| As a kind of important cultivate method that could have labor saving and high efficiency, zero tillage has aroused general concern in the world. Impact of rice-oilseed rape multiple cropping and no-tillage on soil characteristics and growth and physiology effects of rice were studied by using field experiment and laboratory analysis in Hunan Agricultural University (Changsha site) and Shimen County (Shimen site) in Hunan Province in 2003-2005, and the effects of different fertilizer-N application on growth and yield formation of raised seedlings and transplanted rice under no-tillage and conventional tillage conditions were also researched in 2003-2004 .The results as followings:1 Effects of rice-oilseed rape multiple cropping and zero tillage on soil physical properties (1) In Changsha site(Tidal clayey paddy soil derived from river alluvium),the bulk density in 10~20cm soil layer in no tillage and direct broadcasting(NTDB) was 3.81% lower than those in conventional tillage and direct broadcasting(CTDB), while total porosity in the same soil layer of NTDB was 3.43% higher than that of CTDB. Compared with CTDB, the capillary porosity in 0~5cm and 10~20cm soil layer of NTDB increased by 6.09% and 11.14%, respectively, while aeration porosity in the same soil layer decreased by 13% and 16.19%, separately. Furthermore, the capillary moisture capacity in 5-10cm and 10~20cm soil layer of NTDB was 5.69% and 17.95% higher than those of CTDB, respectively. The contents of big aggregate (>0.25mm) and 0.001-0.05 mm microaggregate in NTDB were higher than those in CTDB, and also the dispersion coefficient of soil of no tillage decreased as the time goes on. The bulk density in 5-10cm and 10~20cm soil layer in no tillage, raised seedlings and transplanting (NTRT) was 5.13% and 4.66% lower than those in conventional tillage, raised seedlings and transplanting (CTRT), respectively, while total porosity in same soil layer of NTRT was 4.66% and 4.62% higher than that of CTRT. In comparison with CTRT, the capillary porosity and capillary moisture capacity in 5-10cm soil layer of NTRT increased by 7.85% and 3.98%, respectively, while the aeration porosity in 0~5cm and 5~10cm soil layer decreased by 33.95% and 6.32%, separately. The contents of big aggregate (>0.25mm) and 0.001-0.0 lmm microaggregate of soils increased under the no-tillage condition, and the contents of <0.001mm and 0.25~0.005mm microaggregate slightly decreased as well. The contents of sand and dispersion coefficient ofsoils decreased under no-tillage condition, and the contents of silt and clay and structural coefficient increase as well. It was obvious that no-tillage would be beneficial to the formation of soil structure and improvement of soil fertility.(2) In Shimen site(Yellow clayey paddy soil derived from slate and shale weathered material), the bulk density in 10~20cm soil layer of NTDB was 3.53% lower than those of CTRT, while total porosity in the same soil layer of NTDB was 1.89% higher than that of CTRT. Compared with CTRT, the capillary porosity in 5~10cm and 10~20cm soil layer of NTDB increased by 4.08% and 5.11%, respectively, while the aeration porosity in 0~5cm, 5~10cm and 10~20cm soil layer deceased by was 3.61%, 55.71% and 63.00%, separately. The capillary moisture capacity in 10~20cm soil layer of NTDB was 5.73% higher than those of CTRT, respectively. The contents of big aggregate, 0.25~0.05mm and 0.001~0.005mm microaggregate of NTDB were higher than those of CTRT, but the contents of 0.01-0.05 microaggregate were in contrary state, and the dispersion coefficients of soil of no tillage were lower than those of CTRT.2 Effects of rice-oilseed rape multiple cropping and zero tillage on soil chemical properties(1) Effects of rice-oilseed rape multiple cropping and zero tillage on soil pH value and nutrient contents.The pH value does not decrease under the no-tillage condition, so no-tillage would not lead to the acidation of soils. In Changsha site, The contents of organic matter (O.M), total N(TN), available N(AN) and available P(AP) in 0~5cm soil layer of NTDB were 3.32%,15.60%,8.34% and 36.64% higher than those of CTDB, separately, In addition, the contents of O.M,TN, total K(TK) and AP in 0~5cm soil layer of NTRT were 6.00%,17.25%,4.61% and 12.70% higher than those of CTRT separately. In Shimen site, the contents of O.M, TN, total P, TK, AN and AP in NTDB were 9.32%,8.49%, 24.29%,11.43%,9.82% and 46.99% higher than those of CTRT. It was obvious that no-tillage would be beneficial to enrichment of the soil nutrient in the surface layer soils and would not lead to the acidation of soil.(2) Effects of rice-oilseed rape multiple cropping and zero tillage on soil redox characteristics.The redox potential in 0~5cm, 5~10cm and 10~20cm soil layer of NTDB was 28.60%-105.10%, 86.60%~l78.74% and 41.90%~63.95% higher than those of CTDB, respectively. In comparison with CTRT, redox potential in 0~5cm ,5~10cm and 10~20cm soil layer of NTRT increased by 6.23%~73.43%,59.06%~207.43% and 17.06%~l 84.58%, respectively. It was obvious that the redox potential would increase under no-tillage condition, which is beneficial to improvement of aeration status and conservation of root activity at early growth stage. The contents of total reduction matter, active reduction matter, Fe2+and organic active reduction matter of soils of no-tillage were lower than those of conventional tillage.3 Effects of rice-oilseed rape multiple cropping and zero tillage on soil enzyme activity. The unease activity and phosphatase activity of soil in no-tillage was lower than those inconventional tillage soil. In Changsha site, the hydrogen peroxidase activity of soil in NTDB was higher than those in CTDB, while the hydrogen peroxidase activity of soil in NTRT was