Effect of nitrogen fertiliser on nitrogen partitioning and pool sizes in irrigated Sultana grapevines
The growth and nitrogen (N) percentage of the annual components and the N percentage of the perennial components of unfertilised and fertilised (100 kg N/ha.season) irrigated grapevines (Vitis vinifera cv. Sultana syn. Thompson Seedless) were compared over 2 consecutive seasons. Leaf, stem and fruit samples were measured for dry matter yield and N content at about fortnightly intervals during the growing season, and samples of 1–2-year-old wood, trunk, cane and root were sampled for N content at about fortnightly intervals during the growing season and 4-week intervals during dormancy. Total vine biomass was assessed on unfertilised vines following fruit harvest in the second season. Total vine biomass at this time was about 13.1 kg dry matter/vine, 43% of which was below the soil surface. Dry matter and fruit yield of vines did not respond to N application until the second season with an increase in annual biomass and fruit yield of 75 and 140%, respectively. The N contents of all vine organs were related to vine phenology, with N percentage decreasing in all annual parts during the season. The N percentage in perennial parts was lowest near flowering and fluctuated from then until harvest depending on demand by annual parts, principally leaves and fruit, and supply.