Greenhouse tomato dry matter production and distribution model under condition of irrigation based on product of thermal effectiveness and photosynthesis active radiation

Abstract: To know the applicability of dry matter production and distribution model in greenhouse environment in northwest of China, we conducted a tomato deficit irrigation experiment in 2013-2015 in Yangling Shaanxi Province. Four treatments were set up including no deficit in whole growth period, deficit of 50% only in seedling stage, deficit of 50% both in seedling stage and flowering stage and deficit of 50% in whole growth period. We analyzed the dynamic changes of tomato stems, leaves, fruits and roots under different irrigation treatment in 2013-2014, and established a dry matter production and distribution model by using water consumption, aboveground and root distribution index, aboveground organ allocation index. Then the experimental data in 2014-2015 was used to validate the dry matter production and distribution. Total radiation, temperature, and water consumption of tomato under different treatments and dry matter weight of tomato including stems, leaves, fruits and roots in different growth stages were observed. Meteorological data was measured by artificial weather station, and water consumption was calculated based on water balance theory, and dry matter weight of each organ was measured by weighing method. The results showed that the total cumulative of thermal effectiveness and PAR (TEP) and water condition influenced tomato's dry matter most. For full irrigation treatment, dry matter increased rapidly in seedling stage and flowering stage. In mature stage the increase rate of dry matter reduced to the minimum level, and the total amount of dry matter increased to the maximum level. Water deficit in seedling stage would not significantly reduce the total amount of dry matter. Water deficit both in seedling stage and flowering stage would significantly reduce the total amount of dry matter in mature stage, and longer durations would result in larger reduction. The process of dry matter production under different water condition could be simulated by using total cumulative of TEP as an input variable in a dry matter production and distribution model. The dry matter allocation index of aboveground and root only changes with TEP while irrigation amount influenced it little. The aboveground index increased with TEP, and reached minimum in establishment stage, i.e.0.79, reached maximum in mature stage, i.e.0.95. While the root index decreased with TEP, and reached maximum in establishment stage, i.e. 0.21, reached minimum in mature stage, i.e. 0.05. Before flowering, tomato only underwent vegetative growth, distribution indexes of stem and leaf were 0.24-0.26 and 0.74-0.76, respectively in establishment stage. Distribution indexes of stem and leaf became closer in later vegetative growth stage, and were 0.49-0.51 and 0.49-0.51 respectively in the end of seedling stage. The distribution index of fruit increased with TEP after flowering. A high precision could be attained when using this dry matter production and distribution model to calculate tomato's stem, leave, fruit and root dry matter under different water condition, and absolute errors were 0.24-9.46 g per plant, root mean square errors were 0.35-10.01 g per plant, and coefficients of determination were 0.78-0.89. This model could be used to simulate production and distribution of tomato's dry matter under different water condition when fertilizer supply was sufficient. This research provides useful information for greenhouse tomato production under different water conditions.