Drought is the most important factor limiting plant establishment, growth and
distribution in many regions of the world. The loess hilly region is a typical semi-arid and
arid region in northwest of China. The harsh environments and long-term anthropogenic
disturbance had resulted in severe soil erosion and water loss, vegetation degradation and
fragile ecosystems. Due to economic and technique problems, fertilizer and soil water are
applied excessively in vegetable field. Therefore, The research on responses of vegetable in
greenhouse to water and fertilizer deficit conditions and their eco-physiological adaptation
strategies to drought environment in the loess hilly regions could provide insights into the
improvement of the soil water and fertilizer management, improved vegetable quality and
yield.and therefore, are of great theoretical and practical significance.
In this paper, tomato (Lycopersicon esculentum) which is plant widespread in the
Loess hilly region in greenhouse was chosen as experimental material to study the effects
of water and fertilizer on fruit quality，yield and enenzy activity in fruit and leaves. Using
the method of manual control experiments, a total of six treatments with three soil moisture
levels: water deficit (Wl, 55%±5% of soil holding capacity), moderate irrigation (Wm,
75%±5% of soil holding capacity ), high irrigation (Wh, 95%±5% of soil holding capacity)
and two levels of fertilizer application: deficit fertilizer (Fl, 420Kg·hm-2 N+294 Kg·hm-2
P2O5+ 504 Kg·hm-2 K2O) ,and moderate fertilizer (Fm, 600Kg·hm-2 N+420 Kg·hm-2
P2O5+718 Kg·hm-2 K2O) were established. The following results were obtained.
（1）The vegetables adaptation in Yangling is better than that in Yan'an and Yulin. The temperature in December and January can not meet the cucumber, tomatoes fruit vegetable
normal growth and development needs in Yan'an and Yulin. Therefore, this period should
be mainly based on improving the greenhouse temperature. Some measures such as
covering straw mat at night, wiping the dust on the films and other insulation measures can
be taken to increase the temperature of greenhouse. Since leafy vegetables can grow at
lower temperature and accumulated temperature and have higher adaptability, therefore
these areas which have relatively poor heating conditions can plant leafy vegetables to
meet the needs of people in winter.
（2）Soil moisture content was mainly affect by irrigation, not by nitrogen level. The
soil water content in surface changed significantly. With the deeper of soil, the changing
magnitude of soil water content decreased. Irrigation mainly effected soil water content in
0-40 cm soil deepth. In the same fertilizer conditions, soil respiration increased with soil
irrigation increased. In the same irrigation conditions, soil microbial activity and soil
respiration were inhibited with the amount of nitrogen reduction. The impact of different
water and fertilizer on soil pH and was similar to EC. The change of pH and EC is less on
the vertical direction, but greater on the horizontal direction. Increasing fertilizer can
increase the soil conductivity. In the the same amount of fertilizer, soil electrical
conductivity decreased with the increase of irrigation. The soil temperature have a
significant positive correlation with air temperature under different soil water and fertilizer
treatment in different soil depths，and there had a significant negative correlation between
soil moisture and soil temperature. With the increase in soil depth, the lag of soil
temperature became larger.
（3）Different water and fertilizer treatments had significant effects on tomato yield.
Tomato production increased with the increase of water amount, but fruit quality and water
use efficiency decreased. Tomato yield increased with the increase of fertilizer amount.
Tomato fruit quality had significant positive correlation with drought. Deficit irrigation
improved fruit quality. However, excessive irrigation decreased the Vc content of fruit. In
the same fertilizer conditions, the Vc content in tomato fruit increased with reduction of
irrigation amount; In the same water levels, the content of soluble sugars, organic acids
decreased.with the increase in the amount of fertilizer.
（4）Under water deficit, SOD, POD, CAT and APX activity rised in tomato.The CAT activity and SOD activity was higher in deficit irrigation, while the POD and APX
activity was higher in moderate deficit irrigation. Moderate amount of nitrogen fertilizer
can increase the activity of antioxidant enzymes in leaves. Fertilizer levels had not
significantly affect on POD, APX activity in the leaves, but had significantly affect on
SOD, CAT activity；Fertilizer levels had significantly effect on SOD, POD, CAT, APX
activity in fruits. The APX in fruit maintained a high level, to protect the fruit against
oxidative damage, while the SOD, POD, CAT activity was lower. Fruit quality has a
significant positive correlation with antioxidant enzyme activity. Deficit irrigation
improved fruit quality, but also increased the concentration of free oxygen.
Therefore, different fertilizer and irrigation had significant effects on fruit quality,
antioxidant systems and the soil environment of tomato in the greenhouse. Under high
irrigation, the lag effect of soil temperaturet increased with the increase amount of fertilizer.
Under deficit irrigation, the lag effect of soil temperature decreased the increase amount of
fertilizer. The changes of pH and EC were small in the vertical direction while large in the
horizontal direction. Under drought stress conditions fruit plants resist drought stress by
decreasing the content of fruit moisture, increasing soluble sugars, organic acids, soluble
proteins and other macromolecules to increase the permeability, and enhancing antioxidant
enzyme activity. Tomato fruit increasing the non-enzymatic antioxidants and antioxidant
enzymes activity together to protect tomato from drought stress. Therefore, from the point
of increasing in tomato yield and quality, reducing the free oxygen ion concentration,
improving water use efficiency view, the treatment 75±5% of soil holding capacity and
600Kg·hm-2 N+420 Kg·hm-2 P2O5+718 Kg·hm-2 K2O is the optimal combination.
Key Words: Greenhouse tomato；Irrigation and fertilization level; Soil temperature; Fruit
quality; Antioxidant enzymes