| Soil rotational tillage systems which composed of no-tillage (N), subsoiling (S) andconventional tillage (C) is the effective measures to solve the drawbacks caused by long-termcontinuous single-tillage mode in dryland. But there are few studies about conservationrotational tillage mode recently, hence it is necessary to conduct the long-period experimentof rotational tillage, in order to clarify the effects of rotational tillage on soil moisture andcrop yield in rainfed farmland. The experiments of N/S (no-tillage in the first year, subsoilingin the second year, again no-tillage followed by alternating the next year), S/C (subsoiling inthe first year, conventional tillage in the second year, again subsoiling followed by alternatingthe next year) and C/N (conventional tillage in the first year, no-tillage in the second year,again conventional tillage followed by alternating the next year) rotational tillage wereconducted in rainfed wheat fields of Weibei highland in summer fallow period from2007to2012, compared with continuous conventional tillage, continuous subsoiling and continuousno-tillage treatments. Soil physical structure and stability, soil moisture conditions in leisureand growth period, soil nutrients, also wheat agronomic traits and yield response were studied.The main results are as follows:1. Effects of different rotational tillage patterns on soil bulk density, soil porosity andaggregate stabilityCompared with pretreatment, soil bulk density and porosity of N/S, S/C and C/Nrotational tillage treatments in harvest period had no significant differences. Soil aggregatesproperties changed significantly under three different rotational tillage treatments, N/S washigher in the macro-aggregate content (R0.25) and stability rate of water-stable aggregatesthan S/C and C/N treatments at0-10cm; N/S was also higher in MWD（mean weight diameter）of water-stable aggregates than S/C and C/N treatments at0-30cm. The fractaldimension of aggregates among these treatments were significantly different at10-30cm bydry sieving and at0-10cm by wet sieving, its value under N/S was lower than S/C and C/Ntreatments.2. Effects of different rotational tillage patterns on soil moisture characteristicsEffects of water storage efficiency in summer fallow period and dynamics of soilmoisture in growing period under different tillage patterns were affected by type ofprecipitation. In drought or normal precipitation years, water storage efficiency of N/Streatment is higher; in rainy years, water storage efficiency of C/N treatment is higher. Indrought growing period of winter wheat in2010-2011, soil water storage in0-200cm layerunder three rotational tillage treatments had no significant differences with conventionaltillage, and soil moisture of N/S treatments was better than S/C and C/N treatments;Rotational tillage also reduced the soil water consumption in growing period thanconventional tillage. In rainy growing period of winter wheat in2011-2012, it had nosignificant differences among three different rotational tillage treatments; N/S and C/Ntreatments increased the soil water consumption in growing period compared withconventional tillage.3. Effects of different rotational tillage patterns on soil fertilityCompared with conventional tillage, N/S treatments significantly increased soil organicmatter, total nitrogen and available nitrogen content at0-20cm; however, total and availablephosphorus, potassium content under rotational tillage treatments had no significantdifferences with conventional tillage.4. Effects of different rotational tillage patterns on wheat agronomic traitsIn drought years, soil moisture under N/S treatments was better, so its leaf area, plantheight, photosynthetic characteristics, dry matter accumulation et al. were better than S/C andC/N treatments. In rainy years, wheat agronomic traits under C/N treatments were overall thebest.5. Effects of different rotational tillage patterns on wheat yield and water use efficiencyIn drought or normal precipitation years, the wheat yield and water use efficiency of N/Sand S/C treatments was higher than C/N; in rainy years, the wheat yield and water useefficiency of C/N treatments was higher than N/S and S/C. The comparison of multi-yearaverage results of yield and water use efficiency among different tillage pattern, it shows thatN/S and S/C rotational tillage pattern is better than C/N.6. Effects of different rotational tillage patterns on economic benefits of wheat productionCompared with conventional tillage, N/S and C/N treatments reduced tillage mechanical inputs, and N/S treatments did not reduce the yield in rainy years and increased the yield indrought years, so it improved economic benefit.In conclusion, N/S conservation rotational tillage pattern increased soil macro-aggregatecontent and stability, improved dryland soil structure; S/C and C/N rotational tillage patternsdisturbed soil layer because of every other year plowing, so its soil structure had nosignificant improvement. Water storage efficiency in summer fallow period and dynamics ofsoil moisture in growing period under different tillage patterns were affected by type ofprecipitation. In drought years, water moisture condition of N/S treatment was better; in rainyyears, water storage efficiency of C/N treatment was better. N/S treatments significantlyincreased soil organic matter and nitrogen content on soil surface. N/S treatments did notreduce the yield in rainy years and increased the yield in drought years, so it improvedeconomic benefits of wheat production compared with conventional tillage. Therefore, Weibeidryland where winter wheat production was in the perennial drought stress, compared withconventional tillage, N/S rotational tillage increased soil water storage in the summer fallowperiod, improved the soil moisture conditions in growing period, improved top soil fertility,and was conducive to ensure stable yield, and also improved the economic benefits. |
