Abstract
Abstract Identical experiments were started at six locations in 1929 to determine response of cotton ( Gossypium hirsutum L.), vetch ( Vicia villosa L.) and corn ( Zea mays L.) to rates of P and K in a 2‐year rotation. Rates were revised in 1949 and 1958. Crops were changed in 1968 to corn, wheat ( Triticum aestivum L.) and soybeans ( Glycine max L. Merr.). Original soil samples and samples taken throughout the 50 years were analyzed using the Mehlich double‐acid extract. The objectives of this study are to show the effects of the rates of P and K on (i) yields of the six crops during the last 20 years and (ii) soil test levels of the six soils over the 50 years. On soils that received 14 to 18 kg/ha of P from 1929 through 1957, vetch responded to fertilizer P at six locations, corn at four locations, and cotton at two locations during the 1958‐1967 period. Response to P by corn, wheat, and soybeans was about the same during the next 11 years as for the previous crops. Large response to the first 28 kg/ha increment of K was produced by all crops at most locations. Only one of the six soils produced consistent response to the second 28 kg/ha increment of K. Vetch was the most responsive of the six crops to P, and cotton was most responsive to K fertilization. Rates of 14 to 18 kg/ha P increased soil test P from an average of 19 ppm in 1929 to 33 ppm by 1957. When applications were discontinued, the level dropped to that of untreated plots by 1973. Application of 27 kg/ha or more of P rapidly increased soil test P to “high” or “very high” levels, and these have been maintained by 30 kg/ha applications during the last 20 years of higher production. Plots that received no K for 50 years dropped from an average of 54 ppm in 1929 to 40 ppm by 1957 and have changed very little in the last 20 years. Rates of 18 to 28 kg/ha of K have maintained the soil test K level over the 50 years. Higher rates have increased K, even on soils with cation exchange capacities (CEC) < 5 meq/100 g. Rates of K accumulation showed a direct relationship to the CEC. Applications of 28 kg/ha of K were adequate to produce top yields and also to increase the level in five of the six soils.
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Claims 14
Claim · model-written summary
Vetch responded to P at all six sites.
Not reportedComparator
Verbatim
e0“vetch responded to fertilizer P at six locations”
Claim · model-written summary
Corn responded to P at four sites.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- fertilizer Pe1
- Outcome
- corne0
- Direction
- respondede1
- Value
- four locationse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“corn at four locations”
e1“vetch responded to fertilizer P at six locations, corn”
Claim · model-written summary
Cotton responded to P at two sites.
- Taxon
- cotton
Gossypium hirsutume0 - Treatment
- fertilizer Pe1
- Outcome
- cottone0
- Direction
- respondede1
- Value
- two locationse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cotton at two locations”
e1“vetch responded to fertilizer P”
Claim · model-written summary
All crops showed a large response to the first K increment at most sites.
Not reportedTaxonComparator
Verbatim
e0“Large response to the first 28 kg/ha increment of K was produced by all crops at most locations”
Claim · model-written summary
Only one soil showed consistent response to the second K increment.
Not reportedTaxon
Verbatim
e0“Only one of the six soils produced consistent response to the second 28 kg/ha increment of K”
Claim · model-written summary
P raised soil test P from 19 to 33 ppm by 1957.
- Treatment
- 14 to 18 kg/ha Pe0
- Outcome
- soil test Pe0
- Direction
- increasede0
- Value
- 33 ppme0
- Comparator
- an average of 19 ppm in 1929e0
Not reportedTaxon
Verbatim
e0“Rates of 14 to 18 kg/ha P increased soil test P from an average of 19 ppm in 1929 to 33 ppm by 1957”
Claim · model-written summary
Stopping P applications brought soil test P down to untreated levels by 1973.
- Treatment
- applications were discontinuede0
- Outcome
- the levele0
- Direction
- droppede0
- Comparator
- untreated plotse0
Not reportedTaxon
Verbatim
e0“When applications were discontinued, the level dropped to that of untreated plots by 1973”
Claim · model-written summary
Higher P applications raised soil test P to high levels, maintained by later applications.
- Treatment
- 27 kg/ha or more of Pe0
- Outcome
- soil test Pe0
- Direction
- increasede0
- Qualifier
- maintained by 30 kg/ha applicationse0
Not reportedTaxonComparator
Verbatim
e0“Application of 27 kg/ha or more of P rapidly increased soil test P to “high” or “very high” levels, and these have been maintained by 30 kg/ha applications”
Claim · model-written summary
Without K, soil test K declined from 54 to 40 ppm.
Not reportedTaxon
Verbatim
e0“Plots that received no K for 50 years dropped from an average of 54 ppm in 1929 to 40 ppm by 1957”
Claim · model-written summary
K at 18 to 28 kg/ha maintained soil test K.
Not reportedTaxonComparator
Verbatim
e0“Rates of 18 to 28 kg/ha of K have maintained the soil test K level over the 50 years”
Claim · model-written summary
Higher K rates increased soil K.
Not reportedTaxonComparator
Verbatim
e0“Higher rates have increased K, even on soils with cation exchange capacities (CEC) < 5 meq/100 g”
Claim · model-written summary
K accumulation rate was directly related to CEC.
Not reportedTaxonDirection
Verbatim
e0“Rates of K accumulation showed a direct relationship to the CEC”
Claim · model-written summary
K at 28 kg/ha produced top yields.
Not reportedTaxonComparator
Verbatim
e0“Applications of 28 kg/ha of K were adequate to produce top yields”
Claim · model-written summary
K at 28 kg/ha increased soil K in five soils.
Not reportedTaxonComparator
Verbatim
e0“Applications of 28 kg/ha of K were adequate to produce top yields and also to increase the level in five of the six soils”
The same questions in other papers
fertilization · organism · Zea mays (maize)Results differ
136 papers in the same direction as this paper · 20 in the opposite direction · 5 reporting no difference from an alternative
- negative
- no effect
- no effect
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See all 162 papers →fertilization · organism · Gossypium hirsutum (cotton)Positive and negative results
35 papers in the same direction as this paper · 2 in the opposite direction · 1 reporting no difference from an alternative
- negative
- no effect
- no effect
35 papers more in this group
See all 39 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.