Improvement of chickpea water productivity through plant biostimulant treatments under Mediterranean rainfed conditions

Introduction Global warming and drought events are becoming increasingly frequent, requiring optimized crop management strategies to improve water productivity and sustain crop performance. Plant biostimulants are considered a promising approach to mitigate the effects of water stress in rainfed cropping systems such as chickpea. Methods A three-year field experiment (20232025) was conducted in south Italy to evaluate the effects of different biostimulants on chickpea under contrasting agrometeorological conditions. Treatments consisted of the factorial combination of two genotypes, two nitrogen (N) fertilization rates (0 and 40 kg N ha⁻¹), and three plant biostimulants: two microbial formulations (PB1, a consortium of Azospirillum brasilense and Pantoea dispersa ; PB2, based on Bacillus subtilis ) and one non-microbial formulation (PB3, containing protein hydrolysates, humic acids, and micronutrients), compared with an untreated control. Agronomic, physiological, qualitative, and spectral traits were assessed in relation to seasonal water availability and temperature patterns. Results Marked seasonal variability was observed, with two growing seasons characterized by severe water stress occurring either before or after flowering, whereas the first season showed favorable water availability throughout the crop cycle. Biostimulant applications significantly increased grain yield and water use efficiency (+16 to +22%) compared with the untreated control. Grain quality traits, including protein and phenolic contents as well as storage globulin expression, were mainly affected by post-flowering temperature and rainfall conditions. Water deficit also influenced soil microbial persistence, resulting in greater variability in microbial survival under drought conditions. A negative relationship was observed between grain yield and the accumulation of 7S vicilin and 11S globulin proteins, whose expression was significantly modulated by spring temperatures. In addition, NDVI measurements showed strong correlations with grain yield (R² = 0.830.85; p ≤ 0.05), enabling the development of reliable flowering-stage yield prediction models. Discussion The results demonstrate that plant biostimulants can effectively improve chickpea water productivity under variable Mediterranean climatic conditions. Seasonal agrometeorological variability strongly influenced both crop performance and grain quality, highlighting the importance of integrating biostimulant-based strategies into sustainable crop management systems facing increasing drought risk.