ESTABLISHMENT OF CRITICAL THRESHOLD VALUES OF CHLOROPHYLL METER TO GUIDE NITROGEN FERTILIZATION IN WHEAT

2020 ◽  
Vol 35 (1) ◽  
pp. 11-22
Keyword(s):  
Nitrogen Fertilization ◽  
Critical Threshold ◽  
Threshold Values ◽  
Chlorophyll Meter

Fertilization factor associated with nitrogen sufficiency index for nitrogen topdressing fertilization in common bean

2021 ◽  
Vol 51 ◽  
Author(s):  
Gustavo Henrique do Nascimento ◽  
Luciana Correa Moraes ◽  
Silvino Guimarães Moreira ◽  
Fábio Aurélio Dias Martins ◽  
Guilherme Vieira Pimentel
Keyword(s):  
Common Bean ◽  
Nitrogen Fertilization ◽  
Complex Dynamics ◽  
Block Design ◽  
Chlorophyll Meter

ABSTRACT The current recommendations for nitrogen (N) doses may not contemplate the complex dynamics of N in the soil, what may imply in insufficiency to the crop demand. This study aimed to evaluate the use of two portable chlorophyll meters (Minolta SPAD 502 and ClorofiLOG model CFL 1030), after defining the nitrogen sufficiency index (NSI), to estimate the nitrogen fertilization factor in modern bean genotypes. A block design was used, with four replications. Each experiment consisted of four treatments, with doses of 0, 5, 10 and 20 kg ha-1 of N for each 1 % considered below the NSI defined as adequate for each cultivar. At the end of the cycle, the production components and yield were evaluated. It was not possible to obtain precise adjustments in the methodology for the TAA Gol cultivar. The fertilization factor of 12.5 kg ha-1 of N for each 1 % below the NSI of 90 % proved to be efficient for the Pérola cultivar, when the SPAD-502 chlorophyll meter was used. In genotypes with size and cycle characteristics similar to those of the BRSMG Uai cultivar and the VR 20 strain, using a fertilization factor between 14 and 16 kg ha-1 of N, the NSI of 95 % must be reduced, in order to increase the efficiency of the nitrogen fertilization.

SEASONAL VARIATION AND THRESHOLD VALUES FOR CHLOROPHYLL METER READINGS ON LEAVES OF POTATO CULTIVARS

2010 ◽  
Vol 33 (14) ◽  
pp. 2148-2156 ◽  
Author(s):  
Camilo Busato ◽  
Paulo Cezar Rezende Fontes ◽  
Heder Braun ◽  
Paulo Roberto Cecon
Keyword(s):  
Seasonal Variation ◽  
Potato Cultivars ◽  
Threshold Values ◽  
Chlorophyll Meter

Effect of Liver Failure on the Cerebral Circulatory and Metabolic Responses to Hypoxia in the Goat

1976 ◽  
Vol 50 (1) ◽  
pp. 15-23
Author(s):  
N. N. Stanley ◽  
N. S. Cherniack
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Liver Failure ◽  
Venous Blood ◽  
Practical Importance ◽  
Critical Threshold ◽  
Threshold Values ◽  
Arterial O2 Saturation ◽  
O2 Delivery ◽  
The Brain

1. Six unanaesthetized goats were used to evaluate the effect of liver failure on the hypoxic responsiveness of cerebral blood flow. The animals breathed air and several different hypoxic gas mixtures enriched with sufficient CO2 to maintain an isocapnic state. The cerebral metabolic rate for O2 (CMRo2) was also measured in four of these goats. 2. In baseline studies there was a linear relationship between cerebral blood flow and arterial O2 saturation (Sa,o2) measured at different levels of isocapnic hypoxia. The slopes of the cerebral blood flow/Sa,o2 response lines were used to quantify the response of cerebral blood flow to hypoxia. In the healthy goat, CMRo2 was not depressed by hypoxia until the O2 tension (Po2) in arterial and cerebral venous blood had fallen below critical threshold values of approximately 3·2 and 2·2 kPa (24 and 16 mmHg) respectively. 3. Liver failure was accompanied by a fall in cerebral blood flow and CMRo2. There was also a depression in the response of cerebral blood flow to hypoxia and a disproportionate reduction of cerebral O2 delivery in hypoxia. CMRo2 was further reduced at arterial and cerebral venous Po2 values, which were much higher than the critical threshold values for producing hypoxic CMRo2 depression in health. 4. It is concluded that the brain becomes more vulnerable to the adverse effects of hypoxia during liver failure. This may be of practical importance in the management of patients with arterial hypoxaemia or other complications (e.g. anaemia or shock), which may reduce cerebral oxygen delivery.

When Is Controlling Cone and Seed Insects in Douglas-fir Seed Orchards Justified?

1983 ◽  
Vol 59 (6) ◽  
pp. 304-307 ◽  
Author(s):  
G. E. Miller
Keyword(s):  
Douglas Fir ◽  
Critical Threshold ◽  
Threshold Values ◽  
Insect Infestation ◽  
Seed Orchards ◽  
Crop Size ◽  
Benefit Cost Analysis ◽  
Cone And Seed Insects ◽  
Benefit Cost ◽  
Seed Insects

Data from operational applications of dimethoate at two Douglas-fir seed orchards in British Columbia were used as base-lines for a benefit: cost analysis of protection of seed from cone and seed insects. Applications were economically justifiable provided that cone crop size and increased seed yield are above critical threshold values for given seed values and application costs. Sampling techniques for estimating crop size and insect infestation levels and expected damage are requisites for efficient orchard management where crop size and infestation levels fluctuate.

scholarly journals Mombaça grass yield as a function of nitrogen fertilization based on the use of the chlorophyll meter

2021 ◽  
Vol 42 (6supl2) ◽  
pp. 4085-4102
Author(s):  
Lorrayne Lays Ferreira Leite ◽  
◽  
Clarice Backes ◽  
Leandro José Grava de Godoy ◽  
Alessandro José Marques Santos ◽  
...  
Keyword(s):  
Nitrogen Fertilization ◽  
Block Design ◽  
Management Strategies ◽  
N Fertilization ◽  
Control Treatment ◽  
Agronomic Efficiency ◽  
N Application ◽  
Chlorophyll Meter ◽  
Randomized Block Design ◽  
Tiller Density

The objective of this study was to evaluate the yield and agronomic efficiency of mombaça grass achieved with the management of nitrogen fertilization, based on the nitrogen sufficiency index (NSI) calculated using measurements obtained with a chlorophyll meter. The experiment was conducted in the field, in São Luís de Montes Belos - GO, Brazil, from November 2016 to May 2018, as a randomized-block design with six treatments and five replicates. Treatments consisted of six N fertilization management strategies (M), namely, M1 - reference, with 150 kg ha-1 N per application; M2 - recommended, with 50 kg ha-1 N per application; M3 - 50 kg ha-1 N when NSI < 98%; M4 - 50 kg ha-1 N when NSI < 94%; M5 - 50 kg ha-1 N when NSI < 90%; and M6 - control treatment, without N application. The NSI was monitored based on the relative chlorophyll content obtained with the chlorophyll meter. Forage canopy height, tiller density, and yield were evaluated. At the end of the 2nd cycle, the recommended, reference, NSI98%, NSI94%, and NSI90% treatments had received 1,050, 350, 300, 250, and 0 kg N ha-1. Control treatment obtained the lowest dry biomass yield, whereas the recommended, NSI98%, and NSI94% treatments showed the highest. Thus, N doses between 1,950 and 300 kg ha-1, in the second cycle, provided statistically equivalent yields in mombaça grass. Considering the DM of both evaluation cycles, the highest yield was achieved with the NSI98% and NSI94% treatments. The application of N doses of 250 to 1050 kg ha-1 provided similar yields. Therefore, the adoption of a nitrogen sufficiency index below 98% and 94% as a parameter allows a reduction and rational use of nitrogen fertilizer.

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