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Response of Rice to Nitrogen and Calcium Nutrition¹

ABSTRACT

The influence of N and of Ca nutrition on growth and chemical composition of ‘Nova 66’ rice (Oryza sativa L.) was studied in the greenhouse. Rice plants were grown in soil supplied with four levels each of N (0, 100, 200, and 300 ppm) and Ca (0, 400, 800, and 1,200 ppm) fertilizer. The soil was submerged throughout the experiment.

Significant N x Ca interactions were obtained for both grain yield and straw weight. The interactions for grain yield revealed that yield increased as rate of N fertilizer increased, and increases were greatest when Ca levels increased simultaneously. In contrast, interactions for straw weight showed that N increased weight but the increases were lessened in the presence of Ca. Total dry weight (grain + straw) was significantly increased by N but was only slightly affected by Ca. Thus Ca increased grain yield, decreased straw weight, and markedly increased the grain:straw ratio.

Nitrogen content (g/pot) and Ca concentration of grain were greatly enhanced by both N and Ca fertilization. Greatest contents were obtained at the highest levels of N and Ca. In contrast, Ca lowered concentration of N (%) in both grain and straw and N content (g/pot) of straw. Total N contents (straw + grain) were also slightly lower in the presence of Ca. The reductions in N concentration and content increased with increasing Ca added. Evidence indicated that the effect of Ca may have been largely indirect, through its effect on K accumulation. The inhibiting effect of Ca was overcome partially when N fertilizer level was increased.

¹ Contribution from the Dep. of Agron., Univ. of Kentucky Agr. Exp. Sta., Lexington 40506. The investigation reported in this paper (71-3-57) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.

² Graduate Research Assistant and Associate Professor of Agronomy, respectively.

Received for publication June 7, 1971. Accepted for publication January 17, 1972.