Effects of Thiourea on Metals Availability and Maize Physiological Characteristics in Acid Soils from South China

Abstract

It has been confirmed that thiourea (TU) was effective in inhibiting urea hydrolysis and nitrite formation. However, few studies focused on the toxicological effects and environmental impacts of TU. In this study, the influences of TU on the soil pH and available metals contents were reported. The addition of thiourea to the urea-treated soils led to a slower decrease or even increase in soil pH. The application of thiourea had slight influence on the content of available Cu in soils. Mn content increased with increasing TU concentration, however, the changes of Zn and Al contents were opposite. Pot culture experiments were conducted to investigate the effects of TU on the physiological characteristics of maize seedlings, including the plant growth, chlorophyll (CHL) content, metal ions uptakes and malondialdehyde (MAD) content in the leaves. 1 mmol kg-1 soil thiourea significantly inhibited the growth of maize seedlings. The application of thiourea enhanced the Mn accumulation in leaves, and negatively affected the Fe uptake, which thereby inhibited the biosynthesis of CHL. There was not any noticeable difference in MDA content in plants treated with 1-2.5 mmol kg-1 soil thiourea. An obvious increase of MDA content was found at 5 mmol kg-1 soil thiourea.