SPAD Readings Research Articles

Using processed fertilizers or composted poultry manure results in similar yields but contrasting nutrient budgets in organic cabbage production

Certified organic farmers who grow mixed vegetables often rely on composted manure as their primary nutrient source to build soil organic matter and long-term fertility, but this can result in excessive phosphorus inputs relative to processed organic fertilizers. We established a two-year experiment to compare two certified organic fertilizers − 13-0-0 (derived from hydrolyzed feather meal, meat meal, and blood meal) and 10-2-8 (same components as 13-0-0 in addition to bone meal and sulfate of potash) – and composted chicken manure added to provide 112 kg plant-available N ha−1 in organic cabbage production of Northern Florida. Crown diameter was highest with processed fertilizers in both years, whereas SPAD readings were highest with 13-0-0 in 2020. In both years, sap nitrate measured during the growing season was generally higher with processed fertilizers relative to the composted manure treatment. Marketable yield was highest with processed fertilizers for both years and nutrient concentrations at harvest were similar among treatments, except for nitrogen concentrations that were highest with 10-2-8 in 2021. Nutrient export generally followed differences in yields and was comparable for processed fertilizers and composted manure. Using composted manure resulted in large nutrient surpluses, as opposed to smaller surpluses for 10-2-8 and deficits of phosphorus and potassium for 13-0-0. Our results confirm that poultry manure composted directly onsite can result in comparable organic cabbage yields relative to processed fertilizers, although this resulted in important phosphorus surpluses when applied to meet crop N demand.

Genetic Relationship, SPAD Reading, and Soluble Sugar Content as Indices for Evaluating the Graft Compatibility of Citrus Interstocks

The interstock, a stock between the rootstock and scion, has a significant regulatory effect on the stock and scion, and its function is highly dependent on graft compatibility. To assess the graft compatibility of the interstock and scion, 'Yuanxiaochun' was top grafted onto 'Ponkan', 'Shiranuhi', 'Harumi', 'Tarocco', and 'Kumquat'. The results showed significant differences in the survival ratio and preservation ratio among different combinations. Grafting compatibility in the early stages of grafting was associated with the genetic relationship. The biomass accumulation revealed that the interstock could influence both the rootstock and the scion. The physiological and biochemical traits analysis suggested that SPAD reading and soluble sugar could be employed as preselected indices to evaluate graft compatibility in the late stage of grafting. These results indicated that the evaluation of graft compatibility was a dynamic process. The findings provided a new approach for studying the stock and scion interaction mechanisms mediated by interstock, and directly provided a theoretical and practical basis for the high-grafting of 'Yuanxiaochun' citrus.

Variable rate inorganic foliar fertilization effect on paddy leaves chlorosis, plant growth and yield performance

Foliar feeding has been growing in popularity and has been used to supplement the soil-based fertilizer applications to enhance the growth and yield of crops. However, spraying a high concentration of foliar fertilizer can cause a leaf burn effect while a low concentration of fertilizer application can show symptoms of nutrient deficiencies on the leaf. This study was conducted to determine the effect of foliar fertilization on paddy leaf chlorosis and its impact on plant growth and yield performances between variable rate application (VRA) and uniform rates of supplying the fertilizer. The experiment was performed for two planting seasons and had four nitrogen (N) treatments (50% fixed rate, 100% fixed rate, 150% fixed-rate, and VRA) that arranged in a randomized complete block design (RCBD) with four replications. Paddy leaf chlorosis counts, plant growth (plant heights, number of tillers, number of panicle and flower), and yield performances (grain yield, number of grains, 1000-grain weight, and number of spikelets) were collected and recorded. The results showed no sign of leaf burns, however, showed chlorosis condition on the paddy leaves for all the treatments. VRA had the lowest chlorosis counts and had the highest SPAD readings at every planting stage for both planting seasons. While for plant growth performance, VRA showed moderate plant heights however had a higher number of tillers, panicle, and flowers compared to uniform rate treatments. So, VRA significantly produced more yield compared to uniform rates in both planting seasons. Therefore, foliar fertilization of VRA performed better compared to the uniform rate treatments.

