Improving Soil Health with biochar and compost application in North Coast Vineyards

Progress report for FW21-386

Project Type: Farmer/Rancher
Funds awarded in 2021: $24,583.00
Projected End Date: 05/31/2024
Host Institution Award ID: G351-21-W8613
Grant Recipient: Treasury Wine EStates
Region: Western
State: California
Principal Investigator:
Dr. Michael Sipiora
Treasury Wine EStates
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Project Information

Abstract:

The use of biochar in agriculture has been considered to be a “win-win” proposition as it can improve agriculture sustainability by enhancing soil health while mitigating climate change via carbon sequestration in the soil (Filiberto and Gaunt, 2013). Even though biochar has been used in crop production for several decades, it has not been widely adopted due to inconsistent crop yield responses (Jeffery et al, 2011) and to several economic obstacles, including high costs and lack of a consistent return on investment (Bach et al, 2016; Filiberto and Gaunt, 2013). Recent trials on biochar application in vineyards have also shown inconsistent yield responses as well, with several reports of positive yield responses up to 50% during the first four years after application (Genesio et al 2015, Monterey 2021), while others report (Garcia-Jaramillo et al 2021) no positive yield response at all to biochar applications at two vineyard sites the year after application. Before biochar can be more widely adopted in vineyards in general, and in the North Coast of California in particular, there needs to be a better understanding whether biochar application may result in improved yields.

The lack of consistent yield response may be due to several factors including source of biochar feedstock material and processing, initial soil conditions, and crop (Guo, 2020). A recent meta-data analysis (Jefferey et al 2011) of previous biochar trials indicated that positive crop yield responses were more likely to occur on soils with an acidic or neutral pH or on soils with a coarse or medium texture, which suggests that the mechanisms for yield improvements that are the often observed include a liming effect on the soil or an improved water holding capacity with biochar applications. Indeed, biochar amendments will likely improve overall soil health (Guo, 2020) by improving soil physical (reduce bulk density, increase soil porosity and hydraulic conductivity, increase soil aggregate stability and available water holding capacity), chemical (reduce soil acidity, raise soil cation exchange capacity or CEC) and biological (increase available organic carbon and favorable habitat for microbial activity) characteristics of the soil.

Although Biochar amendments to soil alone may not lead to a positive yield increase for some crops, they can improve yield responses from inorganic (NPK) and organic fertilizer (Schulz and Glaser, 2012) due to improved nutrient retention as measured with higher CEC. Combining biochar and compost can lead to a synergistic response in plant growth and productivity (Fischer and Glaser 2012, Schulz and Glaser 2012). Therefore, even if a biochar application alone does not improve crop yield it may provide positive yield response if accompanied by compost addition.

The vineyards in the North Coast may require biochar or compost amendments. A recent trial (Wilson et al 2021) investigating the response of vineyards to compost applications in North Coast showed a positive yield response when rates were greater than 10 tons per acre. The soils in that trial were acidic and characterized as being degraded with very low concentrations of total carbon. The application of compost improved the carbon level significantly, raised CEC and soil pH, which was to be be anticipated with a biochar application. Therefore, there is a potential positive response in soil health and vineyard productivity to applications of biochar alone or in combination with a compost application in North Coast vineyards.     

A field trial has been undertaken comparing the application of biochar (at 10 tons per acre) to an application of compost (20 tons per acre) and an combined application of biochar and compost. These application were made in the fall of 2021. The impacts of these amendments on soil health, vine nutrient status, vine water status, vine yield and fruit composition will be determined during the next two vintages. A cost analysis and a break even analysis has been completed and the economic threshold for adoption of biochar applications in North Coast vineyards is lower than the threshold for field crops.

Project Objectives:

The first objective of this trial was to determine the impact of biochar and compost alone or in combination on soil health parameters in North Coast Soils utilizing both the Cornell Comprehensive Assessment of Soil Health (CASH) (Moebius-Clune et al., 2016) and the Haney Soil Health Tool (Haney et al 2018). The second objective was to determine if there is a potential yield increase due to an application of biochar, compost or a combination of both that would justify adoption of these practices in North Coast vineyards.

