Redox Potential and Sugarcane Yield Relationship

Abstract

ABSTRACT OXIDATION reduction potentials were measured using platinum electrodes to estimate soil aeration on Mhoon silty clay loam soil planted to sugarcane. Using an Eh of 332 mV as the threshold value below which reduced soil conditions may cause crop damage, the number of days that Eh was < 332 mV was determin-ed for three soil flooding durations, two constant water tables, and one continuously drained treatment. These treatments were imposed on plots 40 m2 in size by flooding three times each summer in 1972 and 1973 on two plots each for 1-, 2-, and 4-wk duration followed by draining to 150-cm depth for 7-, 6-, and 4-wk, respec-tively. Constant water tables were maintained in two plots each at 30 and 120 cm below the soil surface while two plots were drained continuously. Correlating the total number of days Eh was < 332 mV each year with crop yields showed that cane yields decreased 0.2 t/ha and 0.3 t/ha in 1972 and 1973, respectively, for each day Eh was < 332 mV. Sugar yields decreased 28 kg/ha for each day Eh < mV in 1973. The maximum rate that Eh decreased during the various flooding treatments was 67 mV/day. This rate was used to estimate that 4 days were required for the soil to change from an oxidized (600 mV) state to a reduced (332 mV) state. This was also an estimate of how quickly this particular saturated soil must be drained to avoid a decline in sugarcane yields due to poor aeration