Assessment of cattle manure acidification effects on ammonia and GHG emissions and crop yield

Abstract

Manure acidification is recognized as one of best treatments available to reduce ammonia emission from manure.However, the potential to reduce the emissions of polluting gases, as well as the effects on crop yield have been poorly studied. Therefore, this study was conducted to evaluate the effect of acid treatment on NH3 and other GHG emissions from manure and assess the effects on plant nutrient utilization. The effect of manure acidification on gas emissions was investigated on laboratory scale at LUHS Animal Science Institute. The study was performed using 20 litre manure tanks, gas emissions were measured by the passive chamber method. Field trials were conducted to evaluate the effects of acidified slurry on crop yield, using slurry acidification techniques in-field. Both acidified and non-acidified cattle slurry was applied to barley and spring wheat. Control fields were fertilized with mineral fertilizers. Slurry was acidified with H2SO4 to target pH 6.0. Our study showed that the emission rate for non-acidified cattle manure was as follows: NH 3: 11.6, CH4: 1.33 and CO2: 251.9 mg/(m2/60s), respectively. Acidification of manure to pH7 has reduced NH3 emissions by 39.6% and CH4 emissions by 29.5%. Higher level of manure acidification (pH5) gave even better emission reduction results: by 75.6% for NH3, and even by 91.8% for CH4. Different results were found for CO 2 emission, which showed that the emission rate could be 22.2% higher with pH7, and 27.8% lower with pH5. Field trials have shown that acidification of slurry can have a positive effect on crop yield. For barley, acidified slurry resulted in 13.1% higher yield and 3.43% higher protein content in comparison with untreated slurry, and 14.1% higher yield and 9.15% higher protein content in comparison with mineral fertilization. Smaller differences were found in the spring wheat fields, where acidified slurry resulted in 3.7 and 4.9% higher yield compared to untreated slurry and mineral fertilization, respectively. In summary, it can be concluded that mild acidification of cattle manure and slurry can be a successful solution to help farmers reduce NH3, CO2 and CH4 emissions and at the same time improve the fertilization value of manure.