Control of secondary salinization in soils through effective microbes.

There have existed wide areas of soil secondary salinization in the western districts and coastal zones in China due to non-reasonable irrigation without good drainage systems. Secondary salinization of soils causes lower productivity of crops because of high salinity and poor structure .In order to ameliorate these saline-alkaline soils, EM technology combined with subsurface drainage is applied in the rice production in Ningxia and Zhejiang provinces. The results are summarized as follows (1) EM Bokashi with subsurface drainage treatment is the most effective in controlling the secondary salinization and raising rice grain yield and quality compared with other treatments; (2) EM technology can also increase soil organic substance content, improve soil porosity and permeability and raise soil available nutrients; (3)EM technology can evidently reduce amount of chemical fertilizers application, thereby improving the agriculture environment. Introduction Through the establishment of drainage-irrigation system combined with biological engineering measures,the salt-affected soils in China are gradually ameliorated and controlled. However, there are still secondary salinization soils of 36.9 million ha., of which cultivated ones mainly occur in the Huang-Huai-Hai plain as well as a small part of eastern coast with a total area of 6.24 million ha., taking up about 7% of the country’s cultivated land(Gong and Luo, 1997). These cultivated lands affected by salts are mostly formed due to irrigation with neglect of the drainage system notably in the (semi) arid region which are great obstacles to the development of agriculture. Use of beneficial and effective microorganisms as microbial inoculants in agriculture is a promising new technology(Shao et al., 2001). It has been shown to be effective in improving soil health and quality, and raising the growth, yield and quality of crops (Li et al., 1999). However the research is conducted considering the amelioration of salt-affected soils by use of EM technology. In this paper, EM technology combining with subsurface drainage is applied in the rice production in the Autonomous Region of Ningxia and Zhejiang provinces to see the effectiveness of EM in controlling the secondary salinization. Materials 1. Preparation of EM Bokashi and Methods EM Bokashi is an organic fertilizer prepared by adding water (500ml), molasses (8ml) and effective microorganisms (EM) (8ml) to a thoroughly mixed material of rice bran and animal manure (4.7Kg) then anaerobically fermented for 2 weeks. Equal amount of rice bran and animal manure without addition of EM was also fermented to produce traditional Farmyard Manure (FYM). The chemical properties of EM Bokashi used are presented in Table 1. 2. Description of the Field Experiment The field experiments were conducted from 2000 to 2001 in the saline soils of Qianjin Farm in the Autonomous Region of Ningxia and Baiquan town, Zhoushan city in Zhejiang Province respectively. Qianjin Farm is situated in arid area with the average annual rainfall of 186mm, whereas Baiquan town is located at the coastal humid zone with the average annual precipitation of around 1200mm. The experiment consisted of two blocks with and without the field sub-drainage system. The sub-drainage system used PVC tubes of 5.5cm diameter with the depth of 1.1m and the spacing of 15m respectively. Total eight plots (each of size 100mx30m) were given separately at two blocks of both sites. The following treatments were applied to designated plots each year in rice production: 1) Chemical fertilizer (N, P) without sub-drainage; 2) Farmyard manure (10t ha) + Chemical fertilizer (N, P) without sub-drainage; 3) EM Bokashi (10t ha) + Chemical fertilizer (N, P) without sub-drainage; 4) EM Bokashi (20t ha) without sub-drainage; 5) Chemical fertilizer (N, P) with sub-drainage; 6) Farmyard manure (10t ha) + Chemical fertilizer (N, P) with sub-drainage; 7) EM Bokashi (10t ha) + Chemical fertilizer (N, P) with sub-drainage; 8) EM Bokashi (20t ha) with sub-drainage. Chemical fertilizer was applied according to local recommendations as basal and dressing applications. Farmyard manure and EM Bokashi were applied as basal and mixed well in the soils up to 15cm depth. Each treatment was adjusted to contain almost equal amount of N and P nutrients at each site. The physio-chemical properties of soils tested are also listed in Table 1. Table 1. Some Properties of Tested Soils (0-20cm) and EM Bokashi