Nutrient and water use efficiency in screenhouse crops: a benchmarking approach

The extreme and unpredictable outside climate conditions and health and quality of life issues raised from the consumers, have led to a steady and gradual increase of screenhouses crops, especially in countries of the Mediterranean area. The screenhouse enclosure not only modifies the physical climate, by altering the radiative and convective heat transfer, but it also amplifies the interaction between crops and their microclimate. Furthermore, screening materials exclude insects that attack crops enabling an environmental friendly crop production. One of the critical constraints to higher crop productivity is the low efficiency of applied nutrients, especially N and P. The NUE is a function of (a) soil to supply adequate amount of N, and (b) ability of plant to acquire, transport in root and shoot, and remobilize to others parts of the plant. Inefficient nutrients use is a key factor pushing the cost of cultivation and pulling down the profitability in farming. Although there are several terms for expressing nitrogen use efficiency (agronomic efficiency, physiological efficiency, chemical efficiency, productivity), the present study applies the definition most commonly used by farmers and crop advisers i.e., the crop output per unit of nutrient input. Although the need for reliable indicators to monitor, measure and evaluate the real impact of proposed innovation on the environmental sustainability is evident, there is still a lack of indicators that farmers and water authorities can use to achieve their goals. Benchmarking tools and performance indicators can be efficiently used for this purpose. In the present study the nutrient and water use efficiency of a screenhouse pepper crop was analysed based in a benchmarking approach. The benchmarking has been done using as reference case a similar open field pepper cultivation. Results show that if farmers integrate and adopt in their production chain the available techniques and technologies, then the total efficiency of nutrients and water use can be significantly increased.