NITROGEN FERTILIZER MANAGEMENT PROGRAMS, NITRATE-POLLUTION POTENTIAL, AND ORANGE PRODUCTIVITY

摘要: ABSTRACT In a 5-year experiment in mature ‘Washington’ navel orange [Citrus sinensis (L.) Osbeck] orchard, leaching fractions were generally less than 0.05. Annual N rates needed to achieve high fruit yields up 368 kg per ha, greater reported most California experiments. That may have been associated with limiting soil moisture. leaf concentration was related yield and agreed previously guides. Better quality that restricted yield. Lower NO-3-N concentrations saturation extracts 3.5 m depth foliar-applied rather applied N. Mean values from eight sampling dates for annual leachable N, determined samples below the root zone, 124 soil-applied 155 78 respectively: 57.9, 17.5, 10.5 13.8 ha. At 1% level, 57.9 value significantly different other values, which did not differ each other. Average transit time nitrate water move 150 unsaturated zone calculated be about 1300 years. An increase rate substantially increased removed harvested crop. The average 49 N-balance studies showed that, general, yield, we could account more fertilizer irrigation water, indicating trees drawing part upon reserve With an of 147 ha annually accounted presumed denitrified or otherwise lost as volatile Low low production “N-production efficiency” (kg produced N) “fruit-N-removal × 100). Results suggest where are required, nitrate-pollution potential can reduced by using either combination foliar- instead only