Nitrogen-Fertilization Rate and Soil Nitrate Distribution for Microirrigated Sugarcane
- C. D. Stanley ,
- R. E. Green,
- M. A. Khan and
- L. T. Santo
IFAS, Univ. of Florida, Gulf Coast Research and Education Center, 5007 60th St. E., Bradenton, FL 34203
Dep. of Agronomy and Soil Science, 223 Sherman Lab.
Rm 107, Dep. of Agricultural Engineering, both with Univ. of Hawaii, Honolulu, HI 96822
Hawaiian Sugar Planters' Association, 99-193 Aiea Hts. Dr., Honolulu, HI 96701
Concern continues to grow over the fate of chemicals used in agricultural production and the associated potential for groundwater contamination. Management practices can directly influence the efficiency of inorganic fertilizer use by crops, and can affect the amount that moves away from the root zone. A field study was conducted to investigate the effect of three N-fertilization rates (17.8, 9.1, and 6.0 kg ha−1 wk−1) on NO3 distribution and movement for the first 24 wk of growth of microirrigated sugarcane (Saccharum officinarum L.) grown on a Wahiawa silty clay (clayey, kaolinitic, isohyperthermic Tropeptic Eutrustox). One uncropped treatment receiving 9.1 kg ha−1 wk−1 was included for evaluation without crop uptake. The plots received irrigation daily, with N being applied once weekly. Clusters of soil-solution extraction tubes were installed at depths of 15, 45, and 75 cm from the soil surface and 0, 30.5, 61, 91.5, and 122 cm away from microirrigation emitters to determine NO3 distribution patterns on a weekly basis. Soil water potential was monitored with tensiometers placed at similar locations. Results showed that all N levels were applied excessively early in the season and exhibited NO3 leaching beyond the root zone. Data collected at 22 wk after planting showed that the 6.0 kg ha−1 wk−1 rate had low NO3 concentrations through the soil profile, indicating a N-rate closer to crop requirements. Daily irrigation applications were probably excessive and may have contributed to loss of NO3 from the root zone for all treatments. This study demonstrated that a dynamic approach to fertilization and irrigation needs to be developed to minimize water and nutrient losses from the crop root zone.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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