Sunn hemp intercrop and mulch increases papaya growth and reduces wind speed and virus damage

Abstract

Papaya (Carica papaya L.) production in south Florida is limited by trade winds, storm wind damage, and papaya ringspot virus (PRSV) infection. This study was implemented to test a system intercropping sunn hemp (Crotalaria juncea L.) with papaya during papaya establishment, then mowing the intercrop and using it as a mulch on papaya beds. The study was performed in 2014 and repeated in 2015. Treatments included no sunn hemp (No-SH), sunn hemp mown early (SH-ME) 65days after transplanting (DAT), and sunn hemp mown late (SH-ML) at 100 DAT. Wind speeds, sunn hemp growth and biomass contribution, papaya above ground growth, yield, flowering date, weeding time, and gas exchange variables, including net CO2 assimilation (A) and stomatal conductance (gs) of H2O were measured. In 2015, additional measurements included PRSV infection rates and root growth via minirhizotron imaging. Results indicated a positive establishment environment as a result of the sunn hemp intercrop-mulching system. The system reduced weed pressure, reduced wind speed within papaya rows, and increased papaya growth after mowing and mulching. In 2015, standing sunn hemp reduced PRSV infection rates and hastened flowering. Mulching increased root growth in 2015, and A and gs for 2 months after mulching. The SH-ML treatment led to elongation and reduced growth due to excessive shading. With the appropriate timing of mowing, this system promises improved production efficiency and reduced risks for south Florida papaya producers.