MODIFICATION OF THE HEAT UNIT FORMULA FOR PEAS

1962 ◽  
Vol 42 (1) ◽  
pp. 15-21 ◽  
Author(s):  
G. W. Hope
Keyword(s):  
Daily Maximum ◽  
Base Temperature ◽  
Heat Unit ◽  
Yearly Variation ◽  
Coefficients Of Variation ◽  
Maximum Temperatures ◽  
Unit Formula

The yearly variation in computed heat unit requirements of Perfection peas was reduced by modifying the method of deriving the units. Coefficients of variation of heat unit sums derived from daily means were lowest when daily maximum temperatures in excess of 60°F. were equated to 60° and when a base temperature of 36°F. was subtracted from the mean.Heat unit sums obtained from daily maxima were as homogeneous as those obtained from daily means.

scholarly journals Predicting Yield and Time to Maturity of Muskmelons from Weather and Crop Observations

1998 ◽  
Vol 123 (2) ◽  
pp. 195-201 ◽  
Author(s):  
Sylvie Jenni ◽  
Katrine A. Stewart ◽  
Gaétan Bourgeois ◽  
Daniel C. Cloutier
Keyword(s):  
Total Yield ◽  
Developmental Time ◽  
Daily Maximum ◽  
Base Temperature ◽  
Heat Unit ◽  
Data Set ◽  
Simple Method ◽  
Fruit Maturity ◽  
Richards Function ◽  
Maximum Temperatures

A simple method to predict time from anthesis of perfect flowers to fruit maturity (full slip) and yield is presented here for muskmelon (Cucumis melo L.) grown in a northern climate. Developmental time for individual muskmelons from anthesis to full slip could be predicted from several heat unit formulas, depending on the temperature data set used. When temperature at 7.5 cm above soil level was used, the heat unit formula resulting in the lowest coefficient of variation (cv=6.9%) accumulated daily average temperatures with a base temperature of 11 °C and an upper threshold of 25 °C. With temperatures recorded at a meteorological station located 2 km from the experimental field, the method showing the lowest cv (8.9%) accumulated daily maximum temperatures with a base temperature of 15 °C. This latter method was improved by including a 60-degree-day lag for second cycle fruit. The proportion of fruit volume at full slip of 22 fruit from the first cycle could be described by a common Richards function (R2=0.99). Although 65% of the plants produced two fruit cycles, fruit from the first cycle represented 72% of total yield in terms of number and mass. The blooming period of productive flowers lasted 34 days, each cycle overlapping and covering an equal period of 19 days. Counting the number of developing fruit >4 cm after 225 degree days from the start of anthesis (when 90% of the plants have at least one blooming perfect flower) could rapidly estimate the number of fruit that will reach maturity.

scholarly journals A Heat Unit Accumulation Method for Predicting Cucumber Harvest Date

1996 ◽  
Vol 6 (1) ◽  
pp. 27-30 ◽  
Author(s):  
Katharine B. Perry ◽  
Todd C. Wehner
Keyword(s):  
North Carolina ◽  
Production Systems ◽  
Planting Date ◽  
Harvest Date ◽  
Daily Maximum ◽  
Base Temperature ◽  
Harvest Dates ◽  
The Difference ◽  
Maximum Temperatures ◽  
Accumulation Method

The use of a previously developed model for predicting harvest date in cucumber production systems is described. In previous research we developed a new method using daily maximum temperatures in heat units to predict cucumber harvest dates. This method sums, from planting to harvest, the daily maximum minus a base temperature of 60F (15.5 C), but if the maximum is >90F (32C) it is replaced by 90F minus the difference between the maximum and 90F. This method was more accurate than counting days to harvest in predicting cucumber harvest in North Carolina, even when harvest was predicted using 5 years of experience for a particular location and planting date.

scholarly journals A Heat Unit Model to Predict Growth and Development of Muskmelon (Cucumis melo var. reticulatus Naud.) to Anthesis

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 790D-790
Author(s):  
S. Jenni ◽  
D.C. Cloutier ◽  
G. Bourgeois ◽  
K.A. Stewart
Keyword(s):  
Cucumis Melo ◽  
Dry Weight ◽  
Base Temperature ◽  
Degree Days ◽  
Heat Unit ◽  
Air Temperatures ◽  
Unit Model ◽  
Dependent Variables ◽  
Soil Temperatures ◽  
Unit Formula

Plant dry weight of muskmelon transplants to anthesis could be predicted from a multiple linear regression based on air and soil temperatures prevailing under 11 mulch and rowcover combinations. The two dependent variables of the regression model consisted of a heat unit formula for air temperatures with a base temperature of 14C and a maximum-reduced threshold at 40C, and a standard growing-degree-day formula for soil temperatures with a base temperature of 12C. Based on 2 years of data, 86.5% of the variation in the dry weight (on a log scale) could be predicted with this model. The base temperature for predicting time to anthesis of muskmelon transplants was established at 6.8C and the thermal time ranged between 335 and 391 degree-days during the 2 years of the experiment.

scholarly journals Determining Heat Unit Requirements for Broccoli Harvest in Coastal South Carolina

1997 ◽  
Vol 122 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Robert J. Dufault
Keyword(s):  
South Carolina ◽  
Standard Method ◽  
Growing Season ◽  
Base Temperature ◽  
Degree Days ◽  
Heat Unit ◽  
Mean Temperature ◽  
Coefficients Of Variation ◽  
The Mean ◽  
The Difference

The objective of this research was to determine the least variable method to predict the dates of the first and last broccoli (Brassica oleracea L. var Italica) harvests based on heat unit summation using coefficients of variation (cv). The method with the lowest cv for predicting first harvest was to sum, over days from planting to harvest, the difference between the growing season mean (GSM) temperature and a base temperature of 7.2 °C. If the GSM maximum (max) temperature, however, was >26.7 °C, an adjusted max temperature was calculated by first subtracting 26.7 °C from the GSM max temperature and then subtracting the GSM mean temperature. Then the growing degree days (GDDs) were summed by subtracting the base temperature of 7.2 °C from the average of the GSM minimum (min) and adjusted max temperatures. This method produced a cv of 3.96 compared to 4.13 for the standard method of summing over the entire growing season, the mean temperature minus the base temperature of 4.4 °C. The method with the lowest cv for predicting last harvest was to sum, over days from planting to harvest, the difference between the GSM max temperature and a base temperature of 7.2 °C. If the GSM max temperature, however, was >29.4 °C, the base temperature was subtracted from 29.4 °C and not the actual GSM max temperature. This method produced a cv of 3.71 compared to 4.10 for the standard method of summing over the growing season, the mean temperature minus the base of 4.4 °C.

scholarly journals A Heat Unit Model to Predict Growth and Development of Muskmelon to Anthesis of Perfect Flowers

1996 ◽  
Vol 121 (2) ◽  
pp. 274-280 ◽  
Author(s):  
Sylvie Jenni ◽  
Daniel C. Cloutier ◽  
Gaétan Bourgeois ◽  
Katrine A. Stewart
Keyword(s):  
Cucumis Melo ◽  
Dry Weight ◽  
Developmental Time ◽  
Base Temperature ◽  
Heat Unit ◽  
Independent Variables ◽  
Air Temperatures ◽  
Unit Model ◽  
Soil Temperatures ◽  
Unit Formula

Growth of `Earligold' muskmelon (Cucumis melo L.), expressed as plant dry weight from transplanting to anthesis, could be predicted using a multiple linear regression based on air and soil temperatures for 11 mulch and rowcover combinations. The two independent variables of the regression model consisted of a heat unit formula for air temperatures, with a base temperature of 14C and a maximum reduced threshold of 40C, and a standard growing-degree day formula for soil temperatures with a base temperature of 12C. Based on 2 years of data, 86.5% of the variation in the dry weight (on a log scale) could be predicted with this model. The base temperature for predicting developmental time to anthesis of perfect flowers was established at 6.8C and the thermal time ranged between 335 and 391 degree days in the 2 years of the experiment.

Using Land Cover, Population, and Night Light Data for Assessing Local Temperature Differences in Mainz, Germany

2015 ◽  
Vol 54 (3) ◽  
pp. 658-670 ◽  
Author(s):  
Jenny Lindén ◽  
Jan Esper ◽  
Björn Holmer
Keyword(s):  
Twentieth Century ◽  
Light Intensity ◽  
Central Europe ◽  
Urban Growth ◽  
Urban Areas ◽  
Surface Coverage ◽  
Daily Maximum ◽  
Source Areas ◽  
Maximum Temperatures ◽  
The City

AbstractUrban areas are believed to affect temperature readings, thereby biasing the estimation of twentieth-century warming at regional to global scales. The precise effect of changes in the surroundings of meteorological stations, particularly gradual changes due to urban growth, is difficult to determine. In this paper, data from 10 temperature stations within 15 km of the city of Mainz (Germany) over a period of 842 days are examined to assess the connection between temperature and the properties of the station surroundings, considering (i) built/paved area surface coverage, (ii) population, and (iii) night light intensity. These properties were examined in circles with increasing radii from the stations to identify the most influential source areas. Daily maximum temperatures Tmax, as well as daily average temperatures, are shown to be significantly influenced by elevation and were adjusted before the analysis of anthropogenic surroundings, whereas daily minimum temperatures Tmin were not. Significant correlations (p < 0.1) between temperature and all examined properties of station surroundings up to 1000 m are found, but the effects are diminished at larger distance. Other factors, such as slope and topographic position (e.g., hollows), were important, especially to Tmin. Therefore, properties of station surroundings up to 1000 m from the stations are most suitable for the assessment of potential urban influence on Tmax and Tmin in the temperate zone of central Europe.

