Integrated rotation systems for soil borne disease, weed and fertility management in strawberry/vegetable production

Integrated rotation systems for soil borne disease, weed and fertility management in strawberry/vegetable production

Summary

Organic and conventional strawberry/vegetable producers in California face soilborne disease, nutrient and weed management challenges. To evaluate efficacy of anaerobic soil disinfestation (ASD), mustard cake application (MC) and broccoli residue incorporation, we initiated trials at two local farms with crop rotation (broccoli, cauliflower or fallow-strawberries-lettuce) as main plot treatments. Sub-plot treatments (ASD, MC, ASD+MC, untreated control and fumigant (conventional farm only)) were applied prior to strawberry planting. ASD+MC and ASD provided greater yield and soil inorganic N and lower Verticillium infestation in strawberries compared to MC and untreated control, but no treatment differences were found in weed density.

Objectives/Performance Targets

Objective 1:

Test the effects of ASD, broccoli residue incorporation, mustard cake (MC) application, alone and in combination, on crop yields, V. dahlia suppression, weed suppression, N provision, production costs and net returns in strawberries and lettuce grown in typical crop rotation systems on organic and conventional farms with high V. dahliae pressure. (Shennan, Muramoto, Koike, Klonsky, Milazzo, Tanimura, Noma and Kimes. Years 1-3, Santa Cruz, Salinas).

Objective 2:

We propose a series of additional experiments to optimize MC application procedures for improved yields, weed and disease suppression and N provision in strawberries and Romaine lettuce.

Specific goals are

1) to establish the optimum time between MC application and lettuce planting;
2) test the effects of MC application rate, depth of incorporation and level of preplant fertilizer on yields, disease and weed suppression in lettuce production;
3) as for goal 2 but for strawberries, and
4) assess the economic feasibility of MC use in lettuce and strawberries. (Shennan, Muramoto, Koike, Klonsky, Pedersen and Kimes. Years 1-3, Watsonville).

Objective 3:

To disseminate results to growers and agricultural professionals in coastal California through a field demonstration (at a NGO farm that works with low-resource Hispanic organic farmers), field trips, YouTube, eOrganic and written materials (All team members. Years 2 and 3).

Accomplishments/Milestones

1.1 Santa Cruz Site

A field trial was established at the UCSC organic farm (Elkhorn sandy loam) and baseline soil samples were taken on 6/15/2011. Prior to the trial, a legume/cereal mixed cover crop was grown during the winter and mowed and disked in the spring. Based on a preliminary V. dahliae population test (5 microsclerotia/gram soil), the site with the highest baseline V. dahliae population was selected. A replicated split-plot experiment with three-year crop rotations was initiated: 1) broccoli-strawberries- lettuce, 2) cauliflower-strawberries-lettuce and 3) fallow-strawberries-lettuce as main plots, and anaerobic soil disinfestation (ASD), mustard cake (MC. Brassica juncea: Sinapis alba,1:1 by weight), ASD plus MC and untreated control (UTC) as sub-plots. In the main treatments broccoli serves as a “suppressive crop” whereas cauliflower is neutral in terms of V. dahliae since it lacks the effective glucosinolate profile found in broccoli.

Broccoli (cv. Gypsy) and cauliflower (cv. Snow crown) were transplanted in designated plots on 6/16/2011. Fallow plots were kept bare and cultivated periodically to suppress weeds. Broccoli and cauliflower were harvested at maturity from 8/15/11 till 8/31/11 (six times) and aboveground biomass was sampled on 8/15/11 and 8/31/11. The broccoli and cauliflower residues were flail mowed on 8/31/11, soil samples for V. dahliae (0-6” depth) and inorganic N (0-6” and 6-12” depth) tests taken on 9/1/11, and residues incorporated into the soil on 9/2/11.

On 9/20/11, strawberry beds were listed and soil samples (post-broccoli incorporation /pre-ASD treatment) were taken. Split plot treatments were established on 9/21/11 as follows; for the ASD treatment, 9 t/A of rice bran was applied to the bed surface and rototilled to 6” depth. For the mustard treatment, MC was applied at 1.5 t/A and incorporated into 6” of the bed, then covered with plastic mulch. For the ASD + MC treatment, 7.5 t/A of rice bran and 1.5 t/A of MC (total 9 t/A) were applied and incorporated in the same manner. Drip tapes were laid and plastic mulch applied on the same day at all plots. Drip irrigation was applied to ASD and ASD+MC plots on 9/26, 9/27 and 10/10 (total 4.3 ac-in) to maintain soil water above field capacity. Post-ASD/MC treatment soil samples were taken on 10/31/11. Strawberry plants (cv. Albion) were transplanted into all plots on 11/16/11 (Image 1).

