Effect of limestone dose on the incidence of Rhizoctonia root rot and soybean yield in four soil types

Abstract

AbstractRhizoctonia root rot (RRR) is a disease caused by the soilborne pathogen Rhizoctonia solani, which kills soybean plants in patches over croplands. Control is difficult because the pathogen survives in the soil and has a wide host range; therefore, cultural control methods might help to diminish disease pressure. The objective of this study was to evaluate liming as a strategy to reduce the incidence of RRR in soybean grown in four soil types: acrisol (Ac), cambisol Ta (CaTa), cambisol Tb (CaTb) and nitisol (Nit). The treatments were arranged in a factorial design of four doses of limestone (0, 3, 6 and 9 t/ha) at two sites within each field (inside and outside a Rhizoctonia patch). The incidence of RRR inside the patch was on average 40.3% whereas outside it was 1.2%. The reduction in disease incidence was 3.9%, 3.7%, 3.6% and 1.8% per 1000 kg of limestone applied for the Ac, CaTa, CaTb and Nit soils, respectively. The highest soybean yield was of 4713 and 3349 kg/ha for the Ac and Nit soils with application of 6.6 and 6.2 t/ha of limestone, respectively. Soybean yield in the cambisols increased linearly with liming, with an increase in yield of 121 and 172 kg/ha in CaTa and CaTb, respectively, for each 1000 kg of limestone applied. Thus, liming reduced the incidence of RRR in all soils and promoted better soybean nutrition, increasing soybean yield. Therefore, liming is a practice that contributes to both soil fertility and disease control.