Plant and Soil

, Volume 128, Issue 2, pp 115–126

Root distribution in relation to soil nitrogen availability in field-grown tomatoes

  • Louise E. Jackson
  • Arnold J. Bloom
Article

DOI: 10.1007/BF00011100

Cite this article as:
Jackson, L.E. & Bloom, A.J. Plant Soil (1990) 128: 115. doi:10.1007/BF00011100

Abstract

Tomato root growth and distribution were related to inorganic nitrogen (N) availability and turnover to determine 1) if roots were located in soil zones where N supply was highest, and 2) whether roots effectively depleted soil N so that losses of inorganic N were minimized. Tomatoes were direct-seeded in an unfertilized field in Central California. A trench profile/monolith sampling method was used. Concentrations of nitrate (NO3-) exceeded those of ammonium (NH4+) several fold, and differences were greater at the soil surface (0–15 cm) than at lower depths (45–60 cm or 90–120 cm). Ammonium and NO3- levels peaked in April before planting, as did mineralizable N and nitrification potential. Soon afterwards, NO3- concentrations decreased, especially in the lower part of the profile, most likely as a result of leaching after application of irrigation water. Nitrogen pool sizes and rates of microbial processes declined gradually through the summer.

Tomato plants utilized only a small percentage of the inorganic N available in the large volume of soil explored by their deep root systems; maximum daily uptake was approximately 3% of the soil pool. Root distribution, except for the zone around the taproot, was uniformly sparse (ca. 0.15 mg dry wt g-1 soil or 0.5 cm g-1 soil) throughout the soil profile regardless of depth, distance from the plant stem, or distance from the irrigation furrow. It bore no relation to N availability. Poor root development, especially in the N-rich top layer of soil, could explain low fertilizer N use by tomatoes.

Key words

ammoniummineralizationnitratenitrificationnitrogenrootstomato

Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • Louise E. Jackson
    • 1
  • Arnold J. Bloom
    • 1
  1. 1.Department of Vegetable CropsUniversity of CaliforniaDavisUSA