Fertilizers for Potato Soils by Milton Whitney is a historical analysis of published fertilizer experiments on potatoes. Issued on May 9, 1910, as Bulletin No. 65 of the United States Department of Agriculture’s Bureau of Soils, it brings together 1,769 tests reported by agricultural experiment stations.
A collection of field experiments
The introduction defines which results were accepted. A test needed a recorded yield from an unfertilized check plot, a determinable quantity of the material applied and a yield or increase that could be calculated.
The collection includes station-farm trials and work by cooperating farmers when adopted and published by the stations. The paper therefore analyzes an assembled body of experiments rather than presenting one newly planted field trial.
Tables arrange the tests by year and state. The geographical spread and the long period represented help explain both the ambition of the analysis and the difficulty of drawing conclusions from such varied material.
Why the check plots matter
Whitney begins the detailed discussion with yields from the unfertilized plots. These establish the comparison against which the effect of a treatment is measured.
The report draws attention to variation among check plots, even within the same field. A difference between treated and untreated ground needs to be read with that natural variation in mind.
The author also states that descriptions of soils in the original reports were generally insufficient for a satisfactory grouping by their physical or chemical differences. Instead, he groups material by the yield on unfertilized ground.
This is one of the most useful methodological passages in the bulletin. It shows how the available records determined what the investigator could analyze, and which questions the compilation could not answer directly.
Materials, prices and crop value
The next sections consider the kinds and costs of fertilizers and the value assigned to potatoes. The tables include single substances and numerous mixtures, with quantities and costs used to compare the resulting crop increases.
Mineral and organic materials appear in separate groupings and in combinations. Names familiar in older farm literature, including nitrate of soda, acid phosphate, potash materials, ground bone and cotton-seed meal, can be followed through the tables.
The prices are assumptions used in the original calculation. They are valuable for interpreting the historical argument, but they are not current purchase prices or a present-day budget for growing potatoes.
Reading the tables
The main tabulation distinguishes the number of experiments, the range of crop increases, fertilizer quantities, cost, average increase and average gain. It preserves negative results as well as positive ones.
A range can be especially revealing. An average may summarize many observations while concealing substantial differences among soils, seasons and treatments, and the bulletin repeatedly acknowledges that variation.
Readers researching agricultural trials will find a compact example of attempts to compare unlike experiments through a common set of measures. Its value depends on reading column headings, units and qualifications together.
Mixtures, application amounts and limitations
Later sections examine the effectiveness of single materials and mixtures, the effect of increased application amounts and the relationship between fertilizer response and the productiveness of untreated soil.
The summary presents Whitney’s conclusions from the collected records. These are the findings of an early soil-science analysis and should be read in their historical setting, with attention to the grouping method and the quality of the underlying reports.
The author expressly says the records do not permit a judgment of the cumulative effects of repeated fertilizer use on the same soil over a long series of years. A short-term crop response and a long-term change in soil condition are therefore distinct questions here.
Use in a reference collection
This free ebook suits readers studying potato husbandry, the history of soil fertility and the interpretation of agricultural experiments. It is strongest as a record of evidence and reasoning, rather than as a ready-made fertilizer prescription for a particular garden.
The PDF has 22 digital pages, including covers and preliminary matter. Much of the content consists of small, closely set tables. Enlarge those pages, keep units in view and use the printed contents to move between the tabulations and their explanation.
Book details
- Author: Milton Whitney
- Publisher: Government Printing Office, Washington; USDA Bureau of Soils
- Year: 1910
- Edition: Bureau of Soils Bulletin No. 65; issued May 9, 1910
- Digital length: 22 PDF pages
- Language: English
- File size: 1.50 MB
