Yield and economic profit synergism of controlled release urea and fulvic acid in rice–wheat rotation system

Objectives Controlled-release urea and fulvic acids have been proved to raise yield and fertilizer efficiencies in rice and wheat production. Their synergism was studied in this paper for further improving fertilizer use efficiency and grain yield.

Methods A field plot experiment was conducted in the rice wheat rotation system on paddy soil in Jinan, Shandong Province. The experiment treatments included no nitrogen fertilizer control (CK), common urea (U), controlled-release urea (CR-U), controlled-release urea plus fulvic acid (CR-U+F), and 40% less CR-U (60% CR-U) and 40% less CR-U+F (60% CR-U+F). At the seedling, jointing, grain-filling/heading, ripening stage of wheat and rice, plant and soil samples were collected to measure photosynthetic rate, soil nitrogen contents, soil pH, available P and K contents, and the yield.

Results Compared with U treatment, CR-U treatment increased rice yield by 10.5% and wheat yield by 9.8%, increased nitrogen utilization by 64.8% in rice and 42.0% in wheat, improved agronomic efficiency by 52.2% and 47.1%, and increased annual economic benefit by 2804 yuan/hm², respectively. Compared with CR-U treatment, CR-U+F treatment increased the yield and nitrogen use efficiency by 7.3% and 32.5% in rice, and 4.4% and 18.3% in wheat, respectively. 60% CR-U+F treatment improved wheat yield by 5.0% but no obvious effect on rice yield, compared with 60% CR-U treatment. CR-U+F treatment increased the annual net income by 2337 yuan/hm² than CR-U treatment; 60% CR-U+F treatment increased the income by 1823 yuan/hm² than 60% CR-U treatment, and increased net income by 547 yuan/hm² than U treatment.

Conclusions Controlled release nitrogen synchronizes N supply with crop nitrogen requirement, and significantly increases leaf photosynthetic rate during key growth stages of rice and wheat. Fulvic acid reduces crop transpiration rate and increases crop nutrient utilization efficiency. Controlled-release urea and fulvic acid synergistically increase the rice yield, nitrogen utilization efficiency and economic benefit, thus achieving high efficiency nutrient utilization.