What’s Cropping Up? Vol. 25, No. 2 – March/April – Full Version

The full version of What’s Cropping Up? Volume 25, No. 2 is available as a downloadable PDF and on issuu.  Individual articles are available below:

Control Glyphosate-Resistant Horseweed in Zone/No-Tillage Corn and Soybeans

Russell R. Hahn and R.J. Richtmyer III
Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University

Fig. 1: Over-wintering horseweed rosette.  From:  Weeds of the Northeast.  Photo by J. Neal.
Fig. 1: Over-wintering horseweed rosette. From: Weeds of the Northeast. Photo by J. Neal.

Horseweed, also known as marestail, is a winter or summer annual weed which reproduces by seed that germinates in spring or late summer.  Seed that germinate in late summer over-winter as rosettes or basal clusters of leaves not separated by stem elongation (Figure 1).  These over-wintering rosettes rapidly elongate (bolt) to produce erect flowering stems in the spring and early summer.  Mature plants are unbranched at the base and may be 6 feet tall with many small flowering branches near the top as shown in Figure 2.  Seeds are about 1/16 inch long with many white bristles on the end.  These bristles allow for wind dispersal of the seed.

Fig. 2: Horseweed plant showing the lower part of the leafy stem, upper part of the stem with flowers, and seed with slender bristles on one end. From: Weeds of the North Central States, North Central Regional Research Publication No. 281.
Fig. 2: Horseweed plant showing the lower part of the leafy stem, upper part of the stem with flowers, and seed with slender bristles on one end. From: Weeds of the North Central States, North Central Regional Research Publication No. 281.

Zone/No-Tillage Problem
Horseweed is native to North America and is commonly found in fallow fields, pastures, roadsides, and wasteland.  Although not common in conventionally tilled and planted fields, it is common where zone/no-tillage cropping is practiced.  Many of the states reporting glyphosate-resistant (GR) horseweed have a long history of no-tillage cropping.  In these areas, over-wintering horseweed rosettes have likely been subjected to glyphosate selection pressure since the 1970s when growers started using Roundup (glyphosate) for burndown in no-tillage fields.  With repeated glyphosate use over the years, susceptible horseweed plants were likely controlled while glyphosate tolerant plants flowered and set seed. This resulted in a shift to a horseweed population dominated by the resistant biotypes.

GR Horseweed is Widespread in U.S.

Fig. 3: Horseweed population that survived burndown and postemergence glyphosate applications.  Photo by R.J. Richtmyer III.
Fig. 3: Horseweed population that survived burndown and postemergence glyphosate applications. Photo by R.J. Richtmyer III.

The International Survey of Herbicide Resistant Weeds, http://www.weedscience.org, shows that 24 states in the U.S. have documented GR horseweed populations.  It appears that the increasing popularity of zone/no-tillage cropping in NY, along with the widespread use of GR crops and repeated use of glyphosate herbicides has led to the development of GR horseweed populations here as well.  Greenhouse trials with horseweed seed from two locations in Central NY are being conducted to confirm this.  In one case, glyphosate was applied for burndown prior to planting no-tillage soybeans and again for postemergence weed control.  As can be seen in Figure 3, horseweed survived both glyphosate applications.  Although field experiments to evaluate control programs for GR horseweed have not been conducted in NY State, conversations with weed science colleagues on the Delmarva, where GR horseweed was first confirmed in 2000, have been helpful in formulating control recommendations for GR horseweed in zone/no-tillage corn and soybeans.  Effective control programs target the rosette stage shown in Figure 1 as part of the burndown herbicide application prior to planting zone/no-tillage crops.  Once stem elongation begins, horseweed becomes increasingly difficult to control.  The other key element of an effective control program is to incorporate herbicides with sites of action that are different from glyphosate, which is a Group 9 herbicide.

