Evaluating the effects of green manure and biofertilizers on pak choi yield, minerals, and phytonutrient contents

Final report for GNE15-096

Project Type: Graduate Student
Funds awarded in 2015: $14,994.00
Projected End Date: 12/31/2016
Grant Recipient: UMES
Region: Northeast
State: Maryland
Graduate Student:
Faculty Advisor:
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Project Information

Summary:

Demographics on the Delmarva Peninsula are becoming more diverse; hence, the need for small farmers to capitalize on this trend and diversify crop offerings. The goal of this project is to provide research-based production practices for high-yielding ethnic crops that can be grown on Delmarva. Two preliminary greenhouse studies were conducted to select elite sustainable fertilizers, which was used to conduct two field studies.  During summer and fall of 2016, three field studies were conducted at the University of Maryland Eastern Shore (UMES) Agricultural Experiment station, to examine yield of Brassica rapa cv. Bonsai Chinensis (pak choi). During the summer study, two varieties of pak choi (Joi Choi F1 and Mei Qing Choi F1) were planted at different times during the growing season (early summer and late summer, respectively) at two separate locations in a complete randomized design with six fertilizer treatments ((1) Control (20:20:20), (2) Vermicompost Tea and Fish Emulsion (VCT+FE), (3) Poultry Litter Leachate (PLL), (4) Control + Azospirillum (Azo), (5) VCT+FE+Azo, and (6) PLL+Azo), with four replications each.  Fertilizer treatments were applied biweekly throughout the growing season. During the fall study, one pak choi variety was planted in a complete randomized design with two treatments ((1) Control and (2) Green Manure Tea) and four replications each. Pak choy was harvested at the mature stage and yield, essential trace elements (cobalt, chromium, copper, zinc, iron, nickel, and manganese), and phytonutrients (total phenolic contents, total flavonoid contents, and antioxidant capacity) were analyzed. There was no significant difference between the control and treatments for each study, which indicates that either treatment can be used to produce a quality yield.  Cobalt and iron was significantly different among VCT + FE + Azo, PLL + Azo, and VCT + FE. Total phenolic contents were significantly different among the treatments but was not significantly different to the control. Control+Azo significantly increased total phenolic contents compared to the control alone. The results from the studies suggest that all the sustainable fertilizer treatments have the ability to produce high-yielding nutritious pak choy and may be used as alternative fertilizer for growing ethnic crops on the Delmarva Peninsula.

Introduction:

The Delmarva Peninsula on the East Coast of the United States is occupied by all of Delaware and the eastern portions of Maryland and Virginia. According to the Local Eastern Shore Sustainable Organic Network (2016), the majority of the agricultural production for these three states takes place on the Delmarva. The population in Delaware, Maryland, and Virginia is highly diverse and continues to increase. Between 2000 and 2010, the total population within these three states have increased from 13,158,600 to 14,672,500. In 2010, Native Americans, Asians, African Americans, Hispanics, and Caucasians experienced percentage increase in population, 280, 84, 20.7, 94, and 7.8 percent, respectively (U.S. census, 2010). This increase in ethnic diversity has increased the amount of ethnic foods consumed in the United States. 

Economic opportunities have arisen for specialty crop production catering to the ethnically diverse consumers along the eastern coast of the United States (Govindasamy et al., 2007). This increased demand for locally grown food provides opportunities for small farmers, on the Delmarva Peninsula, to grow specialty crops to serve the increasing local ethnic markets, sustain farming operations, and diversify crop offerings, which can create new markets with higher profit potential than tradition crops (Robert Myers, 2000).  However, cropping on the Delmarva is constrained by sandy soils that are mainly acidic and low in plant nutrients. The region is prone to high temperatures and periodic drought conditions during the growing season, which results in low yield production and low farm income (USDA, 2012). Therefore, this research seeks analyze the growth and development of ethnic crop varieties that can be grown and/or adapted to the Delmarva environment.

Project Objectives:

Objectives/Performance Targets

  1. Investigate the use of green manure and biofertilizers on the growth and development of bok choy.
  2. Evaluate the use of green manure and biofertilizers to increase minerals and phytonutrients contents in bok choy.

Cooperators

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  • Dr. Byungrok Min - Technical Advisor (Educator)
  • Dr. Ali Ishaque - Technical Advisor (Researcher)

Research

Materials and methods:

Materials and Methods

Greenhouse Study One.  During fall 2015 a preliminary biofertilizer study was conducted at the University of Maryland Eastern Shore (UMES) Agricultural Experiment Station to identify elite biofertilizer(s) to use in the pak choi field experiments. The study was conducted in a greenhouse in a complete randomized design with seven treatments (Endo/Ectomycorrhizae, Azospirillum, Trichoderma, Endo/Ectomycorrhizae + Trichoderma, Azospirillum + Trichoderma, Endo/Ectomycorrhizae + Azospirillum, Endo/Ectomycorrhizae + Azospirillum + Trichoderma) and the control, with four replicates each.  Pro-mix with Mycorrhizae was inoculated with the biofertilizer treatments according to the manufacturer’s instructions for all treatments. Inoculated potting mix was placed into 6’ pots and two pak choi seeds were planted in each. One seedling was removed 5 days after germination; leaving one plant per replicate. Plants were watered when needed and fertilized with 500 ml of 20:20:20 foliar fertilizer once per week. After 3 weeks, the plants were transferred to 2.5 gallon pots fill with inoculated potting mix. Four weeks later plant were harvested, leaf yield was collected and recorded. Roots were placed to dry for 96 hours at 70 ºC and the dry weight collected. Data was recorded and analyzed statistically.

Greenhouse Study Two:  During fall 2015 a preliminary study was conducted to identify elite organic fertilizer(s) to use in the pak choi field experiments. The study was conducted in a greenhouse in a complete randomized design with nine treatments ((1) chemical fertilizer (control), (2) Veteran Compost vermicompost tea, (3) Wiggle Worm Soil Builder vermicompost tea, (4) Alaska fish emulsion, (5) Neptune's harvest fish emulsion, (6) Veteran Compost vermicompost tea  + Alaska fish emulsion, (7) Veteran Compost vermicompost tea + Neptune's Harvest fish emulsion, (8) Wiggle Worm Soil Builder vermicompost tea + Alaska fish emulsion, and (9) Wiggle Worm Soil Builder vermicompost tea + Neptune's Harvest fish emulsion), with four replications each. Two bok choy seeds were planted into 4 1/2 inches pots filled with Promix with Mycorrhizae. One plant was removed from the pot one week after germination. Ten days after planting, plants were treated with 100 ml of foliar applied fertilizer treatments. Treatment concentrations were mixed according to manufacturer's instruction. Treatments were applied 2 weeks after germination and once every week thereafter until harvesting. At three weeks plants, were transplanted into larger pots. Plants were harvested at the maturity stage (7-8 weeks after planting). Fresh weight and root dry weight were analyzed statistically.

 

Field Study One:  Two field studies, conducted at two separate locations at the UMES Agricultural Experiment Station, were conducted from May to September of 2016 to investigate the use of six fertilizer treatments on the growth and development of two varieties of pak choi. Mei Qing Choi (variety # 1) was planted in the early summer (June 10th to July 14th) and the Joi Choi (variety # 2) was planted in the late summer (August 4th to September 8th). Three weeks after harvesting Mei Qing Choi, Joi Choi was planted in the same location with the same treatments. The experimental design was a complete randomized design with six treatments ((1) Control (20:20:20), (2) Vermicompost Tea and Fish Emulsion (VCT+FE), (3) Poultry Litter Leachate (PLL), (4) Control + Azospirillum (Azo), (5) VCT+FE+Azo, and (6) PLL+Azo), with four replications each. Each plot consisted of three 1.5 m x 5 m rows with 1 m between each row and 2 m between plots. For each treatment, 18 seedlings were planted (6 seedlings per row) at approximately 6 inches apart. Seedlings were treated with 100 ml of each treatment one week before transplanting in the field, and 400 ml once every two weeks after transplanting.  Yield was collected at the mature stage and fresh weight was recorded and analyzed statistically.

**Due to cool wet weather during the beginning of the experiment, the cowpeas for the green manure treatment did not germinate well so this treatment had to be replaced with the Poultry Litter Leachate (PLL), which was a readily available organic fertilizer obtained from another study being conducted at the UMES Agricultural Experiment Station.

Field Study Two:  Joi Choi seedlings were germinated in the greenhouse and transplanted in the field during fall 2016 (October 26th to December 14th) using a complete randomized design with two treatments, (1) Control (20:20:20) and (2) cowpea green manure tea. Each plot consisted of three 1.5 m x 5 m rows/raised beds with 1 m between each row and 2 m between plots. For each treatment, 18 seedlings were planted (6 seedlings per row) at approximately 6 inches apart. Green manure plots were treated with 400 ml cowpea green manure tea and the control plots were treated with 400 ml 20:20:20 once every two weeks after transplanting. Pak choi was harvested at the mature stage. Fresh weight was recorded and analyzed statistically.