Evaluation of the Methods for Estimating Leaf Chlorophyll Content with SPAD Chlorophyll Meters

Leaf chlorophyll content (LCC) is an indicator of leaf photosynthetic capacity. It is crucial for improving the understanding of plant physiological status. SPAD meters are routinely used to provide an instantaneous estimation of in situ LCC. However, the calibration of meter readings into absolute measures of LCC is difficult, and a generic approach for this conversion remains elusive. This study presents an evaluation of the approaches that are commonly used in converting SPAD readings into absolute LCC values. We compared these approaches using three field datasets and one synthetic dataset. The field datasets consist of LCC measured using a destructive method in the laboratory, as well as the SPAD readings measured in the field for various vegetation types. The synthetic dataset was generated with the leaf radiative transfer model PROSPECT-5 across different leaf structures. LCC covers a wide range from 1.40 μg cm−2 to 86.34 μg cm−2 in the field datasets, and it ranges from 5 μg cm−2 to 80 μg cm−2 in the synthetic dataset. The relationships between LCC and SPAD readings were examined using linear, polynomial, exponential, and homographic functions for the field and synthetic datasets. For the field datasets, the assessments of these approaches were conducted for (i) all three datasets together, (ii) individual datasets, and (iii) individual vegetation species. For the synthetic dataset, leaves with different leaf structures (which mimic different vegetation species) were grouped for the evaluation of the approaches. The results demonstrate that the linear function is the most accurate one for the simulated dataset, in which leaf structure is relatively simple due to the turbid medium assumption of the PROSPECT-5 model. The assumption of leaves in the PROSPECT-5 model complies with the assumption made in the designed algorithm of the SPAD meter. As a result, the linear relationship between LCC and SPAD values was found for the modeled dataset in which the leaf structure is simple. For the field dataset, the functions do not perform well for all datasets together, while they improve significantly for individual datasets or species. The overall performance of the linear (LCC=a∗SPAD+b), polynomial (LCC=a∗SPAD2+b∗SPAD+c), and exponential functions (LCC=0.0893∗10SPADα) is promising for various datasets and species with the R2 > 0.8 and RMSE <10 μg cm−2. However, the accuracy of the homographic functions (LCC=a∗SPAD/b−SPAD) changes significantly among different datasets and species with R2 from 0.02 of wheat to 0.92 of linseed (RMSE from 642.50 μg cm−2 to 5.74 μg cm−2). Other than species- and dataset-dependence, the homographic functions are more likely to produce a numerical singularity due to the characteristics of the function per se. Compared with the linear and exponential functions, the polynomial functions have a higher degree of freedom due to one extra fitting parameter. For a smaller size of data, the linear and exponential functions are more suitable than the polynomial functions due to the less fitting parameters. This study compares different approaches and addresses the uncertainty in the conversion from SPAD readings into absolute LCC, which facilitates more accurate measurements of absolute LCC in the field.

Improving Nutrients Uptake and Productivity of Stressed Olive Trees with Mono-Ammonium Phosphate and Urea Phosphate Application

Nutritional status improvement is a surrogate approach to overcoming undesirable soil conditions. This study was performed in sandy clay loam soil that was characterized by certain undesirable parameters (ECe = 6.4 vs. 7.2 dS m−1, CaCO3 = 8.8 vs. 9.2%, and pH = 7.78 vs. 7.89) on olive (Olea europaea, Arbequina cv.) in the 2020 and 2021 seasons to investigate the influence of two highly soluble phosphorus fertilizers, mono-ammonium phosphate (MAP) and urea phosphate (UP). The treatments included 0.336, 0.445, and 0.555 kg tree−1 for MAP1, MAP2, and MAP3 and 0.465, 0.616, and 0.770 kg tree−1 for UP1, UP2, and UP3, respectively, in comparison to granular calcium super-phosphate (GCSP) at the recommended rate (0.272 kg P2O5 equal 1.75 kg tree−1). This experiment was established according to a randomized complete block design. Generally, our results indicated that both MAP and UP applications surpassed GCSP for all studied parameters except leaf copper uptake in the 2021 season. Moreover, among the HSPFs applied, it was found that applying the maximum levels gave the best results. However, MAP3 gave the maximum values for shoot length, SPAD reading, and dry fruit matter. Moreover, UP3 produced the best results for the leaf area, olive tree yield, total olive yield, total fresh weight, flesh weight (FlW), fruit length (FrL), and leaf Fe content in both seasons.

Morphology and Nitrogen Uptake and Distribution of Wheat Plants as Influenced by Applying Remedial Urea Prior to or Post Low-Temperature Stress at Seedling Stage

Wheat production is dramatically influenced by temperature. Low-temperature stress that frequently occurs seriously hampers the growth and development of wheat seedlings. In order to alleviate the damage of low temperature to wheat plant growth, remedial nitrogen was applied prior to or post low-temperature stress at seedling stage using controlled-temperature incubators to explore the difference in wheat morphology and nitrogen absorption and utilization efficiency. Nitrogen amendment significantly increased the leaf area, seedling height, tiller number and dry matter weight of wheat plants as compared with the treatment without nitrogen amendment under temperature stress. Remedial nitrogen applied prior to low-temperature stress (N-LT) was more conducive to increase the above parameters than that applied post low-temperature stress (LT-N). In addition, N-LT enhanced the ability of roots to absorb remedial 15N urea, promoted the growth and development of wheat plants under low-temperature stress, resulting in higher leaf SPAD readings, more new tillers, as well as increased dry weight of roots and above-ground organs. This study suggested that remedial nitrogen should be applied prior to low-temperature stress because it is more effective in restoring the growth of wheat plants under low-temperature stress.

Comparative effects of partial conservation farming practices on plant development and yield

Sustainable farming systems are being introduced to ensure optimum agricultural productivity despite climate change and environmental degradation. One such sustainable agricultural technology is conservation farming (CF). The uptake of this technology has remained low at about 5% years after its introduction. CF has five interrelated practices but for a variety of reasons, farmers are unable or unwilling to adopt all recommended practices. This study studied the agronomic effects of incomplete or partial conservation practice whereby not all the five practices are used, mimicking actual practices adopted by farmers. A split- plot design experiment involving partial or incomplete CF mainly use of basins, ripping were compared to conventional farming of normal ploughing (as main plots) and three crops - cowpea, millet and sorghum (split plot) was conducted. The objective was to determine the agronomic effects and efficacy of partial adoption of CF compared to conventional farming system. Data were collected on vegetative and reproductive parameters including, plant height, germination percentage, canopy density, number of leaves, number of branches/tillers/stems, SPAD (Soil Plant Analysis Development) readings a proxy for leaf chlorophyll content. Plants grown in basins had higher plant development (plant height, total biomass) and higher yields compared to those on conventional methods. This effect could be explained by better soil physical and chemical conditions in the basins as indicated by higher SPAD readings. Int. J. Agril. Res. Innov. Tech. 12(1): 115-119, June 2022

Determination of the Effect of Different Nitrogen Doses on the Yield, Yield Components and Chlorophyll Contents of Bread Wheat (Triticum aestivum L.) Cultivars using Artificial Neural Network

This research investigates an artificial neural network for predicting the chlorophyll concentration index and the effect of different nitrogen doses on the yield, yield components of Bread Wheat (Triticum aestivum L.). Plants were fertilized with 5, 10, 15, 20, and 25 kg da-1 nitrogen doses. The chlorophyll concentration index of each leaf was measured using a SPAD meter. The coefficient of determination values was found to be 0.99. In artificial neural network modeling, chlorophyll concentration values were estimated with SPAD readings. Artificial neural network modeling successfully described the relationship between actual chlorophyll concentration index values and predicted chlorophyll concentration index values. Agronomic parameters plant height (110.66-92.73 cm), the number of spikes per square meter (461.01-355.50), the number of seeds per spike (43.88-23.83), the weight of seed per spike (2.07-0.91 g), hectoliter weight, thousand-grain weight (43.10-35.89 g), grain yield (638.76-343.06 kg.da-1), protein contents (11.16-8.34 %), the value of sedimentation (19.40-11.94) were found statistically important.

Precision Nitrogen Management in Wheat at Rampur, Chitwan, Nepal

The application of blanket recommendation of nitrogen fertilizer leads to over or under fertilization. There is need to synchronize the N fertilizer application with plant demand. Field experiment was conducted during 2019 -2020 in Chitwan to assess the yield, nitrogen use efficiencies and economics of wheat production under precision N management compared with fixed time N management. Experiment was laid out in split plot design with sixteen treatments and three replications. The main plot treatments were varieties Vijay and Banganga and subplot treatments were three SPAD readings (≤35, ≤40, ≤45), two LCC readings (≤4, ≤5), Nutrient expert tool, fixed time nitrogen management(FTNM) with national recommended dose and control (zero N). The research result showed that varieties did not differ in yield and economics. Precision nitrogen management with SPAD≤45 and LCC≤5 consumed higher nitrogen doses and produced better yield attributes and yield (5585 and 5385 kgha-1 respectively) compared with FTNM. The agronomic use efficiency of nitrogen (AEN), recovery efficiency (REN), partial factor productivity (PFP were highest at LCC≤4 which consumed less nitrogen. SPAD≤35, LCC≤4 and NE treatments saved 15, 35 and 20 kgha-1 N respectively without compromising the yield obtained in FTNM. But, the benefit: cost ratio was highest at LCC≤5.Therefore, in terms of yield and profitability of wheat production, LCC≤5 is better than other treatments. The present national recommended dose of nitrogen to wheat crop is insufficient to achieve higher yield in Chitwan condition.

Efficient Herbicide Delivery through a Conjugate Gel Formulation for the Mortality of Broad Leaf Weeds.

Carfentrazone-ethyl is embedded in guar gum to prepare a polymer–herbicide conjugate gel formulation for a sustained release of the active ingredient (a.i.). The sprayable gel formulation was optimized at 0.5% (w/v) concentration. Strong interactions of the prepared composition of the polymer–herbicide conjugate system are shown through spectroscopic techniques, depicting the peak broadening of hydrophilic −OH bonds in the herbicide at 1743 cm–1, shifting to 1730 cm–1 in the polymer–herbicide sample. There is a broadening and shifting of the peak at 329 nm for the n → π* transition at 335 nm in the polymer–herbicide conjugate system in UV spectra. Differential scanning calorimetric measurements show a lowering of endothermic melting peaks to 242 and 303 °C in the polymer–herbicide conjugate. X-ray diffraction studies showed a sharp diffraction peak of the pure polymer at a 2θ of ∼20.3°, while broadening and shifting of the peak position to a 2θ of ∼20.8° were observed after adding the herbicide. Diffusion of the active ingredient in the polymer–herbicide conjugate resulted in much greater coverage (most of the weed leaf stomata (>95%)) than conventional spraying. The efficacy of both the polymer–herbicide formulation and herbicide at different doses in weed nurseries showed significantly higher weed mortality in Anagallis arvensis (95.4%), Chenopodium album (∼97%), and Ageratum conyzoides (93.16%) treated with the polymer–herbicide formulation @ 20 g a.i. ha–1. Narrow SPAD readings range of A. arvensis (0.1–30.6) and that of C. album (0–5) were observed in the polymer–herbicide formulation @ 20 g a.i. ha–1 was at par with the conventional formulation @ 30 g a.i. ha–1. Less regeneration in a weed nursery of A. arvensis (27%), C. album (77%), and A. conyzoides (49%) treated with gel formulations @ 20 g a.i. ha–1 was observed, which was significantly lower than those in conventional herbicides.

Nitrogen and potassium application effects on productivity, profitability and nutrient use efficiency of irrigated wheat (Triticum aestivum L.).

The development of robust nutrient management strategies have played a crucial role in improving crop productivity, profitability and nutrient use efficiency. Therefore, the implementation of efficient nutrient management stratigies is important for food security and environmental safety. Amongst the essential plant nutrients, managing nitrogen (N) and potassium (K) in wheat (Triticum aestivum L.) based production systems is citically important to maximize profitable production with minimal negative environmental impacts. We investigated the effects of different fertilizer-N (viz. 0–240 kg N ha-1; N0-N240) and fertilizer-K (viz. 0–90 kg K ha-1; K0-K90) application rates on wheat productivity, nutrient (N and K) use efficiency viz. partial factor productivity (PFPN/K), agronomic efficiency (AEN/K), physiological efficiency (PEN/K), reciprocal internal use efficiency (RIUEN/K), and profitability in terms of benefit-cost (B-C) ratio, gross returns above fertilizer cost (GRAFC) and the returns on investment (ROI) on fertilizer application. These results revealed that wheat productivity, plant growth and yield attributes, nutrients uptake and use efficiency increased significantly (p<0.05)with fertilizer-N application, although the interaction effect of N x K application was statistically non-significant (p<0.05). Fertilizer-N application at 120 kg N ha-1 (N120) increased the number of effective tillers (8.7%), grain yield (17.3%), straw yield (15.1%), total N uptake (25.1%) and total K uptake (16.1%) than the N80. Fertilizer-N application significantly increased the SPAD reading by ~4.2–10.6% with fertilizer-N application (N80-N240), compared with N0. The PFPN and PFPK increased significantly with fertilizer-N and K application in wheat. The AEN varied between 12.3 and 22.2 kg kg-1 with significantly higher value of 20.8 kg kg-1 in N120. Fertilizer-N application at higher rate (N160) significantly decreased the AEN by ~16.3% over N120. The N120treatment increased the AEK by ~52.6% than N80 treatment. Similarly the RIUEN varied between 10.6 and 25.6 kg Mg-1 grain yield, and increased significantly by ~80.2% with N120 as compared to N0 treatment. The RIUEK varied between 109 and 15.1 kg Mg-1 grain yield, and was significantly higher in N120 treatment. The significant increase in mean gross returns (MGRs) by ~17.3% and mean net returns (MNRs) by ~24.1% increased the B-C ratio by ~15.1% with N120 than the N80 treatment. Fertilizer-N application in N120 treatment increased the economic efficiency of wheat by ~24.1% and GRAFC by ~16.9%. Grain yield was significantly correlated with total N uptake (r = 0.932**, p<0.01), K uptake (r = 0.851**), SPAD value (r = 0.945**), green seeker reading (r = 0.956**), and the RIUEN (r = 0.910**). The artificial neural networks (ANNs) showed highly satisfactory performance in training and simulation of testing data-set on wheat grain yield. The calculated mean absolute error (MAE), mean absolute percentage error (MAPE) and root mean square error (RMSE) for wheat were 0.0087, 0.834 and 0.052, respectively. The well trained ANNs model was capable of producing consistency for the training and testing correlation (R2 = 0.994**, p<0.01) between the predicted and actual values of wheat grain yield, which implies that ANN model succeeded in wheat grain yield prediction.

How the Nitrogen Economy of a Perennial Cereal-Legume Intercrop Affects Productivity: Can Synchrony Be Achieved?

