Identifying resource competition in maize based soil conservation systems using 13C and 15N isotopic discrimination

Publication Type

Journal contribution (peer reviewed)

Authors

Vu Dinh Tuan, Thomas Hilger, Georg Cadisch

Year of publication

2015

Published in

Archives of Agronomy and Soil Science

Series/labeling

available online

DOI

10.1080/03650340.2015.1074185

Page (from - to)

1-20

Keywords

Mais, SOIL CONSERVATION, Stabile Isotope, Vietnam

Soil conservation measures such as establishing grass barriers or cover crops effectively control erosion but also provoke competition which reduces yields of companion crops. We used ¹³C and ¹⁵N natural abundance profiles to identify causes of competition of soil conservation measures on a field with 59% slope in Northwest Vietnam three years after establishment. Treatments were maize under farmer’s practice (T1, control), maize with Guinea grass barriers (T2), maize under minimum tillage (MT) with Pinto peanuts as cover crop (T3), and maize under MT and relay cropped with Adzuki beans (T4). A pre-test using data from zero-N-plots revealed that abundance of water and limited nitrogen availability induced low grain N concentrations, enriched leaf d¹³C, and reduced maize grain yield. Similar low N leaf concentrations and elevated d¹³C values were observed in maize growing close to frequently pruned grass barriers under positive water balance conditions, indicating that yield decline in these rows can be attributed mainly to N competition. Enriched d¹⁵N values of maize from rows next to barriers indicated reliance on soil N rather than on ¹⁵N depleted fertilizer N. Vigorous cover crop growth under MT resulted in maize yield decline due to N competition while relay-cropped legumes did not trigger inter-species competition having a similar maize yield, leaf N concentration, d¹³C, and d¹⁵N as the control.