Corrigendum: Sensor-based precision nutrient and irrigation management enhances the physiological performance, water productivity, and yield of soybean under system of crop intensification.

[This corrects the article DOI: 10.3389/fpls.2023.1282217.].

System of wheat intensification (SWI): Effects on lodging resistance, photosynthetic efficiency, soil biomes, and water productivity.

Intense cultivation with narrow row spacing in wheat, a common practice in the Indo-Gangetic plains of South Asia, renders the crop more susceptible to lodging during physiological maturity. This susceptibility, compounded by the use of traditional crop cultivars, has led to a substantial decline in overall crop productivity. In response to these challenges, a two-year field study on the system of wheat intensification (SWI) was conducted. The study involved three different cultivation methods in horizontal plots and four wheat genotypes in vertical plots, organized in a strip plot design. Our results exhibited that adoption of SWI at 20 cm × 20 cm resulted in significantly higher intercellular CO2 concentration (5.9-6.3%), transpiration rate (13.2-15.8%), stomatal conductance (55-59%), net photosynthetic rate (126-160%), and photosynthetically active radiation (PAR) interception (1.6-25.2%) over the existing conventional method (plant geometry 22.5 cm × continuous plant to plant spacing) of wheat cultivation. The lodging resistance capacity of both the lower and upper 3rd nodes was significantly higher in the SWI compared to other cultivation methods. Among different genotypes, HD 2967 demonstrated the highest recorded value for lodging resistance capacity, followed by HD 2851, HD 3086, and HD 2894. In addition, adoption of the SWI at 20 cm × 20 cm enhanced crop grain yield by 36.9-41.6%, and biological yield by 27.5-29.8%. Significantly higher soil dehydrogenase activity (12.06 µg TPF g-1 soil hr-1), arylsulfatase activity (82.8 µg p-nitro phenol g-1 soil hr-1), alkaline phosphatase activity (3.11 n moles ethylene g-1 soil hr-1), total polysaccharides, soil microbial biomass carbon, and soil chlorophyll content were also noted under SWI over conventional method of the production. Further, increased root volumes, surface root density and higher NPK uptake were recorded under SWI at 20×20 cm in comparison to rest of the treatments. Among the tested wheat genotypes, HD-2967 and HD-3086 had demonstrated notable increases in grain and biological yields, as well as improvements in the photosynthetically active radiation (PAR) and chlorophyll content. Therefore, adoption of SWI at 20 cm ×20 cm (square planting) with cultivars HD 2967 might be the best strategy for enhancing crop productivity and resource-use efficiency under the similar wheat growing conditions of India and similar agro-ecotypes of the globe.

Grain nitrogen content and productivity of rice and maize under variable doses of fertilizer nitrogen.

The rice-maize system is a dominant cropping system of south Asia and consumes a considerable amount of fertilizer. The indiscriminate use of fertilizer particularly nitrogen (N) is degrading the soil health and polluting the environment. Lower N-use efficiency is a major problem and needs to be improved for higher yield, lower cost of cultivation and better environment. The grain quality is also altered by the N-application as N is a major constituent of protein. Studies on the effect of N-application on grain N-content is still lacking. We hypothesised that optimization of N application would result in economising N dose, improving yield and NUE and improving grain quality. Under that context, a field experiment was conducted with different doses of fertilizer N for rice and maize. Fertilizer N was applied at the rate of 0, 40, 80, 120, 160, 200 and 240 kg ha-1 (N0-N240). An increase in grain yield was observed up to 80 and 160 kg ha-1 for rice and maize, respectively. The N content of grain increased with N rates and a significant increase was noted in N200 (1.42%) being at par with N240 (1.49%) but significantly higher than others by 13-32%. With an increase of each kilogram of N, the grain N content increased by 14 and 20 µg (microgram) for rice and maize, respectively. The leaf N content registered a decreasing trend with the progress of the crop growth for both rice and maize. The agronomic efficiency (AE) of N initially increased with an increase in the rate of fertilizer N followed by a decrease with higher doses of N. Unlike the AE, the partial factor productivity (PFP) of N decreased gradually with an increase in the rate of fertilizer N. The chlorophyll content of flag leaves also registered an increasing trend with an increasing rate of fertilizer N. On the surface soil (0-15 cm), the treatments which received lower (N0, N40) and higher (N240) fertilizer N recorded a comparatively higher total soil N than other treatments. The mean NUE was 0.42 and 0.75 for rice and maize, respectively. The study suggests an economic fertilizer N rate of 165 and 167 kg N ha-1, for rice and maize, respectively. It also concludes that the grain N content can be altered by N-application rates though more research is needed.

