Illinois Fertilizer
Conference Proceedings
January 28-30, 1991
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Lyle Paul1
Many of the fertilizer recommendations that are currently made are based on the data from these studies and others that were done on University of Illinois soil fertility research fields around the state of Illinois. These recommendations were based on interim results during the studies. The overall studies were conducted for various periods of years and never summarized after the studies were completed.
Many of the fertilizer recommendations that are currently made are based on the data from these studies and others that were done on University of Illinois soil fertility research fields around the state of Illinois. These recommendations were based on interim results during the studies. The overall studies were conducted for various periods of years and never summarized after the studies were completed.
The studies being summarized include seven different projects with various designs. Following is a description of each of the studies:
Phosphorus annual and three year additions at Elwood: The study was an 18-year study at Elwood on phosphorus additions and the effect on soil test and yield. Phosphorus was added at the levels of 0 - 40 - 80 - 120 pounds per acre annually or 120 - 240 - 360 pounds per acre every three years for the first six years of the study. These plots were then split and the annual rates applied on all the plots in the next six years. Starting in 1982, no additional phosphorus was added to any of the plots. Yields were taken each year with the last harvest being in 1987. Soil samples were taken annually from spring of 70 to fall of 81 and then in 83, 85, and 87. The soil types in the study are Elliott silt loam, Andres silt loam, Drummer silty clay loam, and Ashkum silt loam with less than 1 percent slope. The data from this study has been used for information on the rate of build-up and the relationship of annual and three year applications of phosphorus. The rate of decline of the soil test with no fertilizer additions needed to be analyzed to determine what will happen to soil test and production if a producer discontinues fertilizer application.
Potassium and Phosphorus interaction study at Elwood: This interaction study was conducted over a 20-year period on Drummer silt loam, Andres silt loam and Symerton silt loam. The applications were started in 1968 with P and K rates of 0 - 40 - 80 - 120 pounds per acre. This study was designed so that there were corn and soybeans harvested each year from part of the study. In 1979, the high applications were made residual, and in 1983, all P and K rates were left at residual until the final harvest in 1987. Crop yields were taken each year and soil tests were taken in 1968, 1973, 1978, 1979, 1980, 1982, 1984 and 1986.
Phosphorus and pH interaction study at Shabbonao: This study was started in 1954 as part of a multi-state study on the effect of rock and super phosphate on crop yields. Part of the study was also at two different levels of the soil pH. The original study included a small grain and alfalfa rotation that was changed to a corn and soybean rotation in 1969. Yields were taken on each crop each year and soil tests were taken in 1966, 1971, 1980, 1985, 1987 and some in 1988. The application rates of phosphorus were 0 - 20 - 40 - 80 - 160 of superphosphate annually and the same rates of rock phosphate times 8 applied every 8 years. The application of superphosphate was stopped in 1985 and all plots have been residue since then with only selected plots harvested for yield since that point. These plots are on Flanagan silt loam with less than 1 percent slope.
Potassium soil test levels at Elwood: The study of the shortest duration was a seven year study at Elwood on K soil test levels and yield in a corn and soybean rotation. The first five years were used to get the soil K levels of approximately 200, 300, 400, & 500 established. The next two years, the plots were divided with K added at 0, 1, 2, and 4 times crop removal. Yields were taken each year and soil samples were taken each year from fall of 1980 to fall of 1987 except 1984. The soil type in the study is Elliott silt loam with less than 2 percent slope.
N. P. & K interaction study on timber soil at Elwood: This interaction study was conducted over a 25-year period on Blount silt loam. The practices were changed in 1973 to N rates of 0 - 60 - 120 - 180 - 240 pounds per acre, P rates of 0 - 30 - 60 - 90 - 120 pounds per acre, K rates of 0 - 30 - 60 - 90 - 120 pounds per acre. In 1983, all P and K rates were left at residual and N rates continued. Crop yields on the corn and soybean rotation on each crop were taken each year and the soil tests were taken in 1983, 1985 and 1987.
N. P. & K interaction study on Cisne soil at Brownstown: This study was changed in the early 1960s and again changed in the early 1980s. These plots were in a corn, soybean, and wheat rotation, and also continuous corn. Yields were taken on each crop each year and appropriate soil tests were also taken. The study of about 20 years looked at N, P, & K as well as no fertilizer and adequate lime or no lime and adequate P & K.
N & K interaction at Shabbona: This study was started in 1972. Yields were taken each year and soil tests were taken in 1977, 1985, 1987 and 1988. Corn was grown every year except one. The study was conducted on Flanagan silt loam with a slope of less than 1 percent. The nitrogen rates each of the years was 0 - 80 - 160 - 240 pounds per acre and the K levels were at the same values. The application of fertilizer was stopped in 1989 with the entire field being blanketed with a uniform nitrogen rate.
The analysis and summarization of these studies is continuing and are not yet in presentable, final form.
