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

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

Summary

A total of three field studies were conducted during 2016 to examine yield of Brassica rapa cv. Bosai Chinensis (Bok choy) using sustainable production practices. Two studies, using two bok choy varieties (Mei Qing Choi hybrid and Joi Choi hybrid), were conducted in the summer at two separate locations on the University of Maryland Eastern Shore (UMES) research farm. A third study was conducted in the fall. Mei Qing Choi hybrid was planted early summer and Joi Choi hybrid was planted late summer. Both studies used 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, and four replications each. Joi Choi hybrid was planted in the fall using a complete randomized design with two treatments, (1) Control (20:20:20) and (2) cowpea green manure tea. Bok choy was harvested at the mature stage from all studies and fresh weight was recorded and analyzed. For each treatment, a random sample was collected during each harvest and stored in the freezer for future mineral and phytonutrients analysis.

Objectives/Performance Targets

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.

Accomplishments/Milestones

The first and second phase of this study has been completed. The first phase was to identify and select elite biofertilizer(s) to use in the field studies. A greenhouse study was conducted at the UMES Agriculture Experiment Station between the 26^th of January to the 29^th of March 2016, to examine the application of beneficial organisms on the growth and development of bok choy. The experiment was a complete randomized design with 8 treatments and 2 soil types (pro-mix and field soil) with four replicates each. Treatments included (1) Control (no inoculum), (2) Trichoderma, (3) Azospirillum, (4) Endo/Ectomycorrhizae, (5) Trichoderma + Azospirillum, (6) Trichoderma + Endo/Ectomycorrhizae, (7) Azospirillum + Endo/Ectomycorrhizae, and (8) Trichoderma + Azospirillum + Endo/Ectomycorrhizae. Promix was placed in 4 ½ inch pots and inoculated with treatments as describe by manufacturer. Two bok choy seeds were planted in the inoculated Promix. One week after germination, one seedling was removed to prevent nutrient competition. At three weeks after germination, plants were transplanted into larger pots in two different inoculated soil types (field soil and promix). Plants were watered and fertilized when necessary. Yield data was collected at the maturity stage (7-8 weeks after planting). Results showed that there were no significant difference among the treatments. However, Azospirillum had a higher yield than the other treatments. Therefore, Azospirillum was selected to be use in the 2016 field trials.

The second phase of this study was to investigate the impact of green manure and biofertilizer on the growth and development on bok choy. Field studies 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 bok choy. The Mei Qing Choi (variety # 1) was planted in the early summer (June 10^th to July 14^th) and the Joi Choi (variety # 2) was planted in the late summer (August 4^th to September 8^th). 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. Joi Choi hybrid was planted in the fall (October 26^th to December 14^th) using a complete randomized design with two treatments, (1) Control (20:20:20) and (2) cowpea green manure tea. For each treatment, 18 seedlings were planted (6 seedlings per row) at approximately 6 inches apart. For the summer study, 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. In the fall study, 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. Bok choy was harvested at the mature stage; six plants from each data row, of each replication, were cut at the base and placed into labeled bags. The fresh weight of each treatment was recorded for statistical analysis. Results showed that yield data varied among treatments and locations, but there was no significant difference among treatments (Table 1, 2, 3, and 4).`

Table 1. Early summer bok choy yield data for locations 1 and 2

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

Table 2 Late  summer bok choy yield data for locations 1 and 2

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

Table 3. Fall bok choy yield data

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

Table 4. Complete randomized Design Analysis of Variance (CRD-ANOVA) for bok choy yield for early summer, late summer and fall field study.

 *  DF= Degree of freedom, SS = Sum of squared, MS = Mean of squared, F= F-value, and P= Probability

Impacts and Contributions/Outcomes

Based on the field studies conducted, results showed yield variations among treatments and locations. However, there was no significant difference among the treatments when compared to the control. Location #1 produced the lowest yield when compared to location #2 in both early and late summer bok choy studies. The reason for this is not yet known; however, we awaits the results from soil analysis to determine the cause. The fertilizers used in these studies have shown to produced high yielding bok choy and could be used in sustainable farming system to reduce the use of chemical fertilizer and poultry manure on the Delmarva. While these biofertilizers have shown to improve yield, evaluating their impact on bok choy nutrient contents and phytonutrients is important in order to select an elite sustainable fertilizer for vegetable production within the region. The phytonutrients and mineral contents will be analyzed in the near future.

Collaborators: