Fertilizer rates change root distribution of grapefruit trees on a poorly drained soil
1998
Fibrous root were determined for 26-yr-old 'Marsh' grapefruit trees (Citrus paradisi MacF.) on sour orange (C. aurantium L.) treated with four nitrogen(N) rates (0, 56, 112, 168 kg N ha-1) on a poorly drained sandy soil. Roots 0-15, 15-30 and 30-60 cm and depths at four directions, and two positions from the tree trunk. The fibrous root density was significantly greater in the trees which received either 112, 168 kg N ha-1 as compared to that of the trees which received the lower N rates. Of the total roots sampled from the top 60 cm soil depth, 75% of the roots were in the 0-15 cm depth, and < 10% was in the 30-60 cm layer. More roots were present in the 15-30 cm depth for the trees which received either 112 or 168 kg N ha-1 than that of the trees which received the lower N rates. Root density was significantly greater near the emitter as compared to that either along the dripline, near the water furrow or along the bed top. The root distribution was more uniform in all four directions for the trees which received the lower N rates (0 or 56 kg N ha-1) as compared to those which received the higher N rates (112 or 168 kg N ha-1). The results suggested that the root development was likely to be limited by N deficiency if the N rate was lower than 112 kg N ha-1.
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