Comparison of vapour pressure deficit patterns during cucumber cultivation in a traditional high PE tunnel greenhouse and a tunnel greenhouse equipped with a heat accumulator

Plant productivity in protected cultivation is highly influenced by air temperature and humidity. The conditions relating to the moisture content of the air in protected plant cultivation are preferably defined by vapour pressure deficit (VPD), which describes the difference between the maximal and actual water vapour pressure (kPa). VPD is widely used as the parameter describing the climate conditions favourable for the development of fungal diseases and for highlighting conditions unfavourable for plant development. In protected cultivation, both the air temperature and the humidity are influenced by heating systems, and one such system is a heat accumulator, which may store the excessive heat produced during the day by converting the solar energy inside the plastic tunnel, and using it when plant heating is required. The tunnel equipped with a heat accumulator maintained an optimal level of humidity for a longer period, and significantly reduced the time of excessive air humidity. The longest time with an optimal VPD was recorded in August in a tunnel with an accumulator – 30.5% of total time vs. 22.3% of time for control tunnel. The highest difference of total time where the VPD was too low (below 0.2 kPa) was recorded in July – 12.4% of time in a tunnel with an accumulator vs. 39.1% of time for control tunnel. The highest difference of total time with an excessive VPD (over 1.4 kPa) was recorded in May – 12.1% of time in a tunnel with an accumulator vs. 17.9% of time for control tunnel. However, a situation beneficial for plant growth occurred every month during the investigated season

Morphological and Physiological Responses of Strawberry Plants to Water Stress

The most of previous studies have been focused on the effect of water stress on plant yielding. However, the conditions in which plants grow from the moment of planting might affect their morphology and physiological response. The aim of this study was to examine the effect of water deficiency on growth and plant physiological response of strawberry (Fragaria x ananassa Duch. cv. ‘Salut’) under greenhouse conditions. The plants were grown in plastic containers filled with peat substratum. Water stress was imposed by reducing the irrigation according to substratum moisture readings. Water stressed plants had the lowest values of water potential and showed strong decrease in gas exchange rate. Also, biomass and leaf area were the lowest in this group of plants. No differences in the length of root system were observed between control and water stressed plants. The lack of water in growing medium resulted also in a decrease of density and reduction of dimensions of stomata on plant leaves. These changes contribute to optimizing the use of assimilates and water use efficiency in periods when water availability is decreased

Estimating the substrate water status using capacitance measurements

The suitability of capacitance probes for measuring the actual variations in substrate water content in container-grown ornamental species (Lawson cypress) was examined. The probes were installed in the plant containers. Weighing measurement data on water loss was used to assess the actual changes in substrate water content (plant water use). In an additional test, an evaluation of temperature sensitivity of the capacitance probe was performed under laboratory conditions. The probe was placed in a container containing the growing medium (peat substrate) with a defined (stable) moisture content. The substrate temperature was modified and the changes in probe output were recorded. The experiment demonstrated the existence of the effect of temperature on the quality of soil moisture measurements conducted with the capacitance method. The accuracy of the results obtained from measurements with dielectric sensors in relation to the data obtained by means of weighing platforms depended largely on the temperature profile of the measured medium. It was demonstrated that temperature variations explained 99% of the observed differences in the results of moisture content measured with the capacitance method. Due to the fact that there is no possibility of developing universal factors (for different sensors and substrates) for correcting the influence of temperature, this relationship should be defined independently for a given type of crop and the measuring system available

An hourly reference evapotranspiration model as a tool for estimating plant water requirements

The usefulness of estimating hourly reference evapotranspiration for assessing the water requirements of plants over a 24-hour period was determined in the study. The values of hourly (ET0,h) and daily (ET0,d) evapotranspiration were calculated using the Penman-Monteith (PM) model. The daily ET0 was calculated automatically by the meteorological station, and the evapotranspiration values for individual hours were calculated using spreadsheet software. To verify the values of evapotranspiration calculated with these two approaches in relation to the actual water needs of grass, lysimetric measurements were performed. Additionally, substrate moisture content and temperature were measured using capacitance probes. The values of evapotranspiration estimated with the hourly PM model were higher than those determined with the daily model. An accuracy of the hourly model in relation to the data measured with a weighing lysimeter depended largely on the quality of the reproduction of meteorological parameters at the site of the crop. Observed underestimation of the actual daily evapotranspiration was presumably due to the use of air temperature values in the calculations (measured at a height of 2 m by the weather station). During strong solar radiation the air temperature was much lower than the temperature of the upper layer of the substrate in the weighing lysimeter. Reference evapotranspiration was recalculated by introducing into the hourly PM model the measured values of substrate temperature. After taking into consideration the higher temperatures, the calculated values of evapotranspiration increased, and the regression model took the form: y = 1.01x + 0.014 (R2 = 0.90), which proves the proportionality of the calculated and measured (actual water needs determined with the weighing lysimeter) data. Reliable data on the hourly variations in evapotranspiration over a 24-hour period can be a great tool for use in controlling the irrigation of plants grown in a limited volume of substrate

Ocena przydatnosci podloza kokosowego do bezglebowej uprawy truskawki [Fragaria x ananassa Duch.]

W jednorocznych badaniach określono możliwość zastosowania podłoża kokosowego w uprawie truskawki pod osłonami. Ocenie poddano właściwości fizyczne podłoża kokosowego i torfu oraz wpływ różnych poziomów nawożenia na wzrost i owocowanie roślin truskawki odmiany Elsanta. Wyniki doświadczenia wykazały, że właściwości fizyczne zarówno torfu, jak i kokosu są odpowiednie dla prawidłowego wzrostu truskawki. Generalnie większy i o lepszej jakości plon uzyskano z roślin rosnących na podłożu torfowym. Nie stwierdzono negatywnego skutku obniżenia dawki nawożeniowej na wzrost roślin i wielkość plonu uzyskanego w trakcie doświadczenia. Obserwacje te sugerują możliwość ograniczenia nawożenia roślin truskawki rosnących na podłożach bezglebowych, co może mieć istotne znaczenie dla obniżenia kosztów produkcji owoców i zmniejszenia zanieczyszczenia środowiska naturalnego.The possibility of using coco substrate in production of strawberry plants under greenhouse conditions and the effect of different fertilizer rates on growth and fruiting of these plants were examined in one year study. Obtained results showed that physical properties of peat and coco substrate were adequate for growth of strawberries. Plants grown in peat produced more fruits and their quality was better compared to these from coco substrate. The lack of negative effect of lower nutrient supply, suggests the possibility of reduction of rates of mineral fertilizers in soilless strawberry production systems, decrease of production costs and pollution of environment

Estimation of water consumption by strawberry plants cultivated under greenhouse conditions

The experiment was conducted during two seasons (2002, 2003) t o investigate water consumption by three strawberry cultivars (‘Elsanta’, ‘Elkat’, ‘Salut’) grown under greenhouse conditions. Strawberry plants were grown in pots filled with a peat substrate. The pots were placed on top of glass containers filled with a nutrient solution. Each pot was connected with the container below by two pieces of water absorbing material immersed in the nutrient solution. The amount of the nutrient solution taken up by the plants was recorded every day. The highest water consumption was recorded for ‘Elsanta’, and the lowest one for ‘Salut’ plants. Water use efficiency calculated as a ratio of the total amount of water consumed by the plant and the size of the fruit crop produced ( cm 3 H 2 O g - 1 of fruit) was similar for the cultivars ‘ Salut’ and ‘Elsanta’. The highest level of water consumption recorded for ‘Elsanta’ plants indicates that it was caused by the high production potential of this cultivar