The Influence of Vibration and Moisture Content on the Compactness of the Substrate in Nursery Container Cells Determined with a Multipenetrometer

Abstract

An important problem of container nurseries is ensuring equal and favorable growth conditions for cultivated plants. This can be achieved by ensuring the physical parameters of the substrate used to grow seedlings in individual cells of the container are similar. The nursery container is filled with a specially composed substrate through an automated line. Quickly controlling the parameters related to the quality of substrate filling presents a significant problem, as it requires the ongoing correction of the filling module settings (e.g., extending the vibration time or changing the vibration amplitude). To address this issue, it would be helpful to determine the compactness of the substrate, which can be easily measured using a penetrometer. This paper presents a prototype automated station, known as a multipenetrometer, designed for the simultaneous testing of compactness in 15 selected container cells. The prototype was put to the test at the Nursery Farm in Sukowo, where two types of polystyrene containers (V150—650/312/150 mm; 74 cells; and 0,148 cm3 cell volume and V300—650/312/180 mm; 53 cells; and 0.275 cm3 cell volume) were filled with peat–perlite substrate on the Urbinati Ypsilon automated line. This study investigated the influence of substrate moisture (two levels—70 and 75%) and vibration intensity (two levels—8 and 12 G) of the vibrating table on its compactness within the individual cells of the nursery container. The results indicated that with an increase in substrate moisture and vibration intensity, the compactness of the substrate increased, and the variation in compactness between individual cells decreased. Notably, the V300 containers, with a larger cell volume (265 cm3), experienced a higher level of change compared to the V150 containers (145 cm3). Despite the use of substrate compaction techniques based on the experience of line operators filling containers, the coefficient of variation between the compactness of the substrate in individual cells of the container remained at 30%. Based on the findings, it was confirmed that the optimal parameters for filling V150 and V300 containers with peat–perlite substrate on the Urbinati line, at a filling capacity of approximately 400 containers h−1, are a moisture content of around 75% and a maximum vibration intensity of 12 G.