Agronomy Journal Journal of Natural Resources and Life Sciences Education
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Published online 1 November 1972
Published in Agron J 64:763-766 (1972)
© 1972 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
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Nitrogen-supplying Power of Some Tropical Soils of Puerto Rico and Methods for its Evaluation1

D. J. Lathwell, H. D. Dubey and R. H. Fox2

An evaluation of the N-supplying power of 10 representative Oxisols and Ultisols of Puerto Rico was made by continuous cropping in the greenhouse. Four chemical extraction methods as well as aerobic incubation procedures were used to obtain an index of N availability in these soils. Nitrogen produced during incubation was highly correlated with N released to the crops. Nitrogen extracted by all of the chemical methods used, especially total N extracted by 0.01 M CaCl2 solution and potassium sulfate, was highly correlated with N uptake by plants. These results showed that substantial quantities of N can be removed from these soils upon cropping. It was also shown that laboratory chemical methods as well as incubation procedures provide a reliable means for evaluating the N-supplying power of these soils.

Key Words: Chemical extraction procedures • Incubation • Continuous cropping • Ultisol • Oxisol

1 Joint contribution from the Department of Agronomy, Cornell University, Ithaca, N.Y., as Agronomy Paper No. 979 and the Department of Agronomy and Soils, Agricultural Experiment Station, University of Puerto Rico, Mayaguez Campus, Rio Piedras, Puerto Rico. This study was part of the work supported by the U. S. Agency for International Development under research contract csd-2490 entitled: Soil Fertility Requirements to Attain Efficient Production of Food Crops on the Extensive, Deep, Well-Drained but Relatively Infertile Soils of the Humid Tropics.

2 Professor of Soil Science, Cornell University; Associate Soil Microbiologist, University of Puerto Rico; and Assistant Professor of Soil Science, Cornell University, respectively.

Received for publication February 24, 1972.




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Copyright © 1972 by the American Society of Agronomy.