Response of saffron (Crocus sativus L.) to irrigation water salinity, irrigation regime and planting method: Physiological growth and gas exchange

Abstract

Salinity stress reduces the crop water up-take which causes reduction in growth rate and productivity. Split-split plot arrangement was used to analyze the effects of irrigation water salinity (0.45 (well water, S1), 1.0 (S2), 2.0 (S3), 3.0 (S4) dS m−1), irrigation water levels (100% (I1). 75% (I2) and 50% (I3) of saffron water requirement (WR)) and planting methods (basin (P1) and in-furrow (P2) planting) on physiological growth and gas exchange of saffron (Crocus sativus L.) in open field conditions in two growing seasons. Saffron leaf dry matter (LDM) increased 59.6%, on average, in all treatments in the second growing season compared with that obtained in the first growing season due to corm growth in the second year. The main effects of irrigation regime on corm yield reduction was significant only in 50% WR (as19.1%) and in high salinity level (3.0 dS m−1 as 33.3%) in both years. Results indicated that salinity levels of 2.0 and 3.0 dS m−1 decreased the corm density 14.6% and 23.3% in the first growing season. In-furrow planting method significantly increased LDM (57.1%), corm yield (50.4%), leaf area index (LAI) (48.8%), photosynthesis rate (An) (40.3%) and stomatal conductance (gs) (41.2%) in both growing seasons. The intercept of relationship between flower and corm yield and between flower and LDM showed that approximately 5887 kg ha−1 of corms and 380 kg ha−1 of LDM have not participated in flower production as threshold. High irrigation water salinity, 3.0 dS m−1, reduced LAImax 31.9% and 45.7% in the first and second growing season, respectively. Salinity level of 2.0 and 3.0 dS m−1 reduced the crop growth ratio (CGR) significantly in comparison with that obtained in 0.45 dS m−1. Results showed that 50% WR reduced An by 21.8% and 27.2% in comparison with that obtained in 100% WR in the first and second growing seasons, respectively. Also, salinity levels of 2.0 and 3.0 dS m−1 reduced An by 21.5% and 27.2% in comparison with that obtained in 0.45 dS m−1 in the first growing season and 21.4% and 36.6% in the second growing season, respectively. Therefore, the water stress effects of 75% WR and 50% WR were corresponding to salinity stress effects of 2.0 and 3.0 dS m−1 salinity level, respectively. The results showed that inappropriate field management and strategies (i.e. basin planting method) reduced the corm planting density and resulted in negative effects of deficit irrigation and saline water on corm yield, saffron physiological growth and gas exchange phenomena that can be compensated by in-furrow planting method.