Changes Of Black Soil Fertility Under Long-term Fertilization

This study was under the long-term fertilization in black soil (harbin), which had 24 treatments from the year of 1979, under the rotation of wheat-soybean-corn, investigated the changes of black soil fertility under long-term fertilization, results showed that:Soil organic matter (SOM) had big changes under different fertilization about 31 years. The content of SOM under no fertilizer (CK) decreased from 26.6 g/kg to 22.3 g/kg, about 16.2%; the treatment of chemical fertilizer (NPK) also made the SOM conternt decreased, which was less than CK, from 26.6 g/kg to 23.5 g/kg, about 10.3%; content of SOM increased under treatment of manure (M) and manure combined with chemical fertilizer (MNPK); the content of SOM increased significantly under the treatment of higher amount of manure combined with nitrogen and phosphorus fertilizers (M2N2P2).Treatment of MNPK could increase content of SOM and improve soil fertility.Content of soil total nitrogen (N) decreased 15.6% under the treatment of CK, well the conternt of total N undern treatments of nitrogen fertilizer (N) and NPK decreased less than CK. Long-term manure fertilization could keep balance of soil nitrogen, treatment of MNPK could increased contents of soil total N, alkaline-N and inorganic N, keep and improve soil N balace, increase potential deliverability of N.Contents of soil total phosphorus (P) and available P decreased 39.3% and 70% respectively, well they decreased 25.2% and 41.5% under treatment of M. A lots of P were accumulated in soil under long-term P fertilizer utilization, and the amount increasing with the amount of P fertilizer utilization increasing. When used the normal amount P fertilizer, contents of total P and available P increased 29.0% and 3 times; content of total P increased 44% and available P increased 3.8 times under treatment of MNPK; two times amount of P fertilizer made soil P content increased 68.2%, two times amount of P fertilizer combined with two times manure made soil P content increased one time and available P increased 6.7 times. P fertilizer had big influence on Ca2-P,Ca8-P,Al-P, which had more availability, and had small effect on Ca10-P,O-P, which had lower availability. The accumulated P in soil always existed as available form. Through the biological experiment, accumulated P in soil could be absorbed and utilized by crops.Long-term fertilization had small influence on soil total kalium (K). Soil total K content had decreased trendency under long-term no fertilizer and no K fertilizer, the available K content decreased during the years, well content of total K increased under long-term K fertilizer utilization, the available K decreased, treatment of MNPK could increase soil available K, we should pay more attention on potential short of K.Long-term N fertilizer (urea) utilization made soil acidification, during the amount increasing, the pH value decreasing a lot. The pH value decreased from 7.22 to 5.94 (N) and 5.00 (more amount of N fertilizer), about 1.28 and 2.22 untis during 31 years. Treatments of NPK and MNPK could release the soil acidification, NPK decreased 1.22 units, and the MNPK is 1.14 units.The contribution rate of N fertilizer to yield of wheat is 52.6%, P fertilizer is 27.1%, K fertilizer is 19.3%, manure is 24.1%; the contribution rate of N fertilizer to yield of corn is 22.7%, P fertilizer is 18.8%, K fertilizer is 4.8%, manure is 25.0%. Fertilization had the biggest influence on wheat yield, followed by corn, the soybean yield is the lowest one. N fertilizer had the most contribution rate to crop yield, than the P and K fertilizer.