Strawberry fruits from a harvest station with 20-marked plants at each plot were harvested and weighed for marketable and unmarketable fruits twice per week from 4/9 to 9/27/12 (Image 2). Strawberry biomass samples were taken on 1/10, 2/24, 4/20 and 9/28/12. Degree of plant wilt level was visually evaluated for plants in the harvest station on 5/29, 7/16 and 9/6/12 using subjective scores as follows: 1 = healthy plant, 2 = moderately stunted, 3 = moderately stunted and slight outer rosette of dead leaves, 4 = moderately stunted and moderate outer rosette of dead leaves, 5 = significantly stunted and slight outer rosette of dead leaves, 6 = significantly stunted and moderate outer rosette of dead leaves, 7 = significantly stunted and significant rosette of dead leaves and 8 = dead plant. Four plant samples were taken on 9/27/12 and tested for Verticillium dahliae infestation. Soil samples for inorganic N monitoring (0-6” and 6-12” depth) were taken on 12/2/11, 1/17/12, 2/22/12, 4/13/12, 6/20/12, 8/7/12 and 10/4/12. Topsoil samples taken on 10/4/12 will be tested for viable V. dahliae population as well. A clear plastic window (1m x 0.5m) for weed density measurement was created in each plot on 12/12/12, and the weed sampling was done on 1/30, 2/24, 4/5, 5/17 and 8/2 in 2012. In addition, weeding time for bed area was measured for each plot on 1/30, 4/5, 5/17 and 8/2/12.

At the end of the strawberry season, plants were mowed and the field carefully disked and spring tooth cultivated to maintain integrity of each plot. A mixed cover crop (45% bell beans, 45% purple vetch, 10% AGS104 rye) was direct sown in all plots at a rate of 300 lbs/A on 11/6/12. Soil samples were taken for inorganic N (0-6” and 6-12” depth) on 12/13/12.

Work left to do for this trial includes harvesting, mowing and incorporating cover crops in March-April 2013, growing lettuce in May-July 2013, yield survey of cover crop and lettuce, soil inorganic N monitoring, total N analysis of plant samples, estimation of N loss during the winter rainy seasons, soil Verticillium test and economic analysis.

1.2 Salinas Site

A similar field trial was established in a conventional field (Pacheco clay loam; a V. dahliae count of 12 microsclerotia/gram soil) in Salinas, CA. The experimental design was the same as the UCSC site except for an additional fumigation split plot. Baseline soil samples were taken on 6/9/11. Broccoli (cv. Patron) was direct seeded and cauliflower (cv. Absolute) transplanted to assigned plots on 6/21. On 8/24, biomass of broccoli and cauliflower and soils (0-6”, 6-12’ depths) were sampled. Broccoli and cauliflower were mowed and incorporated before plants reached full maturity due to conflicts with land preparation for the following strawberry crop. Strawberry beds were listed and soil samples (post-broccoli incorporation/pre-ASD treatment) were taken on 9/16/11. On the same day, ASD, MC and ASD+MC split plots were established as for the UCSC site. Drip tapes were laid and plastic mulch applied on 9/17/11. Drip irrigation was applied to ASD and ASD+MC plots on 9/28, 9/30, 10/8 and 10/17 (total 3.2 ac-in). Fumigation with PicChlor 60 was drip applied to fumigation plots on 10/2/11. Post-treatment soil samples for V. dahliae (0-6” depth) and inorganic N (0-6” and 6-12” depths) tests were taken on 10/25/11. Strawberry plants (cv. Monterey) were transplanted to all plots on 11/11/11 (Image 3). Strawberry biomass samples were taken on 1/6, 2/17, 4/6 and 10/19/12. Strawberry fruits were harvested and weighed from 4/30 to 7/30/12 (twice weekly), twice in August, and then terminated due to the labor shortage of the collaborating grower. Thus the yield data reflect the early yield over a three-month period. Degree of plant wilt level was visually evaluated for plants in the harvest station on 10/19/12 as described previously. A weed observation window was established in each plot on 12/19/11, and weed samplings were done on 2/10, 3/9, 5/4, 6/12 and 7/25/12. Weeding time was measured on 2/10, 5/4, 6/12 and 7/25/12. To monitor soil inorganic N dynamics, samples (0-6” and 6-12” depths) were taken on 11/22/11, 1/5/12, 2/15/12, 4/6/12, 5/18/12, 7/25/12 and 10/12/12. Topsoil from 10/12/12 will be tested for viable V. dahliae populations.

