Developing Sustainable Tropical Leguminous Cover Crop and Green Manure Mulch Systems for Low-External-Input crop Production in the U.S. Virgin Islands, Puerto Rico, and Florida

Crop Production: conservation tillage
Education and Training: demonstration, extension, mentoring, workshop
Farm Business Management: whole farm planning, budgets/cost and returns
Pest Management: cultural control, economic threshold, mulches - killed, physical control, mulching - plastic, mulching - vegetative
Production Systems: agroecosystems, holistic management, organic agriculture
Soil Management: green manures, nutrient mineralization

Proposal abstract:

Tropical smallholder farmers operating under low-external-input (LEI) conditions rely upon non-intensive on-farm or locally available inputs for agricultural production; however, such resources are limited in the tropics and there is sparse data regarding the sustainability of tropical LEI agroecological systems. The primary objective of this study is to develop tropical leguminous cover crop and green manure (CC/GM) technologies for use as surface mulch in minimum-till agroecosystems to improve soil quality and provide alternative weed management strategies. Objective 1) will assess mucuna (Mucuna pruriens (L.) DC. cv. Vine 90 and Dwarf) varieties and cowpea (Vigna unguiculata L. Walp cv. Iron Clay) in the U.S. Virgin Islands (USVI) and Puerto Rico (PR) as CC/GM where the crop residue is terminated with a roller-crimper to produce organic sheet mulch. Cover crops will be evaluated on germination rate, establishment, plant vigor, biomass yield, plant tissue nutrient content, response to roller-crimper termination, and CC residue nutrient content and decomposition rate. Objective 2) will evaluate the effectiveness of mechanically (roller-crimper) killed tropical CC/GM as surface mulch for weed suppression and to improve soil quality for subsequent minimum-till vegetable crop production. Cover crop varieties to be tested will include sunn hemp (Crotalaria juncea cv. IAC-1), lablab (Lablab purpureus, var. rongai), and bush pigeon pea (Cajanus cajan cv. BRS Mandarim) in the USVI; and sunn hemp, mucuna, and cowpea in PR. Accessions will be planted in monoculture and evaluated as a CC for their beneficial contributions in rotation prior to a subsequent vegetable crop rotation. Cover crop species will be evaluated on the same production characteristics as in objective 1; and then as green manure surface sheet mulch in response to roller-crimper termination, weed suppression, surface mulch decomposition rate, and effect on soil quality in minimum-till hot pepper (Capsicum chinense Jacq.) production. Objective 3) will evaluate sunn hemp as a CC/GM either left as surface sheet mulch or soil incorporated for effects on soil quality and weed suppression in comparison to 3 traditional weed management practices. Traditional weed management treatments to be compared will include plastic mulch, cut and carry hay mulch, and no mulch (control). In year 1, objective 3 research will be conducted at the University of Florida (UF)-IFAS Suwannee Valley Extension Center and in year three at two on-farm locations in the USVI and PR with vegetable farmers to evaluate and compare sunn hemp as a CC/GM and the resulting residue as surface mulch for weed suppression compared to the 3 traditional weed management practices. Results from these studies will provide data on multi-purpose tropical legumes that incorporate CC/GM principles with crop residue management to suppress weeds and improve soil quality in LEI sustainable farming systems. Lastly, objective 4) will demonstrate and transfer results from the first 3 objectives to local farmers, agriculture extension and outreach personnel, and federal agricultural agencies throughout the USVI, PR, and Florida. The tropical cover crops included in this research can be utilized as multi-purpose warm-season summer covers in the Southern United States and can be adapted to fit varying agroecosystems.

Project objectives from proposal:

Objective 1: To assess two mucuna (Mucuna pruriens L. cv. Vine 90 and Dwarf) varieties and cowpea (Vigna unguiculata cv. Iron Clay) as a cover crop and then as a green manure (CC/GM) where the crop residue is terminated with a roller-crimper to produce organic sheet mulch. Research will be conducted in the U.S. Virgin Islands (USVI) and Puerto Rico (PR) in years 1 and 2. Cover crops will be evaluated on germination rate, establishment, biomass yield, plant tissue nutrient content, response to roller-crimper termination,weed suppression, and cover crop regrowth potential. Soil quality will be monitored and evaluated based upon the physical, chemical, and biological components of soil and their interactions. Weed populations will be identified, quantified, and monitored over time to determine biomass and population changes.

Objective 2: To evaluate and compare five tropical CC/GM species to each other and to a weedy fallow in rotation with a subsequent minimum-till hot pepper (Capsicum chinense Jacq.) rotation where the CC/GM residue is mechanically (roller-crimper) killed for surface sheet mulch for weed suppression and to improve soil quality. Cover crop varieties to be tested will include sunn hemp (Crotalaria juncea cv. IAC-1), lablab (Lablab purpureus, var. rongai), sunflower (Helianthus annuus), and pigeon pea (Cajanus cajan cv. BRS Mandarim) in the USVI; and sunn hemp, mucuna, and pigeon pea (Cajanus cajan cv. BRS Mandarim) in PR. Accessions will be planted in monoculture and evaluated as a CC/GM for their beneficial contributions in rotation prior to the vegetable crop rotation. Cover crop species will be evaluated on the same production characteristics as in objective 1; and then evaluated as surface sheet mulch following roller-crimper termination based upon weed suppression, surface mulch decomposition rate, and CC regrowth potential in minimum-till pepper production. Hot peppers will be transplanted directly into the CC/GM surface sheet mulch and hot pepper production yields, plant quality, and soil quality will be measured to determine effects upon crop production characteristics. These experiments will be carried out in years 1 and 2 in the USVI and in PR.

Objective 3: To evaluate sunn hemp as a CC/GM rotation with hot pepper production where the crop residue is either mechanically (roller-crimper) killed for surface sheet mulch or is green chopped and soil incorporated to determine effects on soil quality and weed suppression in comparison to 3 common cultural weed management practices. Traditional weed management treatments to be compared will include plastic mulch, cut and carry hay mulch, and no mulch (control). In year 1 and 2, research will be conducted at the University of Florida Agriculture Research Station in Live Oak, Florida and in year 3 research will take place in multiple on-farm trials to be conducted in the USVI and PR with farmers that currently produce hot peppers to evaluate and compare sunn hemp as a CC/GM and the residue as surface sheet mulch to standard weed management systems.

Objective 4: To demonstrate and transfer results from the first 3 objectives to local farmers, agriculture extension and outreach personnel, and federal agricultural agencies throughout the USVI, PR, and Florida. This will be accomplished through a series of cover crop management workshops that will be carried out in partneship with agricultural extension service personnel and the development of both printed and digital learning materials such as printed fact sheets and learning videos. The tropical cover crops included in this research can be utilized as multi-purpose warm-season summer covers in the Southern United States and can be adapted to fit varying agroecosystems.

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.