| This is a long-term fertilization situ experiment located in south loss plateau with precipitation about628mm and soil sample was from red soil. The experiment has two factors(including plantation and fallow,fertilize NP+Organic matter and non-fertilizer) with a incomplete experimental design. The treatment ofplantation includes non-fertilizer(CK),fertilizer(NP),fertilizer+low maize straw(NP+9375 kg/ha),fertilizer+medium maize straw(NP+18750 kg/ha),fertilizer+high maize straw(NP+37500 kg/ha) andfertilizer+manure(NP+37500 kg/ha).The treatments of fallow include fertilizer+low maize straw(NP+9375kg/ha).Soil samples are from 0-20cm,20-40cm and 40-60cm in soil profile after 25 years of the long-termsitu experiment, we used two laboratory incubation methods(aerobic incubation and water-loggedincubation) and exhausted pot experiment to measure and compare soil nitrogen availability in this researchto study the influence of long-term fertilization on soil nitrogen availability. Technological support wasexpected to maintain the fertility and manage fertilization in this area. Through the research, conclusionswere drawn as followed:1,Mineralization of organic nitrogen in long-term water-logged incubation and aerobic incubation hassimilarity and also difference of samples from 0-20cm,20-40cm and 40-60cm in soil profile. The similarityis that they both show a same process, the process can be divided into two periods: initial indexmineralization period with fast speed and slow speed mineralization period. The difference is that the initialindex mineralization period was shown in the first week in aerobic incubation but that was in the first twoweeks in water-logged incubation; the trend of nitrogen mineralized increased in water-logged incubationuntil 42 days but it was steady in aerobic incubation after 7 days. It indicated that the first 7days was mainmineralizable period for aerobic incubation and the first 14 days was main mineralizable period forwater-logged incubation, then amount of mineralizable nitrogen is very little in aerobic incubation and themineralizable speed decreased significantly. The amount of mineralizable nitrogen in the long-term aerobicincubation was higher than that in the long-term water-logged incubation, the amount measured inaerobic incubation over twice than that in water-logged incubation, even the amount of minerlizablenitrogen of 7 days in water-logged incubation was higher than that in aerobic incubation after 42 days.2,The amounts of mineralizable nitrogen in long-term water-logged and aerobic incubation were less thanthat of plant growing period in pot experiment obviously: As for average, amount of mineralizable nitrogenprovided during plant growth was 1.87 times (not including root) and 3.09 times( including root) than thatin long-term water-logged incubation;4.51 times(not including root) and 3.09( including root) times thanthat in long-term aerobic incubation. The correlation show that whatever including root or not; consideringinitial nitrate in soil or not, the mineralizable nitrogen occurred in two incubation methods has a greatsignificant linear relationship with nitrogen absorbed in plant(including all soil samples).The creature potexperiment still is the best way to evaluate the influence of long-term fertilization on soil nitrogenavailability.3,As for nitrogen absorption in Lolium multiflorum L.of the pot experiment which soil samples withlong-term fertilization, average nitrogen provision of 0-20cm,20-40cm and 40-60cm is 318.5mgN/pot,145.7 mgN/pot and 120.2mgN/pot,respectively; decrease by turn; decline suddenly from 0-20cm to20-40cm,decline very little from 20-40cm to 40-60cm;soil nitrogen availability of different soil profiledecrease as the soil depth increased with different fertilization treatment. The total mineralizable nitrogenin 0-20cm,20-40cm and 40-60cm was 55.0%,25.2% and 19.8%of the total mineralizable nitrogen in0-60cm profile, respectively. It indicated that the mineral... |
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