Quantitative response of greenhouse tomato yield and quality to water deficit at different growth stages
Deficit irrigation is widely used in tomato production because of water shortage. Many studies indicate that tomato yield is reduced but the fruit quality is improved under certain degree of water deficit. In order to investigate the quantitative relationship between tomato yield, fruit quality and water deficit, two experiments with different irrigation treatments were conducted in solar greenhouse in an arid region of northwest China from winter in 2008 to spring in 2009 (2008–2009 season) and from winter in 2009 to spring in 2010 (2009–2010 season). Results showed that the application of 1/3 (T1) and 2/3 (T2) of full irrigation at seedling stage (Stage I) did not significantly influence greenhouse tomato water consumption, total yield and fruit quality. Tomato water consumption and total yield were decreased by the application of 1/3 (T3) of full irrigation at flowering and fruit development stage (Stage II), and 1/3 (T5) or 2/3 (T6) of full irrigation at fruit maturation stage (Stage III). But the fruit contents of total soluble solids (TSS), reducing sugars (RS), organic acids (OA) and vitamin C (VC) as well as fruit firmness (Fn), sugar/acid content ratio (SAR), color index (CI) and water use efficiency (WUE) were significantly increased. However, no significant effects were found on tomato yield and fruit quality in the application of 2/3 full irrigation at Stage II (T4). The relative yield (Y/YCK) had a significant positive correlation with relative seasonal evapotranspiration (ET/ETCK), while negative correlations were found between the relative values of fruit quality parameters and ET/ETCK. Tomato yield is sensitive to water deficit during Stage II and Stage III, but fruit quality is mainly affected by water stress during Stage III. The regression equations between tomato yield, fruit quality parameters and ET could provide important basis for making irrigation strategies with the compromise between tomato yield and fruit quality