Burndown/Control Recommendations
The recommendations shown in Table 1 are a first attempt to make written recommendations for GR horseweed in zone/no-tillage corn and soybeans.  They have not been incorporated into the Cornell Guide for Integrated Field Crop Management. They emphasize the importance of controlling horseweed early in the season when the plants are still in the rosette stage, and they incorporate herbicides with sites of action that are different from glyphosate (Group 9).  For both corn and soybeans, 2,4-D LVE (synthetic auxin or growth regulator Group 4 herbicide) makes a significant contribution to horseweed burndown/control.  For corn, residual herbicides like atrazine (photosynthesis inhibitor Group 5 herbicide), or Verdict a premix of Kixor (cell membrane disrupter Group 14 herbicide) and Outlook (seedling shoot inhibitor Group 15 herbicide), have proven helpful in controlling horseweed, and provide residual for control of summer annual weeds.  In the soybean recommendations, OpTill or Valor XLT help control the horseweed and provide residual weed control.  OpTill is a premix of Kixor and Pursuit (ALS inhibitor Group 2 herbicide), while Valor XLT combines Classic (ALS inhibitor Group 2 herbicide) with Valor, (cell membrane disrupter Group 14 herbicide).

Table 1.  Burndown/control recommendations for GR horseweed in zone/no-tillage corn and soybeans.
Table 1. Burndown/control recommendations for GR horseweed in zone/no-tillage corn and soybeans.

At this time, it seems prudent that NY farmers scout zone/no-tillage acreage for horseweed that is not readily controlled with glyphosate, and that they employ an aggressive herbicide resistance management plan.  Key elements of such a plan involve rotating herbicides with different sites of action, and using tank mixes/premixes or sequential applications that include herbicides with different sites of action.

Whole farm nutrient mass balance calculator for New York dairy farms

Melanie Soberon1, Quirine Ketterings1, Karl Czymmek1,2, Sebastian Cela1, Caroline Rasmussen1
1
Cornell University Nutrient Management Spear Program, 2PRODAIRY

Striking a whole farm balance
Environmental awareness and the desire for social, economic and environmental sustainability have led to more proactive management of farm nitrogen (N), phosphorus (P) and potassium (K) balances. Nutrient accumulation is when the amount of imported nutrients on farm exceeds the amount of nutrients exported from the farm. The implications of nutrient accumulation include degradation of water and air quality, which is reason for increased pressure on animal agriculture by the public, litigators and state and federal regulators. Similarly negative consequences can result from whole farm nutrient losses, when exported nutrients exceed the amount of nutrients imported on the farm. In these situations, the soil can be mined of nutrients, decreasing soil fertility and, when deficiencies start to occur, also crop yields. Thus, a clear understanding of the imbalances between farm nutrient exports and imports, and how they relate to farm management practices, is key to developing long-term, sustainable solutions for individual farms, and the animal industry in general.

Fig. 1: Whole farm nutrient mass balance assessment.
Fig. 1: Whole farm nutrient mass balance assessment.

Adaptive management
Sustainable solutions require improved nutrient use efficiency across the whole farm, balancing the nutrient flows of both the animals and the land. However, when it comes to whole farm nutrient management, it can feel like there are more questions for producers than time to evaluate and answer. Is cropland being fertilized at the proper times in sufficient quantities to supply nutrients to crops without accumulating nutrients? What nutrients need to be supplied in purchased fertilizer and feed this year to prevent nutrient loss? And once all those questions have been dealt with for the year, a new year comes around and the process begins anew. This is where a method of keeping track of nutrient management records from year to year in a systematic way can save time, money and conserve nutrients. The idea behind the adaptive management concept is to maintain nutrient management records in such a way that one can assess the nutrient status of the whole farm (Fig. 1), pinpoint the areas where improvements can be made, and then track the progress of those improvements year to year. The whole farm nutrient mass balance (NMB) calculator is a tool that was developed to help in the assessment.

A whole farm assessment tool
The whole farm NMB calculator was first developed by Stuart Klausner at Cornell University, and modified and reprogrammed in Microsoft Visual Basic in more recent years. The software and supporting information (manual etc.) are downloadable from the whole farm nutrient mass balance project page of the Cornell Nutrient Management Spear Program (NMSP): http://nmsp.cals.cornell.edu/projects/massbalance.html. The NMB calculator is targeted for use by dairy farms, though it can be used to determine NMBs of any type of livestock operation. A data questionnaire was developed to help gather the data listed in Table 1.

Ketterings paper 1 table 1Within the NMB calculator, there are four basic pools where nutrients can be allocated on a farm: (1) they are imported to the farm in the form of purchased products; (2) they are exported from the farm as products sold/exported; (3) they remain on the farm to be recycled; or (4) they are lost to the environment. The NMB program calculates N, P, and K imported onto and exported from the farm in the form of feed, fertilizer, animals, crops, milk, manure and bedding. The difference between nutrients imported and nutrients exported is expressed as N, P and K balance per acre of cropland, and per unit (cwt or hundred weight) of milk produced (Fig. 1). Negative values are not sustainable over time, as they indicate that more nutrients are being taken off the farm than are replaced. However, large positive balances are not desirable either, as they indicate nutrient inefficiencies and increased risk for environmental losses.

To demonstrate how the NMB calculator assists producers in evaluating best management practices, data from a central New York dairy farm were analyzed over the course of 8 consecutive years (2003-2010). In the initial assessments, NMB values were high, and 76, 69 and 64% of the imported N, P, and K remained on the farm (Fig. 2). However, by gradually matching feed and fertilizer purchases with animal and crop needs, the farm reduced its nutrient imbalances, and only 45, 34 and 31% of the imported N, P, and K remained on the farm in recent years. Moreover, the improvements made resulted in a milk production per cow increase from a little less than 23,000 to more than 24,000 lbs of milk over the same time period.

Fig. 2. Nitrogen, phosphorus and potassium mass balances (lbs/acre) measured by a New York case study dairy farm over 8 years.
Fig. 2. Nitrogen, phosphorus and potassium mass balances (lbs/acre) measured by a New York case study dairy farm over 8 years.

Farmer feedback
Farmers and their advisors can utilize the NMB calculator to increase nutrient use efficiency on the farm and monitor progress over time. They can also compare their farm’s nutrient balance to those of peers in the dairy industry with similar milk production. Comments of participating farmers included:

“Pulling together the information is useful in itself and it gets me to look at numbers in a different way.”

“Participating in the NMB is one way to show that we are doing our best to comply with regulations; it demonstrates that we are good environmental stewards.”

In summary
Whole farm adaptive management approaches to nutrient management have been recognized by the Natural Resources Conservation Service (NRCS) in its new national NRCS590 standard and many states are currently discussing approaches for implementation. The NMB calculator generates an overall summary of N, P and K balance of a particular farm using recorded imports and exports; these annual summaries can assist producers in making management changes that lead to more efficient production and resource conservation.

Additional resources

  • Soberon, M.A., Q.M. Ketterings, C.N. Rasmussen, and K.J. Czymmek. 2013. Whole Farm Nutrient Balance Calculator for New York Dairy Farms. Nat. Sci. Educ. 42:57–67.

Ketterings ack imagesAcknowledgments
Thanks to all the farmers, consultants, SWCD and NRCS staff, and Cornell Cooperative Extension educators that participated in this study. Thanks also to Françoise Vermeylen from the Cornell University Statistical Consulting Unit for statistical advice. This work was supported by grants from the Northern New York Agricultural Development Program (NNYADP), Northeast Sustainable Agriculture Research and Extension (NESARE), Federal-Formula Funds, and a USDA-NRCS Conservation Innovation Grant. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/

Feasible whole farm nutrient mass balances for New York dairy farms

Sebastian Cela1, Quirine Ketterings1, Karl Czymmek1,2, Melanie Soberon1, Caroline Rasmussen1
1
Cornell University Nutrient Management Spear Program, 2PRODAIRY

Nutrient mass balances for New York dairies
A whole-farm nutrient mass balance (NMB) is the difference between the amounts of N, P, and K imported onto dairy farms as feed, fertilizer, animals, and bedding, and exported via milk, animals, crops, and manure. We can express a NMB per tillable acre to indicate the potential for recycling nutrients in the land base, an environmental indicator, or per hundred weight (cwt) of milk, a milk production efficiency indicator.

The importance of measuring nutrient mass balances
Large positive NMBs per acre suggest high risk of nutrient losses to the environment, while large positive NMBs per cwt reflect low nutrient use efficiencies, and potential economic loss for the farm as well. Negative NMBs (resulting from exports exceeding imports) reflect mining of soil P and K resources, and will eventually reduce crop yields. Annual NMB assessments give farmers a chance to compare the farm against peers in the same milk production group, and to evaluate the impact of management changes on nutrient use efficiency and production.

Distribution of nutrient mass balances across New York dairy farms

Fig. 1: Distribution of N, P, and K mass balances (lbs/acre) for concentrated animal feeding operations (CAFOs) and animal feeding operations (AFOs) based on 102 NY dairy farms.
Fig. 1: Distribution of N, P, and K mass balances (lbs/acre) for concentrated animal feeding operations (CAFOs) and animal feeding operations (AFOs) based on 102 NY dairy farms.

In 2006, NMBs for 102 dairy farms from 26 different New York counties showed a range from  -35 to 211 lbs N/acre, from -7 to 45 lbs P/acre, and from -45 to 132 lbs K/acre (Fig. 1). Also the NMBs per cwt of milk varied widely among New York dairies: from -1.3 to 2.6 lbs N/cwt, from -0.11 to 0.47 lbs P/cwt, and from -0.73 to 1.69 lbs K/cwt. Ranges in NMB were similar when comparing CAFOs and AFOs.

How do nutrient mass balances relate to milk production per cow?
Dairy farms in our database averaged 19,600 lbs milk/cow per year, slightly higher than the average milk production of New York dairies in 2006 (18,900 lbs/cow per year). Dairy production does not depend on large positive balances (Fig. 2); we found high producing dairies (>20,000 lbs milk/cow per year) with negative NMBs per acre as well as high producing dairies with large positive NMBs per acre.

Fig. 2: Relationships between milk production per cow and nutrient mass balances per acre show that highly productive farms can operate within the feasible balances.
Fig. 2: Relationships between milk production per cow and nutrient mass balances per acre show that highly productive farms can operate within the feasible balances.

What’s a “feasible” nutrient mass balance?
The data showed large ranges in NMBs among the 102 farms, but this does not tell us what is reasonably achievable, or “feasible”. A feasible NMB should allow dairy farms to be economically profitable, environmentally sustainable, and flexible enough to allow for the many variations among farms. Ketterings paper 2 table 1Based on the largest dairy farm database we had for one individual year (2006), we defined “feasible” NMBs per acre as those at or below which 75% of the dairy farms in our database were operating: ≤105 lbs N/acre, ≤12 lbs P/acre, and ≤37 lbs K/acre (Table 1). We also defined a “feasible” NMB per cwt of milk produced as those at or below which 50% of the dairies were operating in 2006: ≤0.88 lbs N/cwt, ≤0.11 lbs P/cwt, and ≤0.30 lbs K/cwt (Table 1).

Fig. 3: Feasible balances (optimal operational zone) based on 102 dairy farms in New York.
Fig. 3: Feasible balances (optimal operational zone) based on 102 dairy farms in New York.

Combining both indicators, the most efficient farms have balances in the green area in Fig. 3. Although the current assessment of feasible balances for New York can change over time as more farms join the study, evaluations so far have shown that farms that operate outside of the green area (Fig. 3) might have opportunities for improvements in nutrient use.

 

Drivers of nutrient mass balances
Farms with high animal densities (more cows per acre) tend to have higher NMBs per acre than low density farms, and therefore higher risk of nutrient losses to the environment. However, NMBs per cwt are unrelated to animal density, except at very low density farms (Fig. 4). This suggests that high density farms need to operate with high nutrient use efficiencies to reduce the risk of nutrient losses. Farms that grow a high proportion of the feed in the farm itself tend to have lower NMBs per acre and similar NMBs per cwt than farms that purchase much of the feed (Fig. 4).

Fig. 4: Relationship between the N mass balances per acre and per cwt (without manure export) and animal density and farm produced feed.
Fig. 4: Relationship between the N mass balances per acre and per cwt (without manure export) and animal density and farm produced feed.

Opportunities to improve nutrient mass balances
Experiences with a large number of farms over the past ten years has shown that opportunities exist for some dairy farms to improve NMBs by producing more feed on the farm, implementing precision feeding, adjusting fertilizer use, exporting crops (in farms with low animal densities) and exporting manure (in farms with high animal densities). Farms with less than 1 animal unit per acre (about 2 acres per cow plus her replacement) were typically able to stay below the feasible balances, whereas on higher density farms, export of manure and/or crops was needed to lower balances.

Additional resources

  • Cela, S., Q. Ketterings, K. Czymmek, M. Soberon, and C. Rasmussen. 2014. Characterization of nitrogen, phosphorus, and potassium mass balances of dairy farms in New York State. Journal of Dairy Science 97:1-19.
  • Soberon, M.A., Q.M. Ketterings, C.N. Rasmussen, and K.J. Czymmek. 2013. Whole Farm Nutrient Balance Calculator for New York Dairy Farms. Natural Sciences Education 42:57–67.

Ketterings ack imagesAcknowledgments
Thanks to all the farmers, consultants, SWCD and NRCS staff, and Cornell Cooperative Extension educators that participated in this study. Thanks also to Françoise Vermeylen from the Cornell University Statistical Consulting Unit for statistical advice. This work was supported by grants from the Northern New York Agricultural Development Program (NNYADP), Northeast Sustainable Agriculture Research and Extension (NESARE), Federal-Formula Funds, and a USDA-NRCS Conservation Innovation Grant. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

What’s Cropping Up? Vol. 25, No. 1 – January/February – Full Version

WCUVol25No1 coverThe full version of What’s Cropping Up? Volume 25, No. 1 is available as a downloadable PDF and on issuu.  Individual articles are available below:

Farmers with Diverse Nitrogen Management Practices Find Value in the Adapt-N Tool in Iowa

Margaret Ball1, Bianca Moebius-Clune2, Shannon Gomes3, Aaron Ristow1, Harold van Es1,  Soil and Crop Sciences, Cornell University1, NRCS Soil Health Division2, Cedar Basin Crop Consulting3

Shannon Gomes, owner of Cedar Basin Crop Consulting, provides services for 25 farmers in Northeast Iowa. Gomes, with his 28 years of consulting experience and a Master’s degree from Iowa State University, has extensive knowledge of Iowa soils and a particular interest in precision management. He emphasizes a scientific approach in his work, advising clients and helping them run trials to assess the many available tools and products on their farms.

Shannon Gomes provides consulting services to 25 farmers in Northeast Iowa and has been using the Adapt-N tool.
Shannon Gomes provides consulting services to 25 farmers in Northeast Iowa and has been using the Adapt-N tool.

Gomes has long been searching for a better way to monitor nitrogen (N) availability and provide precise N recommendations. He’s tried “all the different nitrogen management tools,” with varying results, but has never been satisfied. When he stumbled upon Adapt-N in 2009, he found what he had been looking for: a real-time, location-specific adaptive N recommendation model that accounts for weather, management practices, and field variability. Since then, Gomes’ expertise and enthusiasm have been essential in field-testing Adapt-N over three seasons and introducing the tool to Iowa. He now models all his clients’ corn acres in Adapt-N, using it as both a starting point for his N recommendations, and a teaching tool for understanding complex N dynamics. We spoke with Gomes, his colleague Frank Moore, and two farmer clients—Nick Meier and Ken Humpal—to learn how they are using Adapt-N.

The Farmers

Nick Meier

Nick farms 1200 acres on a corn-soy rotation for grain and seed production. Typical of most farmers in Iowa, he used to apply all his nitrogen in the fall, but now puts on half (80 lb/ac) in the fall, another 30 lb/ac with pre-emergence herbicide, and the remainder (about 50 lb/ac) as an early sidedress application around the V2 stage. Adapt-N simulations of each field, run by Gomes, allow Nick to adjust this final sidedress application based on the spring’s weather conditions and other field-specific factors.

Nick has completed three Adapt-N field trials. In 2012, Adapt-N recommended that he skip sidedressing altogether. There was no yield penalty, and he saved $34/ac on fertilizer and operational costs. Though waiting until sidedress sometimes makes Nick nervous, he appreciates the reduced risk of losses, and is still pushing his N applications later, as much as his comfort level will allow. In 2013, the tool warned that much of the fall-applied N had been lost to rain, and Nick should adjust his sidedress rate upward by 30 lb/ac. The higher rate yielded 14 more bu/ac and +$57/ac profit.

Ken Humpal

Ken raises dairy and beef cattle, corn (grain and silage), soy, and alfalfa on 1700 acres. Like Nick Meier, he used to apply all nitrogen in the fall, but now puts about 50% of the season’s N on as spring pre-plant (anhydrous ammonia) and the rest as sidedress. On sandier ground, he’ll skip the pre-plant altogether and wait for sidedress, because leaching risks are higher.

Ken used late spring soil nitrate tests (PSNT) in the past to determine N rates, adjusting for alfalfa and soybean credits. Now, Ken uses Adapt-N recommendations for all his acres, with minor adjustments.   The tool helps account for variation in his fields due to OM content (3-5%), previous crop (corn, soy, alfalfa, or cereal rye cover crop), manure history, and soil type influences. It also helps him track the retention or loss of nitrogen from manure applications, for purposes of nutrient management planning and regulation compliance.   Ken completed one Adapt-N field trial in 2011. In this instance, the tool recommended he apply 30 lb N/ac above his usual practice, and the higher rate was justified by a 6 bu/ac higher yield and +$13/ac profit.

Frank Moore

Frank is a consultant colleague of Gomes and a farmer himself.  He grows corn and soy on 2000 acres, and develops nutrient management plans for his clients through Three Rivers Ag Consulting. Unlike many Iowa farmers, Frank does not apply N in the fall or at planting but rather applies only 30 lb N/ac with pre-emergence herbicide.  The rest of the season’s N is added at sidedress, using Adapt-N-recommended rates. His sidedressing equipment can be driven in corn up to about 18” tall without damaging it, even at this stage. It takes Frank about 5 days to sidedress 1000 acres of corn, but he’s never been rained out. Sidedressing does cost slightly more for the extra trip, Frank says, but it is worth the minimized risk of N losses, and the ability to reduce total N applied in dry years.

Before Adapt-N, Frank applied all N with his pre-emergence herbicide. This system “works about 3 out of 5 years”, he says, but not when you have excessive rain. Using Adapt-N hasn’t greatly changed Moore’s N rates overall, but it has helped him shift more N from spring to sidedress, and adjust for weather. He applied less than normal across his farm in 2012, and more in the wet season of 2013. In addition, Frank completed six trials of Adapt-N on his fields and on average, Adapt-N reduced N rates by 22 lb/ac resulting in insignificant yield and profit changes. Frank says the biggest savings from his N program have come in extreme circumstances. In 2013, when spring weather prevented planting in many fields, Moore estimates he saved $35,000 by avoiding putting N on early!

