Potential cover crop options for nematode and weed suppression in Haiti.
Cover crops can provide a replacement for chemical management of weeds and plant-parasitic nematode (PPN) pests while protecting the soil from erosion and contributing fertility through organic matter. These ecosystem services are especially important for smallholder farmers in Haiti and in developing nations throughout the tropics, for whom imported fertilizers and pesticides are often inaccessible. In the dry season from January to March, a study was conducted to evaluate the potential of tropical cover crops in one upland and one lowland site in Haiti. The objective was to determine the weed and nematode suppression potential of cover crop treatments, including the legumes sunn hemp [(SH) Crotalaria juncea L.], cowpea [(CP) Vigna unguiculata (L.) Walp], and lablab [(LB) Lablab purpureus (L.) Sweet cv. Rongai] in monoculture, two-way mixes of each legume with sorghum sudangrass [(SS) Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf cv. Surpass BMR], a four-way mix of all species, and a natural fallow(NF) control. At 8.5 weeks after planting (WAP) the cover crop treatments did not differ in their shoot biomass production. Cover crop treatments also did not result in a significant decrease in weed biomass compared to the natural fallow by 8.5 WAP. Shoot biomass of Parthenium hysterophorus, a dominant weed at upland site, was higher with the CP cover crop than with the NF. Root-knot nematode (RKN; Meloidogyne sp.) was found only at the lowland site. The reproduction factor of RKN with LB was significantly higher than with LB/SS mix, SH, and the SH/SS mix. Eight other genera of PPN were recorded for the first time to our knowledge in Haiti (Rotylenchulus, Pratylenchus, Tylenchorhynchus, Hoplolaimus, Criconomella, Helicotylenchus, Heterodera, and Xiphinema) but were not significantly affected by cover crops. While the cover crop treatments were not effective during this season for weed suppression, evaluation of better adapted cultivars and/or at a different time of year may provide both weed and RKN suppression.