The status of nutrient inputs and outputs on farmland of the Hexi corridor

Gansu Province was studied conclusively by a 24 year long-term location fertilizer experiment.Results showed that long-term continuous chemical fertilizer application made soil nitrogen(N) input—output change from a negative balance to a positive balance in the first period(1982—1990) and surplus rate was about 8.6%~19.1%.Apparent surplus rate was 29.0%~48.5% during the period with the largest balance value(1997—2005)

but soil N input-output was in a negative balance after N loss was deducted.Phosphorus(P) fertilizer input—output was still in a positive balance and surplus rate was 57.4%~68.3%.Potassium(K) fertilizer input quantity was less than uptake quantity of crop

so K input—output was in a negative balance and averaged surplus rate was-58.7%.These indicated that N and K nutrient inputs were not enough by continuous chemical fertilizer application.The long-term combined application of chemical fertilizer and organic manure could make N and P input—output be in a positive balance and surplus rates of N and P were 56.3%~61.5% and 249.9%~265.7%

respectively.Even though N loss was deducted

N surplus was still 9.4%~10.9%.K input—output was in a negative balance and average deficiency was 19.9%.Under continuous organic manure treatment

K deficiency was 45.0%.Increasing K chemical fertilization

keeping N chemical fertilization level

and combining organic manure application are scientific balanced fertilizer application techniques.