Climate change is a critical yield–limiting factor that has threatened the entire global crop production system in the present scenario. The use of biostimulants in agriculture has shown tremendous potential in combating climate change–induced stresses such as drought, salinity, temperature stress, etc. Biostimulants are organic compounds, microbes, or amalgamation of both that could regulate plant growth behavior through molecular alteration and physiological, biochemical, and anatomical modulations. Their nature is diverse due to the varying composition of bioactive compounds, and they function through various modes of action. To generate a successful biostimulatory action on crops under different parameters, a multi–omics approach would be beneficial to identify or predict its outcome comprehensively. The ‘omics’ approach has greatly helped us to understand the mode of action of biostimulants on plants at cellular levels. Biostimulants acting as a messenger in signal transduction resembling phytohormones and other chemical compounds and their cross–talk in various abiotic stresses help us design future crop management under changing climate, thus, sustaining food security with finite natural resources. This review article elucidates the strategic potential and prospects of biostimulants in mitigating the adverse impacts of harsh environmental conditions on plants.

Conventionally tilled maize–wheat cropping system (MWCS) is an emerging cereal production system in semi-arid region of south-Asia. This system involves excessive tillage operations that result in numerous resource- and production-vulnerabilities besides impeding environmental-stresses. Likewise, phosphorus is a vital nutrient that limits crop growth and development. It’s a matter of great concern when ∼80% of Indian soils are low to medium in available-P due to its sparing solubility, resulting in crop stress and low yields. Hence, crop productivity, photosynthetic parameters and resilience to nutritional and environmental stresses were assessed in a MWCS using four crop-establishment and tillage management (CETM) practices [FBCT-FBCT (Flat bed-conventional tillage both in maize and wheat); RBCT-RBZT (Raised bed-CT in maize and raised bed-zero tillage in wheat); FBZT-FBZT (FBZT both in maize and wheat); PRBZT-PRBZT (Permanent raised bed-ZT both in maize and wheat)], and five P-fertilization practices [P₁₀₀(100% soil applied-P); P₅₀+2FSP (50% soil applied-P + 2 foliar-sprays of P through 2% DAP both in maize and wheat); P₅₀+PSB+AM-fungi; P₅₀+PSB+AMF+2FSP; and P₀(100% NK with no-P)] in split-plot design replicated-thrice. The results indicated that double zero-tilled PRBZT–PRBZT system significantly enhanced the grain yield (6.1; 5.4 t ha^–1), net photosynthetic rate (Pn) (41.68; 23.33 μ mol CO₂m^–2s^–1), stomatal conductance (SC) (0.44; 0.26 mol H₂O m^–2s^–1), relative water content (RWC) (83.3; 77.8%), and radiation-use efficiency (RUE) (2.9; 2.36 g MJ^–1) by 12.8–15.8 and 8.5–44.4% in maize and wheat crops, respectively over conventional tilled FBCT–FBCT. P₅₀+PSB+AMF+2FSP conjugating soil applied-P, microbial-inoculants and foliar-P, had significantly higher Pn, SC, RUE and RWC over P₁₀₀besides saving ∼34.7% fertilizer-P under MWCS. P₅₀+PSB+AMF+2FSP practice also had higher NDVI, PAR, transpiration efficiency and PHI over P₁₀₀. Whereas lower stomatal limitation index (Ls) was observed under PRBZT–PRBZT system as compared to the conventional FBCT–FBCT system indicating that P is the limiting factor but not stomata. Hence, optimum P supply through foliar P-fertilization along with other sources resulted in higher grain yield by 21.4% over control. Overall, double zero-tilled PRBZT–PRBZT with crop residue retention at 6 t/ha per year, as well as P₅₀+PSB+AMF+2FSP in MWCS, may prove beneficial in enhancing the crop productivity and, thereby, bolstering food security in semi-arid south-Asia region.

Field experiments were conducted with rapeseed (cv.TS-38) for three consecutive rabi seasons of the year 2014–2017 at the Instructional-cum-Research farm of Assam Agriculture University, Jorhat. Results revealed that different levels of sulfur and boron and their combinations had significant influence on seed and stover yields of rapeseed. The highest seed and stover yields were registered in interaction effect of B and S at 20 kg S/ha + 1.5 kg B/ha which was closely followed by interaction effect of B and S at 30 kg S/ha + 1.5 kg B/ha. The highest total uptake of N and B was noted under 30 kg S/ha + @ 1.5 kg B/ha. The highest total S uptake was noted under application of 20 kg S/ha + @ 1.5 kg B/ha. Partial factor productivity of N, P and K increased with subsequent increase in levels of S and B up to 20 kg S/ha and 1.5 kg B/ha, respectively. The highest values of agronomic use efficiency and apparent recovery of S and B were registered under 10 kg S/ha and 0.5 kg B/ha, respectively. The highest values of physiological use efficiency of S and B were registered under 20 kg S/ha and 0.5 kg B/ha, respectively. Interaction effect of S and B at 30 kg S/ha + 1.0 kg B/ha (S30B1.0) improved the oil content to the tune of 35.6%, registering an improvement of 13.4% over the control. The same interaction resulted in enhancement of protein content up to 22.9% over the 19.8% (control) wherein 15.6% increase over the control was noticed. Multiple stepwise regressions exercised on the different nutrient uptakes showed that nitrogen content in seed contributed the most in augmenting the biological yield of rapeseed followed by phosphorus and sulfur.

A field experiment was conducted at Horticultural Experimental Farm, Assam Agricultural University, Jorhat during the year 2015–17 to assess the impact of boron fertilization on dynamics of boron fractions in soil and crop yields in cauliflower–cowpea–okra cropping sequence. Five levels of boron (0, 0.5, 1.0, 1.5 and 2.0 kg ha⁻¹) along with the recommended dose of NPK fertilizer were applied in soil in cauliflower once in each 2 years (2015–17) of experimentation to assess the direct effect of boron fertilization, while cowpea and okra were grown as a suceeding test crop to study the residual effects of boron fertilization in the cropping sequence. Among the different levels of boron, the highest content of all the boron fractions in soil was recorded at rate of 2 kg B ha⁻¹ at different crop growth stages for all the three crops. Progressive decrease in content of all the boron fractions with crop ageing was noticed. The content of different boron fractions in soil follows the order readily soluble boron (RSB)<oxide bound boron (OXB)<organic bound boron (ORBB)<specifically adsorbed boron (SAB) <residual boron, respectively. The boron level of 2 kg B ha⁻¹ was found to prominent in increasing the yield in all the crops. In respect of contributions of different boron fractions to yield of crops, oxide bound boron(2.10) was found to be the highest contributor of cauliflower yield, while the residual boron (1.10), contributed the highest to cowpea yield and organic bound boron fraction (1.24) was found to be most prominent contributor of boron in leveraging okra yield.