Author: mem40@cornell.edu

Weed Science Society of America Has Lesson Module on Herbicide Resistant Weeds

Russell R. Hahn, Department of Crop and Soil Sciences, Cornell University

According to the International Survey of Herbicide Resistant Weeds (http://www.weedscience.org), 372 resistant weed biotypes representing 116 dicot (broadleaf) and 85 monocot (grass and sedge) species have been confirmed as herbicide resistant as of February 1, 2012. Historically, there was great concern about triazine resistant (Photosystem II inhibitors – Group 5 herbicides) weed biotypes, which now number 69 (Table 1). In recent years, concern has shifted to ALS (Acetolactate Synthase inhibitors – Group 2 herbicides) and to glyphosate (EPSP Synthase inhibitors – Group 9 herbicides) resistant weeds. In the case of ALS resistance, this heightened concern is due to the rapid increase in the number of weed biotypes (116) that are resistant to these Group 2 herbicides and due to the fact that there are numerous herbicides with this mechanism of action that are used on multiple crops. Finally, although there are only 21confirmed cases of glyphosate resistant weeds, the widespread adoption of glyphosate resistant crops and the increased used of glyphosate herbicide has placed a spotlight on weed populations resistant to this mechanism of action.

The continued increase in the number of herbicide resistant weeds along with the fact that no new herbicide mechanisms of action have been introduced in recent years prompted the Weed Science Society of America (WSSA) to develop a lesson module on herbicide resistant weeds. The intended audiences for these lessons are ag professionals, including Certified Crop Advisors, extension educators, dealers, custom applicators, and others who interact with or advise growers on weed management practices. The lessons can be accessed on the WSSA website at http://www.wssa.net under “WSSA News”. The modules are available for download as PowerPoint slides or as a Flash File. According to the Training Module Agreement, “WSSA grants you a limited license to use these materials for training and educational purposes. Slides may be used individually, and their order of use may be changed; however, the content of each slide and the associated narrative may not be altered.” A brief description of the five lessons in the WSSA Lesson Module on Herbicide Resistant Weeds follows:

Lesson 1 – Current Status of Herbicide Resistance in Weeds, helps understand the need for herbicide resistance management and provides information on the status of herbicide resistance by mechanism of action, on the increase in weeds with resistance to multiple mechanisms of action, and on the global distribution of herbicide resistance.
Lesson 2 – How Herbicides Work, provides information on terminology associated with herbicide use along with an understanding of how herbicides are grouped according to their mechanism of action.
Lesson 3 – What is Herbicide Resistance? A definition of herbicide resistance, an understanding of the different types of resistance, and information on how resistant weed populations develop are included in this lesson.
Lesson 4 – Scouting After a Herbicide Application and Confirming Herbicide Resistance, provides information on the importance of scouting for herbicide resistant weeds, on reasons why weeds can be present after herbicide application, on knowing how to identify herbicide resistance in the field, and on procedures for confirming resistance in the field or greenhouse.
Lesson 5 – Principles of Managing Herbicide Resistance, provides an understanding that diversity is an important concept in resistance management, identifies broad strategies and specific tactics for managing herbicide resistance, and compares the value of proactive and reactive management practices.

Although New York State has been fortunate to have limited problems with herbicide resistant weeds, these lessons provide an in-depth understanding of this growing problem and information on how farmers can avoid or deal with herbicide resistance.

Can Manure Replace the Need for Starter Nitrogen Fertilizer? 3-Year Summary

Quirine M. Ketterings, Greg Godwin, Sheryl N. Swink, Joseph Foster, Eun Hong, Karl Czymmek, Carl Albers, Peter Barney, Brian Boerman, Stephen Canner, Paul Cerosaletti, Aaron Gabriel, Mike Hunter, Tom Kilcer, Joe Lawrence, Eric Young, and Alex Wright

Background
Initial studies at a Western New York State dairy farm showed that for corn fields with a recent manure history, starter nitrogen (N) fertilizer could be eliminated without losing yield or reducing forage quality. Eliminating starter N on corn fields with a manure history has the potential to deliver significant savings of time and money to dairy producers. In 2009, we initiated a 3-yr project to test the need for starter N fertilizer across a range of New York State soil types and growing conditions. The objective of this study was to assess differences in yield and forage quality between corn that receives starter N fertilizer and corn that does not, on fields with varying manure history. Here we report the 3-year summary for sites completed without external challenges (weed control, bird damage, planter issues, harvest challenges, etc.). The final dataset included 21 trials, distributed throughout New York State.

