| Paddy soil occupies above 65% of the total grain area and 75% of the rice area in our country. Farmers often apply excessive N fertilizer to obtain high production. In order to reduce the nutrient waste and environmental pollution caused by excessive N fertilization and thus propose a reasonable N applying pattern, about 3362 households in Jiangxi and Hunan province were surveyed, and eight different fertilization treatments were designed in the fields. In order to discuss N supplying mechanism, seven different fertilization treatments in the lab were further designed to provide theory basis for reducing N applying. The main results and conclusions are given as follows:(1) The investigation result of customed fertilization ways of rice-rice rotation system in Jiangxi province indicated that: the average amount of N, P and K were 155 kg N/ha, 68 kg P2O5/ha and 128 kg K2O/ha in early rice, while 152 kg N/ha, 56 kg P2O5/ha and 135 kg K2O/ha were used in late rice. More than 160kg/ha of N was applied by 42% of investigated households in early rice, while 44% in late rice. For reducing N applying amount and improving N use efficiency, we mainly aimed at the households who intensively applied large amount of N. The customed N amount was fixed at 165kg/ha in early rice and 187.5kg/ha in late rice.(2) The three N applying patterns: 80% urea N plus 20% manure N (80F20M), 30% urea N plus 50% release N (30F50R) and 30% urea N plus 50% manure N (30F50M), displayed prominently in the two years'experienment. The yield and N return efficiency(NRE) of the three N applying patterns were slightly higher than the traditional N applying pattern(CFN), which were 14200kg/ha and 37.4% in average respectively. The N partial factor productivity(PFPN), agronomic efficiency(AEN) and physiological efficiency(NPE) improved 18.08%, 16.97% and 12.56% respectively, which meant it was practical to reduce 20% urea N in a short time. Considering the cost and supply ability, 30F50M pattern was recommended in the sufficient organic manure region as the leading optimization pattern(the early rice: organic manure N 82.5 kg/ha+ inorganic urea N 49.5 kg/ha, the late rice: organic manure N 93.8 kg/ha+ inorganic urea N 56.2 kg/ha).(3) Because massive available N existed in the soil solution at the tillering stage, soil available N, plant total N and N supplying surplus were high. Soil available N of the traditional N applying treatment(CFN) was higher than other treatments. There were no significant differences in plant uptake N. Because of the tillering and heading fertilization, soil available N and plant uptake N quantity of 80F20M and CFN were close after heading period. Although the total N amount reduced by 20% and no heading fertilization in 30F50M treatment,there were no significant differences in soil available N, plant uptake N and N uptake situation in each stage, which explained that 30% urea N plus 50% manure N could satisfy the soil and plant needs. Because release fertilizer decomposed slowly, soil available N and plant uptake N of 30F50R treatment were less, but there were no significant differences with CFN treatment in the mature period.(4) Culturing 0~49 days, soil accumulative production of N of applying 100% urea N(CFN) treatment was higher. After culturing 49 days, treatments with organic manure or straw were similar with CFN treatment. After culturing 88 days, soil accumulative production of N reached 180kg/ha. 30% urea N plus 50% manure N (30F50M) treatment improved soil mineralization potential by 11.73%. In the tillering period, plant uptake N occupied more than 50% of soil supplying N. In later period the proportion was also high. Soil supplying N and plant uptake N ability matched the best.To sum up, the treatment of applying 30% inorganic urea N plus 50% organic manure N (30F50M) not only guaranteed high yield and high N use efficiency, but also its soil supplying N ability satisfied plant uptake N ability, and had the biggest improvement function to soil supplying N potential. It was the best N applying pattern.
|
PDF Full Text Request