The original plan was to plant lettuce to each plot in spring 2013. However, the grower notified us that it is impossible to maintain the integrity of these small plots (each plot is one 3’ wide bed x 40’ long) with their large farming equipment. Therefore, the trial was terminated as of October 2012.

Work left to do for this trial includes total N analysis of plant samples, estimation of N loss during the winter rainy season, a part of soil Verticillium test and economic analysis.

2.1 Mustard Cake Plant Back Time Trial for Transplanting Romaine Lettuce

A replicated field trial was established in an organic farm (Arnold loamy sand) in Watsonville, CA. A split-split plot experiment with four replicates was initiated: mustard cake (MC. Brassica juncea: Sinapis alba,1:1 by weight) 1,000 lbs/acre, MC 2,000 lbs/acre, and pelleted organic fertilizer (OF. Perfect Blend 4-4-2. Chicken manure-based) 1,000 lbs/acre (grower’s standard) as main plots; plant back periods of 1, 2, 3 and 4 weeks as split plots; and with and without plastic mulch (clear TIF film) as split-split plots. Each plot was 4’ x 5’. On 3/14/12, after taking soil samples (0”-6” depth) for inorganic N analysis, MC and OF were applied to assigned plots, incorporated into ~1” depth with rakes, and a half of each plot was covered by clear TIF film for the four week treatment. The process was repeated on 3/22 for the three week treatment, on 3/28 for the two week treatment, and on 4/4 for the one week treatment. On 4/11/12, after removing the plastic mulch, weed density was counted, soil samples for inorganic N analysis were taken, and 12 Romaine lettuce transplants (cv. Salvius) were planted at 10” spacing at each plot. Weekly weed density monitoring was continued until 5/16/12. A 1,000 lbs/acre of OF was top dressed on 5/7/12 and 12 gallons/acre of AgroThrive LF (2.5-2.5-1.5) was sprinkler applied on 5/22/12 to all plots as in-season N applications. On 5/30/12, eight mature Romaine lettuce plants in the middle of each plot were harvested and fresh biomass measured. To evaluate residual inorganic N, soil samples (0”-6” depth) were taken on 5/31/12.

2.2 Work Left To be Done

Based on the results of the trial in 2.1 above, to further optimize MC application method for Romaine lettuce we will conduct a replicated trial with MC application rate (0, 1,000 and 2,000 lbs/acre) as a variable. The same type of MC rate trial for strawberries will also be conducted. Economic analysis of MC application will be preformed.

3.1 Demonstration trial at ALBA

A non-replicated demonstration trial (0.1 acre) with the same design with the Santa Cruz trial in Objective 1.1 was established at ALBA, Salinas in 2012. Prior to establishing the trial, tomatoes were planted at the site to increase Verticillium dahliae population. Broccoli and cauliflower were grown on 1/3 of the site in summer 2012 as main plots. After harvest, crop residues from broccoli and cauliflower were mowed and incorporated. Split plots of ASD, MC, ASD+MC and UTC were created as described in 1.1 before transplanting strawberries. Strawberries (cv. Albion) were transplanted to all plots on 11/13/12.

A wooden sign in Spanish explaining the goals, approaches and funding sources of the trial will be established at the demo site in January 2013. Strawberry fruit yield from each plot will be monitored throughout the harvest season in 2013.

3.2 Other outreach activities accomplished and to be done

We gave a poster presentation on soil inorganic N status and the early fruit yield from the rotation trials in 1.1 and 1.2 at the 2nd International Organic Fruit Research Symposium, June 18-21, 2012 at Leavenworth, Washington (see attached poster). Updated data from the project will be presented at academic meetings and outreach meetings, conferences, workshops and webinars in 2013 and 2014. Research papers and outreach pamphlet on the integrated approach will also be published. Surveys on potential adoption of developed practices by regional growers will be conducted along with outreach meetings/workshops.

