ARI REVIEW FOR 2016-2017

NATURAL RESOURCES AND ENVIRONMENT A key feature of recent Section activities is the expansion of studies to new topics related to climate change, the sustainable use of soil and water, precision agriculture and environmental issues in order to assist efforts for sustainable and viable agriculture. The research work of the Natural Resources and Environment Section concerned irrigation and fertilisation of crops, soil fertility, the application of new technologies in greenhouses, the use of treated waste water for irrigation, the use of renewable energy in agriculture and the valorisation of endemic and native species in commercial floriculture and landscaping. An important part of the above research work has been carried out within the framework of cooperation programmes funded by various agencies. PLANT NUTRITION AND SOILLESS CULTURE Nowadays, in the light of global warming and severe water shortage in the world, studies on the use of water sources of marginal quality and plant nutrition aspects are matters of great importance for precision agriculture. On the other hand, the issue of salt accumulation in soils or in soilless growing systems with recirculating nutrient solution, especially when the water source used is of poor quality, is critical and requires the implementation of efficient technologies and appropriate mathematical models. A parallel activity concerns the adaptation of irrigation management and plant nutrition schemes to the pressure exerted by climate change, particularly in the Mediterranean region. In this respect, two articles were published recently dealing with the reassessment of water requirements of major irrigated crops in Cyprus. There is also participation in two EU projects whose main objectives are to adapt farming to climate change and limited water resources and to study the comparative advantages of organic versus conventional farming along with other activities (e.g. Students in Research – MERA) organised by the Research Promotion Foundation (RPF). Simulating NaCl accumulation in a closed hydroponic crop of zucchini: impact on macronutrient uptake, growth, yield and photosynthesis Zucchini squash ( Cucurbita pepo L.) plants were grown in a closed-loop hydroponic system and supplied with nutrient solution (NS) containing NaCl at different concentrations (0.7, 3, 5, and 7 mM). The primary aim of the study was to define the relationship between the external and uptake concentrations (UC) of Na + and Cl − . A second objective was to determine the UC of macronutrients (i.e., N, P, K, Ca, and Mg) and to test whether they are influenced by the gradual increase of the root zone salinity due to progressive NaCl accumulation. Two experiments were conducted, of which one was used to parameterise an existing empirical model, while the second one was commissioned to test the validity of the determined model parameters. Both Cl − and Na + ions accumulated progressively in the root zone solution over time, showing a tendency to stabilize at final concentrations according to the corresponding NaCl treatment. The relationship between the Na + and Cl − concentrations in the root zone and the Na + /water or Cl − /water uptake ratios was exponential and the model parameters successfully fitted to data from crops cultivated in different growth seasons. This model may be used to monitor Na + and Cl − concentrations in the root environment of zucchini crops as relationships of the plant water consumption. The exposure of plants to NaCl affected the UC of N, K, Ca, and Mg, but the results for some nutrients were not consistent in both growth seasons. The measurements of plant growth characteristics (i.e., biomass, yield, fruit quality, and photosynthesis) revealed that water resources containing up to 3 mM NaCl do not cause unacceptable yield losses in zucchini crops grown in completely closed hydroponic systems. ( D. Neocleous, D. Savvas ) 51 Natural Resources and Environment