Effect Of Straw Returning In Different Tillage On Direct Seeding Paddy Ecosystem

Straw is the extreme resource in nature.As a big agricultural country,our country's straw output amount to several million ton.At present there was low use efficiency in straw resource and that caused huge waste and environment pollution.This experiment,which was conducted in Nanjing and Nantong from 2006 to 2007,by adopting field experiment,did research on the paddy soil physical-chemical properties and the yield under straws and tillage,and,by adopting potted simulating experiment,did research on the influence of straws and tillage on nitrogen and phosphorus dynamic.The purposes of this research were to supply the scientific basis for the sustainable development of the crops high yield,high efficiency and safety and provide the theoretical references to the protection of the rural ecological environment.The results were as follows:1 Effect of straw returning in different tillage on physical-chemical propertiesStraw returning significantly decreased the bulk density and soil tillage significantly influenced the vertical diversity of soil physical properties.The deep the tillage was,the more remarkable the effect was.Straw returning increased the soil organic matter,total nitrogen content and available phosphorus content.Soil tillage influenced physical and chemical property by the distributions of straw.No-tillage caused nutrient enrichment on the soil surface-layer,while deep plowing urged different layers approaching average level. The treatment of rotary tillage,which was benefit to the enrichment of nutrition,promoted the utilization of straw.2 Effect of straw and no/deep tillage on dynamic of N in surface water of paddy soilA pot experiment with different depth of straw amended was conducted to elucidate the dynamic characteristics of the N in field surface water.The results of the pot experiment showed that urea application sharply increased the concentrations of ammonia nitrogen(NH₄⁺-N) and total nitrogen(TN) in field surface water and both subsequently declined as the time followed.The concentration of TN and NH₄⁺-N in surface water reached its peak at the 1st and 2nd day,respectively,and decreased rapidly then.Surface water NO₃^- -N concentration was very low,though it showed a little raise at the 3rd day after applying urea.The treatment with straw amending decreased the concentrations of nitrogen in field surface water,while deep plowing boosted the absorption of nitrogen for paddy field soil.Contrast to no-straw field,the concentrations of total nitrogen(TN) and ammonia nitrogen(NH₄⁺ -N) in field surface water was decreased by 71.14mg·ml^-1,12.80 mg·ml^-1 at the peak,.The key environmental monitoring index should be focused on total nitrogen(TN) and ammonia nitrogen(NH₄⁺ -N) in 0-4 days after N applying.The period within a week after N application was defined as the key time to control massive N loss from flooded paddy field.To control N non-point pollution from paddy field,further research must be focused on the best N and straw management for native rice production in field experiment.3 Effect of straw returning in different tillage on biotic communityWeed Control Effects of straw returning was significantly.The population of weeds of straw returning was less than the treatment of no-straw returning by 228plant/m².Dry matter accumulation decreased 86.80g/m².The result showed that with the control effect, no matter stem control effect or dry matter accumulation control effect was significantly with the straw returning.On the other hand,straw returning made the brown planthopper, rice sheath blight increasing,but the difference is inconspicuousness.4 Effect of straw returning in different tillage on growth and yield formation of direct seeding paddyStraw returning was bad to rice seedling.Straw retuning rice seedling reduced 25.66% than no-straw returning treatment.Deep plowing &straw returning treatment(DTS) was beneficial to improve the rice seedling emergence rate than other treatment.The increasing of seeding rate could decrease the effect of straw returning in different tillage on seedling emergence rate.The simulation experiment of different moisture control showed that sufficient water could improve the rice seedling rate.The field investment showed that the black root number was the most in the heading stage.The deeper the straw returning was, the less the black root number was.At last,effect of straw returning in different tillage on yield was not significant.However,the sustained development ability of field improved.