Sub-sample: 24-45 g of the harvested plant material from each field study (replicated treatments) was removed, chopped up, freeze dried, and analyzed for essential trace elements and phytonutrients.

Essential Trace Elements Analysis: The concentrations of essential trace elements, manganese (Mn), copper (Cu), cobalt (Co), chromium (Cr), zinc (Zn),  iron (Fe), nickel (Ni), and selenium (Se), were determined in pak choi samples from each field study. CEM-MARS 6 one touch microwave oven was used for microwave-assisted acid digestion. Approximately 0.5 g of ground freeze dry samples were weighed and transferred to CEM-Xpress vessels and 10 ml of concentrated nitric acid (HNO3) was added to each sample. The samples were pre-digested for 15 minutes at 1000 W with 100% level. A 25 minutes ramping period was used to reach the digestion temperature of 180°C. After digestion, the CEM-Xpress vessels were cooled and the pressure released under fume hood. The contents were transferred to a 50 ml centrifuge tube and distilled water was added to bring it up to 50 ml. Diluted samples were analyzed using ICP (Induction Coupled Plasma). The ICP data was divided into low and medium to high concentrations and statistically analyzed.

Phytonutrients Analysis: Total phenolics, total flavonoids and antioxidant capacity were analyzed using the freeze dried samples from replicate of each treatment, by extracting 0.2 g in 5 ml of 80% methanol (MeOH). The samples were placed horizontally on a platform shaker (Inova 2000, New Brunswick Scientific, Edison, NJ) at 300 rpm for 2 hours at room temperature. The samples were centrifuge at 15000 x g at 4 ⁰C for 10 minutes. Supernatant was transferred to 15 ml polypropylene test tube. Another 5 ml of 80% MeOH was added to the pellet. Pellet with MeOH was shaken, centrifuge again, and the supernatant added to the first supernatant. Supernatant volume was increased to 10 ml by adding 80 % MeOH. The reconstitutes were stored in the freezer for evaluation. All data was reported based on dry weight. Total phenolic contents (TPC) and total flavonoid contents (TFC) were evaluated using a spectrophotometer at 760 and 510 nm, respectively. Calculation for TPC was conducted using the equation [(A- intercept)/slope]*dilution factor*(10)*(1/0.2)/1000 mg gallic acid equivalent (GAE)/g sample. Where A is absorbance, 170.12 is the molecular weight of the gallic acid, 10 is the extract volume and 0.2 is the actual weight of the sample. TFC was calculated using the same equation except the molecular weight for gallic acid was replace with the molecular weight of catechin (CE). Antioxidant capacity was evaluated by Tecan Infinite 200 microplate plate reader (Durham NC) using Oxygen Radical Absorbance Capacity (ORAC) hydrophillic the area under the curve (AUC) was calculated for ORAC. Data obtained from these analysis were analyzed statistically.

Data Analysis:  All treatments were analyzed and compared to the control using Statisix 9. Analysis of variance (ANOVA) and Tukey’s HSD test.

Research results and discussion:

Greenhouse Study One:  Result showed that all seven treatments produce lower leaf yield when compared to the control. Trichoderma + Azospirillum, Trichoderma + Azospirillum + Endo/Ectomycorrhizae, and Endo/Ectomycorrhizae + Azospirillum produced significantly lower yields, whereas the others were not significantly different from the control. Pro-mix with mycorrhizae by itself (Control) produce higher yield (Table 1). There was a significant difference in root dry weight among treatments. Trichoderma + Azospirillum had the highest root dry weight when compared to the other treatments (Table 2). Therefore, it is a possibility that this result is affected by competition among microorganisms. The three treatments that have produce significantly lower yield than the control showed that they all are a combination of Endo/Ectomycorrhizae. However, Endo/Ectomycorrhizae by itself showed no significant difference when compared to control. Azospirillum had a higher yield than the other treatments (Table 1); therefore, it was selected as the elite biofertilizer to use in the 2016 field studies.

Table 1. Pak Choi Yield

Treatments

Yield (g)*

Control

385.13   a

Endo/Ectomycorrhizae

270.28   ab

Azospirillum

307.75   ab

Trichoderma

257.68   ab

Trichoderma + Endo/Ectomycorrhizae

  28.08   c

Trichoderma + Azospirillum

299.33   ab

Endo/Ectomycorrhizae + Azospirillum

252.78   ab

Trichoderma + Endo/Ectomycorrhizae +Azospirillum

190.63   b

*Means (n=4) followed by the same letters are not significantly different according to Tukey's HSD test at 5% probability.

