Study shows manure elevates nitrogen accumulation and loss

A study found that the overuse and misuse of nitrogen fertilization -- which includes the application of manures -- is causing a surplus of nitrogen to seep into the soil and down into ground water.

The three-year study was published in November 2015 in HortScience. The results found that application of manures slowed acidification but accelerated salinization of the fertile greenhouse soil, and did not significantly enhance the above-ground fresh biomass and biomass nitrogen in most of the vegetable seasons.

"Our study showed that enhanced accumulation of mobile nitrogen induced by excessive manure input could exceed the need of plant uptake but be subject to downward migration and leaching-dominated loss," the authors wrote.

The study was conducted by using greenhouse soil to rotationally plant cucumber, tomato and lettuce with and without manures. The scientists in the study watched the spatial/vertical and temporal dynamics of nitrate, extractable organic nitrogen, and total nitrogen in the soil and estimated the leaching-dominated nitrogen loss based on the nitrogen balance in the soil.

The conclusion of the study recommended that farmers re-evaluate their use of manures in high-input agricultural ecosystems and determine if the harm to the environment outweighs the economic benefits.