Research Progress Report 347 August, 1968

Response of Soft Red Winter Wheat Varieties to Rates of Top-Dressed Nitrogen
on Two Soil Types in 1966 and 1967
R. K. Stivers, K. M. Day, J. H. Watkin, M. W. Alderfer and D. R. Griffith Agronomy Department and AES Outlying Farms

Introduction
The purposes of this experiment were to compare (1) performance of three different wheat varieties and (2) response to top-dressed nitrogen (N) on two different soils. It was thought that our newer wheat varieties would respond to higher rates of nitrogen with higher yields and with less lodging than would our older varieties.

Procedures
Four rates of top-dressed nitrogen and three soft red winter wheat varieties were tested on two different soils for two years. Cropping history, soil test values, and fertilization of these crops are given in Table 1.

At all locations, experiments had a split-plot design with 4 replications. Rates of top-dressed N were main plots and varieties were subplots. The older variety, Monon, was compared with the newer varieties, Riley and Benhur.

Results
Increased wheat yields for top-dressed N were efficient at this location in Runnymede 1966 (Table 2). At the 40 pounds per acre rate of top-dressed N, the yield in-
crease over the check was 9.5 bushels per acre or an increase of 1 bushel per acre for each 4.2 pounds per acre of top-dressed N. The next higher rate, 80 pounds per acre of N, was not as efficient, but it produced the largest yield increase, 12.5 bushels per acre, over the check treatment. This rate also produced the highest return, $16.45 per acre, for rates of top-dressed N. Per cent lodging increased from 8.7 to 28.8 per cent as the rate of top-dressed N was increased from 80 to 120 pounds per acre. Maximum plant height, as well as yield, was obtained at the 80 pounds per acre rate of top-dressed N. Riley had significantly lower lodging (9 or more per cent) and was significantly taller than Monon and Benhur. However, the three varieties were not significantly different in yield from each other in 1966.

On the same soil type and on the same farm in 1967, there was a much smaller response to top-dressed N (Table 3). The 40 pounds per acre rate of N resulted in the highest increased return over cost of the N. The yield level with N was as high as the previous year, however. Differences among varieties in lodging, test weight, and height were significant at the 1 per cent level. Monon had significantly more lodging than either Benhur or Riley. Benhur had a higher test weight than either Riley or Monon, and

PURDUE UNIVERSITY • Agricultural Experiment Station • Lafayette, Indiana