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Populations of 100,000 plants per acre produced highest grain yields. Increased row width reduced yields significantly as expressed by the regression Ŷ = 117.11 − 0.72X, where Y is in bushels per acre and ✕ is inches. A significant interaction was found between plant spacing and irrigation water management but not between plant spacing and fertility level. Seasonal moisture use or efficiency was not affected significantly by plant spacing.

An optical autocorrelator is described which is based on a modified Sagnac two-mirror interferometer that operates in the zero-fringe mode. The real-time radiant flux output is the square of the autocorrelation of the aperture function. In a particular application, when the aperture function is the pupil function of a lens under test, the autocorrelator output is the MTF of the lens. The system is not limited in focal length; aperature size is limited only by the sizes of the beam splitters and mirrors. Experimental results are given with comparison data for both infinite-conjugate MTF and the autocorrelation of an annular aperture. Methods of adapting the system for measurement of the phase of the transfer function and for finite conjugate testing are also described.

In viewing systems that employ critical, Kohler, or collimated illumination, the illumination may frequently be characterized by the complex degree of coherence in the form of a first-order Bessel function divided by its argument. The anomalies that occur in the image of a tri-bar target viewed in partially coherent illumination of this form are discussed for a two-dimensional circular diffraction-limited imaging system. The Sparrow criterion, which in this case correlates with experimental measurements of resolving power, is applied to determine the resolution limit. The computed resolution-limit curve for a tri-bar target is shown and compared to the previously published two-point resolution-limit curve for a one-dimensional system and to the limiting values obtained in a two-dimensional system for coherent and incoherent illumination. In the latter case, the full curve is shown as a special case of the application of the Sparrow criterion to the partially coherent imaging equations for a circular two-dimensional system. Experimental confirmation of the calculations is given.

During seedling to crown root stages daily dry matter production was 30 to 50 pounds per acre and N uptake about 1 pound; both were increased only slightly by N fertilizer. During crown root through flowering stages increased growth and N uptake rates were further increased by irrigation and N fertilization, ranging from 240 to 340 pounds and from 4 to 6 pounds, respectively. Maximum production and N uptake occurred between soft and hard dough stages.

Grain yields were curvilinearly related to the number of irrigations, depletion of soil moisture, and increments of applied N. Evapotranspiration was related to number of irrigations and to available soil moisture. Plant growth response to applied N increased evapotranspiration slightly. Irrigation and applied N both increased the efficiency of water use. Maximum efficiency occurred at a yield level below maximum production.

A method of measuring the second-order degree of coherence in an arbitrary plane by means of a compact wavefront shearing interferometer is described. The prism interferometer previously described by Saunders produces two sheared images that interfere, allowing measurement of the degree of spatial coherence. If the degree of coherence is a function of coordinate differences only, the visibility is constant; otherwise it varies over the field. Experimental results are given.

Several letters to the editor are presented in response to articles in previous issues, including "How Western Union Speculates Land," in the June 8, 1974 issue, "Why Inflation Is So Hard to Cure," in the June 1, 1974, and "Federal Express Takes a Nose-Dive," in the June 15, 1974 issue.

Presents several letters to the editor. Comments on the article "Better Dead," by E.U. Condon; Discussion on the protests against the current civil defense program of the U.S.; Remarks on writer Nelson Algren's article on author Ernest Hemingway.