Change characteristic of fertilization and maize yield on black soil in the Northeast China

The trends of maize yield and fertilization effect on black soil were studied based on the results of 12 sites monitoring for 19 years to provide the theoretical basis of sustainable utilization.The result indicated that the amount of total nutrients(nitrogen,phosphorus,and potassium)decreased year by year during experimental periods.The average total nutrient was 500 kg/hm2 in 1988,only 91 kg/hm2 in 2006.The organic nutrients decreased significantly during 19 years.The average amount of organic fertilizer was 269 kg/hm2 in 1988,zero in 2006,meanwhile the chemical nutrients stabilized during 19 years.The average chemical nutrient was 247 kg/hm2 per year.The basis soil fertility(yield with no fertilizer)was difference in various soils.Relationship between the maize grain yield with conventional fertilizer and the basis soil fertility(yield with no fertilizer)was significant positive correlation(p0.01).The increasing ratio was significantly enhanced from 1988 to 1996.Percentage of basic soil fertility contribution to crop yield was decreased from 79% in 1988 to 42% in 1996.The percentage of basic soil fertility contribution to crop yield kept stable between 1997 and 2006,the average value was 63%.The maize yield was high and stable due to high basic soil productivity,but the effect yield increasing of fertilization on black soil was decreased with lowing amount of fertilizer with monitoring year going.