Assessing the Impact of Mixing Acid Whey With Dairy Manure On pH and Nitrogen Dynamics During Manure Handling

PurposeMixing of acid whey and dairy manure prior to land application could be a sustainable option for its application as plant nutrient source, without negatively impacting soil properties.MethodsLaboratory incubation experiments were conducted to test the effect of mixing acid whey and manure (1:1, 1:4 and 1:8 ratios) in simulated storage, on pH, ammonia volatilization, and carbon mineralization. Further, effect of application rate of a 1:8 acid whey:manure mixture (at 0, 94, 187, 374 kL/ha) on soil pH, NH3 volatilization, carbon and nitrogen mineralization was tested using seven different soil types.ResultsMixing acid whey into manure initially decreased the mixture pH (by 1.4-3.0 pH units) followed by an increase in mixture pH. Consistent with the pH swing, adding acid whey to manure decreased cumulative ammonia volatilization by 44-67% compared to manure only. Application of this mixture initially increased the soil pH in all soil types, but pH returned to control levels within 21 days for Honeoye, Lima, Howard, Volusia and Rhinebeck, and within 56 days for the Barbour soil type. Acid whey and manure mixture application increased ammonia volatilization losses from calcareous soils with initial pH> 7.0 (Honeoye and Lima) but had mixed effects in other soil types.ConclusionsMixing of acid whey with manure in storage can reduce ammonia volatilization. Land application of the acid whey: manure mixture increases net nitrogen mineralization without causing long-term soils acidification but a high pH swing after application suggests the need for a 1-2 week delay in planting in calcareous soils. The whey: manure mixture ratio of 1:8 was preferred due to whey and manure availability and significant reduction in NH3 volatilization.

Automated summary

Mixing acid whey with manure in storage can be a sustainable option for land application as a plant nutrient source without negatively impacting soil properties.