The effect of gypsum and other salts on the growth of narrow-leafed lupins
Titel:
The effect of gypsum and other salts on the growth of narrow-leafed lupins
Auteur:
McLay, C. D. A.
Verschenen in:
Communications in soil science and plant analysis
Paginering:
Jaargang 28 (1997) nr. 3-5 pagina's 313-328
Jaar:
1997-02
Inhoud:
Glasshouse experiments were conducted to establish the cause of poor lupin growth in the presence of gypsum in field trials which had been conducted in Western Australia. In the first experiment, Bradyrhizobium-inoculated lupins were grown in nutrient solutions with varying concentrations (1, 3, 5, and 10 mM) of calcium (Ca) and sulfate (SO4) added as either CaSO4, K2SO4, or CaCl2 to establish whether gypsum caused Ca or SO4 toxicity to the plants. Although a general decrease in lupin plant growth was observed as the concentration of each salt increased, there was no evidence that either Ca or SO4 directly caused toxicity to the plants. Two soil experiments were therefore conducted to investigate lupin growth responses to the salts in a soil environment. The first soil experiment was conducted in a yellow earth— the same soil in which lupins had been adversely affected by gypsum in the field. The second soil experiment was conducted in the topsoil of a siliceous sand. Basal nutrients and different rates of CaSO4, K2SO4, and CaCl2 were added so that similar amounts of Ca and SO4 were present for each treatment at a given application rate. In both soils, lupin growth generally decreased as the application rate of treatments increased, although the magnitude of the decrease in growth was higher in the yellow earth than the siliceous sand. The strongest correlation between lupin growth and a soil solution chemical property was a log-linear relationship between the shoot or root dry weight and the electrical conductivity (EC) of the soil solution. Plant nutrition was affected by different treatments, particularly with respect to nutrient balances. It is suggested that a high ionic strength in the soil, which results when gypsum is applied in the field, may contribute to the lupin yield decline. Possible reasons for the effect are discussed.
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