Above and below-ground growth, accumulated dry matter and nitrogen remobilization of wheat (Triticum aestivum) genotypes grown in PVC tubes under well- and deficit-watered conditions.

The continuing decline in water resources under the ever-changing climate compels us to re-orient our focus to a more sustainable practice. This study investigates the performance of Triticum aestivum wheat genotypes viz. HD-2967, HD-3086, HD-3249, DBW-187, and HD-3226 under well- and deficit-watered conditions for their root-traits, biomass and nitrogen accumulation and remobilization, and water use efficiencies, grown in PVC-tubes. The genotypes HD-2967, HD-3086, HD-3249, DBW-187, and HD-3226 under well-watered (WW) resulted in 36, 35, 38, 33, and 42% more grain yield compared to deficit-watered (DW). Among the genotypes, HD-3249 had the highest grain yield under both well- and deficit-watered conditions. Compared to DW, the WW had 28%, 30%, and 28% greater root length, biomass, and root length density at flowering {102 days (d), Z61}, while among the genotypes, HD-3249 had relatively greater root-traits. At flowering (Z61) and maturity (132 d, Z89), genotypes under WW accumulated 30-46% and 30-53%, respectively greater shoot biomass over the DW. Furthermore, the shoot biomass remobilised for HD-2967, HD-3086, HD-3249, DBW-187, and HD-3226 under the WW was 32, 37, 39, 35, and 35% greater than the DW. The nitrogen partitioning to different plant parts at flowering (Z61) and maturity (Z89) was significantly greater with the WW than with DW. The total nitrogen- remobilized and contribution to grain-N under the WW was 55, 58, 52, 53, 58% and 9, 19, 15, 17, 17% greater than the DW for the genotypes HD-2967, HD-3086, HD-3249, DBW-187, and HD-3226. The irrigation water use efficiency (WUE) at flowering (Z61) was more under the deficit-watered, but the biomass and grain total WUE was improved with the well-watered condition. Hence, it is apparent that proper scheduling of irrigation and N applications, along with the adoption of a genotype suited to a particular environment, will result in better WUE and grain yields, along with better utilization of scarce resources.

Timely sown maize hybrids improve the post-anthesis dry matter accumulation, nutrient acquisition and crop productivity.

Delayed sowing of maize hybrids could exacerbate the capability of maximizing the yield potential through poor crop stand, root proliferation, nutrient uptake, and dry matter accumulation coupled with the inadequate partitioning of the assimilates. This study appraised the performance of five recent maize hybrids viz., PMH-1, PJHM-1, AH-4158, AH-4271, and AH-8181 under timely and late sown conditions of the irrigated semi-arid ecologies. Timely sowing had the grain and stover yields advantage of 16-19% and 12-25%, respectively over the late sown maize hybrids. The advanced hybrids AH-4271 and AH-4158 had higher grain yields than the others. During the post-anthesis period, a greater dry matter accumulation and contribution to the grain yield to the tune of 16% and 10.2%, respectively, was observed under timely sown conditions. Furthermore, the nutrient acquisition and use efficiencies also improved under the timely sown. The nutrient and dry matter remobilization varied among the hybrids with AH-4271 and PMH-1 registering greater values. The grain yield stability index (0.85) was highest with AH-4158 apart from the least yield reduction (15.2%) and stress susceptibility index (0.81), while the maximum geometric mean productivity was recorded with the AH-4271 (5.46 Mg ha-1). The hybrids AH-4271 and PJHM-1 exhibited improved root morphological traits, such as root length, biomass, root length density, root volume at the V5 stage (20 days after sowing, DAS) and 50% flowering (53 DAS). It is thus evident that the timely sowing and appropriate hybrids based on stress tolerance indices resulted in greater yields and better utilization of resources.

Sensor-based precision nutrient and irrigation management enhances the physiological performance, water productivity, and yield of soybean under system of crop intensification.