The UN's Sustainable Development goal of Zero Hunger encompasses a holistic set of targets that range from ending hunger by 2030, to increasing environmental sustainability and resilience of food production. Securing and managing soil nutrients remains one of the most basic challenges to growing adequate food while simultaneously protecting biodiversity and the integrity of ecosystems. To achieve these objectives, it is increasingly clear that the management of ecological processes will need to supplant reliance on non-renewable and environmentally damaging inputs. In recent years, progress has been made in developing perennial grain crops that show promise to improve on a range of ecological functions such as efficient nitrogen cycling and soil carbon accretion that tend to be well-developed in natural ecosystems but become compromised following land conversion to row crop agriculture. Here we report on a multi-faceted, 5-year experiment in which intermediate wheatgrass (IWG) (Thinopyrum intermedium), a perennial relative of wheat that is bred to produce the grain Kernza®, was intercropped in alternating rows with the perennial legume alfalfa (Medicago sativa). The performance of the unfertilized intercrop was compared to monocropped IWG treatments, with and without urea-N applications, planted at two row densities such that the intercrop could be interpreted as either an addition or substitution design. Comparisons of relative IWG yields (RYs) in the intercrop with unfertilized monocrops suggest net competitive interactions between alfalfa and IWG in the establishment year, followed by increasing degrees of facilitation over the next 4 years. Evidence from N fertilizer responsiveness, SPAD readings, net N mineralization assays, and N balance calculations suggest that alfalfa contributed to an aggrading pool of soil organic nitrogen over the course of the experiment. Comparisons of grain RYs of intercropped IWG and fertilized IWG monocultures suggest N-limitation in the first half of the experiment, and N sufficiency in the second half. Grain yields in the intercrop did not decline significantly over 5 years in contrast to all IWG monocrop treatments that did significantly decline. This study contributes to a growing literature on approaches to ecological nutrient management that incorporate diversity and perenniality to increase food security and resilience.

Chlorophyll meter based precision nitrogen management in spring maize

Site-specific fertilizer nitrogen (N) management using chlorophyll meter (SPAD meter) can help drawing in-season need-based N topdressing decisions. However, SPAD meter based threshold chlorophyll value to trigger supplement N in spring maize is indistinct. Field studies were conducted for two years in sub-tropical and sub-humid climate to study variations in spectral properties and to establish threshold SPAD value for need-based N management in spring maize cultivars. Results specified that N concentration of topmost fully expanded leaf was closely correlated with SPAD meter readings from six-leaf stage (V6) to tasseling stages (VT). The Cate-Nelson plot expressed SPAD 50 as the threshold value to determine plant N need at different growth stages. Need-based topdressings of 30 kg N ha−1, whenever SPAD reading fell below the threshold 50 improved grain yield production by 7.6 to 10.2 per cent over soil test-based N application. SPAD threshold 45 guided N management was inadequate to meet plant N demand, whereas SPAD threshold 55 guided N application lead to N doses in excess of crop requirement without yield benefits. SPAD threshold 50 guided N management ensured better demand-supply synchrony throughout the growth stages and thus reported better N recovery and agronomic efficiencies over soil test-based N management.

Flowering and Non-Flowering Spur Leaf Characteristics of 'Amasya' Apple and Its Comparison with Other Cultivars

Understanding the attributes of spur leaves in apple trees is essential to gain more insight into the complex process of fruit development and quality. However, limited literature is available about the spur leaf characteristics of the 'Amasya' apple cultivar. In this work, the Soil Plant Analysis Development (SPAD) and leaf area were investigated in flowering and non-flowering spur leaves of 'Amasya' and six common apple cultivars. Significant differences among cultivars were observed for the SPAD and spur leaf area. The median SPAD readings in 'Amasya' were 32.63 and 26.23 for the flowering and non-flowering spurs, respectively, which were the relatively low values among studied cultivars. The maximum SPAD value was measured in flowering spurs of 'Cripps Pink' (45.03). SPAD values were found to be lower in non-flowering spurs compared with flowering ones for all the studied cultivars, which confirms that decline in chlorophyll content coincided with a gradual decline in productivity. A notably significantly lower spur leaf area was found in 'Amasya', whereas the highest spur leaf area was in 'Cripps Pink'. However, no statistical difference was observed between flowering and non-flowering spur leaf areas within the same cultivars. The present results provided a general framework of SPAD and spur leaf areas in 'Amasya' and other apple cultivars when spurs had flowers or not. Knowledge of these characteristics provides a basis for building a model related to yield elaboration of apple trees.

