SPAD Index Research Articles

Effects of Drought and Salinity on Growth, Yield and Nutritional Contents of Cowpea Bean (Vigna marina)

Background: The study was carried out to determine the duration of drought and salinity level on growth, green matter yield and nutrient content in cowpea bean plants. Methods: The experiment was arranged in a 2-factor factorial style, including (A) three drought levels: (i) 07 days of watering, (ii) 14 days of irrigation and (iii) 21 days of watering cessation; factor (B) three salinity levels including (i) saline irrigation 2%, (ii) saline irrigation 4% and (iii) saline irrigation 6%. Each treatment has five replicates. Result: Experimental results showed that stopping irrigation of cowpea bean plants for 14 and 21 days reduced height, SPAD index, stomatal opening, DM., CP and ash content, compared to stopping watering for seven days. It reduced the yield of green matter and the nitrogen content in the plant. Besides, increasing salinity irrigation concentration at four and 6% declined the height, SPAD index, stomatal opening, D.M., E.E. and C.P. of cowpea bean.The green matter yield and nitrogen content in the plants also decreased when irrigated with salinity 6%.

Aquaponics Production of Wheatgrass (Triticum aestivum L.) in Different Horticultural Substrates with African Catfish (Clarias gariepinus) in Northern Germany

In the present study, wheatgrass (Triticum aestivum L.) was chosen since fish effluents could be adequate to support its optimal growth. Wheatgrass was irrigated by water from African catfish (Clarias gariepinus) production under two stocking densities, namely extensive aquaculture unit (EAU) and intensive aquaculture unit (IAU), and tap water mixed with fertilizer (Control) in combination with three horticultural substrates: 100% coconut fibers (C), 70% coconut fibers + 30% perlite (CP), and 50% perlite + 50% vermiculite (PV) in an ebb-and-flow system. Different plant growth parameters, including nutrient contents, were evaluated and discussed. The results showed that regarding irrigation water, shoot dry mass was significantly higher in fish water groups. The root–shoot ratio was significantly higher in Control. The highest SPAD index was discovered in IAU. Regarding substrates, the root–shoot ratio was significantly low in C. Vitamin and mineral production reached mainly the highest concentrations in the combination of fish water with different substrates. In conclusion, irrigation water from IAU and coconut fibers were sufficient for optimal wheatgrass growth; meanwhile, IAU effluents showed a positive influence on vitamin production. Our study demonstrates the potential of aquaponics as a more sustainable way of producing superfoods.

Production and morphophysiological responses of Panicum maximum cv. BRS Zuri to water availability

Due to the increasing intensification of livestock farming and agricultural systems, there is demand for highly productive forage species. Panicum maximum cv. BRS Zuri is forage that has good productivity, vigor and promotes good animal performance. The objective of this study was to evaluate the morphophysiological and production characteristics of Panicum maximum cv. BRS Zuri subjected to water availability in Fluvic Neosol (Entisol). A potted-plant experiment was conducted in a greenhouse at the Federal University of Rondonópolis, Brazil. The experimental design was completely randomized, with five levels of water availability, corresponding to 25, 50, 75, 100 and 125 % of the maximum soil water holding capacity, and six replicates, in three successive cuts. The variables analyzed were: soil pH, SPAD index, plant height, leaf area, shoot dry mass, root dry mass, root volume, water consumption and water use efficiency. Water availability influenced the development of Panicum maximum cv. BRS Zuri, with the highest results between 67 % and 111 % of the maximum soil water holding capacity. The results show that the production and morphological responses were negatively influenced by water availability levels of 25 % and 125 %. These results makes it possible to affirm that, under the studied conditions, the cultivar BRS Zuri showed moderate adaptation to 125% water availability (excess water).

Plant biostimulants from seaweeds or vegetal proteins enhance the salinity tolerance in greenhouse lettuce by modulating plant metabolism in a distinctive manner

