THE WAGENINGEN RHIZOLAB - A FACILITY TO STUDY SOIL-ROOT-SHOOT-ATMOSPHERE INTERACTIONS IN CROPS .1. DESCRIPTION OF MAIN FUNCTIONS

A research facility is described for the integrated study of soil-root -shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight belo w-ground compartments aligned along a corridor. A rain shelter automat ically covers the experimental area at the start of rainfall. Compartm ents are 125 cm x 125 cm and 200 cm deep. Each compartment has a separ ate drip irrigation system. Crop canopy photosynthesis, respiration, a nd transpiration can be measured simultaneously and continuously on fo ur out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiratio n, trace gases and oxygen are installed in spatial patterns in accorda nce with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution and soil atmosphere. Root ob servation tubes (minirhizotrons) are installed horizontally at depth i ntervals ranging from 5 cm (upper soil layers) to 25 cm (below 1 m). T he facility is at present in use to study growth and development of ve getation (crops) in relation to drought, nutrient status, soil-borne d iseases, and underground root competition. One important application i s the study of elevated CO2 concentration and climate change and the w ay they affect crops and their carbon economy. Growth and development of field grown vegetables and winter cover crops are also evaluated. T he common aspect of those studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect da tasets that may help to improve mechanistic crop growth simulation mod els that can address suboptimal growth conditions.