Organic manure stimulates biological activity and barley growth in soil subject to secondary salinization

A pot experiment was performed to compare the impact of organic manure on soil enzymatic activity, respiration rate and the growth of two barley cultivars (Hordeum vulgare L.) differing in their salt tolerance under a simulated salinized environment. A plastic pot with a hole (2 cm in diameter) in the center of bottom was filled with an anthropogenic (paddy) soil and placed in a porcelain container containing NaCl solution (3.0 g L-1) such that a secondary salinization process was simulated via upward capillary water movement along the soil profile. A treatment with neither organic manure nor simulated soil salinization was taken as a control (CK1). The organic manure was applied either inside or outside rhizobag made of nylon cloth (40 mu m of pore size). The soil was treated with: 20 g kg(-1) rice straw (RS), 20 g kg(-1) pig manure (PM), or 10 g kg(-1) rice straw plus 10 g kg(-1) pig manure (RS + PM). No organic manure was added in an additional control treatment (CK2). The results indicated that the placement of organic manure both inside and outside rihzobags significantly increased the activity of urease, alkaline phosphatase and dehydrogenase, as well as respiration rate in both rhizosphere and bulk soils. Also, nutrient uptake by barley plants was enhanced in the treatments with organic manure amended either inside or outside rhizobags. The activity of these enzymes along with the respiration rate was higher in rhizosphere than in non-rhizosphere when organic manure was supplied inside rhizobags, while the opposite was found in the case of manure incorporated outside rhizobags. Among all the treatments, RS + PM treatment had most significant stimulating effects on enzymatic and microbial activity and shoot dry weight of barley, followed by PM and RS. Moreover, more significant stimulating effects on both enzyme activity and plant growth were achieved in the treatments with manure amended inside rhizobags than outside rhizobags. The results of the present study confirmed the view that incorporation of organic manure especially into soil-root zones is an effective low-input agro-technological approach to enhancing soil fertility and minimizing phytotoxicity induced by secondary salinization. (c) 2005 Elsevier Ltd. All rights reserved.