Fulvic acid potassium and nutrient-controlled release paperbag enhance peach tree growth, nitrogen absorption and utilization

Objectives Fulvic acid and paper bag have been proved to be effective in reducing ammonia volatilization and improving the utilization rate of nitrogen. This project studied the combined effects of special paper-bag made for nutrient-controlled release and fulvic acid potassium on peach growth, ammonia volatilization, nitrogen absorption and utilization, in order to provide an alternative fertilization method in orchard.Methods Two-year-old Jingqing14 (wild peach, Amygdalus persica Linn.) seedlings were used as materials, two pot experiments were conducted separately using common urea and 15N urea as N resource, respectively. Two fertilizer treatments of chemical fertilizer (CF) and chemical fertilizer plus fulvic acid potassium (FA), and two kinds of fertilizer containing bag treatments using common nylon bag with 0.178 mm of hole size (NB), and paper-plastic bag with 0.2 mm of pores and 0.5 cm intervals (PB) were set up. Volatilized ammonia was gathered inside a static box and titrated with 0.005 mol/L H2SO4. The above-ground growth index of the peach tree was measured after new shoots stopped growing. The total root length, the total surface area, the root volume and the average diameter were analyzed by WinRHIZO root analysis system. The total nitrogen content was detected by the micro-kjeldahl method, and the 15N abundance was detected by MAT-251 mass spectrometer.Results 1)Compared with the NB/CF treatment, the ammonia volatilization cumulant of NB/CF+FA, PB/CF and PB/CF+FA treatments were significantly reduced by 14.4%, 54.3% and 63.1% respectively. The peak rate of ammonia volatilization was reduced, and the peak time was delayed. 2) Compared with NB/CF treatment, the nitrogen utilization rates and soil nitrogen residue rates were significantly increased by 33.6%, 100.5%, 157.9% and 8.6%, 30.0%, 39.8% respectively under the treatments of NB/CF+FA, PB/CF and PB/CF+FA. 3) Compared with NB/CF treatment, NB/CF+FA, PB/CF and PB/CF+FA treatments significantly promoted the growth and development of young peach trees. The total root length, total root surface area, total root volume and average diameter were improved significantly. The root activity were increased by 6.5%, 17.5% and 22.7% respectively. The raising of trunk straight stems was increased by 12.2%, 26.2% and 41.8%. The primary lateral branch lengths were increased by 16.2%, 35.1%, 53.6% and the primary lateral branch thickness were increased by 8.2%, 20.8%, 28.4%.Conclusions When mixed with a certain amount of fulvic acid potassium and loaded inside the specific made paper-plastic bags, the ammonia volatilization from the chemical fertilizer will be reduced significantly, and the root activity and the roots biomass will be increased, consequently, the soil nitrogen retention time, the shoot growth and tree vigor will be promoted.