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Triploid watermelon cultivars are grown on more than 2,023 ha in Maryland and in Delaware. Triploid watermelon cultivars have little host resistance to Fusarium wilt of watermelon (Fusarium oxysporum f. sp. niveum). The effects of four different fall-planted cover crops (Vicia villosa, Trifolium incarnatum, Secale cereale, and Brassica juncea) that were tilled in the spring as green manures, and bare ground, were evaluated alone and in combination with the biocontrol product Actinovate (Streptomyces lydicus) on Fusarium wilt severity and watermelon fruit yield and quality. Six field experiments were conducted over 3 years in Beltsville and Salisbury, MD and Georgetown, DE. Both V. villosa and T. incarnatum significantly suppressed Fusarium wilt of watermelon as much as 21% compared with watermelon in nonamended plots. However, no suppression of Fusarium wilt occurred at low disease levels or where low cover crop biomass was present. In general, Beltsville, MD had lower disease levels than Salisbury, MD and Georgetown, DE. T. incarnatum was the only cover crop that yielded significantly more fruit than nonamended treatments (129% more fruit per hectare) but only for one field trial. The Actinovate product either did not reduce Fusarium wilt or the magnitude of the reduction was nominal. Actinovate significantly reduced Fusarium wilt by 2% in 2009 and as much as 7% in 2010, and increased Fusarium wilt severity by 2.5% in 2011. Actinovate significantly increased yield for one field trial but only when applied to nonamended or Secale cereal-amended plots. This is the first report of a reduction in Fusarium wilt following a T. incarnatum cover crop incorporated as a green manure.

This chapter examines the potential biophysical and socio-economic benefits and constraints for scaling up conservation agriculture (CA). It also discusses the relationships of CA with the popular topics of sustainable intensification (SI) and resilience. Case studies focused on CA for small landholders in southern Africa and peninsular Southeast Asia are presented. While CA systems across the world share common principles, there are also important differences among geographic locations because of climatic and soil conditions, farming system types, crop-livestock interactions, access to resources by farmers, and other factors. The case studies illustrate the effects of such differential conditions on the development of CA systems.