| Coastal saline soil is an important land resource in developing agriculture and husbandry production. For the dual influences of ocean tide and ground water, the soils in coastal saline areas have the characteristics high salt content and low nutrient content. The moderate salinized coastal saline soil in agricultural science and technical experimental field in Jiangsu province was selected as a study area. The physicochemical properties of coastal saline soil, restraining salt fertilizers field test and soil amendment and conditioners field test were studied.23profile sites were selected to determine the salt content, soil pH, and the content of the main ions in every soil layers. Meanwhile,3typical soil profiles (salinized soil profile, slight saline soil and moderate saline soil) were selected to study the influence factors of soil saturated hydraulic conductivity. In restraining salt fertilizers field test, the soil fertilizer content, ions content and crop growth status were analylized after the single application of4restraining salt fertilizers (organic-inorganic compound fertilizer (10-5-5); organic-inorganic compound fertilizer(12-8); bio-organic fertilizer; inorganic compound fertilizer(15-15-15)) and the fertilizers combined with gypsum(3levels) application. In soil amendment and conditioners field test, soil physicochemical properties, ions content and crop growth status were analylized after the single application of4soil amendment and conditioners(Hekang, Kangdibao, Jinmantian, Humic acid) and the soil amendment and conditioners combined with gypsum(2levels) application. The most suitable restraining salt fertilizer and soil amendment and conditioner and their combinations were selected. The main results were as follows:(1) The maximum salt content was in the0-5cm soil layer. The salt content under40cm of soil profile was nearly the same. In all layers of the soil profile, the content of Na+was from69.62%to83.12%in the total amount of cations, the content of Cl" from62.77%to72.25%. Na+and Cl" were the most important cations and anions in the soil salt composition in study area. The content of Na+and Cl" was the highest in the0-5cm soil layer in soil profile, and lower as the layer was deeper.(2) The soil saturated hydraulic conductivity of slight saline soil was highest, next was moderate saline soil, and the third was salinized soil. The impact factors of soil saturated hydraulic conductivity were soil bulk density, soil texture and soil salt content. The soil saturated hydraulic conductivity of salinized soil showed a significant negative correlation with soil bulk density, and the functional relationship was:y=429.39x2-1155.8x+778.59, r=-0.9693*(n=5); The soil saturated hydraulic conductivity of slight and moderate saline soil had a negative linear correlation with soil bulk density. The functional relationship were:y=-46.348x+71.073, r=-0.9025*(n=5) and y=-19.932x+31.692, r=-0.8539*(n=5). The soil saturated hydraulic conductivity of slight and moderate saline soil decreased at soil surface layer and then increased. It was related to the migration of clay and silt in soil profile.(3) Weight values of5nutrient indexes (soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium) were determined by using correlation and the principle component analysis method. Then the soil integrated fertility indexes were respectively obtained, which reached a very significant level (r0.01=0.9898, n=13). The functional relationship is y=1.0154x-0.0907. So the IFI was used to evaluate the fertilizing effect of different restraining salt fertilizers application is feasible. Compared with the IFI, organic-inorganic compound fertilizer (12-8) was the best in improving the soil nutrient in coastal saline soil. Next was organic-inorganic compound fertilizer (10-5-5), and the third was bio-organic fertilizer. The inorganic compound fertilizer (15-15-15) was the last; the application of gypsum could improve the soil fertility, but can cause the content of available phosphorus decreased because of fixing. When gypsum was utilized to improve the coastal saline soil, its amount should be paid attention to. The improve effect was better when the amount of gypsum was300kg/hm2combined with organic-inorganic compound fertilizer (12-8).(4) The ions content had changed after the different treatments of restraining salt fertilizers application. Compared with CK, the application of organic-inorganic compound fertilizers were better in decreasing the content of Na+and inhibiting the content of Cl-increasing. Second was bio-organic fertilizer, and the third was inorganic compound fertilizer. The content of Na+and Cl-decreased0.85cmol/kg and0.28cmol/kg respectively after the treatment of organic-inorganic compound fertilizer (12-8) application. The contents of K+and NO3-were influenced by the contents of potassium and nitrogen in the restraining salt fertilizers. The application of phosphorus-containing fertilizers meight decrease the content of Ca2+, while the application of organic-inorganic compound fertilizers and bio-organic fertilizer could increase the content of Mg2+. The content of SO42-had some increasing after treatment than before, and the total alkalinity was lowest after the treatment of organic-inorganic compound fertilizers application, next was bio-organic fertilizer and inorganic compound fertilizer application.(5) The application of four restraining salt fertilizers all could decrease the total salt content, S AR and soil pH, and improve the biomass, plant height and yields of the rape and maize. The effect of organic-inorganic compound fertilizer (12-8) application was best. The yields of rape and maize in2010increased25.04%and22.53%compared with CK, next was organic-inorganic compound fertilizer (10-5-5), and the third was bio-organic fertilizer. The inorganic compound fertilizer (15-15-15) was the last. When the restraining salt fertilizers combined with gypsum applicated, as the application rate of gypsum increased, the biomass, plant height and yields of the rape and maize increased first, and then decreased. The biomass, plant height and yields of the rape and maize were more when the application rate of gypsum was300kg/hm2than600kg/hm2. The improve effect was better in test area when the amount of gypsum was300kg/hm2combined with organic-inorganic compound fertilizer (12-8), and the yields of rape and maize reached to3362kg/hm2and6866kg/hm2respectively in2010, meanwhile increased30.11%and27.12%compared with CK. The yields of rape and maize reached to1780kg/hm2and3883kg/hm2respectively in2011, meanwhile increased212.28%and84.89%compared with CK.(6) Soil amendment and conditioners could decrease the salt content, soil pH and soil bulk density in plough layer. The effect of Humic acid was best in decreasing the salt content, soil pH and soil bulk density. After the treatment of Humic acid (300kg/hm2), the salt content in the0-40cm soil layer decreased by28.77%compared with CK, and the soil pH decreased0.16unit. Second was Hekang, and the third was Kangdibao. The Jinmantian biological agent was the last. Soil amendment and conditioners also could improve the soil total porosity and soil saturated hydraulic conductivity. The effect of Humic acid was best, Kangdibao was,second and the third was Hekang. The Jinmantian biological agent was the last.(7) Every ion content had changed after the treatment of different soil amendments and conditioners application. Compared with CK, the application of Humic acid was best in decreasing the contents of Na+, Cl-and total alkalinity in the soil, which decreased0.50 cmol/kg,0.85cmol/kg and0.170cmol/kg respectively, and then were Kangdibao, Hekang and gypsum. Compared with CK, the effect of Jinmantian biological agent treatment was not significant in decreasing the content of Na+, Cl-and total alkalinity. The content of K+, Mg2+, Ca2+and SO42-increased in different degrees. The content of NO3-was mainly influenced by precipitation. There were no obvious difference among different soil amendment and conditioners.(8) Soil amendment and conditioners could improve the plant height of maize. Compared with CK, the biomass and yield of rape and maize were also improved by soil amendment and conditioners. The effect of Humic acid application was best, the yields of rape and maize reached to3427kg/hm2and7922kg/hm2respectively in2010, and increased15.68%and9.15%compared with CK. The yields of rape and maize increased to41.62%and104.85%in2011. Second was Hekang, and the third was Kangdibao. The combined application of Humic acid and gypsum was the best combination to the coastal saline soil. After the treatment of Humic acid combined with gypsum, the salt content decreased0.39g/kg, soil pH decreased0.19unit in0-40cm soil layer, soil bulk density decreased0.10g/cm3in plough layer, and the soil total porosity and soil saturated hydraulic conductivity was the maximum. The yields of rape and maize reached to3513kg/hm2and8084kg/hm2respectively, and increased18.60%and11.38%compared with CK in2010. The yields of rape and maize increased to45.95%and110.83%in2011. So the effect of Humic acid application combined with gypsum was the best, and it was the most suitable combination to the coastal saline soil in study area. |
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