What’s Cropping Up? Volume 30 No. 2 – March/April 2020 Now Available!

Statewide herbicide resistance screening to start in 2020: Help us to help you!

Lynn M Sosnoskie, Weed Ecology and Management for Specialty Crops
School of Integrative Plant Science – Horticulture Section

Weeds compete with crops for light, water, and nutrients, which can result in yield reductions. Weeds can also interfere with crop production by serving as alternate hosts for pests and pathogens, providing habitat for rodents, and impeding harvest operations. Consequently, growers employ a variety of control strategies, including the application of herbicides, to manage unwanted vegetation. Although herbicides can be extremely effective at controlling undesirable plants, failures can and do occur. Weeds may escape chemical treatments for many reasons including the evolution of herbicide resistance.

Worldwide, there are 512 confirmed cases (species x site of action) of herbicide resistance. With respect to the United States, 165 unique instances of resistance have been documented. In New York, there are only four formally reported occurrences; these include common lambsquarters (Chenopodium album), smooth pigweed (Amaranthus hybridus), common ragweed (Ambrosia artemisiifolia) and common groundsel (Senecio vulgaris). All were described as being insensitive to the photosystem II inhibitors (e.g. atrazine and simazine).

Chart showing herbicide resistance over time in the world
Current status of herbicide resistance, globally, over time according to the International Survey of Herbicide Resistant Weeds (weedscience.org)

This, however, does not reflect the current on-the-ground situation in the state; work done by Drs. Julie Kikkert (CCE) and Robin Bellinder (Cornell) indicates resistance to linuron in some populations of Powell amaranth (Amaranthus powelli). Recent studies by Drs. Bryan Brown (NYS IPM) and Antonio DiTommaso (Cornell) suggest that horseweed (Conyza canadensis) and waterhemp (Amaranthus tuberculatus) populations may be resistant to one or more herbicide active ingredients. Pennsylvania has nine reported cases of herbicide resistance including glyphosate resistance in Palmer amaranth (Amaranthus palmeri), which was recently identified here in NY. While it is tempting to believe that herbicide resistance is a hallmark of agronomic cropping systems, resistance can and has developed in orchards, vineyards, vegetable crops, pastures, and along roadsides.

Beginning in 2020, we will undertake a screening effort to describe the distribution of herbicide resistance in the state. This coming summer and fall, growers, crop consultants and allied industry personnel who suspect they have herbicide resistance are encouraged to contact Dr. Lynn Sosnoskie (lms438@cornell.edu, 315-787-2231) to arrange for weed seed collection. Indicators of possible herbicide resistance include:

    • Dead weeds intermixed with live plants of the same species.
    • A weed patch that occurs in the same place and continues to expand, yearly.
    • A field where many weed species are controlled but a previously susceptible species is not.
    • Reduced weed control that cannot be explained by skips, nozzle clogs, weather events, herbicide rate or adjuvant selection, and calibration or application issues.

Growers can take several actions to stop the spread of herbicide resistant weeds and to prevent the development of new ones. First and foremost is scouting fields following herbicide applications and keeping careful records of herbicide performance to quickly identify weed control failure. Pesticide applicators should ensure that their equipment is properly calibrated and that they are applying effective herbicides at appropriate rates to manage the target species. Whenever possible, diversify herbicides to reduce chemical selection pressures that result from the repeated use of a single herbicide or site of action. If possible, incorporate physical and cultural weed control practices into a vegetation management plan. Be sure to control unwanted plants when they are small and never allow escapes to set seed. Clean equipment to prevent seeds of herbicide-resistant weed species from moving between infested and non-infested sites and harvest areas with suspected resistant populations, last.

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Warm-Season Grass Binary Mixtures for Biomass in the Northeast

J.H. Cherney1, D.J.R. Cherney2, and M. Davis3
1Section of Soil & Crop Sciences, 2Dept. of Animal Science, Cornell University, and 3Farm Manager, Cornell Willsboro Research Farm, Willsboro, NY

Over five million acres of marginal agricultural land in the Northeast USA are no longer in use and have great opportunities for grass biomass production, although environmental or other supplemental compensation may be required for profitable production on low-yielding marginal land. Warm season grasses are considered a viable herbaceous second generation biofuel feedstock but are better suited to marginally productive cropland Future selection through breeding should have a significant focus on low-input types of environments.

Additional environmental benefits may accrue when mixtures are used instead of monocultures. Studies have suggested that polycultures sequester more carbon in the soil profile and have less N leaching compared to monocultures. Profitability in biomass production, however, is most strongly influenced by yield, and we focused on yield potential in this study.

Experimental layout

A long-term plot study was sown in 2010 in Ithaca (central NY, Williamson fine sandy loam soil) and Chazy (northern NY, Roundabout silt loam soil), and was completed in 2018. A goal was to determine if binary mixtures of warm-season grasses would result in increased yield over pure stands.

Three replicates of 12 treatments compared pure species with binary mixtures (Fig. 1). Binary mixtures had one species seeded in one direction, and the second species seeded perpendicular to the first. Pure species also were seeded twice, with one half the total seed sown perpendicular to the other half. Pure switchgrass and Atlantic coastal panic grass plots were seeded at 10 lbs pure live seed (PLS)/acre. Pure big bluestem plots were seeded at 12 lbs PLS/acre. Mixtures contained half the seeding rate of pure species plots for each species in a binary mixture. All entries were commercially available varieties, with the exception of RC Big Rock switchgrass, which was an experimental selection from Cave-In-Rock (REAP-Canada, Ste-Anne-de-Bellevue, QC). Insufficient seed was available of Timber switchgrass to seed at both sites.

Fig. 1. Plot layout at the two NY sites.

Plots (15’ x 15’) were fertilized with 50 lbs N fertilizer/acre at spring green up each year. Roundup was sprayed in the spring prior to warm season grass green up to control weeds after 2013. A few weeds were resistant to Roundup and remained, such as milkweed. Plots were well established by the 2013 growing season. Plots were harvested for yield determination each year in early October generally after first frost at a 4” stubble height using a flail harvester, harvesting 78 sq. ft. of plot area (3’ x 13’ twice per plot). Samples were collected for dry matter (DM) determination.


The more southern, generally wetter, Ithaca site averaged 22% greater yield across all years and species combinations. Ithaca long-term average precipitation is 4.5” per year more than Chazy (Plattsburgh, NY weather station), and Ithaca averaged 5.5” more per year during the experiment. Although Chazy is considerably farther north than Ithaca, long-term average heat units are very similar. Over the 2013-2017 period from May 1 to Oct. 1, both sites averaged 4916 GDD per growing season (base 32F). Warm season grass mixtures behaved differently on different sites. At Chazy, big bluestem (BB) tended to compete very well in mixtures with switchgrass (SW), while at the Ithaca site switchgrass tended to be the major component.

Big bluestem was the slowest species to become fully established, but Prairie View BB pure stands were the highest yielding at the Chazy site, averaged over five years. RC Big Rock switchgrass selection had the greatest yield in Ithaca for pure SW stands, averaging 6.6 tons DM/acre over 5 years. Cave-in-Rock SW (CAV) and the CAV-Prairie View BB mixture both yielded 13% less at Chazy than Ithaca, but pure Prairie View stands produced similar yields at both sites. Upland switchgrass mixed with Prairie View BB tended to produce the best overall results and was the most compatible mixture (Fig. 2). Other mixtures tended to become mostly monocultures over time.

Fig. 2. Average yields of pure switchgrasses (SW) vs. SW mixtures with big bluestem (BB).

Atlantic coastal panic grass (ACP) was promising the first year, but quickly deteriorated to a weak stand after the first year, and had significant weed invasion in later years, particularly at Chazy. BoMaster switchgrass struggled in pure stands and became a very minor component of mixtures. In later years, big bluestem and switchgrass tended to invade plots with weaker stands, as ripe seed was scattered each year during harvest with a flail harvester.


At both sites, mixtures of Cave-in-Rock SW and ACP quickly became pure switchgrass stands. By the end of the trial, mixtures of Cave-in-Rock and Suther BB were pure switchgrass at Ithaca, and averaged 10% BB at Chazy. BoMaster SW and ACP, as well as mixtures of these two, tended to be weak stands at both sites, with up to 25% weeds observed in the summer of 2018. Prairie View BB and BoMaster SW mixtures were essentially pure big bluestem stands in 2018 at both sites. Suther BB and Cave-in-Rock SW mixtures were pure switchgrass in Ithaca, and averaged 10% big bluestem in Chazy. Prairie View BB and Cave-in-Rock SW mixtures averaged 15% bluestem in Ithaca and 35% bluestem in Chazy, at the end of the trial.

