| The Weibei dryland, located at the southeast part of the Loess Plateau, is a typical rain fed agricultural region and its planting system is mostly one harvest per year. Winter wheat and spring maize are two major grain crops planted in this region. There is a great meaning to keep high production of these two crops, with the ojective to develop agriculture sustainably, at the Weibei drylandand and the Loess Plateau, China. The grain yields of these two crops depend greatly on precipitation that is retained in soil as soil water. Local farmers always adopt conventional ploughing method(P, deep plowing) to improve and maximize soil water after crop harvest. Nevertheless, excessive plowing often results in unpleasant consequences. No-tillage(N) and subsoiling tillage(S) are other two soil tillage treatments, which has been studied as an alternation to sole the problems of conventional ploughing. Applying single soil tillage measures for a long time causes soil compaction, poor rainwater storing, decreasing nutrition avalibility and yields decreading. Many studies and practices have demonstrated that reasonable soil rotational tillage systems, matching with different crop rotation cropping systems, played an important role not only in keeping the sustainable development of farmland ecosystem, but also in creating suitable environment condition(soil, nutrients, water, air, temperature)for crop growth.In order to research the effects of different rotational tillage systems on soil production ability, physical and chemical property of soil and physiology and biochemistry character of crops were investigated in wheat-maize fields on the Weibei dryland. This research will provide some advices for famers to establish a reasonable soil tillage system under a certain fertilizing patterns in the semi-humid and prone-to-drought Loess Platform. A five-year field experiment was carried out from 2007 to 2012 in Ganjing Town, Shaanxi province. Six rotational tillage systems included in this experiment: N/S(no-tillage/sub-soiling rotation), S/P(sub-soiling/ploughing rotation), P/N(ploughing/no-tillage rotation), N/P/S(no-tillage/ploughing/sub-soiling rotation), N/N/S(no-tillage/no-tillage/sub-soilingrotation), P/P/S(ploughing/ploughing/sub-soilingrotation). The continuous no-tillage(CN), continuous sub-soiling(CS) and continuous ploughing(CP) were used as control checks. Results of this paper was as followed. 1. Effects of rotational tillage on soil physical properties in wheat-maize rotation fieldS/P was the best to improve soil structure among all 6 rotational tillage systems. Compared with CN, CS and CP, S/P reduced the soil bulk density(1.2%~9.2%), increase soil porosity(0.3%~6.8%) and field water capacity(5.5%~14.2%). In 0~40 cm soil, the mechanical aggregate of >0.25 mm size of S /P was the highest(0.8%~6.6%). and got the higher, Compared with CN and CP, water-stable aggregates of >0.25 mm size of N/N/S increased 7.1% and 3.9%; this value of S/P also increased 47.6% and 43.2%(P<0.05). 2. Effects of rotational tillage on soil nutrients in wheat-maize rotation fieldConsidering the nutrient condition of soil, the balance fertilization was the highest among 3 fertilizer levels, traditional fertilization was the second and low fertilization was the lowest. Balance fertilization increased the organic matters content(2.9%), total nitrogen content(2.3%), total phosphorus content(2.9%), total potassium content(18.2%), available nitrogen content(3.0%), available phosphorus content(7.3%) and availale potassium content(), compared with traditional fertilization. Traditional fertilization also increased 2.1%?1.1%?3.0%?-9.8%?2.1%?2.1% and-3.8%, respectively, compared with low fertilization. Soil nutrients content in top soil was higher that in deep soil after crop was harvested. Soil nutrients content in 0~20 cm soil was higher 15.1%~158.4% than that in 20~40 cm soil, it was also higher 6.4%~55.1% in 20~40 cm soil, compared with that in 40~60 cm soil. Comparing with other ploughing methods, No-tillage and sub-soiling increased the soil organic matter, total nitrogen, total phosphorus and total potassium content in 0~60 cm soil, ploughing increased the available nutrient content; S/P got the highest value of soil nutrients, followed by N/S and N/P/S was the third. 3. Effects of rotational tillage on soil water conditions in wheat-maize rotation fieldAmong all the rotational tillage systems, N/S got the highest value of soil water storage and soil water storage rate in 0~200 cm soil, S/P and N/P/S followed by sequence, during the summer fallow period. Soil water condition of different rotationan tillage sytems was significantly different in five years, due to the different tillage practices of this year or previous year. Sub-soiling got the best capacity on keeping water, followed by no-tillage, ploughing was the lowest. The soil water storage of sub-soiling and no-tillage were 36.6 mm and13.6 mm higher, respectively, than that of phoughing. At the end of fallow period, S/P(102.7 mm and 24.9%) was the highest, P/N(102.3 mm and 24.8%), N/P/S(93.2 mm and 22.2%) was also the lowest. Comparing with that of other tillage rotation systems, soil water condition of N/S and N/N/S was better; capacity of No-tillage was the best to keep soil water, followed