Effects of seeding rate and fertilizer on photosynthetic characteristics and yield of spring Fagopyrum esculentum

【Objectives】Fagopyrum esculentum originated in China，and has the higher nutritional, medicinal and health care quality, and has been one of the most popular green functional foods in the 21th century. At present, Fagopyrum esculentum having lower yields is relatively scarce both in the domestic market and abroad exportation market. Thus, the objective of this study is to provide the best cultivation measures for Fagopyrum esculentum by investigating the effects of seeding rate and fertilizer on net photosynthetic rate, chlorophyll content and yield of a Fagopyrum esculentum cultivar, Xidahuaqiao, which is usually planted in spring. 【Methods】Xidahuaqiao was used to investigate the effects of seeding rate and fertilizer on net photosynthetic rate, chlorophyll content and yield by using the quadratic general rotary unitized design, and the seeding rate, nitrogen fertilizer, phosphate fertilizer and potash were defined as experimental factors. The field experiments were respectively conducted from March to June in 2012 and in 2013 at the Xiema experimental station of Southwest University located at Beibei city, Chongqing municipality, China. The field experiments were the randomized block design with three replications, and the individual plot had 10 m2 area with 2 m width 5 m length, and included 6 rows by spacing 33 cm, and surrounded by 3 guard rows. The reciprocal third functional leaf of three plants in the middle stripe was randomly selected to measure the net photosynthetic rate and chlorophyll content (SPAD) between am 9: 30 and 11: 30 at a sunny day of full-bloom stage by using photosynthetic apparatus LI-6400 XT and chlorophyll meter SPAD 502, respectively. Grain in each plot was harvested separately at the stage with 70%-80% mature grain, and then threshing, air drying and calculating yield. Data of each indicator were analyzed separately using Microsoft Excel 2003 and SPSS 19, and the contour map of interaction of two factors was drawn by Surfer 8. 【Results】The yield is significantly and positively correlated with the photosynthetic rate and chlorophyll content. The effects of the seeding rate and potassium level on yield are significant, and the yield has a trend experiencing increase to decrease with the increases of the seeding rate and potassium level. The effects of the seeding rate, the levels of nitrogen and potassium on net photosynthetic rate and chlorophyll content are significant, and the yield exhibits a trend from rising to declining with the increases of the seeding rates and nitrogen and/or potassium levels. The interaction between the nitrogen or potassium levels and the seeding rate have significant effects on the yield, and the interactions between the potassium level and the seeding rate as well as the interaction between the seeding rate and the nitrogen level have great effect on the net photosynthetic rate. The interactions between the seeding rate and the nitrogen level as well as the interactions between the nitrogen level and the phosphate level have significant effects on the chlorophyll content. The results of the multivariate quadratic analysis indicate that the generated regression models based on the levels of nitrogen, phosphate and potassium, the seeding rate and the yield, the net photosynthetic rate and the chlorophyll content can be used for forecasting production of Xidahuaqiao. The recommended cultivation conditions for Xidahuaqiao include 37.5 kg/ha for seeding rate, 17.25 kg/ha for nitrogen level, 46.8 kg/ha for P2O5 and 52.5 kg/ha for K2O, and the chlorophyll content (SPAD), net photosynthetic rate and yield are expected at 55.34, 16.46 mol/(m2s) and 1656.16 kg/ha, respectively. 【Conclusions】The seeding rate, nitrogen fertilizer, phosphate fertilizer, potash and their interactions have a certain influence on the yield, net photosynthetic rate and chlorophyll content (SPAD) of Xidahuaqiao. The yield is significantly and positively correlated with the photosynthetic rate and chlorophyll content. Based on this experiment，the cultivation conditions for Xidahuaqiao are recommended by 37.5 kg/ha for seeding rate, 17.25 kg/ha for nitrogen, 46.8 kg/ha for P2O5, 52.5 kg/ha for K2O, and the expected chlorophyll content (SPAD), net photosynthetic rate and yield are 55.34, 16.46 mol/(m2s) and 1656.16 kg/ha, respectively.