Study On Synthetical Effects And Models Of Conversation Tillage In The Region Of Tri-crop Intercropping System

Since the 1960s when conservation tillage technology came into our country, scientists have carried out a number of studies. However, researches and demonstration are mostly conducted in arid and semi-arid areas of northern China and the study usually focus on one crop a year or two crops a year system, and tillage treatment is single. There is little study on conservation tillage models of three crops a year system in southwest China and the law of soil nutrients, agricultural ecology, water distribution, crop growth and development, and water use efficiency under the condition of conservation tillage is also lacking. Given this situation, this study was implemented in experimental farmland of Southwest University, Beibei District, in Chongqing City, from November 2007 to November 2009. Taking dry field under "wheat/corn/sweet potato" and the "Potato/corn/sweet potato" tri-crop intercropping system as a study object, the experiments were conducted to investigate soil nutrient, farm ecology and soil moisture and crop response to conservation tillage. Using local meteorological and experimental data, and the statistical software SPSS and DPS to compare different tillage patterns, it may provide the scientific basis for promotion of conservation tillage in this area. The major findings are as follows:1. In soil nutrient's aspect, the five modes of conservation tillage all improved soil nutrient supply. Compared to T, the improvement rate of the SOM of RSD, TSD, RS, TD models were respectively by 28.27%,21.30%,16.54%,19.16%, decreasing the rate of bulk density by 3.33%,3.00%,4.00%,2.67%, significantly increased the content of total potassium, total nitrogen, nitrogen in the soil. While the other indexes of R were not significantly different from those of tradition, except the SOM. Dynamic changes of soil nutrients are more complex than a single straw mulch treatment because each of tillage models includes some different tillage methods.2. In the aspect of field's ecological environment, straw mulching treatments like RSD, TSD, RS, and TS were higher than no straw mulching treatments CK and R in terms of the number of earthworms or biomass. But in all, the effects of RS and TS were better. At the same time, RSD, TSD, RS, TS model significantly reduced soil temperature in the 5cm and 10cm at 14:00 hours in July enhance easing the high-temperature damage on maize in late growth stages. However, compared to traditional tillage, R's effect was not remarkable. In the weed control aspect, straw mulching treatments had more efficient than straw mulching treatments in terms of weed height, density, or biomass, while the ridge's effect was not remarkable. The order of control results from the high to lower is as follow:RS> TS> TSD> RSD> T (CK)> R.3. In the aspect of soil moisture, two consecutive years of field trials showed that each treatment increases the soil water storage in 0～80cm soil layer. The order of soil water storage from the high to lower is as follows:RSD>RS>TSD>TS>R> T(CK). In the aspect of the vertical dynamic change of soil moisture,0～40cm of soil water content changed dramatically between 21.45%～30.78%, amplitude in 40～60cm soil layer is relatively small,60～80cm soil layer is relatively stable. This indicates that conservation tillage will help improve soil water storage capacity, increase soil reservoir stocks, while its effects on 0～40cm layer of soil moisture is significantly greater than 40～80cm soil layer.4. In the aspect of Growth and physiological characteristics of crops, compared to traditional tillage, conservation tillage significantly increased the area of the flag leaf and penultimate leaf, increased the net photosynthetic rate by 2.90%～5.74% in maturity stage of wheat. The process of maturation (4.17-5.12), the distribution of index rising trends increased by 238.46%～242.31%. Two consecutive years of field trials showed that conversation tillage significantly increased root length in the diameter range of 1.0～2.5 mm, root surface area in the seedling stage of maize, meanwhile increased root vigor by 19.12%～27.46%, root-shoot ratio by 36.72%～37.50%, root biomass by 62.53%～77.37%. This indicates that conservation tillage is not only beneficial to root development, but also promoted the growth of plants, thereby enhancing the leaf net photosynthetic rate and plant distribution index.5. In the aspect of grain yield and water use efficiency, the order of the average grain yield is as follow:RSD> RS> TSD> TS> R> T (CK). Tillage treatments including RSD, RS, and R significantly increased the yield of potato crops. And compared with treatment T, the trend of R, TS, RS, TSD and RSD were decreasing. The order of various water use efficiency and production efficiency of precipitation is as follow:RSD> RS> TSD> TS> R> T (CK).6. In the respect of benefit analysis, compared with treatment T, the output, net income of other treatments were significantly increased, the output by 4.41%～17.40%, net income by 5.36%～15.37%, output ratio by 3.84%～19.21%. The order of benefit analysis is as follow:RS> RSD> R> T (CK)> TSD> TS.From the experimental study, it can be concluded that the five conservation tillage models have good regulation effects on soil nutrient and soil moisture, including the regulation of soil temperature, the control of weed, the promotion of earthworms, and the significant improvement of crop yield, economic benefit and WUE. Integrated effect of RSD, RS are the best, and are worthy of promotion in the region of tri-crop intercropping system in southwest China.