| From 2012 to 2016, soil nutrient pools and environmental effects of different fertilization systems(chemical fertilizer(CF), cattle manure(CM) and combination of cattle manure with chemical fertilizer(MF)) were studied under a long-term fertilization experiment started in 1986 with winter wheat-summer maize rotation system. The main findings of this thesis were as follows:1. Effects of different fertilization systems on crop yields and quality. When equal N rates(rates applied referring to local farmers) were applied, there was no significant difference in crop yield among CF, CM and MF after 26 years. It confirmed that the long-term(26 years) application of cattle manure(CM) or 50% cattle manure combined with 50% chemical fertilizer(MF) could achieve the same level of crop yield as chemical fertilizer(CF). It was also found that there was no significant yield increase effect under long-term(26 years) double rates input of chemical fertilizer(HF) or cattle manure(HM). Compared with the control(no fertilizer input, i.e. CK) treatment, the protein contents in maize grain were significantly increased by 12%-18% with CF, CM or MF, and the increase effects were more significant under HF and HM. When equal N rates were applied, no significant difference in grain protein contents was found among CF, CM and MF.2. Effects of different fertilization systems on fluvo-aquic soil physical fertility. Compared with CK, the long-term fertilization(chemical fertilizer, cattle manure and combination of cattle manure with chemical fertilizer) significantly decreased soil bulk density and increased soil total porosity after 26 years. Compared with chemical fertilizer, long-term application of cattle manure or combined with chemical fertilizers significantly decreased soil bulk density and increased soil total porosity. Compared with chemical fertilizer, long-term application of cattle manure significantly increased the soil water stable aggregates at the ratio of >0.25 mm diameter. Compared with the chemical fertilizer, long-term application cattle manure and combination of cattle manure with chemical fertilizer significantly increased soil water content at the same soil matric potential. This demonstrated that long-term application of cattle manure or combined with chemical fertilizers could improve soil water retention and reduce drought risk.3. The characteristics of fluvo-aquic soil carbon pool under different fertilization systems.Compared with chemical fertilizer(CF), long-term application of cattle manure(CM) or combination of cattle manure with chemical fertilizer(MF) could increase soil total C, labile organic C and humus C content significantly by 53%-136%, 81%-189% and 112%-158%, respectively, and the increase effects were more significant under HF and HM. Compared with chemical fertilizer, long-term application of organic manure or a combination of organic and chemical fertilizers increased the ratio of HA/FA, and improved the quality of soil humus.4. The characteristics of fluvo-aquic soil nitrogen pool under different fertilization systems.When equal N rates were applied, compared with chemical fertilizer(CF), long-term application of cattle manure(CM) or combined with chemical fertilizer(MF) could significantly increase soil total N and organic N contents by 38%-60%, and the increase effects were more significant under HF and HM.Meanwhile, the manure treatments(CM) significantly decreased soil nitrate contents by 33% and 60%in 0-20 cm and 20-40 cm soil layers respectively. The organic N in soils no matter form long-term application of chemical fertilizer(CF), cattle manure(CM) or combined use of cattle manure with chemical fertilizer(MF), was dominated by acid hydrolysable N accounted for 74%-88%, and amino acid N, ammonium N and hydrolysable unidentified N were affected significantly by different fertilization systems.5. The characteristics of fluvo-aquic soil phosphorous pool under different fertilization systems. Compared with the control treatment, the long-term fertilization treatments(chemical fertilizer,cattle manure and combination of cattle manure with chemical fertilizer) increased soil total P, inorganic P, organic P, available P by 51%-147%, 61%-174%, 36%-218% and 5-72 times, respectively. Long-term application of cattle manure or combined with chemical fertilizer increased soil Ca2-P, Ca8-P, Al-P and Fe-P content, while long-term application of chemical fertilizer increased soil Ca8-P and Al-P content.Long-term application of cattle manure increased soil labile, moderately labile, moderately stable and highly stable organic P content significantly, while long-term application of chemical fertilizer significantly increased soil moderately labile organic P content.6. The characteristics of fluvo-aquic soil potassium pool under different fertilization systems.Compared with the control treatment, the long-term fertilization treatments(chemical fertilizer, cattle manure and combination of cattle manure with chemical fertilizer) had no significant effects on soil total K and mineral K. But the doubling the application rate of cattle manure treatment could increase soil slowly available K by 15%. Compared with chemical fertilizer, long-term application of cattle manure increased soil available K by 81%, and the higher the input rate of fertilizer(HF) or manure(HM), the more the increase of soil available K.7. Effects of different fertilization systems on fluvo-aquic soil trace elements content.Compared with chemical fertilizer, long-term application of cattle manure or combinated with chemical fertilizers significantly increased soil total and available Zn, Cu contents by 18%-32%, 17%-30%,27%-141% and 268%-496%, respectively. Meanwhile, the concentrations of Cu, Zn in wheat and maize grains also significantly increased. This indicates that adding cattle manure or combined with chemical fertilizers is an effective way to increase soil trace elements and improve grain quality consequently.8. Environmental effects of different fertilization systems.(1) Soil Ammonia volatilization.Compared with control treatment(CK), long-term fertilization systems of CF, CM or MF increased soil ammonia volatilization, and the higher the input rate of fertilizer(HF) or manure(HM), the more soil ammonia volatilization occurred. Ammonia volatilization was found higher in soil of CF treatment than those in soils of CM or MF under the condition of equal N input rate and this indicated that organic manure or combined with chemical fertilizer could reduce N loss by soil ammonia volatilization.(2)Nitrous Oxide emissions. Compared with the control treatment(CK), the long-term fertilization treatments of chemical fertilizer(CF), cattle manure(CM) or combination of cattle manure with chemical fertilizer(MF) increased soil N2 O emissions. Soil N2 O emission was increased with the input rate increase no matter long-term application of cattle manure or long-term application of chemicalfertilizer. When the equal N rate was applied, the chemical fertilizer treatment(CF) had higher soil N2 O emissions than that of organic manure(CM) or combination of cattle manure with chemical fertilizer treatment(MF). This demonstrates that application of organic manure(CM) or combined with chemical fertilizer(MF) could reduce soil N2 O emission compared with chemical fertilizer treatment(CF).(3)Soil nitrate-N concentration. Compared with the control treatment(CK), long-term fertilization systems of CF, CM or MF increased soil profile nitrate-N concentration of 0-200 cm. Soil nitrate-N concentration in the profile of 0-200 cm was higher with the input rate increase no matter long-term application of cattle manure or long-term application of chemical fertilizer. When N rate applied was equal, the chemical fertilizer treatment(CF) had higher soil profile nitrate-N content than that of the organic manure treatment(CM) or combination of cattle manure with chemical fertilizer treatment(MF),and this indicated that the environmental risk of nitrate of chemical fertilizer was higher than that of organic manure.(4) Soil heavy mental content. Available Cd and Pb in soil of CM treatment were higher than those of in soil of CF treatments by 40% and 27%, and meanwhile soil available Cd and Pb of double rate manure(HM) ware increased by 60% and 30% respectively compared with HF. There was no significant difference of soil available Cd and Pb between CF and MF. Long-term application of cattle manure(CM) increased the concentrations of As in wheat and maize grains by 42% and 65%respectively compared with chemical fertilizer treatments(CF), and meanwhile the As concentrations in wheat and maize grains of HM were higher than those of HF by 34% and 75% respectively. However,As concentrations in wheat and maize grains of CM and HM are still significantly lower than the content in the national food safety standards(GB2762-2012). There was no significant difference in As concentrations in wheat and maize grains between CF and MF. |
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