Sustainable diversification of paddy lands under minor irrigation systems in the dry zone of Sri Lanka. A case study from Vavuniya District

agriculteur agricultores arid zones arroz arrozales barrage condiciones sociales condition sociale conduite de la culture crop management crop yield cultivation cultivo dams diversification embalses farm income farmers irrigation systems legumes leguminosas manejo del cultivo motivation pratique culturale rendement des cultures rendimiento de cultivos represas revenu de l'exploitation rice rice fields riego complementario riz sistemas de riego social conditions sostenibilidad sri lanka supplemental irrigation sustainability water reservoirs zone aride