 

Objectives of the Trial. The specific objectives of the trial can be summarized as follows.

  1. To assess the potential for biochar and compost separately or in combination to improve soil health parameters of North Coast Vineyard soils.
  2. To assess the impact of biochar and compost application on vine nutrition.
  3. To assess the impact of biochar and compost application on vine growth and yield.
  4. To assess the potential impact of biochar and compost applications on the grape composition.
  5. To assess the potential economic return from applications of biochar and compost separately or in combination for vineyards in North Coast.
Timeline:
  Su 21 Fa 21 W 21 Spr 22 Su 22 Fa 22 W 22 Spr 23 Su 23 Fa 23 W 23 Spr 24 Su 24
Beginning of project (7/1/2021) x                        
Preparation of trial sites x                        
Compost/biochar applications   x                      
Initial soil sampling   x                      
1st Soil health workshop         x                
Follow up soil sampling               x          
2nd Soil Health workshop                 x        
Follow up soil sampling                       x  
Interpretation of results (white paper)                         x
Distribution of white paper                         x
End of project July 1st 2024                         x

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Miguel Garcia - Technical Advisor
  • Dr. Michael Sipiora - Producer

Research

Materials and methods:

Site: The vineyard site selected for this trial was located in Rutherford, CA. This vineyard has been in production since 1920 and there is a concern that prolonged farming of the soils at this site has led to degraded soil organic matter and carbon levels.  The vineyard block selected for the trial was replanted in 2018 to Cabernet Sauvignon clone 8 and 039-16 rootstock. No compost or biochar application have been made to this site during recent replant. The soils in the vineyard block are classified as a Bale Clay Loam with 0 to 2% slope (Fine-loamy, mixed, superactive, thermic Cumulic Ultic Haploxerolls) by USDA-NRCS web soil survey (Soil Survey Staff). The vineyard is being trained to a double cordon system with spur-pruning and formed on a vertically shoot positioned (VSP) trellis. Row spacing is 8 feet and vine spacing is 6 feet between vines.

Trial Layout. The trial was out in a randomized split plot design with 3 replicates, which will allow us to perform a statistical analysis on all the results. The main plots were biochar application versus no biochar (see Figure 1).

The sub plots were the application of compost or no compost. Each row contained 126 vines at a spacing of 6 feet between vines and 8 feet between rows, which is the equivalent of 0.13 acres. Each plot of 6 rows, therefore, is approximately 0.78 acres in size. The center 4 rows of each plot have been designated for data collection, leaving 2 buffer rows. The center data rows were delineated with GPS and a shapefile was generated using ArcMap. These shapefiles were shared with CERES imaging for aerial imaging of the plots (Figure 2). The plots are color coded: White (Control), Orange (Compost), Green (Biochar), and Blue (Biochar + Compost). The line posts in the vineyard have been painted with corresponding color to identify treatments in the field.

Layout of trial

Figure 1. Trial layout of biochar and compost applications.

Figure 2. Aerial view of trial layout.
Figure 2. Aerial view of trial layout.

Biochar and Compost Applications. The applications of both biochar and organic compost were completed on December 1st and 2nd in 2021. The biochar was sourced from Pacific Biochar in Santa Rosa, California. The biochar delivered came from Fortuna, CA and is made from softwood products. The compost was sourced from Jepson Prairie Organics located in Dixon, CA. The compost was made from yard waste and is registered organic by OMRI (Figure 3).

Both the compost and biochar were applied in the vineyard using a Whatcom Mulch spreader with a 5.5 cubic yard capacity.  These amendments were broadcast in the vineyard from the rear of the mulch spreader and covered the whole row, including the area under the vines (Figure 4). A full spreader (5.5 cubic yards) of biochar was applied for each vineyard row in main plots. Since each row was equivalent to 0.139 acres, the application rate resulted in 39.61 cubic yards per acre. The compost was spread at the same rate of 39.16 cubic yards per acre (Table 2).

Figure 3.
Fig 3. Delivery of biochar (left) and compost (right) to vineyard.
Figure 4 App
Fig. 4. Application of biochar in vineyard.

The man-hours to apply both the biochar and the compost were tracked for economic analysis. The total hours for biochar application was 6 man-hours and the total-hours for the compost application was 6.5 acres. The vineyard was also disced twice to incorporate amendments, with an addition 6 man-hours of direct labor hours.

Analysis of Compost and Biochar. A sample of both the biochar and compost was taken at delivery and sent to Soil Control Lab in Watsonville, California for analysis.

Soil Health Assessments

Soil samples were collected on May 4th, 2021, which was 7 months before application of biochar and compost, by the Napa Resource Conservation District staff. Each sample was a composite of several soil core taken from vineyard w middle in each treatment replication. The samples were mixed, and one subsample was sent the Oregon State soil laboratory for analysis following Cornell Framework for Comprehensive Assessment of Soil Health. The soil samples were analyzed for characteristics of physical (texture, wet aggregate stability), biological (organic matter, active carbon, soil respiration), and chemical properties (pH, CEC, extractable P and K) at the Oregon State Soil Laboratory following protocols in Cornell Framework for CASH (Moebius-Clune et al, 2016).

A second sub sample of the same soil samples that were collected on May 4th, 2021 by the Napa Resource Conservation District staff were sent to a commercial laboratory – Ward Laboratories in Kearney, Nebraska for soil health assessment using the Haney test (Haney et al, 2018). The Haney test involves an analysis of soil pH, soluble salts, and organic matter plus an analysis of total nitrogen, organic nitrogen, and total organic carbon from a water extract, an analysis of the concentration of mineral nutrients (NH4, NO3, P, K, CA, Mg, Al, Zn, Fe, Cu, Na, Mn) from a weak acid extract, and a 24-hour soil respiration (CO2-C in ppm) analysis with the Solvita test.

Plant Health, Vine Water Status and Yield

An initial (prior to application of biochar and compost) assessment of vine vigor was done on the individual plots with an NDVI (Normalized Vegetation Index) by CERES imaging on August 1, 2021. The NDVI data was calculated for each plot from central 4 vine rows with approximately 50 vines per row. The average NDVI and the distribution of individual vine NDVI was calculated for each plot prior to treatment by CERES Imaging.

The effects of amendments on plan nutrient status will be determined by analysis petiole samples during bloom of each growing season. Bloom time petioles were collected in June of 2021 and sent to A&L laboratories for analysis.

Measurements of plant water status will be performed at least three times during each season, to coincide with date of remote sensing flights, if possible.

Beginning in 2022, an analysis of yield parameters (kg per vine, clusters per vine, and average cluster weight) will be determined from 10 to 12 random vines within each treatment annually to determine if amendments had a impact on yield over the course of first three harvests after application.

Research results and discussion:

Analysis of Compost and Biochar. Comparing the analysis of biochar to compost (Table 1) showed that bulk density of biochar (19.1 lbs. per cubic foot) is close to half that of the compost (37 lbs. per cubic foot). This will be important for calculating tons per acre applied, since both were applied at the same cubic yard per acre rate.

Table 1. Results from Biochar and Compost Analysis

 

Biochar

Compost

Bulk Density (lbs./cu. ft)

19.1

37.0

Moisture (%)

67.8

36.8

Organic Matter (%)

-

32.7

Carbon (%)

27.7

17.0

Hydrogen (%)

0.7

-

Nitrogen (%)

0.2

1.1

Oxygen (%)

1.6

-

Ash (%)

1.9

30.7

TOTAL

100

100

C:N Ratio

139

15

 

The biochar also had a higher moisture content, a higher content of carbon and a much lower ash content than the compost. The biochar had a 5-fold lower content of nitrogen than the compost. The carbon-to-nitrogen ratio of the biochar was 139, while the carbon-to-nitrogen ratio for the compost was 15.3. Due to the very high C:N ratio of biochar, there is a concern that a biochar application will increase the C:N ratio of the soils after application.  The average C:N ratio of the soil in this vineyard is 11, which is considerably less than the C:N ratio of biochar, yet similar the C:N ratio of the compost. Future analysis of the soils should clarify any changes in the C:N ratio of the soils due to these applications.

