SPAD Readings Research Articles

Foliar Nourishment with Different Potassium Sources to Maximize Yield Through Improving Nutrient Uptake in Citrus Aurantifolia Trees Grown in Potassium-Deficient Soil

AbstractPurpose: Based on its crucial regulatory role in several biochemical processes, potassium (K) is considered to greatly influence fruit yield and quality. Methods: Two field experiments were carried out in two seasons (2021 and 2022) to explore the response of lemon (Baladi cv.) trees grown in K-deficient soil to four different K fertilizer sources applied individually as a foliar spray. K citrate (KC1 = 1.3 vs. KC2 = 2.6 g L− 1), K nitrate (KN1 = 1.5 vs. KN2 = 3.0 g L− 1), K tartrate (KT1 = 1.5 vs. KT2 = 3.0 g L− 1), and K thiosulfate (KS1 = 1.25 vs. KS2 = 2.5 g L− 1) were applied three times, and the treated trees were compared with untreated trees. This study was established with a randomized complete block design (RCBD) using four replicates. Results: The findings revealed that the KC treatment, regardless of dosage, showed clear superiority in terms of the values for the leaf phosphorus (%), manganese, and zinc contents (mg kg− 1), as well as fruit firmness, fruit dry matter, and total soluble solids in both seasons. In second place was the KT treatment, which yielded the best values for fruit length and width in 2021, the best values for leaf nitrogen and iron contents and fruit weight and volume in 2022, and the best values regarding variable fluorescence by maximum fluorescence, relative chlorophyll content (SPAD readings), the photosynthetic performance index, total acidity, and vitamin C in both seasons. Furthermore, the highest total lemon yield and leaf potassium contents were achieved with the KN treatment in both seasons. The heat map illustrating that most of the studied characteristics were positively and significantly correlated with total lemon yield (TLY). Conclusions: The KN treatment, closely followed by the KC treatment, is regarded to be the best treatment for most of the studied trails.

Non-Invasive Detection of Nitrogen Deficiency in Cannabis sativa Using Hand-Held Raman Spectroscopy

Proper crop management requires rapid detection methods for abiotic and biotic stresses to ensure plant health and yield. Hemp (Cannabis sativa L.) is an emerging economically and environmentally sustainable crop capable of yielding high biomass. Nitrogen deficiency significantly reduces hemp plant growth, affecting photosynthetic capacity and ultimately decreasing yield. When symptoms of nitrogen deficiency are visible to humans, there is often already lost yield. A real-time, non-destructive detection method, such as Raman spectroscopy, is therefore critical to identify nitrogen deficiency in living hemp plant tissue for fast, precise crop remediation. A two-part experiment was conducted to investigate portable Raman spectroscopy as a viable hemp nitrogen deficiency detection method and to compare the technique’s predictive ability against a handheld SPAD (chlorophyll index) meter. Raman spectra and SPAD readings were used to train separate nitrogen deficiency discrimination models. Raman scans displayed characteristic spectral markers indicative of nitrogen deficiency corresponding to vibrational modes of carotenoids, essential pigments for photosynthesis. The Raman-based model consistently predicted nitrogen deficiency in hemp prior to the onset of visible stress symptoms across both experiments, while SPAD only differentiated nitrogen deficiency in the second experiment when the stress was more pronounced. Our findings add to the repertoire of plant stresses that hand-held Raman spectroscopy can detect by demonstrating the ability to provide assessments of nitrogen deficiency. This method can be implemented at the point of cultivation, allowing for timely interventions and efficient resource use.