The use of plant biostimulants such as seaweed extracts (SWE) and protein hydrolysates (PH) has grown in the recent years due to their beneficial effects on yield under both optimal and sub-optimal conditions such as salt stress. The comprehension of the mode of action of these two important categories of biostimulants on plant performance will allow to use them more efficiently under different growth conditions. This study aimed to examine the efficacy of a seaweed and plant-based biostimulants on greenhouse lettuce (Lactuca sativa L.) grown under non-saline (0 mM NaCl) and saline conditions (40 mM NaCl) in terms of growth, yield, SPAD index, leaf mineral composition and metabolomic profiling. Shoot fresh weight of lettuce was reduced by 15.3% under 40 mM of NaCl. Nonetheless, it was boosted by both used biostimulants by 9 and 18%, on average, under 0 and 40 mM NaCl salinity, respectively. Na content under saline conditions was reduced in the presence of the biostimulants treatment, where PH reduced it significantly by 15.6% and SWE by 9.4%. On the other hand, Cl content was significantly reduced only under PH treatment. Both biostimulants elicited a broad metabolic reprogramming, involving the accumulation of stress-related compounds such as glucosinolates, terpenoid phytoalexins, and jasmonates. Interestingly, distinctive metabolomic signatures could be observed following the application of the different biostimulants under salinity conditions. In more detail, PH promoted the accumulation of glucosinolates and phytoalexins precursors, while SWE induced a down accumulation of secondary metabolites. Our findings indicate different processes being modulated by PH and SWE, with possible synergistic effects, thus paving the way towards integrated strategies to alleviate the detrimental effects of salinity in lettuce.

Cadmium accumulation and toxicity in watercress (Barbarea verna), chicory (Cichorium endivia) and rocket (Eruca sativa) plants

Some vegetables have the ability to accumulate cadmium (Cd)at levels that are toxic to most other plants. The objective of thisstudy was to evaluate the Cd accumulation and its toxic effects on edible vegetables. Three species were tested: watercress (Barbarea verna); chicory (Cichorium endivia); rocket (Eruca sativa) and four Cd doses (0; 1.5; 3.0; 6.0 mg kg-1), with three replications. We evaluated Cd concentration, fresh and dry mass and SPAD index. We calculated tolerance index (TI), translocation index (TR) and the transfer coefficient (TC). Rocket, chicory and watercress are susceptible to Cd contamination and chicory presented visual symptoms of toxicity (chlorosis and mass loss). The Cd contents above those allowed were 0.6; 0.56 and 1.03 mg kg-1 in rocket, watercress and chicory, respectively, these values were reached by applying doses from 1.5 mg kg-1 for rocket and 3 mg kg-1 for watercress and chicory.

Streptomyces rimosus rhizobacteria and Glomus mosseae mycorrhizal fungus inoculation alleviate salinity stress in grapevine through morphophysiological changes and nutritional balance

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) have positive impacts on growth and production of plants under saline condition. However, their interactive effects on plant behavior under salt stress remained unclear. To address this, a glasshouse experiment was conducted to elucidate the effect of the single and combined (co-inoculation) application of Glomus mosseae (Gm) AMF and Streptomyces rimosus (Sr) PGPR on salt tolerance of Sultana grapevine (Vitis vinifera L.). Based on results, the combined inoculation with Gm AMF and Sr PGPR markedly improved shoot and root morphometric traits and also soluble carbohydrate, soluble proteins, proline content compared to those vines inoculated with these symbionts alone or uninoculated vines under saline condition. The highest main root length was related to inoculated vines with Sr PGPR, which was 18.5% higher than uninoculated control plants under saline condition. Under saline condition, co-inoculation with Gm AMF and Sr PGPR decreased leaf necrotic, leaf ion leakage and malondialdehyde content by 31%, 43% and 38% but increased SPAD index, relative water content, catalase and guaiacol peroxidase activity by 45%, 26%, 30% and 53% compared with control uninoculated plant. Among salt stressed plants, the single inoculated vines with Gm AMF showed the highest total phenol and flavonoid content compared to control plants. In vines grown under saline condition, the highest content of leaf P, Mg, Fe, Zn and Mn were related to Gm plus Sr -inoculated vines. Leaf NO−3 and K of all inoculated vines did not showed statistically significant difference with each other's. Under saline condition, root NO3, K, Mg, Fe, Zn and Mn did not showed significant difference among inoculated plants but differed significantly with control vines. Therefore, combined application of Gm AMF and Sr PGPR assisted host plants to uptake higher nutrients during salt stress; confer salt tolerance to vines by increase in osmoregulants, phenolic compounds and antioxidant enzymes activities in their tissues.

