Effects of sewage sludge application on selected soil properties and yield of maize and bambara groundnut

Abstract

Several studies in the temperate region have indicated that sewage wastes have the potential to improve soil properties but may also cause drastic reductions in soil productivity. We studied the effects of long-term application of dehydrated sewage wastes on soil properties and yield of maize (Zea mays L.) and bambara groundnut (Vigna subterranea) on a sandy Ultisol (Arenic Kandiustult) at Nsukka, Nigeria. The sewage sludge was applied at the rate of about 36 t/year for 40 years before this study was carried out. We sited two profile pits on the site that received the sewage (S/NSK/1 and S/NSK/2) and one pit on the site that did not (NS/NSK) and described them before collecting soil samples from the genetic hori­zons of each pit for analysis of soil properties. Soil organic carbon (OC), microbial respiration, electri­cal conductivity (EC), sodium adsorption ratio (SAR) exchangeable sodium percentage (ESP), total N, exchangeable Na and Ca, cation exchange capacity (CEC) and maize performance were significantly (P < 0.05) enhanced in the sewage treated soil compared to the non-sewage treated soil. The growth of salt-sensitive bambara groundnut was very poor on the former until the sludge was leached of excess salts with distilled water, after which its yield was identical with that from the control soil. Maize height and dry matter yield after 6 weeks were significantly improved (P = 0.05) on the sewage treated soil than the control. These results indicate that the application of sewage sludge on agricultural soils should be done with caution because of its negative effects on soils and crops when used at high rates.



Key words: Sewage sludge disposal; exchangeable bases; electrical conductivity; microbial respiration; salinity levels; sodium adsorption ratio.


Agro-Science Vol.2(2) 2001: 37-43