Relative Chlorophyll Meter Research Articles

Evaluation of soil bacteria treatments on some physiological parameters of crops by spectral vegetation indices

The effects of soil bacteria treatments on barley and wheat (1. treatment: stubble decomposers + soil inoculators; 2. stubble decomposers + soil regenerators; 3. control) were studied at the Agricultural Research Institute in Kompolt on spectral vegetation indices which are closely related to photochemical processes and photosynthetic pigments in barley and wheat leaves. We applied in vivo field measurements: SPAD 502 relative chlorophyll meter and ASD Field Spec Pro 3 spectroradiometer. This work presents the results of the experiments in 2019, moreover, we compared them with our previously published investigations on several other crops (maize, sunflower, rape, barley) carried out in 2017 and 2018. In 2019 despite the significant level of the standard deviation of data in field conditions, treated (mainly with stubble decomposers + soil inoculators) wheat leaves could be characterized by significantly higher chlorophyll and water content, higher photochemical efficiency, and lower carotenoid content. In the case of barley due to the large standard deviation of data, we couldn’t reveal the beneficial effects of treatments by these methods. Due to the very rainy spring in 2019 some experimental plots - like K9 with barley – wre covered by inland water, which negatively influenced living conditions of soil bacteria. Despite this unfavourable conditions, the first treatment resulted in an 18.9% higher yield of barley and 27.8% higher yield of wheat, while the second treatment increased barley yield with 28.9% and wheat yield with 27.7%. In the case of wheat, spectral vegetation indices could indicate beneficial effects of soil bacteria treatments at the beginning of flowering, similarly to our results in 2017 and 2018 in case of maize, sunflower, rape, and barley.

Predicting Nitrogen Losses in Potato Crop with Soil Nitrogen and Plant Tests

There is a lack of information on how to determine N‐use efficiency and monitoring and diagnosing N losses in irrigated potato (Solanum tuberosum L.) production. This study was conducted to determine and validate a simple model to estimate inorganic N leaching losses (Nlosses) from gravitational water and to determine Nlosses thresholds using the soil N and canopy sensor tests. We conducted field experiments (n = 6) from 2008 to 2012 to evaluate the effects of N rates and/or managements and gravitational water on tuber yield, crop N uptake (Nuptake) and Nlosses on the cultivar Innovator in the Argentinean Pampas. The N nutrition index (NNI), normalized chlorophyll meter reading (NNI‐CM), relative chlorophyll meter reading (CMr), and relative normalized difference vegetative index (NDVIr) were determined 70 d after planting. Tuber yield, residual N, and Nlosses varied from 40.8 to 70.3 t ha−1, 23.2 to 78.7 kg N ha−1 and 6.4 to 219.4 kg N ha−1, respectively. The Nlosses were directly associated with the amount of gravitational water in the soil profile (r2 = 0.79). Threshold values of 255 kg N ha−1 for N available, 1.0 for NNI, 1.03 for NNI‐CM, 0.94 for CMr and 0.98 for NDVIr were defined. We determined linear increases in Nlosses above these thresholds (r2 = 0.75, 0.35, 0.53, 0.40, and 0.46, respectively). High N rates and gravitational water increased the N losses in potato crops under irrigation. This information could be useful to adjust N fertilizer recommendation and monitoring the Nlosses in potato crops under irrigation.Core Ideas Information on how to monitor and diagnose N losses in irrigated potato production is lacking. This study estimates N losses from gravitational water, soil N, and canopy sensor tests. The aim is to predict N‐loss thresholds using soil N and canopy sensor tests. N losses were directly associated with the amount of gravitational water in the soil profile.

GROUND-BASED REMOTE SENSING FOR ESTIMATING THE CUMULATIVE EFFECT OF DIFFERENT IRRIGATION WATER QUALITIES ON THE PRODUCTIVITY AND GROWTH OF POTATO

The growing competition of water available from Nile fresh water, coupled with laws limiting ground water pumping, has led to utilization of different water qualities in irrigation proposals. In this study, the effect of mixed water on yield, biomass and relative chlorophyll meter was estimated. The performance of ground-based remote sensing of hyperspectral passive reflectance sensor and digital image analysis as precision agriculture tools was tested at tubers bulking growth stage to assess their relationship to detractively measured parameters via simple linear regression and three models based on partial least square regression (PLSR) analysis. The results showed that the newly developed indices (R970 - R730)/(R970 + R730) and (R990 - R730)/(R990 + R730) showed close and highly significant associations with yield, biomass and relative chlorophyll meter, with R2 values reach to 0.87, 0.80, and 0.86, respectively, while the green cover (%) was highly significantly related the same parameters, with R2 values reach to of 0.82, 0.73 and 0.70, respectively. Three models of PLSR based on (i) the spectral reflectance from 302 to 1148 nm, (ii) selected nine spectral indices and (iii) selected eight red–blue–green (RBG) indices of the images analysis for the measured parameters were apparently useful for estimating the yield, aerial biomass and relative chlorophyll meter of potato cultivar under fresh and mixed water treatments. In conclusion, the assessment of measured parameters was improved and more robust when using the multivariate analysis of PLSR models than with previously assayed normalized difference spectral indices and RGB indices from digital image analysis.

Iron Chelates Alleviate Iron Chlorosis in Soybean on High pH Soils

High pH soils frequently lead to iron deficiency chlorosis (IDC) in soybean [Glycine max (L.) Merr.]. As a result, yields for soybean are often reduced. Studies in the north‐central United States have shown improvements in grain yield after applying Fe chelates on calcareous soils, but this practice has not been evaluated in a southern climate. Two sites within the Blackbelt region of Alabama were evaluated for response to Fe‐EDDHA, Fe‐Citrate, and FeSO4 for their effect on yield and chlorosis in 2010, 2011, and 2012. Treatments were applied in‐furrow at planting, as a foliar spray at the V3 growth stage, or as a split‐application. Remote sensing, relative chlorophyll meter readings, and visual chlorosis scores (VCS) were assessed as methods for identifying degree of Fe chlorosis. At the location where IDC was most pronounced, all treatments of Fe‐EDDHA were effective at reducing VCS ratings when applied in‐furrow at planting; however, chlorosis evaluation through remote sensing and relative chlorophyll readings was not able to detect improvements in chlorosis measured with VCS. Treatments of Fe‐EDDHA at 4.5 kg product ha−1 increased yield whether applied as an in‐furrow at planting treatment or as a split application at planting and at V3 growth stage as a foliar spray. Treatments of Fe‐Citrate and FeSO4 did not improve yield as applied in this study. Results suggest that Fe‐EDDHA can be used in southern climates as a strategy to overcome IDC yield limitations.

Liquid Swine Manure Application to Soybean and Residual-Year Nitrogen Supply to Corn

Liquid swine (Sus scrofa domesticus) manure (LSM) is a valuable source of plant nutrients; however, information on application to soybean [Glycine max (L.) Merr.] and subsequent potential N response in residual-year corn (Zea mays L.) is lacking. Replicated on-farm trials were conducted at eight sites from 2000 to 2003 in Iowa with control, low, and high LSM application rates applied to soybean. In the following year corn, four fertilizer N (FN) rates were applied within each prior-year LSM rate. Soybean grain yield (GY) increased at 63% of sites with LSM application (mean 0.17 Mg ha−1), with no soybean GY reductions. Postsoybean harvest soil profile NO3–N increased at four sites, with mean increases across sites of 12 and 24 kg NO3–N ha−1 for the low and high LSM rates, respectively. Residual-year corn GY increased at 71% of sites from the prior-year low and high LSM rates (mean 0.6 and 1.1 Mg ha−1) that received no FN. The residual-year N supply to corn was estimated at 11% of the total LSM-N applied to soybean, the amount of postsoybean harvest profile NO3–N ha−1 increase from each LSM rate. Corn leaf relative chlorophyll meter (RCM) and end of season corn stalk NO3–N (CSNT) reflected the residual N supply, but the late spring nitrate test (LSNT) did not detect that residual N. Application of LSM to soybean can be a viable nutrient management practice; however, total-N application should be at a rate to minimize excessive residual NO3–N and carryover to future crops.

On‐Farm Evaluation of Liquid Swine Manure as a Nitrogen Source for Corn Production

Liquid swine (Sus scrofa) manure (LSM) is a substantial crop nutrient resource in Iowa. An on‐farm study was conducted in 2000–2003 at 16 sites to evaluate corn (Zea mays L.) response to LSM N. Replicated field‐length strips were a control and two LSM rates, fall or spring applied, and four fertilizer N (FN) rates applied after planting in subplots. Average corn grain yield (GY) in the strips was 7.8, 9.6, and 10.4 Mg ha−1 for the control, low, and high LSM rates, respectively. Plant and soil tests also increased with LSM application, indicating corn response. With the low LSM rate, GY increased with FN at many sites, but less frequent and smaller increase with the high LSM rate. Despite the average 82% fraction of LSM total‐N as NH4–N, FN equivalence based on GY was only 61 to 64%. This indicates potential N losses, not unexpected due to application time and large springtime precipitation at some sites. Critical values for the late spring soil NO3–N (LSNT) and lower corn stalk NO3–N (CSNT) were 27 and 1820 mg NO3–N kg−1, respectively; and the tests consistently indicated excess N but had poor relationship to N response at low values. Relative chlorophyll meter (RCM) values did not differentiate excess to slight N deficiency. The LSM was able to supply N for corn production, but like fertilizer, must be managed carefully. If additional N may be needed to achieve optimal yield, application must be based on well‐calibrated soil or plant tests.

Relationship between soil nitrate accumulation and in-season corn N nutrition indicators

Ziadi, N., Bélanger, G. and Claessens, A. 2012. Relationship between soil nitrate accumulation and in-season corn N nutrition indicators. Can. J. Plant Sci. 92: 331–339. Nitrogen management tools are required to optimize crop growth and yield while minimizing the likelihood of N losses to the environment. We previously determined that non-limiting N conditions for near maximum corn (Zea mays L.) grain yield are reached with the following threshold values for three in-season plant-based indicators of corn N nutrition determined at approximately the V12 stage of development: N nutrition index (NNI) = 0.88, leaf N (NL) concentration = 32.7 mg N g−1 leaf DM, and relative chlorophyll meter (RCM) values = 0.95. Our objective was to study the relationship between these plant-based indicators and soil NO3-N content in an effort to develop tools to reduce the likelihood of soil NO3-N accumulation without affecting grain yield. This study at 5 site-years in Québec consisted of six N fertilizer rates (20–250 kg N ha−1). The NNI, NL concentrations, RCM values, and soil (0–0.15 m) NO3-N content were measured weekly from July to early August, while soil NO3-N content to a 0.90-m depth was measured in late August and October. During the growing season from July to early August, the proportion of data points above the average soil NO3-N content was greater under non-limiting N conditions (NNI ≥ 0.88, NL concentrations ≥ 32.7 mg N g−1 leaf DM, or RCM values ≥ 0.95) than under limiting N conditions. Furthermore, the mean soil NO3-N content of the data points above the general average was much higher under non limiting than limiting N conditions in late August (167 vs. 78 kg NO3-N ha−1 for NNI and RCM; 166 vs. 112 kg NO3-N ha−1 for NL concentration) and October (68 vs. 49 kg NO3-N ha−1). High soil NO3-N accumulation during the season and at harvest occurs only when in-season plant-based N indicators are greater than their threshold values.

Relationship between soil nitrate accumulation and in-season corn N nutrition indicators

Ziadi, N., Belanger, G. and Claessens, A. 2012. Relationship between soil nitrate accumulation and in-season corn N nutrition indicators. Can. J. Plant Sci. 92: 331-339. Nitrogen management tools are required to optimize crop growth and yield while minimizing the likelihood of N losses to the environment. We previously determined that non-limiting N conditions for near maximum corn (Zea mays L.) grain yield are reached with the following threshold values for three in-season plant-based indicators of corn N nutrition determined at approximately the V12 stage of development: N nutrition index (NNI)=0.88, leaf N (NL) concentration =32.7 mg N g-1 leaf DM, and relative chlorophyll meter (RCM) values =0.95. Our objective was to study the relationship between these plant-based indicators and soil NO3-N content in an effort to develop tools to reduce the likelihood of soil NO3-N accumulation without affecting grain yield. This study at 5 site-years in Quebec consisted of six N fertilizer rates (20-250 kg N ha-1)....

Plant‐Based Diagnostic Tools for Evaluating Wheat Nitrogen Status

The nitrogen nutrition index (NNI), based on critical plant N dilution curves, was developed to determine the in‐season N status of many species including wheat (Triticum aestivum L.). We assessed the relationship between wheat NNI and two simpler diagnostic tools; namely, leaf nitrogen (NL) concentration and chlorophyll meter (CM) readings. The study was conducted at six site‐years (2004−2006) in Québec, Canada, using four to eight N fertilizer rates (0−200 kg N ha−1). Leaf N concentrations and CM readings were determined from the uppermost collared leaf during the growing season along with NNI determinations. Generally, NNI, NL concentrations, and CM readings increased with increasing N rates. Leaf N concentrations and CM readings were significantly related to NNI during the growing season. Normalization of the CM values, relative to high N plots (relative chlorophyll meter [RCM] readings), improved the relationship with NNI by reducing site‐year differences. However, variation among sampling dates was observed in all relationships. By restricting the sampling dates to essentially the elongation stage, the relationship between NNI and NL (NNI = −0.43 + 0.035 NL; R2 = 0.52), CM (NNI = −0.64 + 0.039 CM; R2 = 0.68), or RCM (NNI = −1.31 + 2.45 RCM; R2 = 0.82) was generally improved. Nitrogen concentration, CM reading, or RCM reading of the uppermost collared leaf, preferably at the elongation stage, can therefore be used to assess the nutritional status of spring wheat.

Chlorophyll Measurements and Nitrogen Nutrition Index for the Evaluation of Corn Nitrogen Status

Plant‐based diagnostic techniques are used to determine the level of crop N nutrition but there is limited comparative research on the different methods. Our objectives were to establish the relationship between chlorophyll meter (CM) readings and N nutrition index (NNI) during the corn (Zea mays L.) growing season, and to compare both methods as diagnostic tools for predicting grain yield response to N fertilization. The study was established at eight site‐years using four to seven N fertilization rates. The CM readings from the youngest collared leaf were taken on five to eight sampling dates in 2004, 2005, and 2006 along with NNI determinations. Generally, CM readings and NNI increased with increasing N rates. Chlorophyll meter readings and relative CM (RCM) readings were related to NNI, but the intercepts and/or slope of the response curves varied with site‐year. Because they are site‐specific, these relationships may not be reliable indicators of corn N status. The relationship between CM readings and relative grain yield (RY) at stage of development ≈V12 was also site‐specific. Relative CM readings (RY = −0.64 + 1.65 RCM if RCM ≤ 0.98 and RY = 0.97 if RCM > 0.98; R2 = 0.60) and NNI (RY = −0.34 + 1.47 NNI if NNI ≤ 0.88 and RY = 0.96 if NNI > 0.88; R2 = 0.79) at stage of development ≈V12 were related to RY. These two relationships were stable across site‐years and could be used to detect and quantify N deficiencies of corn.

Using Relative Chlorophyll Meter Values to Determine Nitrogen Application Rates for Corn

Determining specific N fertilization rates to achieve optimal return is difficult. Crop N stress sensing uses the plant as an indicator of N fertilization need and has potential to improve N management. However, for making N rate decisions, a calibrated relationship between measured N stress and optimum N rate is required. Corn (Zea mays L.) plant N stress was determined with a chlorophyll meter (CM) at 102 site‐years of N rate trials conducted from 1999–2005 with corn following soybean [Glycine max (L.) Merr.] (SC) and continuous corn (CC). Normalizing CM readings to relative chlorophyll meter (RCM) values reduced variation and improved the calibration of N stress with the nitrogen rate difference (ND) from the economic optimum nitrogen rate (EONR). With SC the adjusted R2 (adjR2) was 0.53 for CM readings and 0.73 for RCM values, and with CC the adjR2 was 0.57 for CM readings and 0.76 for RCM values. The same statistically significant (P < 0.001) relationship between RCM values and ND was found for both SC and CC, indicating RCM critical values of 0.97 and 0.98, respectively. This indicates the same calibration for N rate determination based on RCM values can be used for both rotations. Evaluation of RCM values at multiple corn growth stages indicated the same relationship to ND at the fifteenth leaf and silking growth stages, suggesting a period of time during mid‐to‐late vegetative growth to collect CM readings, and make in‐season N rate decisions and applications. The calibration of RCM values to the rate differential from optimum N can be used by producers to determine in‐season N applications for corn across varying production conditions.

Growth onset, senescence, and reproductive development of meadow species in mesocosms exposed to elevated O 3 and CO 2

We studied the effects of elevated O 3 (40–50 ppb) and CO 2 (+100 ppm) alone and in combination on the growth onset, relative chlorophyll meter values, and reproductive development of meadow species grown in ground-planted mesocosms using open-top chambers. The 3-year study was conducted in the summers of 2002–2004. Elevated O 3 decreased the early season coverage of plant communities and delayed the flowering of Campanula rotundifolia and Vicia cracca. The relative chlorophyll meter values of Fragaria vesca leaves were decreased by O 3. Ozone also reduced the overall number of produced flowers, but as far as individual species were concerned, O 3 had significant effects only on Campanula rotundifolia. In the case of Fragaria vesca, O 3 decreased the fresh weight of individual berries. The effects of CO 2 were less pronounced, and CO 2 generally did not ameliorate the negative effects of O 3. Changes in reproduction may affect the long-term fate of the whole community.