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| DOI：10.13522/j.cnki.ggps.2020214 |
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| The Effect of Water-nitrogen Coupling on Water-nitrogen Production Functions of Greenhouse Tomato under Mulched Drip Irrigation |
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LI Wenling, SUN Xihuan, ZHANG Jianhua, MA Juanjuan, GUO Xianghong, LEI Tao, SUN Ruifeng, SONG Tao
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1.College of Water Resources Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China; 2. HKBU Institute for Research and Continuing Education, Shenzhen 518000, China
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| Abstract: |
| 【Background】Tomato is an important economic crop planted widely in both north and south of China. In addition to its effect in antioxidant and anti-cancer, tomato is also nutritious and rich in VC, lycopene and other nutrients. Water and nutrients are two abiotic factors determining tomato growth. Irrational irrigation and fertilization, especially when they are used excessively, not only waste resources and contaminate groundwater, but could also compromise crop yield and quality. Understanding how water and nutrients combine to modulate tomato growth is hence critical to its sustainable production.【Objective】The overall objective of this paper is to determine the production functions of water and nitrogen of greenhouse tomato in response to water-nitrogen coupling under mulched drip irrigation. We can therefore find its key water-demand stages and provide guidelines for efficient use of water and nitrogen fertilizer in tomato production.【Method】 The experiment considered four factors and three levels, with all designed using the orthogonal test to study how yield of the tomato responds to change in water and nitrogen coupling. The Jensen model was used to describe the change in tomato yield with water and nitrogen applications.【Result】The tomato yield calculated by the model was consistent with the measurements, with the squared sum of the model fitting residuals being 0.01 and the determination coefficient being 0.793. The root mean square error, average relative error and average absolute error between the calculated and the measured yield were 2.98 t/hm2, 2.53% and 2.39 t/hm2, respectively. The water sensitive index at each growth stage was ranked in the descending order as flowering stage (λ2=0.200) > seedling stage (λ1=0.096) > ripening stage (λ3=0.059). The water sensitive index calculated from the cumulative curve of the water sensitive index agreed well with the estimate from the Jensen model. The factors that impacted tomato yield was ranked in the following descending order based on their significance: irrigation at flowering stage>irrigation at seedling stage>nitrogen application>irrigation at maturity stage, with the effect of irrigation at flowering stage being significant (P<0.05). The highest yield was 72.92 t/hm2, achieved by triple irrigations coupled with 350 kg/hm2 of nitrogen application. The partial nitrogen production decreased as nitrogen application increased, and when the nitrogen application exceeded 250 kg/hm2, a further increase in its application did not result in a noticeable yield increase but reduced the water use efficiency. The water-nitrogen production function was accurate and can be used to predict yield of the tomato fertigated by film-mulched drip irrigation. The cumulative curve of the water sensitive index was adequate for calculating water sensitive index, with the water sensitive index at flowering stage being the highest.【Conclusion】Considering the yield and water and nitrogen use efficiency, the optimal fertigation under film-mulched drip irrigation was: sufficient irrigation at seedling stage, 75% of the sufficient irrigation at flowering stage and ripening stage respectively, coupled with 250 kg/hm2 of nitrogen application. |
| Key words: water-nitrogen coupling; tomato; yield; water-nitrogen production function |
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