Mechanical and Hydric Stress Effects on Maize Root System Development at Different Soil Compaction Levels.

Moacir Tuzzin De Moraes,Henrique Debiasi,Renato Levien,João De Andrade Bonetti,Andrea Schnepf,Julio Cezar Franchini,Daniel Leitner

doi:10.3389/fpls.2019.01358

Abstract

Soil mechanical resistance, aeration, and water availability directly affect plant root growth. The objective of this work was to identify the contribution of mechanical and hydric stresses on maize root elongation, by modeling root growth while taking the dynamics of these stresses in an Oxisol into consideration. The maize crop was cultivated under four compaction levels (soil chiseling, no-tillage system, areas trafficked by a tractor, and trafficked by a harvester), and we present a new model, which allows to distinguish between mechanical and hydric stresses. Root length density profiles, soil bulk density, and soil water retention curves were determined for four compaction levels up to 50 cm in depth. Furthermore, grain yield and shoot biomass of maize were quantified. The new model described the mechanical and hydric stresses during maize growth with field data for the first time in maize crop. Simulations of root length density in 1D and 2D showed adequate agreement with the values measured under field conditions. Simulation makes it possible to identify the interaction between the soil physical conditions and maize root growth. Compared to the no-tillage system, grain yield was reduced due to compaction caused by harvester traffic and by soil chiseling. The root growth was reduced by the occurrence of mechanical and hydric stresses during the crop cycle, the principal stresses were mechanical in origin for areas with agricultural traffic, and water based in areas with soil chiseling. Including mechanical and hydric stresses in root growth models can help to predict future scenarios, and coupling soil biophysical models with weather, soil, and crop responses will help to improve agricultural management.

Highlights

Soil compaction is considered the main cause of the physical degradation of agricultural soils (Nawaz et al, 2013)
Maize root growth modeling, including soil physical limitations, can be used for the analysis of architecture development associated with soil water flow models, increasing the fundamental understanding of stress that acts on the growing roots
Experimental data showed that the no-tillage system provided the best soil physical conditions for maximum maize yields

Summary

Introduction

Soil compaction is considered the main cause of the physical degradation of agricultural soils (Nawaz et al, 2013). Physical Limitations to Maize Rooting growth is mainly directly affected by four physical factors in soils, which are temperature, aeration, resistance, and water content (Letey, 1985). It is indirectly affected by several soil characteristics, for example, texture, aggregate structure, and pore size and distribution (Letey, 1985). Mathematical modeling has become an important tool for describing the functionality of biophysical processes including soil–root interactions, such as water absorption and root growth (Dupuy et al, 2010). There are still very few models describing soil–plant interactions, between the physical (e.g., soil water flow, soil mechanics, gas flow, or solute transport) and biological (e.g., water uptake/ release, root system architecture, or shoot and root growth) processes to predict root growth (Vereecken et al, 2016)

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