Application Rates for Amendments and Carbon and Nutrients Applied.

Using the bulk density values for the biochar and compost, we were able to calculate the application rates in tons per acre (Table 2). The calculated application rate for the biochar was 10.21 tons per acre, which was slightly higher than targeted rate of 10 tons per acre. The calculate rate of application for the compost was 19.78 tons per acre, which was slightly less than the targeted 20 tons per acre. The combination of compost plus biochar was applied at 30 tons per acre (wet basis). The amount of carbon applied in the biochar only treatment was calculated to be 2.83 tons per acre. The amount carbon applied with the compost application was calculated to be slightly higher (3.36 tons per acre) than the amount in the biochar treatment (Table 2.). The carbon applied with the combined biochar and compost application was 6.19 tons per acre. An increase of at most 0.28% in soil C is expected with the biochar treatment and an increase of up to 0.34% is expected with the compost application. The combined biochar plus compost treatment has potential to raise C content of topsoil by 0.62%. Some losses are expected, and we expect to see actual C content of future soil samples to increase, but not as much as the calculated amounts. In addition, we expect the C concentration increases of soil samples to be more stable with the biochar applications than the compost application over time.

Table. 2. Bulk Density and application rates of Biochar and Compost and amount of Carbon and macronutrients applied per treatment.

 

Units

Biochar Application

Compost Application

Compost + Biochar

Bulk Density

 

 

 

 

 

lbs/cu ft

19

37

 

 

lbs/cu yd

516

999

 

Application Rates

 

 

 

 

 

cu yd/acre

              39.6

             39.6

 

 

lbs / acre

         20,428

        39,573

      60,002

 

tons / acre

           10.21

          19.79

        30.00

Carbon applied

%

              27.7

             17.0

 

 

tons / acre

              2.83

             3.36

          6.19

 

lbs /acre

           5,659

          6,727

      12,386

Estimated Soil C increase

 

0.28%

0.34%

0.62%

C:N Ratio

 

               139

                15

              26

Nutrients Applied

 

 

 

 

N

lbs/acre

                 41

              435

           476

P

lbs/acre

                  2  

                79

             81

P205

lbs/acre

                  5 

              178

            183

K

lbs/acre

                  9 

              257

           266

K20

lbs/acre

                 11 

              309

           320

 Biochar contains a small amount of nitrogen (0.2%) and the application of biochar resulted in an application of nitrogen of 41 lbs. per acre. The compost used in this trial had a five-fold higher concentration (1.1%) of nitrogen than the biochar used and since it was applied at twice the rate by weight, the amount of nitrogen applied per acre with the compost application was 435 lbs. per acre. The amount of nitrogen applied with the combined biochar and compost application was 476 lbs. per acre. Vineyards have a low nitrogen requirement compared to other crops. Under normal conditions, this vineyard receives an annual application of nitrogen between 20 and 40 lbs. per acre. Therefore, the nitrogen applied with biochar only would only be sufficient to supply approximately one year of nutrient program, while the compost application could theoretically supply 10 years’ worth of applied nutrients. There is some concern that the amount of nitrogen applied with compost is excessive and could lead to possible losses via leaching or nitrous oxide production. Biochar may be able to stabilize the nitrogen applied and will be evaluated with soil sampling.

 The phosphorus and potassium levels measured in the analysis of the biochar quite low (Table 2). The phosphorus and potassium levels in the compost were also analyzed (Table 2.) and the application of compost resulted in adding 79 lbs. per acre of P and 257 lbs. per acre of K in both the compost treatments.

