Cover Crops for Improving Recalcitrant Soil Organic Matter and Soil Biota Management in Plantain Production Systems in Puerto Rico

Cover Crops for Improving Recalcitrant Soil Organic Matter and Soil Biota Management in Plantain Production Systems in Puerto Rico

Summary

Initial soil analyses for RSOM, SMB and Dehydronase activity have been conducted. Cover crop establishment was severely affected by rodents. Despite several efforts to establish the cover crops, other natural causes (torrential rains, drought) did not allowed proper establishment. Experimental plots will be re-established, a year extension for the period of performance was requested and granted.

Active collaboration of the Business Sector, and the Public and Private Academic University Sector has been achieved, thus demonstrating a fruitful pathway to conduct R&D in sustainable agriculture in Puerto Rico. A total of nine non-agriculture majoring university students have been involved in this project.

Objectives/Performance Targets

This project objective is to determine as a function of Cover Crops use on plantain crop systems: 1) Recalcitrant Soil Organic Matter (RSOM) formation rates; 2) soil microbial biomass (SMB); 3) Dehydronase activity.

Accomplishments/Milestones

The experimental plots are located at our rented land at the University of Puerto Rico Agricultural Experiment Station (UPR-AES) at Gurabo, PR. The RSOM analyses are conducted at the Chemistry and Agroenvironmental Sciences Laboratory (UPR-AES) at Río Piedras, PR. The SMB and Dehydronase analyses are conducted at the Universidad del Turabo School of Natural Sciences and Technology Laboratories.

Cover crops establishment:

Six CC treatments are being evaluated [{1}Jack Bean (JB) (Canavalia ensiformis), {2}Sunnhemp (Crotalaria juncea),{3}sorghum (Sorghum bicolor), {4}JB+Sunnhemp, {5}JB+sorghum, {6}JB+Sunnhemp+sorghum]. The experiment has a complete randomized design with experimental (six CC treatments) and control (bare soil) plots (800 feet2/plot) (total of 7 plots), with 4 repetitions.

The cover crops seeds were planted by hand. This past year we had consequent problems for establishing the cover crops, principally due to rodents damage to the sorghum treatments.  We repeatedly tried to re-plant the sorghum treatments in different ways:

1. Hand direct seeding – 5 times (by the 3rd time we discovered it were rodents)
2. Propagation-trays transplants = we decided to use the trays to try to avoid field rodent damage.  However, 2 days after transplanting on experimental parcels, torrential rains washed the transplants, which we tried to re-plant but they were too damaged.

Also, last year we experienced a prolonged severe drought period, which limited the development of the plantain and cover crops germination rates.  Supplemental irrigation was not available until August 2014, when the farm irrigation system was finished with USDA-NRCS assistance.

Therefore, after all these difficulties and attempts for establishing the cover crops the Project Staff decided to extend the period of performance for one year, so that we can “Reset” everything. This extension was approved by Dr. John Wayne.

RSOM analyses

RSOM analyses were conducted to determine initial RSOM levels on the experimental plots using a modified procedure from Cheng et al. (2007). These initial levels will be the base to compare the effect of cover crops treatments on RSOM over time.

SMB and Dehydronase:

Initial works were conducted.  However due to problems with establishment of cover crops, these analyses of Soil Biota have been postponed to this year’s work.

Root Parasitic Nematode Biocontrol Fungi

At the UPR-Humacao Environmental Microbiology Laboratory Dr. Francisco Fuentes with 7 undergraduate students have been isolanting native nematophagous fungi from the experimental plots. Dried soil samples were spread over Water-Agar, Saubouraud and Corn Meal Agar plates. Saubouraud agar plates showed better results for the cultivation of soil fungi. Ascomycetes fungi showing macroconidia, asexual reproductive spores, predominate among the isolates. Some isolates present rings similar to contractile rings produced by some nematophagous fungi.

At present, they are working in the reproduction of nematodes in the lab. It is needed large quantities of nematodes to induce the generation of fungi trapping structures. Some success has been attained using one of the fungal isolates.

• HolesMarksSeedExcavated by Rodents
• Drought – Soil Dryness
• Excavated Holes by Rodents eating planted seeds
• Isolated Fungi with apparent crontractile rings
• CoverCropsHandSeeding
• SoilSampling
• Drought – Soil Dryness
• Isolated Fungi with apparent crontractile rings

Impacts and Contributions/Outcomes

The project has achieved the active participation of graduate and undergraduate microbiology students from two universities that are not specialized in agriculture (Universidad del Turabo and University of PR at Humacao). These 9 microbiology students have been very motivated to apply their area of study to Puerto Rico’s agriculture in a tangible way, and now they position themselves contributing to PR’s agricultural development. This is very important as sustainable agriculture R&D in Puerto Rico would benefit significantly by multidisciplinary and Inter-Institutional contributions. This project serves as a model for achieving this effort.

The long-term benefit from this project will be to:

1. Validate with locally produced empiric data the effect of cover crops on sustainable management of soil health for Puerto Rico. This information is crucial in order to validate from a scientifically standpoint the use of cover crops as a tool in mainstream agricultural production. We conducted interviews to over twenty UPR AgExtension Agronomists all around Puerto Rico during this year, and it was revealed that Cover crops are not being recommended because their use have not been evaluated and validated in order to add them to the Crops Production Official Guides as a recommended agricultural practice, despite the international generalized consensus.
2. Serve as a professional development scenario for students enrolled on diverse Natural Sciences careers to empower sustainable agriculture in Puerto Rico.
3. Serve as a model for multidisciplinary and Inter-Institutional collaborative work towards sustainable agriculture. This project has achieved an active collaboration between the private sector (Agro Tropical, Inc.), Public and Private Academia sector (University of Puerto Rico and Universidad del Turabo, respectively), and also in the particular case of the University of Puerto Rico, the participation of different University divisions (UPR-Humacao Campus and UPR-Agricultural Experiment Station).

Collaborators: