To address economic cost of N fertilizer and environmental management issues on dairy farms, Cornell University researchers and extension educators conducton-farm research and extension on nitrogen needs for corn in rotation from sods.

In New York State, an estimated 990,000 acres is planted to corn with 550,000 acres harvested for silage corn. Doubling of nitrogen prices (currently about $0.40 per lb of N) and environmental concerns related to N loss from farm fields have caused many corn producers and their advisors to rethink current N management practices on the farms. In 2005, we have had reports that some farms reduced N use for all corn fields. This will have moderate to severe impacts on yield and quality of corn on any field that would have given yield return to additional nitrogen. A better approach would be to base N fertilizer additions on field history as farm business profitablity can be enhanced and environmental losses reduced if nitrogen management is more field specific and incorporates nitrogen credits from organic sources. We set out to test N needs for corn in rotation and evaluate tools for N management.

In 2002-2004, laboratory and field trials were conducted in NY to evaluate the performance of a new soil organic N test, the Illinois Soil N Test (ISNT) in identifying whether or not additional N is needed. This work has led to the development of critical ISNT values beyond which additional N from manure or fertilizer is not likely to result in a yield response. In 2005 and 2006 we conducted 16 first year corn trials and 12 second year corn trials throughout the state to address three questions: (1) do we need starter N, (2) do we need sidedress N; (3) what tools could help us decide. We determined: 1) dry matter yields and silage quality; 2) the performance of the ISNT and chlorophyll test procedure in predicting if extra N was needed, and 3) the utility of the end of season tests (soil nitrate test, stalk nitrate test) in identifying when too much N was applied. We did that using a networked research/extension approach.

These last two years, 16 on-farm and research station trials have shown no N is needed for first year corn beyond a small (30 lbs/acre) starter application. A survey currently being conducted shows potential savings of a minimum of $30-$40/acre in fertilizer and application expenses. Given 990.000 acres of corn, assuming 4 years is common, 25% of this acreage or about 250 thousand acres is first year corn. If we conservatively assume half of this acreage receives fertilizer now, we could have a total savings of $4-5 million (in addition to the environmental benefits). Individual impact statements developed recently with 4 participating producers are beginning to show the impact these findings can have on nitrogen and manure management on farms (
http://nmsp.css.cornell.edu/projects/Nitrogenforcorn.asp).
Eliminating N fertilizer use for first year corn is the single largest financial and environmental impact we can have on N use for corn in the state. We will monitor N sales reported by NYSASS and NYSDAM to document actual impact over the next couple of years. Tools for management beyond first year corn are still being tested.

Northern New York Agricultural Development Program (NNYADP).

• Karl Czymmek (Senior Extension Associate, Pro-Dairy)
• Greg Godwin (Research Support Specialist, Cornell CSS)
• Mike van Amburg (Associate Professor, Animal Science)