Date of Award:

1-1-1980

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

R. L. Smith

Abstract

The response of field corn to iron and zinc fertilization was studied using a split plot experimental design in Millard County, Utah, in cooperation with the Utah Stat e University Extension Agent and a local farmer. ~!ainp l ot treatment applications consisted, on an acre basis, of (1) 5 t ons of sulfuric acid, (2) 1 ton sulfuric acid, (3) 1.8 tons gypsum, (4) check plot. Subplot treatments were (1) Fe at 5 lbs/Ac, (2) Zn at 10 lbs/Ac, (3) Fe and Zn at 5 and 10 lb / Ac, respectively, (4) check plot . The iron and zinc applications were essentially rendered unavailable by reactions of the applied iron and zinc with the highly calcareous soil matrix. Experimental variability and the relatively low rates of applied micronutrients combined to produce insignificant yield responses to micronutrient fertilization.

Another study was conducted to predict the soil iron critical level. Five soils from Millard County, representing some of the soils low in iron and zinc,were selected for a greenhouse study.

All five of the soils were equal l y divided into three groups and assigned one of three pretreatments. One- third of the soils were stressed by successive croppings with corn and oats. One-third of the soils were fertilized with Fe chelate and znso 4 at 5 ppm each as a pretreatment. And one-third of the soils did not receive a pretreatment. The pretreatments were designed to obtain a broader range of soil iron concentrations.

After the pre treatments were completed on all of the soils, a randomized block experimental design was employed to measure potential yield increases in corn produced by the addition of Fe chelate . Two corn genotypes, an iron-efficient corn inbred (WF9) and an iron efficient corn mutant (Ysl/Ysl), were utilized in the gr eenhouse study. The treatments were (1) 5 ppm Fe chelate plus corn inbred WF9, (2) 5 ppm Fe chelate plus corn mutant Ysl/Ysl, (3) no Fe addition plus corn inbred WF9 , (4) no Fe addition plus corn mutant Ysl/Ysl.

Significant yield responses to Fe fertilization were determined by an LSD statistical test . Generally, soils with a DTPA extractable iron level greater than 5 ppm did not respond to applied iron. Similar yield responses were obtained for the iron-efficient and ironinefficient varieties. A tentative critical level of DTPA extractable iron of 5 ppm was proposed for the calcareous soils of Millard County, Utah.

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