scholarly journals Extreme Temperature Events in Serbia in Relation to Atmospheric Circulation

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1584
Author(s):  
Ivana Tošić ◽  
Suzana Putniković ◽  
Milica Tošić ◽  
Irida Lazić
Keyword(s):  
Atmospheric Circulation ◽  
Heat Waves ◽  
Extreme Temperature ◽  
Daily Maximum ◽  
Absolute Maximum ◽  
Extreme Temperature Events ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Maximum Temperatures ◽  
The Relationship

In this study, extremely warm and cold temperature events were examined based on daily maximum (Tx) and minimum (Tn) temperatures observed at 11 stations in Serbia during the period 1949–2018. Summer days (SU), warm days (Tx90), and heat waves (HWs) were calculated based on daily maximum temperatures, while frost days (FD) and cold nights (Tn10) were derived from daily minimum temperatures. Absolute maximum and minimum temperatures in Serbia rose but were statistically significant only for Tx in winter. Positive trends of summer and warm days, and negative trends of frost days and cold nights were found. A high number of warm events (SU, Tx90, and HWs) were recorded over the last 20 years. Multiple linear regression (MLR) models were applied to find the relationship between extreme temperature events and atmospheric circulation. Typical atmospheric circulation patterns, previously determined for Serbia, were used as predictor variables. It was found that MLR models gave the best results for Tx90, FD, and Tn10 in winter.

scholarly journals No Evidence of Excessive Leaf Production by Strawberries Grown in the Subtropics

Agriculture ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 197
Author(s):  
Christopher M. Menzel
Keyword(s):  
Dry Weight ◽  
Daily Maximum ◽  
Base Temperature ◽  
Sigmoid Function ◽  
Potential Yield ◽  
Leaf Production ◽  
Breeding Lines ◽  
Immature Fruit ◽  
Linear Pattern ◽  
Number Of Leaves

Fruit growth in most plants is strongly dependent on photosynthates produced in the leaves. However, if there are too many leaves, the lower part of the canopy becomes heavily shaded and yields are reduced. Experiments were conducted to determine if cultivars of strawberry (Fragaria × ananassa Duch.) grown in Queensland, Australia have excessive leaf production for adequate cropping. Seven cultivars and breeding lines were planted from March to May from 2004 to 2016 and the number of fully-expanded leaves, dry weight of the flowers and fruit, and yield/plant recorded (n = 23). Information was collected on daily maximum and minimum temperatures and solar radiation. Increases in the number of leaves/plant over the season followed a linear pattern (range in R2 from 0.81–0.99), with the relationship generally similar or better than a dose-logistic (sigmoid) function (range in R2 from 0.79–0.99). There were strong linear relationships between the number of leaves/plant and growing degree-days (GDDs), using a base temperature of 7 °C (range in R2 from 0.81–0.99). In contrast, there was no relationship between the number of leaves/plant produced each day and average season daily mean temperature (15.7 °C to 17.8 °C) or radiation (13.0 to 15.9 MJ/m2/day) (R2 < 0.10). Potential yield as indicated by the dry weight of the flowers and immature fruit/plant increased up to 40 to 45 leaves/plant (R2 = 0.49 or 0.50) suggesting that the cultivars do not have excessive leaf production. There was no relationship between yield and the number of leaves/plant (R2 < 0.10) because rain before harvest damaged the fruit in some years. These results suggest that the development of new cultivars with more leaves/plant might increase cropping of strawberries growing in the subtropics.

Production of Belarussian soyabeans (Glycine max) in the UK: predicting time to emergence

1999 ◽  
Vol 132 (4) ◽  
pp. 381-385 ◽  
Author(s):  
A. O'DELL ◽  
D. H. SCARISBRICK ◽  
D. A. BAKER
Keyword(s):  
Glycine Max ◽  
Reliable Method ◽  
Seedling Emergence ◽  
Planting Date ◽  
Reliable System ◽  
Heat Unit ◽  
Planting Dates ◽  
Coefficients Of Variation ◽  
Soil Temperatures ◽  
The Uk

A field experiment was carried out on soyabean (Glycine max (L.) Merr.) to measure the effect of planting date (soil temperature) on seedling emergence. Seeds were sown at weekly intervals on seven planting dates from April until the end of May in SE England in 1997. Planting date had no significant effect on final percentage emergence but had a highly significant effect on time to emergence. The coefficients of variation (c.v.) for the number of days to emergence (calendar days) were high (43–45%), and therefore not a reliable method for predicting emergence. Three accumulated heat unit (AHU) methods based on air and soil temperatures were compared with the calendar day method to determine the most reliable system for predicting seedling emergence. Accumulated soil temperatures above a base of 9·0 °C had the lowest c.v.s (8–15%) and were shown to be the most reliable predictor of emergence.

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