Using Adapt-N

“When you compare [Adapt-N] to other tools… nothing even comes close,” says Gomes, “and I’ve used all of them!” In a normal weather year, Gomes and his farmers observe that Adapt-N recommends N rates similar to what they would use otherwise. However, the tool is particularly useful in accounting for contrasting weather scenarios. For instance, in the very dry 2012 versus the very wet 2013 springs, Adapt-N helped Gomes “stay ahead of the curve” – recognizing and correcting N shortage in a field before the crop showed signs of deficiency.  Adapt-N has allowed growers to reduce N applications by 29 lb/ac on average with no yield penalty, resulting in average savings of $17/ac.

The tool is convenient—it achieves field- and sub-field-level precision without the large sampling effort associated with in-season field-measurements.  Before using Adapt-N, Gomes based N recommendations on PSNT samples from a few thousand acres per year. Although many samples can be taken, it’s hard to be sure they are representative. When it rained after sampling, he had to go out and re-sample, or assume that test results were no longer useful. Gomes and Ken Humpal agree they can now monitor soil N availability through Adapt-N – its previous-day high resolution precipitation data gives the closest thing to real-time N measurements, and doesn’t require in-season waiting on the results of lab tests. “I think [Adapt-N] is the thing!” Ken says. Within 24 hours of a rainfall event “you know what you’ve got out there.”

The model provides graphs of available soil N, N uptake and losses, rainfall, temperature, and other factors that are extremely useful as teaching tools, understanding recommendations, and for scenario testing through retrospective runs. For example, from the wet season of 2013 we can see Adapt-N’s “what-if” N timing simulations comparing standard management, Nick Meier’s actual management, and the Adapt-N recommendation (Figure 1; sidebox). This can help a farmer re-examine previous N management programs, and consider the effects of new programs before actually putting them into practice.  “The most powerful part of the interface is the graphs,” says Gomes. “You can sit down with a farmer and show them what’s really happening.”

Iowa Case Studies Figure 1 sidebox

Figure 1.  Adapt-N “what-if” simulation of three N timing practices (fall only; fall/spring/sidedress; and spring/sidedress) in a wet season.  Adapt-N recommendations in this simulation would have minimize N losses and required less total N for an equivalent yield.
Figure 1. Adapt-N “what-if” simulation of three N timing practices (fall only; fall/spring/sidedress; and spring/sidedress) in a wet season. Adapt-N recommendations in this simulation would have minimize N losses and required less total N for an equivalent yield.

Future Directions

Figure 2. Weather and soil health properties interact to influence soil N dynamics. Such field-scale differences influence physical and biological factors that drive N mineralization and losses as shown in the aerial view of Ken Humpal’s farm.
Figure 2. Weather and soil health properties interact to influence soil N dynamics. Such field-scale differences influence physical and biological factors that drive N mineralization and losses as shown in the aerial view of Ken Humpal’s farm.

Gomes is proud that he has persuaded most of his clients to move away from fall N application—a project he’s been working on for quite a while. Now that he uses Adapt-N for recommendations on all client acres, he is able to offer even more incentive to plan on sidedressing, using more precise rates adjusted in season.

Shifting toward sidedress is not without its concerns. Nick and Ken worry about getting rained out and missing the critical window to fertilize, or damaging young corn. Ken remains confident however that sidedressing risks and costs are justified by the additional savings he found during three years of field trials. “I’m excited about Adapt-N,” he says “it’s just a matter of fitting it into the system…” Frank Moore has found great benefit in sidedressing, and risks of rain-out or damage to corn have not caused him problems in his many years using this system. As high-clearance equipment, RTK/GPS, and variable rate technology are becoming more common among growers and custom applicators, the incentives for sidedressing are starting to clearly outweigh the challenges.

What is on Shannon Gomes’ mind for the future? He is strongly interested in soil health testing and helping his clients improve their soil management. Soil health and nitrogen management are closely connected (Figure 2), and Gomes is looking at cover crop and tillage system impacts on soil health and nitrogen dynamics. This way, his farmers can reap the benefits from improved soil health through increased yields and higher N availability, as estimated by Adapt-N.