Sensor-based decision tools provide a quick assessment of nutritional and physiological health status of crop, thereby enhancing the crop productivity. Therefore, a 2-year field study was undertaken with precision nutrient and irrigation management under system of crop intensification (SCI) to understand the applicability of sensor-based decision tools in improving the physiological performance, water productivity, and seed yield of soybean crop. The experiment consisted of three irrigation regimes [I1: standard flood irrigation at 50% depletion of available soil moisture (DASM) (FI), I2: sprinkler irrigation at 80% ETC (crop evapo-transpiration) (Spr 80% ETC), and I3: sprinkler irrigation at 60% ETC (Spr 60% ETC)] assigned in main plots, with five precision nutrient management (PNM) practices{PNM1-[SCI protocol], PNM2-[RDF, recommended dose of fertilizer: basal dose incorporated (50% N, full dose of P and K)], PNM3-[RDF: basal dose point placement (BDP) (50% N, full dose of P and K)], PNM4-[75% RDF: BDP (50% N, full dose of P and K)] and PNM5-[50% RDF: BDP (50% N, full P and K)]} assigned in sub-plots using a split-plot design with three replications. The remaining 50% N was top-dressed through SPAD assistance for all the PNM practices. Results showed that the adoption of Spr 80% ETC resulted in an increment of 25.6%, 17.6%, 35.4%, and 17.5% in net-photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci), respectively, over FI. Among PNM plots, adoption of PNM3 resulted in a significant (p=0.05) improvement in photosynthetic characters like Pn (15.69 µ mol CO2 m-2 s-1), Tr (7.03 m mol H2O m-2 s-1), Gs (0.175 µmol CO2 mol-1 year-1), and Ci (271.7 mol H2O m2 s-1). Enhancement in SPAD (27% and 30%) and normalized difference vegetation index (NDVI) (42% and 52%) values were observed with nitrogen (N) top dressing through SPAD-guided nutrient management, helped enhance crop growth indices, coupled with better dry matter partitioning and interception of sunlight. Canopy temperature depression (CTD) in soybean reduced by 3.09-4.66°C due to adoption of sprinkler irrigation. Likewise, Spr 60% ETc recorded highest irrigation water productivity (1.08 kg ha-1 m-3). However, economic water productivity (27.5 INR ha-1 m-3) and water-use efficiency (7.6 kg ha-1 mm-1 day-1) of soybean got enhanced under Spr 80% ETc over conventional cultivation. Multiple correlation and PCA showed a positive correlation between physiological, growth, and yield parameters of soybean. Concurrently, the adoption of Spr 80% ETC with PNM3 recorded significantly higher grain yield (2.63 t ha-1) and biological yield (8.37 t ha-1) over other combinations. Thus, the performance of SCI protocols under sprinkler irrigation was found to be superior over conventional practices. Hence, integrating SCI with sensor-based precision nutrient and irrigation management could be a viable option for enhancing the crop productivity and enhance the resource-use efficiency in soybean under similar agro-ecological regions.

Integrated management enhances crop physiology and final yield in maize intercropped with blackgram in semiarid South Asia.

Photosynthesis, crop health and dry matter partitioning are among the most important factors influencing crop productivity and quality. Identifying variation in these parameters may help discover the plausible causes for crop productivity differences under various management practices and cropping systems. Thus, a 2-year (2019-2020) study was undertaken to investigate how far the integrated crop management (ICM) modules and cropping systems affect maize physiology, photosynthetic characteristics, crop vigour and productivity in a holistic manner. The treatments included nine main-plot ICM treatments [ICM1 to ICM4 - conventional tillage (CT)-based; ICM5 to ICM8 - conservation agriculture (CA)-based; ICM9 - organic agriculture (OA)-based] and two cropping systems, viz., maize-wheat and maize + blackgram-wheat in subplots. The CA-based ICM module, ICM7 resulted in significant (p < 0.05) improvements in the physiological parameters, viz., photosynthetic rate (42.56 µ mol CO2 m-2 sec-1), transpiration rate (9.88 m mol H2O m-2 sec-1) and net assimilation rate (NAR) (2.81 mg cm-2 day-1), crop vigour [NDVI (0.78), chlorophyll content (53.0)], dry matter partitioning toward grain and finally increased maize crop productivity (6.66 t ha-1) by 13.4-14.2 and 27.3-28.0% over CT- and OA-based modules. For maize equivalent grain yield (MEGY), the ICM modules followed the trend as ICM7 > ICM8 > ICM5 > ICM6 > ICM3 > ICM4 > ICM1 > ICM2 > ICM9. Multivariate and PCA analyses also revealed a positive correlation between physiological parameters, barring NAR and both grain and stover yields. Our study proposes an explanation for improved productivity of blackgram-intercropped maize under CA-based ICM management through significant improvements in physiological and photosynthetic characteristics and crop vigour. Overall, the CA-based ICM module ICM7 coupled with the maize + blackgram intercropping system could be suggested for wider adoption to enhance the maize production in semiarid regions of India and similar agroecologies across the globe.

Double zero-tillage and foliar-P nutrition coupled with bio-inoculants enhance physiological photosynthetic characteristics and resilience to nutritional and environmental stresses in maize-wheat rotation.

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 CO2 m-2 s-1), stomatal conductance (SC) (0.44; 0.26 mol H2O m-2 s-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 P100 besides 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.

Microbes-mediated integrated nutrient management for improved rhizo-modulation, pigeonpea productivity, and soil bio-fertility in a semi-arid agro-ecology.

Excessive dependence on chemical fertilizers and ignorance to organic and microbial inputs under intensive cropping systems are the basic components of contemporary agriculture, which evolves several sustainability issues, such as degraded soil health and sub-optimal crop productivity. This scenario urges for integrated nutrient management approaches, such as microbes-mediated integrated plant nutrition for curtailing the high doses as chemical fertilizers. Rationally, experiment has been conducted in pigeonpea at ICAR-IARI, New Delhi, with the aim of identifying the appropriate nutrient management technique involving microbial and organic nutrient sources for improved rhizo-modulation, crop productivity, and soil bio-fertility. The randomized block-designed experiment consisted nine treatments viz. Control, Recommended dose of fertilizers (RDF), RDF+ Microbial inoculants (MI), Vermicompost (VC), Farm Yard Manure (FYM), Leaf Compost (LC), VC + MI, FYM + MI, and LC + MI. Rhizobium spp., Pseudomonas spp., Bacillus spp., and Frateuria aurantia were used as seed-inoculating microbes. The results indicated the significant response of integration following the trend VC + MI > FYM + MI > LC + MI > RDF + MI for various plant shoot-root growth attributes and soil microbial and enzymatic properties. FYM + MI significantly improved the water-stable aggregates (22%), mean weight diameter (1.13 mm), and geometric mean diameter (0.93 mm), soil organic carbon (SOC), SOC stock, and SOC sequestration. The chemical properties viz. available N, P, and K were significantly improved with VC + MI. The study summarizes that FYM + MI could result in better soil physico-chemical and biological properties and shoot-root development; however; VC + MI could improve available nutrients in the soil and may enhance the growth of pigeonpea more effectively. The outcomes of the study are postulated as a viable and alternative solution for excessive chemical fertilizer-based nutrient management and would also promote the microbial consortia and organic manures-based agro-industries. This would add to the goal of sustainable agricultural development by producing quality crop produce, maintaining agro-biodiversity and making the soils fertile and healthy that would be a "gift to the society."

Biopolymeric superabsorbent hydrogels enhance crop and water productivity of soybean-wheat system in Indo-Gangetic plains of India.

Environmental crises, declining factor productivity, and shrinking natural resource is a threat to global agricultural sustainability. The task is much more daunting in the Indo-Gangetic northern plains of India, where depletion of the underground water table and erratic rains due to the changing climate pose a major challenge to agriculture. To address these challenges a field investigation was carried out during 2016-2018 to test the efficacy of biopolymeric superabsorbent hydrogels namely Pusa Hydrogel (P-hydrogel: a semi-synthetic cellulose derivative-based product) and kaolin derivative of Pusa Hydrogel (K-hydrogel: semi-synthetic cellulose derivative) to assess their effect on crop and water productivity, soil moisture, root dynamics, and economics of soybean (Glycine max L.)-wheat (Triticum aestivum L.) system under three irrigation regimes namely full irrigation, limited irrigation and rainfed. The results revealed that the full irrigation along with P-hydrogel led to enhanced grain yield, biomass yield, and water productivity (WP) of soybean (1.61-10.5%, 2.2-9.5%, and 2.15-21.8%, respectively) and wheat (11.1-18.3%, 12-54% and 11.1-13.1%, respectively) over control plots. Likewise, under water stressed plots of rainfed conditions with P-hydrogel exhibited 52.7 and 20.6% higher system yields (in terms of wheat equivalent yield) over control and other combinations during the respective study years. Whereas the magnitude of increase in system yield under limited irrigation with P-hydrogel was ~ 15.1% and under full irrigation with P-hydrogel was 8.0-19.4%. Plots treated with P-hydrogel retained 3.0-5.0% higher soil moisture compared to no-hydrogel plots, while K-hydrogel treated plots held the lower moisture (4.0-6.0%) than the control. In terms of profitability, full irrigation along with P-hydrogel plots registered 12.97% higher economic returns over control. The results suggested that P-hydrogel (2.5 kg ha-1) reduces runoff water loss in full irrigation applied plots and retained more water, where loss of water is more thus reduces number of irrigations. Hence P-hydrogel with irrigation water is a viable option for sustainable production of soybean-wheat systems in the Indo-Gangetic plains of India and other similar eco-regions of the world.

Appraisal of probabilistic levels of toxic metals and health risk in cultivated and marketed vegetables in urban and peri-urban areas of Delhi, India.

A total of six vegetables (S. tuberosum, D. carota, S. lycopersicum, A. esculentus, S. oleracea and B. juncea) were analysed for five heavy metals (As, Cd, Cr, Hg, and Pb) to evaluate the contamination load in vegetables collected from five cultivated and two market sites (n = 504) at Delhi, India. The irrigation water samples and soil samples (n = 180) were only collected from cultivated sites. The results showed that the concentration of heavy metals in soil and water samples were well below the permissible level except for Cd 0.001-0.013 µg g-1. Similarly, the concentration of Cd (>0.20 µg g-1) was detected higher in all investigated vegetables except for tomato. The evaluation index value was highest for spinach and lowest for tomato. The transfer factor values and metal pollution index was maximum in spinach and okra. Principal component analysis (PCA), Tukey's HSD (Honestly Significant Difference) test, and one-way and two-way ANOVA (Analysis of Variance) were also applied to statistically analyse the results.

Double zero tillage and foliar phosphorus fertilization coupled with microbial inoculants enhance maize productivity and quality in a maize-wheat rotation.

Maize is an important industrial crop where yield and quality enhancement both assume greater importance. Clean production technologies like conservation agriculture and integrated nutrient management hold the key to enhance productivity and quality besides improving soil health and environment. Hence, maize productivity and quality were assessed under a maize-wheat cropping system (MWCS) using four crop-establishment and tillage management 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. Double zero-tilled PRBZT-PRBZT system significantly enhanced the maize grain, starch, protein and oil yield by 13.1-19% over conventional FBCT-FBCT. P50 + PSB + AMF + 2FSP, integrating soil applied-P, microbial-inoculants and foliar-P, had significantly higher grain, starch, protein and oil yield by 12.5-17.2% over P100 besides saving 34.7% fertilizer-P both in maize and on cropping-system basis. P50 + PSB + AMF + 2FSP again had significantly higher starch, lysine and tryptophan content by 4.6-10.4% over P100 due to sustained and synchronized P-bioavailability. Higher amylose content (24.1%) was observed in grains under P50 + PSB + AMF + 2FSP, a beneficial trait due to its lower glycemic-index highly required for diabetic patients, where current COVID-19 pandemic further necessitated the use of such dietary ingredients. Double zero-tilled PRBZT-PRBZT reported greater MUFA (oleic acid, 37.1%), MUFA: PUFA ratio and P/S index with 6.9% higher P/S index in corn-oil (an oil quality parameter highly required for heart-health) over RBCT-RBCT. MUFA, MUFA: PUFA ratio and P/S index were also higher under P50 + PSB + AMF + 2FSP; avowing the obvious role of foliar-P and microbial-inoculants in influencing maize fatty acid composition. Overall, double zero-tilled PRBZT-PRBZT with crop residue retention at 6 t/ha per year along with P50 + PSB + AMF + 2FSP while saving 34.7% fertilizer-P in MWCS, may prove beneficial in enhancing maize productivity and quality so as to reinforce the food and nutritional security besides boosting food, corn-oil and starch industry in south-Asia and collateral arid agro-ecologies across the globe.