Effect of copper on soil enzyme, alkali-hydrolyzable N and sugarcane growth.

[Objective]The present experiment was conducted to study the effects of Cu content on soil properties and sugarcane growth in order to provide information for safe agricultural production and to develop control measures for heavy metal pollution. [Method]A pot experiment was conducted for growing sugarcane plants. The soil was mixed with different concentrations of copper (44.15, 61.65, 79.15, 86.65, 94.15, 269.15, 444.15 mg/kg), and samples of both soil and plants were taken for analyses at different growth stages of sugarcane plants. [Result]The results showed an initial increase in activity of urease in soil with increasing Cu concentration, which later decreased to its minimum at 86.65 or 94.15 mg/kg Cu;Alkali-hydrolyzable N content in soil at each stage of sugarcane growth increased initially and then decreased with increasing Cu concentration in the medium; The Cu content in soil significantly and negatively affected the urease activities for whole duration of plant growth as revealed by the significant negative correlations of Cu content with urease activity at tillering and elongating stages; Cu content positively (at tillering and elongating stages) and negatively affected the alkali-hydrolyzable N content of soil. The plant height, stalk diameter, cane yield and juice brix of sugarcane increased initially and then decreased with increasing Cu concentration. The critical value of Cu for plants was found as 269.15 mg/kg soil and 7.82 mg/kg cane stalk dry weight. [Conclusion]Urease enzyme activity, alkali-hydrolyzable N content in soil and yield and quality of sugarcane were improved with the increase in Cu content in soil up to critical level, above which plants were severely affected; The Cu content negatively affected the activities of urease in soil.