Materials and Methods
Each trial included four replications or more of two treatments: 30 lbs N/acre in the starter versus no N in the starter. In 2009, seven trials were completed, including three trials at commercial farms and four at the Aurora Research Farm (sites 1 through 7). In 2010, starter N response trials were established at ten commercial farm locations and repeated at the Aurora Research Farm (sites 8–21). In 2011, an additional seven sites were established on commercial farms. Across all trial years, a total of seven trials were lost due to planter issues, excessive moisture interfering with planting and/or harvest, bird or deer damage, weed pressure, excessive variability, or uncertainty about the actual treatment allocation. All other trials (21 sites) are included in this summary.

Results
Eleven sites had an ISNT-N level classified as “deficient in soil N supply potential” (>7% below the critical value), five sites were “marginal in soil N supply potential” (within 7% of the critical value) while five sites were “optimal in soil N supply potential” (ISNT-N >7% above the critical value).

Across all three years, of the fields with optimal soil N supply potential (sites 19, 20, 21, 23, and 25), the manure application alone was sufficient to meet the N needs of the crop; none of these three locations showed a yield increase with starter N use (Table 1). The CSNTs (Table 2) confirmed N was not limiting yield at these sites, and for two locations (20 and 21) showed sidedress application rates can be reduced if not eliminated. Used in this way, the data suggest that the ISNT can help identify fields that will not benefit from starter or sidedress N.

Of the five sites that were classified by the ISNT as marginal in soil N supply potential, all received manure and only one (site 31) responded to starter N. The CSNTs were classified as optimal (sites 13, 31, and 35) or excess (sites 3 and 14), indicating that the fields received sufficient or more than sufficient N (Table 2). However, the lowest CSNT was measured for the site that had the yield response to starter N, suggesting an adjustment in CSNT interpretation is needed (inclusion of a 250–750 ppm “Marginal” range). We conclude for these five locations that manure application can replace starter and sidedress N for soils with a marginal soil N supply potential, as long as sufficient N is added with the manure. The results of site 31 also suggest that in some years a response to N can be expected where CSNTs are <750 ppm.

The sites classified as deficient in soil N supply potential (i.e., soil N alone is not expected to supply sufficient N for the corn crop that year) included the trials at Aurora with either no manure history (sites 6 and 11), or with limited manure history (sites 4, 5, 7 in 2009, and 9, 10, 12 in 2010) plus three on-farm locations (sites 8, 15, and 16). The results at sites 6 and 11 (significantly higher yields in 2010 with starter N and a similar though not statistically significant trend in 2009) suggest that starter N is needed for fields that do not have an optimal soil N supply as measured by the ISNT and are managed without manure. The results at site 11 also suggest that a response to N can be expected if CSNTs are <750 ppm (high producing year on deficient ISNT soil), consistent with the results of site 31.

At the other 3 sites at the Aurora Research Farm (4, 5, 7 in 2009; 9, 10, 12 in 2010), liquid manure had been applied at a rate of ~8,000 gallons/year over the past 5 to 6 years. Manure application increased ISNTs over time (compare values to sites 6 and 11), but after 5 to 6 years of manure application, the ISNT of these sites was still classified as deficient. Of these six site*years, three showed a significant yield increase with starter N addition, while a similar trend was seen for the other three sites (Table 1). These same sites exhibited deficient CSNTs (Table 2), suggesting that the specific manure history was not enough to increase soil N supply to levels high enough to supply the N needed by the crop and that the current year manure applications were also insufficient to meet N needs of the crop. Under these conditions, the starter N application was needed.

Of the remaining three on-farm sites with low soil N supply potential, two sites had CSNTs in the optimal range (without starter). A lack of a yield response to starter N illustrated that for these locations, the current year manure supplied sufficient N and starter N was not needed. The very high CSNT of site 15 >5000 ppm) suggests a reduction in sidedress N application was possible without an impact on yield or quality.

