Effects of saving water and fertilizer conservation for potted Chinese rose using controlled-release compound fertilizers combined with water retention agent

Abstract: Water retaining agent (WRA) is a high-hydrophilic polymer which absorbs large amount of water, and is widely used in agriculture. WRA and fertilizer application of collocation is one of the important techniques of water and fertilizer management. In order to study the effects of WRA combined with different fertilizers on the water and fertilizer conservation capacity of soil, soil column and Chinese rose (Rosa chinensis Jacq.) pot experiments were conducted in our research. There were six treatments: common compound fertilizer without WRA (CCFW0), common compound fertilizer combined with 0.25‰ of soil weight WRA (CCFW1), common compound fertilizer combined with 0.5‰ of soil weight WRA (CCFW2), controlled-release compound fertilizer without WRA (CRCFW0), controlled-release compound fertilizer combined with 0.25‰ of soil weight WRA (CRCFW1), controlled release compound fertilizer combined with 0.5‰ of soil weight WRA (CRCFW2), and the soil water, nitrogen and potassium leaching loss rate and physiological characteristics of the rose were determined. Results showed that: (1) In the soil column experiment, compared with CCFW0 treatment, CCFW2 significantly (P<0.05) reduced the loss of water by 33.6%; CRCFW1 and CRCFW2 treatments significantly (P<0.05) reduced the loss of water by 50.8% and 51.7%, the leaching amount of nitrogen by 19.7% and 30.6%, respectively compared with CRCFW0 treatment. Compared with common compound fertilizer (CCF) treatment which combined application with equal dosage of WRA, the controlled-release compound fertilizer (CRCF) treatments significantly (P<0.05) reduced the leaching amount of nitrogen by 72.4% to 75.6%, and significantly (P<0.05) reduced the leaching amount of potassium by 81.5% to 84.2%. The leaching amount of nitrogen of CCF treatments showed no significant (P>0.05) difference, but the leaching amount of potassium was significantly (P<0.05) reduced by 11.6% to 26.3% as the application of WRA increased; (2) Compared with the treatments without WRA, CCF combined WRA showed no significant (P>0.05) difference on flowering phase and flower numbers, however, CRCF combined WRA significantly (P>0.05) increased the flower number, plant height and flower diameter by 12.5%, 7.9%-12.1% and 46.9%-53.1%, respectively. As such, the ornamental value of Chinese rose was increased. Compared with CCF treatments, the CRCF treatments which combined the same dosage of WRA significantly advanced flowering date of Chinese rose by 5-7 d, the period of flowering time was prolonged by 5-10 d, and the flower numbers were increased by 26.7%-41.2%, respectively, plant height, stem width, and leaves net photosynthetic rate of CRCF treatments were significantly (P<0.05) increased by 12.8%-36.0%, 5.4%-15.2%, and 18.2%-29.6%. With the same dosage of WRA, CRCF treatments increased SOD and POD activities by 12.6%-33.0% and 14.5%-31.1%, respectively. Compared with CCF, CRCF could decrease the optimum application of WRA, and fully exert the characteristics of water retaining and fertilizer conservation of WRA. Under the condition of this study, the CRCF combined 0.25‰ soil weight of WRA should be the optimum fertilization schedule.