探讨分次施用脱硫副产物对碱土特性与向日葵生长的影响

1、探讨分次施用脱硫副产物对碱土特性与向日葵生长的影响    Effects of applying byproduct from flue gas desulfurization in batches on sodic soils quality and sunflower growth   Abstract In order to study the application mode of By-product from Flue Gas Desulfurization (BFGD) used to reclaim sodic soils, t

2、he field plot experiment of sunflower was conducted to analyze effects of twoapplication modes, applying BFGD in batches and applying BFGD only once, on the physical andchemical properties of two sodic soils (in sodic soil I, ESP=19.8; in sodic soil II, ESP=46.9) and thesunflower production. The res

3、ults indicated that ESP and pH of the top 40cm soil decreasedsignificantly, and germination rate, dry matter weight and sunflower production increased afterapplying BFGD in all the treatments. The soil EC in the top 40 cm soil appreciably increased in initialstage after applying BFGD. However, it wa

4、s lower after two years than that in initial stage and soil ECwas less than, or close to the value before the experiment. The mode of applying BFGD in batches wasbetter than that of applying it only once because the mode of applying BFGD in batches could decreasethe accumulation of soil salts and pr

5、omote the dissolution of CaSO4 .The ESP of sodic soil I and sodicsoil II reduced to 13.5 and 14.9 respectively, their pH reduced to 8 and 8.4 respectively, and sunflowerproduction increased by 1630.80 kg·hm-2 and 1315.65 kg·hm-2 respectively in the most effectivetreatments of applying BFGD

6、 in batches. In contrast to the mode of applying BFGD only once, the soilpH decreased by 4.76% and 2.33% in sodic soil I and sodic soil II, ESP decreased by 8.78% and24.75%, germination rate increased by 4.71% and 17.57% and sunflower production increased by12.95% and 17.52%.If the drainage was in g

7、ood condition and the byproduct was applied at right rate,the salts of soil top layer would not be accumulated. Keywords: By-product from Flue Gas Desulfurization (BFGD); application mode;sodic soils;reclamation; sunflower    1 Introduction Increasing concerns about SO2 emission

8、in flue gas of coal combustion and associatedproblems with acid precipitation have promoted the development of desulphurization technologiesto reduce SO2 emission but they also produce large amounts of byproduct from flue gasdesulphurization (BFGD; Carlson and Adriano, 1993). The main components and

9、 characters ofBFGD are similar to those of inartificial gypsum, and it contains abundant minerals such as S, Ca,and Si which are necessary to the plants (Xu etal, 2001). Substantial evidence exists that, withproper use, these by-products are valuable resources to improve soil, but improper use that

10、isdetrimental to the soil quality and the environment when they enter water system and pedospherewith rainfall and surface runoff (Carlson and Adriano, 1993; Stuczynski et al, 1998; Chun et al,2001). Typical sodic soils contain an excess of exchangeable sodium (ES) in soil colloids. Theyhave soluble

11、 carbonates in forms of Na2CO3 and NaHCO3, a value of pH>8.5, a value of electricalconductivity of saturated paste (ECsat) <4.0 dS·m-1, a value of sodium adsorption ratio (SAR)>13and a value of exchangeable sodium percentage (ESP) >15 (Ilyas etal, 1997). Reclamation andimprovement o

12、f sodic soils require the removal of part or most of the exchangeable sodium and itsreplacement by more favorable calcium ions in the root zone (US Salinity Laboratory Staff, 1954). In the world, the sodic soils reclaimed with gypsum (CaSO4·2H2O) has had a history of morethan 100 years, yet gyp

13、sum has not been popularized because of its expensive price. Theeffectiveness of the applied gypsum can be increased by improving permeability of the soil profile. The application of gypsum increases permeability and leaching (Frenkel et al, 1989; Baumhardt etal, 1992), improves flocculation and mac

14、roporosity (Bresler et al, 1982; Chartres et al, 1985),decreases bulk density (Southard et al, 1988) and reduce surface crusting (Gal et al, 1984).Interesthas been growing in the use of BFGD to reclaim sodic soils in recent years. Recent research hasshown that BFGD can significantly decrease soil pH

15、 and ESP, with no environmental impactsfrom trace metals, and increase germination rate and crops yield (Li etal, 1999; Chun et al, 2001;Wang and Yang, 2004; Sakai et al, 2004). When the by-product is used in agriculture, its high content of soluble salts may adverselyaffect plant growth because it

16、negatively impacts the osmotic potential of plant roots, even thoughit is a good source of CaSO4 (Katerji etal, 1997; Shannon, 1997; Clark etal, 2001). In sodic soils,swelling and dispersion of soil aggregates causes the decrease of the size and the number ofwater-conducting pores (macropores), resu

17、lting in a slow leaching. The salty water held inmicropores remains largely immobile under steady-state flow conditions, since the micropores donot take part in the water flow (Carter, 1989). If the soil profile has limited permeability, little ornone of the exchanged Na+ will be removed and gypsum

18、will largely be ineffective (Keren, 1996). So it is very valuable to determine suitable application mode and application amount of BFGD inwhich crops can bear not only the salinity but also the sodicity. Current research for sodic soilreclamation with BFGD is mainly focused on maintenance effect of

19、the byproduct on soil qualityand plant production under the condition that the BFGD was applied only once. Only a limited isconcerned about the benefits of applying BFGD in batches in the reclamation of sodic soils. In assessing the feasibility of reclaiming sodic soils, it is essential to first det

20、ermine the basicphysical and chemical properties of the soil (Van Rooyen and Weber, 1977).The objective of thisresearch is to determine the effects of different application modes of BFGD on sodic soilsproperties and sunflower growth and to select the best application modes of BFGD for sodic soilsrec

21、lamation which could control the salinity and the sodicity.    2 Materials and methods 2.1 Study area The study area was located at Changsheng Experiment Station of Inner MongolianBayannaoer water conservancy science research institute in Northwest China (40o20? N, 108o31?E). The

22、 field was flat and the soil type was silt clay. There were convenient condition of irrigationand drainage in this study area. The variation of water table was surveyed according to the nearestobservation well. According to the nearest weather station (0.6 km NW) the weather in the experimental area

23、during our investigation, was relatively dry, warm and sunny. The mean annual amounts ofprecipitation and evaporation were 215 mm and 2200 mm respectively. Irrigation and precipitationduring our investigations. 2.2 The physical and chemical properties of sodic soils and BFGD After our soil investiga

24、tion two sodic soils, sodic soil I (low ESP level, ESP=19.8) and sodicsoil II (high ESP level, ESP=46.9), were selected. Table 1 shows the main physical and chemicalproperties of the two sodic soils tested. The BFGD tested was from China Huaneng Power International, Inc, which had a pH of 6.8and its

25、 EC value was 3.15 dS m-1 (1:5, the by-product to water ratio). Content of CaSO4·2H2O inthe by-product was 89.8% based on dry sample and the amounts of total Ca in the by-product wasalmost 25%. 2.3 The requirement amount of BFGD The requirement amount of BFGD was calculated by a modified method

26、 (formula 2; Wang and Yang, 2005) referring to the requirement amount of gypsum (formula 1; Oster and Frenkel,1980) according to the content of calcium between BFGD and gypsum. R . H (CEC )( E E ) D Nai Naf = 0 086 ? (1)Where H is the soil depth to be reclaimed, 20cm; is the soil bulk density, g

27、3;cm-3; CECis the cation exchange capacity, cmol·kg-1; ENai is the initial exchange sodium fraction; Naf E is thedesired final exchange sodium fraction; RG is the amount of gypsum requirement, t·hm-2. BFGD D R = 1.11R (2)Where RBFGD is the requirement amount of BFGD, t·hm-2; 1.11 is t

28、he modified coefficient,which was concluded by comparing the content of CaSO4 between gypsum and BFGD. Based on the initial properties of sodic soils tested the BFGD application rates of sodic soil Iand sodic soil II were 6.29 t·hm-2 and 20.25 t·hm-2 respectively. 2.4 Experimental treatmen

29、ts To evaluate the effects of different application modes of BFGD on soil quality and sunflowerproduction, two application modes, applying BFGD in batches and applying BFGD only once,were studied in our study. Four treatments and one control were designed for each sodic soil. Theapplication rates of

30、 BFGD were showed in table 3. For the mode of applying BFGD in batches,the 80% of total amount of BFGD was applied in the first year, and 20% was applied in the secondyear. Field plot experiment was completely randomized designed for each sodic soil usingsunflower KANGDI 115. The soil body of 0 to 1

31、00 cm was spaced out by plastic in every plot. The by-product was applied to the experimental plot before seeding on September 9, 2002 andSeptember 21, 2003, and sunflower was planted in the next year. The by-product was uniformlyapplied and was incorporated into the top 20 cm of sodic soils by hoei

32、ng, and the control plot wasalso hoed. Each plot (4m×4m) was seeded with 300 seeds of sunflower on May 18, 2003 and May27, 2004 respectively. Sunflower was harvested on September 8, 2003 and September 12, 2004respectively. The germination rate, dry matter weight and sunflower production were me

33、asured toevaluate the plant growth of different application mode and application rate of BFGD. It wasassumed that the effects of the treatments on parameters will not be altered by the applied water,since all the plots received the same amount and quality of water. 2.5 Methods of measurement Three bulk soil samples were collected from each plot at the depths of 0-40 cm, air-driedafter removal of the plant roots, and passed through a 1-mm sieve. Analytical chemistry methodswere used to measure pH, EC, cation exchange capacity, exchangeable sodium, soluble cations (Na+, Ca2+, M