Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Paul L. Carson


Objectives of this study were: (a) to evaluate several N soil tests that are used to estimate soil N availability, and (b) to measure the distribution of inorganic N in the soil profile after an application of fertilizer N. Small grain yield response from an application of 17, 34, or 67 kg N/ha was used as the parameter of N availability. These parameters were related to 23 independent variables by use of a step wise multiple regression program. Nitrogen soil tests and climatic factors (rainfall and temperature) were the independent variables involved in the analysis. Nitrogen soil tests included were hot water soluble N, distillable N from a hot Na4P2C7 extract, organic matter, total N, and soluble NO3-N. A multiple regression equation was developed that significantly (R = .793**) estimated N yield response of small grain from an application of 67 kg N/ha. The equation was: ∆Y”67 = .395X4 + .379X6 - .128X14 – 5.17 where ∆Y”67 = yield increase from 67 kg N/ha, quintal/ha; X4 = available soil moisture at planting, cm; X5 = rainfall 1-9 weeks after planting, cm; X6 = rainfall 5-61 days before harvest, cm; and X14 = NO3-N content of the 0-61 cm profile, kg N/ha. The NO3-N soil test was the only N soil test that was significantly related to N yield response from application of 67 kg N/ha. Three locations that involved N rate studies with corn were used to evaluate changes of N soil tests during the growing season. It was concluded that the only N soil test significantly increased by applied N was the NO3-N test. The data showed that soil samples for NO3-N should be taken in the fall or spring before planting for estimating N availability. Movement of NO3-N in the soil profile was calculated by Liven’s equation (91). Estimated NO3-N leaching was very similar to actual leaching (b = .99 and r2 = .745**). Most of the leaching water occurred during April , May, and October under South Dakota conditions.

Library of Congress Subject Headings

Soils -- Nitrogen content
Soils -- Fertilizer movement



Number of Pages



South Dakota State University