HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sims, J. L. Articles by Blackmon, B. G. Search for Related Content PubMed Articles by Sims, J. L. Articles by Blackmon, B. G. Agricola Articles by Sims, J. L. Articles by Blackmon, B. G.

Predicting Nitrogen Availability to Rice: II. Assessing Available Nitrogen in Silt Loams With Different Previous Year Crop History¹

ABSTRACT

Soil test methods that measure NH₄⁴-N in silt loams before and after incubation under waterlogged conditions were evaluated as predictors of N availability to ‘Nato’ rice (Oriza sativa L.) grown in the greenhouse. Eighteen soils for each of five previous year crop histories were utilized. All so ls were from crop rotations containing rice.

Coefficients of determination (r²) for the regression of N uptake by rice on NH₄⁺-N after 6 days incubation of soil from the different crop histories increased in the order of cotton (Gossypium hirsutum L.) < rice < lespedeza (Lespedeza striata Thumb.) < soybean (Glycine max L.) < reservoir (irrigation water storage or fish production), and ranged from .12 to .77. Exchangeable Ca was inversely related to N uptake and accounted for significant percentages of variation in uptake on all soils except those from reservoirs. Exchangeable Ca was not related to NH₄⁺-N production during incubation. For all previous year crop histories NH₄ -N in soil after 6 days incubation was a better single predictor of N uptake by rice than soil organic matter values.

Initial NH₄⁺-N content of reservoir soils was about 5 times greater than in soils of other crop histories. The amount in these silt loam soils from reservoirs (55 kg N/ha) was about half that found in previous studies for reservoir soils of clay texture. Multiple regression analyses indicated that including initial NH₄⁺-N together with NH₄⁺-N production during incubation improved the prediction of N uptake over NH₄ -N production values alone. Including exchangeable Ca together with initial NH₄⁺-N and NH₄⁺-N production values improved the prediction on all soils except those from reservoirs.

Key Words: soil organic matter • ammonium

¹ Contribution from the Arkansas Agr. Exp. Sta.

² Former Assistant Professor and former research assistant, Arkansas Agr. Exp. Sta., Stuttgart, respectively. The senior author presently is Assistant Professor of Agronomy, University of Kentucky, Lexington; the junior author presently is graduate assistant, Department of Forestry and Soils, Louisiana State University, Baton Rouge.

Received for publication October 27, 1966. Accepted for publication June 30, 1967.