Study On Soil Organic Carbon And Nitrogen Components Under Conservation Tillage On Dryland In Hilly Areasof Southwest China

The experiment was conducted to analyze the influence of conservation tillage to soil organic carbon and nitrogen components on sloping dryland planted with broad bean and maize in purple hilly areas in southwest China. There were six treatments including traditional tillage (T), ridge tillage (R), traditional tillage with half amount of straw mulching (TS1), ridge tillage with half amount of straw mulching (RS1), traditional tillage with full amount of straw mulching (TS2), ridge tillage with full amount of straw mulching (RS2).The main findings were as follows:l.The components of soil organic carbon& nitrogenin the soil layer were 0-10cm>10-20cm, including the total organic carbon (TOC), total nitrogen (TN), active organic carbon(AOC), Particulate Organic Carbon(POC),dissolved nitrogen(DN), hot waterdissolved organic carbon(HWC), microbial biomass carbon(MBC) and microbial biomass nitrogen (MBN). Howeverthe dissolved organiccarbon(DOC) showed as0-10cm>10-20cm in maize farmland,but nosignificant regularity in the broad bean farmland.2. As the time changing,the components of soil organic carbon&nitrogen showed different regularity. TOC and TN changed a little during the growth period for the soil organic matter changed slowly. AOC,POC,DOC, DN, HWC,HWN, MBC and MBN showed different changes between the growth period of broad bean and maize.Different season and absoption of nutrients were also the factors.3.The components of soil organic carbon& nitrogenshowed the responses to ridge tillage and straw mulching. Straw mulching improved the content ofthe components of soil organic carbon & nitrogen,but without significant different in DOC among the straw mulching treaments and treaments withoutstraw mulching. Except for MBC&MBN, there were no significant between full amount of straw mulching treatment andhalf amount ofstraw mulching. The components of soil organic carbon& nitrogen showed diffenent reponse to the ridge for the different soil layers,different growth period and different amount of straw mulching.Ridge without straw mulching improved the content of TOC,but decreased the content of TN.Under the ridge tillage treaments,the content ofHWC, HWN were higher than the traditional tillage.4.TOC&TN, DOC&DN, MBC&MBN indicated that there were a certain coupling relationship between soil organic carbon and nitrogen component. TOC&AOC presented a highly significant positive correlation,dependent on soil organic carbon content, so TOC could be an important indicator of soil organic matter.During thedifferent growth period of the plants, the same indicator showed different reponse because of the comprehensive factors such as the temperature, moisture, soil structure and so on.