Of the silage trials, two locations showed a significant increase in crude protein with starter N addition (sites 3 and 21) while at one site, crude protein declined with starter N addition (site 25). Soluble protein increased at two locations, although the difference was very small (an increase of 0.3 and 0.1% in soluble protein at sites 3 and 16, respectively) and decreased at one site (site 25). Only one site showed a change in NDF (decrease, site 21). At one site, NDF digestibility increased with starter N addition (site 23) while at two additional sites, NDF decreased with starter N addition (sites 31 and 35). Lignin and starch were not impacted at any of the silage trials. Elimination of starter N did not result in significant differences in milk per acre estimates except for at one site where starter use decreased milk per ton (site 25, results not shown). Milk-per-acre estimates were only impacted at one site (increase at site 31, consistent with the yield increase upon starter N use).

Sites 6 and 11 (the only deficient ISNT sites without a manure history) illustrate that starter N will be needed even if sidedress N is applied. This scenario applies to cash grain operations without manure histories. Under those conditions, the best management practice is to use starter N (20-30 lbs N/acre) and sidedress to meet crop N needs. Omission of starter N is not recommended for fields without a manure history (deficient ISNT-N).

Sites that were classified as sufficient in ISNT-N included sites 19–25 (5 sites). None of these five sites showed a yield response to starter N addition. We conclude that if the ISNT is classified as sufficient, manure can be used to replace starter N.

Manured sites that were sidedressed (sites 15, 20, 21, 25, and 35) all had CSNTs that were optimal or excessive. Starter N use did not increase yield at any of these locations. Optimal or excessive CSNTs at each of these five locations suggest that sidedress N could have been eliminated or application rates reduced at these locations. These results suggest that starter N can be omitted for sites with a manure history even if the ISNT is deficient or marginal, as long as sufficient N from manure and other sources (rotations, soil N, sidedress N) is available.

Sites that had a manure history but were classified as deficient in N based on the CSNT included sites 4–5, 7, 9–10 and 12 (6 sites). Of these sites (all Aurora Research Farm sites with some but limited manure application history), sites 5, 9, and 12 showed higher yields when starter N had been applied than where corn was planted without a starter, with similar trends at sites 4, 7, and 10 (all Aurora Research Farm sites). The ISNT for each of these Aurora Research Farm sites was classified as deficient, suggesting additional N was needed. These results indicate a response to starter N is likely if ISNT-N is deficient and additional N applied is insufficient.

The tool available to determine whether or not the overall N addition was sufficient is the CSNT. The yield results of sites 11 and 31 (locations with an average CSNT between 250 and 750 ppm plus a significant yield difference upon use of starter N), suggest that a new interpretation should be added for 2nd or higher year corn: “Marginal” (250–750 ppm), where a response to starter N could be expected in wet years.

Main Conclusions

  • Starter N should be used for fields with no manure history and no current year manure applications (deficient ISNT-N).
  • If the ISNT-N is classified as optimal, manure can be used to replace starter N without a yield or quality decline.
  • Manure can replace starter N for sites deficient or marginal in ISNT-N as well, but only if sufficient N from manure and other sources (cover crops, soil N, sidedress N) is available (CSNTs between 750 and 2000 ppm); a yield response to starter N would have been likely if the ISNT-N was deficient and additional N applied was insufficient as well.
  • A new interpretation should be added for the CSNT for 2nd or higher year corn: “Marginal” (250–750 ppm), where a response to starter N could be expected in some years. To reduce risk, it is recommended that farms strive for CSNTs between 750 and 2000 ppm, using 8-inch stalks taken between 6 and 14 inches above the ground.
  • We recommend producers analyze 2nd or higher year corn fields for both ISNT-N and CSNT, to identify sites where a starter N application can be omitted.

CNMSPAcknowledgments
The project was funded with federal formula funds and Northern New York Agricultural Development Program (NNYADP) funds. We thank the farmers for participating in the project. Questions about this project? Contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu

Dairy and Cash Grain Farmer Perceptions of the Value of Manure

Julia Knight1, Patty Ristow1, Graham Swanepoel1, Karl Czymmek1,2, and Quirine M. Ketterings1
1Nutrient Management Spear Program, 2PRODAIRY, Department of Animal Science, Cornell University

Introduction
A policy interest in regional nutrient balances and farm interests in the value of manure inspired a study to begin understanding and characterizing the current state of manure exports and imports in New York State (NYS). Initial discussions with producers, farm advisors, and policy makers showed a need for more information on (1) the current movement of manure between dairy and crop farms, and (2) the (perceived) value and costs of manure handling for both dairy and crop farmers. The purpose of this study was to obtain information about current manure use, transfers, drivers and limitations, and the value of manure as perceived by crop and dairy producers.

