How do water, compaction and heat stresses affect soybean root elongation? A review

Abstract

Soil physical limitations that affect directly crop root elongation are the water, heat and mechanical stresses. In the literature, there are few studies that present a clear relationship of root elongation rate and soil physical stresses that could be used into a root growth models. The aim of this study was to carry out a systematic review, compiling and analyzing the impacts of the physical limitations of the soil (water stress, heat stress and soil strength) on the root elongation rate of soybean. The PRISMA method was used to select scientific papers published in the Scopus and Web of Science databases. The terms "root elongation", "soybean", "Glycine max", "water stress", "mechanical impedance", "heat stress", "hypoxia", "soil penetration resistance", "matric potential" and "temperature" were used as selection criteria. These procedures resulted only in ten papers, which were published until June 2021. The results indicate that the soybean root elongation was increased due to the increase in soil temperature, until 30 °C. Soil penetration resistance reduce exponentially the root elongation, and 4 MPa was sufficient to slow root elongation to approximately 7% of its unimpeded rate. The root elongation decay exponentially due to the reduction of the water potential. Even though soil compaction, heat stress, and water potential are relevant factors that affect directly the soybean root elongation, very few studies have published comparisons of the root responses to soil physical condition for soybean.