Chlorophyll measurements in Alstroemeria sp. using SPAD-502 meterand the color space CIE L*a*b*, and its validation in foliar senescence

Our research aimed to study the correlation between the SPAD-502 readings and the color space CIE L*a*b* values in two cultivars of Alstroemeria sp. during leaf senescence and to evaluate the statistical criteria used in the selection of the best fit calibration functions. We demonstrate the importance of the Akaike information criterion and the parsimonious function besides the coefficient of determination. The reliability of the functions was tested by Student's t-test comparison between the chlorophyll (Chl) estimated from SPAD readings and their chemical concentrations. Polynomial and Hoerl function described well the changes in Chl a and total Chl (a+b) during senescence, but calibration functions are required to perform for each cultivar. We demonstrated that CIE L*a*b* system is reliable to estimate SPAD reading at stages of leaf senescence of Alstroemeria sp. and can be used instead of SPAD-502.

Nutrient Contents and Productivity of Triticum aestivum Plants Grown in Clay Loam Soil Depending on Humic Substances and Varieties and Their Interactions

Due to an extreme increase in population growth, Egypt suffers from a widening gap in the quantity of imported wheat compared with production and local consumption. Two field trials were conducted during the 2018/2019 and 2019/2020 seasons with three levels of humic substances (HSs) as a foliar spray (1.0, 2.0 and 4.0 g L−1; HS1, HS2 and HS3) and three levels (5.04, 7.56 and 10.08 kg ha−1; HS4, HS5 and HS6) as a soil application. These were applied three times (30, 45 and 60 days after sowing) in comparison with the control (HS0) to evaluate the performance of three wheat varieties (Seds1 (V1), Misr2 (V2) and Giza168 (V3)) grown in clay loam soil. The experiment was set up according to the split-plot structure in a randomized complete block design; however, the varieties were set as the main plot and treatments were a sub-main plot. Generally, the data indicated that the soil application treatments recorded maximum values for most growth and yield attributes, except for spike length and grain weight per spike, SPAD reading and total grain yield in the first season, and leaf area and biological yield in the second season. HS1, HS2, HS5, and HS6 were the superior treatments for most of the nutrient contents studied. Regarding the influence of variety, the results showed that V3 recorded maximum values for LA, SpL, TGW, TGY and leaf Zn and Cu contents in both seasons; PH, GWS and leaf N content in the first season; and SPAD reading, BY and leaf K, Fe and Mn contents in the second season. V1 was the superior variety for GWS, BY, leaf K and Mn contents in the 2018/2019 season and PH, GNS in the second season, followed by V2, which had the greatest values for leaf P contents in both seasons, and SPAD reading, GNS and leaf Fe content in the 2018/2019 season and GWS and leaf N content in the second season.

Morphological, agronomical, physiological and molecular characterization of a high sugar mutant of sugarcane in comparison to mother variety.

Sugarcane is a significant crop plant with the capability of accumulating higher amount of sucrose. In the present study, a high sucrose content sugarcane mutant clone, GXB9, has been studied in comparison to the low sucrose mother clone B9 on morphological, agronomical and physiological level in order to scrutinize the variation because of mutation in GXB9 in field under normal environmental condition. The results showed that GXB9 has less germination, tillering rate, stalk height, leaf length, leaf width, leaf area, number of internodes, internode length and internode diameter than B9. Qualitative traits of leaf and stalk displayed significant variation between GXB9 and B9. Endogenous hormones quantity was also showed variation between the two clones. The relative SPAD reading and chlorophyll a, b concentrations also showed variation between GXB9 and B9. The photosynthetic parameter analysis indicated that the GXB9 has significantly higher net photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr) than B9. The qRT-PCR analysis of genes encoding enzymes like SPS, SuSy, CWIN, and CeS showed upregulation in GXB9 and downregulation in B9. However, these genes were significantly differentially expressed between the immature and maturing internodes of GXB9. The cane quality trait analysis showed that GXB9 had higher juice rate, juice gravity purity, brix, juice sucrose content and cane sucrose content than B9. The yield and component investigation results indicated that GXB9 had lower single stalk weight, however higher number of millable stalks per hectare than B9, and GXB9 had lower theoretical cane yield than B9. SSR marker analysis showed genetic variation between GXB9 and B9. This study has shown significant variation in the traits of GXB9 in comparison to B9 which advocates that GXB9 is a high sugar mutant clone of B9 and an elite source for future breeding.

