Nutrient Management Research Database

A field study was conducted in 1992 at the U.C. Kearney Agricultural Center on sandy loam soil to measure the extent to which water and nitrogen moved below the root zone of a Thompson Seedless grape vineyard. The vineyard was drip irrigated with water and fertilizers delivered throughout the growing season to present nonstressed conditions. Season-long water flux below the root zone was only 23mm (slightly under 1 inch). With the measured nitrogen concentration in this quantity of water, only 1.5 kg nitrogen per hectare (1.3 lbs nitrogen per acre) was moved below the effective root zone of the crop. This study clearly shows that nitrogen fertilization and irrigation to fully meet water and nutrient requirements of grape vineyards can be done without contaminating groundwater.

• Five irrigation treatments were tested to determine nitrogen and irrigation flux beyond the rooting zone of grape vines.
  
  • control;
  • conventional drip with above ground water release;
  • buried drip (30cm below the soil surface);
  • buried drip (30cm) with phosphoric acid injected to prevent root intrusion;
  • buried lateral drip (30 cm) with in-line turbulent flow emitters;
  • and buried lateral drip (30 cm) with in-line turbulent flow emitters with slow release Treflan to prohibit root intrusion.
• Vineyard plots were irrigated uniformly to meet 100% of crop water needs and nitrogen and potassium was fertigated at weekly intervals beginning May 14th through July 6th.
• A total of 45 kg nitrogen per hectare and 150 kg potassium per hectare was applied.
• Soil water flux and nitrogen flux was measured to determine the potential for nitrogen leaching beyond the rooting zone.

• This study saw no statistically significant differences in yield among the 5 treatments.
• Average yield was 27.5 tons per hectare, though root disruption from burying lateral drip lines did reduce yields by 2 tons per hectare.
• Although there was considerable variation among the different plots, results indicate with either surface and subsurface drip systems, nitrogen fertilization and irrigation to fully meet the water and nutrient requirements of vineyards can be done without a potential for contamination of groundwater supplies.
• The total cumulative water flux for the season was 23mm and the maximum total nitrogen flux below the root zone was 1.5 kg nitrogen per hectare.
• Fertigation was done at weekly intervals beginning May 14th through July 6th.
• A total of 45 kg nitrogen per hectare and 150 kg potassium per hectare was applied.