Abstract
Abstract Fractal analysis has been used to characterize both temporal and spatial variability in plant and soil parameters. A plant parameter of prime concern is crop yield. Consequently, the temporal variability of 10 crops commonly grown in the USA was described using fractal analysis. Average yields of nine grain crops along with fiber yield of cotton ( Gossypium hirsutum L.) from 1930 to 1990 in the USA were used for semivariogram and fractal analyses. Semivariance was calculated for each crop for different year intervals ( h ). The slope of the regression line of log semivariance vs. log h for each crop was used to calculate fractal dimension [ D = (4 — slope)/2], which is an indication of the pattern of yield variability. A small D ‐value (near 1) indicates the dominance of long‐term variation, while a large D ‐value (near 2) indicates dominance of short‐term variation and nondominance or lack of long‐term variation or trend. From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [ Glycine max (L.) Merr.], oat ( Avena sativa L.), and barley ( Hordeum vulgare L.) to about sixfold in maize ( Zea mays L.). Crop improvement through plant breeding and the use of fertilizers and pesticides are presumably the main reasons for increased yield. Large yield differences were observed after 1960 for most of the crops studied, suggesting that risk resulting from year‐to‐year yield differences increased with improved yields. Fractal dimensions ranged from 1.20 to 1.47 for the crops studied, identifying long‐term trend as well as short‐term variation in yield of these crops. Rice ( Oryza sativa L.) had the smallest D ‐value, indicating that this crop had the least short‐term variation, while oat and soybean had the largest D , indicating greatest short‐term variation. Temporal variability in average crop yield in the USA was much smaller than typical spatial variability values reported by others for soil parameters. It appears that fractal analysis is useful in quantifying temporal variability in yield of various crops and can be applied to agronomic research to characterize temporal variations.
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Claims 10
Claim · model-written summary
Soybean yield rose about twofold from 1930 to 1990.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [ Glycine max (L.) Merr.], oat ( Avena sativa L.), and barley ( Hordeum vulgare L.) to about sixfold in maize ( Zea mays L.).”
e4“Temporal variability in average crop yield in the USA was much smaller than typical spatial variability values reported by others for soil parameters.”
Claim · model-written summary
Oat yield rose about twofold.
- Taxon
- oat
Avena sativae0 - Outcome
- yielde0
- Direction
- increasede0
- Value
- about twofolde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [ Glycine max (L.) Merr.], oat ( Avena sativa L.), and barley ( Hordeum vulgare L.) to about sixfold in maize ( Zea mays L.).”
Claim · model-written summary
Barley yield rose about twofold.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree0 - Outcome
- yielde0
- Direction
- increasede0
- Value
- about twofolde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [ Glycine max (L.) Merr.], oat ( Avena sativa L.), and barley ( Hordeum vulgare L.) to about sixfold in maize ( Zea mays L.).”
Claim · model-written summary
Maize yield rose about sixfold.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [ Glycine max (L.) Merr.], oat ( Avena sativa L.), and barley ( Hordeum vulgare L.) to about sixfold in maize ( Zea mays L.).”
Claim · model-written summary
Most crops had large yield differences after 1960.
Verbatim
e1“Large yield differences were observed after 1960 for most of the crops studied”
Claim · model-written summary
Yield fractal dimensions ranged from 1.20 to 1.47.
Verbatim
e2“Fractal dimensions ranged from 1.20 to 1.47 for the crops studied, identifying long‐term trend as well as short‐term variation in yield of these crops.”
Claim · model-written summary
Rice had the least short-term yield variation.
- Taxon
- Rice
Oryza sativae3 - Outcome
- short‐term variatione3
- Direction
- leaste3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Rice ( Oryza sativa L.) had the smallest D ‐value, indicating that this crop had the least short‐term variation, while oat and soybean had the largest D , indicating greatest short‐term variation.”
Claim · model-written summary
Oat and soybean had the greatest short-term yield variation.
- Taxon
- oat and soybean
Glycine maxAvena sativae3 - Outcome
- short‐term variatione3
- Direction
- greateste3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Rice ( Oryza sativa L.) had the smallest D ‐value, indicating that this crop had the least short‐term variation, while oat and soybean had the largest D , indicating greatest short‐term variation.”
Claim · model-written summary
Average crop yield varied less over time than soil parameters varied spatially.
Verbatim
e4“Temporal variability in average crop yield in the USA was much smaller than typical spatial variability values reported by others for soil parameters.”
Claim · model-written summary
Fractal analysis was judged useful for quantifying temporal yield variation.
Not reportedComparatorValue
Verbatim
e5“It appears that fractal analysis is useful in quantifying temporal variability in yield of various crops”