Figure 5
Fig 5. Aspect of vineyard after application of biochar and compost. (White: control; Orange: compost; Green: biochar; Blue: biochar + compost).

SOIL HEALTH ASSESSMENTS

Initial Comprehensive Assessments of Soil Health (CASH).

The initial results show that the soil in this vineyard block has a uniform loam texture with 34% to 36% sand, 39% to 40% silt, and 24% to 26% clay content (Table 3). The water stable aggregate values for soil samples collected prior to biochar and compost application fluctuated somewhat between trial plots for 33 to 44%.  The soils also have both a uniform soil pH, cation exchange capacity (CEC) and soil Electrical Conductivity (Table 3). Biochar applications have been shown to increase soil pH and CEC both depending upon initial conditions (Garcia-Jaramillo et al 2021, Guo 2021, Schulz and Glaser, 2012) and there is interest in confirming potential impact of the treatments on these soil physical and chemical properties. The soil pH at this site is slightly alkaline and, therefore the liming effect of a biochar application may be minimal.

Table 3. Soil physical  (soil texture, water stable aggregate stability), chemical (Cation Exchange Capacity, pH, EC),  and biological (Organic Matter, Carbon, Active Carbon, Nitrogen, C:N ratio, and microbial respiration rates) parameters from CASH analysis of soils from plots prior to application of biochar and compost (May 2021).

 

Biochar + Compost

Biochar

Compost

Control

% Sand

34

35

36

35

Silt

40

39

40

40

Clay

26

25

24

25

Texture

loam

loam

loam

loam

Water stable aggregates (%)

33

44

37

39

pH

7.40

7.40

7.45

7.42

EC (dS/m)

0.19

0.18

0.27

0.21

CEC (meq/100g)

17

17

18

17

Org. Matter (%)

2.19

2.32

2.55

2.35

Total Carbon (%)

1.10

1.16

1.27

1.18

Total N (%)

0.12

0.11

0.13

0.11

C:N ratio

9.0

10.7

9.7

10.7

Active Carbon (ppm)

244

220

214

222

CO2 Respiration 24 hr  (µg CO2-C/g dry soil/day)

77

94

95

95

CO2 Respiration 96 hr  (µg CO2-C/g dry soil/day)

45

56

56

59

The CASH analysis from OSU lab also showed low, but uniform levels of carbon, nitrogen, organic matter, and active carbon, while soil respiration rates for soils in treatment plots 7 months prior to treatment were high (Table 3). The average total soil carbon ranged from 1.10% to 1.27 %. The biochar application was calculated to raise % carbon in this vineyard soil by 0.28%, the compost application could raise the soil carbon by 0.34%, and the biochar + compost treatment may raise soil carbon by 0.62%. The average percent nitrogen levels were also similar, ranging from 0.11% to 0.13% for samples from the different treatment plots. The compost applications may increase soil nitrogen levels, but by small amount on the order of 0.023% or less. The average carbon-to-nitrogen (C:N) ratio varied somewhat between plots. The average percent organic matter ranged from 2.2 to 2.5%. The 24-hour and 96-hour soil respiration rates were similar for all treatment plots, except possibly the biochar + compost plots, which were lower than the respiration rates in all the other plots .

This site was chosen since it has been in production since 1920 and the continuous farming of this vineyard since then has likely led to degradation of soil organic matter. Previous soil analysis indicated that soil organic matter was low at this site. In 2021, the Napa RCD collected an additional 24 samples from 4 other vineyard sites operated by Treasury Wine Estates for a CASH analysis. Comparison of the results from the other Treasury Wine Estates vineyard sites (Table 4) to the results from trial site that the soil at this trial site has a similar texture but a much lower wet aggregate stability and cation exchange capacity (CEC). The average levels of % carbon, % nitrogen, % organic matter, and active carbon confirmed the suspicion that this site had low levels of carbon (both total percent and active), organic matter, and nitrogen. The applications of both biochar and compost are likely to improve both water aggregate stability and CEC, which are important physical and chemical indicators of soil health. Interestingly, the soil respiration rates were slightly higher from this site compared to the average soil respiration rates form the other vineyard sites tested in 2021.

Table 4. Comparison of the CASH soil physical, chemical, and biological parameters at trial site to the averages from 4 other sites in Napa Valley (2021)

 

Trial Site

Average 4

Napa Sites (2021)

% of average

% Sand

35

40

88%

% Silt

40

36

111%

% Clay

25

24

104%

Texture

loam

loam

 

Water stable aggregates (%)

38

57

67%

pH

7.42

7.05

105%

EC (dS/m)

0.21

0.18

117%

CEC (meq/100g)

17

23

74%

Org. Matter (%)

2.35

4.05

58%

Total C (%)

1.18

2.02

58%

Total N (%)

0.12

0.18

67%

C:N ratio

10

11

91%

Active C (ppm)

225

348

65%

CO2 Respiration 24 hr    (µg CO2-C/g dry soil/day)

90

78

115%

CO2 Respiration 96 hr    (µg CO2-C/g dry soil/day)

54

51

106%

 

Initial Haney Soil Health Assessments

The results from the pre-application soil health assessment with the Haney test showed little variance in organic matter content (Table 5). The concentration of OM measured by loss on ignition was roughly 25% higher than the organic matter reported in the CASH (Table 5), which was determined by multiplying the total carbon (%) by 2. The water extractable organic carbon in these soil samples ranged from 85 ppm to 109 ppm (Table 5) and these values are about half of the amount of the active carbon levels observed in the CASH (Table 4). Both the active carbon from the CASH protocol and the water extractable carbon concentrations are used to assess the available carbon for microbes in the soil.  The average C:N ratio in the water extract was between 11 and 12 for the plots.

Table. 5. Results from Haney Soil test from plots prior to application of biochar and compost (May, 2021).

 

Biochar + Compost

Biochar

Compost

Control

Soil pH

7.47

7.40

7.47

7.43

EC (dS/m)

0.13

0.14

0.15

0.16

H3A Inorganic Nitrogen (ppm)

1.8

1.8

2.0

2.0

H3A Total Phosphorus (ppm)

48

40

50

44

H3A ICAP Potassium (ppm)

108

86

129

107

Organic Matter (% LOI)

2.90

2.83

2.93

2.90

Water Extractable Organic C (ppm)

95

109

85

96

Water Extractable Organic N (ppm)

9

11

8

8

Organic C: N

11

11

11

12

24-hr Respiration CO2-C (ppm)

56

76

71

77

% Microbial Active Carbon

59

70

85

80

Soil Health Score

8.4

10.9

9.6

10.4

The 24-hour respiration rates from the Haney test were slightly lower than the 24-hour respiration rate from the CASH. In both assessments, the 24-hour respiration rate in the biochar + compost plots were lower than in the other plots.  The percentage of the water extractable organic carbon (WEOC) that is respired in 24-hours is deemed the “% microbial active carbon” in the Haney test. The % microbial active carbon ranged on average from 59% to 85% (table 6) in the samples prior to treatment applications. There is keen interest in comparing the biochar and compost amendments influences on total carbon, microbial active carbon (active carbon or WEOC) and soil respiration rates in this trial as biochar is considered to be a more stable (Guo 2021, Schulz and Glaser, 2012) form of carbon in soils.

PLANT GROWTH AND NUTRITION

Plant Vegetation Growth prior to Biochar and Compost Applications.

The average NDVI values for treatment plots prior were very similar prior to application of biochar and compost (Table 6.). The results indicate that the grapevine vigor was on average the same for all the plots prior to application of biochar and compost.

Table 6. Average of Normalized Vegetation Index (NDVI) for plots in 2021 prior to application of biochar and compost (August 2021).