Ground cover

Plots in Ithaca were observed for ground cover in the spring of 2018 (Fig. 3). The three replicates were very consistent in ground cover. Switchgrass provided the most ground cover early in the season, with RC Big Rock SW appearing to have the greatest ground cover. BoMaster was the weakest switchgrass, typically with weed infestations. Approximately 50% of the ground area was bare in BB plots, but open areas were generally free of weeds. Even less surface area was covered by ACP, and open areas tended to be infested with weeds annually. With the exception of ACP at both sites, and BoMaster SW at Chazy, other species and species combinations developed into a closed canopy by mid to late summer, regardless of the ground cover observed in spring.


The only mixtures with a significant contribution from both species were Prairie View BB and Cave-in-Rock SW mixtures. These mixtures had considerably more switchgrass at the Ithaca site compared to the Chazy site. Our results agree with other studies suggesting that species mixtures will be largely influenced by environmental variation. Results from a single location may not be applicable to other environments. Mixtures can improve yields mainly in the establishing years, with the potential for better yield stability over the life of the stands. Farmers should consider planting adapted cultivar mixtures of big bluestem and upland switchgrass for enhanced yield and yield stability. Improving seedling establishment of big bluestem should be an important breeding priority for more widespread adoption of this crop.


This work was supported by the USDA National Institute of Food and Agriculture, Multistate project 218756. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the National Institute of Food and Agriculture (NIFA) or the United States Department of Agriculture (USDA).

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2018 Corn Silage Hybrid Evaluation Results

Joe Lawrence, Allison Kerwin

The New York & Vermont Corn Silage Hybrid Evaluation Program continues to provide side by side evaluation of corn hybrids grown under a range of growing conditions representative of those experienced in the Northeast.  In 2018 the program evaluated 77 hybrids from 17 different seed brands.  Each hybrid was planted in replicated plots at 3 locations based on relative maturity (RM; Table 1).

The growing season was defined by below average precipitation and above average heat, measured as growing degree days (GDD) across trial locations (Figure 1). A defining difference between trial locations was the timing and amount of rainfall from late July to early September.  While all locations realized some level of improvement in growing conditions with more frequent rainfall in late July and August, its timing and impact on the crop varied. In general, rain arrived at all locations in time to facilitate normal pollination of the crop but ear development varied by location.

Figure 1. Rainfall and growing degree day accumulation by location and season for the NY & VT Corn Silage Hybrid Evaluation Program

The above average GDD accumulation throughout the season and particularly as the crop neared maturity resulted in fast dry down of the crop to target whole plant moisture content for silage harvest. A noticeable characteristic at harvest in many corn fields, including trial fields, was a healthy green plant with a dry ear.

While nutrient inputs at all locations met or exceeded crop needs, a lack of soil moisture may have compromised nutrient uptake at varying stages of crop development. Recognizing these real world influences and how a hybrid might perform under varying stressors is important to understand when evaluating this data.

The influence of growing conditions lead to location variability in hybrid performance in 2018 but overall better performance when compared to growing conditions experienced in 2017 (Figure 2).

Figure 2. Percentage of samples across all locations over a range of uNDF240 and starch levels by year for the NY & VT Corn Silage Hybrid Evaluation Program

The full report provides detailed data on individual hybrids entered into the program for 2018. The most significant parameters in the report vary by individual farm and that farms resources but some of the key data includes, yield, whole plant dry matter, starch content, measurements of fiber digestibility including neutral detergent fiber (NDF) digestibility at 30 hours (NDFD30) and undigested NDF at 240 hours (uNDF240), and predicted milk yields modeled in the Cornell Net Carbohydrate and Protein Synthesis (CNCPS) model.  The CNCPS model predicts the expected milk yield of different hybrids based on their inclusion into a high corn silage total mixed ration representative of the diets fed on many NY and Northeast dairy farms.

It is important to evaluate this data in the context of your farm when selecting hybrids. The top performing hybrid at any one location or in any one category may not be a good fit for your feeding program. Factors that influence this vary by farm but include land base, soil resources, forage inventory, quality of available hay crops, access and cost of supplemental ingredients, and expectations of cow performance.

