The use of treated brewery effluent for salt tolerant crop irrigation

Brewery effluent (BE) can be used as a water and nutrient source for crop irrigation. It contains high levels of nitrogen and phosphorus, which are essential plant nutrients. However, the effluent at Ibhayi Brewery (SAB Ltd) has a high concentration of sodium, which is a constraint for its reuse in agriculture. The objectives here were to determine the salt removal efficiency, crop growth and health and changes in soil structure when four salt-tolerant test crops were irrigated with BE and subjected to crop rotation or soil amendments. These crops included Swiss chard (Beta vulgaris), saltbush (Atriplex nummularia), Salicornia meyeriana and sorghum (Sorghum bicolor), and all grew efficiently in BE irrigated soils but did not stop sodium accumulation in the growth medium. Nitrogen was successfully exploited, while phosphorus availability was limited by an unfavourable pH. Swiss chard had the best growth with a wet biomass production of 8173 g m⁻², due to the plant’s ability to tolerate saline conditions and continuous cropping. Crop rotation, aiming to limit the effects of nutrient depletion in soil, had no significant effect on plant growth, suggesting that the soils were provided enough micro-nutrients in the short term. Prolonged irrigation with BE can lead to sodium accumulation in the soil, which was successfully ameliorated through addition of soil amendments (gypsum and Trichoderma). These amendments reduced soil sodium from a potentially yield limiting level of 1398 mg L⁻¹ to the acceptable levels of 240 mg L⁻¹ and 353 mg L⁻¹, respectively, mainly through leaching. However, only the addition of Trichoderma improved Swiss chard production to 11,238 g m⁻², while reducing soil surface crusting and improving infiltration rates. Soil amended with Trichoderma appears to be a potential solution for BE reuse as a water and nutrient source in agriculture.