Automation of lettuce seedlings irrigation with sensors deployed in the substrate or at the atmosphere

Abstract

Seedling production is an important step in the lettuce production system. However, there is a tendency to apply excessive irrigation at this stage. The aim of this study was to test the use of the Simplified Irrigation Controller (SIC) under two conditions: first, with the sensor installed in the substrate (measuring the soil water tension) and second, in the atmosphere ("atmospheric" -responding to vapor demand in the atmosphere) to control the irrigation of lettuce seedlings. The performance of the SIC was evaluated by monitoring plant traits. The lettuce seeds of the Regina cultivar were sown in styrofoam trays with commercial organic substrate.Both experiments were conducted under greenhouse conditions and evaluated under different SIC activation tensions. Shoot fresh weight and dry weight, height, number of leaves, leaf length, leaf area, water use efficiency (WUE) (ratio between the dry mass of plant produced by the volume of water applied), chlorophyll content, stomatal conductance and chlorophyll a fluorescence were assessed. In the experiment with the substrate sensor, the tension of 11.5 kPa caused death in 94 % of the seedlings and was disregarded in the statistical analysis. All biometric and physiological traits evaluated decreased as the SIC tensions increased. Thus, tensions of 4.0 (substrate sensor) and 3.5 kPa (atmospheric sensor) showed greater potential for producing vigorous seedlings, with WUE average values of 1.86 and 1.37 g L -1 , respectively. Cultivation of lettuce seedlings proved viable under both conditions when the SIC was used, with the emergence of a number of practical advantages of the atmospheric sensor over the substrate one.

Water requirement and growth indicators of forest tree species seedlings produced with automated irrigation management

“…This device has been used in several field studies [ 17 ] and greenhouse studies [ 18 ], using different soils or substrates for plants. It is presented as an alternative in irrigation management [ 19 ] and has the advantage of being built with low cost materials [ 20 ]. Two actuators were used for each plant species studied, independently installed in two tubes with treatment corresponding to the highest flow rate (V4), totaling 6 actuators for the 3 experiments.…”

Growth of black pepper plantlets under different substrates and irrigation levels

“…Irrigation management was carried out automatically at 4 kPa through the installation of simplified irrigation controllers (Medici et al, 2010) in two reference plants which were grown in the BC substrate and were well-irrigated. The porous capsule used as an irrigation controller sensor was made from domestic water filter candles in such a way that the dimensions were reduced (Bezerra et al, 2019) so as to enable installation in the tubes. Thus, the plants' water requirement was taken into consideration when defining RIL, facilitating the establishment of the ILs tested.…”

Crescimento inicial de cultivares de Açaí com irrigação automatizada / Initial growth of Açaí cultivars with automated irrigation

“…Dias et al (2013) encontraram diferentes respostas de EUA em mudas de mamão de acordo com a tensão no substrato, sendo que para variedade "Tainung 01", a medida que se aumentou a tensão no substrato, houve também aumento da EUA, enquanto para a variedade "Sunrise Golden", houve maior EUA para tensão intermediária testada. Já Bezerra et al (2019), em trabalho com mudas de alface em diferentes épocas de crescimento, acharam valores de EUA diminuindo a medida que se aumentava a tensão no substrato. Valença et al (2018), também em trabalho com alface, concluiu que houve maior EUA para os valores intermediários de condição hídrica do substrato.…”