Conserving end-of-season N with effective seeding dates for cover crops based on fall growing degree days

Conserving end-of-season N with effective seeding dates for cover crops based on fall growing degree days

Summary

Our hypotheses are i. that fall-winter losses of N leaching in corn fields are avoidable, and can be reduced or prevented if cover crops are used, and are planted early enough to be effective, and ii. that use of cover crops and nutrient management has economic benefit to the farmer, can be integrated into the cropping system through outreach and education, and is transferable to other regions.

Objectives/Performance Targets

Our objectives are i. to determine critical seeding dates and a growing degree day (GDD) model for rye cover crops. ii. To evaluate methodologies for early establishment of cover crops, and iii. to demonstrate the economic benefit of adopting “effective” cover crops.

Of 20 dairy/livestock farmers who participate in on-farm studies and farm based outreach, 15 will use the developed assessment methods for cover crop effectiveness in recovering end-of-season nutrients, and 10 will make management decisions (changes) to ensure cover crops are effective for N uptake.

Accomplishments/Milestones

1. In the first year (2006) 10 farm demonstrations were established. These were monitored after winter for crop survival and N contribution in spring of 2007. Two of these studies were evaluated for growth of corn following the incorporation of the rye cover crops, and 9 addtional farm demonstrations were established as described below.

2. Because inter-seeded cover crops into corn proved less than successful at the 8 farm locations an alternative strategy was followed in 2007. Cover crops in corn silage production were viewed as part of a total production system. The limitation to planting cover crops early for fall N accumulation is in part the harvest date of corn which is often too late for effective establishment of the cover crops. Therefore, our approach this year was to also involve farmers in an evaluation of yield potential of early hybrids comparing them to the later maturing hybrids they usually plant, and in time of planting studies since early planting helps ensure higher yield and earlier harvest.

3. Visits were made to farms involved in cover crop planting, early hybrid evaluation and time of planting trials. Research methodology for on-farm evaluations. The on-going evaluation at the UMass Crops Research and Education Center continued.

4. Data from evaluations is being summarized and were discussed at a farmer research group meeting was held in late winter early spring with more than 20 farmers present.

5. Results were presented at the New England Certified Crop Advisors meeting in February 2007.

6. Preliminary work on growing degree model was completed and graphs were shown in education programs in 2007. This work is being refined after compiling the growth and temperature data in this second year and GIS maps for seeding dates and fall GDDs are being developed.

7. UMass and participating farmers hosted one on-farm field meeting, and a field day showcasing cover crops and corn hybrid evaluations.

Impacts and Contributions/Outcomes

1. Early establishment of cover crops dates were confirmed for effectiveness in end-of-season N uptake. On-farm studies early seeded cover crops accumulated close to 100 lb N/ac from the fall applied manure and carryover N from the previous corn crop. On incorporation the following corn crop had PSNT levels exceeding 25 ppm in June while cover crops seeded on September 15 or later had PSNT levels below this threshold.

2. While interseeding of at time of topdressing had been shown to be successful for annual ryegrass but not winter rye, the annual rye winter killed and made insufficient growth after the corn harvest to accumulate a significant amount of N. Smooth bromegrass which also survived was not as vigorous as the annual ryegrass.

3. The preliminary GDD analysis is being evaluated with varying base temperature to refine the GDD model for cover crops. A template has been developed for GIS maps relating GDDs to all farm locations in the state.

4. Results of the early hybrid evaluation are being compiled and as are results from the time of planting study. Detailed information on harvest maturity dates is being kept.

Collaborators: