The Magruder Plots A Century of Wheat Research in Oklahoma A.C. Magruder Horace J. Harper Robert L. Westerman Oklahoma State University

CheckPNPK

(6) Nitrogen, Phosphorus, Potash and Lime Lime (5) Nitrogen, Phosphorus and Potash (4) Nitrogen and Phosphorus (3) Phosphorus (2) Check (1) Manure every four years at 240 lbs N/ac 10’ 100’ 125’ Magruder Plots 1947-present Stillwater Experiment Station Magruder Plots 1947-present Stillwater Experiment Station

Treatments n Manure 1892, 240 lb N/ac every 4 yr n Check 1892, no nutrients applied n P 1929, 30 lb P 2 O 5 /ac/yr n NP 1929, 60 lb N and 30 lb P 2 O 5 /ac/yr, n NPK 1929, 60 lb N, 30 lb P 2 O 5 and 30 lb K 2 O/ac/yr n NPKL 1929, 60 lb N, 30 lb P 2 O 5, 30 lb K 2 O/ac/yr and lime (1954) n Manure 1892, 240 lb N/ac every 4 yr n Check 1892, no nutrients applied n P 1929, 30 lb P 2 O 5 /ac/yr n NP 1929, 60 lb N and 30 lb P 2 O 5 /ac/yr, n NPK 1929, 60 lb N, 30 lb P 2 O 5 and 30 lb K 2 O/ac/yr n NPKL 1929, 60 lb N, 30 lb P 2 O 5, 30 lb K 2 O/ac/yr and lime (1954)

Changes n Plots relocated in 1947 –0-6 and 6-15” profiles moved separately n Variety –Fultz, Currell, Kharkov, Turkey, Tenmarq, Pawnee –Ponca, Concho, Kaw, Scout 66, Triumph 64, Osage –TAM W 101, Karl, Tonkawa n N Rate –33 lb N/ac –60 lb N/ac 1968-present n N Source: NaNO 3 and NH 4 NO 3 n P Source: OSP, TSP n Plots relocated in 1947 –0-6 and 6-15” profiles moved separately n Variety –Fultz, Currell, Kharkov, Turkey, Tenmarq, Pawnee –Ponca, Concho, Kaw, Scout 66, Triumph 64, Osage –TAM W 101, Karl, Tonkawa n N Rate –33 lb N/ac –60 lb N/ac 1968-present n N Source: NaNO 3 and NH 4 NO 3 n P Source: OSP, TSP

N N N P P P K K K Reliability

y = x r = 0.92 y = x r = 0.76 y = x r = 0.57 y = x r = 0.87 y = x r = 0.88 y = x r = Manure Check P P P P P P NP NPK NPK+L Environment mean, bu/acre Grain yield, bu/acre Stability Analyses K Response in Stress Environments Stability Analyses K Response in Stress Environments

Manure Check P P P NP NPK NPKL Soil pH Year

ManureManure CheckCheck Soil organic matter, % Year

Manur e Check Total soil N, % Year

Environment Mean Year Grain yield, bu/ac Grain Yield Trend

All Experiments y = x R R 2 2 = Year Average Yield, bu/ac

Conclusions n Manure applications were shown to increase yields very early in the study n Applied P fertilizer increased grain yields ( ), but no increases were found as a result of applying N, K or lime up to 1957 n After 100 years of cultivation and continuous wheat production, N is deficient for crop production on this soil. Now, N, P and K are required for maximum yields n Manure applications were shown to increase yields very early in the study n Applied P fertilizer increased grain yields ( ), but no increases were found as a result of applying N, K or lime up to 1957 n After 100 years of cultivation and continuous wheat production, N is deficient for crop production on this soil. Now, N, P and K are required for maximum yields

n Application of commercial fertilizer has improved yields as much as applications of barnyard manure n Potassium addition had no notable effect on crop yields until 1988, but since that time has been needed for maximum yields. Liming has only been slightly beneficial at this location n Soil organic matter has declined from 4.0% to <1.25% and has tended to stabilize. Barnyard manure has slowed the decay of soil organic matter compared to the unfertilized plot. n Long-term relevancy achieved via the use of simple treatment structure. n Application of commercial fertilizer has improved yields as much as applications of barnyard manure n Potassium addition had no notable effect on crop yields until 1988, but since that time has been needed for maximum yields. Liming has only been slightly beneficial at this location n Soil organic matter has declined from 4.0% to <1.25% and has tended to stabilize. Barnyard manure has slowed the decay of soil organic matter compared to the unfertilized plot. n Long-term relevancy achieved via the use of simple treatment structure.

n Soil test indices for P and K have been increased to adequate levels by continuous application of phosphorus and potassium fertilizer and barnyard manure applications. n The initial objective of this study was to determine how long this reddish prairie soil could produce wheat. After 100 years of soil fertility research with multiple variables on continuous wheat, the question remains unanswered. It has been shown that inorganic fertilizer applications as well as manure applications result in sustainable and environmentally acceptable agricultural production systems. n Soil test indices for P and K have been increased to adequate levels by continuous application of phosphorus and potassium fertilizer and barnyard manure applications. n The initial objective of this study was to determine how long this reddish prairie soil could produce wheat. After 100 years of soil fertility research with multiple variables on continuous wheat, the question remains unanswered. It has been shown that inorganic fertilizer applications as well as manure applications result in sustainable and environmentally acceptable agricultural production systems.