Guar root and shoot growth as affected by soil compaction

Doglas Bassegio,Marcos Vinicius Mansano Sarto,Jaqueline Rocha Wobeto Sarto,Ciro Antonio Rosolem

doi:10.1590/1983-40632018v4852189

Abstract

ABSTRACT Guar (Cyamopsis tetragonoloba L.) is commonly grown in arid lands, because of its high drought-tolerance. However, soil compaction may be a limiting factor to its growth. This study aimed to evaluate the guar growth, according to the soil penetration resistance (0.20 MPa, 0.33 MPa, 0.50 MPa, 0.93 MPa and 1.77 MPa, in a layer with depth between 0.15 m and 0.20 m), in a Rhodic Acrudox soil. The shoot and root dry mass, root length by the Q1/2 index (mechanical soil penetration resistance in which the root growth is reduced by 50 %) and root diameter were evaluated. The impairment of the guar shoot growth begins when the penetration resistance is greater than around 1 MPa. The soil compaction alters the distribution of guar roots in the soil profile, concentrating them in the 0.15 m layer, but it does not prevent roots from penetrating this layer and developing in depth. The root diameter increases in the compacted layer. A soil penetration resistance of up to 1.77 MPa does not influence the root length density below the compacted layer, as well as the total root length density of guar. Although the guar Q1/2 index is greater than 1.58, the shoot and root dry mass are impaired.

Highlights

There is a need for the introduction of plants with industrial potential that are tolerant to the abiotic stresses characteristic of tropical climates
Soil was collected at a depth of 0.00-0.20 m, from a Latossolo Vermelho distroférrico (Santos et al 2013), or Rhodic Acrudox (USA 2010), and sieved through a 4 mm mesh
The chemical analysis was conducted based on the recommendations of Raij et al (2001), with the following results: CaCl2 = 0.01 mol L-1; pH = 5.1; organic matter = 27 g dm-3; P resin = 34 mg dm-3; K+ = 7 mmolc dm-3; Ca2+ = 48 mmolc dm-3; Mg2+ = 17 mmolc dm-3; cation exchange capacity (CEC) = 105 mmolc dm-3; and saturation basis = 68 %

Summary

Introduction

There is a need for the introduction of plants with industrial potential that are tolerant to the abiotic stresses characteristic of tropical climates. In this context, guar (Cyamopsis tetragonoloba L.), a legume of the Fabaceae family, may be an alternative in crop rotation systems (Gresta et al 2013, Shekhawat et al 2016), given its wide industrial application (Kumar et al 2017) and drought tolerance (Kumawat & Dayanand 2015). Guar is cultivated primarily as a commercial crop in India, which globally ranks the highest position, in terms of guar production (75-82 %), followed by Pakistan (10-12 %) (Kumar et al 2017).

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Results