lower than those in CTRT. In Shimen site, the hydrogen peroxidase activity of soil in NTDB wasgeneral lower than those in CTRT.4 Effects of rice-oilseed rape multiple cropping and zero tillage on growth and physiology characteristics of rice(1) The tillering capacity and productive tiller percentage(PTP) of rice in NTDB was slightly higher than those in CTDB. The tillering capacity, PTP, maximum tillers, plant height and effective panicle number of rice in CTRT were lower than those in NTRT, but the differences were not significant between NTRT and CTRT. It was proved that no-tillage would be beneficial to increase of the leaf area index in compassion with conventional tillage no matter which crop establishment was adopted. The net photosynthesis and net assimilate of rice leaves in NTDB were 8.70% and 46.81% higher than those in CTDB at the later growth stage. The hydrogen peroxidase activity of rice leaf of no-tillage was higher than that of conventional tillage no matter which crop establishment was adopted.(2) There were insignificant differences of the dry matter accumulation and its distribution of hybrid rice between no tillage and conventional tillage, and also the difference of total N absorbing capacity and total P were insignificant between NTDB and CTDB, while total K absorbing capacity in NTDB were higher than those in CTDB, and also the regular pattern for absorbing N,P,K were difference.(3) The spiketlet number per panicle no-tillage was higher than that in conventional tillage no matter which rice establish method was adopted, while the differences of those other yield component were not significant. The harvest yield in NTDB and NTRT were 17.33% and 3.34% higher than those in NTDB and NTRT, respectively.5 Effects of rice-oilseed rape multiple cropping and no-tillage on the root properties of rice(1) The root/shoot ratio and root dry weight in NTDB was 4.03% and 19.12% higher than those in CTDB at maximum tillering stage, and also the root/shoot ratio and root dry weight in NTRT was 32.06% and 34.26% higher than those of CTRT at the same stage. The root weight and root weight density in 0~5 cm soil layer of no-tillage was higher than those of conventional tillage, and the root length and root length density and root surface area in 0~5 cm soil layer of no-tillage was higher than those of conventional tillage on transplanting condition, and the specific root length in 5~ 10 cm and 10-20 cm soil layer of no-tillage were higher than those of conventional tillage.(2) Total 32P activity absorbed by roots in no-tillage were higher than those in conventional tillage. In addition, the partitioning of 32P absorbed by roots into aerial parts in NTDB reached to 46.93% and increased by 13.78% compared with CTDB at booting stage, while the root residual rate of 32P in NT at the same stage was 6.84% lower than that in CTDB. In comparison with CTDB, the root oxidation ability in NTDB at maximum stage, booting stage and full heading stage were 9.92%,19.80% and 26.23%, respectively.6 Effects of different fertitizer-N application on growth and yield formation of transplanted rice under zero tillage and conventional tillage conditions.(1) Application of fertilizer-N could improve the tillering capability of rice, and also the tillers per hill and tillering capability in CTRT were significantly higher than those in NTRT.With the increase in fertilizer-N application rate, the dry matter accumulation increased at whole growth stage, and also the dry matter distribution on leaf increased, while the dry matter distribution on panicle deceased.(2) With the increase in fertilizer-N application rate, the total N absorbing capacity increased at whole growth stage, and also the absorbing N proportion in NTRT at mid growth stage was significantly lower than that in CTRT, while the absorbing N proportion in NTRT at later growth stage was significantly higher than that in CTRT. Obviously, NTRT would be more beneficial to absorption of N at later stage in comparison with CTRT.(3) With the increase in fertilizer-N rate, spikelet number per panicle, harvest index, N recovery efficiency, N physiological efficiency, N agronomic efficiency and N partial factor productivity decreased, while the yield gradually increased at early stage. After fertilizer-N rate reached to definite value(no tillage is ISOkgN-ha'1, conventional tillage is 75 kgN-ha'1), the yield gradually decreased. There were no significant differences of yield and yield components between NTRT and CTRT. The N physiological efficiency and N agronomic efficiency in NTRT was higher than those in CTRT, while N partial factor productivity in NTRT was lower than that in CTRT, there were no significant differences of N physiological efficiency and N agronomic efficiency and N partial factor productivity between NTRT and CTRT.7 Effects of rice-oilseed rape multiple cropping and zero tillage on yield and yield formation of oilseed rape and economic benefit analysis of no tillage of riceOn the condition that early stubble was rice in CTDB, the effective pod number of oilseed rape in NTDB was 21.97% more than that in CTDB, and also differences of the effective pod number of oilseed rape was significant between NTDB and CTDB. The theoretic yield and harvest yield of NTDB oilseed rape was 28.58% and 7.37% higher than those of CTDB and there were significant differences of the theoretic yield of oilseed rape between NTDB and CTDB. Survey results of no tillage in Shimen County indicated that yield of NTDB rice could increase 3.62% and 11.62%, production cost could decrease 198.5 yuan-ha"1 and 680.1 yuan-ha'1, the income could raise 1 210.9 yuan-ha"1 and 1 744.8 yuan-ha'1 compared with CTDB and CTRT, respectively.
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