ACCUMULATION POTENTIAL AND NUTRIENT CYCLING OF APPLE OF PERU (Nicandra physalodes)

POTENCIAL DE ACÚMULO E CICLAGEM DE NUTRIENTES DE JOÁ-DE-CAPOTE (Nicandra physalodes)

ABSTRACT

Weed residues can influence nutrient cycling in agroecosystems. Quantifying this potential nutrient source may influence weed control and fertilisation practices. Nicandra physalodes (L.) Gaertn. is a weed with a short life cycle and a great ability to accumulate dry matter. Field observations suggest that N. physaloides residues are easily decomposed in soil. The objective of this study was to evaluate the effect of increasing of N, P and K doses on the growth of N. physalodes, as well as the nutrient content, chemical characteristics and C/N ratio of the weed. A randomised block design, arranged in split-plot with three replications, was utilised. The main plots were given four doses of NPK (Dose 1 - 0, 0.3 and 17.2 mg dm^-3; Dose 2 - 30, 450.3 and 75.4 mg dm^-3; Dose 3 - 60, 900.3 and 133.4 mg dm^-3; and Dose 4 - 120, 1800.3 and 249.68 mg dm^-3), and the subplots were harvested at ten time points after emergence (26, 33, 40, 47, 54, 61, 76, 91, 106 and 121 days). Higher dry matter production and N, P and K content were observed in plants grown on higher levels of fertiliser. The increase of N, P and K levels in the soil resulted in greater total accumulation of these macronutrients. The highest macronutrient contents were K and N. The treatments did not affect neutral detergent fibre (NDF), acid detergent fibre (ADF) and C/N ratio of plant. N. physalodes had low C/N ratio, low NDF and ADF levels, and great nutrient accumulation, suggesting that this plant is quickly decomposed, providing a rapid cycling of nutrients.

Keywords:
Apple of Peru; Acid detergent fibre; C/N ratio; Neutral detergent fibre