Physiological activity and material production in processing tomato under continuous cropping

Processing tomato production is the main business of the "red industry" in Xinjiang Uygur Autonomous Region. But with regional distribution and industrial development and the resulting in continuous cropping obstacle, the sustainable development of local processing tomato production has been severely restricted. A field experiment was conducted in 2013 in the Experimental Station of Shihezi Agricultural University to study the effects of continuous cropping on physiological activity and material production of processing tomato plant using the 'Ligeer 87-5' tomato variety. In the experiment, three treatments of continuous cropping (3 years, 5 years and 7 years) of processing tomato were set up. In addition, the first-planting of processing tomato was used as the control. The results showed that continuous cropping obstacles appeared in the whole growth period of tomato after 3 years of continuous cropping. The problems significantly increased with increased years of continuous cropping. Peroxidase activity initially increased and later decreased with increasing years of continuous cropping. While catalase activity, superoxide dismutase activity and root activity steadily decreased, malondialdehyde content increased significantly with increasing years of continuous cropping. The effects of continuous cropping on both antioxidant enzymes activities and malonidaldehyde content were greater on tomato roots than on leaves. Tomato dry matter production decreased with increasing years of continuous cropping. Dry weight was significantly lower in the 7-year continuous cropping treatment than in the control treatment. Continuous cropping reduced translocation of storage materials, rate of transfer and rate of contribution respectively by 57.3%, 21% and 35.6%. At flowering and fruit development stages, dry matter production decreased with increasing years of continuous cropping, eventually reducing tomato yield. 3, 5 and 7 years of continuous cropping reduced tomato yield respectively by 9.4%, 15.6% and 33.9%. Root-to-shoot ratio of tomato had a direct impact on yield and had significant quadratic correlation (R² = 0.973 5) with tomato yield. The results showed that continuous cropping damaged protective enzyme system and pre-burned tissues and organs of processing tomato. This eventually led to imbalances in plant sink-source relation as one of the main factors for the decline in tomato yield. Thus high yield could be realized by using crop rotation, which could improve the quality of the soil environment, control LAI of population at maturity stage, improve reasonable tomato root-to-shoot ratio.