Study On The Change Regulation And Effect Of Improvement Measures Under Protected Cultivation

A series of production problems such as soil acidification, secondary salinization, nutrient imbalance have appeared gradually with the extension of planting years in protected field in suburbs of Harbin. Soil quality Attributes(soil aggregates size, porosity, nutrients, salt, ect) of protected field in different planting years at Xiangfang district Harbin are analyzed by taking a combination of laboratory testing and field experiment. By which, we make clear the protected soil quality and its change regulation and existing problems.A field soil improvement test with different fertilization and soil amendments (for example Potassium humate and Zeolite)was set in typical protected field of20years to resolve the problems. The effect of different fertilization and improvement measures on soil physical properties, chemical properties, biological properties of protected field and growth, yield, quality of tomato analyzed. By which, we make sure that soil improvement effect by different measures. By this study, to provide the theoretical basis and technical support for soil improvement and rational fertilizing of tomato, achieve sustainable utilization of soil resources. The main results are as follows:1. With the extension of planting years in protected field, soil aggregates sizes(10-0.25mm) aggregates are increased and no-water stability aggregates more than0.25mm is decreased;the percentage of water stability aggregates more than0.25mm is increased obviously, so as WMWD, damage ratio of water stability aggregates is decreased; soil bulk density and porosity are reduced, pore porosity and total porosity enhanced, ratio of pore porosity and field capacity, capillary moisture capacity, saturation moisture capacity are reduced. Changes of these indexes are similar in0～15cm and15～30cm soil layer and change tendency is obvious during1to10year.2. With the extension of planting years in protected field, soil’s pH value is decreased year by year. The value decreases rapidly during1to10year. After10years,81.40%of protected field soils appear a weak acid. Soil acidification degree in0～15cm and15～30cm depth are similar. Soil electrical conductivity increased, the electrical conductivity of30years is0.68mS/cm, higher4times than outside corn field and exceeds the critical plant reproductive.3. With the extension of planting years in protected field, different soil salt ions are increased, they increase quickly before planting5or10years,10years later, reach the highest amount. When30years, the contents of Na+, HCO3and Cl-are reduced slowly or keep the same as after20years’. At the same time, contents of K+, Ca2+, Mg2+and SO42-increased obviously. The salt ions are higher in0-15cm depth than in15-30cm depth. When30years, the salt contents are1.75g/kg and1.50g/kg respectively, which are3times than outside corn field.4. Large amount of fertilization and irrational structure of fertilization are general in protected field. With the extension of planting years, protected soil nutrients accumulate obviously before planting5or10years,10years later, reach the highest amount. Soil nutrient content is higher in0-15cm depth than in15-30cm depth. Except contents of total potassium and available boron shows a decreasing trend, contents of soil total N, total P, available N, P, K, Ca, Mg,5, Fe, Mn, Cu and Zn increasing.5. With the extension of planting years in protected field, contents of soil microbial biomass C and N increased first then decreased, reach the summits (497.2mg/kg and172.2mg/kg) in10years and30years respectively.10years later, the content of soil microbial biomass C is reduced, SMBN/TN enhanced. The rate of C/N is the highest when planting5years, then it is decreased. Compared with outside corn yield, the contents of soil microbial biomass C and microbial biomass N are increased in protected field, in0-15cm depth are higher than in15-30cm depth.6. The ratio of soil aeration porosity to capillary porosity,>0.25mm of water stability aggregates and no-water stability aggregates, DMWD of no-water stability aggregates are all increased by applying potassium humate, Zeolite or both. Compared with the soil before planting,>0.25mm size of soil water stability aggregates are increased, percentage of0.25-0.106mm size of soil aggregates are decreased. The destruction rates of water stability aggregates are decreased, the WMWD increased. The effect of soil improvement is the best by application ameliorant, and then optimized fertilization and soil testing and formulated fertilization.7. Soil pH value can be reduced and electrical conductivity be increased by soil testing and formulated fertilization, optimized fertilization or optimized fertilization with ameliorant. Optimized Fertilization with Potassium humate and Zeolite is the best treatment to reduce the content total salt and salt ions, Potassium humate can reduce the contents of Ca2+、Na+、Mg2+better than Zeolite, other Zeolite can reduce the contents of SO42-, Cl-better than potassium humate. The content of soil total salt rise with the contents of Na+, Ca2+, Mg2+, HCO3-, Cl-, SO42-in protected soil.8. Compare with farmer conventional fertilization optimized fertilization and optimized fertilization combined with ameliorant treatments can reduce the contents of nitrate nitrogen, available nitrogen and available P, optimized fertilization combined with Potassium humate is best. Less potassium is applied by farmers, so the content of K is less than of optimized fertilization,but similar to optimized fertilization combined with ameliorant treatments, this showed that the contents of nutrients can be decreased by optimized fertilization combined with ameliorant.9. The contents of soil microbial biomass C and N can be increased by optimized fertilization or optimized fertilization with ameliorant.The ratio of soil microbial biomass C and microbial biomass N is highest by the treatment of optimized fertilization with potassium humate and Zeolite.10. Chlorophyll content, net photosynthetic rate, transpiration and water use efficiency of tomato leaves can be improved by optimized fertilization or optimized fertilization with ameliorant. The effect of optimized fertilization with Zeolite is the best, the second is optimized fertilization.11. Compared with farmer conventional fertilization, tomato yield in optimized fertilization treatment and optimized fertilization with potassium humate are increased by20.5%and36.9%respectively, Vc are increased by15.1mg/kg and35.6mg/kg respectively, sugar-acid ratio are enhanced1.2and1.7times, the content of nitrate and nitrite are decreased; income are increased by1294.9yuan/667m2and3012.5yuan/667m2. Considering tomato production, quality and income, Optimized Fertilization with potassium humate and Zeolite is best. Appilying potassium humate is better than Zeolite, and potassium humate can make firut early-maturing5-7days.