Changes Of Organic Carbon And Nitrogen Pool Of Black Soil Under Long-term Fertilization

Study on change of carbon and nitrogen pool of farm black soil is rather important to protect and rationally exploit black soil under long-term fertilizer. In this paper, based on the long-term base of national black soil and fertilizer efficiency( 1989-2004), the effects of long-term fertilizer on organic carbon and nitrogen pool of black soil and yield of corn was studied. The results were as follow:1. Effect on total organic carbon of soil. Combing organic fertilizer and NPK chemical fertilizer increased the whole of content of soil organic carbon that was increased by 27.8%⁷1.5% in 2004 compared to 1989 and annual increasing rate was 0.6g/kg¹.32g/kg. Soil total organic carbon increased 5.4% and 1.6% for abandoned and combing straw and NPK treatments, and their annual increasing rates 0.4g/kg and 0.075g/kg. Soil total organic carbon decreased 8.3% and 11.2% for nitrogen and no fertilizer treatments. The contents of soil total organic carbon were significant different for different treatments. After 15 years long-term fertilizer soil total organic carbon pools were in the order of: M₂+NPK> 1.5(M,+NPK)>M,+NPK>abandoned> straw+NPK treatments>PK> NPK>N, CK.2. Effect on humus acid carbon of soil. The whole of content of soil humus acid carbon increased 22.7%, 55.0% and 62.6% for combing organic fertilizer and NPK compared to early experiment and annual increasing rate of humus acid carbon was 0.22g/kg⁰.53g/kg. the whole of content of soil humus acid carbon increased 8.2% and 5.2% and 5.83%⁷.17% for abandoned, combing straw and NPK, chemical fertilizer and CK.3. Effect on humin carbon of soil. The whole of content of soil humin carbon of combing organic fertilizer and NPK increased 31.2%⁹0.3% compared to CK, and annual increasing rate of 1.5(M₁+NPK) and M₂+NPK treatments were 0.80g/kg and 1.21g/kg. Humin carbon decreased firstly and then increased with time for chemical fertilizer, straw+NPK and abandoned treatments. After 15 years long-term fertilizer soil humin carbon pools were in the order of: M₂+NPK>M₁+NPK>1.5(M₁+NPK)>PK, NPK> abandoned, straw+NPK treatments and CK.>N.4. Effect on composition of organic carbon of soil. For treatments of combing organic fertilizer with NPK and PK, NPK and abandoned land, the rate of humic acid carbon to humus acid carbon increased and opposite to rate of fulvic acid carbon to humus acid carbon. For treatments of combing straw with NPK ,nitrogen and CK, the rate of humic acid carbon to humus acid carbon decreased and opposite to rate of fulvic acid carbon to humus acid carbon, and the rate of humin carbon to humus acid carbon increased but sometimes decreased.5. Effect on total and available nitrogen of soil, total and available nitrogen of soil increased 15.7%⁴2.6% and 18.1%⁴1.1% for combing organic fertilizer and NPK compared to early experiment, and annual increasing rate of total nitrogen of M1+NPK treatment was 0.15g/kg;but for chemical fertilizer and combing straw and NPK, total nitrogen decreased annually. In 2004, for different treatments, total nitrogen was in the order of: M₂+NPK, 1.5(M₁+NPK)>M₁ + NPK, abandoned>straw + NPK, NPK , PK, CK, N;avail. N increased a little than that of early experiment and for different treatments it was in the order of: 1.5(M,+NPK)> M₁+NPK> M₂+NPK>NPK, straw+NPK>PK, N, abandoned, CKo6. Effect on yield and its constitution of corn. For combining organic fertilizer with NPK and straw with NPK, the yield of corn was over 3.5 times and the weight of 100 grains and the number of grain increased 47.5%⁵4.8% and 23.5%³4.6% than that of CK respectively. For nitrogen treatments, the yield of corn was over 1 times than that of CK. NPK was priot to nitrogen treatment and increased 18%. In 2004, the yield were in the order of: 1.5(M,+NPK)> M2 + NPK> Mj + NPK>straw + NPK>NPK>N>CK, PK.Generally speaking, under long-term (15 years) different fertilization measures, unbalance fertilization was no benefit for high output, and accumulation of soil organic carbon and nitrogen pool, and its effects of fertilizing was worst. Balance fertilization of NPK always made yield higher, and the change of soil organic carbon and nitrogen pool was little, compared to early experiment;combing organic fertilizer and NPK always made not only yield higher, but also soil total organic and humus acid carbon and nitrogen pool increase, and was the best fertilization mode for sustainable utilizing of black soil.