An innovative lysimeter system for controlled climate studies

Banks of lysimeters coupled with an environment-control unit (ECU) were developed for iteratively testing controlled-release fertilisers. Ryegrass was fertilised with 200 kg N kg-1 (single initial application) and grown for three months under a climate emulating Taranaki, New Zealand in the lysimeter system. Drainage and monthly dry matter (DM) yield were measured whilst evapotranspiration (ET), temperature and relative humidity (RH) of the ryegrass growing space were recorded. The performance of the ECU was tested by comparing observed and setpoint values from the Taranaki modified climate model of temperature and RH. Observed values of leachate, ET and ryegrass DM yield were compared with estimated values derived from the modified climate model to analyse the performance of the lysimeter system. Temperature and RH were satisfactorily maintained over the experimental period. The root mean square error (RMSE) for total daily average temperature value was 2 degrees C day-1 which was higher than the maximum desirable limit of 1 degrees C day-1. However, the RMSE of total daily average RH was 4.45% day-1, within the maximum desirable range of 5% day-1. The observed drainage, ET and DM yield were significantly correlated with estimated values and the Pearson correlation coefficient were 0.97, 0.76 and 0.98 (P < 0.05), respectively. These observations showed that the newly developed climate-control lysimeter system can emulate a climate model satisfactorily. The performance of the ECU could be improved by increasing the cooling capacity of the chiller and installing individual RH columns for each lysimeter bank. (c) 2023 IAgrE. Published by Elsevier Ltd. All rights reserved.