The effect of irrigation with anaerobic baffled reactor effluent on nutrient availability, soil properties and maize growth

A glasshouse study was carried out to assess the availability to maize of nutrients from anaerobic baffled reactor (ABR) effluent. Maize was grown for 6 weeks in pots with three contrasting soils namely a sandy soil (Cartref (Cf), Typic Haplaquept), an organic, acidic soil (Inanda (Ia), Rhodic Hapludox) and a clayey soil (Sepane (Se), Aquic Haplustalf). Fertilizer (N, P and K) was applied at the recommended rate, half the recommended rate and zero fertilizer for each of the soils used. Lime was applied to the Ia following recommendations. Plants were irrigated with either effluent or tap water. Dry matter yields and nutrient concentrations for effluent-irrigated maize were significantly higher (p < 0.05) than for all water-irrigated plants. For each soil, the unfertilized, effluent-irrigated plants were not significantly different in most of the above-ground nutrient concentrations from the water-irrigated plants at half fertilization. Phosphorus deficiency was observed in the Ia and Se but not in the Cf, irrespective of fertilizer treatment. Plants grown on the Cf irrigated with effluent and fully fertilized had the highest above-ground dry matter yield (4.90 g pot−1) and accumulated more N, P, K, Ca and Mg than all other treatments. After harvest, P in the Cf soil was significantly higher (p < 0.05) in the effluent-irrigated than the water-irrigated soils reflecting P input from the effluent. Concurrently, the effect of the effluent was further investigated by planting maize on the Ia with neither lime application nor fertilization. Plants that received effluent irrigation and no lime had significantly higher (p < 0.05) dry matter yields (2.67 g pot−1) and accumulated more N, P and K than those water-irrigated with no lime as well as the equivalent limed treatments. This suggests an interaction effect between the lime and effluent properties.