The effect of substrates containing municipal sewage sludge compost on the accumulation of macrocomponents in Impatiens walleriana Hook.

Abstract

Municipal sewage sludge is often used in compost production for agriculture. Composting sediments, which include structure-forming materials, results in the formation of matter rich in organic substances and nutrients that can be used as a component of horticultural substrates, as an alternative to peat. The aim of this research paper is to assess the impact of substrates containing municipal sewage sludge compost on N tot. , P, K, Ca, Mg and S levels in the leaves and roots of Impatiens walleriana Hook. The two-year experiment used four types of compost; in the first year the tests were conducted after a 7-month period of decay and the second year after an 18-month period. The composition of compost material was as follows: compost I – 70% municipal sewage sludge, 30% rye straw; compost II – 70% municipal sewage sludge, 30% coniferous tree sawdust; compost III – 35% municipal sewage sludge, 35% potato pulp, 30% rye straw; compost IV – 35% municipal sewage sludge, 35% potato pulp, 30% coniferous tree sawdust. During the first and second year, five experimental sites were used: four substrate with 50% of the tested compost and 50% sphagnum peat and one sphagnum peat reference substrate with a 2.5 g dm -3 dose of Azofoska multipurpose fertiliser. After 12 weeks of Impatiens walleriana cultivation the recorded level of total nitrogen, calcium, magnesium and sulphur in the leaves was lower than the optimal range of the macrocomponent content recommended for this species. The levels of phosphorus and potassium were the exception. Impatiens cultivated in substrates with compost after a 7-month decay period contained 1.7 times more nitrogen and 1.8 times more potassium in the leaves; they had similar phosphorus and sulphur content and lower calcium and magnesium content than the plants cultivated in the compost substrates after an 18-month decay period. The roots of impatiens contained more calcium than the leaves in both years of the study. The nutrients supplied in the substrates and through top dressing fertilisation were not sufficient to achieve the best cultivation results for Impatiens walleriana.