Figure 1. Postcard style surveys were handed out to dairy and crop producers in the winter of 2010.

Farmer Surveys
Surveys (postcards, see Figure 1) were handed out across New York (NY) during fifteen farmer meetings held between January 1 and March 31, 2010. Overall, 266 surveys were
completed (200 dairy and 66 crop producers) representing 38 NY counties, and 7 counties from Vermont, Connecticut and Maine.

Main Findings
Among those surveyed, the average dairy farm had 295 cows with 625 acres of cropland. The average crop farm was 1030 acres. Across dairy farms, 86% of the acreage received manure (535 acres out of 625 acres of the average dairy farm), 47% had at least 6 months of manure storage.

All of the farms with 700 or more cows (17 farms) tested manure at least annually versus 40 of 53 farms (75%) for farms with 200-699 cows. At farms with 100-199 cows, manure was tested annually by 10 of 34 farms (29%) and once every 2-3 years by 17 of 34 farms (50%). Of the farms with less than 100 animals, 66% never tested manure for nutrient content (Figure 2).
Manure was exported off the farm by 20% of the 200 dairy producers that were surveyed. The most important reason for not exporting (more) manure was the perceived lack of manure to meet crop nutrient needs at the dairy farm itself (Table 1).

Of the crop producers surveyed, 64% reported that they apply manure to an average of 41% of their crop acres, indicating manure export from dairy farms to crop farms is occurring in the region. Crop producers who did not import manure indicated lack of availability and concerns about compaction as the two main reasons to limit manure use on their farm (Table 2). Odor and costs were seen as less of a concern.

Both dairy and crop producers listed organic matter and nutrients as the most valuable manure properties (Tables 3 and 4). Enhanced soil water holding capacity (moisture retention) with manure use was considered less important.

There was a gap between the perceived value of manure by dairy producers and by crop producers. Dairy
producers on average priced manure at a value of $96 per acre with a range of $20 to $400 per acre while crop producers on average valued manure at $53 per acre with a range of $0 to $150 per acre, respectively.

Of those crop farmers that applied manure, only 21% indicated they had paid for the manure. The average payment per acre manure applied was $88/acre. Dairy producers estimated their actual manure handling and application costs to amount to $43/acre (averaged across the farms).

Manure nutrient distribution to non-dairy cropland is taking place in the region. However, many of the dairy farms (160 out of 197) did not export manure (Figure 3). The percentage of farms that export manure increases with an increase in animal density with a third of the farms exporting manure when animal densities exceeded 0.75 animal units per acre (1 animal unit equals 1000 lbs).

Preliminary Interpretations
Nitrogen management (timing and application method) choices can have a large impact on how much manure must be applied per acre to meet crop N needs. When less efficient N management practices (such as surface application without incorporation) are utilized, the P addition with the manure can substantially exceed crop P needs leading to greater P losses and/or accumulation in the soil. If dairies are able to improve N use efficiency of manure and fertilizer and/or add N from other sources (cover crops, greater reliance on N fixation, shorter rotations, building of soil organic matter levels through use of reduced tillage practices, etc.), they may have more manure available to move off the farm. More efficient manure N use coupled with increased manure distribution across the landscape has the potential to improve regional P balances and with increasing fertilizer prices, farms may be able to derive value from such transactions in future years

Conclusions
The survey results indicate crop and dairy producers value manure, mostly for its supply of nutrients and organic matter. Crop producers tended to place a lower monetary value on manure than dairy farmers which may reflect a deeper understanding by dairy farmers of the value of manure as a fertilizer replacement. The results of this survey reflect that manure export/import activities are currently limited by manure availability and a gap between the perceived dollar value of manure by dairy producers and by crop producers. However, the responses also indicate the potential for greater export from higher density dairy farms to crop farms in the future, as both groups share recognition of the benefits of manure.

CNMSPAcknowledgments
This work was sponsored by the Center for Dairy Excellence and the New York Farm Viability Institute. We thank the many Cornell Cooperative Extension educators who helped with the surveys. Questions about this project? Contact: Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.