IMPACT OF DIFFERENT ZINC APPLICATION METHODS AND PHOSPHORUS DOSES ON GROWTH, YIELD AND GRAIN ZINC CONTENTS OF WHEAT

Wheat is a staple crop of around half of the world's population. About 30 percent of the world’s population is suffering from Zn deficiency. Zn deficiency problems can be encountered by agronomic and genetic biofortification. Phosphorus (P) is an important plant macronutrient and has an antagonistic relationship with Zn. A field study was performed to evaluate the impact of different Zn application methods and P doses on growth, yield, and grain Zn contents of wheat at the Agronomic Research Farm, University of Agriculture Faisalabad, Pakistan, using a high accumulation wheat variety Zincol-2016. Three doses of P (100, 150, and 200% of recommended P) along with three Zn application methods (seed priming, soil mixing, and foliar application) were applied to wheat using randomized complete block design (RCBD) with three replicates under split-plot arrangement. All agronomic practices were kept normal and uniform for all treatments. Parameters including growth, yield, and Zn content in wheat grains were monitored using standard protocols. The results were evaluated using Fisher’s analysis of variance at a 5% probability level. A comparison of means of treatments was performed using the least significant difference (LSD) test. The highest value of SPAD reading (56.38) was noted in treatment where Zn was applied as priming and P was applied at 200%. Maximum crop growth rate (63.17) was observed in P3 where Zn was applied as mix in soil. Maximum spike length (14.25), spikelets per spike (17.67), and Zn concentration were observed in P3 as a result of foliar application of Zn. Highest grain weight per spike (1.89g), no. of tillers (691.01), grain yield (4.09 t ha-1), biological yield (11.01 t ha-1), harvest index (36.54%) and NDVI (0.42 were observed in P3 where Zn was applied as soil mix.

Evaluation of the Performance of Okra (Abelmoschus esculentus l. Moench) Genotypes for Growth, Yield, and Quality Parameters

The present investigation was carried out to evaluate the performance of okra genotypes for growth, yield and quality parameters. Okra is often cross-pollinated and is grown primarily for its fruits, which have various culinary uses. Tender fruits are commonly boiled or used in sliced and fried dishes. Okra fruits are also dried in the sun, canned, or dehydrated for preservation during the off-season. The study was carried out at New Orchard, Main Agricultural Research Station, UAS, Raichur, during late Kharif 2021-22 using thirty-one genotypes (including the check variety Arka Anamika) and laid out in Randomized Block Design (RBD) with three replications. The analysis of variance revealed significant differences (p < 0.05) among genotypes for all traits studied. Genotype OPL-2127 recorded the highest plant height (96.52 cm), stem girth (14.26 mm), number of leaves per plant (23.20), leaf area index (3.08), number of nodes per plant (13.60), chlorophyll content (59.61 SPAD readings), fruit length (18.69 cm), fruit yield per plant (293.53 g), fruit yield per hectare (16.4 t) and it is found to be superior over the other okra genotypes under the study. The highest fruit girth (41.36 mm) was noted in the genotypes OPL-2108. The genotype OPL-2119 recorded the minimum number of days to 50 per cent flowering (38.00) which indicates the earliness of the genotypes. OPL-2023 recorded the highest fibre content (16.09 %). The genotypes OPL-2127, OPL-2121, OPL-2116, OPL-2115 and OPL-2113 were found to be superior okra genotypes for yield and quality and they can be used in future breeding and crop improvement program.

Morphological Characteristics and Drought Tolerance of the Diploid and Tetraploid Angelonia angustifolia

Angelonia (Angelonia angustifolia) is an important potted flowering plant or bedding plant widely used in tropical and subtropical regions. However, most Angelonia cultivars have relatively small flowers and demonstrate limited drought tolerance in root-restricted environments such as small containers. Polyploid plants often exhibit larger flowers and enhanced drought tolerance. In this study, Angelonia ‘Serena White’ seeds and ‘Serena Purple’ seedlings were treated with 0.1% and 0.2% colchicine to induce polyploid lines, respectively. The resulting tetraploids had larger pollen and flowers, along with thicker, greener leaves distinguished by serrated edges, longer stomata, and lower stomatal density compared with diploid ‘Serena White’ and ‘Serena Purple’ plants. Both diploid and tetraploid plants subjected to a 20% volumetric water content (VWC) treatment exhibited smaller leaves, higher SPAD-502 readings, and a decreased number of flowers compared with those subjected to 40% VWC treatment. Moreover, tetraploids had higher photosynthetic rates than diploids under both 20% and 40% VWC conditions. When grown in 0.8-L containers, tetraploid plants required fewer watering events and had thicker, erect stems with larger flowers than diploids, even under a 20% VWC treatment. Colchicine-induced polyploidization presents a promising method to potentially enhance drought tolerance in angelonia.

Phenotypic Dissection of Drought Tolerance in Virginia and Carolinas within a Recombinant Inbred Line Population Involving a Spanish and a Virginia-Type Peanut Lines

Peanut (Arachis hypogaea L.) is a rainfed crop grown in both tropical and subtropical agro-climatic regions of the world where drought causes around 20% yield losses per year. In the United States, annual losses caused by drought are around $50 million. The objective of this research was to (1) identify genetic variation for the normalized difference vegetation index (NDVI), canopy temperature depression (CTD), relative chlorophyll content by SPAD reading (SCMR), CO2 assimilation rate, and wilting among recombinant inbred lines (RILs) derived from two diverse parents N08086olJCT and ICGV 86015, to (2) determine if the physiological traits can be used for expediting selection for drought tolerance, and (3) experimental validation to identify lines with improved yield under water-limited conditions. Initially, 337 lines were phenotyped under rainfed production and a selected subset of 52 RILs were tested under rainout shelters, where drought was imposed for eight weeks during the midseason (July and August). We found that under induced drought, pod yield was negatively correlated with wilting and CTD, i.e., cooler canopy and high yield correlated positively with the NDVI and SPAD. These traits could be used to select genotypes with high yields under drought stress. RILs #73, #56, #60, and #31 performed better in terms of yield under both irrigated and drought conditions compared to check varieties Bailey, a popular high-yielding commercial cultivar, and GP-NC WS 17, a drought-tolerant germplasm.

Does humic acid foliar application affect growth and nutrient status of water-stressed maize?

Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by-product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar-applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging.

Nitrogen Gradient Optimization with Kharif Legumes on Agronomic Parameters in Zero-till Rabi Maize

Background: With the SDG goals of using the generated output of one season on other season for managing the resource potential so to unlock the crop productivity is being the best alternative that need to be looked out in present climate change scenario. So, the present trial is focuses on the lines of residue management of legumes on maize sequence with nitrogen as the driving gradient in 2021-22 and 2022-23. Methods: The experiment is laid out in split-plot design with 18 treatments consisted of C1N1: groundnut100% RDN-maize, C1N2: groundnut75% RDN-maize, C2N1: soybean100% RDN-maize, C2N2: soybean75% RDN-maize, C3N1: greengram100% RDN-maize, C3N2: greengram75% RDN-maize as main-plots and 3 subplots viz.100% RDN, 125% RDN, 150% RDN (kharif and rabi respectively) during two years of study. Result: Among the different cropping systems, the preceding kharif greengram with 100% RDN on rabi zero-till maize showed higher growth parameters i.e. plant height, leaf area, leaf chlorophyll content (SPAD reading), dry matter at 30,60,90 DAS and at harvest and yields in both years. However, with respect to nitrogen levels, application of 150% RDN to rabi maize showed significantly higher growth and yields followed by 125% RDN and lowest was seen in 100% RDN in rabi respectively. On the other hand, the interaction effect was found significant at only 60 DAS in both years.

Morphological and Physiological Responses of Two Penstemon Species to Saline Water Irrigation

Penstemon, with more than 250 species native to North America, holds significant aesthetic and ecological value in Utah, supporting diverse pollinators. Despite their significance, the survival of penstemon is threatened by challenges such as habitat loss, climate change, and Utah’s naturally high soil salinity. To address these challenges and understand their adaptability, this study evaluated the salt tolerance of two penstemon species [Penstemon davidsonii (Davidson’s penstemon) and Penstemon heterophyllus (foothill penstemon)] under controlled greenhouse conditions. The aim was to develop baseline information for nursery production and landscape use that utilize reclaimed water for irrigation. Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.0 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. Half of the plants were harvested after four irrigation events, and the remaining plants were harvested after eight irrigation events. At harvest, visual rating (0 = dead and 5 = excellent without foliage salt damage), plant width, number of shoots, leaf area, shoot dry weight, leaf greenness [Soil Plant Analysis Development (SPAD)], stomatal conductance, and canopy temperature were collected to assess the impact of salinity stress. In both species, salt damage was dependent on the salinity levels and length of exposure. After four irrigation events, both species exhibited foliage damage that increased in severity with rising EC. The most severe damage was observed in plants receiving saline solution at an EC of 10.0 dS·m−1. After eight irrigation events, P. davidsonii exposed to a saline solution with an EC of 10.0 dS·m−1 received a visual rating of 0, whereas P. heterophyllus had a visual rating of 0.4. Both species exhibited salinity-induced effects, with variations observed in the specific parameters and the degree of response. Penstemon davidsonii exhibited significant salinity stress, as indicated by reduced leaf area, shoot dry weight, SPAD reading, and stomatal conductance with increasing EC of the saline solution. In addition, in both species, at both harvests, canopy temperatures increased either linearly or quadratically by 8% to 36% as the EC levels of the saline solution increased. These results indicate that P. davidsonii was more sensitive to salinity stress than P. heterophyllus.