The trial results and location averages serve as a means to calibrate hybrid performance to a particular growing season and these averages can be used in conjunction with a company’s data on hybrids in their lineup, including hybrids not entered into these trials, to understand how a hybrid performed relative to what is realistic for that growing season. For example, in Figure 2 we see that over 50% of samples taken in 2018 had an uNDF240 value between 9 and 10 so this can be used to evaluate how close and far away from these values other hybrids performed in 2018.  However, due to the challenging growing conditions experienced in 2017 and the impact of growing conditions on fiber digestibility we see that the highest percentage of samples in 2017 had a uNDF240 value of 13-14 while a very small percentage (less than 10%) of 2017 samples were as digestible as the majority of 2018 samples.  Therefore it would not be fair to hold hybrid fiber digestibility or other performance indicators from 2017 to the same standards as 2018.

It is also important to recognize the companies that make these trials possible through their entry of hybrids.  The following companies participated in the 2018 trials:

Albert Lea – Viking, Augusta Seed, Channel, CROPLAN, Dairyland, Dekalb, Doebler’s, Dyna-Gro, Growmark FS, Hubner, Local Seed Company, Masters Choice, Mycogen, Pioneer, Seedway, Syngenta – NK, Wolf River Valley

The full report of 2018 can be found at the Cornell Soil and Crop Sciences website:

Additional trial information can be found in the following article and webinar:

Article: 2018 Corn Silage Overview

Webinar: 2018 Corn Silage Hybrid Test Results, New York and Vermont Corn Silage Hybrid Tests – 2018

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What’s Cropping Up? Volume 28, Number 5 – November/December 2018

Feasibility Assessment of Dairy Biochar as a Value‐Added Potting Mix in Horticulture and Ornamental Gardening

Akio Enders a, John Gaunt a, b, Joshua Stone a, Leilah Krounbi a, Johannes Lehmann a, and Rajesh Chintala c

a Department of Soil and Crop Sciences, Cornell University, Ithaca, NY  14853

b GreenTree Garden Supply, Ithaca, NY  14850

c Innovation Center for U.S. Dairy

Total milk production in New York was 14,765 million pounds in 2016 (NYS Department of Agriculture and Markets, 2017). In 2018, New York State had the 3rd highest number of milk cows behind California and Wisconsin, with 625,000 cows (USDA NASS, 2018). Dairy manure excretion averages 12,821,616 tons per year in NY state alone (NYS Department of Agriculture and Markets, 2017; NRCS, 2018). This translates into 64,108 tons N, 38,465 tons P2O5, and 44,876 tons K2O (SARE, 2018) which can be recycled back for agricultural and horticultural use. In places where available manure nutrients exceed the needs of nearby field crops, the challenge becomes offsetting transportation costs. Unfortunately, these transportation costs can at times equal the manure’s value as a fertilizer (Pennington et al.).

Manure management generates 44% of total methane emissions on dairy farms (Wright et al., 2017). A more potent greenhouse gas than CO2 by 34-fold (Pronto et al., 2017), methane can be captured in anaerobic digesters for use as a fuel. Since 1998, 34 anaerobic digesters for dairy manure were installed and are operating across the state (EPA AGstar, 2018). These digesters facilitate a reduction in methane emissions by 1,502,327 MT CO2 equivalent units per year (EPA AGstar, 2018; Pronto et al., 2017).

Methane biogas is just one of the products generated in anaerobic digesters. The remaining digestate of wet reactors is comprised of partially-degraded biomass and nutrients, and contains up to 16% solids (Ward et al., 2008). Plant nutrients are concentrated by the microbial activity. Notably, ammonium nitrogen increases by up to 33% (Möller et al., 2008; Möller and Müller, 2012). The digestate slurry can screw-pressed to separate solids from liquids and recycled into useful products such as bedding or organic fertilizers. The solids can be further stabilized against decomposition through pyrolysis.

Heating under oxygen-free conditions, known as pyrolysis, converts biomass into a charcoal-like substance called biochar. During this process, carbon chains fuse into rings (McBeath et al., 2014). These substances resist decomposition in the soil, and can even slow the decomposition of non-biochar carbon (DeCiucies et al., 2018). As pyrolysis temperature increases, biochar surface area increases along with pH (Mukherjee et al., 2011). Generally speaking, pyrolysis concentrates plant nutrients when compared to the biomass feedstock (Enders et al., 2012).

This research project, sponsored by the U.S. Center for Dairy Innovation, enabled an assessment of upgrading anaerobically digested, screw-pressed dairy manure into a higher value biochar product. In summary, dairy manure biochar is an odor- and pathogen-free, nutrient-rich fertilizer with approximately twice the nutrient content of the original manure by mass, and more than three times that by volume. The nutrient value of the biochar as a substitute for other organic fertilizers was calculated as $240-340/ton. In addition, the carbon value as a substitute for commercially available biochar was calculated as $1580/ton. Analyses suggest that over half of the carbon in the resulting biochar is stabilized to benefit soil fertility and carbon sequestration for over a century after application.


Anaerobically digested, screw pressed, dairy manure was sourced from a 3000+ head New York dairy farm. Initial moisture content was 59%. After air drying to 12%, the feedstock was pyrolyzed at a highest temperature of 550 °C for 30 minute total residence time. Biochar yield was 38% of oven dry feedstock weight.

Biochar Basic Utility Properties and Toxicant Assessment were analyzed according to the International Biochar Initiative (IBI) Standard Product Testing Guidelines v 2.1. Total nutrient contents of feedstock and biochars were assessed to describe the effect of pyrolysis on plant nutrients. Transformations in nutrient availability of the manure and biochar were investigated with three extractants. Leachable nutrients were determined with a 0.01 M calcium chloride, available with a modified Morgan’s solution (ammonium acetate), and phosphorous with a fertilizer industry standard (2% citrate EDTA).

These data were used by our commercial partner, GreenTree Garden Supply, to substitute dairy manure biochar for all of the commercial biochar as well as a portion of fertilizer they use in three of their commercial growing media.

Basic Properties

The dairy manure biochar is 178% more dense than the manure at 503 lbs/cu yd, with ash content increased to 38%.

The IBI classification tool calculates the Carbon Storage Class of this biochar as 1, on a scale of 1-5 with 5 providing the highest carbon storage potential. This rating integrates both carbon quality and quantity. The high ash content of this biochar downplays the quality of the carbon present, hence the low rating. However, the quality of the carbon is such (i.e., low H/Corg ratio) that roughly half is expected to persist over 100 years, compared to practically 0% in the manure.

The pH of this biochar is 10.45. More importantly, it has a calcium carbonate equivalence of 3.30%. In other words, 100 pounds of biochar can neutralize acid as well as 3.30 pounds of lime. This falls under IBI Liming Class 1, rated on a scale of 0-3, with 3 relating to the highest lime equivalent. Therefore, this biochar is best suited for mildly acid soils that would benefit from increasing pH. Unlike biochar from biomass, this material possesses a moderate level of soluble salts with electrical conductivity (1:20 w:v) at 1.65 dS/m. For comparison, soil salinity begins to affect plant growth at levels over 2 dS/m.

The Fertilizer Class of this biochar, according to the IBI classification system, is 3 on a scale of 0-4. This is defined as providing adequate nutrition for corn at < 4.5 tons/acre provides for 3 out of 4 nutrients. Specifically, the calculation states that phosphorous, potassium, and magnesium requirements are met by application of 4.0, 1.3, and 1.3 tons/acre.

Toxicant Assessment

The IBI toxicant assessment is understandably quite stringent, screening for persistent organic pollutants:  polyaromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), dioxins (PCDD) and furans (PCDF); toxic heavy metals including:  arsenic, cadmium, chromium, lead, mercury; trace elements that become toxic at higher quantities including:  copper, molybdenum, nickel, selenium, and zinc; and phytotoxic elements including:  boron, chlorine, and sodium. The dairy manure biochar was non-toxic on all counts, and contained 30 times less than the threshold value for any single analyte. A germination trial also assessed biochar toxicity. Of the three species used (lettuce, ryegrass, and radish) germination in dairy manure biochar amended media was nearly identical to the control.

Total Nutrients

Biochar contained 4.1% P2O5, 2.2% K2O, and 4.4% MgO. Approximating from biochar yield, nutrient concentration in biochar could be as much 2.6x more than in manure. Gaseous losses during pyrolysis reduced the total content of plant nutrients in the biochar to 1.7x more than in manure feedstock. Sulfur is the most notable example where biochar contained 50% less than feedstock.

Available Nutrients

In addition to increasing total nutrient content, pyrolysis improved nutrient availability, exception for nitrogen and iron. The dairy manure biochar has a nitrogen content of 1.7%, however thermal treatment has converted this to plant unavailable forms and is therefore considered insignificant.

Biochar provided 13% more available phosphorous than the manure feedstock with 1.2% of biochar mass as P2O5, i.e. as would be printed on a fertilizer label. Interestingly, increased available phosphorous was coupled with a 10-fold decrease in leachable phosphorous.

The biochar also demonstrated 59% more available potassium than the manure with 1.6% of biochar mass as K2O.

Commercial Value

When all nutrient and carbon content is accounted for, the dairy manure biochar has a value between $0.91 – $0.96/lb (or $1,828-$1,912). This is calculation is based on the weighted average wholesale price for individual components in commercially available organic fertilizers as below. The majority of value, $0.79/lb, arises from the biochar carbon.

The product evaluation performed by GreenTree Garden Supply substituted all of the commercial biochar (80% C) with dairy manure biochar (43% C) on a carbon basis. The additional nutrient content in the dairy manure biochar reduced wholesale material cost for two products by 2.26% and 0.19%.

Future Outlook

A practical challenge to biochar production from manure is its moisture content. Waste heat from biogas combustion could fulfill this requirement, given the proper infrastructure. Additionally, pyrolysis coproduct gases could be upgraded and then co-fired alongside biogas for electricity generation to power on-farm pyrolysis. Biochar application to fields would increase fertility and offset nutrient inputs.

Organic farming is a feasible commercial application for dairy manure biochar. The biochar is cost competitive with other organic phosphorous sources and organic farmers are accustomed to spreading the larger bulk quantities as fertilizer. Additional fertilizer (especially N) would be blended with the biochar to achieve a desired nutrient balance and concentration and the final product would contain biochar to benefit soil fertility in the long term.

Ammonia gas lost from leachate ponds is another resource that can be utilized when biochar is introduced to the system. Biochar has proven effective in adsorbing both ammonium in solution and ammonia gas (Wang et al., 2016). This nitrogen loading can be enhanced with repeated exposure to CO2 to precipitate ammonium bicarbonate (Van Humbeck et al., 2014). Ammonium bicarbonate-biochar fertilizer has demonstrated greater efficiency than synthetic nitrogen alone (Mandal et al., 2016), however commercial production has not yet been achieved.


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Pennington, J.A., VanDevender, K., and Jennings, J.A., Nutrient and Fertilizer Value of Dairy Manure. University of Arkansas Division of Agriculture, Cooperative Extension Service, Agriculture and Natural Resources bulletin FSA4017.

Wright, P., Gooch, C. and Oliver, J.P., 2017. Estimating the Economic Value of the Greenhouse Gas Emission Reductions Associated with on-farm Dairy Manure Anaerobic Digestion Systems in New York State. In 2017 ASABE Annual International Meeting (pp. 1). American Society of Agricultural and Biological Engineers.

Pronto, J., Gooch, C., and Wright, P. 2017. Meeting New York State’s Energy, Environmental and Economic Goals While Strengthening Dairy Farms Through the Widespread Adoption of Manure‐Based Anaerobic Digestion Technology- Working Paper. Pro-Dairy program, Cornell University, Ithaca, NY p. 4. https://prodairy.cals.cornell.edu/sites/prodairy.cals.cornell.edu/files/shared/documents/ADworking_paper_Oct17.pdf (last accessed Oct 28, 2018)

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DeCiucies, S., Whitman, T., Woolf, D., Enders, A. and Lehmann, J., 2018. Priming mechanisms with additions of pyrogenic organic matter to soil. Geochimica et Cosmochimica Acta, 238, pp.329-342.

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Enders, A., Hanley, K., Whitman, T., Joseph, S., Lehmann, J., 2012. Characterization of biochars to evaluate recalcitrance and agronomic performance. Bioresource Technology, 114, pp.644-653.

Wang, B., Lehmann, J., Hanley, K., Hestrin, R. and Enders, A. (2016) Ammonium retention by oxidized biochars produced at different pyrolysis temperatures and residence times. Royal Society of Chemistry Advances, 6, pp.41907-41913.

Van Humbeck, J.F., McDonald, T.M., Jing, X., Wiers, B.M., Zhu, G. and Long, J.R., 2014. Ammonia capture in porous organic polymers densely functionalized with brønsted acid groups. Journal of the American Chemical Society, 136, pp.2432-2440.

Mandal, S., Thangarajan, R., Bolan, N.S., Sarkar, B., Khan, N., Ok, Y.S. and Naidu, R. (2016) Biochar-induced concomitant decrease in ammonia volatilization and increase in nitrogen use efficiency by wheat. Chemosphere, 142, pp.120-127.

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