by sub-soiling, loughing was the lowest; soil water storage of sub-soiling and no-tillage was higher than that of phoughing during the whole fallow period. Soil water storage of N/S and N/N/S in 0~200 cm soil were higher(7.9% and 6.4%) than that of CP; soil water of no-tillage was the highest, followed by sub-soiling anad ploughing, during winter wheat growth period. Soil water storage of N/S and N/N/S in 0~200 cm soil were higher(10.7% and10.8%) than that of CP; Soil water of no-tillage was the highest, sub-soiling was the second, no-tillage was the lowest in 2009, during spring maize growth period. Soil water decreased from sub-soiling and no-tillage to ploughing by sequence in 2011, but no significant difference was found betweenno-tillage and sub-soiling.4. Effects of different fertilization and rotational tillage on crop agronomicand photosyntheticcharacters in wheat-maize rotation fieldDuring the 5 years of experiment in the different fertilization patterns, crop agronomic and photosynthetic characters showed as balance fertilization>traditional fertilization>low fertilization. 6 rotational tillage systems in different growth period of winter wheat and spring maize, the average crop height, leaf area index, fresh weightand dry weightof N/S and S/P were increased by 1.4%~8.1%, 5.7%~25.0%(P<0.05) and 6.2%~20.6%(P<0.05), than that of control group(CN, CS and CP). 5 years average, the crop height of S/P under balance fertilization was the highest, crop leaf area index and single biomass of N/S under balance fertilization were the largest. In different combinations of fertilization and tillage patterns, the crop chlorophyll content and photosyntheticcapacity of S/P under balance fertilization were the highest, increased by 2.2%~33.3% and 2.4%~23.0%, respectively, than other combinations, followed by N/S under balance fertilization. It can be seen from theanalysis of photosynthetic characters in winter wheat and spring maize different growth period that the photosynthetic rate of S/P and N/S in 3 years winter wheat and 2 years spring maize were the highest, significantly higher than the control group. In the different treatment combinations, the photosynthetic capacity of S/P under balance fertilization was the best, followed by N/S under balance fertilization; the third was CS under balance fertilization.5. Effects of different fertilization and rotational tillage on crop yield, utilization efficiency of solar energy of gain yield,WUE and economic benefits in wheat-maize rotation fieldCalculated from crop yield, yield components, grain yield, WUE and economic benefits, balance fertilization was the highest, followed by traditional fertilization, the lowest was low fertilization, for both winter wheat and spring maize. During winter wheat production years(3 years), considering from effective ears, kernel numbers and 1000-kernel weight, S/P under balance fertilization was the highest, its effective ears increased 11.0%~53.0% than other combinations of fertilization and tillage patterns. During spring maize production years(2 years), calculated from effective ears, kernel numbers and 1000-kernel weight, N/S under balance fertilization was the highest, its effective ears increased 1.1%~9.2% than other combinations of fertilization and tillage patterns. Considering grain yield, utilization efficiency of solar energy, WUE and economic benefits, S/P under balance fertilization was the highest, followed by N/S under balance fertilization; Correlative values of S/P under balance fertilization increased 7.4%~48.8%(P<0.05), 7.7%~50.0%(P<0.05), 4.6%~41.9% and 11.6%~58.4%(P<0.05), respectively, comparing with other combinations of fertilization and tillage patterns. Crop yield, yield components, grain yield utilization efficiency of solar energy, WUE and economic benefits of different tillage patterns under 3 fertilization patterns had different in the 5 experimental years due to the different tillage practices of the year or previous year. Sub-soiling treatment was the best, followed by no-tillage, ploughingwas the lowest.In conclusion, appropriate rotational tillage systems are beneficial for protecting soil environment, improving soil structure, retaining soil water, increasing crop yield and economic benefits. Sub-soiling/ploughing rotation system(S/P) had good production performance in reducing soil bulk density, improving soil structure, increasing soil water storages and soil nutrients contents, promoting crop yields, utilization efficiency of solar energy and WUE, which is more suitable soil rotational tillage system in winter wheat and spring maize rotation fields for Weibei dryland or similar areas. No-tillage/sub-soiling rotation system(N/S) could increase rainwater infiltration, protect soil, and enhance water reserving and soil moisture keeping, its crop yields and economic benefits were only inferior to S/P. Therefore, N/S was also a good soil rotational tillage system in this region. Considering the local conditions, S/P could be recommended as suitable soil tillage patterns to match the “one crop one year” crop rotation system, followed by N/S. These two systems can be employed to achieve better production performance on the basis of the specific situation. |
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