• Image 2. The Santa Cruz trial at UCSC organic farm (4/27/2012).
• Image 3. The Salinas trial. Top: main plot; broccoli (B), cauliflower (C), and fallow (F) (6/18/11-8/29/11). Bottom: strawberries (11/11/11-10/12/12). Sub plots, mustard cake (MC); 1.5 tons/acre, anaerobic soil disinfestation (ASD) using 9 tons/acre of rice bran, ASD with 7.5 tons/acre of rice bran + 1.5 tons/acre of MC (ASD+MC), untreated check (UTC), and fumigant (Pic-Clor 60) were randomly assigned to each bed of each main plot. 4 replicates.
• Image 1. The Santa Cruz trial at UCSC organic farm. Top: main plot; broccoli (B), cauliflower (C), and fallow (F) (6/16/11-8/31/11). Bottom: strawberries (11/16/11-10/4/12). Sub plot; mustard cake (MC); plot 2, 5, 10, 16, 18, 21, 28, 31, 33, 40, 44, and 47. ASD; plot 3, 8, 9, 14, 19, 24, 27, 30, 36, 39, 43, and 46. ASD+MC; plot 1, 7, 12, 15, 17, 23, 25, 32, 34, 38, 41, and 48. UTC; plot 4, 6, 11, 13, 20, 22, 26, 29, 35, 37, 42, and 45.

Impacts and Contributions/Outcomes

1.1 Santa Cruz Site

Broccoli and cauliflower grew well; head yield and residue biomass (stems+leaves fresh weight) of broccoli averaged 6.4 ton/ac and 13.7 tons/ac, respectively, and of cauliflower 4.2 ton/ac and 16.8 tons/ac, respectively. There was no difference in yield (P=0.80) and residue biomass (P=0.29) between sub plots.

From December 2011 to Januar 2012, salt burn damage on strawberry leaves was observed in all plots but slightly higher in MC (data not shown). In February, plant biomass was highest at ASD and lowest at MC (P=0.007**). In April, ASD, ASD+MC and MC had greater biomass than UTC (P=0.0007***). Some plants started to show wilt symptom in May and the symptom progressed as plants became senescent. At the end of the season, UTC had the highest wilt score and ASD the lowest (P=0.043*). This coincided with the plants from UTC having higher V. dahliae infestation rates than ASD and ASD+MC (P=0.006**. Fig.1). No differences in biomass, wilt scores and V. dahliae infestation rate were found between main plots (broccoli, cauliflower or fallow in preceding year). Throughout the harvest season, fruit yield was higher in ASD+MC and ASD treatments than UTC and MC (Fig. 2a). Cumulative marketable fruit yield was greatest in ASD+MC (averaged 862 g/plant), followed by ASD (781 g/plant), MC (646 g/plant), and lowest for UTC (618 g/plant) (P=0.0001***, Fig. 2b). There was no difference in cumulative marketable fruit yield between main plots (P=0.58).

Viable V. dahliae microsclerotia population in topsoil prior to the strawberry planting was rather low: it averaged 1.5 per gram soil at pre-ASD/MC application. At post-ASD/MC application, viable V. dahliae microsclerotia was completely eliminated by ASD and ASD+MC, whereas it was 0.3 to 0.5 for MC and UTC (P=0.15. Table 1). Results of viable V. dahliae microsclerotia population in topsoil at the end of the strawberry season is pending.

About 20 mg/kg of soil NO3-N was detected at the beginning of the trial. By harvest in September, broccoli and cauliflower had depleted NO3-N at both depths, whereas in fallow plots the initial NO3-N level remained (Fig. 3a-d). As crop residues were incorporated (9/2/11) and rice bran and MC applied (9/21/11), soil inorganic N in the topsoil rapidly increased and peaked in November to December when NO3-N and NH4-N reached 60-120 mg/kg and 10-30 mg/kg, respectively. The NO3-N peak in December was highest for fallow, followed by broccoli and cauliflower for main plots (P=0.007** Fig. 3a). For sub-plots, it was highest in ASD+MC, followed by ASD, MC and UTC (P<0.0001*** Fig. 3c). After that, soil inorganic N concentration gradually decreased at all plots regardless of treatment. Soil inorganic N dynamics at ASD, ASD+MC and MC showed rapid mineralization of rice bran (ASD plots) and MC within two to three months from incorporation (Fig. 3c (topsoil) and 3d (subsoil)).