Biostimulant derived from the fermentation of Inulav viscosa (Inort) in the germination and growth of Amaranthus hypochondriacus

Research objective: This research aims to evaluate Inula's bio-stimulating potential in the form of macerate in water in the cultivation of Amaranthus hypochondriacus. This is to increase knowledge of this plant that commonly exhibits inhibitory characteristics towards the germination of various plants. Materials and Methods: The experiments started in May 2022 and were conducted in the greenhouses of CREA-OF in Pescia on Amaranthus hypochondriacus plants. On September 24, 2022, plant height, leaves number, leaves the surface area, vegetative weight, roots volume and length, the number of germinated seeds, average germination time, the number of microorganisms in the substrate, plant dead number and pH were determined. In addition, the SPAD index was measured on three leaves pinched from the bottom to the apex of the canopy of each plant (for a total of 90 measurements per treatment) and tissue mineral content was evaluated on collected dry matter (N, P, K, Ca, Mg, Fe and Na, Cl). Results and Discussion: The experiment showed that using Inula as a bio stimulant can significantly improve germination and growth and reduce mortality in Amaranthus hypochondriacus plants. In general, a significant increase in plant height and number of leaves, vegetative and root biomass was observed in plants treated with INORT, with differences depending on the percentage of product supplied to the plants. There was also a significant reduction in the mortality of plants treated with the biofertilizer product and increased microbial biomass. The trial also showed that the Inula biofertilizer could improve the chlorophyll content of the plant and increase the N, P, K, Ca, Fe, and Na content, while no differences were found for the parameters Mg and Cl. This test also shows biostimulant effects regarding seed germination and the average germination time reduction. This is interesting because Inula is usually mentioned for its inhibiting activity in seed germination, which probably depends on the transformation process. However, when macerated with microbial products, the inhibiting activity is nullified, and the fast-growing microorganisms utilize the organic products provided by this plant. Conclusions: In this experiment, further exciting and innovative aspects were highlighted in the use of this plant, given its already recognized importance from a medicinal, melliferous and biodiversity point of view. More experiments are underway to improve the protocol for using a biofertilizer based on Inula and microorganisms for horticulture for plant stimulation and defence.

Effect of Biostimulant Application on Plant Growth, Chlorophylls and Hydrophilic Antioxidant Activity of Spinach (Spinacia oleracea L.) Grown under Saline Stress

Irrigated agricultural lands are prone to salinity problems which may imperil horticultural crops by reducing growth, yield and even qualitative traits. Eco-friendly approaches such as biostimulant application and in particular protein hydrolysates from vegetal origin are implemented to mitigate salinity stress effects on crops. For this reason, a greenhouse experiment on spinach irrigated with increasing concentrations of saline water (EC = 3 dS m−1 (EC3), 6 dS m−1 (EC6) and 9 dS m−1 (EC9), in addition to non-saline treatment (EC0)) was organized, while plants were subjected to foliar applications of a protein hydrolysate from vegetal origin on a weekly basis. The application of this biostimulant helped mitigate the adverse effects of saline stress, by increasing the SPAD index and total chlorophylls of spinach plants. Yield was significantly boosted under biostimulant treatment in saline conditions and reached the value obtained in control treatment (no biostimulants added) × EC0 in the case of EC 3 and 6 dS m−1. In addition, the number of leaves and plants m−1 was increased under biostimulant treatment, and most importantly the hydrophilic antioxidant activity of spinach, thus a qualitative aspect of great importance was also increased. Such results increase the knowledge on the effects of protein hydrolysates application on an important leafy vegetable and may help growers mitigate saline conditions and maintain high crop yield and high quality of the final product when no other source of irrigation water is available.

ADUBAÇÃO COM BORO E ZINCO NO CULTIVO DE MILHO EM NEOSSOLO LITÓLICO DISTRÓFICO

ABSTRACT The objective of this work was to evaluate the effect of soil application of different boron (B) rates to the soil, with and without application of zinc (Zn), on growth, production components, and grain yield of maize crops grown in a Lithic Quartzipsamment with low B and Zn contents. A randomized block experimental design was used, in a 6×2 factorial arrangement corresponding to six B rates (0, 1, 2, 3, 4, and 5 kg ha-1), with and without application of Zn (2.0 kg ha-1), applied to the soil at sowing, with four replications. Growth variables (stem diameter and plant height), and chlorophyll SPAD index were evaluated at the R1 phenological stage. Maize ear length, one-thousand grain weight, and grain yield, and the B maximum efficiency rate were evaluated at the R6 phenological stage. Application of B and Zn to the soil increases maize grain yield in soils with sandy clay loam texture and low B and Zn contents; the plant absorption and metabolism indicated synergism between these elements when using soil applications of 1.0 kg ha-1 of B combined with 2.0 kg ha-1 of Zn to the planting furrows. The rates with maximum technical efficiency for grain yield were 3.29 and 4.31 kg of B ha-1 in treatments without and with application of Zn, respectively.

Selection of biofortified mini lettuce progenies resistant to Pectobacterium carotovorum subsp. carotovorum

Brazilian consumers are increasingly seeking unique vegetable products, such as mini lettuces. However, their production is hampered by a wide variety of pathogens, including Pectobacterium carotovorum subsp. carotovorum, which causes soft rot in lettuce. In this study, we aimed to select biofortified mini lettuce genotypes with good agronomic traits and resistance to P. carotovorum. A randomized block design consisting of 12 treatments, conducted in a field and greenhouse (Federal University of Uberlândia [UFU]), was used to select biofortified mini lettuce with good agronomic traits: SPAD index, stem and plant diameter, stem length, plant height, number of leaves, fresh weight, and bolt resistance. A completely randomized design consisting of 13 treatments was used for resistance or susceptibility testing. The bacterial suspension was inoculated and the following were assessed: disease severity, 16 days after inoculation; area under the disease progress curve, calculated separately at 4, 8, 12, and 16 days after inoculation as well as the sum of data calculated on all the assessment days; and the disease resistance class. The genotypes UFU 215#1 and UFU 215#2 had significantly high carotenoid concentrations. The genotypes UFU 66#4, UFU 215#1, and UFU 215#7 showed high bolt resistance. All genotypes were classified as resistant or moderately resistant to the P. carotovorum isolate, UFU A7.

Ecophysiology and water use efficiency of soybean cultivars under field conditions

A wide range of soybean cultivars is available on the market and understanding the physiological response and yield of these materials is fundamental to develop new management systems. Thus, the objective of the present study was to assess ecophysiological parameters and yield of soybean cultivars under field conditions. The experiment was carried out on a farm located in the municipality of Açailândia, Maranhão, Brazil. Three commercial cultivars were used (SC1, SC2 and SC3), and gas exchanges, SPAD index, Fv/Fm, photosynthesis index (PI), instantaneous water use efficiency (WUE) and intrinsic instantaneous of the use of water (iWUE) were assessed during the vegetative (V5) and reproductive (R5) stages. In addition, the biomass and production components were obtained. A randomized complete block design was used, with three cultivars and six replications. SC2 obtained the best mean for the photochemical variables. SC2 was more efficient at both development stages in WUE, but the maximum iWUE values were obtained in SC3. The SC2 cultivar obtained the best responses in the main variables analyzed, resulting in a higher yield.

Silicon Sources and Bacterial Inoculants on Growth Parameters, Leaf Yield, Quality of Coriander (Coriandrum sativum L.) and Soil Adsorbed Silicon in Sandy Loam Soil

Aims: The objective of the present study was to investigate the effect of different silicon sources with and without microbial inoculants on growth parameters, leaf yield and quality of Coriander. Study Design: Factorial Completely Randomized Block Design (FCRD) was used in the present study with thirty-six treatments and three replications. Place and Duration of Study: The pot culture experiment was carried out in the Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore, India during January to March 2022. Methodology: A pot culture experiment was conducted with different silicon sources namely CaSiO3, MgSiO3 and Rice Husk Ash (RHA) at three levels (0, 50 and 100 mg Si kg-1) with and without two silicate solubilizing bacteria (SSB) and a zinc solubilizing bacterium (ZSB) at 2 kg ha-1 with coriander CO (CR) 4. The influence of the treatments on growth parameters, leaf Si content, leaf yield, total soluble sugar content of leaf and soil adsorbed Si were investigated at 25 and 50 DAS. Results: The results revealed a significant influence of Si sources with bacterial inoculants. The plant height and SPAD index values were the highest by the application of RHA­ @ 100 mg Si kg-­1 + SSB4 followed by CaSiO3 @ 100 mg Si kg-­1 + SSB4. All the sources increased the leaf Si as well as soil adsorbed Si and the effect was highly significant when Si sources were combined with SSB4 and other inoculants. Coriander leaf yield ranged from 4.32 to 8.24 g plant-1. The maximum leaf yield was recorded with the application of RHA @ 100 mg Si kg-­1 with SSB4 (8.24 g plant-1) followed by RHA @ 50 mg Si kg-­1 with SSB4 (7.67 g plant-1) and ­ CaSiO3 @ 100 mg Si kg-­1 with SSB4 (7.56 g plant-1). The effect of Si sources with bacterial inoculants on TSS content of leaf was significant with a maximum value of (38.23 mg g-1 DW) by RHA @ 100 mg Si kg-­1 + SSB4 followed by CaSiO3 @ 100 mg Si kg-­1 + SSB4 (36.10 mg g-1 DW). Conclusion: The current study revealed that the combined application of Si sources and microbial inoculants significantly enhanced the growth attributes, leaf Si, leaf yield, leaf quality of coriander and soil adsorbed Si. The leaf yield increase over control for RHA @ 100 mg Si kg-­1 with SSB4 was 88.92 per cent followed by RHA @ 50 mg Si kg-­1 with SSB4 (76.58%) and CaSiO3 @ 100 mg Si kg-­1 with SSB4 (73.82%). The research work needs further validation at the field level.

