Effects Of Combined Application Of Organic And Inorganic Fertilizers On Soil Improvement In Newly Reclaimed Saline-alkali Wasteland

Low soil fertility, high salt content, poor water and fertilizer retention properties were commonin newly saline-alkali wasteland of the Yellow River Gansu high lift irrigation area. Under salineconditions, crop growth inhibited by itselves. If fertilization was inappropriate, it not only decreasedcrop yeilds, but also increased soil salt damage, and caused crop yield reduction and even totalcrops failure. The purpose of this study is to investigate effects of combined application of organicand inorganic fertilizers on soil salt transfer, desalting effect, soil fertility, physical properties andmaize nutrient uptake and utilization, biological characteristics, physiological indexes in Gansunewly reclaimed saline-alkali wasteland, explore the optimal ratio of organic and inorganic fertilizer,so as to improve newly reclaimed saline-alkali wasteland by utilizing it. The feild experiment wasconducted combination design with two factors and three levels in total nine treatments. Nitrogenfertilizer (N) arranged three levels of0,300,600kg/hm2(nutrient content), and organic fertilizer (M)arranged three levels of0,12,24t/hm2(fertilizer content). Each treatment had three replicates. Weperformed randomized block in this experiment and used maize as indicator crops. The main resultswere obtanined as follows:1. The mean conductivity of N0M12, N0M24was significantly lower than the other treatmentin0-60cm layer. The changes of soil salt content had no obvious rule in treatments in60-80and80-100cm soil layer. Soil desalination and resalinization mainly occurred in the layer above60cm.The average desalination rate was about45%after the first crops harvest season and the averageresalinization rate was about38%in spring of the second year. Effect of desalination in N0M12andN0M24treatments were optimal, reached to64.88%and68.37%. This explained that applyingorganic manure was an effective measure to improve soil desalting efficiency and inhibitresalinization.2. Combined application of organic and inorganic fertilizers could significantly improve thesoil fertility in newly reclaimed saline-alkali wasteland. Compared with CK, soil organic matterincreased by5.96%~24.00%，total nitrogen increased by40.28%~58.33%, total phosphorusincreased by60.47%~83.72%, total potassium increased by8.41%~15.42%, available nitrogenincreased by50.00%~113.42%, available phosphorus increased by193.33%~312.38%, andavailable potassium increased by5.84%~18.50%. Effect of nitrogen fertilizer on soil nitrogen was significantly higher than that of phosphorus and potassium, and organic fertilizer mainly improvedsoil phosphorus supply levels.3. At the same nitrogen level, increasing organic fertilizer application could make soil bulkdensity decrease by2.91%~8.02%,1.49%~9.15%and0.72%~9.15%in0~10cm,10~20cm,and20~40cm layer, respectively. And at the same organic fertilizer level, all soil bulk densitychanges were not obvious by increasing nitrogen fertilizer. But soil porosity change was opposite tobulk density. Effects of different combined fertilization on soil water infiltration rate and averagedegree of compaction in0~45cm were not obvious.4. Maize seedling plant height increased with the increase of organic fertilizer, and was nolonger outstanding with the increase of nitrogen, organic fertilizer. Maize leaf SPAD valuesgradually increased with the extension of growth period. The difference in jointing stage was moresignificant than huge bellbottom period. Differences between the other treatments were notsignificant except N0M0treatment in huge bellbottom period. Effect of organic fertilizerapplication on net photosynthesis rate was particularly prominent, and N0M24treatment eached tothe peak. Single fertilizer application could increase electrolyte leakage rate, and increasedsignificantly with the increase of fertilization. Effects of combined fertilizer application were betterthan that of single application.5. Fertilization could significantly increase maize grain yield by13.4%~168.8%. Excessiveapplication of nitrogen fertilizer could injure maize leaves and affect straw yield. Both nutrientcontents and uptakes of maize plants improved significantly with the increase of fertilization. Grainwas the main body of nitrogen and phosphorus absorption, but straw was that of potassiumabsorption. Combined application of organic and inorganic fertilizers could promote maizeabsorption of N, P, K nutrients. Under our experimental conditions, nitrogen utilization ratio was14.47%~20.74%in different treatments; Partial factor productivity from applied N was11.06~25.69kg/kg; Agronomic efficiency of applied N was3.04~11.40kg/kg; Physiological efficiency ofapplied N was rate o20.08~56.63kg/kg, the overall were relatively low. The main reasons werethe lower utilization of organic fertilizer in this year and less contribution to total nitrogen content.The recommended amount of nitrogen applied was300kg/hm2and that of organic manure was24t/hm2in this study area by considering soil salt transfer, desalting effect, soil fertility, physicalproperties and maize nutrient uptake and utilization, biological characteristics, and so on. The recommended fertilization rate in other regions of the Yellow River irrigation area needs to adjustslightly because of the big saline-alkali soil spatial variability.