Melekote Nagabhushan Arun

Enhancing productivity through integrated and comprehensive nutrient management is pertinent to sustainable intensification of agricultural ecosystems. The utilization of marine bioactive stimulants has been gaining momentum and impetus in crop agricultural farming system due to their phytoelicitor activity. Liquids biostimulants derived from seaweed evoke defense responses in plants that contribute to resistance to abiotic stresses and challenges like high temperature, salinity, moisture stress, and cold. Seaweed extracts are immensely organic and suitable for growing crops that are both organic and environmentally friendly. Seaweeds provide an abundant source of natural growth substances that can be employed to enhance plant growth. Seaweeds are one of the most significant marine resources of the world, and derived compounds have been extensively used as amendments in crop production systems due to the presence of macronutrients such as Ca, K, and P and micronutrients like Fe, Cu, Zn, B, Mn, Co, and Mo, presence of several plant growth stimulating compounds including cytokinin, auxins, gibberellins, and betaines which are essential for plant growth and development. The purpose of the current chapter is to explore the functional and growth characteristics induced by seaweed extracts in addition to their modes and mechanisms of action in rice crops, which are responsible for elicitor and phytostimulatory activities and boost in grain production and nutrient usage efficiency.

A species is considered to be invasive if it establishes, persists, and spreads widely inside a natural ecosystem, stunting the growth of native plants and giving them room to overtake crops and native plants. Non-native plant species that have been brought into a new geographic area and have a negative effect on the ecosystems supporting horticulture and agriculture are known as invasive plant species. Invasive/noxious weeds, which are widely distributed in many types of ecosystems, significantly reduce crop production. Compared to native species, invading plant species have a higher potential to move their niche more rapidly and are more likely to adapt to new environments. The timing, speed, and longevity of seed germination have indeed been discovered to change as a result of climate change, which has consequences for plant invasions. More than native plant species, invasive plant species gain from atmospheric carbon dioxide (CO2) enrichment, greenhouse gas emissions, and global warming. A loss of native biodiversity due to invasive species includes species extinction, changes in hydrology, and altered ecosystem function.

Initial evaluations of the System of Rice Intensification in India and elsewhere focused mainly on its impacts on yield and income, and usually covered just one or two seasons. Researchers at the ICAR-Indian Institute of Rice Research have conducted a more comprehensive evaluation of SRI methods over six years (six wet and six dry seasons), comparing them with three alternatives: modified, partially mechanized SRI (MSRI) to reduce labor requirements; direct-seeded rice (DSR) as an alternative method for growing rice; and conventional transplanting of rice with flooding of fields (CTF). Grain yield with SRI methods was found to be about 50% higher than with CTF (6.35 t ha⁻¹ vs. 4.27 t ha⁻¹), while the MSRI yield was essentially the same (6.34 t ha⁻¹), 16% more than with DSR (5.45 t ha⁻¹). Water productivity with SRI methods was 5.32–6.85 kg ha-mm⁻¹, followed by 4.14–5.72 kg ha-mm⁻¹ for MSRI, 5.06–5.11 kg ha-mm⁻¹ for DSR, and 3.52–4.56 kg ha-mm⁻¹ for CTF. In comparison with CTF, SRI methods significantly enhanced soil microbial populations over time: bacteria by 12%, fungi by 8%, and actinomycetes by 20%. Biological activity in the rhizosphere was also higher as indicated by 8.5% greater dehydrogenase and 16% more FDA enzymes in soil under SRI management. Similarly, an indicator of soil organic matter, glucosidase activity, was 78% higher compared to CTF. SRI enhanced the relative abundance of beneficial microbial-feeding nematodes by 7.5% compared to CTF, while that of plant-pathogenic nematodes was 7.5% lower under SRI. Relative to conventional methods, SRI management reduced GHG emissions by 21%, while DSR reduced them by 23%, and MSRI by 13%, compared to standard rice-growing practice. Economic analysis showed both gross and net economic returns to be higher with SRI than with the other management systems evaluated. While the six-year study documented many advantages of SRI crop management, it also showed that MSRI is a promising adaptation that provides similar benefits but with lower labor requirements.

Initial evaluations of the System of Rice Intensification in India and elsewhere have mainly fo-cused on its impact on yield and income and have usually covered just one or two seasons. Re-searchers at the ICAR-Indian Institute of Rice Research conducted a more comprehensive evalua-tion of SRI methods over six years (six wet and six dry seasons), comparing these methods with three other rice crop management systems: modified, partially mechanized SRI (MSRI); direct-seeded rice (DSR); and normal transplanting with inundated fields (NTP). SRI grain yield was found to be about 50% higher than with NTP (6.35 t ha-1 vs 4.27 t ha-1), while the MSRI yield was essentially the same (6.34 t ha-1) and 16% higher than with DSR (5.45 t ha-1). Compared to NTP, SRI methods significantly enhanced soil microbial populations over time, bacteria by 12%, fungi by 8%, and actinomycetes by 20%. Indicators of biological activity in the rhizosphere were also higher, dehydrogenase by 8.5% and FDA enzymes by 16%. Glucosidase activity, an indicator of soil organic matter, was 78% higher. Relative to normal transplanting methods, SRI reduced GHG emissions by 21%, while DSR reduced them by 23% and MSRI by 13%, which indicated pos-itive effects of the alternate and improved methods over normal transplanting. Economic analy-sis showed that both gross and net economic returns to be higher with SRI than with MSRI and the other management systems evaluated. While the six-year study documented many ad-vantages of SRI crop management, the MSRI version evaluated is a promising adaptation that provide similar benefits but with lower labor requirements.

Abiotic stress is a major threat to the farming community, biasing the crop productivity in arid and semi-arid regions of the world. The seed is an important component of agriculture, contributing significantly to the booming production of food and feed crops across the different agro-ecological regions of the world with constant challenges with reference to production, storage, and quality control. Germination, plant growth, and development via non-normal physiological processes are detrimentally affected by stress. Seed priming is an alternative, low cost, and feasible technique, which can improve various abiotic stress tolerances through enhanced and advanced seed production. Seed priming is a process that involves imbibing seed with a restricted amount of water to allow sufficient hydration and advancement of metabolic processes but preventing germination. The beneficial influence of priming on the germination performance of diverse species is attributed to the induction of biochemical mechanisms of cell repair: the resumption of metabolic activity that can re-impose cellular integrity, through the synthesis of nucleic acids (DNA and RNA) and proteins and the improvement of the antioxidant defense system metabolic damage incurred by dry seed and thus fortifying the metabolic machinery of the seed. With this background, this chapter highlights the morphological, physiological, biochemical, and molecular responses of seed priming and recent advances in priming methods as a tool to combat abiotic stress in crop plants.

A field experiment was conducted at ICAR – Indian Institute of Rice Research Hyderabad during kharif and rabi seasons 2010 – 2011 and 2011 - 2012 to study the effect of sulphur on yield, nutrient status in grain and economics in rice – black gram cropping system. The experiment consisted of different levels of fertilizer (M1 - 120:60:40; and M2 - 60:30:20 kg N, P2O5 and K2O/ha) and sulphur schedules (S1 - control, S2 - sulphur application @ 30 kg/ha during kharif only, S3 - sulphur application during rabi only and S4 - sulphur application during both kharif and rabi) were evaluated with variety Jaya during kharif and blackgram variety LBG-648 during rabi season to study the applied, residual and cumulative effects of sulphur (S) in rice under selected rice based cropping systems in relation to improvement of productivity. Pooled results indicated that maximum rice yield (5.64 tonnes / ha) recorded in M2S3 (60:30:20 kg N P2O5 and K2O/ha + Sulphur application @ 30 kg/ha during rabi only) treatment where as corresponding minimum rice yield (3.71 tonnes / ha) was recorded with control (M1S1) where no application of sulphur was done. Similarly maximum black gram seed yield (1.98 tonnes / ha) was recorded in M2S3 where as corresponding minimum black gram yield (0.87 tonnes / ha) was recorded in control (M1S1) (120:60:40 kg N, P2O5 and K2O/ha + control). Highest nutrient composition of sulphur content, N content, protein content, P content and K content in paddy and black gram seed was recorded when sulphur was applied in rabi season (S3). Highest Zn content in Paddy seed (13.50 ppm) was obtained when sulphur was applied in kharif season (S2) and in black gram (77.67 %) when sulphur was applied in kharif and rabi season (S4).

A field study was conducted during summer season of 2012 and 2013 at Indian Institute of Horticultural Research in Bangalore, India to evaluate if priming could improve grain yield and water use efficiency of cowpea under limited water supply condition through drip system. Seed variety Arka Garima received the following priming treatments: they were soaked in GA3,CaCl2, ammonium molybdate, KBr, MgNO3, ZnSO4 solutions and water (hydropriming) for 24 hours at 15o C. Crop was subjected to three irrigation intervals in which the irrigation was applied at 0.9, 0.7, 0.5 Epan Replenishment of evaporation. Plant height, number of trifoliate leaves, total dry matter accumulation, number of pods per plant, number of seeds per pod, 1000 seed weight and grain and biological yield were increased by different priming treatments compared to control. Seed priming increased the LAI, RGR, CGR and NAR at all irrigation regimes. Results suggest that the use of seed priming with either GA3 (100ppm) or ammonium molybdate (10-3 M) for 24 hours at low concentration can be helpful in cowpea under both optimum as well as limited water conditions.

A split plot design field study was conducted during summer month of 2012 and 2013 at the vegetable block of Indian Institute of Horticultural Research in Bangalore, India to evaluate if priming could improve grain yield and water use efficiency of cowpea under limited water supply condition through drip system. Seeds of cultivar Arka garima received the following priming treatments: they were soaked in GA3,Calcium Chloride, Ammonium Molybdate, Potassium Bromide, Magnesium Nitrate, Zinc Sulphate solutions, and aerated distil water (hydropriming) for 24 hours at 15o C. Crops were subjected to three irrigation intervals in which the irrigation was applied at 0.9, 0.7, 0.5 Epan Replenishment of evaporation. Seed priming treatments reduced the mean emergence time, promoted germination, early canopy development and flower initiation in comparison to the untreated control. Plant height, number of branches, total dry matter accumulation, number of pods per plant, number of seeds per pod, 1000 seed weight and grain and biological yield, harvest index and irrigation water use efficiency increased by different priming treatments. Seed priming increased the irrigation water use efficiency (IWUE) of all irrigation regimes. Grain yields linearly increased at 0.9 Epan Replenishment while maximum IWUE was achieved at 0.5 Epan Replenishment. Results suggest that the use of seed priming with either GA3 (100ppm) or Ammonium Molybdate (10-3 M) for 24 hours at low concentration can be helpful in cowpea under both optimum as well as limited water conditions.