Assessing Land Suitability To Sunflower (Helianthus annuus L.) Cultivation In Tuscany Using APSIM To Predict Yield Potential And Stability

Sunflower is a relevant oil crop in rainfed cropping systems of Mediterranean area. Indeed, its morphological and physio-logical traits make it suited to scarce and irregular rainfall conditions and high evapotranspiration of summer season. In Central Italy, conventional management allows achieving yields higher than 3.0 t ha-1, with a reasonable variability within genotypes. Due to the high oil content (45-52%) and fatty acid profile (traditional and high-oleic varieties), the seeds are of particular interest both for food and no-food industry, moreover the co-product from oil extraction is a protein meal/cake valuable for animal feeding. In Tuscany, sunflower is largely the most relevant oil seed crop, being cultivated on and average area of about 20.000 ha, whit an average yield during the last ten years, equal to 2.1 t ha-1 (ISTAT, reference period 2011-2021). The crop is distributed both on flat areas of the large coastal and river plains, as well in hilly areas, where it represents one of the few alternative options to durum wheat within the crop rotation. In Tuscany region the climate is characterised by a large interannual variability of weather conditions with frequent occurrences of spring frost, that usually takes place during April, and high temperatures and prolonged drought periods in the late spring and in summer. Rainfall distribution and crop evapotranspiration are strongly affected by the orography of the region. Moreover, the different soil texture gradients determine, under the same weather conditions, a strong variability in crop responses due to their effect on the soil-water-crop system. Properly representing the spatial pattern of sunflower response to weather and soil conditions would increase the knowledge level about land suitability to its cultivation, providing support for farmer choices and supply chain organization. Thus, during the period 2019-2021 the project "SIC-OLEAT - Crop Innovation Systems for Tuscany Oilseed Crops" project, funded by Tuscany Region (PSR 2014-2020), focused on the development of knowledge tools to support Tuscan farmers towards a sustainable production of oil crops. In particular, the objectives of this research, based on the application of APSIM simulation engine on a 42-year historical series of spatialized weather data, were the evaluation of the effect of meteorological conditions and soil characteristics on sunflower yield potential and their stability over time under not irrigated conditions, in order to deliver land suitability maps to sunflower cultivation in Tuscan agricultural areas.