1. Tropical cover crop mulch systems for low-external-input reduced-tillage crop production Stuart A. Weiss D. D. Treadwell, E. Valencia, & K.P. Beamer USDA - Southern SARE Research & Education Program Project # LS12-252

2. Funding & Collaborators USDA Southern SARE Research & Education Grant Project # LS12-252 University of the Virgin Islands, Agricultural Experiment Station Duration: 2012-2014 Collaborating : Danielle Treadwell, Ph.D., Associate Professor, Horticultural Sciences Department, University of Florida, Gainesville, FL. Elide Valencia, Ph.D., Associate Professor, Agronomy Sciences Department, University of Puerto Rico, Mayaguez, PR.

3. Introduction Nutrients tied up in CC biomass are released back into the soil beginning at termination (Ditsch and Alley 1991). Minimum- till, mechanical-kill systems for cover crops have proven to be cost efficient, all while improving soil organic matter and providing weed suppression (Curran et al., 2010). Roller crimpers combine these methods into a low-input system that conserves energy and time, and can improve subsequent crop yield by increasing labile nitrogen (NRCS, 2002). More cover crop species need to be tested for their suitability for use with a roller-crimper (Curran and Ryan, 2010), particularly in tropical environments.

4. Cover Crop Management Using Roller-Crimper Technology Cover crops that are mechanically killed with a roller-crimper benefit the agricultural system by; – Reduction of soil temperature – Block solar radiation – Reduce soil moisture loss – Increase water availability to succeeding crops – Decreases soil nutrient loss through volatilization Cereal rye cover crop rolling/crimping in March 2011 at Brock Farm in Monticello, Florida. Custom roller/crimper design and fabrication by Kirk Brock Courtesy of Rodale Institute Rolling/crimping of sunn hemp cover crop on St. Croix, USVI. Design by Stuart Weiss

5. Cover Crop Residue Surface Sheet Mulch – Increases soil conservation through reduced tillage – Decomposition of CC sheet residue allows for the slow release and conversion of organic matter to plant available nutrients – Sheet residue more efficiently converts carbon into soil organic matter – Sheet residue acts as a barrier against weeds – Surface plant residues provides a beneficial microorganism rhizosphere (Southern SARE, 2012, Sullivan, 2011; Curran and Ryan, 2010, Hoorman et al., 2009; Wang and Klassen, 2005; Sullivan, 2003; NRCS, 2002)

6. Agricultural Relevance Inorganic commercial fertilizers, bulk soil amendments and chemical inputs are not economically feasible for smallholder farmers and are often not available at all (Smithson and Giller, 2002; Palm et al., 2001). Tropical conditions result in heavy, year-round weed pressure causing decreased farm productivity. Many warm season CC can be successfully grown in the U.S. Virgin Islands. However, successful CC termination with a roller/crimper and their residual use for weed control is unknown.

7. Objectives To evaluate three cover crops in tropical conditions produced with zero external inputs. To evaluate the effectiveness of a roller-crimper to terminate the cover crops to produce surface sheet mulch. – Evaluate termination method efficiency through cover crop residue re-growth. – Evaluate cover crop surface sheet mulch for weed suppression following cover crop roll down. To measure the combined system effects of CC residue surface sheet mulch on Jalapeno pepper production after CC termination.

8. Treatments and Methodology Treatments – sunn hemp (Crotalaria juncea cv. IAC-1) – pigeon pea (Cajanus cajan cv. BRS Mandarim) – sun flower (Helianthus annuus cv. Black Oil) – Weedy Fallow Control – Conventional full-till seed bed preparation Replications: 3 Fields were disk-harrowed in preparation for planting Cover crops planted by broadcast seeding and then rolled with a culti-packer on October 4, 2012 No external inputs were applied to the cover crops (no irrigation, fertilizer, or pesticides) All CC’s terminated on January 24, 2013 (112 DAP)

9. Statistical Analysis Data was subjected to General Linear Modeling (GLM) tests with a least significant difference range separation using SAS. – Version 9.3; SAS Institute, Cary N.C. – Significance reported at P<0.05

10. Cover Crop Establishment Germination 7 DAP and drip tape placement Pigeon Pea 47 DAP Sun Flower 47 DAP Weedy Fallow Control Sunn Hemp 47 DAP

11. Sampling Procedures Prior to Termination Biomass sampling of cover crops and volunteer weeds – 3 random 0.25m 2 samples collected per plot prior to CC kill – CCs and weeds were separated – Weeds were sorted by class (grass and broad leaf) – Samples were dried in a forced air oven to determine dry matter Cover Crops at Maturity Prior to Termination (112 DAP)

12. Cover Crop Performance. Weed Development, and Nitrogen Contribution from at Termination No difference was observed in CC plant tissue phosphorus or potassium levels

13. Custom Built Roller-Crimper Cover crops were terminated at 112 DAP with a custom built roller-crimper – Built from a recycled 24 inch disc plough using the disc and plough hubs, 24 inch steel pipe, steel tubing, and steel flat bar.

14. Cover Crop Termination with Roller-Crimper and Crop Residue Surface Sheet Mulch Pigeon Pea Sunn Hemp Sun Flower Control

15. Jalapeno peppers (Invicto-F1) grown in a green house and transplanted into treatment plots 42 DAP and 7 days after CC termination Control Sun Flower Pigeon Pea Sunn Hemp

16. Cover Crop and Weed Monitoring Procedures Post CC Termination Biomass sampling of cover crop re-growth and volunteer weeds 3, 6, 9, 12, and 15 weeks after termination. Six weeks after JP transplanting, all plots were split in half area- wise to compare JP yield from weeded (W) vs. non-weeded (NW) management. One half of each plot was hand weeded at 6, 9, and 12 weeks after JP transplant, and the other half of the plot remained unweeded allowing for maximum CC regrowth and natural weedy vegetation to emerge. CC regrowth and weed data was collected through the 15 th week after CC termination (May 23, 2013) – 3 random 0.25m 2 samples collected per plot per harvest – CCs and weeds were separated – Weeds were sorted by class (grass and broad leaf), no sedges were present – Samples were dried in a forced air oven to determine dry matter – Plant height was recorded for CC re-growth Agronomy program personnel Jose Hererra, Paul Beamer, and Nelson Benitez.

17. Cover Crop Re-Growth and Weed Development at 3 and 6 weeks after CC Termination 1.) At 3 weeks after CC termination, SH surface residue provided the greatest reduction in weed development. 2.) Sun flower was effectively killed with a roller- crimper showing no regrowth. 3.) At 6 weeks after CC termination, SH continued to reduce weed development with less GW than all other treatments and less BL weeds than PP or SH, but similar to the control. SH regrowth increased. Sunn Hemp Sun Flower Pigeon Pea Control Sunn Hemp Control Pigeon Pea Sun Flower

18. Cover Crop Re-Growth and Weed Development at 9, 12, and 15 weeks after CC Termination Low frequency weeding at 6, 9, and 12 weeks reduced SH and PP regrowth to minimal levels, however, SH and PP regrowth in non-weeded plots became major weeds. In weeded plots, CCs minimized weed development similar to conventional tillage through week 12. Sunn Hemp Control Pigeon Pea Sun Flower

19. Jalapeno Pepper Harvest First pepper harvest occurred on April 8, 2013 (112 DAP or 70 DAT). Peppers where harvested from data rows, graded (marketable or unmarketable), and weighed. There were a total of 9 pepper harvests with the final harvest on June 21, 2013.

20. Jalapeno Pepper Plant Development at 1 st Harvest (112 DAP) in Weeded Sub-Plots Sun Flower Control Pigeon Pea Sunn Hemp

21. Jalapeno Pepper Production Low frequency weeding of Sunn Hemp plots resulted in the greatest pepper yield, most fruit per plant, and the heaviest fruit. Non-weeded plots followed similar trends, but with severely reduced yields, fruit per plant, and individual fruit weight.

22. Summary of Results Sunn Hemp produced the greatest amount of vegetative biomass that contributed 92 kg/ha -1 nitrogen. Sunn hemp provided the greatest level of weed suppression (near 100%) of the three cover crops evaluated while sun flower had the poorest. The use of a roller-crimper for cover crop termination was effective for sun flower and sunn hemp, but was not effective for pigeon pea. Sunn hemp cover crop residue formed a layer of surface sheet mulch that suppressed weeds for 6 weeks after termination. Low frequency weeding of Sunn Hemp plots resulted in the greatest pepper yield, most fruit per plant, and the heaviest fruit.

23. Implications Cover crops can be a valuable management tool in the tropics that require few if any external inputs. Cover crop re-growth may cause weed problems when using a roller-crimper for termination of specific CC species in tropical or extended warm season environments. For indeterminate cover crops, roller-crimper termination may not be viable without additional management. Surface sheet mulch resulting from CCs terminated with a roller-crimper can be used for natural weed suppression and to protect soil quality for subsequent crop rotations.

24. Continuing Research Southern SARE Research and Education grant award “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” Identify and evaluate new tropical/warm season CCs that are compatible with roller-crimper technology. Compare different CC residue surface sheet mulch for weed suppression in vegetable crop rotations Compare CC surface sheet mulch to conventional weed suppression practices in vegetable crop production

25. Questions?