Quantifying The Effects Of Water And Nitrogen Coupling On The Growth Of Standard Cut Chrysanthemum 'Jinba' In Solar Greenhouse

Dry matter production and dry matter partitioning is the base of external quality formation of ornamental plants. Water and nitrogen are the important factors affecting dry matter production and dry matter partitioning of plants. The aim of this study is to quantitatively investigate the effects of water and nitrogen coupling on the growth of solar greenhouse standard cut chrysanthemum in solar greenhouse. Experiments of standard cut chrysanthemum (Chrysanthemum morifolium'Jinba') with different planting dates and different levels of water levels and nitrogen application rates were conducted in a solar greenhouse in Beijing during August,2006 and July,2008. The integrated photo-thermal index (PTI), defined as the daily average normalized thermal time multiplies by the daily total PAR intercepted, was used to describe the changes of leaf area index (LAI), the maximum leaf gross photosynthetic rate (Pg.max) and the partitioning indices of leaf, stem and flower with development stages. Also the way of water and nitrogen coupling and coefficients of water and nitrogen coupling were confirmed. Effects of the soil water potential, accumulated leaf nitrogen content, water and nitrogen coupling on the dynamics of the maximum leaf gross photosynthetic rate, canopy LAI and the partitioning indices of leaf, stem and flower were respectively quantified based on experimental data. Based on these quantitative relationships, models for predicting the effects of water, nitrogen, water and nitrogen coupling on dry matter production and partitioning of standard cut chrysanthemum in solar greenhouse were developed. Independent experimental data were used to validate the model. The results showed that the model developed in this study can predict canopy LAI, total dry weight, dry weight of stem, leaf and flower of the standard cut chrysanthemum plants grown in the solar greenhouse satisfactorily, hence, can be used for optimization water and nitrogen management for solar greenhouse standard cut chrysanthemum production.(1) Quantifying the effects of soil water potential on the growth of standard cut Chrysanthemum 'Jinba' in solar greenhouse.The aim of the study was to quantitatively investigate the effects of water on canopy LAI,Pg,max and dry matter partitioning of solar greenhouse standard cut chrysanthemum. The results showed that canopy LAI, Pg,max and dry matter partitioning indices kept at more or less the same level when soil water potential was equal or above -20kPa, but decreased linearly with the decrease of soil water potential when soil water potential was below -20kPa. So the critical soil water potential for the growth of standard cut chrysanthemum crops was determined as-20 kPa.With PTI as the predicting index, a model for predicting the effects of soil water potential on the growth of standard cut chrysanthemum in solar greenhouse was developed. Integrated with the crop growth model, the model predicted dry matter production and different organs dry weight. Independent experimental data were used to validate the model. The model developed gives satisfactory predictions of canopy LAI, dry matter production and different organs dry weight of standard cut chrysanthemum The result showed that the coefficient of determination (r2) between the predicted and measured values of LAI, dry matter production, dry weight of shoot, leaf, stem, flower based on the 1:1 line were 0.91, 0.84,0.85,0.85,0.86,0.83, respectively; and the relative root mean squared error (rRMSE) between the predicted and the measured values were 0.25,0.32,0.29,0.29,0.28,0.16.(2) Quantifying the effects of nitrogen on the growth of standard cut Chrysanthemum 'Jinba' in solar greenhouse. The aim of the study was to quantitatively investigate the effects of nitrogen on canopy LAI, Pg;max and dry matter partitioning of solar greenhouse standard cut chrysanthemum. The results showed that canopy LAI and dry matter partitioning indices kept at more or less the same level when the accumulated leaf nitrogen content at flower initiation stage was equal or above 1.70 g m-2, but decreased linearly with the decrease of the maximum leaf nitrogen content when the accumulated leaf nitrogen content was below 1.70 g m-2. The leaf gross photosynthetic rate increased with the increase of the accumulated leaf nitrogen content and their relationship was exponential. So the critical the accumulated leaf nitrogen content at flower initiation stage for the growth of standard cut chrysanthemum crops was determined as 1.70 g m-2.With PTI as the predicting index, a model for predicting the effects of nitrogen on the growth of standard cut chrysanthemum in solar greenhouse was developed. Integrated with the crop growth model, the model predicted dry matter production and different organs dry weight. Independent experimental data were used to validate the model. The model developed gives satisfactory predictions of canopy LAI, dry matter production and different organs dry weight of standard cut chrysanthemum. The result showed that the coefficient of determination (r) between the predicted and measured values of canopy LAI, dry matter production, dry weight of shoot, leaf, stem, flower based on the 1:1 line were 0.92,0.89, 0.90,0.88,0.85,0.89, respectively; and the relative root mean squared error (rRMSE) between the predicted and the measured values were 0.21,0.26,0.26,0.25,0.25,0.06.(3) Quantifying the effects of water and nitrogen coupling on the growth of standard cut Chrysanthemum 'Jinba' in solar greenhouse. Based on quantificationally analysis of the effects of water, nitrogen on the growth of standard cut Chrysanthemum 'Jinba' in solar greenhouse, the way of water and nitrogen coupling and coefficients of water and nitrogen coupling were confirmed. Water limit factors, nitrogen limit factors and coefficients of water and nitrogen coupling were multiplied as the way of water and nitrogen coupling. When coefficient of water and nitrogen coupling was above 1, the change of the parameter was positive with soil water potential or leaf nitrogen content. The larger of the coefficient of water and nitrogen coupling of the parameter, the stronger of the effect of water and nitrogen coupling was shown on the parameter, such as the leaf partitioning index on harvesting date, the increasing rate of shoot partitioning index. When coefficient of water and nitrogen coupling was below 1, the change of the parameter was negative with soil water potential or leaf nitrogen content. The smaller of the coefficient of water and nitrogen coupling of the parameter, the stronger of the effect of water and nitrogen coupling was shown on the parameter, such as the stem partitioning index on harvesting date, the increasing rate of leaf partitioning index.With PTI as the predicting index, a model for predicting the effects of water and nitrogen coupling on the growth of standard cut chrysanthemum in solar greenhouse was developed. Integrated with the crop growth model, the model predicted dry matter production and different organs dry weight. Independent experimental data were used to validate the model. The model developed gives satisfactory predictions of LAI, dry matter production and different organs dry weight of standard cut chrysanthemum. The result showed that the coefficient of determination (r2) between the predicted and measured values of LAI, dry matter production, dry weight of shoot, leaf, stem, flower based on the 1:1 line were 0.89, 0.84,0.83,0.84,0.82,0.85, respectively; and the relative root mean squared error (rRMSE) between the predicted and the measured values were 0.33,0.34,0.31,0.30,0.32,0.10.In this study, the model was developed for predicting canopy leaf area index, dry matter production and different organs dry weight by inputting the data of planting date, planting density, the date when the canopy of the crop was closed, the start date of short day, soil water potential, accumulated leaf nitrogen content, air temperature and PAR in the greenhouse. The model can be used for optimizing water and nitrogen management for standard cut Chrysanthemum 'Shenma' in solar greenhouse.