The Effects of Deficit Irrigation Combined with Biochar Amendment on Growth and Physiological Traits of Greenhouse Tomato

Abstract

【Objective】 Deficit irrigation and biochar amendment have been increasingly used to increase irrigation water use efficiency and improve soil quality respectively. However, how their combination affects the growth and physiological traits of crops is an issue that is not well understood. The aim of this paper is to address this in an attempt to provide guidance to improve the management of greenhouse tomato production in northwest China. 【Method】 The experiment was conducted in a greenhouse. We compared three irrigation levels by keeping the soil water content at 75%~85% (I1), 55%~65% (I2) and 40%~50% of the field capacity respectively. Added to each irrigation treatment were three biochar application rates: no amendment (B0), added 3% (w/w) (B1), and 6% (B2) of biochar. In each treatment, we measured the growth and physiological traits of the crop, as well as its ultimate shoot dry matter and water use efficiency at different growth stages. 【Result】 A moderate deficit irrigation did not reduce the photosynthetic rate at critical growth stage, but significantly increased the activities of antioxidant enzymes (SOD, POD, CAT) in leaves and reduced the final shoot dry matter. Biochar amendment combined with full irrigation reduced photosynthesis and the open ratio of photosystem II (PSⅡ), thereby resulting in a significant decrease in shoot dry matter and water use efficiency (WUEL). Combination of deficit irrigation and B2 biochar amendment enhanced the opening of PSⅡ and heat dissipation capacity (NPQ) of the crop, thereby increasing the shoot dry matter and WUEL. Dry shoot matters were affected significantly by all physiological traits, especially antioxidant enzyme activities (POD and CAT), the net photosynthetic rate (Pn) and stomatal conductance (Gs), during the critical period when dry matter started to accumulate in the shoot. Improving the photosynthetic capacity of the leaves and defence capacity of the antioxidant system can promote dry matter accumulation. Compared with I2+B0, I2+B2 increased dry shoot matter and WUEL by 6.1% (P>0.05) and 30.9% (P<0.05), respectively. 【Conclusion】 I2+B2 was the optimal combination of irrigation and biochar amendment for greenhouse tomato in northwest China.

Keywords

• deficit irrigation
• biochar amendment
• photosynthetic traits
• antioxidant enzyme activity
• dry shoot matter
• wuel