Evaluating the Waterlogging Tolerance of Wheat Cultivars during the Early Growth Stage Using the Comprehensive Evaluation Value and Digital Image Analysis

The accurate and efficient screening of waterlogging-tolerant cultivars is an effective way to mitigate waterlogging damages. An experiment was conducted to evaluate the performance of 28 wheat varieties mainly planted in the middle and lower reaches of the Yangtze River, China, under control and waterlogging conditions. When the 15-day waterlogging that was initiated at the third-leaf stage was completed, the aboveground dry weight, plant height, leaf number on main stem, culm number, leaf area, and SPAD readings of wheat seedlings were significantly decreased by 14%, 11%, 6%, 13%, 14%, and 15% compared with the control treatment (maintaining approximately 80% of field capacity), respectively. The results showed that the percentage reductions in the dry weight and leaf area under stress accurately represented the influence of the majority of the measured agronomic traits and were significantly negatively correlated with the respective dry weight and leaf area of different cultivars under waterlogging. This suggests that dry weight and leaf area can be used as agronomic traits for screening waterlogging-tolerant cultivars. The comprehensive evaluation value of waterlogging tolerance (CEVW) was closely related to the percentage reduction in dry weight, plant height, culm number, leaf area, and SPAD reading. The range of CEVW was 0.187–0.819, indicating a wide variation in the waterlogging tolerance of the wheat cultivars. Comparing the top-view images, the phenotypic texture parameters (dissimilarity, homogeneity, and angular second moment (ASM)) extracted from the side-view images better reflected the dry weight, plant height, and leaf area under different water treatments. The percentage reduction in ASM had the strongest correlation with CEVW (root mean square error = 0.109); thus, the ASM is recommended as a suitable phenotypic parameter to evaluate waterlogging tolerance. The present results provide references for the rapid and intelligent screening of waterlogging-tolerant wheat cultivars, but future studies need to consider the stress evaluation of the adult plants.

Agronomical and Physiological Responses of Faba Bean Genotypes to Salt Stress

Considering the importance of salinity stress and genotype screening under stress conditions, the current study evaluated faba bean genotypes in response to saline stress and identified those that were tolerant and determined the influential ratio of each yield component on seed yield under both conditions. As a result, 12 faba bean genotypes were tested under 2 levels of salt stress (100 mM and 200 mM) and a control. The study was analyzed with multivariate (descriptive, ANOVA, PCA, biplot, cluster analysis, and indices) analysis techniques to determine the tolerance level of each genotype. Similarly, the cluster analysis results reported that faba bean genotypes were divided into two groups under the control and 100 mM salinity levels; however, the 200 mM salinity level recorded three groups of faba bean genotypes, showing that salinity stress may limit phenotypic variability among faba bean genotypes. The descriptive analysis results showed a wide range of diversity among the studied characteristics under control and salinity stress conditions. The number of seeds/plants recorded a significant association with plant height (cm) (PH), stomatal conductance (SC), days to flowering (DF), the number of pods, and seed weight (g) (SW); however, an insignificant association was recorded with leaf temperature (LT), fresh weight (g) (FW), Na+, K+, and Na/K ratio. The first three principal components (PCs) represent 81.45% of the variance among the studied traits. The most significant characteristics that contributed the most to the diversity were (PH, leaf area, SPAD reading, stomatal conductance, DF, number of pods/plants, number of seeds/pods, SW, K, and total chlorophyll content); however, the significant genotypes (Hassawi-2, Sakha, ILB-4347, Misr-3, FLIP12501FB) were present in PC1 under both conditions. The results predicted that Hassawi-2, ILB-4347, Sakha, Misr-3, and Flip12501FB were the significant (tolerant) genotypes. However, FLIP12504FB represents a sensitive genotype based on its final grain yield. The results of the indices also recorded significant index correlations with grain yield, demonstrating that these indices are effective tools for screening faba bean-tolerant genotypes under salinity stress conditions.

Effects of nitrogen application rates on the spatio-temporal variation of leaf SPAD readings on the maize canopy

AbstractThe spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soil-plant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea maysL.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent.SPADmaxat each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.