Effects Of Different Rice Cultivationmodes On Crop Yield, Nitrogen Use Efficiency And Soil Fertility In Rice-Barely Rotation System

In order to provide a theoretical basis for rice cultivation mode in aerobic soil condition, a field experiment was conducted in Yancheng Academy of Agriculture Science, Jiangsu province from 2005 to 2006 and such parameters were determined as plant biological traits, nitrogen use efficiency differences, mineral nitrogen dynamic changes.In rice season, the treatments included a waterlogged cultivation (W), aerobic cultivation with plastic film mulching covered (PF), aerobic cultivation with rice straw mulching covered (RS) and aerobic cultivation without any mulching (B). After rice season barley was planted with nothing mulched in all treatments. Accordingly, the post-barely treatments was marked as post-waterlogged soil treatment (PW), post-plastic film mulching treatment (PPF), post-rice straw mulching treatment (PRS) and post-no mulch treatment (PB), respectively.Compared with W treatment, RS treatment could meet or exceed yields of rice. In year 2005 the yields of rice grains in RS was 13% higher than W, and in year 2006 both the treatments had a same yield. Also, rice cultivation in aerobic soil condition had a good effect on post barely grain yields compared with W. Treatment. PRS had a highest grain yield that was 23%, 4% and 14% higher than PW, PPF and PB, respectively. Rice cultivation in aerobic soil with rice straw mulching significantly increased soil productivity of rice-barely system, which was 13%, 10% and 23% higher than PW, PPF and PB, respectively.More or a same nitrogen amount was accumulated in rice in RS treatment compared with W treatment. On average year, total nitrogen accumulation in plants was found in the order of RS＞W＞PF＞B. Rice cultivation in aerobic condition significantly increased post barely to accumulate nitrogen. Barely in PRS treatment accumulated a maximum nitrogen that was 21%, 6% and 14% higher than PW, PPF and PB, respectively.Fertilizer nitrogen use efficiency by rice in RS treatment could meet or exceed W treatment, but fertilizer nitrogen use efficiency of rice in treatment PF and B was significantly lower than traditional paddy rice. After two years' study, it was found fertilizer nitrogen use efficiency by barley could be improved by pre-aerobic cultivation rice. Maximum fertilizer nitrogen use efficiency was found in PRS, and it was 38%, 3.6% and 16.2% higher than PW, PPF and PB, respectively.Soil NH₄⁺-N content in W was much higher than aerobic cultivation of rice during the rice growth period. In year 2005, soil NH₄⁺-N had no significant difference in vertical distribution, but soil NH₄⁺-N decreased rapidly from 0-20 cm to layer 60-80 cm in year 2006. W treatment had maximum NH₄⁺-N in each layer. In layer 0-20 cm and 20-40 cm, NH₄⁺-N performed as, RS＞PF＞B, while PF had a NH₄⁺-N content higher than RS and B in layer 40-60 cm and 60-80 cm. Rice cultivation mode had a profound effect on surface soil NO₃^--N content during rice growing periods. On average year, NO₃^--N in W treatment significantly was lower than in aerobic condition. Of all aerobic treatments, RS had a higher soil NO₃^--N than other two treatments in year 2005, and in year 2006 the soil NO₃^--N contents were in the order of RS＞PF＞B. There existed a vertical distribution of soil NO₃^--N content that was reduced from 0-20 cm to 60-80 cm layer. Soil NO₃^--N in aerobic condition was much higher than in W in layer 0-20 cm and 20-40 cm and RS had a higher NO₃^--N content than PF and B in these two layers. But in layer 40-60 cm to 60-80 cm, RS had a much lower NO₃^--N content than the other two aerobic treatments. Soil NH₄⁺-N did not have any differences during barely growing periods between each treatment, and no variation in vertical directional distribution either. Unlike soil NH₄⁺-N in barely-grown season, NO₃^--N had a grade concentration that was reduced from surface to layer 60-80 cm. Soil mineral nitrogen measured before rice transplanting and barley sowing each year, it was found that PRS and PPF treatment increased soil mineral nitrogen by 65.4% and 90.2%, respectively, compared with W.Rice with straw mulching significantly improved soil microbial biomass. RS, for example, had maximum microbial biomass C, and it was 50.7%, 18.1% and 31.9% higher than W, PF and B, respectively. Also RS had maximum microbial biomass N, and it was 48.9%, 55.4% and 11.83% higher than W, PF and B, respectively. By comparing the changes of soil fertility in different rice cultivation modes for five years, it was found that rice cultivation mode had a profound impact on soil fertility. W and RS significantly increased soil organic matter by 10.6% and 14.3%, total soil nitrogen by 19.8% and 28.6%, respectively, compared with those at the beginning of the experiment. However, PF reduced soil organic matter and total soil nitrogen by 15.2% and 12.1%.We conclude that rice cultivation in aerobic soil with straw mulching could improve soil fertility, and thus assure a higher crop production and water use efficiency.