 

Biochar + Compost

Biochar

Compost

Control

Average NDVI

0.516

0.528

0.539

0.529

 
figure6
Fig 6. NDVI average a distribution curves for treatment plots from CERES aerial images.

Plant Nutrient Status Assessments.

     Bloom petiole samples were collected by Treasury Wine Estates viticulture team in late May. Approximately 25 petioles were taken from basal leaves opposite the flower clusters per plot. The samples were sent to a commercial lab (A & L Western Laboratories in Modesto, CA) for analysis. The results are provided in table 7.

Table 7. Grapevine bloom petiole nutrient contents in May 2021 prior to application of biochar and compost.

 

Biochar + Compost

Biochar

Compost

Control

Petiole N (%)

1.02

1.03

0.98

1.07

Petiole P (%)

0.31

0.32

0.33

0.31

Petiole K (%)

3.13

3.12

3.07

3.12

 Mg (%)

0.79

0.79

0.69

0.74

Ca (%)

2.04

2.11

2.03

2.08

B (ppm)

42

43

42

44

Zn (ppm)

51

52

49

50

There were no appreciable differences in plant nutrient status between the plots prior to treatment in any major nutrient (NPK) or micronutrient. Furthermore, the levels of N, P, and K encountered were in the normal to optimal range. The levels of Mg and Ca were slightly elevated, yet they are not a concern. And, the bloom petiole content of two critical micronutrients for grapevines (B and Zn) were in the normal to optimal range according to guidelines from local analytical lab. Based upon petiole analysis in 2021 there does not appear to be any nutrient deficiencies at this site that would require nutrient additions.

GRAPEVINE YIELD AND FRUIT COMPOSITION

The first year of yield data collection is scheduled for vintage 2022, which coincides with first year of production where grapevines in the trial block are fully established. Data of the number of clusters per vine, the average cluster weight and yield per vine will be collected near harvest. Data for fruit composition (Brix, pH, and titratable acidity) will also be collected in 2022 from cluster samples taken near harvest.

ECONOMIC ANALYSIS OF BIOCHAR AND COMPOST APPLICATIONS

There are some economic obstacles to widespread use of biochar in agriculture (Bach et al. 2016) including the lack of a consistent yield response with the applied biochar, the elevated costs of biochar, and the lack of positive economic returns for many crops even with increases in yield (Filiberto and Gaunt, 2013).            

Costs of Biochar and Compost Applications.

The actual cost per ton of the biochar used in this vineyard trial was $325.75 per ton and the total cost (material + labor) to apply the biochar was $3,406.93 per acre (Table 8). Previous economic evaluation of prior research on biochar applications (Filiberto and Gaunt, 2013) has reported that the average cost per ton for biochar to be $250 per ton, which is  lower than the cost for this trial. The cost of the compost application at 20 tons per acre was $1,131, 38 per acre. The cost of biochar for this trial was at least 6 time higher than the cost of compost per ton. The total cost of the biochar application was three time the total cost of the compost application, yet the total amount of carbon added to soil was 19% higher with compost application (Table 2). And, the total cost of the biochar plus compost application was $4,538.33 per acre (Table 8).

Table 8. Cost of Biochar and Compost Applications

 

Biochar

Compost

Biochar + Compost

Material Costs ($/acre)

             3,325.92

            1,025.98

            4,351.89

Labor Costs ($/acre)

                   81.03

                105.41

                186.43

Total Cost of Application ($/acre)

             3,406.94

            1,131.38

            4,538.33

Average Total Farming Costs Napa ($/acre/year) *

          11,871.00

          11,871.00

          11,871.00

Percent increase in Farming Costs

29%

10%

38%

* Kurtural et al (2020). Cost studies North Coast Vineyards

 

The University of California, Davis cooperative extension recently published cost study for farming Cabernet Sauvignon in Napa Valley in 2020 (Kurtural et al, 2020) and reported that the average annual total cash costs per acre is $ 11,871 per acre per year. The application costs of biochar in this trial would, therefore, increase total farming costs by 29% for one year, while the application of compost would increase farming costs by 10%, and the combined biochar + compost application would increase farming costs by 38% (Table 8). The onetime costs for soil amendments for vineyard redevelopment have been reported to be $870 per acre and the normal budgeted annual fertilization costs for North Coast vineyards is only $54 per acre per year (Kurtural et al 2020). The costs, therefore, of the treatments in this trial represent a much larger investment in vineyards than is normal for the region.

Break Even Analysis for Biochar and Compost Application

Even though the cost of biochar is high, especially compared to compost, the economic obstacles to adoption in wine grapes in Napa County should be much lower than the obstacles for other crops. Filiberto and Gaunt (2013) concluded that even with a sustained 10% yield increase of 10 years that the cost of biochar should be closer $70 per ton for an investment in biochar to break even for field crops such as corn, wheat, legumes, and vegetables, where annual gross revenue and net margins are small. Wine grapes are a high value crop compared to field crops and the economic obstacles to adoption are much lower. For example, a recent study with biochar applications in the Central Coast area of California (Sonoma Ecology, 2020) showed a positive return on investment after two year of production with biochar application costs at $2,000 per acre.

The breakeven analysis for this trial (Table 9) indicates that at the district average price of $7375.70 for Cabernet Sauvignon for vintage 2018 to 2020 that a yield increase of 0.46 tons (or 14% of average annual yield for Cabernet Sauvignon) is required in just one year to offset costs for biochar application; a yield increase of 0.15 tons (only 5% increase in average annual yield) for the compost application would be needed; and, a yield increase of 0.62 tons would be needed for the combined biochar and compost application to offset costs.  The adoption of biochar use in North Coast vineyards will likely depend upon prices of grape, which is dependent upon county or region and variety. For example, the average price of Cabernet Sauvignon (the major red varietal in Napa County) from 2018 to 2020 was more than twice the average price of Chardonnay i (the major white varietal n Napa County) during the same period (Table 9) and an investment in biochar at 10 tons per acre would, therefore, require a onetime annual yield increase of 30 – 40% or 1.14 to 1.52 tons per acre to justify investment. Likewise, the price of Cabernet Sauvignon varies greatly between regions in the North Coast. In 2020 the weighted average return per ton according to the 2020 grape crop report (CDFA, 2021) was $1,750 per ton in Mendocino county, $1,588 per ton in Lake county, $2,460 per ton in Sonoma county, and $6,261 per ton in Napa county. Due to large differences in grape prices and potential return per acre, adoption of biochar in North Coast vineyard use will not only be in response to potential yield increases, but by local crop prices for each varietal.

Table 9. Break Even Analysis for Biochar and Compost Applications to Napa Cabernet Sauvignon and Chardonnay vineyards

 

Biochar

Compost

Biochar + Compost

Cost Amendment ($)

3,406.94

1,131.38

4,538.33

Price Cabernet Sauvignon ($/ton) *

7,375.70

7,375.70

7,375.70

Yield increase (tons) to offset investment

0.46

0.15

0.62

Average 2018 to 2020 Yield Napa Cabernet Sauvignon (tons/acre) *

3.25

3.25

3.25

Yield increase Cabernet Sauvignon (%) to offset investment

14%

5%

19%

Price Napa Chardonnay ($/ton) *

2,993.70

2,993.70

2,993.70

Yield increase (tons) to offset investment

1.14

0.38

1.52

Average 2018 to 2020 Yield Napa Chardonnay (tons/acre) *

3.81

3.81

3.81

Yield increase Chardonnay (%) to offset investment

30%

10%

40%

* District average prices and yields for 2018 to 2020 vintages (Napa Crop Reports)

 

SARE 2021 report literature review

Participation Summary
1 Farmer participating in research

Educational & Outreach Activities

1 Consultations
1 On-farm demonstrations

Participation Summary:

Education/outreach description:

The first workshop is planned for the summer of 2022. The actual date has not been set.

Learning Outcomes

1 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.