The high NO3-N concentration in December to January raised soil salinity and caused salt burn to the strawberry plants, a widespread phenomenon in the region including our Salinas trial (Fig. 5 and 6) due to the dry and warm winter. Cauliflower residues appeared to be decomposed and release inorganic N faster than broccoli residues; NO3-N in cauliflower plots peaked in November versus December for the broccoli plots (Fig 3a). Weed density was measured in the observation window created in the strawberry beds from January to August 2012. Cauliflower plots had less weed density than broccoli and fallow plots (P=0.046), but no difference was found between subplots (P=0.17. Fig. 4).

1.2 Salinas Site

Broccoli and cauliflower grew well, but the grower decided to mow and incorporate before plants reached full maturity due to conflicts with land preparation for the following strawberry crop. Fresh biomass of broccoli and cauliflower was 16.2 tons/acre for both crops.

Strawberries experienced rather severe salt burn damage in December to January due to the dry and warm winter and resulting high soil EC (Image 4). Damage was especially severe in ASD and ASD+MC plots where soil EC exceeded the threshold for salt sensitive crops such as strawberries (Fig. 5).

Cumulative marketable fruit yield of strawberries in ASD+MC and ASD treatments was similar to Pic-Clor, and ASD+MC and Pic-Clor had a significantly higher yield than UTC and MC (P=0.01*. Fig.6). No difference in marketable yield was found between main plots (P=0.58).

Baseline viable V. dahliae microsclerotia in topsoil averaged 16 per gram soil. At broccoli/cauliflower harvest, the number decreased to 5.5. It dropped to 0.46 pre-ASD/MC, due probably to dilution with subsoil after chiseling. The count was further decreased to 0.1 after ASD/MC treatment, and no difference was found between any treatment (P>0.12). V. dahliae microsclerotia counts for soil samples from the end of strawberry season is in progress. At the end of the season (10/19/12), the plant wilt score averaged 3.3, much lower than the 4.8 found at the Santa Cruz site; no differences were observed between plots (P>0.22).

Soil inorganic N dynamics showed a similar pattern as at the Santa Cruz site, but overall inorganic N concentration was much higher due to pre-plant chemical fertilizer application (Fig. 7). After broccoli and cauliflower residue incorporation and ASD/MC application in September, nitrate concentration peaked in December at 70-150 mg/kg in 0”-6” depth and in January at 70-100 mg/kg in 6”-12” depth in the clayloam soil. Significant differences in both main plots (P<0.05) and subplots (P<0.001) were observed in December, indicating N mineralization from crop residues, rice bran and MC was greatest about three months after incorporation. Pic-Clor appears to have slowed down nitrification rate in the topsoil: with 20-40 mg/kg of NH4-N from December 11 until April 2012, a much higher level than all other plots (P<0.001 in January), and only 30-40 mg/kg of NO3-N from September to February, much lower than other plots including UTC (Fig. 7c).

Generally weed density in the Salinas site (Fig. 8) was about 1/10 of the Santa Cruz site (Fig. 4). Pic-Clor had lower weed density compared to all other plots (P=0.002. Fig.8). Main plot treatments did not have any effect on weed density (P=0.22).

Overall, ASD+MC and ASD produced similar fruit yields as Pic-Clor at the Salinas site. ASD+MC produced greater fruit yield than UTC and MC at both sites and ASD at the Santa Cruz site. The yield of ASD and ASD+MC in the Salinas site may, however, have been reduced by the salt damage during early growth. On the other hand, ASD and ASD+MC produced excessively high amounts of inorganic N in the soil two to three months after application. N input reduction from the carbon source used for ASD and modifications to preplant N warrant further study. At both sites, when strawberries were transplanted, Verticillium dahliae population in soil was not as high as expected. However, V. dahliae infestation on strawberry plants at the end of the harvest season in the Santa Cruz site was reduce by ASD and ASD+MC (Fig. 1) suggesting that the mechanisms of yield increase by ASD involves disease suppression. Other studies indicate that ASD increases total soil bacteria and fungal populations which may enhance soilborne pathogen suppression due to a highly competitive environment. Weed suppression by ASD and MC appears to be limited. Interestingly, ASD and ASD+MC lowered weed densities more in fallow plots in both sites (Fig. 4 and 8). The effect of broccoli rotation and MC application in V. dahliae and weed suppression was limited in this study. No synergistic effect of broccoli rotation with ASD and MC was observed. This may be partially due to the unexpectedly low Verticillium pressure of the trial sites.