 

Table 2. Pak Choi Root Dry Weight

Treatments

Dry Weight (g)*

Control

0.8000    ab

Endo/Ectomycorrhizae

0.3500    ab

Azospirillum

0.7750    ab

Trichoderma

0.5750    ab

Trichoderma + Endo/Ectomycorrhizae

0.0520    b

Trichoderma + Azospirillum

1.1250    a

Endo/Ectomycorrhizae + Azospirillum

0.6500    ab

Trichoderma + Endo/Ectomycorrhizae +Azospirillum

0.4250    b

 

*Means (n=4) followed by the same letters are not significantly different according to Tukey's HSD test at 5% probability.

 Discussion:  Potting mix does not have a wealth of nutrients to sustain plant life to the maturity stage; therefore, in greenhouse crop production, fertilizers are used to enhance crop yield. Trichoderma and Endo/Ectomycorrhizae are beneficial microorganisms known to colonize the rhizosphere or the interior of the plant, suppress diseases, and promotes its growth by increasing the supply or availability of primary nutrients to the host plant (Aseri et al., 2008; Wu et al., 2005; Mahfauz and Sharaf-Eldin, 2007). However, if the growth medium lacks nutrients then the biofertilizers cannot increase the availability of nutrients to the plants. Azospirillum are beneficial microorganisms that have nitrogen fixation, nitrogen assimilation, nitrogen regulation, and antagonistic properties (Steenhoudt and Vanderleyden, 2000; El-Hamshary et al., 2010). The commercial potting mix used in the study already contained mycorrhiza. Trichoderma, Endo/Ectomycorrhizae, and Azospirillum added as biofertilizer treatments, therefore increasing the number of organisms in the growth medium, which may have caused competition among the organisms and lowered crop yield. For example, the Trichoderma + Endo/Ectomycorrhizae treatment had the lowest yield and Trichoderma + Endo/Ectomycorrhizae + Azospirillum treatment had the second lowest yield; however, the Azospirillum treatment (nitrogen fixation) alone produced the second highest yield and the Trichoderma + Azospirillum treatment produced the third highest yield (Table 1). Hence, Azospirillum was able to supply the plants with the required nutrients, for this reason Azospirillum was considered to have the best characterized genus of plant growth-promoting rhizobacteria (Steenhoudt and Vanderleyden, 2000), and was chosen at the elite biofertilizer to use in the field studies.

Greenhouse Study Two:  Results showed that the chemical fertilizer (control) was significantly (P≤ 0.05) different among all the organic fertilizers except for the Veteran Compost vermicompost tea + Alaska fish emulsion treatment. Veteran Compost vermicompost tea + Alaska fish emulsion had the highest yield compared to the other organic treatments (Table 3); therefore, it was selected as the elite organic fertilizers to use in the field studies.

Table 3. Pak Choi Yield

Treatments

Leaf Weight (g)

Control (20:20:20)

445.40 a*

Veteran Compost vermicompost tea

85.60 e

Wiggle Worm Soil Builder vermicompost tea

291.75 c

Alaska fish emulsion

129.35 d

Neptune's harvest fish emulsion

247.53 c

Veteran Compost vermicompost tea  + Alaska fish emulsion

379.5 ab

Veteran Compost vermicompost tea + Neptune's Harvest fish emulsion

247.53 c

Wiggle Worm Soil Builder vermicompost tea + Alaska fish emulsion

247.05 c

Wiggle Worm Soil Builder vermicompost tea + Neptune's Harvest fish emulsion

268.10 c

*Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability

Discussion:  The components of Vermicompost Tea (VCT) are thought to increase crop yield and improve plant health, and nutritional quality by providing plants with substantial amount of soluble mineral nutrients that readily available to plant (Hargeaves et al., 2008; Pant et al., 2009). However, in this study VCT by itself produced a significantly lower pak choi yield when compared to the other treatments. This finding is consistent with that of Lazcano et al. (2008), who found that some vermicompost tea lowered the yield of ryegrass. However, when VCT was combined with fish emulsions (FE), the pak choi yield increased significantly. Fish emulsions decompose rapidly in soil producing C: N ration between 4:4.7 and plant available nitrogen of about 50% in 7 days, which will increase to 60% at 28 days after application (Gale et al., 2006). Commercial FE is enhanced with fulvic acid and chelating to make minerals more bio-available for plant absorption, which may have contributed to the increase in yield (Wyatt and McGourty, 1990). When FE is applied via foliar application it has the ability to supply supplemental doses of mineral nutrients, plant hormones, stimulants, and other beneficial substances (Kuepper, 2003).  As a result of the greenhouse study, VCT+FE was selected as the elite organic fertilizer to use in the field studies.

 Field Study One: Results showed that yield data varied among treatments and locations for the early summer study; however, there was no significant difference among treatments (Table 4).  For the early summer study at location 1, the Poultry Litter Leachate produced the highest average yield of 2.025 Kg, whereas the Vermicompost Tea + Fish Emulsion + Azospirillum produced the lowest average yield of 0.7375 Kg when compared to yield produced by other treatments. All sustainable fertilizer treatments at location 1 produced higher yields than the chemical fertilizer. However, at location 2, the chemical fertilizer treatment produced the highest yield (5.4625 Kg) when compared to the sustainable fertilizer treatments (Table 4). Pak Choi yield also varied among treatments in the late summer study at both locations (Table 5); however, there was no significant difference (P≤0.05) among the treatments. The Chemical Fertilizer + Azospirillum treatment produced the highest yield at both locations (4.1750 Kg and 8.8500 Kg, respectively) when compared to the other treatments. Location 1 produced the lowest yield when compared to location 2 in both the early and late summer Pak Choi studies.

Field Study Two: There was no significant difference (P≤0.05) among the Control and Cowpea Green Manure treatments for the fall study (Table 6).

Table 4. Early Summer Pak Choi Yield for Locations 1 and 2

 

 

Treatments

 

Location #1

Yield (Kg)

 

Location #2

 Yield (Kg)

1. Control (20:20:20)

 

1.2625 a*

 

5.4625 a*

2. Vermicompost Tea + Fish Emulsion

1.7750 a

4.3000 a

3. Poultry Litter Leachate

2.0250 a

4.0375 a

4. Control + Azospirillum

1.6875 a

4.6900 a

5. Vermicompost Tea + Fish Emulsion + Azospirillum

0.7375 a

4.2875 a

6. Poultry Litter Leachate + Azospirillum

1.6750 a

4.8375 a

*Mean (n=4) separation by Tukey's HSD test at 5% (ANOVA Table 4). Numbers having the

same letters are not significantly different.

 

Table 5. Late Summer Pak Choi Yield for Locations 1 and 2

 

Treatments

 

Location #1

Yield (Kg)

 

Location #2

 Yield (Kg)

 

1. Control (20:20:20)

 

3.4000 a*

 

8.1125 a*

2. Vermicompost Tea + Fish Emulsion

3.7000 a

8.1750 a

3. Poultry Leachate Liquid

3.3500 a

6.8250 a

4. Control + Azospirillum

4.1750 a

8.8500 a

5. Vermicompost Tea + Fish Emulsion + Azospirillum

3.5125 a

8.5375 a

6. Poultry Litter Leachate + Azospirillum

3.3500 a

7.3375 a

*Mean (n=4) separation by Tukey's HSD test at 5% (ANOVA Table 4). Numbers having the same letters are not significantly different.

 

Table 6. Fall Pak Choi Yield

Treatments

Yield (Kg)

 

Control (20:20:20)

0.9625 a*

 

Cowpea Green Manure

0.9500 a

 

*Mean (n=4) separation by Tukey's HSD test at 5% (ANOVA Table 4). Numbers having the same letters are not significantly different

Discussion (Field Study One & Two):  There was no significant difference among treatments for all three studies. Yield of pak choi varied among treatments, locations, and varieties. Pak choi grown at location 1 produced lower yields when compared to location 2.  This may have resulted from a number of edaphic factors such as soil type, soil health, soil nutrients, soil pH, and soil topography. At location 1 the soil was sandy, acidic, and lower in plant nutrients and biological activities. The land was flat, which makes it susceptible to flooding. During the growing season, location 1 was covered with water despite the use of raised beds. At location 2, the soil was clay-loam and had a higher level of biological activity, was rich in nutrients, and less acidic than location 1. Sandy soil readily leaches plant nutrients and cause the soil to become more acid, which can affect the growth and development of plant (Mendel and Kirkby, 2012). The Mei Qing pak choi variety produced a lower yield compared to the Joi Choi variety in both locations. This finding is consistent with that of Radovich et al. (2013) who conduct a study using seven pak choi varieties including Joi Choi and Mei Qing. Joi Choi variety was found to produce a significantly different weight compared to Mei Qing.

In the fall study, the cowpea green manure treatment produced similar yield (0.95 Kg) to the chemical fertilizer (0.963 Kg). Green manure, when incorporated in soil, improves of soil fertility, increase the number of soil microorganisms and their activities, increase farm production, suppress weed and disease infestation, and improve crop quality (Hirpa, 2013). Joi Choi produced a lower yield during the fall when compared to the control in the late summer study. The control in both the late summer study and the fall study was the same treatment and same variety, but was planted in a different location with different climatic condition. Pak choi is a cool-season crop and was expected to produce similar yield to the late summer study. However, the yield produced in the fall study is consistent with the Joi Choi variety grown by Radovich et al. (2013) in the fall, which averaged 0.348 and 0.34 lbs per plant, respectively.

Essential Trace Elements Analysis:  Essential trace elements varied among the treatments at both locations for the early summer and fall studies. At location 1, the control treatment contained significantly higher amounts of cobalt than the VCT+FE+Azo and PLL+Azo treatments. There were no other significant differences among the treatments for essential trace elements at location 1. However, control had the highest amount (µg g-1) in five (Co, Cr, Fe, Mn, and Se) of the eight essential trace elements measured compared to all other treatments. Whereas the VCT+FE treatment had the highest µg g-1 of Cu and Ni compared to their counterparts and the PLL+Azo treatment had the highest amount of Zn (µg g-1) when compared to all other treatments (Figure 1 and 2). At location 2, the PLL+Azo treatment produced the highest amount (µg g-1) of Mn, Co, and Cr, while the Control+Azo treatment produced the most µg g-1 for Fe, Ni, and Se, where Fe was significantly different to the VCT+FE treatment, but it was not significantly different from the other treatments. VCT+FE+Azo had the highest µg g-1 of Zn when compared to the other treatments (Figure 3 and 4). There were no significant differences (P≤0.05) among the treatments in the green manure study. Green manure tea produced a higher µg g-1 of Co, Cu, Fe, and Se than the control, While Zn, Mn, Cr, and Ni was higher in the control than the green manure treatment (Figure 5 and 6).

 

 

Figure 1. Early summer study (location 1) low concentration essential trace elements
Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability.
Figure 2. Early summer study (location 1) medium and high concentration essential trace elements. Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability.
Figure 3. Early summer study (location 2) low concentration essential trace elements
Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability
Figure 4. Early summer study (location 2) medium and high concentration essential trace elements. Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability.
Figure 5. Green manure tea study low concentration essential trace elements
Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability
Figure 6. Green manure tea study medium and high concentration essential trace elements. Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability.

Discussion:  Essential trace elements are minerals that our bodies require in minute amounts for the certain processes such as metabolism, nutrients and vitamin absorption, and digestion. Essential trace elements are the co-factors or tools that make everything happen in the body. These essential trace elements include iron, manganese, copper, zinc, chromium, cobalt, manganese, nickel, and selenium. However, these essential trace elements have been found to decline in fruits and vegetables due to modern farming methods, which have stripped the soil of it mineral contents (Lairon, 2010). Studies have shown the decline in food nutrient is attributed to chemical fertilizer usage (Lairon, 2012; Howard et al., 2002; White and Broadley, 2005). However, results from this study is inconsistence with those findings.  This study showed that the amount of essential trace elements in the pak choi varied among treatments, locations, and variety. Six of the eight essential trace elements were not significantly different from the control. Of the two essential trace elements that showed significant difference, one was attributed to the chemical fertilizer treatment and the other to the chemical + Azospirillum treatment. The chemical fertilizer treatment increased the amount of cobalt and iron significantly compared to VCT + FE + Azo and PLL + Azo treatments, while the chemical fertilizer + Azospirillum treatment significantly increased iron compared to VCT + FE treatment.

Phytonutrients Analysis: Phytonutrients were not significantly (P≤0.05) affected across the treatments for the two pak choi varieties at location 1. The control treatment had the highest level of total phenolic contents and antioxidant capacity when compared to the other treatments. The Control+Azo treatment had the highest level of total flavonoid contents when compared to all other treatments. VCT+FE significantly increased (P≤0.05) the levels of total phenolic content when compared to PLL, but it was not significantly different from the other treatments in the early summer study at location 2 (Table 7). However, the Control+Azo treatment produced the highest levels of total phenolic content and antioxidant capacity compared to all the other treatments. The level of phytonutrients also varied among the treatments in both locations of the late summer study. Treatments did not significantly affect the levels of phytonutrients analyzed in location 1 of the late summer study. While the levels of total phenolic content, total flavonoid content, and antioxidant capacity were higher in the VCT+FE+Azo, PLL, and Control+Azo treatments, respectively, when compared to other treatments (Table 7). At location 2 of the late summer study, the levels of total phenolic content, total flavonoid content, and antioxidant capacity were higher in all the sustainable fertilizer treatments compared to the control. The Control+Azo treatment significantly (P≤0.05) increased the levels of total phenolic content compared to control but was not significantly (P≤0.05) different among the other sustainable fertilizers (Table 7). There were no significant difference among the treatments used in the green manure study for phytonutrients; however, the Cowpea Green Manure treatment produced a higher level of total phenolic contents, total flavonoid contents, and antioxidant capacity compared to the Control (Table 7).

 

Table 7. Effect of Sustainable Fertilizers on Phytonutrients in Three Pak Choi Studies

Treatments

Total Phenolic Contents

(mg GAE/g sample dry weight)

Total Flavonoid Contents

(mg CE/g sample dry weight)

Antioxidant Capacity (ORAC)

(umol TE/g sample dry weight)

 

Early Summer Study (Location 1)

 

Control

260.12  a

1.85  a

7.77  a

VCT + FE

186.11  a

1.12  a

5.37  a

PLL

213.81  a

1.43  a

6.27  a

Control + Azo

170.00  a

1.90  a

5.10  a

VCT + FE + Azo

196.35  a

1.70  a

5.29  a

PLL + Azo

234.20  a

1.74  a

5.91  a

 

Early Summer Study (Location 2)

 

Control

249.16  ab

2.39  a

5.84  a

VCT + FE

297.97  a

2.76  a

7.25  a

PLL

120.79  c

2.14  a

5.91  a

Control + Azo

162.20  bc

3.37  a

8.31  a

VCT + FE + Azo

199.59  abc

2.98  a

6.39  a

PLL + Azo

235.19  ab

2.51  a

7.02  a

 

Late Summer Study (Location 1)

 

Control

223.63  a

2.84  a

4.96  a

VCT + FE

228.88  a

3.04  a

5.57  a

PLL

238.86  a

3.36  a

5.75  a

Control + Azo

264.98  a

2.95  a

6.64  a

VCT + FE + Azo

280.69  a

2.56  a

6.01  a

PLL+ Azo

262.64  a

2.97  a

5.03  a

 

Late  Summer Study (Location 2)

 

Control

105.86  b

1.18  a

3.28  a

VCT + FE

135.11  ab

1.58  a

3.93  a

PLL

121.26  ab

1.45  a

3.81  a

Control + Azo

170.13  a

1.49  a

4.13  a

VCT + FE + Azo

147.68  ab

1.39  a

4.73  a

PLL + Azo

124.56  ab

1.24  a

3.99  a

 

Green Manure Study

Control

264.49  a

3.12  a

7.06  a

Green Manure Tea

293.36  a

3.21  a

7.71  a

         

Means (n=4) followed by the same letters are not significantly according to Tukey's HSD test at 5% probability

Discussion:  Plants naturally produce phytonutrients as a defense mechanism to protect themselves from pests and diseases and from ultraviolet light. When we consume plants rich in phytonutrients, they appear to provide humans with protection as well (Gupta and Prakash, 2014). Phytonutrients serve as antioxidants, enhance immune response, enhance cell-to-cell communication, alter estrogen metabolism, cause cancer cell to die, repair DNA damage caused by smoking, and detoxify carcinogens (Liu, 2007). However, studies have shown that free resources such as chemical fertilizers and pesticides cause plants to detract from producing defensive compounds (phytochemicals or phytonutrients) (Halweil, 2007). According to Brandt and Kidmose (2006), the levels of phytonutrients are higher in slow-released fertilizers, such as manure and compost, compared to chemical fertilizers. While this may be so for some sustainable fertilizers used in this study, not all of them produced higher phytonutrient contents than the control (chemical fertilizer). For example, in the early summer study at location 1, the chemical fertilizer treatment had a higher level of total phenolic contents and antioxidant capacity compared to the sustainable fertilizers. However, at location 2, VCT + FE significantly increased the amount of total phenolic contents in pak choi when compared to the PLL and Chemical + Azo treatments. At location 1 of the late summer study, there were no significant difference among the treatments for total phenolic contents; however, all of the sustainable fertilizers had a higher level than the control. The amount of total phenolic contents were different at location 2. The chemical fertilizer + Azospirillum treatment increased significantly compared to the chemical fertilizer treatment by itself. Across the studies the level of antioxidant capacity was higher in all of the sustainable fertilizer studies except at location 1 in the early summer study. Sustainable fertilizers had higher levels of total flavonoid content compared to chemical fertilizer at locations 1 and 2 of the late summer study.  Whereas, in location 1 and 2 of the early summer study, chemical fertilizers produced the 5th and 2nd highest level of total flavonoid contents, respectively.

Research conclusions:

Sustainable fertilizers have the ability to produced high-yielding nutritious pak choi and can be used as alternative fertilizer to chemical fertilizer and poultry litter for growing ethnic crops on the Delmarva Peninsula, which can reduce the amount of nitrogen runoff in our water bodies and improve soil health and soil fertility. While yield was not significantly different among the treatments, cobalt, iron, and total phenolic contents were significantly different at locations and crop varieties. Therefore, it can be concluded that plant yield, essential trace elements, and phytonutrients are affected by several factors, such as edaphic conditions, climatic conditions, crop variety, and type of sustainable fertilizers. Chemical fertilizers did not affect yield, essential trace elements and phytonutrients as it was hypothesized which could due to the fact that the amount of chemical fertilizer used in this study was small when compared to what is used in commercial farming system.

Participation Summary
11 Farmers participating in research

Education & Outreach Activities and Participation Summary

15 Consultations
11 On-farm demonstrations
2 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

400 Farmers
20 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

This is study was a part of a larger study whose goal was to provide the Delmarva small farmers with research-based knowledge on how to produce high-yielding nutritious ethnic crop on the Delmarva Peninsula. Thus far we have participated in four outreach events to share the research data. These outreach events include, (1) UMES AG Field Day, (2) UMES Annual Small Farms Conference, (3) Eastern Shore Vegetable Growers Meeting, and (4) Association of 1890 Research Directors (ARD) Conference.

Ethnic-Crop-Production-on-Delmarva_Corrie-Cotton

2017-ARD-Poster-Presentation_Burton_Cotton-1

Agfield Day

The UMES Small Farm Conference is an annual event that is popular on the Lower Eastern Shore and beyond. It provides practical information for agriculture related ventures among farmers, landowners, entrepreneurs, aspiring small business owners and supporters of agriculture. At the 13th annual Small Farm Conference held November 2016, our research team educated small farmers about the ethnic crop research, conducted a cooking demonstration with Amaranthus viridis, and serve samples of different recipes of Amaranthus viridis with the hibiscus drink. Farmers interested in participating in the UMES 2017 On-Farm Ethnic Crop Trials were asked at the end of the presentation to fill out a survey and provide their contact information. Today, we are working with 11 farmers who are participating in the on-farm crop trials and they are growing Amaranthus viridis and Hibiscus sabdariffa. We provided the farmers with the seeds and production guidelines on how grow, harvest, and market the crops.

Project Outcomes

40 Farmers reporting change in knowledge, attitudes, skills and/or awareness
6 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 Grant received that built upon this project
$274,998.00 Dollar amount of grant received that built upon this project
Project outcomes:

Sustainable fertilizers have the ability to produced high-yielding nutritious pak choi and can be used as alternative fertilizer to chemical fertilizer and poultry litter for growing ethnic crops on the Delmarva Peninsula, which can reduce the amount of nitrogen runoff in our water bodies and improve soil health and soil fertility. While yield was not significantly different among the treatments, cobalt, iron, and total phenolic contents were significantly different at locations and crop varieties. Therefore, it can be concluded that plant yield, essential trace elements, and phytonutrients are affected by several factors, such as edaphic conditions, climatic conditions, crop variety, and type of sustainable fertilizers. Chemical fertilizers did not affect yield, essential trace elements and phytonutrients as it was hypothesized which could due to the fact that the amount of chemical fertilizer used in this study was small when compared to what is used in commercial farming system.

Knowledge Gained:

We were of the mindset that sustainable agriculture production is the way to go. However, by conducting this research we have a greater understanding of sustainable production practices. The fact that there were no significant differences among the treatments for yield or nutrients greatly strengthened our beliefs. Therefore, we have become greater supporters to sustainable agriculture.

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.