Better estimation of evapotranspiration and transpiration using an improved modified Priestly-Taylor model based on a new parameter of leaf senescence in a rice field

Evapotranspiration (ET) is at the heart of the global water, energy, and carbon cycles. As ET is difficult and expensive to measure, it is crucial to develop estimation models that can be widely applied. Currently, an improved Priestley-Taylor (PT) model considers soil moisture stress, temperature constraints, and leaf senescence; however, its parameter (fs) for simulating crop senescence is based on empirical values, making it difficult to apply to different varieties and complex external conditions and thus challenging to generalize. We improved the parameters fs in the original model based on the chlorophyll decomposition that accompanies crop senescence through easily observable SPAD values (Soil-Plant Analysis Development readings) in the field. We validated the improved model by obtaining ET of different rice varieties in 2022 and 2023 using the energy balance residual method at the Free Air Concentration Enrichment Experimental (FACE) Facility located in Yangzhou City, China. The results showed that the simulation of leaf senescence using SPAD values was feasible and could be extended to different varieties. The new model using improved leaf senescence parameter for estimating ET and transpiration (T) in three plots (2022 and 2023) exhibited slightly enhanced accuracy, particularly at the later stages of crop growth. Moreover, the higher the T/ET ratio of the cropland, the more significant the improvement. This new development enhances the ability of PT models to estimate ET and T using readily available field observations and provides some suggestions for wider application in the field for other crop species.

The Effect of Nitrogen-Enriched Partially Burnt Paddy Husk on Growth and Yield of Rice (Oryza Sativa)

Paddy husk can be defined as a material that can be easily accessed by small-scale, resource-poor farmers in Sri Lanka. It is being produced in large quantities during the production of milled rice as by-products. Currently, most paddy husk is underutilized or left unused due to their intrinsic properties. Partially burnt paddy husk (PBPH) is an organic material that is prepared by incomplete combustion of paddy husk. The use of PBPH as a soil amendment to fix soil fertility problems has been well recognized. It contains a higher porous structure and an enhanced adsorption capacity, therefore, has the ability to slow down nutrient leaching by capturing nutrients in its porous structure. In the present study, a farmer-friendly, biochar-based organic nitrogen fertilizer was developed by nitrogen-enriching PBPH using nitrogen-rich liquid fertilizers in order to determine its effect on the growth and yield of rice. A pot experiment was conducted at the Rice Research and Development Institute, Bathalagoda based on a Completely Randomized Design (CRD) with eight treatments and five replicates.The treatments included T1 (Gliricidia extract+PBPH), T2 (cow urine+PBPH), T3 (poultry manure+PBPH), T4 (fish tonic+PBPH), T5 (compost tea+PBPH), T6 (urea+PBPH), T7 (PBPH only) and T8 (no treatment). Nitrogen (N) content of raw materials, liquid fertilizers, N-enriched PBPH, and N uptake of plants were determined using Kjeldahl method. Phosphorus (P) and potassium (K) contents of PBPH were determined by using UV-Visible Spectrophotometer and Flame Photometer, respectively. Plant height and greenness (SPAD results) were recorded as growth parameters and finally, number of tillers, panicles, grains per pot and grain weight per pot were obtained as the yield parameters. Significantly, the highest N content was found in urea liquid fertilizer (3.42%) whereas the lowest was found in Gliricidia extract (0.35%). Significantly, the highest N content (1.735%) of N-enriched PBPHs was found in T6 (urea+PBPH), while the lowest (0.058%) was found in T7 (PBPH only). Significantly, the highest N uptakes (1.98% and 1.86%) of rice plants were found in T6 (urea+PBPH) and T4 (fish tonic+PBPH) respectively while the lowest (0.56%) was found in the T8 (no treatment). SPAD readings, the number of panicles, tillers and grain yield, and biomass were significantly increased in all treatments over T7 (PBPH only) and T8 (no treatment) treatments. The overall study concluded that the application of N-enriched PBPH has improved the growth and yield of rice, therefore it can be used as a farmer-friendly, sustainable, and organic nitrogen source in paddy cultivation in Sri Lanka.
 Keywords: Nitrogen, Partially burnt paddy husk, Nitrogen enrichment

Exploring the Effect of Humic Acid on Chlorophyll Levels in Japanese Mint under Drip and Flood Irrigation Amidst Water and Nutrient Constraints

A field experiment on Mentha (Mentha arvensis L.) was conducted during the spring seasons of 2022 and 2023 at G.B. Pant University of Agriculture and Technology, Pantnagar. The objective was to investigate the impact of foliar spray of humic acid on SPAD values under conditions of limited water and nutrients. The experiment comprised two drip irrigation levels (80% and 100% of crop evapotranspiration) and four nutrient management practices. These practices included: 25% NPK basal + 75% NPK fertigation, 50% NPK basal + 50% NPK fertigation, No basal + 75% NPK fertigation + three foliar sprays of humic acid at 0.3%, and 25% NPK basal + 50% NPK fertigation + three foliar sprays of humic acid at 0.3%. The experiment was laid out in a randomized block design with three replicates (factorial), and an extra control was included. The control followed conventional practices, where the crop received recommended doses of fertilizers (N: P2O5: K2O @ 120:60:40 kg/ha) and was irrigated at an IW: CPE ratio of 1.2 with a 5 cm irrigation depth. Significantly higher SPAD values were observed when the crop was irrigated at 100% ETc level of drip irrigation and with nutrient management practices involving foliar application of humic acid, compared to 80% ETc level of drip irrigation and total NPK supply through chemical fertilizers, respectively. At harvest, crops irrigated at 100% ETc level recorded SPAD readings that were 11.1% and 18% higher than those irrigated at 80% ETc level during 2022 and 2023, respectively. The humic acid application helped to maintain the SPAD values even after a 25% reduction in nutrient dosage. SPAD values for control were significantly lower than the combination of best nutrient management practices with either 80 or 100% ETc level of drip irrigation.

High-Throughput Analysis of Leaf Chlorophyll Content in Aquaponically Grown Lettuce Using Hyperspectral Reflectance and RGB Images

Chlorophyll content reflects plants’ photosynthetic capacity, growth stage, and nitrogen status and is, therefore, of significant importance in precision agriculture. This study aims to develop a spectral and color vegetation indices-based model to estimate the chlorophyll content in aquaponically grown lettuce. A completely open-source automated machine learning (AutoML) framework (EvalML) was employed to develop the prediction models. The performance of AutoML along with four other standard machine learning models (back-propagation neural network (BPNN), partial least squares regression (PLSR), random forest (RF), and support vector machine (SVM) was compared. The most sensitive spectral (SVIs) and color vegetation indices (CVIs) for chlorophyll content were extracted and evaluated as reliable estimators of chlorophyll content. Using an ASD FieldSpec 4 Hi-Res spectroradiometer and a portable red, green, and blue (RGB) camera, 3600 hyperspectral reflectance measurements and 800 RGB images were acquired from lettuce grown across a gradient of nutrient levels. Ground measurements of leaf chlorophyll were acquired using an SPAD-502 m calibrated via laboratory chemical analyses. The results revealed a strong relationship between chlorophyll content and SPAD-502 readings, with an R2 of 0.95 and a correlation coefficient (r) of 0.975. The developed AutoML models outperformed all traditional models, yielding the highest values of the coefficient of determination in prediction (Rp2) for all vegetation indices (VIs). The combination of SVIs and CVIs achieved the best prediction accuracy with the highest Rp2 values ranging from 0.89 to 0.98, respectively. This study demonstrated the feasibility of spectral and color vegetation indices as estimators of chlorophyll content. Furthermore, the developed AutoML models can be integrated into embedded devices to control nutrient cycles in aquaponics systems.

The implementation of the SPAD-502 Chlorophyll meter for the quantification of nitrogen content in Arabica coffee leaves

The utilization of a non-destructive SPAD-502 chlorophyll meter, which enables the measurement of nitrogen status in plant leaves, has gained popularity in agronomic crops. Its application to horticultural crops like coffee remains relatively uncommon. The device provides quick and real-time measurements, helping to provide on-time nitrogen fertilizer to coffee plants before deficiency signs occur. Coffee leaves are characterized by thick and waxy leaves, together with many layers of tree crown. Therefore, the objective of this study was to develop a method for measuring nitrogen levels in coffee plants using the SPAD-502 Chlorophyll meter for an appropriate nitrogen fertilizer application rate in Arabica coffee plants.•Coffee trees were separated into upper, middle and lower levels. Data on SPAD values and total nitrogen were analyzed.•Pearson Correlation Coefficient (R), Coefficient of Determination (R2) and linear regression were calculated for different three levels of both SPAD-502 and total nitrogen values.•The results revealed a strong correlation (R2 = 0.63) between the SPAD readings of coffee leaves obtained from the upper canopy and their nitrogen content.These findings can provide a good concept of which coffee crown level will be a better part for measuring N content using a SPAD-502 Chlorophyll meter.

Assessing of Residual Legume Effect on Growth and Yield Parameters of rabi Maize under Irrigated Conditions

An experiment was conducted to study the residual influence of preceding legumes and nitrogen levels on growth and yield parameters of rabi maize at Maize Research Centre, AgriculturalResearch Institute, Rajendranagar, Hyderabad, during kharif and rabi of 2021 and 2022. The experiment was laid out in split-plot design with 18 treatments consisted of C1N1: groundnut100% RDN- maize, C1N2: groundnut75% RDN- maize, C2N1: soybean100% RDN- maize, C2N2: soybean75% RDN- maize, C3N1: greengram100% : greengram100% RDN- maize, C3N2: greengram75% RDN- maize as main-plots and 3 subplots viz.100% RDN, 125% RDN, 150% RDN (kharif and rabi respectively) during twoyears of study. Among the different cropping systems, the preceding kharif greengram with 100% RDN on rabi zero-till maize showed higher growth interms i.e. plant height, leaf area, leaf chlorophyll content (SPAD reading) at 30 DAS, cob length, cob girth and yield in both years. However, with respect to nitrogen levels, application of 150% RDN to rabi maize showed significantly higher growth and yield followed by 125% RDN and lowest was seen in 100% RDN in rabi respectively. On the other hand, the interaction effect with the preceding legume residues on succeeding rabi maize with addition of varied nitrogen levels was found non-significant in 2021-22 and 2022-23.

Effect of Varied Levels of Gibberellin, Anti-Gibberellin and Cytokinin on Growth and Tuberization in Potato

Plant hormones play a significant role in potato tuberization. While Gibberellins inhibit tuberization, anti-gibberellins (PBZ and CCC) and cytokinins promote tuberization in potato. The experiment demonstrated the clear roles of these hormones in facilitating tuberization in potato. Treatment with 25 ppm GA significantly increased plant height (44.56 cm) compared to the control (32.22 cm), while CCC, a Gibberellins (GA) inhibitor, reduced the plant height by inhibiting GA-induced stem elongation. Hormonal treatments affected the number of nodes, leaves, branches, SPAD readings, stem girth, root length and root weight with significantly higher values observed compared to the control. 50 ppm GA showed the highest number of stolons per plant (6.33), but surprisingly resulted in a few tubers per plant (1.7) compared to the control (1.8). However, both 5 ppm and 10 ppm BAP led to significantly more tubers per plant (2.1 and 3.2 respectively), as did 5 ppm and 10 ppm Kinetin (2.8 and 2.6 respectively). Regarding tuber fresh weight, all treatments except CCC and higher concentration of kinetin showed significantly higher fresh weight compared to control. In summary, 50 ppm Gibberellins increased the stolon number, while 10 ppm BAP increased the tuber number and fresh weight in potato

Influência do nitrogênio na produtividade do pimentão em condições de campo aberto no outono-inverno

ABSTRACT Nitrogen (N) deserves special attention in the fertilization recommendation for bell peppers, as it is the nutrient absorbed in greater quantity, standing out for the amount required and the functions it performs in the plant. The objective was to evaluate the influence of nitrogen applied as top dressing on bell pepper production in open field during the autumn/winter period. The experiment was conducted in Red-Yellow Argisol. A randomized complete block design with four replications was used. Treatments consisted of nitrogen rates applied as top dressing (0, 75; 150; 300; and 450 kg/ha). Nitrogen increased the number and fresh mass of fruits per plant. The SPAD Reading increased with the increment of nitrogen rates in the three evaluation periods and with the evaluation period. Bell peppers grown during the autumn/winter period showed high productive potential associated with nitrogen rates higher than currently recommended. The yield of marketable fruits increases until 214 kg/ha of N. The critical level for the SPAD reading varied with the age of the plants, with estimated critical values of 53.2, 66.5, and 61.9 at 35, 56, and 154 days after transplanting (DAT).

Predicting chlorophyll and nitrogen content in rice using multiple regression models

Chlorophyll and nitrogen (N) content in rice at critical crop growth stages are important input parameters for crop growth and nutrient uptake models used to optimize N application. Hence, the study was conducted to predict chlorophyll and N content in rice using multiple regression-based models involving normalized difference vegetation index (NDVI), Soil Plant Analysis Development (SPAD), Customized leaf color chart (CLCC), chlorophyll and N content. An experiment was conducted with six varieties i.e. CR Dhan 312, CR Dhan 310, Lalat, Shatabdi, Swarna Shreya, CR Dhan 206 with four N levels (i.e. 0, 80, 100 and 120 kg N ha−1) in split plot design and replicated thrice. The NDVI, SPAD and CLCC readings were taken at 45, 49 and 54 days after transplanting (DAT). Plant sampling was done for estimating the chlorophyll and nitrogen content in laboratory following standard methodology. Multiple linear regressions were performed between NDVI, SPAD and CLCC readings and chlorophyll & N content in rice in different variables combinations. Multiple linear regression (MLR) models with two variables i.e. NDVI and SPAD predicted the chlorophyll and N content of rice varieties. The predicted values for nitrogen and chlorophyll were comparable to those obtained using models from individual varieties when combined data from six different varieties were used to create MLR models. The study concludes that variations in chlorophyll and N concentrations in rice can be estimated using data from optical sensors with notable accuracies.

Effect of Priming on Brassica rapa subsp. chinensis (Bok Choy) Seeds Germination

Brassica rapa subsp. Chinensis, commonly known as Bok Choy, is a nutrient-rich vegetable with substantial antioxidant content. Therefore, this study aimed to evaluate the effect of hydropriming and bio-nutri-priming using Sandwich compost leachate on seed germination, SPAD reading, and dry matter accumulation in 280 dwarf variants of Bok Choy seeds sourced from Green Eagle. The experimental process involved hydropriming with tap water, bio-nutri-priming using 0.2% Sandwich compost leachate, and a control group cultivated in soil without priming. A complete randomization design (CRD) with three replications assessed seed germination performance, SPAD, root and shoot dry matter, and root-to-shoot ratio. While there was no significant difference in the germination percentage (88.35±1.13%), the entire priming seeds exhibited a 2-day peak germination period, compared to 3 days for the non-priming counterparts. Bio-nutri-priming seeds showed faster median and mean germination times due to enhanced nutrient uptake. They further displayed high SPAD readings, suggesting a lack of toxic compounds. The dry matter production of all treated Bok Choy was similar because administered treatments did not interfere with plant growth and development. Therefore, applying bio-nutri-priming using Sandwich compost leachate positively affected seed germination performance, warranting its recommendation as a seeds priming solution.

Assessment of Growth, Flowering, Yield and Quality Parameters of Different Okra (Abelmoschus esculentus L.) Genotypes

The present investigation was carried out at New Orchard, Main Agricultural Research Station, UAS, Raichur, during late Kharif 2021-22 using thirty-one genotypes and laid out in Randomized Block Design (RBD) with three replications. The result of the study revealed that, there was significant differences (p < 0.05) among the genotypes for all the traits studied. Genotype OPL-2127 recorded the highest plant height (130.69 cm), stem girth (20.45 mm), number of leaves per plant (27.29), leaf area index (3.62), number of nodes per plant (16.04), chlorophyll content (64.26 SPAD readings), fruit length (18.69 cm), number of fruits per plant (16.10), harvesting period (63.50 days), fruit yield per plant (293.53 g), fruit yield per hectare (16.4 t) and it is found to be superior over the other okra genotypes under the study. The highest fruit girth (41.36 mm) and ten fruits weight (230.10 g) was noted in the genotypes OPL-2108 and OPL-2125, respectively. The genotypes OPL-2102 and OPL-2119 recorded the minimum number of days for first flower appearance (34.50) and days to 50 per cent flowering (38.00), respectively which indicates the earliness of the genotypes. OPL-2023 recorded the highest shelf-life (5.50 days) and fibre content (16.09%).