Evaluating the Use of Biostimulants for Indoor Hydroponic Lettuce Production

Biostimulant products have various reported benefits for plant production in the field or using hydroponic systems in protected structures. However, limited information is available describing their potential use for indoor farming applications. Considering that lettuce (Lactuca sativa) is one of the most popular crops produced in commercial indoor farms, the objective of this study was to compare growth and quality of lettuce grown indoors using nine biostimulant products derived from humic substances, amino acids, hydrolyzed proteins, or seaweed extracts. ‘Monte Carlo’, ‘Fairly’, and ‘Lalique’ lettuce were grown hydroponically for 30 to 33 days under a daily light integral, day/night temperature, relative humidity, and carbon dioxide concentration of ≈13 mol·m‒2·day‒1, 22/21 °C, 70%, and 800 µmol·mol‒1, respectively. There were no positive effects from using any of the biostimulant products evaluated in our study as growth (leaf area, leaf number, shoot diameter, and shoot and root dry weight), yield (shoot fresh weight), and quality (bolting, tipburn index, leaf color, and SPAD index) of treated plants were generally similar to those from the untreated control. Applications from one seaweed extract caused slight negative growth effects, possibly due to phytotoxicity. Cultivar differences showed that Fairly plants had the highest susceptibility to tipburn and bolting, and none of the biostimulant products countered these symptoms. Overall, the products evaluated provided marginal advantages for indoor hydroponic lettuce production.

Zinc Nutrition for Improving the Growth and Yield of Barnyard Millet (Echinochola frumantacea L.)

Aims: To evaluate the effect of various levels and methods of zinc fertilization in improving the growth and yield of barnyard millet at different growth stages.
 Study Design: Randomized Block Design (RBD) with three replications.
 Place and Duration of Study: A field experiment was conducted in the farmer’s field at Pasur village, Coimbatore district from January to April, 2022.
 Methodology: A field experiment was conducted with barnyard millet (Echinochloa frumentacea L.) var. MDU 1 by using different levels of ZnSO4 at 5, 10, 15, 20 and 25 kg ha-1 as basal soil application and foliar spraying of 0.25, 0.50 & 0.75% twice along with soil test based NPK as control in Randomized Block Design with three replications. The growth and yield parameters such as plant height, SPAD index, root length, lateral root length, root volume, no. of tillers, panicle length, panicle weight, 1000 grain weight, grain and straw yield were recorded as per standard protocols.
 Results: Application of soil test based NPK + 20 kg ZnSO4 ha-1 performed better in increasing the plant height (157.0 cm), SPAD index (46.3), root length (21.1 cm), lateral root length (16.3 cm), root volume (3.80 cc) and yield attributes like number of tillers (5.06), panicle length (17.6 cm), panicle weight (29.2 g) and 1000 seed weight (3.89g) of barnyard millet. Higher grain (2606 kg ha-1) and straw yield (3411 kg ha-1) was also registered with the addition of soil test based NPK+20 kg ZnSO4 ha-1 which was 27.1% increase over NPK.
 Conclusion: Basal soil application of soil test based NPK + 20 kg ZnSO4 ha‑1 was found optimal and economical for improving the growth and yield of barnyard millet variety MDU 1.

Can 2,4-D promote the hormesis effect in upland rice?

