Effects Of No-tillage And Enhanced Efficiency Nitrogen Fertilizer On Rice Yield And Nitrogen And Phosphorus Losses:a Meta-analysis

The previous studies on no-tillage (NT) and enhanced efficiency nitrogen fertilizer (EENF) in paddy field focused on single experiment, which was regional limit and lack of universal guiding significance.In this study, the meta-analysis method-the currently best method for quantitative overview, was used to make a large-scale assessment of the effect of NT and EENF on rice yield, rice N uptake, nitrogen use efficiency (NUE) which refered to the recovery efficiency of N in our study and total nitrogen and phosphorus losses, and to compare the different effect of NT all over the world and EENF in China on rice yield, NUE and total nitrogen and phosphorus losses in different conditions (different physical and chemical properties of soil, rice cultivation methods, tatal N rate, etc.), which was aimed to obtain quantitative data and the favorable conditions to use NT and EENF in paddy field, and provide a scientific basis for evaluating the economic, social and environmental benefits for the application of NT and EENF in paddy field. The conclusions were as follows:(1) No-tillage (NT) led to a 3.83% reduction in rice yield compared with conventional tillage (CT). Soil pH had a significant effect on rice yield (P< 0.05), there was a negative effect on rice yield when the soil pH value was more than 7.5, and pH between 6.5 and 7.5 was favorable for rice yield under NT; it showed distinctly negative effect for rice yield when NT was applied on sandy soil (P< 0.05); it showed negative effect for rice yield when rice was planted by direct seeding, but the negative effect was not obvious for rice yield when rice was planted by transplanting and cast transplanting; it did not change the negative effect of rice yield under NT whether rotation was applied or not due to the short duration years of rotation in rice paddy under NT; it was favorable to weaken the negative effect on rice yield when straw was returned to the paddy field under NT, it made the rice yield reduce by 3% and 1% when straw was removed from the paddy field and returned to the paddy field under NT; in terms of total N rate, the tatal N rate had a significant effect on rice yield under NT (P< 0.05), and 120-180 kg·hm-2 was the good practice to get equal rice production compared with CT; in order to obtain the equal yield, the duration time of NT should not be less than 3 years. In addition, NT made the rice N uptake and NUE reduce by 5.4% and 16.64%. NT made rice N uptake and NUE reduce by 6.29% and 18.41% when straw was removed from paddy field compared with that under CT, and there was no significant effect on N uptake and NUE of rice when straw was returned to the paddy field; in terms of planting method, it was consistent for the effect of NT on rice N uptake and NUE, direct seeding made them both reduce significantly, but transplanting and cast transplanting had no significant effect on them. Finally, NT made the total nitrogen (TN) and Total phosphorus (TP) increase by 15.45% and 40.06%. In terms of rotation, our study suggested that it was favorable for reducing the TN loss by runoff when rotation was applied; the straw returned to rice paddy was conducive to reduce the TN and TP loss by runoff.(2) Our study on EENF suggested that, on average, the application of EENF made rice yield, N uptake and NUE increase by 7.5%,10.5% and 48.53%, respectively. In terms of factors, it was found that soil pH had a significant effect on rice yield, N uptake and NUE (P< 0.05), and it was favorable for them to use EENF in alkaline soli of paddy field; coated slow/controlled release nitrogen fertilizer (CRF) made the rice yield, N uptake and NUE increase significantly, but nitrification inhibitor had no significant effect on N uptake and NUE of rice which was possible due to the nature of the nitrification inhibitor (stability, mobility and inhibitory strength) and soil, climate conditions and nitrification-denitrification rate; EENF applied as basal fertilization was better than split fertilization; the better practice for N rate was 120-180 kg-hm"2. In addition, the TN loss by runoff and by leaching in paddy field were reduced by 42.62% and 27.58% when EENF was applied. In terms of factors, it suggested that the total nitrogen rate of 120～180 kg·hm-2 was good practice to reduce the TN loss by runoff and by leaching in paddy field. In addition, it reduced the TN loss by runoff and by leaching in paddy field by about 10% and 20%, respectively when 15%～65% of the N rate of EENF appled into the paddy field was cut.