Solution culture was used to investigate whether the high solution Na concentrations and Na: Ca ratios found in sodic soils could directly affect the early growth and nutrient uptake of cotton (Gossypium hirsutum L.). Cotton was grown in nutrient solutions with three Na:Ca ratios (46:1, 4:1 and 0.2:1 mM) and three electrical conductivities (EC) (2.5, 4.25 and 6 dS m −1 ) combined in a factorial design with four replicates. Most cotton growth parameters (including shoot and root dry weight, fruit number and weight) were unaffected by increasing solution EC or Na:Ca ratio, but at the highest Na concentration (56.6 mM), plant height was reduced. It was concluded that young cotton has the ability to tolerate solution Na concentrations up to those found in moderately sodic soils. Increasing solution Na:Ca increased plant root and shoot concentrations and plant accumulation for Na, and decreased them for Ca. Increasing EC also increased plant Na concentration and accumulation. Shoot K and P concentrations decreased with EC, but actually increased as the sodicity (Na:Ca ratio) of the nutrient solution increased. The results suggest that the low K and P concentrations commonly found in cotton grown in sodic soils are not a direct result of Na:Ca ratio in the soil solution.

Abstract. Soil sodicity is widespread in the cracking clays used for irrigated cotton (Gossypium hirsutum L.) production in Australia and worldwide and sometimes produces nutrient imbalances and poor plant growth. It is not known whether these problems are due primarily to soil physical or to soil chemical constraints. We investigated this question by growing cotton to maturity in a glasshouse in large samples of a Grey Vertosol in which the exchangeable sodium percentage (ESP) was adjusted to 2, 13, 19, or 24. A soil-stabilising agent, anionic polyacrylamide (PAM), was added to half the pots and stabilised soil aggregation at all ESPs. Comparison of the effect of ESP on cotton in the pots with and without PAM showed that, up to ESP of 19, the soil physical effects of sodicity were mainly responsible for poor cotton performance and its ability to accumulate potassium. At ESP >19, PAM amendment did not significantly improve lint yield, indicating that soil chemical constraints, high plant sodium concentrations (>0.2%), and marginal plant manganese concentrations limited plant performance. Further research into commercial methods of amelioration of poor physical condition is warranted rather than application of more fertiliser.

In Australia, the surface and subsurface soils of the majority of cotton (Gossypium hirsutum L.)‐growing regions are sodic. Application of organic amendments can be an option to stabilize the structure of sodic Vertisols due to their potential positive effect on soil physical properties. An incubation experiment was conducted for 4 wk in a temperature‐controlled (30°C) growth chamber to study the effect of organic amendments on the properties of two Vertisols with different sodicity levels. The exchangeable Na percentages (ESPs) in these Vertisol soils collected from the Australian Cotton Research Institute (ACRI) near Narrabri, New South Wales, and a commercial cotton farm near Dalby, Queensland, were modified such that three different sodicity levels resulted, i.e., nonsodic (ESP < 6), moderately sodic (ESP 6–15), and strongly sodic (ESP > 15). The organic amendments used were cotton gin trash (60 Mg ha−1), cattle manure (60 Mg ha−1), and composted chicken manure (18 Mg ha−1), as well as an unamended control. The organic amendments improved the physical properties of both Vertisols by decreasing clay dispersion. In the Dalby soil, cotton gin trash produced the largest decrease (29%) in the dispersion index over the control at the moderate sodicity level, whereas in the strongly sodic soil, the lowest dispersion index resulted from the application of chicken manure. Nutrient availability (N, P, and K) was also increased significantly at higher sodicity levels for both the ACRI and Dalby soils by using organic amendments. These results indicate that using organic amendments can be beneficial for the amelioration of sodic Vertisols and also to sustain soil quality.

Sodicity in Vertosols used for agricultural production can adversely affect the growth and nutrition of cotton (Gossypium hirsutum L.) plants. Cotton produced in sodic soils has reduced dry matter and lint yield and can develop toxic plant tissue concentrations of sodium (Na) but limited tissue concentrations of phosphorus (P,) potassium (K), and micronutrients. Crops produced on sodic soils frequently suffer from aeration stress after an irrigation or rainfall event, and it was hypothesised that the adverse physical and/or chemical conditions of sodic soils may exacerbate the effects of waterlogging. We measured the impacts of sodicity on the growth, nutrition, and root recovery time of cotton during and after waterlogging in two experiments. In the first, cotton plants were subjected to a 7-day period of inundation in Grey Vertosols with a range of exchangeable sodium percentage (ESP) values from 2 to 25%; 32P was placed in the pots and its accumulation in the plant was used to indicate root activity and recovery after the waterlogging event. In a second experiment, agar was dissolved in nutrient solutions with a range of Na concentrations (9, 30, and 52 mm) matching soil solution Na concentrations in sodic soils, in order to simulate a waterlogging event. Following the waterlogging event, the solutions were labelled with 32P, in order to determine the effect of sodic soil solution chemistry on the rate of recovery of cotton root function after the event. Plant nutrient analysis was used to determine the effects of sodicity and waterlogging on cotton nutrition. In both experiments, waterlogging reduced root activity and reduced the uptake and transport of labelled P by the cotton plants, decreased plant P and K concentrations, and increased the plant Na concentrations. Sodicity exacerbated the effects of waterlogging on root function and cotton nutrition in the soil experiment but not in the nutrient solution experiment, suggesting that any contribution of waterlogging to the patterns of nutrient accumulation in cotton crops produced in sodic fields occurs due to soil physical factors rather than soil solution chemistry.

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