This study aimed to evaluate the influence of low doses of 2,4-D on the agronomic traits of upland rice applied at different stages of crop growth. The work was carried out in a randomized completly blocks, and consisted of the application of 5 low doses of the 2,4-D herbicide (0, 0.68, 1.36, 2.04, 3.40 and 5.44 g acid equivalent (e.a.) ha−1) in two stages of rice development (tillering and floral differentiation). Nitrogen contentes in leaves, SPAD index and yield are higher when low doses of 2,4-D is applied in the tillering stage. Application of 2,4-D at a dose of 2.04 g a.e ha−1 results in a 19% increase in the number of spikelet per panicle. On the other hand, there is no effect of the application of low doses of 2,4-D on height, number of stems, active tillering and weight of 100 seeds. Our results contribute to increase knowledge of the hormesis effect in plants in order to increase crop yield.

Evaluation of Roholtiella sp. Extract on Bell Pepper (Capsicum annuum L.) Yield and Quality in a Hydroponic Greenhouse System.

This study was carried out to investigate the impacts of cyanobacteria (Roholtiella sp.) high-value product extract (HVPE) and water resuspended biomass WRB treatments on bell pepper production using the hydroponic system under greenhouse conditions. Six cyanobacteria treatments (6 ml L−1, 4 ml L−1, and 2 ml L−1 – HVPE, 6 ml L−1, 4 ml L−1, and 2 ml L−1 – WRB, and TR0 as control) were evaluated using the foliar application method. The results showed that foliar application of HVPE with treatments of 2 ml L−1, 4 ml L−1, and 6 ml L−1 produced significantly higher values of physical growth parameters of bell pepper (BP) plants (shoot length, the number of leaves, plant leaf length, plant leaf width, and the diameter of the shoot), SPAD index, yield components (the fruit length, fruit width, the number of fruit per plant, and fresh weight per fruit), biochemical composition [ascorbic acid, phenolic acid, and total soluble solids (TSS)], and the total yield compared to the control group TR0. Also, significant higher values of growth parameters (shoot length, the number of leaves, plant leaf length, plant leaf width, the diameter of the shoot), SPAD index, yield components (the fruit length, fruit width, the number of fruits per plant, and fresh weight per fruit), biochemical composition [ascorbic acid, phenolic acid, and total soluble solids (TSS)], and the total yield were obtained with foliar spraying WRB at 2 ml L−1, 4 ml L−1, and 6 ml L−1 compared to the control group TR0. Consequently, the treated bell pepper with Roholtiella sp. HVPE and WRB were more efficient in enhancing production and chemical constituents compared with the control group.

Soil warming and straw return impacts on winter wheat phenology, photosynthesis, root growth, and grain yield in the North China Plain

Soil temperature rise caused by global warming is one of the most serious threats to crop physiology and production. Straw return is considered as a potential strategy to improve soil health and agricultural productivity. However, little is known about their interactive effects on wheat growth and production, which limits the development of strategies and technological innovations for future food security. Therefore, in the two wheat seasons from 2018 to 2020, with or without straw return, the heating cable was laid at a depth of 20 cm to increase the soil temperature by 3.8 ℃, and the phenology, photosynthesis, root growth, and grain yield of winter wheat were studied. Soil warming advanced the anthesis date by one week and promoted pre-anthesis wheat growth and dry matter transportation. However, soil warming decreased post-anthesis duration, leaf area index, SPAD, net photosynthesis, and spectral vegetation indexes. Therefore, post-anthesis dry matter accumulation and grain filling were inhibited, lowering the 1000-grain weight and harvest index. Furthermore, the post-anthesis root weight, length, surface area densities and root to shoot ratio were also decreased under soil warming. Finally, soil warming reduced the grain yield by 35.2% in the dry 2018–2019 year. However, the wheat growth characteristics were considerably higher and no difference in grain yield was detected among treatments in the wet 2019–2020 season, indicating that increased precipitation may offset the adverse effect of soil warming on wheat yield. Straw return increased aboveground biomass, but had no effect on wheat yield, probably because the positive effects were limited in the short experimental duration. The findings suggested that soil warming would promote pre-anthesis wheat growth but accelerate post-anthesis wheat senescence, affect dry matter transportation and accumulation, eventually reducing wheat yield in the NCP, especially under dry condition.

