| Taking the conventional cropping pattern wheat-paddy rice (WRR) as control, the other four treatments, containing Winter cabbage-Zizania (WZR); Winter cabbage-Edamame-Chufa (WECR); Cress-Celery bud-Rice (CCRR); Lotus root-lotus root (LR) were involved in this experiment. Under 5 different cropping patterns, the experiment was conducted to study the rice paddy ecosystem changes of the soil physical and chemical properties, the carbon fixation in soil-crop system, the greenhouse gas emissions, the nutrient fixation situation in soil-crops system as well as the economic, ecological and social benefits. The research draws the following conclusions:1 Effects of the physical and chemical properties of soil from different cropping patternsUnder the conventional massive field cropping patterns, WRR, WZR, WECR and CCRR patterns could make the soil pH value rise, but the bulk density decrease. LRR pattern have an opposite effect. The higher the multiple cropping index was, the more remarkable the pH value and bulk density changed. Based on observing the dynamic change of available nutrients in soil within one year, the available N, the available P, and the available K in the tested soil showed a trend of decline. It indicated the experimental soil became barren. Under the different cropping patterns, the soil nitrification was promoted, indicating WRR, CCRR, LR have higher potential nitrogen losses. The mineralization speed of the WECR pattern was negative, and the rest showed the soil was under mineralization to provide the massive nutrient for the crops.2 Effects of different cropping patterns on the carbon fixationThere were significant differences in different crops on carbon uptake. A significant positive correlation with dry matter accumulation was showed. The unit area nitrogen fixation of different corps in descending order were:Paddy rice> water chestnut> lotus root> wheat> edamame> wild rice stem> Huang Xinwu> Cress> celery bud. The organic carbon content of soil under 5 kinds of cropping patterns all showed an increasing trend, in increasing order:LR> WECR> WRR> WZR> CCRR, on the top layer section, soil’s organic carbon content presented a vertical degression characteristic along with the depth increase. the soil carbon sequestration under models of WECR、WRR、LR、WZR、CCRR are respectively 2461.89、2165.45、778.34、600.93、259.52 kg·hm-2 in agricultural systems. Water chestnut, rice and wheat crops were higher Carbon sequestration crops. Under the WZR and CCRR patterns, the soil was frequently disturbed, thus promoted the soil respiration, increased CO2 emissions, which resulted in lower carbon sequestration.3 Effects of different planting patterns on paddy greenhouse gas emissionsUnder different cropping patterns paddy, Greenhouse gas emissions is different. CO2, CH4 and N2O emissions of controlled WRR were higher, which contributed the most to the greenhouse effect. The CO2 emissions contributed to the greenhouse under different cropping patterns sequenced:WECR> WRR> CCRR> LR> WZR. The biggest contribution of Global Warming potential was CCRR, reaching 20465.73 kg CO2·hm-2, followed by WRR, reaching 20438.27 kg CO2·hm-2,then WECR>LR> WZR. Analysis showed that multiple cropping index had a greater impact on CO2 and N2O emissions, soil dry-wet alternate influence on CH4 emissions. Besides, the temperature influence made the greenhouse gas emissions have an obvious seasonal characteristic, the CO2 emissions presented:summer> autumn> spring> winter; CH4 and the N2O emissions is summer> autumn.4 Effects of the soil-crops system’s nutrient fixation under different cropping patternsDifferent crops absorb different amounts of the nitrogen, phosphorus and potassium element, by the zizania, edamame, lotus root absorb bigger amount of nitrogen, phosphorus and potassium.Under the different crop rotation pattern, soil-crop system for nutrient fixation larger rotation model had WECR, CCRR, WZR, are (N、P、K:808.46、 123.62、233.32 kg·hm-2)、(N、P、K:266.84、107.97、88.57kg·hm-2)、(N、P、K: 455.34、128.60、490.10 kg·hm-2. Three kind of patterns by the crops to the nutrient absorption increased nutrient fixation in soil-crops system. The greater the multiple cropping index, soil-crop nutrients nutrient fixation was bigger. From the point of view of raising the land, WECR, CCRR performanced better the pattern, increasing accumulation of soil nutrients. Nitrogen plots under different cropping patterns showed significant surplus, while potassium deficiency is manifested in negative state, the part of cropping patterns have a negative phosphorus losses. In the process of farmland fertilization, it was to pay attention to NPK application, further to adjust fertilizer management and take suitable amount of nitrogen reduction, stable phosphate dosage, increase potassium application. Finally it could to get both saving and high yield of new planting patterns.5 Under five different cropping patterns, the economical, the ecological, the social benefits comparisonAccording to the local agricultural market average price, and the actual labor costs for the economic benefits, it was analyzed under different cropping patterns. The results showed that whether the total output value or pure benefits were expressed as CCRR>WECR>LR>WZR>WRR.CCRR, WECR, LR and WZR, WRR pure benefit were 150754.23,110259.11,67310.42,42400.14, and 18596.30 yuan·hm-2·2-1.labor cost and benefit in CCRR mode is the largest, followed by LR model, then the WRR>WECR>WZR.WRR pattern as control, new net benefits and a marginal cost return on 1.5 or 22% or higher as promoting meaningful economic benefits evaluation index. Compared with contrast WRR mode, four kinds of mode of new net benefits and marginal costs return rate than the critical value, in line with the promotion.New pure yield performance was:the CCRR>WECR>LR>WZR. Comprehensive analysis WZR mode in the marginal cost of return and net yield new model compared to the rest of the poor performance, and the lowest labor costs, not promotion.Taking economic, ecological, and social benefits into consideration, WECR, CCRR models not only contributed more economic, ecological, social benefits, but also played a better role in raising land, improving soil physical and chemical properties,and reducing greenhouse gas emissions. The models significantly increased net income, improved income from labor cost, and increased net benefits, with a high economic and social value, which were more suitable for the region along the Yangtze River in Anhui planting patterns. |
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