinity stress (SS) is major abiotic stress that is seriously limiting crop production across the globe. The application of organic amendments (OA) mitigate the effects of salinity and improves soil health and crop production on a sustainable basis. However, limited studies are conducted to determine the impact of farmyard manure (FYM) and press mud (PM) on the performance of rice crop. Therefore, we performed this study to determine the impacts of FYM and PM on the growth, physiological and biochemical attributes, yield, and grain bio-fortification of rice crop under SS. The experiment was comprised of SS levels; control, 6 and 12 dS m-1 SS and OA; control, FYM: 5%, press mud 5% and combination of FYM (5%) + PM (5%). Soil salinity imposed deleterious impacts on the growth, yield, and grain quality of rice, however, OA appreciably offset the deleterious impacts of SS and improved the growth, yield, and grain bio-fortification of rice crop. The combined application of FYM + PM improved the growth and yield of rice through an increase in chlorophyll contents, leaf water contents, anti-oxidant activities (ascorbate peroxidise: APX; catalase: CAT, peroxidise: POD and ascorbic acid: AsA), K+ accumulation and decrease in Na+/K+ ratio, electrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H2O2), Na+ accumulation. Moreover, the combined application of FYM + PM significantly improved the grain protein (5.84% and 12.90%), grain iron (40.95% and 42.37%), and grain zinc contents (36.81% and 50.93%) at 6 and 12 dS m-1 SS. Therefore, this study suggested that the application of FYM and PM augmented the growth, yield, physiology, biochemistry, and grain bio-fortification of rice and proved to be a good practice for better rice production in salt-affected soils.

Sulfur Enhancement for the Improvement of Castor Bean Growth and Yield, and Sustainable Biodiesel Production.

Due to limited conventional energy sources, there is a need to find substitute non-conventional sources of energy to meet the societal demands on a sustainable basis. Crude oil and edible oil remain major import items in Pakistan, the deficit of which can be compensated by using biomass, preferably inedible oilseeds. Therefore, the current study evaluated the role of sulfur (S) fertilization for improving yield (seed and oil) and biodiesel value of castor bean, a potential inedible crop with minimum input requirements. For this purpose, a combined approach of field experimentation and laboratory analysis was conducted to explore the potential of two castor bean cultivars (DS-30 and NIAB Gold) against four S supply rates, namely, 0, 20, 40, and 60 kg S ha-1, in terms of growth, phenology, and yield parameters. Subsequently, the obtained seed samples were analyzed for biodiesel-related parameters in the Bio-analytical Chemistry lab, Punjab Bio-energy Institute, Faisalabad. The incremental S rates increased the seed yield for both cultivars, and the highest yield was recorded at 60 kg S ha-1 for NIAB Gold. For NIAB Gold, the oil content increased by 7% with S fertilization at 60 kg ha-1, and for DS-30, the oil content increased by 6% at 60 kg ha-1. As with incremental S fertilization, the oil yield increased on a hectare basis, and the quantity of biodiesel produced also increased. Importantly, the tested quality parameters of biodiesel, except biodiesel viscosity, were in the ASTM standard range. Overall, it has been concluded that castor bean is a promising and sustainable option for producing biodiesel as it is non-competitive to food crops and requires little input.

Management Strategies to Mitigate N2O Emissions in Agriculture.

The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30-40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management.

Bio-diesel production of sunflower through sulphur management in a semi-arid subtropical environment.

Energy security is a prime focus of policy makers to support agriculture, industrialisation, and transportation. Due to limited conventional energy sources, there is a need to harness non-conventional energy sources. In this regard, one of the proposed approaches is using biomass (e.g. energy crops) to produce biofuel-a renewable source of energy. Sunflower has several agronomic features to be exploited for a renewable, non-conventional, and environment-friendly source of bioenergy. Sulphur (S) fertilisation holds key for realising sunflower potential for seed and oil yield. In response to variable S supply rates, here we compared and quantified sunflower yield (seed, oil, and biodiesel) and biodiesel quality according to the ASTM international standards. We used a combined approach of field experimentation and rigorous lab analysis. Firstly, in a field experiment laid out in randomised complete block design with split-plot arrangement, response of two local sunflower hybrids (FH-331 and FH-689) to four S supply rates (0, 25, 50, 75 kg S ha-1) was evaluated in terms of agronomic traits. Experimental data showed that fertilisation of S significantly influenced growth and yield (seed, oil) traits; the response was different between two hybrids which also interacted with S supply rate. FH-331 recorded the highest achene yield at S fertilisation of 75 kg S ha-1, whereas FH-689 recorded the highest achene yield at 50 kg ha-1; achene yield of FH-331 was 13.6% higher than FH-689. Compared to control, S at 75 kg S ha-1 increased oil yield of FH-331 by 22% whereas S at 50 kg ha-1 increased oil yield by 23% of FH-689. Seed samples were analysed for different biodiesel quality parameters. The ranges of all quality parameters of sunflower biodiesel such as viscosity, calorific values, acid value, iodine value, saponification value, cetane number, and pour point were in ASTM standard range. We conclude that sunflower is a promising and sustainable option for producing biodiesel, the potential of which can be increased by optimal S management under field conditions.

Melatonin-Induced Protection Against Plant Abiotic Stress: Mechanisms and Prospects.

Global warming in this century increases incidences of various abiotic stresses restricting plant growth and productivity and posing a severe threat to global food production and security. The plant produces different osmolytes and hormones to combat the harmful effects of these abiotic stresses. Melatonin (MT) is a plant hormone that possesses excellent properties to improve plant performance under different abiotic stresses. It is associated with improved physiological and molecular processes linked with seed germination, growth and development, photosynthesis, carbon fixation, and plant defence against other abiotic stresses. In parallel, MT also increased the accumulation of multiple osmolytes, sugars and endogenous hormones (auxin, gibberellic acid, and cytokinins) to mediate resistance to stress. Stress condition in plants often produces reactive oxygen species. MT has excellent antioxidant properties and substantially scavenges reactive oxygen species by increasing the activity of enzymatic and non-enzymatic antioxidants under stress conditions. Moreover, the upregulation of stress-responsive and antioxidant enzyme genes makes it an excellent stress-inducing molecule. However, MT produced in plants is not sufficient to induce stress tolerance. Therefore, the development of transgenic plants with improved MT biosynthesis could be a promising approach to enhancing stress tolerance. This review, therefore, focuses on the possible role of MT in the induction of various abiotic stresses in plants. We further discussed MT biosynthesis and the critical role of MT as a potential antioxidant for improving abiotic stress tolerance. In addition, we also addressed MT biosynthesis and shed light on future research directions. Therefore, this review would help readers learn more about MT in a changing environment and provide new suggestions on how this knowledge could be used to develop stress tolerance.