Journal of Experimental Agriculture International

Aims: To calculate the lower and upper critical doses of Cu applied to a Haplic Cambisol on growth, gas exchange and mineral nutrition of xaraés grass plants (Brachiaria brizantha cv. Xaraés).

Study Design: The experiment was arranged in a completely randomised design with four replications.

Locality of Study: Department of Soil Science of the Santa Catarina State University, Lages, Brazil, between February and March 2015.

Methodology: Xaraés grass plants were cultivated in a greenhouse in pots with soil containing Cu doses in the following increasing order: 0, 30, 60, 120 and 200 mg kg^-1. Before plant cultivation, the Cu availability in the soil was determined. During plant growth, the net CO₂ assimilation rate, transpiration rate, stomatal conductance, SPAD index and extended plant height were measured. After harvest, the plant leaf area, specific leaf area, plant dry mass, nutrient accumulation in the shoots and Cu concentration in the roots and shoots were evaluated.

Results: Application of Cu in increasing doses to the soil resulted in a linear increase in the Cu availability which led to parabolic functions for plant growth, gas exchange and nutrient accumulation in the shoots. There was an exponential increase in the Cu concentration in the roots. Despite the increase in the Cu concentration in the shoots, the values do not exceed 12.70 mg kg^-1.

Conclusion: The lower and upper critical doses of Cu for xaraés grass plants cultivated in Haplic Cambisol are 62.60 and 128.92 mg kg^-1, respectively.