2.1 Mustard Cake Plant Back Time Trial for Transplanting Romine Lettuce

Lettuce head weight in the MC 1 t/ac treatment was higher than grower’s standard, but 0.5 t/ac was not (P=0.05. Fig. 9). Use of clear TIF increased lettuce head weight (P<0.0001***. Fig. 9). More specifically, when used with TIF, a three-week plant back time yielded higher head weight than one week at 1 t/ac rate (P=0.047*), though for 0.5 t/ac rate one week seemed sufficient (P=0.52). Without TIF, however, there was no difference in head weight between any plant back time period indicating even one week is sufficient. Lettuce head weight of MC-applied plots showed a positive linear correlation with inorganic N content in the topsoil on the transplanting day (R2=0.243***. n=62). This suggests that besides MC phytotoxicity, the optimum plant back time was strongly affected by the amount of mineralized N from MC at the time of transplanting. Although MC 1 t/ac with TIF and three-week plant back time produced the highest head weight, the price of lettuce versus costs of MC and TIF need to be considered to determine the most cost effective option.

MC application did not show any effect on weed density of either monocots or dicots sampled from 4/11/12 to 5/16/12 regardless of application rate, use of TIF or not, and plant back period (P>0.10).

• Fig. 4. Weed density (# of weeds/0.5 m2) at the Santa Cruz site for the period Jan. to Aug. 2012. Statistical analysis was performed for log-transformed data. Bar shows mean ± SEM (n=4) of the original data.
• Image 4. Photos of salt burn damaged strawberry plants in the Salinas site in Jan. 2012.
• Fig. 5. Electrical conductivity (1:1 v/v method) of topsoil at the Salinas site in Jan. 2012. Each bar indicates mean ± SEM (n=4). The dotted line indicates the threshold for strawberries above which crop yield could be reduced.
• Fig. 6. Cumulative marketable fruit yield at the Salinas site. Bars shows mean ± SEM (n=4).
• Fig. 7. Inorganic N dynamics in soil of the Salinas trial. a) Main plots in 0”-6” depth, b) Main plots in 6”-12” depth, c) subplots in 0”-6” depth, and d) subplots in 6”-12” depth.
• Fig. 8. Weed density (# of weeds/0.5 m2) at the Salinas site during Feb. and July 2012. Statistical analysis was performed for log-transformed data. Bar shows mean ± SEM (n=4) of the original data.
• Fig. 9. Lettuce fresh head weight at the mustard cake plant back time trial, Watsonville, CA. Main plots are GSt: Grower’s standard method using commercial peletted organic fertilizer, .5t/ac, and 1 t/ac of mustard cake (MC). Split plots are 1, 2, 3, and 4 weeks of plant back time. Split-split plots are No cover: without plastic mulch, and Cover: with clear TIF film. Treatments with the same letter within main plots, split plots, or split-split plots do not have significant difference by Tukey’s HSD test (P=0.05). Each bar shows mean ± SEM (n=4).
• Fig. 1. Verticillium dahliae infestation rate of strawberry plants sampled on 9/27/12 at the Santa Cruz site. Each bar indicates mean ± SEM (n=4). Infestation rate (%) = # of infested plants/4 plants tested x 100.
• Fig. 2a. Marketable fruit yield at the Santa Cruz site. Cumulative marketable fruit yield in subplots. Treatments with the same letter are not significantly different (Tukey’s HSD test (P=0.05)).
• Fig. 2b. Marketable fruit yield at the Santa Cruz site. Total marketable fruit yield. Each bar indicates mean ± SEM (n=4).
• Table 1. Verticillium dahliae microsclerotia population in the topsoil of the Santa Cruz site.
• Fig. 3. Soil inorganic N dynamics at the Santa Cruz trial. a) Main plots 0”-6” depth, b) Main plots in 6”-12”, c) subplots 0”-6”, and d) subplots 6”-12”.

Collaborators: