The effects of liquid dairy manure application on herbage yield and quality of an established alfalfa (Medicago sativa L.) stand
Liquid manure is a nutrient rich byproduct of dairy cattle farming systems but its use for alfalfa ('Medicago sativa' L.) crop production has not been a standard practice. The objectives of this project were to determine the effect of liquid dairy manure and a number of associated application factors on the herbage yield and quality of alfalfa. A two year study was conducted at the Elora Research Station Ontario, Canada to compare effects between- and within-season of traffic, aeration, and three manure application rates (27, 41, and 55 kL ha-1) after first and/or second harvest in 2006 and 2007. Within each application time, a split plot with a restricted randomization design and three replications was used; individual plots were 30 m2 in size. Over the two seasons, the manure application increased herbage yields an average of 8.5%. Two in-season applications of 55 kL ha-1 manure (after first and second alfalfa harvest) resulted in significant (P=0.05) increases in third harvest yields of 42% and 32% for 2006 and 2007 respectively. Manure applied with aeration consistently resulted in significant (P=0.05) yield increases in both years, but were lower than when the manure was applied without the aeration treatment. There were no significant reductions in CP, NPN, or alteration in fibre content (NDF) detected. This study revealed that application of liquid manure to alfalfa after first and second harvest could be integrated into an alfalfa production system with no negative consequences to yield or forage quality. However, additional studies with other manure types, other soil types and soil conditions, and nitrogen cycling dynamics will be required to extend this finding to other field settings.