Controlled-release nitrogen fertilizer improved citrus production and reduced several types of nitrogen losses in a two-year study conducted in China. The findings offer insights for citrus growers interested in improving fertilizer efficiency.
Researchers compared three enhanced-efficiency urea fertilizers with conventional urea in a citrus orchard in Yanting County, Sichuan Province, in southwestern China. The fertilizers included polyurethane-coated urea (PCU), humic acid urea and urea containing a urease inhibitor.
PCU PERFORMED BEST
PCU performed best overall. Its coating controls how quickly nitrogen is released into the soil, potentially helping better match nutrient availability with tree demand. Over the two-year study, PCU reduced ammonia losses by 51.1% and nitric oxide emissions by 36.3% compared with conventional urea. It also reduced nitrogen losses in surface water runoff, including a 25.5% reduction in nitrate losses.
The PCU fertilizer increased fruit yield and improved certain fruit-quality measurements, including vitamin C content and the sugar-to-acid ratio. Yield and quality improvements were significant in the second year, but not the first. PCU did not significantly reduce total nitrous oxide emissions.
The other two fertilizer treatments produced less favorable results. Humic acid urea increased nitrous oxide emissions by 16.1% without providing comparable environmental benefits. The urease inhibitor treatment reduced some nitrogen losses but did not consistently reduce ammonia or nitrous oxide losses.
APPLICABLE FOR FLORIDA?
For Florida citrus growers, the findings are worth watching. Nitrogen leaching is an important concern in the state’s sandy soils, where heavy rainfall and irrigation can move nutrients below the root zone. Controlled-release fertilizers could offer another way to improve nitrogen-use efficiency.
However, the Chinese experiment measured nitrogen losses through surface runoff, not nitrate leaching through Florida’s sandy soil profile. Differences in soils, rainfall and production practices mean the results should not be treated as a fertilizer recommendation for Florida. Field trials under Florida growing conditions would be needed to determine whether PCU provides similar benefits.
GET MORE DETAILS
The research, published Nov. 1 in Agriculture, Ecosystems & Environment, was conducted by Jing Zheng, Hongyu Lin, Xingling Wang, Hongyang Dong, Bowen Zhang and Minghua Zhou, all with the Chinese Academy of Science; Hui Cheng with Henan Xinlianxin Chemicals Group Co.; Shouzheng Jiang with Sichuan University; and Ralf Kiese and Klaus Butterbach-Bahl with Karlsruhe Institute of Technology in Germany.
Read the full research report: Effects of different urea-based fertilizers on gaseous and hydrological nitrogen losses from subtropical citrus orchards.
Share this Post