Abstract
Abstract Long‐term experiments offer unique possibilities to study the effects of management practices on crops and soils with time. Characterizing temporal variability of grain yield provides an opportunity to distinguish between the effects of environment vs. management practices on grain yield, an important parameter. A long‐term study was established in 1912 in western Nebraska as part of a rotation study. In 1953, each plot was divided into manure (27 Mg ha −1 annually) and no‐manure sections to which fertilizer treatments of 0, 45, 90, 135, 180 kg N ha −1 , and 135 kg N + 80 kg P ha −1 were applied annually. Grain yield data from 1953 to 1993 for these treatments were used for fractal analysis and determination of fractal dimension ( D ), which is an indication of pattern of variation. A D value close to 1 indicates dominance of long‐term variation (or trend), while a D value close to 2 indicates dominance of short‐term (year‐to‐year) variation. Grain yield increased with increasing N application rate without manure, but no response to fertilizer application was observed where manure had been applied. Fractal dimensions ranged from 1.942 to 1.996, indicating significant domination of short‐term variation of grain yield in the past 41 yr in all treatments. There was no significant difference between D values for manure or fertilizer treatments. Soil fertility amendments did not alleviate year‐to‐year variability observed in the corn ( Zea mays L.) yield. Environmental factors like hail, fall freezing, and temperature variation during the growing season had a significant effect on the grain yield over the years. Although management practices can reduce temporal grain yield variability in some crops, variations in environmental factors in this study were great enough to dominate the yearly maize grain yield regardless of soil fertility amendments.
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Claims 6
Claim · model-written summary
Grain yield increased as nitrogen application rose without manure.
- Treatment
- increasing N application ratee0
- Outcome
- Grain yielde0
- Direction
- increasede0
- Comparator
- without manuree0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield increased with increasing N application rate without manure”
t0“Maize”
Claim · model-written summary
Fertilizer did not elicit a yield response where manure was applied.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no response to fertilizer application was observed where manure had been applied”
e1“Grain yield increased with increasing N application rate without manure”
t0“Maize”
Claim · model-written summary
Yield fractal dimensions of 1.942 to 1.996 indicated dominant short-term variation across treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fractal dimensions ranged from 1.942 to 1.996, indicating significant domination of short‐term variation of grain yield in the past 41 yr in all treatments”
t0“Maize”
Claim · model-written summary
Fractal dimension did not significantly differ between manure or fertilizer treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no significant difference between D values for manure or fertilizer treatments”
t0“Maize”
Claim · model-written summary
Soil fertility amendments did not alleviate yearly maize yield variability.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- Soil fertility amendmentse0
- Outcome
- year‐to‐year variability observed in the corn ( Zea mays L.) yielde0
- Direction
- did not alleviatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil fertility amendments did not alleviate year‐to‐year variability observed in the corn ( Zea mays L.) yield”
Claim · model-written summary
Hail, fall freezing and growing-season temperature variation significantly affected yield.
- Outcome
- grain yielde0
- Qualifier
- hail, fall freezing, and temperature variatione0
- Setting
- growing seasone0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Environmental factors like hail, fall freezing, and temperature variation during the growing season had a significant effect on the grain yield over the years”
t0“Maize”
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