Wheat Varietal Response to Relative SPAD Index (RSI) and Relative Normalized Difference Vegetation Index (RNDVI) under Variable Nitrogen Application and Terminal Heat Stress along with Yield Repercussion

Nitrogen (N) deficiency and heat stress (HS) are major abiotic stresses that affect the quantity and quality of wheat grains. This study was conducted to examine wheat varietal response to RSI and RNDVI at the anthesis stage and their relationship to yield and yield-related traits under variable N supply and terminal heat stress. Twelve wheat varieties were evaluated in 2016–2017 and 2017–2018 at the National Agricultural Research Centre (NARC), Islamabad, Pakistan. The experiment was divided into three sets, i.e., N120 (120 kg N/ha), N60 (60 kg N/ha) and N0 (0 kg N/ha), based on the nitrogen fertilizer application. The physiological and yield-related parameters were recorded. Mean grain yield for all twelve varieties, averaged from two years of data, ranged between 1655.0 and 3890.1 kg/ha. Maximum RSI (0.99), RNDVI (1.03) and GY (3890.9 kg/ha) were recorded for FSD-08, while AARI-11 showed minimum RSI (0.50), RNDVI (0.56) and GY (1396.40 kg/ha). In the present study, mean CTD was lower, at N0 (3.57 °C), followed by N60 (5.07 °C) and N120 (5.47 °C) on average for the two years of data. The strong positive correlation of RSI and RNDVI with grain yield at R2 = 0.73 and R2 = 0.49 suggest that these parameters can be used as efficient and precise selection criteria for identifying nitrogen-use-efficient wheat varieties under terminal heat-stress conditions. This work will help the researchers to identify and develop nitrogen-use-efficient and thermos-tolerant wheat cultivars by minimizing the negative impacts of heat stress at the anthesis stage.

Plant-Derived Biostimulants Differentially Modulate Primary and Secondary Metabolites and Improve the Yield Potential of Red and Green Lettuce Cultivars

The use of biostimulants in modern agriculture has rapidly expanded in recent years, owing to their beneficial effects on crop yield and product quality, which have come under the scope of intensive research. Accordingly, in the present study we appraised the efficacy of two plant-derived biostimulants, the legume-derived protein hydrolysates Trainer® (PH), and the tropical plant extract Auxym® (TPE) on two lettuce cultivars (green and red salanova®) in terms of morpho-physiological and biochemical traits (primary and secondary metabolites). The two cultivars differed in their acquisition capacity for nitrate and other beneficial ions, their photosynthetic and transpiration rates, and their ability to synthetize and accumulate organic acids and protective metabolites. The biostimulant effect was significant for almost all the parameters examined but it was subjected to significant cultivar × biostimulant interactions, denoting a cultivar-dependent response to biostimulant type. Notwithstanding this interaction, biostimulant application could potentially improve the yield and quality of lettuce by stimulating plant physiological processes, as indicated by the SPAD index (leaf chlorophyll index), ACO2 (assimilation rate), E (transpiration), and WUEi (intrinsic water use efficiency), and by increasing concurrently the plant mineral content (total N, K, Ca, Mg) and the biosynthesis of organic acids (malate, citrate), phenols (caffeic acid, coumaroyl quinic acid isomer 1, dicaffeoylquinic acid isomer 1), and flavonoids (quercetin-3-O-glucuronide, quercetin-3-O-glucoside). Biostimulant action may facilitate the bio-enhancement of certain lettuce cultivars that are otherwise limited by their genetic potential, for the accumulation of specific compounds beneficial to human health.

Growth of urochloa irrigated in clayey and sandy soil submitted to nutritional management in the cerrado

The reduction in water supply in specific areas and the high costs of agricultural inputs resulted in the need for agronomic management capable of reducing the pressure on water resources and promoting economic development. The objective of this work was to evaluate the response of Urochloa brizantha cv. Marandu grown in clayey and sandy soils submitted to nutritional and water management in the municipality of Rio Verde, state of Goiás. The treatments consist in combining two levels of fertilization (A1: 30, 7 and 36 and A2: 45, 10.5 and 54 of NPK per Mg of DM produced,) and seven water depths (0%; 25%; 50%; 75%; 100%; 125% and 150% of crop evapotranspiration (ETc)), in four replications. Crop performance was evaluated employing SPAD index, plant height, leaf length, leaf width, neutral detergent crude fiber, and dry matter. The rise in the irrigation depths significantly affected the performance of the forage and despite not having a significant difference, the production of dry matter may be higher when in soil with A2 fertilization. A significant influence was observed in the number of seedlings emergence from 7 to 21 days in Sandy soil as a function of clayey soil, on chlorophyll, and plant height as a function of A2 fertilization concerning A1 and irrigation depths in all analyzed variables.