| Experiment 501: Sorghum Grain Yield Response to Nitrogen, Phosphorus and Potassium Fertilization, Lahoma, OK | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
AbstractSorghum grain yield
response to long-term applications of nitrogen (N), phosphorus (P) and
potassium (K) remains extremely important relative to maximum yields and
the potential for environmental risk.
Experiment 501 was established in 1971 to evaluate fertilizer
applications on grain sorghum grown in western Oklahoma.
This experiment has now been conducted for 30 years.
Response to applied N was not seen until the second decade of the
experiment. In the last 20
years of the experiment, sorghum grain yields have been maximized at an
average annual N rate of 60 lb N/ac.
Grain % N levels were generally maximized at the same N rate as
that noted for maximum yields. To
date, no response to applied P and/or K has been found in this long-term
grain sorghum experiment. Materials and MethodsIn the spring of 1971, Experiment 501 was established under conventional tillage on a Grant silt loam (fine-silty, mixed, thermic Udic Argiustoll) at the North Central Research Station near Lahoma, Oklahoma. Grain Sorghum has been planted for 20 continuous years in 36 inch rows at seeding rates of 4.3 pounds per acre. The variety 'ACCOR1019' was planted from 1971-79, 'DKC42Y+' from 1980-1994, SG-822 from 1995-1998 and SG-753 from 1999 to present. Experimental methods, application dates and changes over time are reported in Table 1. The experimental design employed is a randomized complete block with four replications. Fertilizer treatments and average grain yield means over selected periods are reported in Table 2. Individual plots at this site are 20 feet wide and 60 feet long. The center 2 rows of each plot were harvested for yield using a conventional combine the entire 60 feet in length. In addition to grain sorghum yield measured every year (exception was 1973 where crop failure resulted due to lack of rainfall for most experiments at the North Central Research Station), periodic soil and grain samples were taken for further chemical analyses. Results from surface (0-6 inches) soil test analyses from samples collected in 1988 are reported in Table 3. Table
1. Treatment
applications, and experimental management
for continuous sorghum Experiment 501, Lahoma, OK, 1971-2000.
Table 2. Treatment structure of long-term sorghum Experiment 501, sorghum grain yield and percent N in the grain for selected periods, Lahoma, OK, 1971-1999.
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