Title page for ETD etd-05132005-111649


Document Type Master's Dissertation
Author Kamper, Maarten
URN etd-05132005-111649
Document Title Changes in the soil volume exploited by roots as influenced by differential treatments
Degree MSc (Soil Science)
Department Plant Production and Soil Science
Supervisor
Advisor Name Title
Prof A S Claassens Committee Chair
Keywords
  • corn effect of phophorus on
  • corn effect of potassium on
  • roots development
  • soil science
  • corn effect of nitrogen on
Date 2004-09-01
Availability unrestricted
Abstract
Due to the fact that the mechanism of acquisition of phosphorus (P) by roots, is mainly by interception, sufficient P uptake is only ensured by maximal root development ("exploitation"). Pot and field trials were conducted to determine the percentage exploitation of the soil volume by roots. The influence of P on root growth of Zea Mays was also studied. Previously, roots were described in terms of root density (cm cm-2, cm cm-3, gram cm-2 and gram cm-3). In this study roots are described in terms of exploitation which combines length, mass and the rhizosphere. The Gompertz function was used to model exploitation by roots as influenced by P application.

P along with nitrogen and potassium, had a highly significant (P < 0.001) effect on root growth in the pot experiments. The root systems' function changed after 14 days from nutrient acquisition to shoot supportive.

P had no significant effect on root growth in the field trial. Growth was governed by soil moisture, as dryer positions exhibited higher growth. The high P plot had much less root growth in the subsoil than the low P plot. Gompertz functions revealed subtle differences between different treatments.

During the first two weeks (when most P uptake occur) roots exploited at the most 1 % of the top soil volume. This implies that any soil analysis (Bray-1 value), should be divided by ≈ 100 to render the "exploitable" P. When considering the total P uptake of a maize crop (5 kg P ton-I), this means that the crop acquires only ≈ 6% of its P from the "plant available" pool (that is represented by the Bray-1 value). This suggests that roots are indeed able to extract the P from "plant unavailable" pools. Therefore, the term "plant available" is misleading and not descriptive concerning P uptake, and its use should be discontinued.

2004 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Kamper, M 2004, Changes in soil volume exploited by roots as influenced by differential P treatments, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-05132005-111649/ >

H955/ag

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