Abstract1. A survey of the literature of earlier fertilizer trials in Puerto Rico in which the efficiency of ammonium sulfate, sodium nitrate, tankage, and calcium cyanamide were compared revealed that there was no significant difference in the yield response of sugarcane to these nitrogen carriers. 2. Experiments were conducted in which ammonium sulfate and ammonium nitrate were compared as nitrogen sources for sugarcane. The results at Río Piedras and Guánica showed no significant differences in yield of cane or sugar regardless of which was used. At Isabela there was a better response to ammonium sulfate than to ammonium nitrate in the first ratoon, but it was significant only at the 5-percent point. 3. Uramon and cyanamide when tested along with the ammonium sulfate and nitrate experiments at Río Piedras and Isabela, produced no significant responses as compared with the other nitrogen sources. At Río Piedras liquid ammonium nitrate produced the lowest yield of any nitrogen source used. 4. Ammonium sulfate is the chief nitrogen source used in Puerto Rico. Its use is chiefly dictated by economic and manufacturing conditions. Ammonium nitrate, which is cheaper per unit of nitrogen, cannot be used at present because of extremely high transportation costs based on its explosiveness. 5. A discussion of the agro-economic aspect of nitrogen sources is presented.
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