Soil enzymatic activity and growth of rice and barley as influenced by organic manure in an anthropogenic soil

Abstract

Pot experiments were conducted with rice and barley to investigate the influence of incorporated organic manure in an anthropogenic (paddy) soil on the enzymatic and biological activities and on the growth and mineral composition of plants. The soil used for the experiments was sampled in the coastal zone of eastern Jiangsu Province, China. The soil was an anthropogenic derived from alluvial and marine deposits. Four treatments, consisting of 20 g kg −1 rice straw alone (RS), 20 g kg −1 pig manure alone (PM), 20 g kg −1 rice straw plus 20 g kg −1 pig manure (RS+PM), and a control (no manure added) were investigated with rice as the first and barley as the second crop. The results showed that urease activity for RS+PM, PM and RS treatments increased by 163%, 96% and 21%, respectively, compared to the control at tillering stage of rice. Similar results were obtained at jointing stage. During the barley season, the urease activity of RS, PM and RS+PM treatments at tillering stage increased by 57.4%, 93.1% and 152.5%, respectively, compared to the control. The incorporation of organic manure into the soil significantly ( P<0.01) increased soil alkaline phosphatase activity and soil respiration rate regardless of crop species and growth stage. The addition of organic manure increased K ion but decreased Na ion uptake and transport to shoots from roots, thus enhancing K/Na selectivity ratio and salt tolerance of rice and barley plants. As a result, the dry weight of rice and barley for the treatments with organic manure significantly increased compared to the control. The incorporation of organic manure into salinised anthropogenic soil seems to be a practical and effective way to improve soil fertility, and enhance the salt tolerance and growth of crops. However, organic manure incorporated at excess dosage should be avoided, especially in a soil under long-term flooded condition, to reduce the risk of toxic effects of reduced metabolic intermediates.