(1) Background: Arid conditions occur due to climate abnormality in the different biogeography regions of the world. The aim of this research is to investigate the stoichiometry of manure and moisture regimes on soil properties, microbial biomass C:N:P turnover, and the grain yield of mustard crops under stress in arid conditions; (2) Methods: The field experiment was carried out for 2 years at the farms of the agriculture college of SKN, Jobner (SKRAU Bikaner, Rajasthan). The effects of organic manure, moisture regimes, and saline water treatment on soil properties, such as the soil microbial biomass build-up, loss, turnover, and recycling of carbon (C_mic), nitrogen (N_mic), and phosphorus (P_mic) in the mustard crop were investigated. The twenty-seven treatments studied are described as follows: organic manures (control, FYM @ 10 t ha⁻¹ and vermicompost @ 5 t ha⁻¹), moisture regimes (0.4, 0.6, and 0.8 IW/CPE ratio), and saline irrigation water (control, 6, 12 dSm⁻¹); (3) Results: Our findings indicate that vermicompost @ 5 t ha⁻¹ significantly increases moisture retention and the available water in soil at 33 kPa and 1500 kPa. The microbial biomass build-up of C_mic increases by 43.13% over the control and 14.36% over the FYM. Similarly, the soil microbial biomass of N_mic, and P_mic also increase considerably. The SHC of the soil is enhanced by the application of farmyard fertilizer and vermicompost. The BD and pH decrease significantly, while the SHC, OC, CEC, and ECe of the soil increase significantly. The build-up, losses, and fluxes of the soil microbial biomass of C_mic, N_mic, and P_mic increase significantly, and the turnover rate decreases under vermicompost @ 5 t ha⁻¹. A significant increase in grain yield was observed. Irrigation with a 0.8 IW/CPE moisture regime significantly decreases the pH of the SHC; (4) Conclusions: We hypothesized the interactive outcomes of the moisture regime and found that organic manure significantly influenced grain and stover yield. The treatments of quality irrigation water and the addition of organic manure are efficient enough to improve soil properties, water holding capacity, and soil microbial biomass C:N:P in stress climatic conditions.

Mentha longifolia is one of the important aromatic crop cultivated for its essential oil. The experiment was conducted to determine the effects of intermittent drought on the essential oil yield, composition, and nutrient status in M. longifolia. Initially, experimental plants were divided into two group: ‘irrigated’ and ‘drought’. The ‘irrigated group was watered normally, while the ‘drought’ group was not watered for seven days. Subsequently, both the groups were irrigated during the recovery period. Further, both groups were divided into two subgroups with non-irrigated and irrigated plants for seven days. In each cycle, samples were taken on 0, 7, 14, 21 days (first, second, and third cycle). Results indicated that the essential oil yield (ml/100- gram plant material) was increased under drought stress from 0.6 to a maximum of 0.9, while it showed a reduction in limonene, d-carvone percentage and percentage of nutrients (nitrogen and potassium) in the plants with non-significant change in phosphorous concentration. Also, the highest values of neodihydrocarveol (26.4%) and c-dihydrocarvone (11.43%) were determined by Gas Chromatography/Mass Spectrometry (GC/ MS) under third cycle. Our findings provide critical insights and directions for appropriate irrigation schedule so as to maximize the essential oil yield.

Salt stress adversely influences growth, development, and productivity in plants, resulting in a limitation on agriculture production worldwide. Therefore, this study aimed to investigate the effect of four different salts, i.e., NaCl, KCl, MgSO₄, and CaCl₂, applied at various concentrations of 0, 12.5, 25, 50, and 100 mM on the physico-chemical properties and essential oil composition of M. longifolia. After 45 days of transplantation, the plants were irrigated at different salinities at 4-day intervals for 60 days. The resulting data revealed a significant reduction in plant height, number of branches, biomass, chlorophyll content, and relative water content with rising concentrations of NaCl, KCl, and CaCl₂. However, MgSO₄ poses fewer toxic effects than other salts. Proline concentration, electrolyte leakage, and DPPH inhibition (%) increase with increasing salt concentrations. At lower-level salt conditions, we had a higher essential oil yield, and GC–MS analysis reported 36 compounds in which (−)-carvone and D-limonene covered the most area by 22%–50% and 45%–74%, respectively. The expression analyzed by qRT-PCR of synthetic Limonene (LS) and Carvone (ISPD) synthetic genes has synergistic and antagonistic relationships in response to salt treatments. To conclude, it can be said that lower levels of salt enhanced the production of essential oil in M. longifolia, which may provide future benefits commercially and medicinally. In addition to this, salt stress also resulted in the emergence of novel compounds in essential oils, for which future strategies are needed to identify the importance of these compounds in M. longifolia.

A genus of Monarda belongs to the family (Lamiaceae), the largest group of angiosperms. The crop has been grown extensively across the world for its flavoring and therapeutic properties as well as for its high-quality essential oil. The present research was designed to study the impact of different drying methods i.e (shed drying, sun-drying, microwave, oven-drying at (40°, 50°, and 60° C), freeze-drying (0°, -10°, and -20° C), and vacuum drying (30°, 45° and 60° C) on the qualitative and quantitative analysis of Monarda citriodora essential oil. Dried and fresh plant samples were hydro-distilled using the clevenger apparatus, and essential oil analyzed by Gas Chromatography (GC) and Gas Chromatography mass spectrophotoscopy (GC/MS). The results showed that different drying methods had significant effects on essential oil yield as shed-drying (2.6 ml) >freeze-drying (2.2 ml at 0°C) >oven drying (2.1 ml) >fresh drying (2.0 ml) >sun drying (2.0 ml) >microwave (0.15 ml). The major compounds obtained by GC/MS were thymol (92.46%) >g-terpinene (10.48%) >o-cymene (9.31%) >carvacrol (8.88%) >cyclohexene (3.51%). The highest essential oil yield was observed under shed dried (2.6 ml) and the major essential oil compound, thymol (92.46%), was observed under microwave-2 (4.0 min, 4.0 min, 4.0 min, and 3.0 min) combination. The results show an inversely proportional correlation between essential oil compounds. Thus, it has been summarized that the M. citriodora plant dry under the shed-drying method was the most appropriate and suitable method for obtaining a high-quality essential oil yield and microwave-2 (MV-2) combination for oil composition.