Exploring the response of sugar cane to sodic and saline conditions through natural variation in the field

Abstract

Soil sodicity and salinity are known to reduce yields of sugar cane ( Saccharum spp.), but little quantitative information is available. The aim of this study was to determine the response of irrigated sugar cane to sodic and saline conditions, using natural variations in the field. Sixteen sites, in which sodicity and salinity varied within a field, were selected in the Burdekin district (19°30′S, 147°20′E) of Queensland, Australia. The soils were clay loams to clays, with neutral to alkaline pH. At each site, a 3-row (4.5 m) wide strip of cane that cut across variable areas was identified. The strips were between 150 and 600 m long, and cane yield was measured in selected sections, each 20–30 m long. Soils were analysed for solution chemistry, exchangeable cations, nutrients, organic C and particle size distribution. Cane yield (fresh weight) varied from 1 to 252 Mg ha −1. Soil electrical conductivity (EC 1:5) and exchangeable sodium percentage (ESP), weighted for depth using root mass distribution data, together accounted for 79.5% of the variation in yield over all sites. Only 7.1% of the variation in yield was accounted for by site-related factors, including crop cultivar and class (plant crop or ratoons). Sodicity- and salinity-related parameters (EC 1:5, electromagnetic induction meter (Geonics EM38) readings, exchangeable Na content, and ESP) were highly correlated. Over all sites, EC 1:5 at 0–0.125 m depth varied from 0.04 to 0.77 dS m −1 (mean 0.21 dS m −1) and at 0.5–0.625 m depth varied from 0.03 to 1.50 dS m −1 (mean 0.50 dS m −1). ESP at 0–0.125 m depth varied from 1.3 to 75.4% (mean 13.4%) and at 0.5–0.625 m depth varied from 1.7 to 78.7% (mean 29.3%). The clear indication obtained of the dominant soil properties limiting yield showed the value of the experimental approach, using natural variability in the field.