Ecological Effects Of Rice-Duck Integrated Farming System In Different Filed Scales

As one of the three staple foods in China,rice always relies on the application of chemical fertilizers and pesticides to promote high yield,which results in serious pollution,and could hardly guarantee the safety and quality.With the development of the national economy,people pay more attention on the quality and safety of rice.Current agriculture development is required to be high-quality,high-efficiency and environment-friendly,and rice-duck system treatment which is a farming method of long history in China,has high production and ecological value.Based on field experiments,by setting the control groups of three scales,namely,0.067ha(OR1),0.200ha(OR3)and 0.333ha(OR5),and the control group(CK:the conventional group which is applied chemical fertilizers),this thesis analyzed the inconsistent effects of different scales of ducks on paddy soil,paddy surface water and rice growth,and discussed the ecological effects under different scales,in order to suggest a scheme for optimizing rice-duck system treatment integrated farming under paddy-dryland rotation system.The major conclusions were made as below:1.Changes in soil physical and chemical properties were observed under long-term rice-duck farming.The soil bulk density of long-term rice-duck farming plots OR1,OR3 and OR5 was 5.3%,11.5%and 8.0%lower than CK,respectively.The soil organic matter content under three treatments was 17.6 g/kg,16.9 g/kg and 19.7 g/kg,and CK was 14.0 g/kg after two years of experiment,which was different from that before the test.OR1 and OR3 were compared.Before the test,the increase was 5.8%,9.4%,and the OR5 was reduced by 1%compared with the test before,while the CK did not change much.The contents of ammonium nitrogen in OR1,OR3 and OR5 increased by 31.2%,103.1%and 39.7%,respectively.The soil nitrate nitrogen content increased by 46.8%,25.1%and 42.6%,respectively.The soil available phosphorus content was 6.4mg.There was no significant difference between/kg,6.8mg/kg and 6.8mg/kg,and CK 6.8g/kg,which was increased by 36.9%,21.5%and 26.0%compared with before the test.There was no significant difference in available potassium.The two-year averages were 140.9 mg/kg,138.5 mg/kg,and 145.3 mg/kg,respectively,but significantly lower than the control’s 179.4 mg/kg.There was no significant difference between the pH and CK of each treatment under the three scale treatments.Compared with CK,the redox potentials of OR1 and OR3 and OR5 treated waters were 54.6%,106.7%and 68.5%lower,respectively.2.The average surface temperature of the three types of rice-duck system treatment fields was significantly lower than that of CK,which was about 0.4-0.9℃,and the cooling effect was more obvious when the temperature was higher.Compared with CK,the contents of NH4+-N in OR1 and OR3 and OR5 treatments were increased by 7.3%,19.5%,and 9.7%,respectively;the contents of NO3--N were increased by 61.9%,61.0%,and 10.9%,respectively;There is a risk of nitrogen loss in rice and duck system treatment.water-soluble potassium was decreased by 25.2%,8.1%,and 14.9%,respectively;there was no significant difference between water-soluble phosphorus treatment and CK.In addition,rice-duck farming can increase the dissolved oxygen content of water,and the dissolved oxygen content of OR1,OR3 and OR5 treatments increased by 6.0%,11.0%and 0.9%,respectively.3.Under the treatment of OR1 and OR3,the photosynthesis intensity of rice treated with rice and duck in the heading stage was 18.2%and 20.3%lower than that of CK,and there was no significant difference between OR5 and CK.Under the treatment of OR1 and OR3,there was no significant difference in root activity between rice-duck system treatment and CK treatment in the heading stage,but it was 35.1%higher than OR5.The above ground biomass of crops treated with OR1 and OR3,OR5 was 20.2%,13.9%,and 26.1%lower than CK.The yield of the three rice-duck system treatment was 24.9%,19.7%,and 24.4%lower than that of CK.Among the three treatments,the yield of OR3 was the highest,mainly because the number of effective spikes was significantly higher than the other two treatments.