PHYSICAL PROTECTION IN EXPERIMENTAL RASPBERRY PLANTATION

One of the biggest challenges of raspberry production in Hungary nowadays is the reduction of unfavourable effect of climate changes. The maturation phase of main varieties within the Carpathian Basin falls in a period of extremely high temperature reaching, or even exceeding, 35-40 °C and atmospheric drought. This detains the desirable fruit growth. In order to restore or even save the domestic raspberry production and market, introduction of greenhouse or polytunnel solutions is needed. Experimental plantations of three different raspberry varieties were set in two repetitions: covered and uncovered versions. Each cover has characteristic light reflection /absorption/ transmission which should generate devious environmental conditions and also different plant growth. Besides the monitoring of elementary biological indicators a wide range of sensors (temperature, humidity, solar irradiation, spectroradiometer) were used to quantify the difference between cover materials to find the optimal tunnel material for maximal plant productivity. РЕФЕРАТ Одним з найбільших викликів виробництва малини в Угорщині сьогодні є зменшення несприятливого впливу змін клімату. Фаза дозрівання основних сортів в межах Карпатського басейну потрапляє в період надзвичайно високих температур та посухи досягає, або навіть перевищує 35-40°С. Це затримує бажаний ріст плодів. Для того, щоб відновити або навіть зберегти виробництво малини, необхідно впроваджувати парникові або політунельні рішення, щодо її вирощування. Експериментальні плантації трьох різних сортів малини були встановлені в двох повторах: покриті і відкриті способи вирощування. Кожне покриття мало характерне відбиття /поглинання/ світла, яке повинне генерувати умови навколишнього середовища, а також різне зростання рослин. Крім моніторингу елементарних біологічних показників для кількісного визначення різниці між покривними матеріалами для пошуку оптимального тунельного матеріалу для максимальної продуктивності рослин використовувався широкий спектр датчиків (температура, вологість, сонячне опромінення, спектрорадіометр). INTRODUCTION At least 80% of the world's raspberry production is covered by leading raspberry producers located in Eastern Europe. Climate change scenarios generate serious threat on raspberry plantations throughout this region. Plant growth, yield and fruit quality are all affected by the increased number of high temperatures, atmospheric drought and sunburn (Figure 1). Fig. 1 – The symptoms of sunburn Vol. 57, No. 1 / 2019 116 Farmers regularly experience reduction in plant growth, leaf area, yield and fruit quality. Visual signs of heat stress, sunburn are often registered during the summer periods induced by excessive heat and direct radiation causing decreasing photosynthetic activity of plants. Dedicated plant breeding programs have been started to mitigate the effects of climate change (Dénes, 2016) but these programs need long time. Fighting alone by using biological ways is not enough. An immediate action is required to save the raspberry production. A physical protection against excessive direct radiation can be considered as the only way to restore the stability and quality of production on short term. Nevertheless, returning the site of raspberry production to the forests (where the species is originated from) or agroforestry systems (Nagy, 2017) can be also considered as a solution on middle and long term. Combining solar panels with agriculture (Hanley, 2017, Hajdú, 2018) in this particular place can offer an even more reasonable way to solve the question of excessive radiation. An accurately adjusted portion of radiation would be transferred to electricity while the rest can be used by the protected plantation below. In this case, the shading system would produce energy which would possibly offer a more sustainable way of fighting against the effects of climate change (Szalay K. et al., 2016) and energy scarcity. Beside the reduction of direct radiation various shading solutions and applied materials are expected to change the spectral characteristic of incident light and so the light utilisation of plants. In order to find a reasonable solution to protect the plants and increase the stability of the production a raspberry plantation with different varieties was established. A sun protective shade tunnel system was erected to create a test site at NARIC Fruitculture Research Institute (FRI), Fruit Culture Research and Development Institute of Fertőd, Hungary. It provides opportunity to measure and evaluate relevant biological and physical parameters playing an important role in berry production (Keller et al., 2018). An additional problem is plant protection. The climate change results in the migration of different pests like Drosophylla Suzukii (Figure 2) which threats the raspberry plantation and can cause 100% yield loss (Figure 3.). Protection against the pest is challenging especially in organic farms where chemical protection is limited. Within the frame of the project the effect of shade materials and possibility to use them against Drosophylla Suzukii was studied. Fig. 2 – Drosophylla suzukii Fig. 3 – Fruit damaged by Drosophylla suzukii Vol. 57, No. 1 / 2019 117 Modern remote sensing applications (Fenyvesi, 2008) such as portable spectroradiometers can widely be used both in field and under laboratory conditions. It is adequate to carry out independent, fast and precise evaluations in an economic way. ASD FieldSpec 3 MAX portable spectroradiometer (Csorba et al., 2014, Fekete et al., 2016) was used to evaluate the incident radiation within the polytunnels and the spectral response of the vegetation. The device extends the range of the detectable visible light (Lágymányosi and Szabó, 2009, Williams et al., 2010) to NIR (near infrared) and the SWIR (shortwave infrared) region and covers the range of 350 to 2500 nm (Szőke et al., 2011). The technology provides opportunity to reveal such differences in natural light conditions that are usually unmeasured by traditional weather stations and makes possible to study the correlation between light condition and plant growth in a more complex way. MATERIALS AND METHODS Field measurements were carried out in the control area and under two different types of tunnels. Data acquisition was made with ASD FieldSpec 3 MAX portable spectroradiometer. As a reference the full sky irradiation in the control plantation was measured without any cover material above (Figure 4). A reference panel was used as a standard surface that reflects 95% of all incident radiation. Using this etalon the light conditions between treatments (tunnels) could be compared. Fig. 4 – Tunnels with different cover materials and white reference measurement under open sky Following this, further measurements were carried out under black and white tunnels. Measurements were carried out in the range of 350 to 2500 nm. In parallel, with in situ meteorological sensors, temperature, humidity and global radiance (400-1100 nm) were measured with Almemo 2890-9 data logger (Figure 5). Fig. 5 – ASD FieldSpec3 MAX and Almemo 2890-9 data logger Beside the above described non-contact data acquisition contact measurements were also carried out. In order to compare the light utilization efficiency, the water and nitrogen management of plants under various circumstances PlantProbe was used to measure the reflectance characteristic of plant leafs within each treatments (Figure 6). Vol. 57, No. 1 / 2019 118 Fig. 6 – Contact reflectance measurement with PlantProbe From these spectra, photochemical reflectance index (PRI), water index (WBI) and normalizes nitrogen index (NDNI) were calculated with the following equations: