| According to some problems such as exposed surface, serious soil loss and soil quality degradation in dry farming area on Loess Plateau of Inner Mongolia, through eight years’field experiment of five tillage treatments including no-tillage with high stubble mulching(NHS), no-tillage with low stubble mulching(NLS), no-tillage with high stubble(NH), no-tillage with low stubble and conventional tillage(T) under three rotations (oat-soybean-corn,soybean-corn-oat and corn-oat-soybean) and using the research methods of qualitative and quantitative, theory and demonstration, a system analysis of the seasonal, annual and spatial variation regulation of soil physical, chemical and biological quality under two no-tillage rotation cycles were done. And the evolution characteristics, driving factors and effect mechanisms of soil quality under long-term no-tillage rotation were described. The soil quality representative indexes of soil physical, fetility, health and land productivity which were suitable to the eroxion environment in dry farming area of Loess Plateau were selected, combined with regional characters and previous researchs, the suitable soil quality evaluation index system and model were builded. At the same time, using soil quality comprehensive index methods to evaluate soil quality completely. And also the suitable no-tillage rotation pattern and planting technology system were determined. The research results were as follows:No-tillage with stubble mulching can improve soil ecological benefit. The soil erosion intensity had close relationship with land surface roughness, and with the increasing of soil surface covers, the water erosion is obviously weakened. The results showed that, rainfall, rainfall intensity and slope gradient had obvious effects on soil water erosion and water erosion amounts. In2006, the annual total surface runoff amounts of NHS, NLS, NH, NL and T under7°4’ slope gradient increased by14.14%,14.36%,16.89%,18.18%and19.70%than that under4°6’ slope gradient, the annual total soil loss amouts increased by17.34%,17.55%,19.00%,20.55%and20.63%. So using some measures such as no-tillage with stubble mulching can increase vegetation coverage and land surface roughness, decrease surface runoff and soil loss.Many years’no-tillage with rotation can improve soil physical quality. No-tillage can avoid the disturbance on soil, and combined with stubble mulching and rotation had a more important effects on improving soil structure and increasing the ability of storing and conserving moisture in soils. The oat-soybean-corn with stubble mulching had the biggest effects on improving soil physical quality. No-tillage with rotation increased soil aggregate and soil porosity, improved soil infiltration. And after one rotation cycle, soil porosity of no-tillage in0-20cm soil layer increased9.96%-17.72%than that of T, soil aggregate increased18.4%-89.9%, soil stale infiltration increased10.85%-14.18%. Through the improvement of soil structure, no-tillage with rotation improve soil water storage characteristics. After one rotation cycle, the soil water storage in0-20cm of no-tillage treatments increased most, and compared with T, the soil water content of NHS, NLS, NH, NL increased12.00mm,11.87mm,11.03mm,8.38mm in the seeding stage. Take NHS as example, soil water content of2008increased14.03mm and28.30mm than that of2006and2007. No-tillage with rotation improved soil temperature environment, and when the temperature was high, no-tillage with stubble mulching had the cooling effect, it showed in middle growth period that the soil temperature decreased3.2-5.3℃,2.7-4.6℃and1.4-3.5℃than T in5cm,20cm,40cm soil layers, but when the temperature was low, no-tillage with stubble mulching had the insulation effect, it showed no-tillage with stubble mulching can increase soil temperature by2-3℃. In the second rotation cycle drought was serious, the improving effects of soil structure were weakened and the differences among treatments were not obvious. But the oat-soybean-corn with stubble mulching had the better effects.So carring out no-tillage with rotation for many years can benefit to forming good soil structure, improve soil hydrothermal condition and its permeability, increase soil water storage and water use efficiency, promote the improving of soil physical quality.Many years’no-tillage with rotation increased soil chemical quality.Through improving of soil physical environment, no-tillage with rotation had effects on a series of chemical change processes such as soil nutrient transformation, and than increased soil nutrients content. Through no-tillage with rotation for many years, the results showed that, among different no-tillage treatments no-tillage with stubble mulching had the most obvious effects, especially the soil nutrient in0-20cm soil layers. The three rotations had different effects on improving soil nutrient content. Under three rotations combined with no-tillage with stubble mulching, the soil organic matter content in arable layer increased11.79%-15.73%after one rotation cycle,14.68%-16.50%after two rotation cycles; the available N, P, K in arable layer increased13.74%-16.97%,12.50%-15.63%,11.40%-19.20%after one rotation cycle,17.90%-24.08%,20.07%-25.78%,15.22%-27.59%after two rotation cycles; the total N, P, K in arable layer increased8.57%-13.92%,7.41%-16.13%,1.87%-2.87%after one rotaton cycle,12.82%-20.25%,10.34%-22.58%,3.25%-5.13%after two rotation cycles; the pH value decreased 9.76%-11.53%after one rotation cycle,4.54%-11.25%after two rotation cycles. So in the rain-fed farming system of Loess Plateau in Inner Mongolia,when the combined application of N, P fertilizer was used, using no-tillage with stubble mulching and crop rotation had important effects on promoting and maintaining soil nutrient balance and increasing soil chemical quality.Many years’no-tillage with rotation increased soil biological quality. Results showed, no-tillage with stubble mulching combined with rotation for many years increased soil enzyme activities and soil microbial biomass C, N, P contents. Among different no-tillage rotations, the soil biological idexes activity most showed oat-soybean-corn combined with no-tillage with stubble mulching was best. And with the increasing of the straw decomposition, soil biological activity showed a increased trend. In the first rotation cycle, the soil hydro thermal environment of no-tillage with stubble mulching was better, and the biological activities were higher, showed a increased trend with the increasing of years and it reached the biggest at2008. Under three rotations combined with no-tillage treatments, the soil catalase, invertase, urease and alkaline phosphatase activities increased6.57%-13.04%,8.02%-14.00%,21.84%-35.79%,2.92%-4.19%; soil microbial biomass C, N, P contents increased20.20%-37.63%,10.49%-19.03%,6.40%-16.55%after one rotation cycle.In the second rotation cycle, drougt was serious and the rainfall of2009is less than150mm during the whole growth period, this leading to the decrease of soil biologic activity, soil enzyme activity and soil microbial biomass content.And compared with the first year, under three rotations combined with no-tillage treatments, the soil catalase, invertase, urease and alkaline phosphatase activities increased5.47%-9.42%,5.02%-11.72%,9.20%-28.42%,0.71%-2.21%; soil microbial biomass C, N, P contents increased8.35%-29.90%,3.69%-13.62%,3.06%-14.20%.Many years’no-tillage with rotatin improved soil comprehensive quality. Through making the soil quality indexes being dimensionless and the calculation of weights, the evaluation indexes’index and soil comprehensive quality indexes were determined, the soil quality evaluation index system and routing model were builded. The results showed that, soil biological quality indexes and soil physical quality index were both high under many years’no-tillage with rotation, and it had biggest effects on soil comprehensive quality. The soil physical, chemical, biological and comprehensive quality index among different no-tillage treatments showed NHS>NLS>NH>NL>T. Among three rotation patterns, the differences of soil quality index were not obvious, and oat-soybean-corn showed better than the other two rotations. Trough the analysis effects of no-tillage, rotations and the combined effects of the two, tillage methods and combined effects had big effects on soil physical, chemical and biological quality, they all reached significant(p<0.05) or very significant(p<0.01) level, but the effects of rotation pattern were smaller than the former.Many years’no-tillage with rotation improved land productivity. The results showed, through improving soil quality, no-tillage with rotation for many years increased crop yield, value to cost ratio of farmland and economic benefit.In dryfarming area the crop yield had the same change trend with rainfall. And three rotations combined with no-tillage had different effects to improve crop yield, oat-soybean-corn had the biggest effects. Under three rotations combined with no-tillage, the crop yield and economic benefit increased10.01%-27.69%,20.21%-38.57%in the first rotation cycle, increased10.55%-24.74%,31.41%-51.89%in the second rotation cycle. So in the dryfarming area of Loess Plateau in Inner Mongolia, carring out no-tillage with rotaion for many years can reach the increasing of crop yield and income, and than increasing farm land productivity of this region, realizing agricultural sustainable development. |
PDF Full Text Request