Many questions are asked concerning the right time or the right crop to apply manure.
- Is there a difference in nitrogen (N) availability if it is applied in the spring or the fall?
- Is there a difference between crops with early season N demand vs. late season N demand?
To answer these questions a study was initiated at the NDSU Carrington Research Extension Center in 2008 and repeated in 2009 to determine the impact of fall vs. spring applied beef feedlot manure on hard red spring wheat yield and kernel protein.
Treatments included; fall applied manure, spring applied manure, spring applied urea N and a check with no N. In 2008, the treatments were applied in a no-till situation and in 2009 the treatments were incorporated with one pass tillage. The treatments were applied to supply 150 lb N/acre after crediting soil residual N. The manure treatments were applied assuming 50% of the total N would be available in the first crop year of application. The fall manure was applied in early-November both years. Spring manure and urea were applied in mid-April both years preceding planting. To decrease N volatilization under no-till in 2008, the urea was applied during a rain event 4 hours before planting. In 2009, the urea was incorporated at the same time as application.
What Did We Learn?
According to Figure 1, the spring applied urea and fall manure treatment had the highest yield. The spring applied manure was significantly less yielding than the urea treatment, but not the fall manure treatment.
As shown in Figure 2, the urea treatment also had the highest level of kernel protein percentage. The remaining three treatments were all statistically similar and significantly less than the urea treatment.
To provide an economic perspective, nitrogen prices were factored into this study. Area fertilizer dealers provided urea price quotes that equated to $0.45/lb of available nitrogen. An $0.11/lb value of manure nitrogen was determined from manure fertility analysis combined with the cost of hiring a custom manure operator to haul and apply the manure at the Carrington Research Extension Center. The nitrogen input costs were $67.50/ac for urea and $16.50/ac for manure treatments, respectively. Costs associated with urea application were not included since it is often combined with other field operations.
Gross income was determined by multiplying the price of a bushel of wheat (discounted for protein) by the yield for each treatment. By producing the most and highest quality wheat, the urea treatment grossed the highest at $273.60/ac for 48 bu/ac at $5.70/bu. Gross income on the fall-applied manure treatment was $243.00/ac for 45 bu/ac at $5.40/bu, and the spring-applied manure treatment grossed $198.00/ac for 40 bu/ac at $4.85/bu. The untreated check grossed $141.00/ac for 30 bu/ac at $4.80/bu.
Although the urea treatment grossed the most money the urea nitrogen bill was more than four times greater ($67.50/ac) than the manure treatments ($16.50/ac). Calculating the net return (market price less nitrogen costs) on the use of the fertilizer shows fall-applied manure ($226.50/ac) netted the most with traditional urea ($206.10/ac) second, followed by spring-applied manure ($181.50/ac). The untreated check ($141.00/ac) was last (Figure 3).
After two years with different weather conditions, wheat response to manure assuming 50% availability was not as favorable as urea. Manure N needs to be converted by soil bacteria or fungi from an organic to an inorganic form to be available for plant uptake. Wheat is a short season crop with high N demand early in the growing season. Therefore, N mineralized from manure at rates assuming 50% availability may not be available soon enough for the quickly developing wheat crop.
Manure application studies conducted at the Carrington Research Extension Center using corn as the target crop have shown no differences in yield when manure or commercial N was used assuming manure N availability calculated at 50%. Several things happen that may impact the wheat vs. corn response to manure. Assuming 50% of the total N in manure is available for crop uptake in year 1 of application may not meet wheat N needs. More research is needed to determine what plant available N percentage assumption is needed for wheat and other short season cereal grains. Secondly, the spring weather conditions in both 2008 and 2009 were significantly cooler than the average ND spring weather. Since manure N mineralization is driven by biological processes, the cooler than average temperatures may have had more impact on N availability than is typical.
However, while urea out produces manure when only yield is considered, fall-applied manure can return a greater profit per acre because of its cost effectiveness. Producers who do apply manure as a fertilizer for spring wheat, may want to apply a low rate of commercial N fertilizer at planting to maximize yield and return. As a side note, fall manure applications produce higher yields and better quality spring wheat than spring-applied manure.
Ron Wiederholt and Chris Augustin, NDSU Nutrient Management Specialists
Carrington Research Extension Center, Carrington, ND
This research summary is not peer-reviewed and the authors have sole responsibility for the content.