Nitrogen Nutrition of the Pineapple Plant ,

Unpublished studies in the files of the Pineapple Research Institute of Hawaii indicate that under present cultural conditions the .pineapp1e plant displays superior performance with a foliar applied combination of ammonium and nitrate nitrogen than with either form of nitrogen alone. The studies presented here were undertaken to evaluate ammonium nitrate as a nitrogen source under different soil pH levels and fumigation regimes, using soil application of the carrier rather than foliar sprays. The studies compared ammonium ni.trate with the all-ammonium fertilizer ammonium sulfate and the all-nitrate fertilizer calcium nitrate at rates of 100, 200, and 300 1b/A, using soil pH values of 4.5 and 5.5. Fumigation used in conjunction with the nitrogen sources included no fumigation, fumigation with 1,2-dibromo-3ch10ropropane at 3 gal/A, and fumigation with a mixture of 1,3dich10ropropene and related hydrocarbons at 40 gal/A. A separate experiment was set up using the high and low rates of nitrogen to examine the effects of carriers and soil pH on reDiform nematode numbers in the absence of ft~igation. All experiments were of randomized complete block design with a factorial arrangement of treatments. Plants supplied with ammonium nitrate exhibited a slightly greater uptake of total nitrogen, no difference in protein nitrogen, a soluble nitrogen fraction intermediate in size, and a medium to high nitrate content compared to plants on all-ammonium and all-nitrate nutrition. Leaf calcium remained high compared to plants supplied with the other nitrogen carriers. The relative status of the nitrogen forms supplied was not changed by soil fumigation, though soil nitrification